Entrez Genomes [20] provides access to genomic data contributed by the scientific community for over 900 species whose sequencing and mapping is complete or in progress, and now includes more than 57 complete microbial genomes and 245 reference sequences for eukaryotic organelles; a gain of about 27 microbial genomes and 80 organelle sequences over last year.

Four higher eukaryotic genomes are also found within Entrez Genomes; Homo sapiens, Drosophila melanogaster, Caenorhabditis elegans and Arabidopsis thaliana.

A new tool for genomic comparisons has been added within the last year called TaxPlot, which graphically compares similarities in the proteomes of two organisms to that of a third reference organism.

Entrez Genomes reports for complete microbial genomes give access to views showing various aspects of proteome organization, including the taxonomic distribution of proteins encoded in the genome (TaxMaps) and their membership in Clusters of Orthologous Groups (COGs) [16], links to 3D structures and conserved protein domains.

Pairwise sequence alignments for sequence neighbors are presented graphically and linked to the Cn3D macromolecular viewer [21], which allows the interactive display of 3D structures and sequence alignments.


The COGs database [16] presents a compilation of orthologous groups of proteins from completely sequenced organisms representing 30 phylogenetically distant clades.

Many new organisms have been added over the last year, bringing the total to over 44.

The COGs are now also linked to the proteins of two higher eukaryotes; the worm and the fly.


NCBI’s SAGEmap service implements many functions useful in the analysis of SAGE data such as a two-way mapping between SAGE tag and UniGene.

A new Java-Based SAGEmap Submission Tool (SST) is now available to assist SAGEmap submissions, and may be useful as a SAGE data organizational and analysis tool.


NCBI provides web access to the OMIM catalog of human genes and genetic disorders authored and edited by Victor A. McKusick at The Johns Hopkins University [22].

The database contains information on disease phenotypes and genes, including extensive descriptions, gene names, inheritance patterns, map locations and gene polymorphisms.

OMIM currently contains 12,940 entries, including data on 9,526 established gene loci and 926 phenotypic descriptions, and is now searchable using the powerful Entrez interface.


The Gene Expression Omnibus (GEO), a data repository and retrieval system for gene expression data, is described in a separate article in this issue [23].


The NCBI MMDB, built by processing entries from the Protein Data Bank [5], is described by Wang et al. [ 7].

The structures in the MMDB are linked to sequences in Entrez and to the CDD.

The CDD contains PSI-BLAST-derived Position Specific Score Matrices (PSSM’s) representing domains derived principally from two public protein domain collections, the Simple Modular Architecture Research Tool (SMART) [24] and Pfam [25], but also draws from domains defined by NCBI researchers.

NCBI’s Conserved Domain Search (CD-Search) service can be used to search a protein sequence for conserved domains in the CDD.

Wherever possible CDD hits are linked to structures which, coupled with a multiple sequence alignment of representatives of the domain hit, can be viewed with NCBI’s 3D molecular structure viewer, Cn3D [21].

A new Tool, called the Domain Architecture Retrieval Tool (DART), has been added to the MMDB suite which allows searches of protein databases on the basis of a combination of conserved domains.

Protein domain information has also been integrated into the Entrez system as mentioned above.


Most of the resources described here include documentation, other explanatory material and references to collaborators and data sources on the respective web sites.

Several tutorials are also offered under the Education link from NCBI’s home page.

A Site Map provides a comprehensive table of NCBI resources, and the What’s New feature announces new and enhanced resources.

A user support staff is available to answer questions at info@ncbi.nlm.nih.gov.


The GenBank sequence database incorporates publicly available DNA sequences of more than 105,000 different organisms, primarily through direct submission of sequence data from individual laboratories and large-scale sequencing projects.

Most submissions are made using the BankIt (web) or Sequin programs and accession numbers are assigned by GenBank staff upon receipt.

Data exchange with the EMBL Data Library and the DNA Data Bank of Japan helps ensure comprehensive worldwide coverage.

GenBank data is accessible through NCBI’s integrated retrieval system, Entrez, which integrates data from the major DNA and protein sequence databases along with taxonomy, genome, mapping, protein structure and domain information, and the biomedical literature via PubMed.

Sequence similarity searching is provided by the BLAST family of programs.

Complete bimonthly releases and daily updates of the GenBank database are available by FTP.

NCBI also offers a wide range of World Wide Web retrieval and analysis services based on GenBank data.

The GenBank database and related resources are freely accessible via the NCBI home page at http://www.ncbi.nlm.nih.gov.


GenBank is a public database of all known nucleotide and protein sequences with supporting bibliographic and biological annotation, built and distributed by the National Center for Biotechnology Information (NCBI), a division of the National Library of Medicine (NLM), located on the campus of the US National Institutes of Health (NIH) in Bethesda, MD [1].

NCBI builds GenBank primarily from the direct submission of sequence data from authors.

Another major source of data is bulk submission of EST, GSS and other high-throughput data from sequencing centers.

The US Office of Patents and Trademarks (USPTO) also contributes sequence data from issued patents.

The data are supplemented by sequences submitted to other public databases.

Through a long-standing international collaboration with the EMBL Data Library [2] in the UK and the DNA Databank of Japan (DDBJ) [3], data are exchanged daily to ensure that all three sites maintain a comprehensive collection of sequence information.

NCBI makes the data available at no cost over the Internet, by FTP access and by web text and sequence similarity search services.

NCBI also offers a wide range of World Wide Web retrieval and analysis services which operate on the GenBank data [4].


Obstetric anal sphincter injuries (OASIS) are serious complications to vaginal deliveries, with a 50% long-term risk of anal incontinence, that is, involuntary loss of feces or flatus.

1-3 In Norway, a National preven- tion program aiming at reducing the incidence of OASIS was initiated in 2004.

The prevention program was inspired by the management of deliveries in Finland, where the incidence of OASIS at that time was very low.

4 The program consisted of manual protection of the peri- neum, visualization of the perineum during crowning of the fetal head, focus on good communication with the delivering woman and use of episiotomy only on indication (the Norwegian/Finnish model).

5 After a couple of years, the incidence of OASIS in Norway dropped signifi- cantly, from 4%-5% to 1%-2%.

5 In Denmark, the incidence of OASIS in primiparous women in- creased from 6.1% in 2000 to 7.4% in 2010.

6 Unlike the situation in Norway, there has been no decision on a national OASIS-prevention program in Denmark.

However, since 2012, the incidence of OASIS has been monitored and evaluated yearly in a national setting (Danish National Quality Database for Births).

7 Despite no national strategy for OASIS prevention, the overall incidence of OASIS among first-time mothers has decreased in Denmark since the detailed national surveil- lance started in 2012; from 6.2% in 2012 8 to 4.2% in 2017.

7 In 2015, the Danish Society of Obstetrics and Gynecology pub- lished a national guideline 9 on evidence to prevent and thereby reduce the incidence of OASIS.

The recommendation was that all obstetric departments in Denmark should initiate OASIS-preventive strategies.

Before publication of the guideline, two of four obstetric departments in the Capital Region of Denmark had already initiated formal prevention programs.


The prevention programs were inspired by the Norwegian/Finnish model, which is further described in the Material and methods section.


The aim of the present study was to evaluate the effect of pre- ventive initiatives to reduce the incidence of OASIS by comparing hospitals from the same region with and without formal prevention programs and by comparing risk factors over time and at the differ- ent departments.


We performed a historical cohort study, evaluating incidence, change of incidence and risk factors of OASIS during the years 2011-2015 at the four delivery departments in the Capital Region of Denmark.

Two of the departments at Herlev (Hospital 1) and Hillerød (Hospital 2) Hospitals used formal prevention programs to reduce the risk of OASIS, adopting the Norwegian/Finnish model, but Hvidovre Hospital (Hospital 3) and Rigshospitalet (Hospital 4) did not introduce a formal prevention program during the study period.

We used data from the Danish National Birth Registry.


The main outcome of this study was the incidence of OASIS.

Variables included in the analyses to test for association with the in- cidence of OASIS were: year of delivery (calendar year [2011-2015], years after and before intervention [2014 and 2015 vs 2011 and 2012, deliveries in 2013 were excluded in the analyses of the effect of formal prevention programs as education and certification took place during 2013]), hospital (separately and grouped by use of for- mal prevention program [yes/no] [Hospitals 1 and 2 vs Hospitals 3 and 4], maternal age at delivery [years]), maternal prepregnant body mass index (kg/m 2 ) (as continuous variable and categorized as under- weight [<18.5], normal weight [18.5-24.9], overweight [25-29.9] and obese [>30]), maternal smoking (yes/no), primiparity, fetal birthweight (g or kg), fetal head circumference (cm), gestational age (days), fetal presentation (occiput anterior, occiput posterior and breech delivery), 5-minute Apgar score <7, induction of labor, oxytocin stimulation, epidural anesthesia, vacuum extraction, forceps delivery, mediolateral episiotomy, and time of delivery (daytime [08.00-23.59 hours] or night [00.00-07.59 hours]).


At Herlev Hospital (Hospital 1), the formal prevention program started with several meetings for midwives and doctors at the de- livery ward to inform about the diagnosis and prevention of OASIS.

A Norwegian midwife who had worked with the Norwegian pre- vention program, 10 participated for 2 weeks in the clinical work and instructed colleagues at the department, focusing on bedside learn- ing and "hands-on".

Twelve midwives were trained and certified in the Norwegian/Finnish techniques.

Subsequently, these 12 midwives trained the rest of the department's midwives, obstetricians, gynecol- ogists and residents.

Furthermore, the obstetrician who implemented the preventive model in Norway, 4 held a "hands-on" training session where the manual protection technique in vacuum-assisted deliveries was practiced on a phantom.

Each midwife and doctor, regardless of previous training skills and experience, was supervised at a minimum of three deliveries before certification.

After implementation of the formal prevention program was completed, all newly hired midwives and doctors, irrespective of previous training, were obliged to take part in an education session with phantom training, as well as super- vised deliveries before certification.


At Hillerød Hospital (Hospital 2), the prevention program was initiated in 2010 and included courses in correct handling of OASIS (theory, diagnosis and suturing).

From May 2012, hands-on tech- nique courses were held for midwives and obstetricians.

The protec- tive technique was optional and could be according to the "Finnish" technique, 11 Ritgens maneuver 12 or another manual protection technique.

As this prevention program did not seem to reduce the number of OASIS significantly (data not shown), all staff attended a 1-day course introducing the technique used in the Norwegian


During the years with a general focus on how to prevent obstetric anal sphincter injuries, the incidence decreased significantly.

Hospitals with formal prevention programs, however, did not have a higher reduction in incidence than hospitals without programs.

16000412, 2019, 11, Downloaded from https://obgyn.onlinelibrary.wiley.com/doi/10.1111/aogs.13672 by Mcgill University, Wiley Online Library on [18/05/2024].

See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License JANGÖ et Al.

model performing hands-on training on phantoms.

Training was con- ducted by both a Finnish midwife and obstetrician who participated in the Norwegian national preventive program.

Back at the delivery ward, all midwives and obstetricians (irrespective of previous train- ing, skills and experience) were supervised by certified local staff.

Supervision of the midwives included a minimum of three training sessions on a phantom followed by supervision on three deliveries before certification.

The doctors were also supervised in "hands-on" vacuum extraction on a phantom, using the Norwegian model, re- quiring three supervised sessions on a phantom before certification.


Hvidovre Hospital (Hospital 3) and Rigshospitalet (Hospital 4) served as controls, as these hospitals did not have a formal OASIS- prevention program in the time period.

At Hospital 3, OASIS-pre- ventive initiatives started during 2015, focusing on diagnosis, episiotomy technique and voluntary training sessions.

No certifica- tion or bedside training was applied.

Hospital 4 did not have a formal prevention program for OASIS.


Statistical analyses to evaluate changes in incidence of OASIS and risk factors over time were made using trend tests.

To compare groups, we used the Chi-square test, Fisher's exact test and Kruskal- Wallis test as appropriate.

Further, we evaluated risk factors of OASIS using uni- and multivariable analyses.

The multivariable logis- tic regression analyses were performed as stepwise regression with backward elimination of nonsignificant or borderline nonsignificant variables.


Since the incidence of OASIS has previously been found to be influenced by whether episiotomy is performed in deliveries with and without vacuum extraction, 6 we tested for interaction be- tween these factors.

We also tested for interaction between year of delivery (2014 and 2015 vs 2011 and 2012) and for hospital with or without formal prevention programs.

Significance level was set as a P-value <0.01 due to the large number of analyses and therefore risk of multiplicity.


In the final multivariable model, the analyses were adjusted for the following variables: year of delivery, place of birth at department with or without formal prevention program, mater- nal age, smoking during pregnancy, primiparity, fetal birthweight, epidural anesthesia, vacuum extraction and episiotomy.

Forceps, although significantly associated with the risk of OASIS, were not included in the multivariable analyses since forceps are rarely used in Danish obstetric practice.

Statistical analyses were performed using the statistical software R (https ://www.r-proje ct.org/).


We used registry data from the Danish Medical Birth Registry (Permission No. FSEID-00002666, date of approval 19 January 2017).

The study was also approved by the National Data Protection Agency (J.nr.

HGH-2016-035, I-Suite nr. 04489.

Date of approval: 1 March 2016).


There were 93 273 deliveries in the study period.

Of these, 75 173 (80.6%) were vaginal deliveries and 18 100 (19.4%) were by cesarean section.

Among vaginal deliveries, 2670 (3.6%) were complicated by OASIS.

The incidence of OASIS decreased during the study period from 4.3% (n = 636) in 2011 to 2.6% (n = 399) in 2015 (Table 1).


A significant decrease was found for all four hospitals during the study period (Figure 1).

However, comparing the annual incidence of OASIS between the four hospitals, we found that the incidence was equal in years 2011 and 2012, but that there was a significant dif- ference between the hospitals during the years 2013-2015 (Table 1).


During the study period, the cesarean section rate did not change significantly (P = 0.79), nor did the rate of vacuum-assisted deliveries (P = 0.05).

However, we found a significant change in the proportion of primiparous women over the study period.

At the hospitals with formal prevention programs, the proportion of primiparous women increased from 36.6% to 43.1% (P < 0.001) and at hospitals without formal pre- vention programs, the proportion decreased from 57.6% to 54.9% (P < 0.001).


There was a significant increase in the rate of episiotomy in the study period from 3.8% in 2011 to 5.5% in 2015 (P < 0.001) and this increase was significant both at hospitals with formal pre- vention programs (P < 0.001) and those without (P = 0.001).

Further, the episiotomy rate differed at hospitals with and without formal pre- vention programs.

Notably, the rate of episiotomy in vacuum-assisted deliveries increased markedly at hospitals with formal prevention pro- grams, although a similar but smaller increase was found in hospitals without formal prevention programs (Figure 2).


When comparing the hospitals in the years after intervention (2014 and 2015), we found a lower risk of OASIS in spontaneous deliveries without episiotomy at hospitals with formal prevention program (1.5%, n = 158) than at hos- pitals without formal prevention programs (2.0%, n = 331; P = 0.002) (Table 2).

In vacuum-assisted deliveries at hospitals with formal pre- vention programs, the rate of episiotomy increased from 9.8% in 2011 to 27.9% in 2015.

After implementation of the formal prevention pro- grams, the risk of OASIS was 7.7% if episiotomy was performed in vac- uum-assisted deliveries and 10.0% without episiotomy, although this difference was not significant (P = 0.27).

At hospitals without formal prevention programs, the rate of episiotomy in vacuum-assisted deliv- eries increased from 8.9% in 2011 to 17.5% in 2015.

At the time after intervention at the other hospitals, the hospitals without formal pre- vention programs had the same risk of OASIS irrespective of whether episiotomy was used (10.7% vs 10.7%, P = 0.99).


In Table 3, population characteristics according to hospital with and without formal prevention programs at the years after implementation (2014-2015) are presented.

Notably, there was a significantly higher proportion of primiparous women at the two de- partments without formal prevention programs (55.8%) than at the departments with such programs (39.5%; P < 0.001).

We also found F I G U R E 1 Changes in incidence of obstetric anal sphincter injury (OASIS) over time at the four Hospitals in the Capital Region 2011-2015 [Color figure can be viewed at wileyonlinelibrary.com] When analyzing risk factors of OASIS during the study period we found two important interactions.

First, we found that year of delivery (2014 and 2015 vs 2011 and 2012) and whether the de- partment had a formal prevention program affected the risk of OASIS differently (P = 0.008).

Secondly, we found that the risk of OASIS was affected differently in vacuum-assisted deliveries with or without episiotomy (P < 0.001).

Therefore, these two interactions were included in both the univariable and the multivariable analyses (Table 4).

After adjustment and removal of nonsignificant and bor- derline significant/nonsignificant variables (close to P = 0.01), both interactions remained significant.


In the univariable analyses, we found that the risk of OASIS during 2011 and 2012 did not differ significantly between hospitals with and without formal prevention programs (P = 0.15).

When com- paring the risk of OASIS at departments without formal prevention programs in 2011 and 2012, there was a significantly lower risk in 2014 and 2015 for hospitals without formal prevention programs (crude odds ratio 0.67, 95% confidence interval [CI] 0.60-0.75) and an even lower risk at hospitals with formal prevention programs (crude odds ratio 0.48, 95% CI 0.42-0.55).


The final multivariable analyses were adjusted for year of de- livery, formal prevention program, maternal age, smoking status, parity, fetal birthweight, induction of labor, epidural anesthesia, vac- uum extraction and episiotomy.

After multivariable adjustments we found a higher risk of OASIS at the departments with formal preven- tion programs at baseline (years 2011 and 2012) (adjusted odds ratio [aOR] 1.36, 95% CI 1.20-1.54) than departments without formal prevention programs.

Similar to the univariable analyses, we found a reduced risk of OASIS in 2014 and 2015 for both the departments with formal prevention programs (aOR 0.67, 95% CI 0.58-0.78) and those without (aOR 0.68, 95% CI 0.61-0.76).


The risk of OASIS in vacuum-assisted deliveries was higher if performed without episiotomy (aOR 3.08, 95% CI 2.77-3.43) than if it was performed with episiotomy (aOR 2.35, 95% CI 1.89-2.93).

In the multivariable analyses we also found that increasing mater- nal age, primiparity, increasing birthweight and epidural anesthesia increased the risk of OASIS.

Smoking during pregnancy significantly decreased the risk of OASIS, even after adjustment for the other variables, including fetal birthweight.


We performed a historical cohort study with prospective follow up to evaluate the change in incidence of obstetric anal sphincter injury (OASIS) at four delivery departments in the Capital Region of Denmark and found that the overall incidence of OASIS decreased significantly during the period, at both the departments with and those without formal prevention programs.

The adjusted analyses showed a similar risk reduction at departments with and without formal prevention pro- grams when controlling for important risk factors and for calendar year.


The robustness of evidence regarding perineal protection and reduction of OASIS using the Norwegian model have previously been criticized.

22,23 The randomized trials performed to evaluate perineal protection have failed to provide effective reduction in the TA B L E 2 Incidence of obstetric anal sphincter injury (OASIS) in spontaneous and vacuum-assisted deliveries depending on episiotomy and formal prevention program in the years after intervention (2014-2015) (n = 30 835) OASIS rate.

24 The Norwegian/Finnish model includes both perineal protection and other preventive strategies, and therefore it is diffi- cult to differentiate between the specific strategies and how these affect the overall risk of OASIS, separately and combined.

22 Based on our results it seems that some cases of OASIS can be prevented when adopting general focus on prevention strategies.


However, we found no significant extra effect of implementation of a formal training program.

The decreased incidence of OASIS did not reach the magnitude reported from Norway.

In Denmark, prevention strategies depended on local initiatives.

In contrast, the marked reduction of OASIS in Norway was the result of a na- tional strategy with compulsory tutorials in all clinics.

In Norway, TA B L E 4 Risk factors of obstetric anal sphincter injury (OASIS) according to maternal, fetal and obstetric characteristics presented as uni- and multivariable analyses It is possible that this could have caused a more marked effect on obstetrical practice, resulting in a higher reduction of incidence of OASIS, causing a significant difference between the hospitals with and without formal prevention programs.


An intervention program like the Norwegian program is costly.

Further, the preventive effect is not verified by randomized controlled trials.

These may be expla- nations for not implementing intervention programs like the one used in Norway.

It is possible that future rigorous prevention strate- gies will significantly alter the incidence of OASIS.

The results from Norway with a continuously low number of OASIS is admirable, and taking the severe long-term complications to OASIS into consider- ation, continuous focus and prevention is needed to further reduce the number of women with OASIS.


One of the side-effects of the increased focus on reduction in the incidence of OASIS was the increased use of episiotomy.

In Denmark, the episiotomy rate has been decreasing 6 and Blondel et al found that Denmark had the lowest episiotomy rate (3.7%) of the European countries.

25 In the present study, we found that the episiotomy rate increased significantly after implementation of the formal prevention programs and to a lesser extent also at the hospitals without formal prevention programs.

Especially, the rate of episiotomy increased in vacuum-assisted deliveries, possi- bly as a result of recent data that this protects against OASIS in primiparous women.

26 In Norway, education in episiotomy tech- nique was one of the central parts in the prevention of OASIS.

Laine et al found that the rate of episiotomy actually decreased in spontaneous deliveries but increased significantly in instrumental deliveries in primiparous women (from 61% to 85%).

20 Although we found an increased risk of episiotomy rate in vacuum-assisted de- liveries, the episiotomy rate in our study is substantially lower than that in the Norwegian study.

The results of an ongoing Swedish randomized controlled trial that is evaluating the influence of lat- eral episiotomy in vacuum-assisted deliveries among primiparous women are awaited.

27 The important strength of this study is the large sample size over a relatively short time in obstetric settings that are very similar for other matters than preventive strategies for OASIS.

The large data- set allows for multivariable testing to control for important risk fac- tors and possible confounders.

Data were collected for all deliveries and, ideally, bias due to registration as well as recall bias should be eliminated.


However, there are some weaknesses that need to be addressed.

First, the intervention with formal prevention programs was initi- ated and conducted differently at the two hospitals with prevention programs.

The Capital Region of Denmark is geographically small, and many midwives and doctors change work places within the re- gion.

Therefore, it is possible that the exchange of staff between hospitals with and without formal prevention programs might affect the incidence of OASIS during the study period.

Also, the national guideline on prevention of OASIS and the overall focus on the pre- ventive strategies may have had a Hawthorne effect 28 on the staff in hospitals without formalized preventive strategies.

Furthermore, many obstetric and demographic factors that could not be evaluated in our study, could have led to the effect of the formal prevention programs being too small to detect a significant difference.


In this study, we compared the effect of a formal prevention program with general recommendations.

We did not investigate the different prevention strategies separately (ie, perineal protection, communication, reducing speed of crowning and individualized need for episiotomy) but focused on the effect of the awareness on com- binations of these factors.


Further, we evaluated the effect on incidence of OASIS in the short term (few years) after the intervention.

Maintaining the lower incidence of OASIS over time requires continued focus, training and possibly also recertification, in order to preserve necessary clinical skills.


Hopefully, future studies will reveal which preventive strate- gies, separately or combined, can lead to the largest reduction in incidence of OASIS.

Nonetheless, until those studies have been per- formed, we are obliged to prevent as many cases of OASIS as possi- ble to avoid long-term consequences for the women affected.


We found that focusing on prevention of OASIS is associated with a decrease in incidence, but implementation of formal prevention programs did not provide an additional effect.

Possibly, more rigor- ous interventions at the hospitals with formal prevention programs might have caused a significant difference.


Sir,


Congratulations on an important work confirming that it is indeed feasible to react to a rising rate of obstetric anal sphincter injuries (OASIS) and reduce it [1].

Furthermore, you discuss whether the formal program or focus was the most important factor in reducing the rate.

This assumed contradiction is a misconception.

Focus is essential, regardless of the strategy.

Instead, the decisive questions to be answered are what factors made staff members focus, and what they focused on.


In general, one way to help people focus on a task such as implementing a hands-on approach in childbirth is to establish a formal prevention program.

Focus may also be supported by more informal, person-centered or contextual factors such as preparedness for the intervention, competition between departments, meetings, discussions on the internet, and proximity to a department with a program.

Fear of penalties is another important factor in favor of a systems approach.


Some departments in Denmark actually did not experience a fall in the incidence of OASIS despite a perceived focus and the nationwide guideline [2].

Focus may be counteracted by, for example, resistance of influential leaders.

Unfortunately, you did not document process indicators.

It may well be that more or less the same elements for handling delivery were taken up to about the same degree in all departments.

This would of course explain similar results.

A more thorough description of the different factors making the staffs focus, what they focused on, and how often this was applied would have been valuable [3].


You call for studies revealing which elements may lead to the largest reduction in the incidence of OASIS.

In our work, we registered process indicators, and we found the lowest incidence of OASIS in the group of primiparae where a certified midwife used a hand on the baby's head.

The single most important element of the care bundle was using a hand on the head [4].


Thus, in your case, both formal prevention programs and more informal and person-centered factors seem to have brought about a focus on a safer handling of delivery in the short term.

To achieve and sustain a low risk of OASIS in the long term, a formalized systems approach is needed [5].


Sir, We thank Dr. Rasmussen for his interest [1] in our paper [2].

As pointed out in the article, we recognize that formal obstetric anal sphincter injury (OASIS)-preventive programs will also increase the focus on reduction of the incidence of OASIS.

Furthermore, the publication of the Norwegian quality improvement projects has been the inspiration of OASIS-preventive practice in many other countries.

The study by Rasmussen et al. evaluating the different OASIS-preventive factors is interesting, because they, despite implementation of “a package” with certification, were able to analyze the importance of these factors separately [3].

It seems likely that their “package” resembles the one used in Norway, including visible perineum during crowning, manual perineal protection, a hand on the fetal head to slow down the delivery, and focus on communication.

The same factors were included at the two departments with formal prevention programs in our study, and similar to their intervention, those two departments also included compulsory certification of staff members.

The formal preventive programs were initiated by local midwives and obstetricians/residents, and both programs were appreciated by the leaders of the department.


Unfortunately, we do not have information about which preventive strategies staff members focused on at the departments without formal prevention programs.

We did not report or collect process indicators that could have increased our understanding of the process—both at the departments with and at those without formal prevention programs.

However, prospective collection of individual OASIS-preventive factors at all deliveries at the four departments over several years, would have been a tremendous amount of work and probably not feasible.

When evaluating obstetric practice and skills, it remains challenging to evaluate the results from multivariable analyses.

Different risk factors, protective factors and obstetric methods are often associated.

Hence, it is difficult to transfer results from single parameters to other staff members and other obstetric units.

Nevertheless, the finding that controlling the speed of crowning by placing a hand on the fetal head was the single factor that was most important [3], seems logical and important.

Along with the other preventive strategies, continuous focus on reducing speed of crowning is probably essential to reduce the risk of OASIS.


However, the finding that certification of midwives was essential could not be verified in our study.

Certification is time-consuming and costly, and along with the lack of evidence of perineal protection from randomized controlled trials, these were the reasons for not implementing such programs at the two departments without formal prevention programs.

Nevertheless, both individual and general focus are important, but it is plausible that more rigorous preventive programs can cause a sustained lower incidence of OASIS than in departments without such programs [4].

The difficulties associated with a valid OASIS diagnosis at delivery, and the association between OASIS and subsequent anal incontinence should be addressed.

Actually, increased focus on prevention of anal incontinence after delivery is essential.

Clinical assessment and endoanal ultrasound at follow up may provide clinical feedback and help us to understand how OASIS-preventive strategies affect the risk of anal incontinence after delivery.


Based on the institutional standards at Loma Linda University in Loma Linda, California, our study met the criteria for IRB exemption.

We did not receive any financial support for the research, authorship, and publication of this study.


A 2020 directory of former ophthalmology and otolaryngology (ENT) residency programs was obtained from the American Osteo- pathic Colleges of Ophthalmology and Otolaryngology-Head and Neck Surgery (AOCOO-HNS).

This directory represented AOA ENT and ophthalmology programs that existed before the single accreditation process began in 2014.


In January 2020, a secured survey was sent via direct e-mail to PDs of former AOA ENT and ophthalmology programs that did not achieve ACGME accreditation (Appendix).

Follow-up emails were sent on May 12, 2020 and again on May 22, 2020.

The survey helped reveal challenges faced by these programs, many of which were in cities with less than 50,000 people.

This survey examined why accreditation was not pursued or obtained utilizing two questions, each with response options generated through personal communication with AOA ENT and ophthalmology PDs.

Another response option with a comment box was provided for both questions.


(1) If you did not pursue ACGME accreditation, why did your program not pursue ACGME accreditation? ( Choose one or more of the following: excessive cost, excessive paperwork, lack of faculty support, lack of hospital/administration support, ACGME clinical case volume requirements, ACGME research and academic vol- ume requirements, ACGME logistical/facility proximity re- quirements, ACGME surgical case volume requirements, we did not pursue ACGME accreditation, and other.)


(2) If you did apply for ACGME accreditation, why did your program not attain ACGME accreditation? ( Choose one or more of the following: excessive cost, excessive paperwork, lack of faculty support, lack of hospital/administration support, ACGME clinical case volume requirements, ACGME research and academic vol- ume requirements, ACGME logistical/facility proximity re- quirements, ACGME surgical case volume requirements, we did not apply for ACGME accreditation, and other.)


Out of the 16 programs that were issued surveys, 12 re- spondents completed the surveys: six ophthalmology and six ENT PDs.

Ten (83.3%) of the respondents did not pursue ACGME accreditation, and 2 (16.7%) of the respondents pursued ACGME accreditation but were unsuccessful in achieving accreditation.

The most common reason behind the inability of the programs to pursue or achieve accredi- tation was the lack of hospital/administrative support (7; 58.3%).

Other frequently selected reasons included excessive costs and lack of faculty support (5; 41.7%). " Other" was chosen by 50% of respondents, citing common reasons associated with the cost-benefit of accreditation.

ACGME research and academic requirements (4, 33.3%), logistical/facility requirements (3; 25%), excessive paper- work (3; 25%), and surgical case volume requirement (2; 16.7%) were also cited as reasons for not pursuing ACGME accreditation.


Given the relatively small sample size in this survey, data from both ophthalmology and ENT respondents' "Other" reasons in their nonpursuit for ACGME accreditation were aggregated.

The ophthalmology program respondents who chose "Other" cited limited office space and independent third-party consultant recommendation as their reasons not to pursue accreditation from a cost-benefit perspective.

The hospital administration made a decision that reflected the consultant's recommendation.

The responses of ENT pro- grams varied.

One program was part of a hospital system that merged all residency programs with a nearby university and consolidated all specialties in primary care.

Another program closed its ENT residency to expand other residency programs.

One ENT PD stated that the sponsoring institution did not want to commit the time and money to achieve ACGME accreditation; furthermore, the PD believed that the program could have successfully attained ACGME accreditation had the hospital supported the ENT residency.


When the AOA initially debated the SAS, a major concern was regarding the ability of rural programs to achieve ACGME accreditation.

Nearly 30% of the 132 AOA training programs in rural locations did not achieve ACGME accreditation, the majority of which were primary care programs but also included surgical subspecialty fields.

Typically, the lack of access to physician care in rural communities is due to rural hospitals having trouble recruiting physicians and remaining financially viable.

Our survey results also reflect hospitals' financial issues.

Re- spondents highlighted the lack of logistical and adminis- trative support as well as the ongoing costs to maintain AOA surgical specialty programs as significant reasons for not pursuing/receiving ACGME accreditation.

We have provided four recommendations to gain a greater under- standing of and address this rural workforce issue.


Based on our survey results, the most common issues faced by former AOA surgical subspecialty programs that failed to receive ACGME accreditation were related to finances, logistics, and administration rather than clinical and sur- gical volumes.

Lack of quality in programs, such as those with smaller surgical and clinical case volumes, may be logical reasons for closing former programs.

However, it seems that surgical and clinical case volumes was not a common issue for most former AOA ENT and ophthal- mology programs because 3 of the 12 programs cited sur- gical or clinical volume as part of their decision not to pursue ACGME accreditation.


Considering these results, we have recommendations that should interest PDs and Designated Institutional Of- ficials who faced similar issues in other medical spe- cialties, hospital Chief Medical Officers that supervise program transitions, residents interested in how transi- tions toward ACGME accreditation could impact their future medical education, and health policy experts examining physician access in high-need areas.

The first recommendation is to expand Teaching Health Center Graduate Medical Education (THCGME).

Currently, the THCGME model has successfully established GME in high-need areas with high primary care physician retention rates.

However, no such program exists for surgical pro- grams despite increasing needs for surgical subspecialties in the rural workforce.

THCGME funding has been priori- tized to primary care specialties considering workforce supply and demand as well as an increasing national emphasis on primary care.

THCGME, however, now in- cludes surgical fields such as Obstetrics and Gynecology (Ob-Gyn), and existing Ob-Gyn programs can be utilized as a model to develop ENT and ophthalmology programs.


The second recommendation is to study other former AOA surgical subspecialty programs.

Our findings were specific to ENT and ophthalmology programs.

In similar fashion, 50% of former AOA neurosurgery programs transitioned to ACGME accreditation.

However, 90% of urology AOA programs are now ACGME accredited [4].

Systematic in- quiry is necessary to determine whether other affected surgical fields faced similar barriers transitioning to single accreditation.

It may be beneficial to study former AOA urology programs to determine which characteristics of the urology programs contributed to their high transition rate to the ACGME.

It is important to note that among the 10 urology programs that transitioned successfully, four were in cities with a population of less than 50,000.


The third recommendation is to address the lack of insti- tutional commitment and high cost to maintaining sub- specialty programs in high-need areas.

To a certain extent, we propose reexamining specific ACGME requirements to accommodate former AOA residency programs to increase surgical specialty care access in high-need areas.

Re- quirements surrounding academic output (research pro- jects and publications), faculty size, and distance between training sites may be reexamined to reduce costs and in- crease support for these programs.

To help facilitate this recommendation, we call upon the AOA and AACOM to address the previously mentioned ACGME requirements at the federal and ACGME levels.


The fourth recommendation is for the Centers for Medicare & Medicaid Services (CMS) to reconsider its physician reimbursement approach.

Currently, CMS periodically en- acts alterations to their fee schedule that involves the reallocation of funds between fields.

In the last several years, including the proposed fee schedule for 2021, CMS has enacted and proposed cuts to reimbursement for all surgical subspecialties [19].

Although increasing support from primary care specialties is essential and critical to public health, it should not come at the expense of surgical specialties.

Such decline in reimbursements also contrib- uted to ENT and ophthalmology program closures.

In our discussions with PDs, they often mentioned that the cost of enhancing programs to meet ACGME requirements was too high for institutions to justify the investment, especially when considering declining reimbursement from public insurance entities such as CMS.

Multiple institutions determined that it was more financially feasible to pursue their primary care program transitions.


Due to the small number of osteopathic ophthalmology and ENT PDs, there is a statistical limitation on the power of our study.

Other limitations include the lack of participa- tion of administrative stakeholders, the lack of more qualitative responses, and the lack of quantifiable data reflective of each respondent's hospital, community size, number of hospital beds, and department size.

We invited the PDs to participate in this study and did not extend the survey to hospital administrative leaders; hence, we only had the PDs' impressions to trust.

In our survey, we reserved a qualitative response section for PDs to express other thoughts and discussion, allowing further explana- tions regarding the reasoning behind their program's pursuit or nonpursuit for accreditation beyond the reasons they checked on the survey (e.g., costs, administrative support, research, surgical volumes, and other ACGME requirements).

However, we received limited responses in this category.


None reported.


All authors provided substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; all authors drafted the article or revised it critically for important intellectual content; all authors gave final approval of the version of the article to be published; and all authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.


To the Editor:


We read Ahmed et al. ’s recent article “AOA Ophthalmology and Otolaryngology Program Closures as a Model to Highlight Challenges of Maintaining GME in High Need Areas” [1] with great interest and congratulate them on their publication.

They found that previously accredited AOA ophthalmology and otolaryngology residency programs were less likely to obtain ACGME accreditation (47 and 62%, respectively) than other previously accredited AOA surgical subspecialty residency programs, such as urology (90%) [1].


To contribute to their findings and respond to “Recommendation #2,” [1] we found that all 10 of the current urology residencies that successfully merged to ACGME are considered community-based or community-based/university-affiliated programs [2, 3].

Additionally, another study found that urology residents are more profitable than residents of other specialties [4].

This profitability could play a role in the decision to obtain accreditation for urology residency programs over ophthalmology or otolaryngology residency programs.


Two of the successfully transitioned urology residency programs are affiliated with a large university that was also affiliated with five AOA ophthalmology residency programs that never obtained accreditation after the ACGME merger [3, 5].

These five AOA ophthalmology residency programs contributed to 33% of all 15 AOA ophthalmology residencies in 2013 [5].

This accounts for more than half (62.5%) of the AOA ophthalmology residency programs that eventually did not obtain ACGME accreditation.

Because these five programs were all affiliated with one university, we believe that the AOA ophthalmology residency data presented by Ahmed et al. [ 1] may be misleading.

If the university had only been affiliated with one AOA ophthalmology residency program that never obtained accreditation, then the data would reflect that 7 out of 11 AOA ophthalmology residency programs would have received accreditation (64%), which is similar to that of AOA otolaryngology residency programs that successfully merged (62%) [1].


Despite these findings, we agree with the recommendations presented by Ahmed et al. [ 1] The ACGME merger appears to be a setback for osteopathic medical students interested in competitive specialties such as ophthalmology or otolaryngology.

We suggest further research that investigates potential barriers and incentives within a university that may cause it to choose certain surgical subspecialty residency programs (i.e., urology) over others (i.e., ophthalmology and otolaryngology).


To the Editor,


We appreciate the response from the authors [1] regarding our publication [2] on former American Osteopathic Association (AOA)-accredited ophthalmology and otolaryngology programs and their transition to the Accreditation Council of Graduate Medical Education (ACGME).

We agree that financial factors likely influenced individual graduate medical education (GME) institutions’ decision to pursue accreditation of a particular specialty program over another.

Of note, the authors mention in their letter [1] that two of the former AOA-accredited urology programs that transitioned successfully and five of the ophthalmology programs that did not transition successfully were affiliated with a single university.

Due to the affiliation of these five programs (representing 62.5% of the ophthalmology programs that did not get accredited by the ACGME per the authors) with a single institution, the authors feel that the data regarding the failure of many ophthalmology programs to successfully transition may be misleading.

They seem to suggest that since these five programs were affiliated with one university, it should be considered that only one program did not achieve accreditation rather than five.


To understand this issue, it is important to remember the nature of AOA accreditation, GME, and the Commission on Osteopathic College Accreditation (COCA)-accredited medical schools.

Together, these institutions previously implemented an “Osteopathic Post Graduate Training Institution (OPTI) model.

” The OPTI was a representative body composed of members from AOA affiliate organizations created to ensure that “postdoctoral training programs were operating within approved standards, rules and regulations, and were providing educational training satisfactory to the public interest” [3].

It was commonplace for a DO medical school to be affiliated with various independent GME programs, with a regional accreditor and oversight process, such as the OPTI.


While the authors do not cite which five programs were affiliated with one university, we believe they are referring to the five programs that were affiliated as part of a “Consortium of Osteopathic Residencies in Ophthalmology (CORO)” with a single midwestern university [4].

The CORO was founded in 1989, predating the university’s modern statewide campus system.

CORO featured some shared academic elements, such as didactics and access to a surgical simulator.

However, sharing such resources was and is not unique to the CORO or even the state of Michigan, as Henry Ford ophthalmology is home to a state-of-the-art wet lab and has granted access to neighboring ophthalmology programs.


Despite the five programs sharing a loose affiliation with a single university, these were all separate programs, independently accredited, with distinct program directors and department chairs, without interdependence on one another for accreditation.

The mutually exclusive nature of these five programs was so well understood that when we obtained the program roster from the American Osteopathic Colleges of Ophthalmology and Otolaryngology – Head and Neck Surgery prior to the single accreditation process, the programs were listed separately.

As such, we feel that the data presented in the initial study regarding the percentage of ophthalmology programs gaining ACGME accreditation is an accurate representation.


Interoception is understood as the sensing and representation of signals concern- ing the internal state of the body [1,2].

As a general concept, interoception includes two forms of perception: proprioception (signals from the skin and mus- culoskeletal apparatus) and visceroception (signals from the inner organs such as heart rate, breath and hunger).

Garfinkel & Critchley [3] first emphasized the importance of differentiating between different facets of interoceptive processing, suggesting taking the following into account: objective interoceptive accuracy (IAc; e.g. behavioural testing such as performance on heartbeat perception tests), metacognitive awareness (e.g. confidence-accuracy correspondence) and subjective interoceptive sensibility (e.g. as assessed via self-report questionnaires, e.g. body perception questionnaire).

In a recent study, Garfinkel and co-workers [4] investigated these three levels of processing and could demonstrate that sig- nificant correlations between dimensions emerged only within the subgroup of individuals with higher IAc.

They suggest that the relative balance of accuracy, sensibility and awareness dimensions could explain cognitive, emotional and clinical associations of interoceptive ability.


Referring to the study of Garfinkel et al. [ 4], IAc might be the core ability within the construct of interoception underpinning other interoceptive measures.

Individuals differ substantially in measures of IAc, the ability to consciously per- ceive signals arising from the body.

Measuring a person's ability to perceive and & 2016 The Author(s) Published by the Royal Society.

All rights reserved.

accurately report one's heartbeats at rest is often used to quan- tify these differences [1,5-9].

Other methods exist targeting the gastrointestinal or respiratory system [10-14], but only a few studies have investigated interoceptive abilities across different organ systems [10,15], suggesting that interoceptive abilities are associated across modalities to a certain extent.


The neural substrates of the distinct facets of interoceptive processing are still poorly understood.

The insular cortex plays a major role as a cortical projection area of viscerosensory input [16].

Receiving direct viscerosensory input from the thalamus, the posterior and mid insular cortices are implicated as the primary viscerosensory cortices.

However, other cortical (e.g. ventromedial prefrontal cortex, anterior cingulate cortex, somatosensory cortices) and subcortical (e.g. ventral striatum) regions as parts of the 'interoceptive neural network' also receive ascending interoceptive inputs to support the regu- lation of physiology and behaviour [17].


Khalsa et al. [ 18] further emphasized that next to insula and anterior cingulate cortices, primary and secondary somatosensory cortices inner- vating the skin of the chest area are also essential for the self-report of cardiac sensations.

Pollatos et al. [ 19] showed that IAc as assessed by the heartbeat perception task according to Schandry [9] was positively correlated with blood-oxygen- level dependent (BOLD) activity at right insula, inferior parietal lobule and the medial frontal gyrus extending into the cingulate gyrus.

Critchley et al. [ 5] used a heartbeat dis- crimination task and could demonstrate that interoceptive attention was associated with activation in anterior insula, lat- eral somatomotor and adjacent parietal cortices, anterior cingulate and supplementary motor cortices.

IAc was strongest related to activity in right anterior insula/operculum.

Impor- tantly, the authors also examined interoceptive sensibility using questionnaire data and found positive correlations of subscales of the body perception questionnaire with anterior insula activity.


Till now, existing research has been mainly based on correlational findings, and the effects of causal manipulation of brain activity in interoceptive areas by means of brain stimulation remain unknown.


Therefore, transcranial magnetic stimulation (TMS) is a way to experimentally manipulate brain activity in regions associated with certain aspects of interoceptive signal proces- sing that might also be used as an innovative technique in several clinical groups characterized by alternations of inter- oceptive processing such as depression, eating disorders or anxiety disorders [6,12,20 -23].


The so-called heartbeat-evoked potential (HEP) is another methodology for examining the cortical processing of cardiac afferent signals and assessing individual differences in interoceptive processing.

HEPs are related to the automatic processing of cardiac information, and were initially thought to be independent of attentional processes involved in perceiv- ing or detecting internal signals.

The measurement of HEPs uses methods analogous to other evoked potentials.

Typically, electrocortical (encephalographic, EEG) activity is averaged to individual heartbeats, using the electrocardiogram (ECG) R-wave [24].

Individual differences in HEP amplitude are related to IAc, as shown using heartbeat counting tasks [8,25-27].

The sources of the HEP have been localized to insu- lar, somatosensory, rostral cingulate and prefrontal cortices [7].

Because afferent signals from the cardiovascular system con- tinuously reach cortical structures, HEP amplitudes assessed during rest can be interpreted as indicators of central represen- tation of cardiac interoceptive signals independent of overt attention or conscious awareness of cardiac sensations [28].

Therefore, the HEPs are one way to objectively measure one basic aspect of automatic afferent interoceptive processing.


In this context, two recent models of neural structures ser- ving interoceptive processes and their connections to emotions are of great interest.

A recent multihierarchical model of emotion processing proposed by Smith & Lane [29] suggests distinctions between discrete body features rep- resented in somatosensory cortices, posterior insula, nucleus of the tractus solitarii, hypothalamic nuclei and the para- brachial nucleus, while so-called whole-body patterns are represented in the mid and anterior insula.

Emotional con- cepts then occur by appraisal mechanisms involving other brain regions such as the anterior cingulate and the medial prefrontal cortices that refer to this mapping of the body- state.

It is a multistage interoceptive/somatosensory process by which these body state patterns are detected and assigned conceptual emotional meaning [29].

These assumptions are in accordance with other studies showing that the insular cortex and the anterior cingulate cortex (ACC) play crucial roles in connecting interoceptive processes and emotions [24].

Their activation was found to be modulated by cognitive [30] and emotional factors in several studies [31,32].

This view is also in accordance with recent findings from interoception research [33,34] suggesting that subjective appraisal of interoceptive sig- nals reflect processes independent of interoceptive perception accuracy and are related to mechanisms of self-regulation and top-down control.


A second branch of models refers to assumptions of pre- dictive coding with respect to interoceptive processing.

Friston et al. [ 35- 37] suggested that proprioceptive and kinaesthetic perceptions of the body arise from predictions through the same computational principles of active inference as do visual and auditory perceptions of the external world.


Comparable ideas on predictive coding have been summar- ized and used by Seth et al. [ 38] in order to outline how interoception is associated with conscious presence and its disturbances.

The core concept of this model is that a sense of presence arises when informative interoceptive prediction signals are successfully matched to inputs, so that prediction errors are suppressed.


Brain areas contributing to interocep- tive predictive coding include specific brainstem, subcortical and cortical (insular, orbitofrontal, anterior cingulate) regions.

Seth et al. [ 38] suggest that these regions potentially form at least a loose hierarchy: posterior and mid insula sup- port the primary cortical representation of interoceptive signals, with the anterior insula operating as a comparator error module (see [5,39,40]).


Up to now, only a few studies exist testing whether damage or disturbance of critical neural structures involved in intero- ceptive processing leads to assumed deficits.

Ronchi et al. [ 41] demonstrated in one patient that IAc as measured by the heart- beat detection task by Schandry was decreased after right insula resection.

Terasawa and co-workers [42] also found reduced IAc in patients suffering from insula damage.

Up to today, there is no study that has investigated whether an experimental approach using TMS might affect interoception comprising different aspects and levels of interoceptive processing.


Here, we investigated whether interoceptive processes were disturbed by TMS.

Depending on the parameters of stimulation, it has been suggested that repetitive TMS may either increase or decrease the excitability of the targeted corti- cal structure (see [43-45]).

As Huang and co-workers [44] rstb.royalsocietypublishing.org Phil.

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B 371: 20160016 summarized, several studies have shown that when delivered over the primary motor cortex (M1), continuous theta-burst stimulation (cTBS) decreases M1 excitability when delivered in a continuous fashion.


Eighteen healthy young male partici- pants received either cTBS over right insular and right somatosensory cortices or sham stimulation over occipital areas before performing heartbeat detection and a respiratory load estimation task.

Furthermore, the HEP during heartbeat perception (as the most objective marker of automatic proces- sing of cardiac information), assessed after stimulation, was also examined.


We hypothesized that cTBS over somatosen- sory and insular cortices would yield a decrease in accuracy of interoceptive signal processing.

We also hypothesized a deflation of the HEP amplitude after somatosensory and insula stimulation.

An alternation of the emotional aspects of interoceptive signals was hypothesized after insula inhibition only.

A modulation of interoceptive sensibility was assumed after insula stimulation, as this facet refers especially to 'whole-body' patterns.

Whether confidence of interoceptive signal processing is affected by cTBS over insula and somato- sensory cortices should be assessed in an exploratory fashion.


Eighteen healthy male participants were recruited by advertise- ment at the University of Ulm.

Mean age was 23.9 years (s.d. 2.9).

In order to reduce variance owing to menstrual cycle [46,47], we recruited males only.

The sample was not selected with respect to any other criteria.

They gave written informed consent prior to the study and received compensation of E60.

Exclusion criteria were history of brain injury, past or current psychiatric or neurological disorders, severe somatic illness or intake of medication as assessed by anamnestic questionnaire.

Experiments were conducted in accordance with the Declaration of Helsinki with the approval of the local ethics committee.


Participants were informed about the study by staff and they received written information about the experiment.

At each data collection time, participants were examined at the labora- tories of the Clinical and Health Psychology department in Ulm.


First, there was a screening session in which the tasks used in the stimulation sessions were introduced and they were made familiar with the TMS procedure.

At this screening, exclusion criteria and important side effects of cTBS were explained.


From 20 participants screened, 18 took part in the main experiment.


At the first session of the main experiment, the participants were seated in a sound-attenuated chamber, which was connected to the neighbouring equipment room by intercom.


Passive electrodes for EEG (32 channels using a cap, see below), ECG, respiration (belt), electromyography (EMG) (first dorsal interosseous, FDI; muscle of the left hand) and elec- trooculograms (EOG) were attached and individual resting motor threshold was assessed over left primary motor cortex using a PowerMAG 100 stimulator (Mag & More, Munich, Germany) with biphasic pulses and a figure-of-eight coil (PMD70).


First, optimal cortical representation of FDI muscle (motor hot spot) was assessed by determining a coil position over the EEG cap yielding the highest amplitude of the motor evoked potential (MEP).

Resting motor threshold (MEPs . 100 mV in at least 5/10 trials, cf.

[ 48]) was determined, and cTBS intensity was calibrated to 80% of resting motor threshold in accordance with former studies [49].


This value was then used for all stimulation protocols of the participant including the second and third experimental session.


All three experimen- tal sessions were identical to the first one except for the fact that the motor threshold was assessed only at the first session.


The stimulation site (right insular, right somatosensory cortices or central occipital cortex as sham location) was selected using a randomized protocol for all three experimental sessions, i.e. each participant was stimulated three times in a repea- ted measurements design with identical test protocols.


The experimental procedure is depicted in figure 1.


Coil position for each stimulation site was located on the basis of the 10/20 system supplied by the EEG cap (see below).

Optimal coil positions with respect to the 10/20 system were derived in the following way: TMS neuronavigation (PowerMag View) was used with standard head model, and the positions derived were vali- dated in two subjects prior to the experimental sessions using their structural magnetic resonance imaging (MRI) images while wearing an EEG cap to define coil positions targeting the three stimulation sites (see also [50,51]).

Target areas of stimulation were obtained using MRI structural information and an MRI atlas as depicted in figure 1.


(a) The right anterior insula was reached with a coil position over frontotemporal locations building a triangle corresponding to EEG positions FT10, F8, FC6, pointing to FT8 (F6/AF8).

( b) The primary and secondary somatosensory cortices, chest/trunk location, were reached with the centre of the coil within a triangle corresponding to EEG positions CPZ, C2 and CP4, directed to CZ.

Primary and secondary somatosensory cortices of the trunk are not distinguishable by means of TMS navigation.

( c) Central occi- pital cortex (V2/V3) was reached with the coil placed over OZ, directed straight to the horizontal plane.

In all experimental ses- sions, the coil was placed according to these EEG coordinates.

Coil positioning and TMS target areas are depicted in figure 1.


The experimental design is summarized in figure 1 and was the following: first, participants had to rest for 5 min, while baseline measures (heart rate, breathing) were recorded with a sampling rate of 1000 Hz.

They then filled in an interoceptive sensibility state questionnaire designed to assess the momentary subjec- tive perception of bodily sensations focusing on the perception of five bodily systems (heart beat, respiratory functions, trembling, temperature/sweating, gastrointestinal sensations; see examples in the electronic supplementary material, Methods section).


Next, the cTBS took place with 600 pulses applied in 40 s (bursts of three pulses at 50 Hz every 200 ms (5 Hz)) over one of three locations according to the random scheme.

After stimulation, par- ticipants were asked to fill in the interoceptive sensibility state questionnaire once again.

Then, the heartbeat detection task took place.

During the first heartbeat perception task, EEG was also assessed and later used for HEP analyses (see below).

Four heartbeat counting phases of the mental tracking method were used (see [8,9] and also the electronic supplementary material).

After each trial, they were asked to report their confidence of their estimation using a nine-point Likert scale, where one endpoint was labelled 'no confidence at all', and the other endpoint was 'complete confi- dence' (see [4]).

At the end of the task, the participants were asked to evaluate their feelings during heartbeat perception (cardiac inter- oceptive evaluation; see the electronic supplementary material).


IAc was calculated as the mean heartbeat perception score according to the following transformation 1 4 X 1 À ðjrecorded heartbeats À counted heartbeatsjÞ recorded heartbeats : IAc scores typically range from 0 to 1.

Higher scores indicate small differences between the counted and recorded heartbeat and consequently a better IAc.


The respiratory load estimation task took place next.

As no standard test for IAc in the respiratory system exists, we designed a task similar to the one used by Petersen et al. [ 11,12].

The task rstb.royalsocietypublishing.org Phil.

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B 371: 20160016 manipulated breathing effort via respiratory load by switching the diameter of a breathing device (Pari PEP w S-system) resulting in varying expiratory resistance (diameters 1-5 mm, eight levels, in 0.5 mm steps diameter change).

Participants were instructed to maximally expire with constant flow as naturally as possible and not to apply high levels of effort or force in doing so; as the resist- ance levels applied were rather low, the impact of breathing flow or effort on performance is expected to be negligible.

Participants were asked to judge respiratory effort on an eight-point Likert scale, using the highest and lowest loads as anchors.

Several train- ing intervals were used to make the participants familiar with the range of the scale used.


The test then used six trials with varying diameters.

A respiratory accuracy score was calculated analogous to the heartbeat perception task, using the weighted difference scores of the six trials according to the following formula 1 À P 6 k¼1 jestimated resistance À objective resistancej 2625 ðmean difference with random distribution of errors) : Identical to the heartbeat detection, participants rated confidence after each trial.

At the end of the task, participants reported valence, arousal and anxiety when attending to their respiratory functions.


Afterwards, another paradigm was used that will be not reported here.

The first session lasted about 2 h, the second and third sessions lasted about 90 min.


During the heartbeat perception task, EEG activity was recorded continuously from 32 leads (FP1, FPZ, FP2, AF3, AFZ, AF4, F7, F5, Fz, F6, F8, FC5, FCZ, FC6, C5, C1, CZ, C2, C6, CP5, CP1, CPZ, CP2, CP6, P5, PZ, P6, PO3, PO4, O1, OZ, O2), using the Easy-Cap electrode system (Falk Minow Services, Germany) with non-polarizable passive Ag/AgCl electrodes at equidistant positions.

Cz served as a reference and the ground electrode was attached at electrode position F4.

Horizontal and vertical EOGs were recorded.

Impedances were maintained below 5 kV. The signals were amplified using an active amplifier system (Brain Products, Germany) and digitized at a sampling rate of 1000 Hz.

ECG was measured with non-polarizable Ag/AgCl electrodes placed at the right clavicula and left chest.

ECG, EMG and respiration were recorded equivalent to the EEG using an amplifier system (Brain Products, Germany) and were digitized at a sampling rate of 1000 Hz.


All steps of EEG analysis were conducted with the BRAIN VISION ANALYZER v. 2.1 (Brain Products, Germany).

ECG R- waves were detected either automatically online or offline semiautomatically in ECG raw data for later EEG averaging.

EEG was visually inspected and filtered (0.05- 20 Hz).

EEG data were examined for ocular, muscular and other sources of artefacts.

Trials were rejected from the analysis if the voltage exceeded + 50 mV ms 21 in any channel.

EEG data were segmen- ted relative to the detected R-wave triggers, whereby segments were built in epochs ranging from 200 ms before the R-wave trig- ger to 800 ms after the R-wave trigger.

After baseline correction (200 ms pre R-wave trigger as baseline), average HEP waves were computed of R-triggered EEG segments.

HEP amplitude analyses were conducted in accordance with former studies, using a time window of 400 - 600 ms after R-wave during which the electric field artefact is assumed to be negligible (see [52,53]).


Data analyses were performed with the program SPSS (v. 22).

Referring to the cardiac and respiratory system, separate repeated- measures ANOVAs were calculated with the factors location (I, S, O) examining IAc, confidence and interoceptive evaluation (valence, arousal, anxiety).


Furthermore, interoceptive sensibility was examined with the factors location (I, S, O) and time (pre- stimulation, post-stimulation).

For HEP analyses, we selected frontocentral electrodes with highest HEP amplitudes for statistical evaluation and conducted repeated-measures ANOVAs with the factors location (I, S, O) and electrode.


Statistical significance levels reported correspond to p-values less than 0.05, 0.01 and 0.001, rstb.royalsocietypublishing.org Phil.

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B 371: 20160016 respectively.

In the Results section, uncorrected F-values are reported together with the Greenhouse-Geiser epsilon values and corrected degrees of freedom.

In case of multiple comparisons, we used the Bonferroni correction to adjust the alpha errors.


The mean obtained heartbeat perception scores for the three locations are summarized in figure 2 depicting the locations I, S and O. We observed a significant main effect of location (F 2,34 ¼ 6.67; p , 0.01; h 2 ¼ 0.28; 1 ¼ 0.80): post hoc Bonferroni corrected comparisons revealed that IAc was significantly lower after stimulation over right insula as well as over right somatosensory cortices when compared with occipital stimulation ( ps , 0.05).


Figure 3 summarizes the mean obtained confidence scores for the three locations.

We observed a significant main effect of location (F 2,34 ¼ 6.36; p , 0.01; h 2 ¼ 0.27; 1 ¼ 0.87): confidence was significantly lower after insula stimulation when com- pared with somatosensory stimulation ( p , 0.05).

No other significant differences were observed.


Valence, arousal and anxiety during heartbeat perception are summarized in table 1.

Referring to anxiety, a significant main effect of location (F 2,34 ¼ 6.36; p , 0.01; h 2 ¼ 0.27; 1 ¼ 0.87) showed that after insula cTBS anxiety was significantly higher when compared with both other locations.


Respiratory IAc scores are depicted in figure 2.

We observed a significant main effect of location (F 2,34 ¼ 3.44; p , 0.05; h 2 ¼ 0.17; 1 ¼ 0.58).

Post hoc Bonferroni corrected comparisons revealed that IAc was significantly lower after stimulation over right insula when compared with occipital stimulation ( p , 0.05), whereas the observed smaller IAc after somatosensory cTBS did not reach significance.


Cardiac and respiratory IAc were positively correlated after cTBS over somatosensory cortex (r ¼ 0.39, p , 0.05), whereas correlation coefficients for the other locations were not significant (occipital: r ¼ 0.18, p ¼ 0.24; insula: r ¼ 0.25, p ¼ 0.16).


We observed a significant main effect of location (F 2,34 ¼ 6.14; p , 0.05; h 2 ¼ 0.27; 1 ¼ 0.77): confidence was significantly lower after cTBS over right anterior insula when compared with occipital stimulation ( p , 0.05).


Valence, arousal and anxiety during respiratory load estimation are summarized in table 1.

No significant effects were observed.


Mean obtained IS scores are summarized in figure 4.

We observed a significant main effect of time (F 1,17 ¼ 9.84; p , 0.01; h 2 ¼ 0.37; 1 ¼ 0.84) and a significant interaction for location Â time (F 2,34 ¼ 4.99; p , 0.05; h 2 ¼ 0.23; 1 ¼ 0.61).

Post hoc tests showed that mean IS increased only after insula and somatosensory stimulation when compared with before cTBS stimulation (I: F 1,17 ¼ 19.95; p , 0.001; h 2 ¼ 0.54; 1 ¼ 0.99; S: F 1,17 ¼ 8.46; p , 0.01; h 2 ¼ 0.33; 1 ¼ 0.78).


Mean HEPs distribution and HEP amplitudes (at right fronto- central and central locations) are depicted in figure 5 contrasting the three cTBS locations.


Owing to technical problems, only 15 complete datasets could be included.

After visual inspection of the data, we selected FC6 and C6 (in accordance with former research also reporting the most pronounced HEP amplitudes at frontocentral rstb.royalsocietypublishing.org Phil.

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B 371: 20160016 and central locations [8,54]) as the electrodes for statistical analyses.


The repeated-measures ANOVA yielded significant main effects for location (F 2,28 ¼ 3.95; p , 0.05; h 2 ¼ 0.22; 1 ¼ 0.57).

Post hoc Bonferroni corrected comparisons revealed that the HEP amplitude was significantly lower after stimulation over right insula when compared with occipital stimulation ( p , 0.05), whereas the observed smaller HEP amplitude after somatosensory cTBS when compared with occipital stimu- lation did not reach significance (trend level at C6: p ¼ 0.08).


This study showed differential effects for IAc, interoceptive sensibility, subjective feelings and confidence judgements evoked by cTBS of right anterior insular and right somato- sensory cortices (S1 -S2, chest region).

As hypothesized, compared with inhibition of occipital cortices as a reference condition, cTBS of right anterior insula and right somatosen- sory cortices resulted in a significant decline in cardiac IAc, while only cTBS of right anterior insula significantly reduced respiratory IAc.

Cardiac and respiratory accuracy were posi- tively correlated after cTBS over the somatosensory location, whereas for the two remaining locations, correlation coeffi- cients were not significant.

Larger sample sizes are needed to support our interpretation that similar to observed corre- lations between perception accuracy in the cardiovascular and gastrointestinal system [10,15], there is a comparable, but weaker association between these two inner systems.


Whether confidence of interoceptive signal processing is affected by cTBS over insula and somatosensory cortices was assessed in an exploratory fashion.

Interestingly, analyses of confidence judgements of participants' perception accuracy demonstrated that individuals' confidence judgements were reduced after anterior insula stimulation for both cardiac and respiratory signals, whereas somatosensory inhibition affected only cardiac confidence in the opposite direction, i.e. here par- ticipants were more convinced of having accurately perceived their heartbeats although objective perception accuracy declined.

These results suggest that while inhibition of anterior insula reduces both IAc and confidence judgements in a consist- ent way, inhibition of somatosensory cortices is associated with a dissociation of these processes.

This interpretation is in rstb.royalsocietypublishing.org Phil.

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B 371: 20160016 accordance with assumptions proposed by Garfinkel and co- workers [4] highlighting that the relative balance of accuracy, sensibility and awareness dimensions could account for cogni- tive, emotional and clinical associations of interoceptive ability.


Going beyond IAc, cTBS of right anterior insula and right somatosensory cortices led to an immediate increase in interoceptive sensibility as assessed by self-report.

As former studies found a correlation between insula activation and sensibility [5], and this facet of interoceptive processing refers especially to the idea of 'whole-body' patterns as intro- duced by Smith & Lane [29], a modulation of interoceptive sensibility was assumed to occur after insula stimulation.

The fact that cTBS inhibiting somatosensory cortices also modulated interoceptive sensibility in the same direction as cTBS over right anterior insula highlights that, within the assumed hierarchical structure of interoception, hampering a region processing a discrete body feature leads to greater 'noise' in the whole system.

Referring to predictive coding [38], the anterior insula is the key error module that might detect such 'noise' in the system.

This might then lead to an increase of attentional processes examining ongoing dis- crete body sensations and therefore explain why our participants were more aware of a variety of bodily sen- sations including cardiac and respiratory functions, but also trembling, temperature/sweating and gastrointestinal sen- sations.

The latter underscores that effects of cTBS definitely occurred and affected bodily sensations.


As hypothesized, an alternation of the emotional aspects of interoceptive signals as captured by the interoceptive evaluation was modulated only in relation to anxiety after inhibition of anterior insula.

This underpins its pivotal role for processes related to anticipation of aversive stimuli or anxiety disorders [55].

According to the model of Smith & Lane [29], it might be argued that inhibiting anterior insula functions could have primarily disturbed 'whole-body pat- terns' and therefore, the reduction of IAc becomes evident or conscious to the participants, leading to a corresponding decline in metacognitive beliefs of perception security.

In a similar way, together with models of 'interoceptive predic- tion error', this could explain the increases of self-reported subjective feelings of anxiety and arousal and more aver- sive feelings after inhibition of anterior insula.


Considering the role of the insula in integrating bodily representations, affective and cognitive representations and expectations, dis- turbance of its function should evoke an incoherence or mismatch of the patterns of ongoing real-time basic body feedbacks, subjective feelings and beliefs about it, as well as predictions of bodily reactions based on experience.

This disturbance of the interoceptive network in its basic function, as subserved by the insula, may thus induce feelings of gen- eral discomfort, arousal and anxiety, i.e. feelings of a vague conscious notion that an otherwise intact interplay bet- ween these processes and its neuroanatomical basis has been disturbed.


Our results support the notion that the anterior insula is also a key structure for metacognitive awareness of interocep- tive processes.

This interpretation is in accordance with Farb et al. [ 56], who suggested that anterior insula activity during interoception may reflect endogenous attention demands associated with manipulation of interoception at the level of conscious awareness.

Additionally, there is evidence that the insular cortex supports different levels of representation of cur- rent and predictive states and that anterior insula activity may also reflect feelings of general uncertainty during interoception [57].

In the EPIC model of Barrett & Simmons [58], intero- ceptive perception is largely a construction of beliefs that are kept in check by the actual state of the body.

This is achieved by an 'interoceptive system' in the frontal cortex including the cingulate and the anterior insula [58] and could explain why anterior insula inhibition could also affect the whole interoceptive system including the beliefs about one's accuracy.


Because cutaneous sensations are more distinctly rep- resented than visceral sensations and therefore more discriminable, sensations originating in the viscera are often referred to the skin [59].

Therefore, hampering somatosensory input from the chest region might affect cardiac perception to a greater extent than is the case for respiratory perception.

Favouring this assumption, Khalsa et al. [ 18] demonstrated that somatosensory afferents from the skin can also contrib- ute to cardiac judgements.

Another reason why effects on the respiratory load estimation task and related measures of confidence and evaluation were less pronounced might refer to the fact that we applied a fixed order (figure 1), with assessment of the respiratory system always after the car- diovascular system.

Although the prior parts of the experiment were rather short (about 8 -10 min), and though there are several studies showing that cTBS effects last at least 20 min or significantly longer [44,60], it cannot be ruled out that the effects of cTBS were already diminish- ing when compared with the assessment of interoceptive processes in the cardiovascular system.


Following Smith & Lane [29], discrete body features are represented in somatosensory cortices and disturbing these discrete features might affect the relative balance of accuracy, sensibility and confidence dimensions.

Favouring this assump- tion, both insula and somatosensory stimulation led to an increase of interoceptive sensibility as assessed by question- naire.

The HEP as a marker quantifying basic processes of automatic cardiac signal processing was found to be reduced after inhibition of anterior insula.

We suppose that the HEP pri- marily mirrored bottom-up guided automatic cardiac signal processing [7].

As sources of the HEP are located in insular, somatosensory, cingulate and prefrontal cortices (see [7]), both cTBS locations might affect these HEP generators.

The observed HEP modulation goes along with a reduction of IAc on a behavioural level for cardiac signals.


An additional hint that the interplay between different levels of interoceptive processes was affected might be the fact that cardiac IAc was not correlated to the HEP amplitude at central and frontocentral locations as observed in some former studies [8].

Mirroring behavioural results, effects on the HEP amplitude were more pronounced after insula cTBS suggesting that at least during overt attention to one's heart- beats-there was no baseline or rest condition after cTBS to compare with-this region might be more crucial for the inte- gration of cardiac signals as inhibition of right somatosensory cortices affected the HEP amplitude to a lower extent.

This assumption confirms ideas that the ability to be 'aware' of interoceptive signals is thought to depend upon further propa- gation of interoceptive signals to the anterior insula, which has been argued to reflect the integration of afferent physiological signals with higher-order contextual information [17,61], thereby becoming consciously accessible, enabling a subjective affective experience or feeling state [2].


There are several issues to be critically discussed in this study.

One essential point is that there is no guarantee of reaching the anterior insula with a TMS coil positioned over the skull.

We would argue that the effects obtained seem to be specific enough and in accordance with proposed theoretical models to say that anterior parts of the right insula were indeed targeted.


Second, further support stems from research on the auditory cortex where the topographic situ- ation is directly comparable to the attempts to stimulate primary auditory cortex in the case of tinnitus.

It has been shown that chronic tinnitus with a functional correlate in pri- mary auditory cortex can be modulated by rTMS [62,63], despite the larger distance of the coil to the primary auditory cortex ( planum temporale [64]).

Because we compared effects from the frontal stimulation site with two other sites, we are sure that the frontal effects are not unspecific but related to the particular stimulation site, at least close to the anterior insula.


An important limitation refers to the fact that there were no baseline assessments of the HEP and the IAc tasks before the respective stimulation of brain areas.

As we already used a repeated measurements design with three ses- sions per participant, we wanted to reduce effects of repetition on all tasks used.

Other experimental set-ups asses- sing only one or two locations in each participant and using a between-group design might be used in future to address this issue.


An important limitation refers to the fact that IAc in this opportunistic sample was higher than in other studies [65-67]; after occipital stimulation, the observed mean score was 0.77 when compared with, for example, 0.69 observed in a large sample of more than 400 healthy participants [66].

A cause for this might be that we assessed only male participants who have higher IAc in some studies [1,68].

It might also be the case that the TMS procedure itself increased stress and sym- pathetic activation which then, in turn, could facilitate heartbeat rstb.royalsocietypublishing.org Phil.

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B 371: 20160016 detection.

Other studies could show that a sympathetic increase as induced by short-term food deprivation [33] or physical stress [69] increased IAc.

Future studies should therefore use more participants with a greater distribution of IAc to examine whether TMS effects interact with the absolute level of IAc as found for the interplay of different interoceptive levels in a former study [4].

We nevertheless argue that changes in intero- ceptive processes on various levels, as well as modulation of the HEP amplitude, are favouring the interpretation that also in a sample with substantially lower IAc similar effects are to be expected.


Another limitation is that this study concentrated on right lateral effects of cTBS on structures of the interoceptive network.

This can be explained by the fact that right anterior insula has been identified as the most significant site that is strongly related to IAc [5,19].

The right-hemisphere anterior insular cortex provides one cortical focus for the integration of exteroceptive and interoceptive signals [17,70] and this region has been proposed as a neural substrate for self-awareness in the form of the 'material me' [71].

This may be most relevant for effects of interoceptive metacognition and interoceptive sen- sibility, and their relation to effects of IAc, as there is ample evidence for hemispheric laterality of emotion processing and cognitive functions as well as interhemispheric interplay [72].


In conclusion, this is the first study that has demonstrated that cTBS inhibiting right anterior insula and right somatosen- sory cortices efficiently disturbs different facets of interoceptive processing.

Inhibiting anterior insula resulted in a signifi- cant decline in cardiac and respiratory IAc and in a coherent decrease in perception security.

cTBS over somatosensory cortices reduced cardiac IAc and affected metacognitive aware- ness.

Inhibiting right anterior insula and right somatosensory cortices increased interoceptive sensibility.

The HEP, as marker of automatic cardiac signal processing, was decreased after cTBS over right anterior insula.

Our findings strongly suggest that cTBS is indeed an effective tool to investigate the neural network supporting interoceptive processes.

However, it remains to be further elucidated why cardiac and respira- tory perception did not perfectly match and how long TMS effects on interoceptive signal processing remain detectable.


Obviously, future studies should include a broader range of interoceptive tasks as well as a longer observation interval and should also consider potential differential effects of hemispheric laterality when investigating the function of inter- oceptive target regions of the brain via stimulation techniques.

As interoceptive processes are altered in several psychopatho- logic syndromes [6,12,21-23], brain stimulation techniques are a promising tool for interventions.

While cTBS is used to inhibit certain brain regions, other TMS protocols could be applied to improve the access to bodily sensations and empower concomi- tant therapeutic approaches as demonstrated for various disorders, e.g. in the decrease of relapse rates in depression [73].

More clinical research is needed to further elucidate future therapeutic avenues.


Ethical approval by the local ethics board was obtained.

Written informed consent was obtained.


In the field of interoception research, one outstanding question is the precise nature of the neural networks underlying interoceptive processing [1].

The anterior insula (AI) is a key component of contemporary interoception models [2].

However, most evidence implicating the AI in interoceptive processing is correlational and it remains unclear what its precise role in interoception is.

This issue was tackled by Pollatos and co-workers [3].

Using an inhibitory form of transcranial magnetic stimulation (TMS), continuous theta burst stimulation (cTBS), they aimed to provide causal evidence for the involvement of the AI in interoception.

The main results suggest that stimulation aiming to inhibit the AI or the somatosensory cortex disrupted performance, and confidence in this performance, for interoceptive tasks relative to stimulation applied to an occipital control site.

The same stimulation also altered the heartbeat evoked potential (HEP), an EEG measure thought to index cortical processing of one’s heartbeats [4].

The authors interpreted these findings as the impairment of certain aspects of interoceptive processing following cTBS to the right AI, concluding that “cTBS is an effective tool to investigate the neural network supporting interoceptive processes” [3, p. 1].

This study should be commended for its originality, the use of a within-subject design, and multiple concurrent multimodal measures of interoceptive processing.

However, two critical issues cast doubt on the conclusions that can be drawn from these data.


The AI is a deep cortical region, positioned behind frontal cortical regions (including the inferior frontal gyrus and operculum).

Because of the AI’s neuroanatomical position and depth, it is doubtful that TMS could directly reach this region with the parameters used by Pollatos and co-workers.

While anatomically near regions to the AI such as the auditory cortex have been targeted in other areas of research (e.g. using TMS to modulate tinnitus symptoms [5]), it is unclear whether the observed effects are due to stimulation of deeper regions or more lateral association areas that are more likely to be modulated by TMS (e.g. [6,7]).

TMS administered using a figure-of-eight coil is thought to only stimulate brain regions 1.5–3 cm below the scalp [8], while insula depth is estimated at 4–5 cm [9].

Direct stimulation to the cortical depth of the AI may be achieved using double-cone or helmet-shaped coils, although focality of the electrical field is compromised in comparison with superficial cortical stimulation [9].

To establish if TMS could reach the AI with the stimulation parameters employed by Pollatos and co-workers, we used the SimNIBS software [10] to run calculations of the electric field induced using these parameters.

All parameters and results of this simulation are accessible online (https://osf.io/5qbcs/).

As shown in figure 1, the results of this simulation suggest that with these stimulation parameters, only a negligible portion of the electric field reaches the AI.

In their discussion, the authors concede that “there is no guarantee of reaching the AI with a TMS coil positioned over the skull” (p. 8), but then argue that their pattern of results seems specific enough to say that the anterior part of the insula was indeed targeted.

In the light of our simulation results, we contend that it is unlikely that AI activity was directly influenced by the stimulation.


We therefore suggest two possible reinterpretations of Pollatos and co-workers’ results.

Firstly, it is possible that the AI may have been indirectly disrupted via inhibition of cortical regions it is connected to.

Indeed, there is evidence that TMS can affect activity of deeper regions through stimulation of connected cortical areas.

For example, cTBS to other frontal regions (dorsolateral prefrontal cortex) has been shown to indirectly suppress insula activation through modulation of fronto-insular connectivity ([11], see also [12]).

As direct stimulation of the AI in Pollatos et al. ’s experiment was unlikely, one reinterpretation of this data is that worsening of interoceptive performance was the result of indirect modulation of AI activity, via inhibition of more superficial cortical regions.

Alternatively, affected regions in the ventrolateral prefrontal cortex may make a unique contribution to interoceptive processes (indeed, the frontal opercular regions are also activated during interoception tasks; see [13,14]), or during non-interoceptive aspects of interoception tasks.

These cortical regions are considered to play an important role in language and decision-making [15,16], disruption to which could feasibly have impacted on the tasks used by Pollatos and co-workers.

Without control tasks however, the nature of this disruption is unclear, leading us onto our second point: it is unclear whether affected performance on the interoception tasks was specific to interoception, or reflective of a more general transient cognitive impairment.


Future researchers wishing to use similar methods to examine the role of brain regions in interoceptive processing will of course need to consider which control tasks best suit their experimental question, but it is crucial to use a control task that is similar in nature and difficulty to the interoceptive tasks in order to ensure that decrease in performance is not related to alteration of general processes such as attention, memory or sensation.

Such tasks include, but are not limited to, time estimation [17], tone perception [18] and tactile perception [19].

The absence of a control condition is also problematic for the EEG measures used.

Indeed, the authors measured the HEP over right fronto-central sites close to the AI and somatosensory stimulation sites, but further from the occipital control site.

It is therefore possible that cTBS over the right fronto-central areas altered the electrical brain response of these areas in a non-specific manner.

To claim that the disruption of electrocortical potentials caused by the stimulation is specific to the HEP, it is necessary to show that stimulation effects are not generalized to other non-interoceptive evoked potentials (e.g. visual or somatosensory evoked potentials).


In conclusion, non-invasive neurostimulation is arguably one of the most informative tools available in cognitive neuroscience and has certainly been underused in the study of interoception.

The recent report of Pollatos and co-workers is in this regard an innovative exploratory study.

However, we wish to emphasize that stimulating the AI using this technique is a challenging endeavour, and should be carried out with appropriate cautions and control conditions.


We want to respond to the two main points raised by Coll, Penton and Hobson as comment on our article ‘Changes in interoceptive processes following brain stimulation’ [1,2].

First, we want to discuss in more detail the question raised by Coll and co-workers in their comment, namely which regions were stimulated by our set-up.

We are grateful to the authors providing results of a simulation of field distribution using SimNIBS.

Indeed, as we already addressed in the discussion of our article, we cannot be sure that transcranial magnetic stimulation (TMS) directly reaches the anterior insula (AI).

We also refer to the arguments already discussed in our article, but especially important for this issue: The topographic situation when stimulating the AI is directly comparable with the attempts to stimulate primary auditory cortex in the case of tinnitus referring to the auditory cortex. And it has been shown that chronic tinnitus can be modulated by rTMS [3,4], despite the larger distance of the coil to the primary auditory cortex (planum temporale, e.g. [5]).

However, field simulation only demonstrates field distribution relative to a given range.