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Published July 2020 | Published + Supplemental Material
Journal Article Open

Integration Between Cerebral Hemispheres Contributes to Defense Mechanisms


Defense mechanisms are mental functions which facilitate coping when real or imagined events challenge personal wishes, needs, and feelings. Whether defense mechanisms have a specific neural basis is unknown. The present research tested the hypothesis that interhemispheric integration plays a critical role in defense mechanism development, by studying a unique sample of patients born without the corpus callosum (agenesis of the corpus callosum; AgCC). Adults with AgCC (N = 27) and matched healthy volunteers (N = 30) were compared on defense mechanism use across increasing levels of developmental maturity (denial, least; projection, intermediate; identification, most). Narratives generated in response to Thematic Apperception Test images were scored according to the Defense Mechanism Manual. Greater use of denial and less identification was found in persons with AgCC, compared to healthy comparisons. This difference emerged after age 18 when full maturation of defenses among healthy individuals was expected. The findings provide clinically important characterization of social and emotional processing in persons with AgCC. More broadly, the results support the hypothesis that functional integration across the hemispheres is important for the development of defense mechanisms.

Additional Information

© 2020 Paradiso, Brown, Porcerelli, Tranel, Adolphs and Paul. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Received: 13 March 2020; Accepted: 09 June 2020; Published: 07 July 2020. Data Availability Statement: All datasets generated for this study are included in the article/Supplementary Material. Ethics Statement: The studies involving human participants were reviewed and approved by the Human Subjects Review Committee at the Travis Research Institute (data collection) and Institutional Review Board of the California Institute of Technology (data analysis). Written informed consent to participate in this study was provided by participants ages 18 and older and by the participants' legal guardian/next of kin of participants ages 17 and below. Author Contributions: LP and SP designed the study. LP and WB collected the data. SP and JP administered the DMM scoring. LP analyzed the data. SP, LP, RA, and DT drafted the manuscript. JP edited the manuscript. All the authors commented on the manuscript. Funded in part by a grant from the Simons Foundation (LP and RA) and by Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under Award Number R01HD092430 (LP). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. SP research time at Caltech was supported by the National Institute on Aging (5K23AG027837). The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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August 19, 2023
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