Parallel but independent reduction of emotional awareness and corpus callosum connectivity in older age

Martine Skumlien, Donatas Sederevicius, Anders M Fjell, Kristine B Walhovd, René Westerhausen

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9 Citations (SciVal)

Abstract

Differential functional specialization of the left and right hemispheres for linguistic and emotional functions, respectively, suggest that interhemispheric communication via the corpus callosum is critical for emotional awareness. Accordingly, it has been hypothesized that the age-related decline in callosal connectivity mediates the frequently demonstrated reduction in emotional awareness in older age. The present study tests this hypothesis in a sample of 307 healthy individuals between 20-89 years using combined structural and diffusion-tensor magnetic resonance imaging (MRI) of the corpus callosum. As assumed, inter-hemispheric connectivity (midsagittal callosal area and thickness, as well as fractional anisotropy, FA) and emotional awareness (i.e., increase in externally-oriented thinking, EOT; assessed with the Toronto Alexithymia Scale, TAS-20) were found to be reduced in older (> 60 years) compared to younger participants. Furthermore, relating callosal measures to emotional awareness, FA in the genu of the corpus callosum was found to be negatively correlated with EOT in male participants. Thus, "stronger" structural connectivity (higher FA) was related with higher emotional awareness (lower EOT). However, a formal mediation analysis did not support the notion that age-related decline in emotional awareness is mediated by the corpus callosum. Thus, the observed reduction of emotional awareness and callosal connectivity in older age likely reflects parallel but not inter-dependent processes.

Original languageEnglish
Pages (from-to)e0209915
JournalPLoS ONE
Volume13
Issue number12
DOIs
Publication statusPublished - 31 Dec 2018

Bibliographical note

Data Availability Statement: The general study was approved by the “Regional Ethic Committee of south-eastern Norway (REK sør-øst; reference 2010/3407; see https://helseforskning.etikkom.no) and an update was filed and approved (25.03.2015) regarding the third wave of data collection which includes the here relevant questionnaire (TAS-20). In the informed consent of the third wave data collection, the participants provided “consent to share samples and data with other Norwegian universities or research institutes, including universities abroad, also outside the EU/EEA [European Union/European Economic Area]” (translated from the informed consent form). Thus, the consent allows the authors to share data with researchers upon request. However, participants were not informed about the possibility that the data could be published on an individual level and accordingly did not consent such unrestricted publication of their data. Furthermore, in the new EU General Data Protection Regulation (GDPR), ratified also by Norway as member of the EEA, it reads (Chapter 2, Art 6; https://gdpr-info.eu/art-6gdpr/) that “Processing shall be lawful only if and to the extent that at least one of the following applies: (a) the data subject has given consent to the processing of his or her personal data for one or more specific purposes”. The purpose for which the participants provided consent was: “The project has the aim to map brain changes over time and how they are associated with changes in mental functioning” (translated from the informed consent form). Accordingly, participant gave consent to use and share the data for research within this research purpose. Thus, although the authors cannot make their study’s data publicly available at the time of publication, all authors commit to make the data underlying the findings described in this study fully available without restriction to those who request the data, in compliance with the PLOS Data Availability policy. For data sets involving personally identifiable information or other sensitive data, data sharing is contingent on the data being handled appropriately by the data requester and in accordance with all applicable local requirements (as outlined above). The data underlying the results presented in the study are available via the corresponding author (Rene´ Westerhausen; rene.westerhausen@psykologi.uio. no, the project manager Anders M. Fjell; a.m. fjell@psykologi.uio.no; or via the webpage of the Center for Lifespan Changes in Brain and Cognition, LCBC, University of Oslo, Norway; https://www.oslobrains.no/).

Funding: The authors received no specific funding for this work.

Keywords

  • Adult
  • Aged
  • Aged, 80 and over
  • Aging/physiology
  • Awareness/physiology
  • Connectome
  • Corpus Callosum/physiology
  • Emotions/physiology
  • Female
  • Humans
  • Male
  • Middle Aged

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