Lateralized memory circuit dropout in Alzheimer's disease patients

Ashley Tyrer*, Jessica R Gilbert, Sarah Adams, Alexandra B Stiles, Azziza O Bankole, Iain D Gilchrist, Rosalyn Moran

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)

Abstract

Altered connectivity within neuronal networks is often observed in Alzheimer's disease. However, delineating pro-cognitive compensatory changes from pathological network decline relies on characterizing network and task effects together. In this study, we interrogated the dynamics of occipito-temporo-frontal brain networks responsible for implicit and explicit memory processes using high-density EEG and dynamic causal modelling. We examined source-localized network activity from patients with Alzheimer's disease (n = 21) and healthy controls (n = 21), while they performed both visual recognition (explicit memory) and implicit priming tasks. Parametric empirical Bayes analyses identified significant reductions in temporo-frontal connectivity and in subcortical visual input in patients, specifically in the left hemisphere during the recognition task. There was also slowing in frontal left hemisphere signal transmission during the implicit priming task, with significantly more distinct dropout in connectivity during the recognition task, suggesting that these network drop-out effects are affected by task difficulty. Furthermore, during the implicit memory task, increased right frontal activity was correlated with improved task performance in patients only, suggesting that right-hemisphere compensatory mechanisms may be employed to mitigate left-lateralized network dropout in Alzheimer's disease. Taken together, these findings suggest that Alzheimer's disease is associated with lateralized memory circuit dropout and potential compensation from the right hemisphere, at least for simpler memory tasks.
Original languageEnglish
Pages (from-to)fcaa212
Number of pages12
JournalBrain Communications
Volume2
Issue number2
DOIs
Publication statusPublished - 10 Dec 2020

Keywords

  • EEG
  • Alzheimer's disease
  • memory
  • executive function
  • computational psychiatry

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  • DCM for Evoked Responses

    Tyrer, A., 15 Oct 2021, SPM12 Manual. p. 453-464 12 p.

    Research output: Chapter in Book/Report/Conference proceedingChapter in a book

    Open Access

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