Electroconvulsive therapy disrupts functional connectivity between hippocampus and posterior default mode network

Krzysztof Gbyl*, Vytautas Labanauskas, Christoffer Cramer Lundsgaard, André Mathiassen, Adam Ryszczuk, Hartwig Roman Siebner, Egill Rostrup, Kristoffer Madsen, Poul Videbech

*Corresponding author for this work

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Abstract

Background: The mechanisms underlying memory deficits after electroconvulsive therapy (ECT) remain unclear but altered functional interactions between hippocampus and neocortex may play a role. Objectives: To test whether ECT reduces functional connectivity between hippocampus and posterior regions of the default mode network (DMN) and to examine whether altered hippocampal-neocortical functional connectivity correlates with memory impairment. A secondary aim was to explore if these connectivity changes are present 6 months after ECT. Methods: In-patients with severe depression (n = 35) received bitemporal ECT. Functional connectivity of the hippocampus was probed with resting-state fMRI before the first ECT-session, after the end of ECT, and at a six-month follow-up. Memory was assessed with the Verbal Learning Test – Delayed Recall. Seed-based connectivity analyses established connectivity of four hippocampal seeds, covering the anterior and posterior parts of the right and left hippocampus. Results: Compared to baseline, three of four hippocampal seeds became less connected to the core nodes of the posterior DMN in the week after ECT with Cohen's d ranging from −0.9 to −1.1. At the group level, patients showed post-ECT memory impairment, but individual changes in delayed recall were not correlated with the reduction in hippocampus-DMN connectivity. At six-month follow-up, no significant hippocampus-DMN reductions in connectivity were evident relative to pre-ECT, and memory scores had returned to baseline. Conclusion: ECT leads to a temporary disruption of functional hippocampus-DMN connectivity in patients with severe depression, but the change in connectivity strength is not related to the individual memory impairment.

Original languageEnglish
Article number110981
JournalProgress in Neuro-Psychopharmacology and Biological Psychiatry
Volume132
Number of pages11
ISSN0278-5846
DOIs
Publication statusPublished - 2024

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Keywords

  • Electroconvulsive therapy
  • Hippocampus
  • Major depressive disorder
  • Resting state fMRI

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