Electroconvulsive therapy disrupts functional connectivity between hippocampus and posterior default mode network.
K. Gbyl, Vytautas Labanaukas, C. C. Lundsgaard, A. Mathiassen, Adam Ryszczuk, H. Siebner, E. Rostrup, K. Madsen, Poul Videbech
Progress in Neuro-psychopharmacology and Biological Psychiatry February 1, 2024 DOI: 10.1016/j.pnpbp.2024.110981 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 35 |
| Population | In-patients with severe depression |
| Duration | Before first ECT session, after end of ECT, and six-month follow-up |
| Measures | Verbal Learning Test - Delayed Recall, resting-state fMRI |
| Topics | Default mode network |
| Key findings | Bitemporal ECT was followed by reduced functional connectivity between three of four hippocampal seeds and posterior default mode network nodes (Cohen's d -0.9 to -1.1) in the week after treatment, alongside memory impairment. However, individual memory changes did not correlate with connectivity reductions, and both connectivity and memory returned to baseline by six months. The authors conclude the connectivity disruption is temporary and does not account for individual memory impairment. |
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.