Functional Connectivity and ECT: New Meta-Analysis

Out on PubMed, from researchers in Bengaluru, India, is this paper:

Resting State Functional Connectivity of Brain With Electroconvulsive Therapy in Depression: Meta-Analysis to Understand Its Mechanisms.

Sinha P, Joshi H, Ithal D.Front Hum Neurosci. 2021 Jan 21;14:616054. doi: 10.3389/fnhum.2020.616054. eCollection 2020.PMID: 33551779

The abstract is copied below:

Introduction: Electroconvulsive therapy (ECT) is a commonly used brain stimulation treatment for treatment-resistant or severe depression. This study was planned to find the effects of ECT on brain connectivity by conducting a systematic review and coordinate-based meta-analysis of the studies performing resting state fMRI (rsfMRI) in patients with depression receiving ECT. Methods: We systematically searched the databases published up to July 31, 2020, for studies in patients having depression that compared resting-state functional connectivity (rsFC) before and after a course of pulse wave ECT. Meta-analysis was performed using the activation likelihood estimation method after extracting details about coordinates, voxel size, and method for correction of multiple comparisons corresponding to the significant clusters and the respective rsFC analysis measure with its method of extraction. Results: Among 41 articles selected for full-text review, 31 articles were included in the systematic review. Among them, 13 articles were included in the meta-analysis, and a total of 73 foci of 21 experiments were examined using activation likelihood estimation in 10 sets. Using the cluster-level interference method, one voxel-wise analysis with the measure of amplitude of low frequency fluctuations and one seed-voxel analysis with the right hippocampus showed a significant reduction (p < 0.0001) in the left cingulate gyrus (dorsal anterior cingulate cortex) and a significant increase (p < 0.0001) in the right hippocampus with the right parahippocampal gyrus, respectively. Another analysis with the studies implementing network-wise (posterior default mode network: dorsomedial prefrontal cortex) resting state functional connectivity showed a significant increase (p < 0.001) in bilateral posterior cingulate cortex. There was considerable variability as well as a few key deficits in the preprocessing and analysis of the neuroimages and the reporting of results in the included studies. Due to lesser studies, we could not do further analysis to address the neuroimaging variability and subject-related differences. Conclusion: The brain regions noted in this meta-analysis are reasonably specific and distinguished, and they had significant changes in resting state functional connectivity after a course of ECT for depression. More studies with better neuroimaging standards should be conducted in the future to confirm these results in different subgroups of depression and with varied aspects of ECT.

Keywords: activation likelihood estimation; depression; dorsal anterior cingulate cortex; electroconvulsive therapy; hippocampus; meta- analysis; posterior cingulate cortex; resting state functional neuroimaging.

The pdf is here.

It must have been a daunting task, writing this paper; reading it certainly was. My brain hurts after slogging through every word of it. The Luddite in me is skeptical of the arcane math and physics, the clinician/researcher in me is glad someone might actually understand the neuroimaging methods and statistics described in this report.

Luddite or not, this is definitely a long ride for a short slide: so, cingulate and hippocampus are involved, with connectivity either up or down. This only gets us a bit further than "certain brain regions change with ECT."

 For those of you interested in the details of the neuroimaging or statistical methods, this is worth a full read (~45 minutes). Just as genetic research is taking a long time to bear fruit in psychiatry, so neuroimaging research, still in its infancy, will take some time to make progress in explicating the mechanism of action of ECT, and the underlying pathophysiology of mood disorders. But it very likely will...