"Multimetric" Review of fMRI Findings in ECT
Out on PubMed, from researchers in Spain, Australia and the USA, is this review article:
A multimetric systematic review of fMRI findings in patients with MDD receiving ECT.
Prog Neuropsychopharmacol Biol Psychiatry. 2020 Nov 13:110178. doi: 10.1016/j.pnpbp.2020.110178. Online ahead of print. PMID: 33197507 The abstract is copied below:
And from the text:[Of the 34 articles]...the resting-state fMRI metrics employed included: seed-based resting-state functional connectivity (n=17), resting-state network connectivity (n=10), ReHo (n=3), ALFF (n=4), and fALFF (n=5).
Moreover, regarding the number of results per metric, resting-state functional connectivity studies seem to capture more ECT-related changes than task-based and/or resting-state activity. Although this finding may be partially accounted for the fact that resting-state connectivity (across 2 different metrics) was more frequently assessed than task-based and/or resting-state activity (27 vs. 18 studies), ECT-induced resting-state functional connectivity increases seems to be the most consistently reported finding. Specifically, resting-state functional connectivity increases between the SFG and the MFG and other brain regions with multimetric changes (including the orbital gyrus, the IFG, the PCC, the dACC, the pgACC, the sgACC, the temporal gyri, the insula, the hippocampus, the putamen, the precuneus and the angular gyrus) are the most consistent findings observed in patients with MDD after ECT...
Moreover, regarding the number of results per metric, resting-state functional connectivity studies seem to capture more ECT-related changes than task-based and/or resting-state activity. Although this finding may be partially accounted for the fact that resting-state connectivity (across 2 different metrics) was more frequently assessed than task-based and/or resting-state activity (27 vs. 18 studies), ECT-induced resting-state functional connectivity increases seems to be the most consistently reported finding. Specifically, resting-state functional connectivity increases between the SFG and the MFG and other brain regions with multimetric changes (including the orbital gyrus, the IFG, the PCC, the dACC, the pgACC, the sgACC, the temporal gyri, the insula, the hippocampus, the putamen, the precuneus and the angular gyrus) are the most consistent findings observed in patients with MDD after ECT...
While ECT-induced functional changes appear to be variably and broadly distributed across the brain, not all brain regions are found to be changed by the same number of fMRI metrics and with the same degree of replicability. In this sense, the superior and middle frontal gyri might act as critical nodes modulating both cortico-limbic and posterior default mode network in patients with MDD after ECT. Although these frontal modulations are directly linked to ECT clinical response, sgACC might also facilitate the circuit modulation needed to bring about clinical recovery after ECT. Cerebellar changes, although present, do not seem to be related to ECT clinical response. Further research is warranted to ascertain the specific involvement of the cerebellum in the mechanism of action of ECT.
The authors of this ambitious review attempt to compare the apples of some fMRI studies with the oranges of others; surprisingly, they seem to have had some success. Connectivity changes in the frontal lobes are linked to changes in the limbic lobe; changes in the cerebellum may be unrelated to ECT response: the brain, from front to back, in ECT!
While I applaud these investigators, and this is heady stuff (pardon the pun), I am not yet ready to commit much of my cortical space to the details. Such research is in its infancy and replication is not sufficient to arrive at definitive conclusions. Ongoing large-scale MRI ECT investigations should provide clarification.
For those of you interested in the neuroanatomy of functional brain connectivity and ECT, this paper is worth a full and careful read (about 20 minutes).
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