“It has not been know exactly how ECT works. It is known that ECT reduces brain activity and raises seizure threshold (makes it less likely to have a seizure). This implies that overall neuronal activity is reduced, so perhaps ECT is inhibiting overactivity in a part of the brain that is driving the depression. That hypothesis is supported by a recent study that uses fMRI scanning to look at brain activity in nine patients with major depression before and after ECT. They found:
A comparison of pre- and posttreatment functional connectivity data in a group of nine patients revealed a signiﬁcant cluster of voxels in and around the left dorsolateral prefrontal cortical region (Brodmann areas 44, 45, and 46), where the average global functional connectivity was considerably decreased after ECT treatment (P < 0.05, family-wise error-corrected). This decrease in functional connectivity was accompanied by a signiﬁcant improvement (P < 0.001) in depressive symptoms
Once way to interpret this result is that some patients with major depression have overactive connectivity between that part of the brain that generates the emotion of depression and the part of the brain involved in cognition and concentration. In these patients, therefore, their depressed mood has a significant effect on their thoughts and ability to concentrate. ECT appears to reduce this hyperconnectivity, which should significantly reduce the symptoms of depression.
This is all consistent with prior research on depression, and makes good sense. Still, it’s a small study that needs to be replicated and the whole question further explored.” (via NeuroLogica Blog ).