Background: Since the 1970s, a number of neuroimaging studies of electroconvulsive therapy (ECT) have been conducted to elucidate the working action of this highly efficacious treatment modality. The technologies used are single photon emission tomography, positron emission tomography, magnetic resonance imaging, magnetic resonance spectroscopy, and quantitative electroencephalography.
Methods: A PubMed literature search with focus on clinical studies was made from the inception of the database until December 2013 using the search terms electroconvulsive therapy and neuroimaging.
Results: Early methods allowing only identification of global changes of cerebral blood flow and cerebral metabolism show considerable ictal increases of these measures, which normalize during the postictal period. Later methodological developments have given access to measurements of minute activity changes in localized cortical and subcortical areas of the brain and have revealed differences in neurophysiology and metabolism between the hyperactive ictal state and the restorative interictal/postictal periods. Recent magnetic resonance imaging studies seem to pave way for new insights into ECT's effects on increased connectivity in the brain during depression.
Conclusion: The existing data reveal considerable variations among studies and therefore do not yet allow the formulation of a unified hypothesis for the mechanism of ECT. The rapid developments in imaging technology, however, hold promises for further elucidation of the mode of action of ECT.