Effects of right unilateral electroconvulsive therapy on motor cortical excitability in depressive patients

Electroconvulsive therapy (ECT) is a widely acknowledged effective treatment for severe major depression. ECT produces considerable anticonvulsant effects that may be related to an increased GABA-ergic neurotransmission. We aimed to explore whether motor cortical excitability as assessed with single and paired pulse transcranial magnetic stimulation (TMS) could be used to investigate these anticonvulsant effects. Therefore, parameters of motor cortical excitability were investigated in 10 patients before and after 10 sessions of right unilateral ECT. After 10 sessions of right unilateral ECT, an enhanced activity of inhibitory circuits in human motor cortex had been observed, as measured by both increased intracortical inhibition and cortical silent period duration, whereas intracortical facilitation and resting motor threshold remained unchanged. The reduction of seizure duration in the course of ECT was associated with clinical improvement and an increase in intracortical inhibition. We interpret this finding as further indirect evidence for changes in inhibitory circuits in the course of ECT in patients with major depression.