Motor cortex excitability after vagus nerve stimulation in major depression

Recent data suggest that inhibitory pathways may be involved in the pathophysiology of depression and in the mode of action of some antidepressant interventions. The aim of the present study was to test whether vagus nerve stimulation (VNS) can affect motor cortex excitability. Measures of motor cortical excitability were probed by using single-pulse and paired-pulse transcranial magnetic stimulation at baseline, after 10 weeks of left VNS, and additionally, in an on-off paradigm in 10 patients with treatment-resistant unipolar depression. Ten weeks of VNS was associated with a selective and pronounced increase in intracortical inhibition, whereas no changes occurred in the on-off paradigm. These results suggest that VNS is capable of changing motor cortical excitability in patients with depression.