Interhemispheric asymmetry of motor cortical excitability in major depression as measured by transcranial magnetic stimulation.
BACKGROUND
Neuroimaging studies of major depressive disorder (MDD) indicate interhemispheric differences in prefrontal cortical activity (right greater than left).


OBJECTIVE
To investigate whether there are any interhemispheric differences of motor cortical excitability in MDD.


METHODS
Eight patients with treatment-refractory MDD off medication were assessed for the severity of their depression, and transcranial magnetic stimulation studies (bilateral motor threshold and paired-pulse studies) were conducted. Eight normal controls were also studied.


RESULTS
MDD patients showed significant interhemispheric differences in motor threshold and paired-pulse curves, both of which showed lower excitability on the left hemisphere. Such differences were absent in controls.


CONCLUSIONS
Our findings may aid the further understanding of the neurophysiology underlying MDD.
Maeda
F
F
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Cambridge, MA, USA.
Keenan
J P
JP
Pascual-Leone
A
A
D000328:Adult; D000368:Aged; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation