title: Impaired interhemispheric interactions in patients with major depression.
abstract: Previous studies have shown that patients with major depression have an interhemispheric imbalance between right and left prefrontal and motor cortex. We aimed to investigate the interhemispheric interactions in patients with major depression using repetitive transcranial magnetic stimulation (rTMS). Thirteen patients with major depression and 14 age-matched healthy subjects participated in this study. Corticospinal excitability before and after 1 Hz rTMS (applied to the left primary motor cortex) was assessed in the left and right motor cortex and these results were compared with those in healthy subjects. There was a significant difference in the interhemispheric effects between patients with depression and healthy subjects. In healthy subjects, 1 Hz rTMS significantly decreased corticospinal excitability in the stimulated, left hemisphere and increased it in the contralateral, right hemisphere. In depressed subjects, 1 Hz rTMS also decreased corticospinal excitability in the left hemisphere; however, it induced no significant changes in corticospinal excitability in the contralateral, right hemisphere. In addition, there was a significant correlation between the degree of interhemispheric modulation and the severity of the depression as indexed by the Beck Depression Inventory scores. Our findings showing a decreased interhemispheric modulation in patients with major depression are consistent with the notion that mood disorders are associated with slow interhemispheric switching mechanisms.
authors.affiliation: Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Sami
authors.initials: S
authors.lastname: Bajwa
authors.forename: Felix
authors.initials: F
authors.lastname: Bermpohl
authors.forename: Sergio P
authors.initials: SP
authors.lastname: Rigonatti
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
authors.forename: Paulo S
authors.initials: PS
authors.lastname: Boggio
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
mesh_terms: D000328:Adult; D000339:Affect / Q000502:physiology; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D004292:Dominance, Cerebral / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D009433:Neural Inhibition / Q000502:physiology; D010555:Personality Inventory; D011712:Pyramidal Tracts / Q000503:physiopathology; D009435:Synaptic Transmission; D050781:Transcranial Magnetic Stimulation