title: Reduced interhemispheric inhibition in mild cognitive impairment.
abstract: In mild cognitive impairment (MCI), the corpus callosum is known to be affected structurally. We evaluated callosal function by interhemispheric inhibition (IHI) using transcranial magnetic stimulation (TMS) in MCI patients. We investigated 12 amnestic MCI patients and 16 healthy age-matched control subjects. The IHI was studied with a paired-pulse TMS technique. The conditioning TMS was given over the right primary motor cortex (M1) and the test TMS over the left M1. Motor evoked potentials were recorded from the relaxed first dorsal interosseous muscle. We also studied other motor cortical circuit functions; short-latency afferent inhibition (SAI), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Both the amount of IHI and SAI were significantly reduced in MCI patients as compared with control subjects, whereas SICI or ICF did not differ between them. The degree of IHI significantly correlated with neither the mini-mental state examination score nor the degree of SAI. Our results suggest that transcallosal connection between bilateral M1 is primarily involved in MCI, regardless of SAI dysfunction.
authors.affiliation: Division of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. rtsutsumi-tky@umin.ac.jp
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Tsutsumi
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Hanajima
authors.forename: Masashi
authors.initials: M
authors.lastname: Hamada
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Shirota
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Matsumoto
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Terao
authors.forename: Shinya
authors.initials: S
authors.lastname: Ohminami
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Shimada
authors.forename: Shoji
authors.initials: S
authors.lastname: Tsuji
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ugawa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D054022:Cerebrum / Q000503:physiopathology*; D060825:Cognitive Dysfunction / Q000175:diagnosis / Q000503:physiopathology*; D003337:Corpus Callosum / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000503:physiopathology*