Research Article

Experimental Brain Research

, Volume 218, Issue 1, pp 21-26

Reduced interhemispheric inhibition in mild cognitive impairment

  • Ryosuke TsutsumiAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo Email author 
  • , Ritsuko HanajimaAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo
  • , Masashi HamadaAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo
  • , Yuichiro ShirotaAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo
  • , Hideyuki MatsumotoAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo
  • , Yasuo TeraoAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo
  • , Shinya OhminamiAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo
  • , Yoshihiro YamakawaAffiliated withDepartment of Geriatric Medicine, Graduate School of Medicine, Osaka City University
  • , Hiroyuki ShimadaAffiliated withDepartment of Geriatric Medicine, Graduate School of Medicine, Osaka City University
    • , Shoji TsujiAffiliated withDivision of Neuroscience, Department of Neurology, Graduate School of Medicine, University of Tokyo
    • , Yoshikazu UgawaAffiliated withDepartment of Neurology, School of Medicine, Fukushima Medical UniversityJST, Research Seeds Program

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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.

Keywords

Mild cognitive impairment Alzheimer’s disease Corpus callosum Interhemispheric inhibition Short-latency afferent inhibition Transcranial magnetic stimulation