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Reduced transcallosal inhibition in Alzheimer’s disease compared to healthy controls
Author(s) -
Agrawal Adesh Kumar,
Mehta Urvakhsh M.,
Naik Shalini S.,
Thanki Milind Vijay,
Mitra Sayantanava,
Varghese Mathew
Publication year - 2020
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1002/alz.045036
Subject(s) - corpus callosum , transcranial magnetic stimulation , clinical dementia rating , dementia , psychology , audiology , alzheimer's disease , medicine , neuroscience , stimulation , disease
Background In Alzheimer’s disease (AD), structural changes in the corpus callosum are known to precede clinical signs. Transcranial magnetic stimulation (TMS) can be used to study functional integrity of the corpus callosum through ipsilateral silent period (iSP). We examined iSP duration between patients with mild cognitive impairment (MCI)/AD and healthy controls. Method 15 patients of AD (n = 10) and MCI (n = 5), and 15 healthy controls were recruited. All subjects completed clinical (Clinical Dementia Rating Scale, Instrumental Activities of Daily Living Scale for Elderly, Everyday Abilities scale for India, & Neuropsychiatric Inventory) and cognitive (Hindi Mental Status Examination, attention, working memory and semantic verbal memory) evaluations. Twenty single TMS pulses (suprathreshold pulse delivered to right motor cortex with the ipsilateral/right hand maintained in 20% of its maximal contraction) and twenty paired pulses (subthreshold priming pulse delivered 3ms before suprathreshold test pulse over left motor cortex) were delivered to assess inter‐cortical inhibition (iSP) and intra‐cortical inhibition (ICI) respectively. Result iSP duration was significantly reduced (df = 27; t = ‐2.76; p‐0.01)) in the clinical group as compared to healthy controls. However, there were no significant differences in ICI. There was no significant association between iSP and clinical or cognitive performance. Conclusion The presence of inter‐cortical rather than intra‐cortical inhibition deficits in AD supports the hypothesis of corpus callosum dysfunction in AD. A lack of association between iSP and severity indices suggest this measure may be examined as an early marker of AD.