Browsing by Author "Yahia-Cherif, L"

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    Age-related decline in the responsiveness of motor cortex to plastic forces reverses with levodopa or cerebellar stimulation
    (Neurobiology of aging, 2014-11) Kishore, A; Popa, T; James, P; Yahia-Cherif, L; Backer, F; Varughese, CL; Govind, P; Pradeep, S; Meunier, S
    The plasticity of motor cortex is integral for motor memory and skills acquisition but it declines with aging. Forty healthy volunteers, across 6 decades, were tested to examine the (a) age-dependency of motor cortex responsiveness to plasticity induction, as measured from the response to paired associative stimulation (PAS) and the (b) effect of aging on the cerebellar modulation of motor cortex response to PAS. We examined if reduced dopaminergic transmission was involved in the age-related decline of response to PAS by retesting 10 of the older subjects after a single dose of levodopa. There was a substantial decline in the motor cortex response to PAS with aging, which was restored by levodopa in the older subjects. The cerebellar modulation of motor cortex response to PAS was less vulnerable to aging and a single session of cerebellar inhibition reinstated the cortical responsiveness in older subjects. Both levodopa and cerebellar inhibition can be tested for their ability to enhance motor skills acquisition and motor performance in the elderly individuals.
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    Motor cortex plasticity can indicate vulnerability to motor fluctuation and high L-DOPA need in drug-naïve Parkinson's disease.
    (Parkinsonism Relat Disord., 2016-12) Kishore, A; James, P; Krishnan, S; Yahia-Cherif, L; Meunier, S; Popa, T
    Introduction: Motor cortex plasticity is reported to be decreased in Parkinson's disease in studies which pooled patients in various stages of the disease. Whether the early decrease in plasticity is related to the motor signs or is linked to the future development of motor complications of treatment is unclear. The aim of the study was to test if motor cortex plasticity and its cerebellar modulation are impaired in treatment-naïve Parkinson's disease, are related to the motor signs of the disease and predict occurrence of motor complications of treatment. Methods: Twenty-nine denovo patients with Parkinson's disease were longitudinally assessed for motor complications for four years. Using transcranial magnetic stimulation, the plasticity of the motor cortex and its cerebellar modulation were measured (response to paired-associative stimulation alone or preceded by 2 active cerebellar stimulation protocols), both in the untreated state and after a single dose of L-DOPA. Twenty-six matched, healthy volunteers were tested, only without L-DOPA. Results: Patients and healthy controls had similar proportions of responders and non-responders to plasticity induction. In the untreated state, the more efficient was the cerebellar modulation of motor cortex plasticity, the lower were the bradykinesia and rigidity scores. The extent of the individual plastic response to paired associative stimulation could indicate a vulnerability to develop early motor fluctuation but not dyskinesia. Conclusions: Measuring motor cortex plasticity in denovo Parkinson's disease could be a neurophysiological parameter that may help identify patients with greater propensity for early motor fluctuations.