R Chen1, S Kumar, R R Garg, A E Lang. 1. Division of Neurology and The Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario M5T 2S8, Canada. robert.chen@uhn.on.ca
Abstract
OBJECTIVES: To examine the time course of corticospinal excitability before and after voluntary movement in Parkinson's disease (PD). METHODS: We studied 9 mild PD patients at least 12 h off medications and 11 healthy volunteers in a simple reaction time (RT) paradigm. Suprathreshold transcranial magnetic stimulation was delivered to the left motor cortex at intervals covering the periods before and after movement. RESULTS: PD patients (284+/-90 ms) and normal subjects (282+/-56 ms) had similar median RT. The time courses of both the premovement increase and the postmovement decrease in corticospinal excitability were significantly different between PD patients and normal subjects. The increase in motor-evoked potential (MEP) amplitudes began earlier for PD patients (200 ms before electromyographic (EMG) onset) than for normal subjects (150 ms before EMG onset), but the rate of increase was slower in PD patients than controls. After EMG offset, MEP amplitudes were increased for about 150 ms in normal subjects, but in PD patients this period was prolonged to about 350 ms. CONCLUSIONS: Impairment of motor cortex activation and deactivation is an early feature of PD and may be a physiological correlate of bradykinesia. The normal RT in our patients may be related to the earlier occurrence of the premovement increase in corticospinal excitability compensating for the slower rate of rise.
OBJECTIVES: To examine the time course of corticospinal excitability before and after voluntary movement in Parkinson's disease (PD). METHODS: We studied 9 mild PDpatients at least 12 h off medications and 11 healthy volunteers in a simple reaction time (RT) paradigm. Suprathreshold transcranial magnetic stimulation was delivered to the left motor cortex at intervals covering the periods before and after movement. RESULTS:PDpatients (284+/-90 ms) and normal subjects (282+/-56 ms) had similar median RT. The time courses of both the premovement increase and the postmovement decrease in corticospinal excitability were significantly different between PDpatients and normal subjects. The increase in motor-evoked potential (MEP) amplitudes began earlier for PDpatients (200 ms before electromyographic (EMG) onset) than for normal subjects (150 ms before EMG onset), but the rate of increase was slower in PDpatients than controls. After EMG offset, MEP amplitudes were increased for about 150 ms in normal subjects, but in PDpatients this period was prolonged to about 350 ms. CONCLUSIONS: Impairment of motor cortex activation and deactivation is an early feature of PD and may be a physiological correlate of bradykinesia. The normal RT in our patients may be related to the earlier occurrence of the premovement increase in corticospinal excitability compensating for the slower rate of rise.
Authors: David Lindenbach; Melissa M Conti; Corinne Y Ostock; Jessica A George; Adam A Goldenberg; Mitchell Melikhov-Sosin; Emily E Nuss; Christopher Bishop Journal: J Neurosci Date: 2016-09-21 Impact factor: 6.167