Abstract
Patients with Parkinson’s disease and focal dystonia have difficulty in generating and preventing movement. Reaction time (RT) and stop signal reaction time (SSRT) measure the speed to initiate and stop a movement respectively. We developed a portable device to assess RT and SSRT. This incorporated a novel analysis to measure SSRT more efficiently (optimal combination SSRT, ocSSRT). After validation ocSSRT was measured in Parkinson’s disease patients without dyskinesia (PD), cervical dystonia (CD) and writer’s cramp. We also assessed how ocSSRT responded to L-dopa in PD patients and botulinum toxin injections in CD patients. Participants were instructed to release a button following a green LED flash on the device. On 25% of trials, a red LED flashed 5–195 ms after the green LED; participations were instructed to abort the button release on these trials. ocSSRT and RT were significantly prolonged in patients with Parkinson’s disease and focal dystonia (one-way ANOVA p < 0.001). Administration of L-dopa significantly improved ocSSRT and RT in PD patients (p < 0.001). Administration of botulinum toxin significantly improved ocSSRT, but not RT, in CD patients (p < 0.05). ocSSRT is an easily-administered bedside neuro-physiological tool; significantly prolonged ocSSRT is associated with PD and focal dystonia.
Highlights
Patients with Parkinson’s disease and focal dystonia have difficulty in generating and preventing movement
Motor response inhibition has been previously reported to be deficient in patients with patients without dyskinesia (PD), focal hand dystonia and L-dopa induced dyskinesia compared to controls without neurological disorders[2,3,16,17]
We first compared the results of measuring stop signal reaction time (SSRT) using our new statistical approach with the more conventional procedure of averaging estimates made from trials with different stop signal delays
Summary
Patients with Parkinson’s disease and focal dystonia have difficulty in generating and preventing movement. SSRT was reported to be uncorrelated with the go www.nature.com/scientificreports signal reaction time in PD patients[2]. This suggests that the paradigm may measure stopping independently of any coincident bradykinesia. Motor response inhibition has been previously reported to be deficient in patients with PD, focal hand dystonia and L-dopa induced dyskinesia compared to controls without neurological disorders[2,3,16,17]. We first introduce a new method to measure SSRT using portable equipment and an improved analytical approach After validating this in healthy subjects, we apply it to both PD and focal dystonia patients. Differences between patients and healthy controls were sufficiently robust that measurement of SSRT may be of use in pre-screening for movement disorders
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