Reliance on external cues for movement initiation in Parkinson's disease: Evidence from movement-related potentials

• Published in: Brain (London, England : 1878) Vol. 121; no. 1; pp. 167 - 177
• Main Authors: PRAAMSTRA, P, STEGEMAN, D. F, COOLS, A. R, HORSTINK, M. W. I. M
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 1998; Oxford Publishing Limited (England)
• Subjects: Aged; Biological and medical sciences; Contingent Negative Variation - physiology; Cues; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Evoked Potentials - physiology; Evoked Potentials, Visual - physiology; Female; Humans; Male; Medical sciences; Middle Aged; Movement - physiology; Neurology; Parkinson Disease - physiopathology; Photic Stimulation; Reaction Time - physiology; Reference Values; Human; Motion; Nervous system diseases; Pathophysiology; Parkinson disease; Electroencephalography; Potential; Cerebral disorder; Electrodiagnosis; Motor cortex; Central nervous system disease; Degenerative disease; Contingent negative variation; Extrapyramidal syndrome
• ISSN: 0006-8950; 1460-2156; 1460-2156
• DOI: 10.1093/brain/121.1.167

The aim of this study was to investigate the neurophysiological mechanisms underlying Parkinson's disease patients' increased reliance on external cues for the initiation of movement. Lateralized movement-related cortical potentials were recorded in a noise-compatibility task with seven patients and seven age-matched control subjects. In this two-choice task, visual stimuli containing incompatible target and distractor elements, which simultaneously instructed for responses from both hands, initially caused activation of the motor cortex controlling the wrong response hand. The incorrect response activation was of higher amplitude in patients than in control subjects, causing a longer response delay relative to response times when target and distractors instructed the same hand. In addition, hand-specific motor cortex activation started earlier in patients than in control subjects. These results indicate that visual stimuli exerted an earlier and stronger influence on movement initiation in patients than in control subjects. We hypothesize that information from sensory stimuli relevant for the generation of a response can have rapid access to motor structures in Parkinson's disease patients, thereby facilitating the initiation of movement. The findings may reflect a compensatory mechanism, but could also be related to excitability changes in the motor cortex intrinsic to the pathophysiology of Parkinson's disease.