title: Motivational modulation of bradykinesia in Parkinson's disease off and on dopaminergic medication.
abstract: Motivational influence on bradykinesia in Parkinson's disease may be observed in situations of emotional and physical stress, a phenomenon known as paradoxical kinesis. However, little is known about motivational modulation of movement speed beyond these extreme circumstances. In particular, it is not known if motivational factors affect movement speed by improving movement preparation/initiation or execution (or both) and how this effect relates to the patients' medication state. In the present study, we tested if provision of motivational incentive through monetary reward would speed-up movement initiation and/or execution in Parkinson's disease patients and if this effect depended on dopaminergic medication. We studied the effect of monetary incentive on simple reaction time in 11 Parkinson's disease patients both "off" and "on" dopaminergic medication and in 11 healthy participants. The simple reaction time task was performed across unrewarded and rewarded blocks. The initiation time and movement time were quantified separately. Anticipation errors and long responses were also recorded. The prospect of reward improved initiation times in Parkinson's disease patients both "off" and "on" dopaminergic medication, to a similar extent as in healthy participants. However, for "off" medication, this improvement was associated with increased frequency of anticipation errors, which were eliminated by dopamine replacement. Dopamine replacement had an additional, albeit small effect, on reward-related improvement of movement execution. Motivational strategies are helpful in overcoming bradykinesia in Parkinson's disease. Motivational factors may have a greater effect on bradykinesia when patients are "on" medication, as dopamine appears to be required for overcoming speed-accuracy trade-off and for improvement of movement execution. Thus, medication status should be an important consideration in movement rehabilitation programmes for patients with Parkinson's disease.
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, The National Hospital for Neurology and Neurosurgery, 33 Queen Square, London, WC1N 3BG, UK.
authors.forename: Maja
authors.initials: M
authors.lastname: Kojovic
authors.forename: Pablo
authors.initials: P
authors.lastname: Mir
authors.forename: Iris
authors.initials: I
authors.lastname: Trender-Gerhard
authors.forename: Susanne A
authors.initials: SA
authors.lastname: Schneider
authors.forename: Isabel
authors.initials: I
authors.lastname: Pareés
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Edwards
authors.forename: Kailash P
authors.initials: KP
authors.lastname: Bhatia
authors.forename: Marjan
authors.initials: M
authors.lastname: Jahanshahi
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D015259:Dopamine Agents / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D018476:Hypokinesia / Q000188:drug therapy / Q000209:etiology* / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D009042:Motivation / Q000187:drug effects*; D010300:Parkinson Disease / Q000150:complications* / Q000188:drug therapy / Q000523:psychology; D011930:Reaction Time / Q000187:drug effects; D013997:Time Factors
chemical_list: D015259:Dopamine Agents