title: The beneficial effects of subthalamic nucleus stimulation on manipulative finger force control in Parkinson's disease.
abstract: We investigated the differential effects of levodopa medication and STN stimulation on finger force control in Parkinson subjects grasping to lift an object and performing vertical point-to-point movements of a hand-held object. The experiments were conducted in four treatment conditions: off-drug/off-stimulation, off-drug/on-stimulation, on-drug/off-stimulation and on-drug/on-stimulation. We found that the bradykinesia in Parkinsonian subjects improved by both levodopa medication and STN stimulation. As compared to healthy subjects, excessive grip force was observed in all Parkinson subjects, regardless of the treatment condition. This force excess was most pronounced in the on-drug condition and ameliorated by STN stimulation. We observed reliable correlations between the amount of force overflow and the severity of levodopa-induced dyskinesias in the on-drug condition. Despite some similarities regarding therapeutic effects on bradykinesia, our findings contrast with earlier observations with respect to the differential effects of levodopa and STN stimulation on the scaling of fingertip forces in Parkinson's disease. While levodopa causes an overshoot of fingertip forces, STN stimulation appears to be sufficient to alleviate, but not normalise the force excess. STN stimulation enables Parkinson subjects to scale grip force more accurately to the loads arising from voluntary manipulation of hand-held objects.
authors.affiliation: Sobell Department of Motor Neuroscience and Movements Disorders, Institute of Neurology, University of London, London, UK. Dr.Dennis.Nowak@gmx.de
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Nowak
authors.forename: Helge
authors.initials: H
authors.lastname: Topka
authors.forename: Stephen
authors.initials: S
authors.lastname: Tisch
authors.forename: Marwan
authors.initials: M
authors.lastname: Hariz
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000978:Antiparkinson Agents / Q000627:therapeutic use; D046690:Deep Brain Stimulation / Q000379:methods*; D005260:Female; D005385:Fingers / Q000502:physiology / Q000528:radiation effects; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D010300:Parkinson Disease / Q000628:therapy*; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D020531:Subthalamic Nucleus / Q000528:radiation effects*; D014891:Weight Lifting / Q000502:physiology
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa