title: Dopamine dependency of cognitive switching and response repetition effects in Parkinson's patients.
abstract: A group of people with Parkinson's disease and a group of matched controls were tested on a task involving a switch between perceptual dimensions. Patients were tested both 'on' and 'off' their normal medication cycles. Stimuli appeared in pairs for each trial, with each stimulus consisting of a color and a shape. One dimension of color and one of shape were mapped to each of two response keys. A cue was presented concurrently with each stimulus to indicate whether to respond on the basis of color or shape, following procedures developed by Hayes et al. [Hayes, A.E., Davidson, M.C., Keele, S.W., and Rafal, R.D. (1998). Toward a functional analysis of the basal ganglia. Journal of Cognitive Neuroscience, 10, 178-198]. Replicating previous literature, abnormally large switch costs were observed in patients who were off their normal medication cycles. A novel finding was that patients in the 'on' state demonstrated a slight reversal of switch costs. Also novel, reaction time (RT) costs associated with switching between response keys, and interactions between response switching and task switching were influenced predominantly by on-off dopamine manipulations. It is concluded that abnormal task switching costs and response repetition effects likely reflect impairments of activation and inhibition, and both effects are dopamine-dependent.
authors.affiliation: Center for Neuroscience, University of California, Davis, USA.
authors.forename: Sheryl K
authors.initials: SK
authors.lastname: Shook
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Franz
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Higginson
authors.forename: Vicki L
authors.initials: VL
authors.lastname: Wheelock
authors.forename: Karen A
authors.initials: KA
authors.lastname: Sigvardt
mesh_terms: D016022:Case-Control Studies; D003071:Cognition / Q000187:drug effects* / Q000502:physiology; D004193:Discrimination Learning / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism*; D015259:Dopamine Agents / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology*; D010775:Photic Stimulation / Q000379:methods; D011340:Problem Solving / Q000187:drug effects* / Q000502:physiology; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects
chemical_list: D015259:Dopamine Agents; D004298:Dopamine