title: L-dopa impairs learning, but spares generalization, in Parkinson's disease.
abstract: In this study we examined the effect of dopaminergic modulation on learning and memory. Parkinson's patients were tested 'on' versus 'off' dopaminergic medication, using a two-phase learning and transfer task. We found that dopaminergic medication was associated with impaired learning of an incrementally acquired concurrent discrimination task, while patients withdrawn from dopaminergic medication performed as well as controls. In addition, we found a dissociation of the effect of medication within a single two-phase task: patients tested 'on' medication were not impaired at the ability to generalize based on learned information. The deficit among medicated patients appeared to be related specifically to the concurrent, incremental, feedback-based nature of the task: such a deficit was not found in a version of the task in which demands for concurrent error-processing learning were reduced. Taken together with a growing body of evidence emphasizing a role for midbrain dopamine in error-correcting, feedback-based learning processes, the present results suggest a framework for understanding previously conflicting results regarding the effect of medication on learning and memory in Parkinson's disease.
authors.affiliation: Department of Psychology, Stanford University, Jordan Hall, Bldg. 420, Stanford, CA 94305, USA. shohamy@psych.stanford.edu
authors.forename: Daphna
authors.initials: D
authors.lastname: Shohamy
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Myers
authors.forename: Kindiya D
authors.initials: KD
authors.lastname: Geghman
authors.forename: Jacob
authors.initials: J
authors.lastname: Sage
authors.forename: Mark A
authors.initials: MA
authors.lastname: Gluck
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D000978:Antiparkinson Agents / Q000009:adverse effects*; D016022:Case-Control Studies; D004192:Discrimination, Psychological / Q000187:drug effects; D005260:Female; D005793:Generalization, Psychological / Q000187:drug effects*; D006801:Humans; D007858:Learning / Q000187:drug effects*; D007859:Learning Disabilities / Q000139:chemically induced*; D007980:Levodopa / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000188:drug therapy
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa