Influence of competing distractors on response selection in Huntington's disease and Parkinson's disease

Current theories of the basal ganglia suggest a functional role in filterin g stimuli that are competing for response selection. We hypothesised that d amage to the basal ganglia, as occurs in Huntington's disease (HD) and Park inson's disease (PD), may alter the effects of distractors on this filterin g process. Fourteen HD subjects, 16 PD subjects, and age-matched healthy co ntrols performed an ignored repetition test of negative priming. Negative p riming was defined as a significant time cost in responding to a target tha t shared features with the distractor from the previous trial. Results indi cated that whereas healthy controls and PD subjects showed normal negative priming, HD subjects failed to show negative priming. The results indicate that disruption to cells in the neostriatum, but not necessarily to cells i n the substantia nigra, may affect selective attention by altering the infl uence of distractor stimuli competing for action.