Cognitive processes involved in delayed non-matching-to-sample performancein Parkinson's disease

Visual recognition memory was assessed in terms of delay duration, memory l oad and amount of interference(s) in non-demented patients with Parkinson's disease (PD) using an automated delayed non-matching-to-sample (DNMS) task with trial-unique stimuli. Special attention was focused on the different cognitive functions engaged by these patients in solving this recognition m emory task. Thirteen patients with PD, carefully selected according to thei r stable regimen and anticholinergic medication, were compared to 12 contro ls matched by age and educational level. Besides the DNMS task, a neuropsyc hological battery that included tasks carefully selected according to proce sses potentially required to perform the DNMS task (e.g. attention, executi ve functions, visual discrimination and motor speed) was administered to th e subjects. As compared with controls, patients with PD showed a deficit on most DNMS subscores, except those requiring the least cognitive load. The correlative analysis between the DNMS and other neuropsychological tasks su ggests involvement of long-term memory mainly in the DNMS performance for t he control group, contrasting with a major involvement of executive functio ns for the patients with PD. These data indicate that visual recognition me mory impairment in non-demented patients with PD is largely due to an execu tive dysfunction, notably in working memory. Several hypotheses are propose d concerning the neuronal substrates underlying the impairment on the visua l DNMS task in PD.