IMPLICIT AND EXPLICIT MEMORY IN PATIENTS WITH PARKINSONS-DISEASE WITHAND WITHOUT DEMENTIA

Objective: To study explicit and implicit memory processes in patients with Parkinson's disease. Design: Case-control design. All subjects w ere given a neuropsychological test battery, and the test scores were compared among the groups. Setting: Government-funded research facilit y. All subjects were examined as outpatients. Patients: We tested nond emented (n=13) and demented (n=5) patients with Parkinson's disease an d normal controls (n=12) matched for age, gender, and educational leve l. Main Outcome Measures: Memory for verbal and pictorial stimuli unde r both explicit and implicit retrieval conditions. Results: Both nonde mented and demented patients with Parkinson's disease exhibited impair ment on tests of explicit memory. Their impairment could be graded bas ed on the level of effort required by the task: impaired free recall i n nondemented patients and impaired free recall, cued recall, and reco gnition in demented patients. By contrast, neither group showed eviden ce of impairment on automatic (modality monitoring and word frequency estimation) or implicit (word and picture fragment identification) mem ory tasks. Correlation analyses did not support any association betwee n the effortful memory deficits and neurologic variables, mood, or per formance on executive function tests. Conclusions: Memory deficits in patients with Parkinson's disease primarily involve the conscious, eff ortful strategic aspects of searching long-term memory.