Cognition in Parkinson's disease

Studies of accentuated drop in cognitive functioning of Parkinson's disease patients mostly use global intelligence measures that have a masking effect on differential drop in specific cognitive abilities. The goal of this study was to investigate the possible differential drop in different types of cognitive tasks. Applied tests tapped fluid and crystallized intelligence, memory, and metacognition. A sample of 116 participants participated in the study. Half of the participants were diagnosed with Parkinson's disease (average duration of disease 6.5 years) and control group participants equaled them in age, sex, and education level. All participants were tested using Raven's Colored Progressive Matrices (CPM), Crichton Vocabulary Scale (CVS), memory subtests from Wechsler Adult Intelligence Scale (WAIS DS-F, WAIS DS-B), and Mini-mental Status Examination (MMSE). Participants, and in the case of clinical group their caregivers as well, were asked questions concerning their metamemory and metacognition. Parkinson's disease patients scored lower than control group on all instruments used but the difference was significant only on CPM (F[1,114]=19.14, p=0.001) and MMSE (F[1,110]=4.04, p=0.047). Patients with Parkisons' disease have greater cognitive damage in fluid intelligence than in crystallized intelligence. They seem to have relatively accurate metamemory and metacognition.