MEMORY FUNCTIONING IN PARKINSON'S DISEASE: THE EFFECT OF AGE OF ONSET ON HIGH SPEED MEMORY SCANNING.

Abstract

A sample of 25 idiopathic Parkinson's disease subjects and 25 age and education matched elderly healthy control subjects were assessed for their speed of primary memory scanning speed using the Sternberg memory scanning paradigm. In addition, all patients were assessed for cognitive functioning as measured by the Mattis Dementia Rating Scale and the Wechsler Memory Scale. Significant differences were found between Parkinson's disease subjects and control subjects on speed of primary memory scanning, with the parkinsonian subjects performing significantly slower than the control subjects. Increased variability in the measure of memory scanning speed was noted for the parkinsonian subjects as compared to control subjects and different variables associated with increased cognitive disturbances in parkinsonian subjects were investigated as possible sources of this variability. It was found that the majority of variance could be accounted for by the parkinsonian subjects' age of symptom onset. Parkinsonian subjects who developed the disease later in life were significantly slower at primary memory scanning speed than were either parkinsonian subjects who developed the disease earlier in life, or than healthy control subjects. Cognitive variables measuring initiation and perseveration, construction and attention were found to be highly associated with increased primary memory scanning time. The relationship between these cognitive abilities and frontal lobe dysfunction is discussed. Also, the possible relationship between slowing of memory scanning and dopamine depletion is presented.