ENCODING DEFICITS IN UNTREATED PARKINSONS-DISEASE

Short-term memory deficits are prominent in untreated Parkinson's Disease (PD) and speed of central processing is known to be abnormal. To investigate the relationship between these findings, a modification of the Brown-Peterson paradigm was given to newly diagnosed, untreated patients and healthy control subjects (HCS). The PD patients were impaired under conditions of long stimulus exposure but not when study time was short. Although patients displayed deficits in immediate recall, they were more impaired at longer test delays. They achieved fewer encoding operations per unit time, resulting in a divergence of group performance with increasing duration of stimulus exposure. Performance in the PD group did not associate with motor disability, disease duration or rating of depression. These results are discussed in terms of a unifying reduced central processing deficit that is evident in PD but is independent of physical symptoms.