Picture and motor sequencing in Parkinson's disease

A recent report found that the discrepancy between scaled scores on the Vocabulary and Picture Arrangement subtests of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) was much larger for patients with Parkinson's disease than for healthy controls or patients with Alzheimer's disease. On this basis, it was argued that Parkinson's disease causes a specific deficit in cognitive sequencing that occurs even when the memory and speed requirements of the task are minimal. However, other work indicated that Parkinson's disease patients are almost as severely impaired on other Performance subtests from the WAIS-R that do not require sequencing. In the present study, an extremely simple, untimed test of picture sequencing and a version of the Luria three-step test of motor sequencing were employed. Parkinson's disease patients were impaired on both tasks. The extent of their impairments on picture and motor sequencing were positively correlated, and the severity of deficits on both sequencing tests was related to global mental status and to performance on the Wisconsin Card Sorting Test, but not to neurologic measures of disease severity. However, the patients' performance on the picture sequencing test but not on the motor sequencing test was related to performance on Benton's Facial Recognition Test. These results demonstrate the existence of a generalized sequencing deficit in Parkinson's disease that appears dissociable from impairment in performing simple motor acts.