Assessing cognitive impairment in Parkinson's disease: a comparison of two tower tasks.

This study examined whether two tower tasks-the Cambridge Automated Neuropsychological Test Battery "Stockings of Cambridge" (CANTAB-TOL) and the Delis-Kaplan Executive Function System (D-KEFS-TOH), are interchangeable for detecting cognitive deficits in Parkinson's disease (PD) patients. Forty PD patients who met the criteria for this study were assessed with both tasks. The relative contribution of working memory and inhibition was also examined. Relative to controls, PD patients were impaired on the CANTAB-TOL but not the D-KEFS-TOH. Regression analysis which showed that whereas performance on the CANTAB-TOL task was dependent on inhibition and spatial working memory, performance on the D-KEFS-TOH was dependent on spatial working memory only. Only 7% to 24% of the variance between the two tasks was shared. These findings suggest that these tower tasks from two well-established neuropsychological test batteries are not interchangeable.