Component Analysis of a Rhythmic Finger Tapping Task in Individuals With Senile Dementia of the Alzheimer Type and in Individuals With Parkinson's Disease

The present experiment examined different components of motor control that may be impaired in normal aging, senile dementia of the Alzheimer type (SDAT), and Parkinson's disease (PD). Specifically, A.M. Wing and A.B. Kristofferson's (1973) formal quantitative model of rhythmic finger tapping was used to obtain estimates of central timekeeping and response execution components of timing control. Subjects included young college students, healthy older adults, nondemented individuals with PD, and individuals with very mild and mild SDAT. Individuals with mild SDAT exhibited a breakdown in the central timekeeping mechanism but not in the execution of the response. Both very mild SDAT and PD individuals did not show any deficits in the two timing mechanisms relative to age-matched healthy controls. Finally, there was no effect of normal aging on timing control in this task. This study underscores the importance of examining issues of motor control in SDAT as a function of separate processing components and stages of disease progression.