Visuomotor integration is impaired in early stage Alzheimer's disease

When the sensory information guiding a reach movement is dissociated from the required motor output, humans must integrate rule-based information in order to reach accurately. Here, we examine the accuracy of movements requiring a visuomotor transformation in neurologically healthy elderly subjects and patients diagnosed with probable Alzheimer's disease. Participants made sliding finger movements over a clear touch-sensitive screen positioned in three spatial planes to displace a cursor from a central target to one of four peripheral targets viewed on a monitor. These spatial plane conditions were repeated under conditions where the direction of cursor motion was rotated 180° relative to the direction of hand motion. Significant main effects were observed between patient and control groups on reaction time and movement time measures. Also, significant increases in task completion errors were observed in the patient population. Further, performance was affected more by the visual feedback changes relative to the plane location changes. Notably, there were substantial performance deficits observed in the patient population, even those with minimal cognitive deficits. We suggest that the integration of eye and hand information may be impaired in these patients.