Performance on the Clock Drawing Task Correlates with fMRI Response to a Visuospatial Task in Alzheimer's Disease

The clock drawing (CD) task involves visual integration skills associated with parietal lobe function. Seven mild Alzheimer's Disease (AD) patients and 11 healthy elderly controls (EC) underwent functional magnetic resonance imaging (fMRI) scanning while viewing a radial motion (RM) task. This RM task in EC activated the bilateral secondary visual cortex and parietal regions, whereas AD patients activated only the right-sided secondary visual cortex. The magnitude of the fMRI signal in the left superior parietal lobe was positively correlated with performance on the CD task in AD patients. These findings suggest that complex visuospatial processing impairments reflect the underlying AD neuropathology in parietal regions.