Functional MR imaging using a visually guided saccade paradigm for comparing activation patterns in patients with probable Alzheimer's disease and incognitively able elderly volunteers

BACKGROUND AND PURPOSE: Alzheimer's disease is associated with progressive visuospatial dysfunction, This study used functional MR (fMR) imaging with an eye movement paradigm to investigate differences in visuospatial cogniti on between patients with probable Alzheimer's disease (pAD) and cognitively able elderly volunteers. METHODS: Using established, although imperfect, clinical criteria, patients with pAD (n = 18) and cognitively able elderly volunteers (n = 10) were se lected for study. All patients underwent echo-planar fMR imaging at 1.5 T, The visually guided saccade paradigm consisted of alternating periods (30 s ) of central fixation and visually guided saccades to a target appearing ra ndomly along the horizontal meridian, Activation maps were derived using a voxel-wise t test, comparing the signal intensities between the two steady- state conditions. The activation patterns were characterized by Talairach c oordinates, activation volumes, and laterality ratios (LRs). RESULTS: Statistically significant differences existed between the activati on patterns of the patients with pAD and those of the volunteers. In contra st to the control group, a left-dominant parietal activation pattern and en hanced prefrontal cortical activation were observed in most patients with p AD. CONCLUSION: Within the limitations of the imperfect clinical standard of re ference, the reduction in right parietal activation producing the left-domi nant LR for the intraparietal sulcus may reflect the progressive dysfunctio n in spatial attention associated with Alzheimer's disease, considering the known parietal lobe involvement in this function and the disease. The high specificity of a positive intraparietal sulcal LR measured by fMR imaging may have a role in detecting and monitoring Alzheimer's disease.