Abstract
In this event-related fMRI study, we compared the networks that become active during the delay before a saccade to a remembered target with those that become active during the delay before a pointing movement to the same target. Previous work showed that saccade-and-pointing areas are lateral to areas active during pointing but not saccades in both premotor and parietal cortex. The purpose of the present study was to examine whether such organization is evident in networks with delay-period activity. Subjects held in mind the location of a flashed cue for 9 seconds and moved their eye or finger to the remembered location once a central cue was extinguished. The color of the central cue instructed a: 1) pro-saccade; 2) anti-saccade; 3) pro-pointing; or 4) anti-pointing trial. Regression analysis revealed 7 areas that were active during both delay and control periods or only during delay periods. Laterally in the parietal cortex, the anterior and the middle inferior parietal areas were active during all delay periods. More medially, the caudal and middle superior parietal areas were active only during the pointing delays. Laterally in the premotor cortex, the ventral premotor area and the frontal eye fields were active during the saccade and pointing delay periods. More medially, the presupplementary motor area was active only during the pointing delays. These data support the idea that areas with delay activity for saccades are active for pointing delays and lateral to areas active during pointing but not saccade delays.
Research supported by the Canadian Institutes of Health Research.