Abstract
Purpose. Disparity selectivity for motion stimuli is well established in the MT area of monkey cortex (deAngelis & Newsome, 1999, J Neurosci). Activation by disparate moving stimuli has also been reported in the human brain by fMRI techniques (Rutschmann et al., 2000, Exp Brain Res) in the dorsolateral occipital cortex, but not the motion area V5. We investigated this discrepancy in an fMRI study of long-range disparate apparent motion.
Methods. BOLD responses were collected on a GE Signa 3T scanner in 22 near-coronal slices spanning the posterior half of the brain. The test-null stimuli were alternated for 9s each in 8 blocks, totaling 144 s plus a fixation period. The stimuli were presented as regular-dot autostereograms, with lateral motion at 1 Hz and disparity present above and below a static row of nondisparate fixation dots. The test stimuli thus had disparity, depth and 3D form, but were equated with the nulls in both motion and kinetic borders.
Results. Regions on both the anterior and posterior banks of the occipito-temporal sulcus responded strongly to apparent motion versus static dots, and were identified as the human homologs of monkey MT and MST motion areas. Neither early retinotopic areas nor these motion areas were selective for disparate versus flat motion, but such disparity/depth selectivity was observed in four other localized areas: a lateral occipital area corresponding to LO, a ventromedial area in the anterior calcarine sulcus (non-retinotopic for our stimuli), a temporal lobe area anterior to the MST homolog, and parietal area near the temporo-occipito-parietal junction.
Conclusion. Motion-based disparity information activates a distributed network of focal areas in human cortex involved in the perception of depth structure and spatial form. The ventromedial depth area lies between retinotopic V1 and the parahippocampal place area (Epstein & Kanwisher, 1998, Nature), suggesting a role in space integration.