Cortical representation of inward and outward radial motion in man.
We have used positron emission tomography to investigate the cortical areas of the normal human brain involved in processing inward (Expansion) and outward (Contraction) radial motion simulated with an optic flow stimulus. The optical flow display was made out of dots moving radially away from or toward the center of the display monitor. In the Control condition, the dots' motion was randomized in order to remove any sensation of radial motion. In the Expansion condition, several loci of activation were observed: visual areas V2-V3 and the superior parietal lobule (BA 7), predominantly in the right hemisphere. In the Contraction condition activation sites were found in the same visual areas (V2 and V3) in the right hemisphere but the increase in rCBF in these regions was much lower than in the Expansion condition. BA 7 was activated in both hemispheres. When the motion component of the stimulus was isolated by subtracting the static condition from the incoherent motion condition, we obtained activations of areas V2, V3, and MT (putative V5). These results indicate that the detection of radial motion derived from an optic flow stimulus is mediated by structures forming the dorsal part of the visual cortical system and confirm that area MT is not specifically involved in flow analysis.
Ptito
M
M
Ecole d'Optométrie, Université de Montréal, Montréal, Quebec, Canada H3C 3J7.
Kupers
R
R
Faubert
J
J
Gjedde
A
A
D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000000981:diagnostic imaging*; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007699:Kinesthesis / Q000502:physiology*; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009778:Occipital Lobe / Q000000981:diagnostic imaging; D009903:Optical Illusions / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D010296:Parietal Lobe / Q000000981:diagnostic imaging; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D014055:Tomography, Emission-Computed; D014793:Visual Cortex / Q000000981:diagnostic imaging