Heeger DJ, Boynton GM, Demb JB, Seidemann E, & Newsome WT, Motion Opponency in Visual Cortex, Journal of Neuroscience, 19:7162-7174 1999.
Abstract: Perceptual studies suggest that visual motion perception is mediated by opponent mechanisms that correspond to mutually suppressive populations of neurons sensitive to motions in opposite directions. We tested for a neuronal correlate of motion opponency using functional magnetic resonance imaging to measure brain activity in human visual cortex. There was strong motion opponency in a secondary visual cortical area known as the human MT complex (MT+), but there was little evidence of motion opponency in primary visual cortex (V1). To determine whether the level of opponency in human MT+ and monkey MT are comparable, a variant of these experiments was performed using multi-unit electrophysiological recording in areas MT and MST of the macaque monkey brain. While there was substantial variability in the degree of opponency between recording sites, the monkey and human data were qualitatively similar on average. These results provide further evidence that: 1) direction selective signals underlie human MT+ responses, 2) neuronal signals in human MT+ support visual motion perception, 3) human MT+ may be homologous to macaque monkey MT along with adjacent motion sensitive brain areas, and 4) that fMRI measurements are correlated with average spiking activity.