Human visual areas invariant to eye movements during natural vision
53.534, Tuesday, May 14, 8:30 am - 12:30 pm, Vista Ballroom
Shinji Nishimoto1, Alexander Huth1, Natalia Bilenko1, Jack Gallant1,2,3; 1University of California, Berkeley, Helen Wills Neuroscience Institute, 2University of California, Berkeley, Program in Bioengineering, 3University of California, Berkeley, Department of Psychology
During natural vision humans perceive a stable visual world even though they make frequent, rapid eye movements. For this reason, it is believed that the human visual system must contain representations of the visual world that are invariant to eye movements. To investigate this issue we used functional magnetic resonance imaging (fMRI) to record blood-oxygen level dependent (BOLD) signals evoked by natural movies from 5 human subjects under two conditions. In the first condition subjects were required to fixate steadily. In the second condition subjects were allowed to freely make voluntary eye movements. Identical natural movie stimuli were presented in both conditions and were repeated multiple times. If a brain area is invariant to eye movements, then responses during fixation will be similar to those observed during free viewing. If a brain area is sensitive to eye movements, then responses will be different between two conditions. The overall similarity between responses in the two conditions will also be limited by the amount of non-visual response modulation (i.e., signal-to-noise ratio). To identify areas that are invariant to eye movements, for each cortical voxel we first calculated response similarity across repeats within the fixation condition. Next we calculated response similarity across repeats but between the fixation and free viewing conditions. The ratio of these measures reveals which brain areas are invariant to eye movements. We found that voxels located in early visual areas such as V1, V2 and V3 are strongly affected by eye movements. In contrast, voxels in ventral temporal areas including fusiform face area (FFA) and extrastriate body area (EBA) are only weakly affected by eye movements. These results suggest that the ventral temporal visual areas contain a stable representation of the visual world that is invariant to eye movements made during natural vision.