Spatial and temporal parameters of motion detection in the peripheral visual field.

We present evidence that motion detectors in the peripheral visual field react to spatiotemporal structure in moving spatial white-noise patterns in a qualitatively similar fashion to those located near the center of gaze. Reichardt-type correlator mechanisms provide a simple theoretical framework in which all observed phenomena can be discussed. Two basic parameters of the correlator model are the time lag and the span. We have devised paradigms in which these parameters may be measured as a function of velocity and position in the visual field. Our results indicate that these parameters are primarily a function of the magnitude of the velocity (the span increasing and the lag decreasing as the velocity is increased) rather than of the retinal eccentricity. In another experiment, we determined the spatial resolution for apparent segregation of the visual image that is due to differential motion of detail in stationary rectangular gratings in which the pixels moved one way in the even bars and the other way in the odd bars. The limit of resolution occurs when the pixels traverse a bar of the grating in a given time, irrespective of the velocity or the retinal eccentricity. For higher velocities, the resolution is uniform over the entire visual field. For slower motion, the region of uniform (and relatively high) resolution shrinks to a region around the center of gaze. Resolution for segregation due to differential movement is at least 10 times worse than typical contrast-grating acuity.