Local channel structure of sustained peripheral vision

Abstract

A new evaluation of the local structure of sustained spatial channels with local stimuli in peripheral retina employs the masking sensitivity approach to minimize analytic assumptions. The stimuli were designed to address predominantly the sustained response system at 5 deg eccentricity. Under these conditions, the lowest spatial-frequency channel peaked at about 2 cycle/deg, 4 times higher than previous estimates, with a bandwidth of 1.5-2 octaves. The highest spatialfrequency channel peaked at 5-6 cycle/deg with about a 1 octave bandwidth. The data are consistent with there being only one channel tuned between these extremes, although they do not exclude a more continuous channel structure. Our analysis shows that there are no sustained channels tuned below 2 cycle/deg but there may be channels above the highest-frequency channel measured if tested with more selective stimuli than employed in our study. For local sustained stimuli, human peripheral spatial processing therefore appears to be based a simpler channel structure than is often supposed.