Peripheral temporal frequency channels code frequency and speed inaccurately but allow accurate discrimination

Abstract

Perceived temporal frequency is vastly underestimated in the peripheral visual field, as all temporal frequencies above 10 Hz are perceived as flickering at 10 Hz even after scaling for acuity. Varying the contrast and spatial frequency of the peripheral pattern four-fold have negligible effects on the perceived flicker rate. Speed and auditory matching experiments also support this finding. Despite the saturation of perceived temporal frequency, frequency discrimination beyond 10 Hz was as accurate as in the fovea. By using a temporal masking paradigm, we obtained threshold elevation data that could be accounted for by three overlapping, broadly tuned temporal channels peaking at 5.5, 12 and 22 Hz. Based on these temporal frequency channels, we proposed that the visual system uses a line-element scheme for mediating temporal frequency discrimination, but adopts a weighted-average method for determining perceived temporal frequency. In the peripheral visual field, the weight assigned to the highest temporal channel is much larger than those assigned to the lower frequency channels.