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Temporal studies with flashed gratings: Inferences about human transient and sustained channels

1977; Elsevier BV; Volume: 17; Issue: 7 Linguagem: Inglês

10.1016/0042-6989(77)90130-4

1878-5646

Bruno G. Breitmeyer, Leo Ganz,

Photoreceptor and optogenetics research

The temporal response properties of the human visual system to low and high spatial frequency gratings was investigated by two contrast detection threshold techniques. With the first technique the contrast threshold for detecting vertical sinusoidal gratings at spatial frequencies of 0.5, 2.8 and 16.0 c/deg was determined at exposure durations ranging from 20 to 400 msec. It was found that the critical duration, at and below which reciprocity between contrast and a nonunity power of duration holds, increased from roughly 60 to 200 msec as spatial frequency increased from 0.5 to 16.0 c/deg. The second technique involved subthreshold summation of two, 10 msec flashed presentations of either a 1.0 or 10.0 c/deg grating. The stimulus onset asynchrony (SOA) separating the onsets of the two pulses varied from 0 to 210 msec. The results revealed that the subthreshold interaction of the two flashes at high spatial frequencies can be characterized by monophasic sustained excitation and inhibition; at low spatial frequencies, however, this interaction can be characterized by a multiphasic oscillation of excitation and inhibition superimposed on a monophasic excitatory-inhibitory interaction. The findings are related to properties of transient and sustained channels assumed to exist in human vision.