Psychophysical evidence for sustained and transient detectors in human vision

Abstract

SUMMARY1. The sensitivity to temporally modulated sinusoidal gratings was determined. Two thresholds could be distinguished for the modulated gratings: the contrast at which flicker could be perceived and the contrast at which the spatial structure became distinct.2. The flicker detection thresholds and pattern recognition threshold varied independently as functions of the spatial and temporal frequencies, suggesting that the two thresholds represent the activity of two independent systems of channels.3. The channels detecting flicker prefer low and medium spatial frequencies. They have a pronounced decline in sensitivity at low temporal frequencies of sinusoidal modulation. They respond twice as well to gratings whose phase is alternated repetitively as to gratings turned on and off at the same rate.4. The channels responsible for the discrimination of spatial structure are most responsive at high and medium spatial frequencies. There is no decline in sensitivity at low temporal frequencies. These channels respond equally well to alternating and on/off gratings up to about 8 Hz.5. The temporal properties as revealed with sinusoidal modulation, suggest that the flicker-detecting channels would give transient responses to prolonged presentation of stimuli: the channels responsible for analyzing the spatial structure would give sustained responses. The responses of the two types of channel to alternating and on/off gratings confirm this suggestion.

Perceived rate of movement depends on contrast

“…The results reported in this paper could also be the The experimental data suggest that there cannot be consequence of a dependence of spatial frequency an exact correspondence between the two channels upon contrast. Georgeson (1980) has reported large described here and the pattern and movement chanincreases in the perceived spatial frequency of stationnels described by Kulikowski and Tolhurst (1973) and ary gratings when their contrast was decreased. In others.…”

“…Kulikowski and Tolhurst (1973) have reported that fast-moving gratings of low spatial frequency are seen to flicker at detection threshold whereas slowly moving gratings of high spatial frequency appear to be stationary at detection threshold.…”

On inhibition between spatial frequency channels: Adaptation to complex gratings

“…Tolhurst (1973) showed that the visibility of a stationary grating of 1.5 c/deg, which was presumably detected by shape-channels, was strongly reduced by an adapting grating moving at 5 Hz. Also, Kulikowski and Tolhurst (1973) showed that gratings of 0.8 and l() c/deg strongly affected the shape channels when the gratings flickered in counterphase in the range from 0 to 7 Hz. Thus, the observation that a stationary third-harmonic grating is a potent adapting pattern in the presence of a moving or noisy first-harmonic pattern is not readily explained by postulating that stationary and moving patterns adapt different types of channels, for the moving patterns presumably stimulate strongly the shape-channels as well as the movement-channels.…”

The Interaction Between Vision and Eye Movements

“…During pursuit, the eyes have to react mainly to small changes in stimulus speed. It is well established that there are two temporal channels for motion perception (Gegenfurtner & Hawken, 1996;Kulikowski & Tolhurst, 1973;Thompson, 1983; van der Smagt, . Pursuit improves chromatic contrast sensitivity.…”