Abstract
Adaptation to a spatially uniform field that increases or decreases in luminance over time yields a “ramp aftereffect”, whereby a steady, uniform luminance appears to dim or brighten, and an appropriate non-uniform test field appears to move. We measured the duration of this aftereffect of adaptation to ascending and descending luminance for a wide range of temporal frequencies and luminance amplitudes. Three types of luminance ramp profiles were used: linear, logarithmic, and exponential. The duration of the motion aftereffect increased as amplitude increased, regardless of the frequency, slope, or ramp profile of the adapting pattern. At low luminance, this result held for ascending luminance adaptation, but the duration of the aftereffect was significantly reduced for descending luminance adaptation. This reduction in the duration of the aftereffect at low luminance is consistent with differential recruitment of temporally tuned cells of the ON and OFF pathways, but the relative independence of the effect from temporal frequency is not.
Highlights
It is well known that the visual system adjusts its sensitivity to the prevailing level of illumination.Adaptation does not occur instantly; moving from a dark environment to a light one or vice versa requires a short period of time before the visual system adjusts to seeing at the new level of illumination.These processes are known as light and dark adaptation, respectively
The results indicate that as the amplitude of the adapting ramp increased, the duration of the aftereffect increased for all temporal frequencies tested (Figure 3)
In order to investigate the effect of luminance level and frequency, we averaged across the adapting amplitudes for each participant to give one duration value for low luminance and one for high luminance at each frequency
Summary
It is well known that the visual system adjusts its sensitivity to the prevailing level of illumination. Contrast adaptation of cells in Anstis and Harris’s finding that the receptive field size associated with these aftereffects is very large [5] (over 20 times the diameter of the cells underlying acuity) is not compatible with any known subcortical or early cortical neurons. Their findings indicated that receptive field size radius (r) underlying the aftereffect increased with eccentricity (e) such that r = 6.17e – 0.51, whereas primate magnocellular receptive field radii are estimated the visual cortex is well established, contrast adaptation in pre-cortical cells remained elusive until relatively recently. We measured the aftereffect duration (appearance of motion on a test ramp) for a range of adapting amplitudes and gradients (Experiment 1) and for linear, logarithmic, and exponential ramps (Experiment 2)
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