Abstract
Eye blinks are commonly assumed to be detrimental for visual functions, as they momentarily block the input to the retina. However, they also modulate strongly the luminance flow entering the eye, and it has been argued that temporal changes in the retinal image play important roles in the establishment of spatial representations. Thus, the visual system could, in principle, benefit from these modulations. Here we examined whether the luminance transients resulting from eye blinks enhance visual sensitivity. In a forced-choice task, human observers (N=9) were asked to report the orientation (±45°) of a 3 cycle/degree grating displayed at full screen (21°×11.8°) for 2.5 s. Stimulus contrast was individually adjusted to yield ~80% correct responses. To minimize presentation transients, the stimulus slowly ramped up over a period of 1.5 s. We compared performance in trials in which subjects did and did not execute voluntary blinks. The proportion of correct responses was higher in the presence of blinks, leading to a small but significant increment that occurred despite the relatively long absence of retinal stimulation in the blink trials (~150 ms). Similar results were also obtained in a control experiment in which subjects did not blink, but blink transients were simulated by temporally modulating the luminance of the display. This sensitivity enhancement is consistent with the strong responses to blink transients exhibited by standard models of ganglion cells, which were exposed to reconstructions of the visual input signals experienced by the subjects in our experiments. These results support the proposal that luminance transients caused by eye blinks enhance visual sensitivity.