Abstract
Recent psychophysical studies have shown that attention can alter contrast sensitivities for temporally broadband stimuli such as flashed gratings. The present study examined the effect of attention on the contrast sensitivity for temporally narrowband stimuli with various temporal frequencies. Observers were asked to detect a drifting grating of 0–40 Hz presented gradually in the peripheral visual field with or without a concurrent letter identification task in the fovea. We found that removal of attention by the concurrent task reduced the contrast sensitivity for gratings with low temporal frequencies much more profoundly than for gratings with high temporal frequencies and for flashed gratings. The analysis revealed that the temporal contrast sensitivity function had a more band-pass shape with poor attention. Additional experiments showed that this was also true when the target was presented in various levels of luminance noise. These results suggest that regardless of the presence of external noise, attention extensively modulates visual sensitivity for sustained retinal inputs.
Highlights
Attention plays a central role for selecting behaviorally relevant information among enormous retinal inputs
The present results show that when the observers concentrate on a different cognitive task, contrast sensitivity is reduced by a large amount for peripheral gratings of low temporal frequencies but little for those of high temporal frequencies
The results are consistent with the previous findings that attention alters contrast sensitivity [6,7], and further demonstrates that the effect is profound for low temporal frequencies
Summary
Attention plays a central role for selecting behaviorally relevant information among enormous retinal inputs. An increasing number of studies have focused more on the computational mechanisms underlying these attentional facilitations, using simple measures such as detection threshold [4,5,6,7], discrimination sensitivity [8,9], and suprathreshold appearance [10]. This approach enables us to analyze the effect of attention more systematically in terms of the gain and selectivity of visual channels and makes it easier to relate the behavior to the attentional modulation of cortical responses [11]. It has been shown that the effect is almost independent of the spatial frequency; i. e., attention does not alter the shape of the spatial contrast sensitivity function [6]
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