Abstract
Purpose: Covert spatial attention benefits performance in many visual tasks. Endogenous (voluntary) and exogenous (involuntary) attention can have differential effects on performance. For example, in texture segmentation tasks, endogenous attention always improves performance whereas exogenous attention impairs performance near the fovea (high resolution) but improves performance in the periphery (low resolution). Furthermore, exogenous attention benefits performance at SFs higher than the target’s SF, whereas endogenous attention improves performance at SFs below and above the target’s SF. Here we investigate whether sensory tuning is differentially affected by exogenous and endogenous attention. Methods: The same six observers completed 15 experimental sessions of exogenous and of endogenous attention while detecting the presence of a vertical grating embedded in noise. Following a valid, neutral, or invalid cue, stimuli were presented at four peripheral locations (7° eccentricity). Whether a target was embedded in the noise was independently and randomly manipulated for each location. A response cue determined the test stimulus. The feature content of the noise was regressed with behavioral responses (reverse correlation) to derive tuning curves for each attentional cue and feature dimension (orientation and SF). Results: Both endogenous and exogenous covert attention improved performance at the attended location and impaired performance at the unattended locations, compared to the neutral condition. Both types of attention enhanced the gain of the target orientation and maintained tuning width. Endogenous attention enhanced the gain of SFs below and above the target’s SF, whereas exogenous attention shifted peak sensitivity to higher SFs and enhanced the gain of SFs higher than the target’s SF. Conclusions: Both types of covert attention modulate orientation similarly. However, endogenous attention flexibly enhances low and high SFs whereas exogenous attention inflexibly enhances higher SFs. These changes in sensory tuning can underlie the differential performance effects of endogenous and exogenous attention.