Abstract
Goal: The eccentricity effect refers to the phenomenon that performance worsens with increasing eccentricity (fovea to periphery). To understand the computational mechanism underlying the eccentricity effect, we investigated whether and how orientation and spatial frequency tuning functions differ between the fovea and periphery using reverse correlation. Methods: Observers detected a horizontal Gabor (present in half trials) embedded in noise, which was indicated by a response cue among distractors (noise only). To isolate and compare the sensory tuning functions at the fovea and isoeccentric cardinal locations (at 6° eccentricity), we estimated the perceptual sensitivity to different orientations and SFs using psychophysical reverse correlation, which has been widely used to probe the mechanisms underlying behavioral responses to noisy stimuli. Tuning functions were characterized by the gain (amplitude) and the width (at half maximum). Higher gain indicates higher sensitivity and narrower width indicates narrower tuning and higher selectivity. Results: Analyzing Gabor-absent trials yielded (a) a higher orientation gain and higher spatial frequency amplitude at the fovea than the periphery, and (b) a narrower tuning to the target orientation at the fovea than the periphery. Conclusion: Results suggest that the better visual performance at the fovea than the periphery may be explained by higher sensitivity and selectivity for the orientation relevant for target detection and higher sensitivity for its spatial frequency. These findings provide insight into the computations underlying the eccentricity effect and inform computational models.