Abstract
Introduction. In a texture segmentation task where performance peaks at mid-peripheral locations, the performance drop near the fovea is usually attributed to the spatial filters at the fovea being too small for the scale of the texture. Yeshurun and Carrasco (1998, 2000) found that attending to the target location improves performance where the resolution is too low (periphery) but impairs it where resolution is already too high (central locations) for the task. These results indicate that attention enhances spatial resolution. Goal. To investigate further the spatial properties underlying the central performance drop in texture segmentation, and to further characterize the attentional effect. For the first time, we combine selective adaptation and precue procedures. Method. In a 2AFC (identify target orientation: tilted to the left or tilted to the right) observers were presented with a precue that indicated either both target location and display onset (peripheral cue) or just display onset (neutral cue). The target patch appeared at varying eccentricities in a large texture pattern along the horizontal meridian. Observers adapted for 8 min to a display containing either a high- (8 cpd) or a low- (1 cpd) spatial frequency sinusoidal grating. Immediately after, they performed 250 trials of the texture segmentation task. The same adaptation pattern was presented for 1 sec before each trial, to ‘top-up’ and maintain the initial adaptation effect. Results and Conclusion. In the neutral condition, adapting to the 1-cpd grating produced similar functions for performance at the peripheral and at the central locations. However, adapting to the 8 cpd grating diminished the central performance drop. Furthermore, after adapting to the 8-cpd grating we found no attentional impairment at the central locations. The overall sensitivity of the attended region shifts towards higher spatial frequencies; but selective adaptation to high spatial frequencies precludes such a shift.
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YeshurunY.CarrascoM.(2000) The locus of attentional effects in texture segmentation. Nature Neuroscience, 3 (6) 622–627.