Abstract
Glass patterns (GPs) consist of randomly distributed dot pairs (dipoles) whose orientations are determined by specific geometric transforms. We assessed whether adaptation to stationary oriented translational GPs suppresses the activity of orientation selective detectors producing a tilt aftereffect (TAE). The results showed that adaptation to GPs produces a TAE similar to that reported in previous studies, though reduced in amplitude. This suggests the involvement of orientation selective mechanisms. We also measured the interocular transfer (IOT) of the GP-induced TAE and found an almost complete IOT, indicating the involvement of orientation selective and binocularly driven units. In additional experiments, we assessed the role of attention in TAE from GPs. The results showed that distraction during adaptation similarly modulates the TAE after adapting to both GPs and gratings. Moreover, in the case of GPs, distraction is likely to interfere with the adaptation process rather than with the spatial summation of local dipoles. We conclude that TAE from GPs possibly relies on visual processing levels in which the global orientation of GPs has been encoded by neurons that are mostly binocularly driven, orientation selective and whose adaptation-related neural activity is strongly modulated by attention.
Highlights
Glass patterns (GPs) consist of randomly distributed dot pairs whose orientations are determined by specific geometric transforms
The angular function observed by adapting to oriented translational GPs, reduced in magnitude, is similar to those reported when adapting to oriented gratings or lines[2,3,7,45,46], subjective contours[9,16,47,48], contours defined by orientation contrast[16] and adaptation to fast directional moving dots producing motion streaks[19]
The near-identical pattern of tuning implies that oriented translational GPs are likely to be encoded by the same orientation-selective neurons present in early visual cortical areas[31,32], thought to underlie the classic TAE2,17,41
Summary
Glass patterns (GPs) consist of randomly distributed dot pairs (dipoles) whose orientations are determined by specific geometric transforms. A computational model of the TAE outlined by Clifford et al.[2] showed that both direct and indirect TAE can be explained by means of the overlap of two adapting effects, which they refer to as centering and scaling The former inhibits the response of the neurons tuned to stimuli oriented in parallel to that of the adapting stimulus, causing a repulsion of the perceived test orientation. To date TAEs have been reported using a variety of visual stimuli including oriented gratings[5,9], single lines[1,8,15], oriented stimuli defined by subjective contours[16,17], texture edges defined by orientation contrast[16], bilateral symmetrical patterns[18] and orientation signals defined by fast moving dots (i.e., motion streaks[19]) Taken together these studies suggest that, depending on the adapting stimulus, the TAE may rely either on the striate cortex (V1) or on extrastriate areas (e.g., on V2 or higher extrastriate areas). This enhanced response to tangential orientations indicates sensitivity to curvature and global form as early as striate cortex
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