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Direct encoding of orientation variance in the visual system

Norman, L.J.; Heywood, C.A.; Kentridge, R.W.


C.A. Heywood


Our perception of regional irregularity, an example of which is orientation variance, seems effortless when we view two patches of texture that differ in this attribute. Little is understood, however, of how the visual system encodes a regional statistic like orientation variance, but there is some evidence to suggest that it is directly encoded by populations of neurons tuned broadly to high or low levels. The present study shows that selective adaptation to low or high levels of variance results in a perceptual aftereffect that shifts the perceived level of variance of a subsequently viewed texture in the direction away from that of the adapting stimulus (Experiments 1 and 2). Importantly, the effect is durable across changes in mean orientation, suggesting that the encoding of orientation variance is independent of global first moment orientation statistics (i.e., mean orientation). In Experiment 3 it was shown that the variance-specific aftereffect did not show signs of being encoded in a spatiotopic reference frame, similar to the equivalent aftereffect of adaptation to the first moment orientation statistic (the tilt aftereffect), which is represented in the primary visual cortex and exists only in retinotopic coordinates. Experiment 4 shows that a neuropsychological patient with damage to ventral areas of the cortex but spared intact early areas retains sensitivity to orientation variance. Together these results suggest that orientation variance is encoded directly by the visual system and possibly at an early cortical stage.


Norman, L., Heywood, C., & Kentridge, R. (2015). Direct encoding of orientation variance in the visual system. Journal of Vision, 15(4), 1-14.

Journal Article Type Article
Acceptance Date Mar 28, 2015
Online Publication Date Apr 29, 2015
Publication Date Apr 29, 2015
Deposit Date May 15, 2015
Journal Journal of Vision
Publisher Association for Research in Vision and Ophthalmology
Peer Reviewed Peer Reviewed
Volume 15
Issue 4
Article Number 3
Pages 1-14