An anisotropy of orientation-tuned suppression that matches the anisotropy of typical natural scenes

Abstract

Broadband oriented-noise masks were used to assess the orientation properties of spatial-context suppression in 'general' viewing conditions (i.e., a fixated, large field of 'naturalistic' noise). Suppression was orientation-tuned with a Gaussian shape and bandwidth of 40 degrees that was consistent across test orientation (0 degrees, 45 degrees, 90 degrees, and 135 degrees). Strength of suppression was highly anisotropic following a "horizontal effect" pattern (strongest suppression at horizontal and least suppression at oblique test orientations). Next, the time course of anisotropic masking was investigated by varying stimulus onset asynchrony (SOA). A standard "oblique effect" anisotropy is observed at long SOAs but becomes a "horizontal effect" when a noise mask is present within approximately 50 ms of the test onset. The orientation-tuned masking appears to result from an anisotropic gain-control mechanism that pools the weighted responses to the broadband mask, resulting in a changeover from oblique effect to horizontal effect. In addition, the relative magnitude of suppression at the orientations tested corresponds to the relative magnitudes of the content of typical natural scenes at the same orientations. We suggest that this anisotropic suppression may serve to equalize the visual system's response across orientation when viewing typical natural scenes, 'discounting' the anisotropy of typical natural scene content.

Dominant Vertical Orientation Processing without Clustered Maps: Early Visual Brain Dynamics Imaged with Voltage-Sensitive Dye in the Pigeon Visual Wulst

“…Along this line, Essock et al (2009) proposed a suppressive normalization mechanism helping to discount the overrepresentation of orientation content (horizontal) in the environment, after the finding that horizontal orientations were most strongly suppressed (vs vertical and oblique ones) by prestimulus exposure to oriented broadband masks. Broadband stimuli are more naturalistic, and, under such conditions, humans showed least sensitivity toward horizontal orientations (horizontal effect) (Essock et al, 2003).…”

Psychophysical analysis of three separate anisotropic patterns in vision : putting visual reference frames in conflict to study the class 1 and 2 oblique effects and the horizontal effect.

“…There was no interaction between head tilt and orientation: Table 13) were analyzed. The data show us that the top-down cognition did not have an effect on the results as they are still "in-between" gravitational and retinal coordinates and do not shift (Essock, DeFord, Hansen & Sinai, 2003;Hansen & Essock, 2004;Essock, Haun & Kim 2009;Kim, Haun & Essock, 2010). It occurs with stimuli that are broadband, both in terms of in spatial frequency and orientation content, which I used in the matching task.…”

“…More specifically, there are two different weights in the proposed gain control model for this effect: one added to the semi-saturation constant that is greatest at horizontal and least at vertical, and one added to masking strength (when a mask is present) that is greatest for cardinals. Both of these lead to the most suppression occurring at horizontal orientations (Essock, Haun & Kim, 2009 Hebbian rules applied at synapses, focusing on temporal competition, to generate simple cell RFs (Bienenstock, Cooper & Munro, 1982). That is, the greater magnitude of response of a postsynaptic neuron due to the input of a presynaptic neuron, the more capable the presynaptic neuron becomes at exciting the postsynaptic neuron in the future.…”

“…The horizontal effect then, serves to whiten a natural scene by suppressing horizontal content the most and oblique input the least, which is a highly beneficial step in the coding process. This means that typical natural scene content is suppressed and less-prevalent content is made relatively more salient (Hansen & Essock, 2004;Haun, Hansen, & Essock, 2006;Essock et al, 2009;Kim, Haun, & Essock, 2010; see also Schwartz & Simoncelli, 2001;Wainwright, 1999).…”

“…The importance of patterncentric coordinates is in agreement with the theory that the horizontal effect serves to "whiten" a natural scene. Because the natural scenes contain most orientation content (Fourier power) at horizontal, second most at vertical, and least at oblique orientations, the horizontal effect normalizes a natural scene by suppressing horizontal content the most and oblique input the least, so that typical natural scene content is suppressed and less-prevalent content is made relatively more salient (Hansen & Essock, 2004;Haun, Hansen, & Essock, 2006;Essock et al, 2009;Kim, Haun, & Essock, 2010).…”