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Contrast sensitivity for oriented patterns in 1/f noise: contrast response and the horizontal effect.
Andrew M Haun1, Edward A Essock
1Department of Psychological and Brain Sciences, University of Louisville, Louisville, KY, USA. andrew.haun@schepens.harvard.edu
Journal of Vision
|October 2, 2010
Summary
Visual perception exhibits a "horizontal effect," where detecting oriented stimuli is harder for horizontal orientations. This study reveals this effect is strongest at 8 cycles per degree, explained by anisotropic contrast gain control.
Area of Science:
- Vision science
- Psychophysics
- Computational neuroscience
Background:
- Observers show orientation-dependent thresholds when detecting stimuli in 1/f spatial noise.
- This phenomenon, known as the "horizontal effect," demonstrates lowest thresholds for oblique orientations and highest for horizontal ones.
Purpose of the Study:
- To identify specific spatial frequencies contributing to the horizontal effect.
- To investigate the underlying mechanisms of anisotropic performance in contrast detection.
Main Methods:
- Measured contrast detection thresholds for oriented broadband stimuli against 1/f noise backgrounds.
- Analyzed spatial frequency content of stimuli and observer performance.
- Determined threshold-versus-contrast (TvC) functions using pedestal and broadband noise masks.
Main Results:
- Contrast thresholds were lowest for stimuli around 8 cycles per degree (cpd).
- A significant horizontal effect was observed at 8 cpd, mirroring broadband masking anisotropies.
- The magnitude of the horizontal effect diminished at spatial frequencies below and above 8 cpd.
Conclusions:
- The horizontal effect in oriented noise is most pronounced at approximately 8 cpd.
- Anisotropic contrast gain control processes best explain the observed threshold patterns for oriented noise and broadband content.
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