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Preserved gain control for luminance contrast during binocular rivalry suppression
Katsumi Watanabe1, Young Paik, Randolph Blake
1Visual Cognition Group, Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan. katsumi.watanabe@aist.go.jp
Vision Research
|October 12, 2004
Summary
Binocular rivalry increases contrast detection thresholds when stimuli are suppressed. However, the underlying contrast gain control mechanism operates similarly whether the pedestal is perceived or not, suggesting perception is not required.
Area of Science:
- Visual perception
- Neuroscience
- Psychophysics
Background:
- Binocular rivalry alters visual perception, notably elevating contrast increment thresholds for suppressed stimuli.
- Contrast increment thresholds are influenced by pedestal contrast, exhibiting a sigmoidal non-linearity indicative of gain control.
Purpose of the Study:
- To investigate how the contrast gain control mechanism functions during binocular rivalry, specifically examining its operation with and without conscious perception of a pedestal mask.
- To compare threshold versus contrast (TvC) functions during dominance and suppression phases of binocular rivalry.
Main Methods:
- Subjects viewed dichoptic stimuli (a steady grating pedestal and a radial checkerboard).
- Contrast increment thresholds for a transient stimulus were measured using a staircase method during dominance and suppression.
- Threshold versus contrast (TvC) functions were generated across various pedestal contrasts.
Main Results:
- Contrast increment thresholds were significantly higher during suppression compared to dominance.
- The rising slopes of the TvC functions did not differ between dominance and suppression, indicating a constant upward shift.
- A control experiment confirmed that TvC functions during dominance matched those during monocular viewing (non-rivalry).
Conclusions:
- The contrast gain control mechanism for transient luminance increments operates similarly regardless of whether the pedestal stimulus is consciously perceived.
- Binocular rivalry elevates detection thresholds through a mechanism that does not depend on the phenomenal experience of the pedestal contrast.