Volume 7, Number 5, Article 3, Pages 1-18 doi:10.1167/7.5.3 http://journalofvision.org/7/5/3/ ISSN 1534-7362
Illusory contrast-induced shifts in binocular visual direction bias saccadic eye movements toward the perceived target position
Julia A. Weiler
School of Optometry, University of California, Berkeley, CA, USA
[home] [e-mail]
James S. Maxwell
School of Optometry, University of California, Berkeley, CA, USA
[home] [e-mail]
Clifton M. Schor
School of Optometry, University of California, Berkeley, CA, USA
[home] [e-mail]
Abstract

The perceived binocular visual direction of a fused disparity stimulus with an interocular contrast difference is biased toward the direction signaled by the eye presented with the higher contrast image (J. S. Mansfield & G. E. Legge, 1996). Does the amplitude of binocular saccadic eye movements have a similar bias? We examined saccades to fused disparate Gabor patches with interocular contrast differences. The effect of these contrast differences on saccadic amplitudes was compared to the perceptual biases in binocular direction obtained in a vernier acuity task. Saccades to unequal contrast targets landed between the end points for equal contrast and monocular targets. For three of our eight subjects, the saccadic bias equaled the perceptual effect. For the other subjects, however, saccades were affected to a lesser extent. Three models for binocular combination were used to evaluate these responses: A maximum-likelihood model failed to predict our results, whereas a model with contrast-dependent weighting of direction estimates by two monocular channels and a gain control model of binocular contrast summation gave a better approximation to our data. Both models showed that for the perceptual system, the influence of the eye that was presented with the higher contrast image was more dominant in the binocular combination than expected from the stimulus contrast ratio. The oculomotor system, however, was close to following linear summation.

View full-text

History
Received October 19, 2006; published March 21, 2007
Citation
Weiler, J. A., Maxwell, J. S., & Schor, C. M. (2007). Illusory contrast-induced shifts in binocular visual direction bias saccadic eye movements toward the perceived target position. Journal of Vision, 7(5):3, 1-18, http://journalofvision.org/7/5/3/, doi:10.1167/7.5.3.
Keywords
saccades, visual direction, contrast, binocular combination
Downloads
156 Total; 0.324 /day (DemandFactor)
 
Search
for related articles by these authors
for papers that cite this paper
Get citation






jov