Binocular rivalry using luminance- and contrast-modulated stimuli
56.502, Tuesday, 20-May, 2:45 pm - 6:45 pm, Pavilion
Jan Skerswetat1, Monika A. Formankiewicz1, Sarah J. Waugh1; 1Anglia Vision Research, Department of Vision and Hearing Sciences, Anglia Ruskin University, Cambridge, U.K.
Binocular rivalry is competition that occurs when incompatible stimuli are presented to the two eyes. The percept changes over time and originates either exclusively from one eye or is a mixture of the two stimuli. The mixed percepts are thought to represent periods of partial binocular integration (Klink et al., 2010). The processing of contrast-modulated stimuli is thought to occur in higher and more binocular areas of visual cortex, than that of luminance-modulated stimuli (Wong et al., 2005). We investigated whether these proposed differences in processing loci are reflected in the characteristics of binocular rivalry. Binocular rivalry was investigated for luminance (L), luminance-modulated (LM) and contrast-modulated (CM) stimuli with sizes of 1, 2 and 4 deg and spatial frequencies of 4, 2 and 1 c/deg, respectively. Orthogonal sinusoidal gratings were presented dichoptically to the two eyes. Six participants with normal vision completed 72 trials, each lasting at least 120 seconds, in counterbalanced order. The task was to indicate whether the left, right or mixed stimulus was perceived. Visual exclusivity, i.e., the proportion of time when only the right or left grating was visible, was significantly greater for LM (52±5%) and L (51±5%) than CM (14±4%) stimuli (p<0.05) and decreased with increasing stimulus size (50±6%, 41±6% and 26±6% for 1, 2 and 4 degrees, respectively). The average duration for the mixed CM percept was longer (~60 sec) than the mixed LM (~5 sec) and mixed L (~4 sec) one, and than the exclusive percepts for all types of stimuli (~1, ~2, ~1 sec for L, LM and CM, respectively). The low level of visual exclusivity and long periods of mixed perception or ‘partial binocular integration’ for CM stimuli provide further evidence for the involvement of more binocular visual areas in the processing of CM than L/LM stimuli.