Contemporary consensus holds that binocular rivalry (BR) is shaped by activity in multiple structures located at different levels of the human visual hierarchy (Blake & Logothetis,
2002; Haynes, Deichmann, & Rees,
2005; Lee & Blake,
1999; Tong & Engel,
2001; Watson, Pearson, & Clifford,
2004; Wunderlich, Schneider, & Kastner,
2005). Evidence for this includes findings from human brain imaging and monkey electrophysiology, which have implicated both high- (Leopold & Logothetis,
1996; Logothetis & Schall,
1989) and low- (Haynes et al.,
2005; Polonsky, Blake, & Heeger,
2000; Tong & Engel,
2001; Wilson, Blake, & Lee,
2001) level structures as being integral to BR.
There is also behavioral evidence suggesting the involvement of multiple mechanisms. For instance, if simple conflicting images, like gratings, are too large they tend not to dominate perception exclusively. Instead, patches of both rival images are seen (Blake, O'Shea, & Mueller,
1992). More complex images, like human faces, are more resistant to such effects (Alais & Melcher,
2007).
One method that has proven informative in this context involves triggering a change of perceptual dominance via a sudden focal contrast increment within a suppressed radial grating. The contrast increment instigates an almost instantaneous perceptual dominance change at the locus of the contrast increment (Knapen, van Ee, & Blake,
2007; Wilson et al.,
2001; see also Blake, Westendorf, & Overton,
1980). Changes then sweep gradually away from the position of the contrast increment, often circling the stimulus. These perceptual changes have been linked to sweeps of activity that can be traced through V1 via fMRI (Lee, Blake, & Heeger,
2005,
2007; Wilson et al.,
2001).
These data tie V1 activity to the spread of perceptual dominance through simple radial gratings. Thus far this method has only been employed using simple radial gratings. Given the physiological and behavioral evidence suggesting a link between perceptual dominance of more complex images and higher level brain structures, we decided to assess how triggered dominance changes would spread through these types of image.