Abstract
Bistable perception arises when a single stimulus provides two plausible, yet mutually exclusive perceptual interpretations from which the brain must select one. Examples include binocular rivalry (BR) and bistable structure from motion (SFM) cylinders. During intermittent presentation, stabilisation can occur; perception becomes ‘stuck’ such that the same interpretation (e.g. a rightward rotating cylinder) is seen on every presentation for up to several minutes. This regularization of perception based on prior experience has been termed “perceptual memory”. We investigate whether these memory effects spread across disparate visual locations, or are spatially specific, as reported by Chen & He (2004).
In separate sessions, observers viewed BR oriented gratings or SFM cylinders. Stimuli were presented alternately at fixation and at one of a number of eccentric locations. Thus, every second stimulus appeared at fixation, causing robust stabilization in that location. Importantly, with both BR and SFM stimuli, there were strong interactions between perception at fixation and perception at subsequent peripheral locations. In other words, perceptual stabilisation is not local, but spreads to other regions of the visual field. These perceptual interactions were not uniform across space, however, but gradually decreased as spatial separation between stimuli increased. Furthermore, by manipulating fixation position between successive presentations, we established that this spreading of perceptual memory occurs in a retinotopic frame of reference; perceptual memory is not re-mapped in response to saccades.
In summary, in stark contrast to previous findings, we found that the effects of perceptual memory do spread across the visual field; a perceptual decision at one retinal location biases the interpretation of similar stimuli at non-contiguous spatial locations. The retinotopic nature of this spread suggests that stabilisation is a low-level process mediated by facilitatory connections in low-level cortical areas.