Abstract
When two identical visual discs move toward each other on a two-dimensional visual display, they can be perceived as either “streaming through” or “bouncing off” each other after their coincidence. Previous studies have observed a strong bias toward the streaming percept. Additionally, the incidence of the bouncing percept in this ambiguous display could be increased by various factors, such as a brief sound at the moment of coincidence and a momentary pause of the two discs. The streaming/bouncing bistable motion phenomenon has been studied intensively since its discovery. However, little is known regarding the neural basis underling the perceptual ambiguity in the classic version of the streaming/bouncing motion display. The present study investigated the neural basis of the perception disambiguating underling the processing of the streaming/bouncing bistable motion display using event-related potential (ERP) recordings. Surprisingly, the amplitude of frontal central P2 (220–260 ms) that was elicited by the moving discs ~200 ms before the coincidence of the two discs was observed to be predictive of subsequent streaming or bouncing percept. A larger P2 amplitude was observed for streaming percept than the bouncing percept. These findings suggest that the streaming/bouncing bistable perception may have been disambiguated unconsciously ~200 ms before the coincidence of the two discs.
Highlights
The human visual system often experiences unitary and stable perception by integrating relevant sensory information in the environment
A growing number of functional magnetic resonance imaging (fMRI) studies have demonstrated that the frontal and parietal cortex play a causal role in initiating perceptual reversals in bistable displays[37, 40,41,42,43], which indicates that high-level brain areas could reorganize ambiguous information within the visual cortex and eventually reverse our perceptual interpretations[1, 44, 45]
Consistent with the findings in previous behavioral studies that streaming percept dominates in the original visual streaming/bouncing motion display[3,4,5], the percentage of streaming responses in our study was significantly higher compared to the bouncing responses [streaming, 61.2 ± 3.6% of response required trials; bouncing, 38.8 ± 3.6% of response required trials; F(1, 17) = 9.58, p < 0.007, η2p = 0.36]
Summary
The human visual system often experiences unitary and stable perception by integrating relevant sensory information in the environment. Transcranial magnetic stimulation (TMS) to temporarily deactivate the posterior parietal cortex resulted in an attenuated magnitude of the sound’s effect on improving the bouncing percept[24] Combining these neuroscience studies, cross-modal integration between polysensory and unisensory brain cortices may underlie the effect of sound on reversing the perceptual dominance of the streaming/bouncing motion display. Despite numerous identified bounce-inducing factors, especially evidences based on neural mechanisms for the audiovisual bounce-inducing effect (ABE), the neural basis of disambiguating perception during the streaming/bouncing bistable perception processing in purely visual streaming/bouncing display remains unclear In other words, it is not understood how one percept (streaming or bouncing) overwhelms the other and eventually becomes a stable percept under an ambiguous context in a visual streaming/bouncing bistable display. The emerging brain model of bistable perception is a dynamic and highly interactive network between low-level (sensory) and high-level (frontal and parietal) brain regions
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