Pre-coincidence brain activity predicts the perceptual outcome of streaming/bouncing motion display

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.

Temporal dynamics of the flash‐induced bouncing effect

“…That is, two visual disks moved toward one another and then suddenly disappeared just before their coincidence, eliciting neither streaming nor bouncing percept. These catch trials were designed to ensure that participants were responding veridically based on their perceptual outcomes after two disks' coincidence event happened (Zhao et al, , ; Zhao et al, ). In the F condition , no visual motion was presented from Frames 1–21, but the flash (50 ms duration) was presented at the onset of Frame 11 and the center of the monitor (Figure d). This F condition was arranged to prevent subjects from guessing the relationship between transient flash and the visual motion.…”

“…Finally, the ERPs before the coincidence of the two visual disks were also analyzed, since the precoincidence P2 amplitude has been found to be predictive of subsequent streaming or bouncing percept (Zhao et al, ). More importantly, a recent study found that a brief sound presented at the moment of two disks' coincidence could interrupt the predictiveness of the precoincidence P2 amplitude on subsequent perceptual outcomes (Zhao et al, ).…”

“…The precoincidence P2 component was measured as mean amplitude within a time interval of 250–300 ms after Frame 1 onset over a cluster of five parietal electrode sites (CPz, P1, Pz, P2, POz). These parietal electrodes, rather than the frontocentral electrodes reported previously (Zhao et al, , ), were chosen because the current precoincidence P2 components were consistently evident over these parietal electrodes but not over frontocentral electrodes (see Figure 3, right) under all conditions (i.e., V_stream, V_bounce, VF_stream, and VF_bounce trials), which is logically equivalent to using the “ collapsed localizer ” method (Luck & Gaspelin, ) to select electrodes when the analysis parameters cannot be determined based on previous studies. The precoincidence P2 amplitudes were then subjected to a two‐way repeated‐measure ANOVA with factors of stimulus condition (V, VF) and perceptual outcome (stream, bounce).…”

Temporal dynamics of a perceptual decision

“…Importantly, two imaging studies using streambounce displays have found that prestimulus activity can predict perceptual outcomes. Recently, Zhao et al (2017) considered response-associated (stream or bounce) electroencephalographic activity to just visualonly stream-bounce stimuli. They found that early visual event-related potentials were no different for streaming versus bouncing responses, and that postcoincidence activity over parietal scalp dissociated perceptual responses.…”

“…Continuous-tracking approaches that manipulate specific top-down factors to tease apart and isolate their relative influence would be useful. Second, while previous stream-bounce imaging studies have found early effects that predict perceptual outcomes (Hipp et al, 2011;Zhao et al, 2017), each of those studies considered perceptual bistability in the context of a single stimulus type only (either all visual or all audiovisual). We suggest that extending imaging studies to mixed presentation of visual-only and audiovisual stimuli may provide insight into the influence of top-down factors on multisensory integration beyond perceptual bistability.…”