The Structural And Functional Basis Of Brain In Bistable Perception Of Face

Bistable perception(or multistable perception) is one kind of subjective perception that spontaneously and unpredictably alternates between two or more perceptual interpretations of an ambiguous sensory input. Bistable perception provides an ideal approach to probe the visual processing of awareness, as the subjective experience change while visual input holds constant. To date, it is controversial for the structural and functional basis of brain underlying such multistable perception or bistable perception. Past functional magnetic resonance imaging(fMRI) studies have examined the activation patterns in human early visual cortex underlying the bistable perception, yet the variability between individuals in the rate of spontaneous alternations in bistable perception is not well understood, especially when considering gray matter structure of sensory cortex and top-down controlling role of high level cognitive brain areas simultaneously.In addition, do activity patterns in early visual cortex really contain face or vase information, which neural activity or neural network determines perceptual switch, so far is still not clear. The current study mainly concentrated on the relationship of individual differences between the bistable alternation and brain structure and function, and how activity of the visual cortex in bistable perception.Experiment 1: Voxel-based morphometry(VBM) was introduced to correlate the GM of sensory cortex with the alternation rate of the Rubin face-vase illusion in a large group of young adults. We found that the GM volume/density(GMV/GMD) of the left fusiform face area(FFA) were significantly positively correlated with alternation rate. Next, granger causality analysis(GCA)was introduced to investigate the top-down modulation from high level areas to sensory cortex by using resting state fMRI data. Correlations between perception alternation rate and granger causalities showed that the top-down modulations from high level brain regions such as superior parietal lobule(SPL) and posterior cingulate cortex(PCC) to the left FFA were positive.Experiment 2: We used task-related function magnetic resonance imaging with the approach of activity amplitude analysis and activity pattern analysis to investigate the neural activity mechanism of bistable perception.In the unambiguous condition and ambiguous condition, the analysis of activity amplitude suggest that activity in fusiform face area(FFA) was highly related to subjective perception of face. In addition, the result shown that perception state could change the neural representations of V1 to V4, bilateral lateral occipital(LO), left FFA and bilateral superior temporal sulcus(STS) visual cortex. However, for the face information index in category information, only face-specific visual areas contain the information of the content of awareness.This study explored the neural basis of biatable perception individual differences, using a combined structural imaging and GCA approach. To some extent, this study might be the first to investigate the causal role of high level brain areas in bistable perception between individuals by using the granger causality analysis, and can help us directly find the top-down controlling role of high level brain areas on sensory cortex to determine the alternation rate in bistable perception.And, we used task-related fMRI with the approach of multivariate pattern analysis(MVPA) investigate the neural activity state of bistable perception processing. Together, these findings indicated that anatomical structure of face selective area may determine individual perceptual alternations in bistable perception. This process may be under the control of high level cortex such as the SPL and PCC associated with attentional modulation. Visual awareness could change the neural representations of both early and late visual cortex, however, only high-level visual areas contain the information of the content of awareness.To sum up, this study elucidate the differences in brain structure and function of the bistable perception by using different analysis methods, and thereby to reveal the physiological and psychological mechanisms of bistable perception and provide important experimental data.