| 其他摘要 | Our visual system is highly sensitive to the movements of biological entities. Biological motion (BM) carries a wealth of biologically and socially relevant information including direction, shape, identity, emotion and intention. The ability to recognize and decipher these signals is essential for human survival and social life. BM processing involves multiple levels, from sensory perception to social cognition. At perceptual level, recent work has suggested that BM perception is primarily built on our visual experience gained from long-term interactions with other creatures throughout evolution, which closely relates to the superior perceptual processing of local kinematics. However, the neural basis of local BM processing is poorly understood. On the other hand, BM signals have certain social functions. For example, the walking direction of BM, like eye gaze, acts as a social cue and induces reflexive attentional orienting effect. But it remains equivocal whether social attention triggered by different social cues is driven by a common neural substrate and whether it is
qualitatively distinct from non-social attention. A number of studies highlight a critical role of superior temporal cortex (STS/STG) in processing bio-social information. In spite of some neuroimaging evidence, the causal contributions of this region to multilevel BM processing remain largely unknown.
To address these questions, this project combined psychophysics, brain imaging and transcranial magnetic stimulation (TMS) techniques to explore the specific brain mechanisms underlying BM processing from the perspectives of perception and function. We targeted two main questions: (1) The neural basis of local BM processing; (2) The specific neural module of social attention. Here we focused on the role of the right posterior superior temporal cortex in BM multilevel processing.
In study 1 we investigated the causal contributions of cortical areas to BM, especially local BM perception. In particular, TMS targeted two motion-sensitive regions, the posterior superior temporal sulcus (pSTS) and medial temporal area (MT+) in the right hemisphere, which were functionally localized at individual level. Observers were asked to perform a motion direction discrimination task on intact BM, scrambled BM and simple coherent motion, respectively. Our results showed that TMS over pSTS impaired the direction discrimination of intact BM, whereas TMS over MT+disrupted the perception of simple coherent motion but not intact BM. However, there was no any significant impairment observed on direction discrimination of scrambled BM following stimulation over either site. These findings indicate a unique process of local BM which is likely to be achieved at an early stage of visual processing.
Study 2 aimed to examine the functional specialization of the superior temporal cortex in social attention. Using a modified central cueing paradigm, we evaluated whether TMS over the right posterior superior temporal gyrus (pSTG) impairs the attentional effect induced by different types of cues, that is social cues (i.e., eye gaze and BM) vs. non-social cues (i.e., arrows). Our results demonstrated that both social and non-social cues exerted reflexive attentional orienting. Cueing effects elicited by eye gaze and BM were simultaneously reduced following pSTG stimulation, while arrow cueing effect remained unaffected. These findings reveal that social attention induced by different types of cues might share a common neural substrate, which is distinct from non-social attention.
Taken together, our work provides direct evidence for the specific neural mechanisms undergirding the complex cognitive processes of BM signals, which advances our understanding of bio-social information processing. |
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