Abstract: Abstract：Human brain is a black-box dealing with a lot of stimulation in our everyday life. However, it is not a purely receiving machine in which the perception system is of plasticity and self-directed. Indeed, the visual areas in the brain are interconnected in a complex pattern of feedforward, lateral, and feedback pathways. The top-down system can send feed-back information to primary visual cortex which will affect what we perceived. For a long time, the magnitude of cortical influences on this processing in early sensory cortex is mostly underestimated. Human brain is not a purely receiving machine in which the perception system is of plasticity and self-directed. Indeed, the visual areas in the brain are interconnected in a complex pattern of feedforward, lateral, and feedback pathways. The top-down system can send feed-back information to primary visual cortex which will affect what we perceived. For a long time, the magnitude of cortical influences on this processing in early sensory cortex is mostly underestimated. In this review, we firstly conceptualized the processing of top-down modulation. Then we introduced the neural basic of top-down modulation in visual perception. Perception process has been showed to work in a spatially distributed cortical network including the subcortical structures and primary visual cortex. Early visual areas do more than encoding raw sensory signals, but they also participate in processing activities corresponding to a visual perception. Researches indicate that neural activation of top-down modulation is modulated by expertise, selective attention, mental imagery and even emotion. Methods which were usually used in past researches are also included in this review. Both of the figure-ground segregation paradigm and degraded paradigms are applied to realize the functional dissociation. And it is essential that feedforward and feedback modulation components are independently stimulated or inactivated. To provide more detailed insights, we highlighted the models interpretative of perception modulation function. (1)Attention modulation model posit that feedback to primary visual cortex modulates, tunes, or anticipates the bottom-up response to visual stimuli through selective attention. Top-down attention modulation is crucial for elucidating the mechanisms by which we can filter sensory information by paying attentions to the most behaviorally relevant events. (2)The competition between the learning of new objects and the recognition of old objects is conceptualized in the Adaptive Resonance Theory , in the case that the internal model explains well the sensory stimulation, the neuronal responses are enhanced and such recurrent enhancement is believed to lead to conscious recognition. (3) A more complex account of cortical feedback modulation is provided by the hierarchical predictive coding model. Perception processing is provided by the idea that predicted signals will depend on whether afferent sensory signals are determined. This model propose a matching inhibition mechanism, correctly predicted bottom-up signals are cancelled from further processing, or attenuated. (4) However, there are many instances where top-down projections might contribute to V1 activation even in the absence of any stimulation, so here comes the baseline activity theory and the global neuronal workspace model, proposing that there are other computational spaces in the brain which could distinguish top-down modulation from the local processors by their reciprocal long-range anatomical interconnection. Spontaneous baseline activity is another instance of stimulus-unrelated processing in primary cortex which may be a form of top-down modulation. At last, we discussed the theoretical constraints and the future research orientations. Recurrent interactions between higher and lower visual areas allow high-level neurons in the present model to express different modes of information in their firing patterns. More elaborately paradigm and precise date analysis methods are promoted。

Key words: visual perception, top-down modulation, perception modulation model, primary visual cortex

摘要： 大脑的知觉加工并非单纯由外部刺激驱动，而是存在自上而下的知觉调控。尽管这一现象被大量实验研究证实，但其神经机制仍然是认知神经科学研究的重要问题。本研究系统介绍了知觉调控的神经基础、实现形式、研究范式，及其理论模型，分析指出了当前研究面临的主要问题，并对未来的研究进行了展望，以期促进该问题研究的进一步开展。

关键词: 视觉, 自上而下调控, 知觉调控模型, 初级视皮层