中国科学院昆明动物研究所机构知识库

根据大范围首先的拓扑知觉理论，视知觉的第一步是检测视觉刺激的拓扑特征。尤其是检测视觉刺激有洞还是无洞。 洞是一个特殊的拓扑特征，在意识状态下，视觉过程的早期，脑对洞的检测就像对基本特征的检测一样，比起对其它特征的检测都快速。电生理研究表明，在猕猴颞叶腹侧部，有些神经元特异性地对洞的视觉刺激敏感，其潜伏期相当地短。但经典皮层通路对洞的信息处理目前并不清楚。 在本博士论文中，我将报告对洞的视知觉的研究，研究包含了3类共5个实验（第2部分由3个实验组成）。 实验1 咖啡因对双眼竞争时，“洞”，“非洞”竞争的影响在这个实验中，我们应用双眼竞争中的连续闪烁抑制的范式（continuous flash suppression (CFS)）来比较洞和非洞在不同意识状态下信息处理过程的异同。在这个实验中，咖啡因用来兴奋大脑皮层，我们比较了在咖啡因4个不同浓度下，视觉系统对洞和非洞信息处理的异同。 我们的结果表明了中等剂量的咖啡因对洞和非洞视觉辨别的影响存在着明显的差异，能够增加非洞的竞争力，但是对洞的竞争力没有影响。这个结果暗示了对洞的信息处理不仅仅依赖于视觉皮层，很可能和皮层下通路有关，而对非洞视觉刺激而言，视觉皮层起着十分重要的作用。实验2：初级视觉皮质经颅磁刺激（TMS）对洞视知觉信息处理的影响在这个实验中，我们给予初级视觉皮质单个脉冲磁刺激，以干扰初级视觉皮层的功能。我们的结果表明了在视觉刺激呈现后30ms和100ms时，给予TMS严重影响了对非洞的视觉辨别，但对洞的视觉辨别没有显著影响。这个结果提示视觉皮层无论是在早期视觉过程或是晚期视觉过程中即使受到干扰，都不影响洞的视知觉过程。很可能对洞的信息处理是通过皮层下通路快速处理完成的，绕开了速度较慢的经典皮层处理通路，这可能是大范围首先的脑机制。实验3 洞信息处理的脑功能成像研究在这个实验中，我们使用脑功能核磁成像技术研究了视觉皮层下通路对洞的信息处理。皮层下视觉通路包括中脑上丘结构，丘脑枕结节和杏仁核。这条通路避开经典皮层视觉通路，快速处理粗糙的和情绪相关的视觉信息。我们发现，洞的视觉刺激比非洞的视觉刺激更能激起上丘和丘脑枕结节的兴奋。结合我们前几个实验，我们的研究表明了拓扑视觉信息处理不仅仅依靠经典的皮层视觉通路，视觉皮层下通路在其中起着重要的作用。我们的研究结果阐明了皮层下通路和拓扑视知觉过程的关系，在这个博士论文中，我们讨论了这条皮层下通路的演化和生理学意义。 

According to the “global-first” topological approach to visual perception, the first step in visual perception is the extraction of topological properties, particularly the determination of whether the object has a hole. "Hole" is an independently perceptual extracted global property, which perceptual speed is fast than other properties. Previous studies suggest that neural processing mechanism between “hole” and “no-hole” may be different. Accumulating behavioral evidence has shown that the hole feature can be rapidly extracted by the visual system as a primitive feature at the beginning of visual processing, with some advantages during conscious perception. Electrophysiological evidence in monkeys revealed that neurons in the inferior temporal (IT) cortex were selectively activated through a “hole” with a short latency (<100 ms). However, the classical visual pathway through which the “hole” rapidly reaches the temporal lobe remains unknown.In this dissertation, I will report my PhD study on the visual perception of “hole”. This study includes 3 experiments as below:Experiment 1: The impact of caffeine on “hole and no-hole" perceptions in binocular rivalry paradigm. In this experiment, we applied a special paradigm of binocular rivalry which is known as continuous flash suppression (CFS) to compare “hole and no-hole” processing in altered consciousness states, and coffee was used to cause caffeine-induced cortex arousal. We compared the respond time between “hole” and “no-hole” among 4 groups which drank coffee with different caffeine dose (high caffeine dose group with 100mg caffeine; median caffeine dose group with 4mg caffeine; low caffeine dose group with 1mg caffeine; control group with no caffeine) to study the arousal effect on topological perceptual speed after using caffeine. The result showed that the response time gap between “hole and no-hole” was affected by caffeine with median caffeine dose (p<0.05). According to the results, increasing cortex excitability could improve perceptual speed of the “no-hole”, but has little impact on the perception of the “hole”. We speculated that “hole” processing may not only depend on the visual cortex, but also involve subcortical pathways.Experiment 2: Advantage of the hole stimulus under disruption of the early visual cortex, a TMS study.In this experiment, we applied single-pulse transcranial magnetic stimulation (TMS) over the occipital pole to suppress the activity of the early visual cortex, showing that the discrimination of no-hole stimuli was remarkably impaired through TMS at delay intervals of 30 and 100 ms, which are vital temporal phases in cortical visual processing. However, the hole feature perception was immune to the disruption of the early visual cortex. These results suggest that information for the hole feature can be processed when early and late visual processing in the early visual cortex is blocked. Furthermore, the information for the hole feature may be visually processed through a fast subcortical pathway, thereby bypassing slow cortical visual processing and resulting in the rapid extraction of global-first topological properties.Experiment 3: Functional magnetic resonance imaging (fMRI) study of visual perception of hole.In this experiment, fMRI is used to study the function of subcortical visual pathway in visual perception of hole. Except classical visual pathway, there is another phylogenetically older subcortical visual system including superior colliculus (SC), pulvinar and amygdala is found to process the less detailed but faster processing about emotion, bypassing the primary visual cortex. Using fMRI, we found that compared with no-hole figure, the hole figure could active stronger response in SC and pulvinar. Merging our previous study, our study demonstrated that topological perception was processed not only by classical visual pathway, but also could be processed by subcortical pathway.The results from our study suggest that this subcortical pathway also is related to topological visual perception .The evolution and biological significance of this pathway was discussed in this dissertation.