特定类型的抑制性神经元在图形背景分离中的贡献

Inhibitory neurons play important roles in cortical information processing. Neurons in the primary visual cortex (V1) often exhibit surround suppression, in which visual stimulation beyond the receptive field suppresses the neuron's response. Surround suppression is thought to contribute to perceptual phenomena such as figure-ground segregation and contour integration. Recent studies have shown that specific types of inhibitory neurons contribute to surround suppression of pyramidal neurons in V1. However, it remains unclear how the activities of specific types of inhibitory neurons influence the tuning properties of surround suppression and the visual behavior of figure-ground segregation, and how the activities of these inhibitory neurons are modulated by specific cortical projection. Our preliminary data showed that specific types of inhibitory neurons in V1 could be directly activated by cortical feedback projection, and that optogenetically manipulating the activity of specific type of inhibitory neurons in V1 or specific cortical feedback projection to V1 could influence the visual response and surround suppression properties of V1 neurons. In this proposal, by using electrophysiological recording, optogenetics, and visual behavior in the mouse model, we will examine the role of specific types of inhibitory neurons and specific long-range cortical projection in figure-ground segregation. This study will be an important step to understand how inhibitory neuron circuit contributes to figure-ground segregation of the visual system.

抑制性神经元对皮层的信息处理具有重要作用。在初级视皮层（V1），神经元感受野外周的刺激常常会抑制感受野刺激引起的反应。V1神经元的外周抑制被认为是图形背景分离和轮廓整合等知觉现象的机制。近年的研究表明，V1外周抑制的程度受到特定类型抑制性神经元的调节。还不清楚的是，特定类型抑制性神经元的活动如何影响V1外周抑制的调谐特征和动物的图形背景分离行为, 以及如何受到特定环路连接的调节。我们的初步实验发现，V1中特定类型的抑制性神经元可被高级皮层的反馈投射直接激活，光遗传操纵特定类型抑制性神经元或高级皮层反馈投射的活动能够影响V1神经元的视觉反应和外周抑制特征。我们将利用小鼠的电生理、光遗传和行为学等方法，研究V1中特定类型的抑制性神经元和与其相关的皮层反馈投射在图形背景分离中的作用。本研究有助于从抑制性神经元的角度深入理解视觉系统进行图形背景分离的机制。

抑制性神经元对皮层的信息处理具有重要作用。在初级视皮层（V1），感受野外周的刺激常常会抑制神经元对感受野内刺激的反应。V1神经元的外周抑制被认为是图形背景分离和轮廓整合等知觉现象的机制。近年的研究表明，V1外周抑制的程度受到特定类型抑制性神经元的调节。在该项目中，我们研究特定类型抑制性神经元的活动如何影响V1外周抑制的调谐特征和动物的图形背景分离行为。我们训练自由活动的小鼠进行图形-背景分辨任务，图形和背景光栅具有相同的方位但在空间相位上有差异。结果显示，小鼠的行为正确率随着图形-背景相位差的增加而增加，并受到视觉刺激对比度的调节。在头部固定小鼠的V1进行电生理记录表明，对于表现外周抑制的神经元，感受野内外刺激相位差的增加导致神经元的放电率增加，神经元分辨图形和背景刺激的能力增强。与行为表现一致，V1神经元对感受野内外相位差的敏感度也受到对比度的影响。进一步实验发现，光遗传激活V1中表达小清蛋白（parvalbumin，PV）或表达生长激素抑制素（somatostatin，SOM）的抑制性神经元，均能够降低小鼠图形-背景分辨行为的正确率。激活PV或SOM神经元，均能够降低V1神经元区分图形刺激和背景刺激的能力。这些结果提示，PV和SOM抑制性神经元通过影响V1神经元特征特异性的外周抑制，参与调节小鼠的图形-背景分辨行为。