Circuits for contextual modulation in V1

我们目前对初级视觉皮层（V1）感觉表征的机械理解是 主要是“前馈”。即，V1的感受野（RF）的时空结构 神经元是由早期阶段传递的感受野成分组合而成的。 视觉处理（即视网膜和丘脑），以前馈方式。虽然计算 基于对V1的这种前馈理解的模型在预测 神经元对神经元RF边界内呈现的视觉刺激的反应，它们 当刺激超过RF的大小时，通常会失败，就像日常视觉一样 涵盖整个视野的场景。当前无法实现的主要原因之一是 预测V1神经元对自然刺激的反应的模型是， V1对RF中的刺激的强烈调制是由RF之外发生的事情引起的。换句话说， V1中的神经元如何对RF中呈现的刺激做出反应取决于上下文， “包围”，在其中呈现刺激。在自然界中，视觉刺激落在 V1神经元的RF永远不会缺乏周围环境。与这些神经生理学上的 观察，人类和动物的心理物理实验表明， 视觉刺激取决于其与周围视觉环境的关系。因此， 依赖于上下文的视觉信息处理是视觉皮层的一个关键特性， 深刻影响了我们对世界的认知只有一个明确的机械，电路水平 了解背景如何调节V1的反应将使我们能够产生现实的， 模型能够准确地预测该区域对自然刺激的反应。 神经生理学数据表明，V1区神经元反应的背景调制最 很可能依赖于皮层内的相互作用也就是说，虽然V1神经元的经典RF结构 由于前馈过程，环绕声的调制可能取决于帧内， 皮质电路元件，它们的连接模式和它们的动态相互作用。这项建议 旨在阐明这些皮层电路元件，以及它们的相互作用如何引起 在V1中对视觉刺激的反应的上下文调制。一个彻底的机械 理解V1中的语境调制将使我们能够建立现实的模型， 捕捉视觉皮层对自然刺激的反应。由此获得的数据 建议将是必不可少的通知和验证V1的现实模型。

Our current mechanistic understanding of sensory representation in primary visual cortex (V1) is principally “feed-forward”. That is, the spatio-temporal structure of the receptive field (RF) of V1 neurons results from the combination of receptive filed elements transmitted by earlier stages of visual processing (i.e. retina and thalamus), in a feed-forward manner. While computational models based on this feed-forward understanding of V1 are relatively accurate at predicting the response of neurons to visual stimuli presented within the borders of the neuron’s RF, they generally fail when the stimuli exceed the size of the RF, as is the case for every-day visual scenes that encompass the entire field of view. One of the main reason for the inability of current models to predict responses of V1 neuron to naturalistic stimuli is that the response of neurons in V1 to stimuli in their RF is strongly modulated by what happens outside of their RF. In other words, how neurons in V1 respond to a stimulus presented in their RF depends on the context or “surround” within which the stimulus is presented. In the natural world, visual stimuli falling in the RF of a V1 neuron are never devoid of a surround. Consistent with these neurophysiological observations, psychophysical experiments in humans and animals show that the perception of a visual stimulus depends on its relationship to the surrounding visual context. Thus, the ability to process visual information depending on the context is a key property of visual cortex and has a profound impact on how we perceive the world. Only a clear mechanistic, circuit level understanding of how the context modulates the response of V1 will allow us generate realistic models capable of accurately predicting the response of this area to naturalistic stimuli. Neurophysiological data indicate that contextual modulation of neuronal responses in V1 most likely relies on intra-cortical interactions. That is, while the classical RF structure of a V1 neuron results from a feed-forward process, the modulation by the surround likely depends on intra- cortical circuit elements, their connectivity pattern and their dynamic interactions. This proposal aims at elucidating these cortical circuit elements and how their interaction gives rise to the contextual modulation of the response to visual stimuli in V1. A thorough mechanistic understanding of contextual modulation in V1 will allow us to build realistic models capable of capturing the response of visual cortex to naturalistic stimuli. Thus, data obtained from this proposal will be essential in informing and validating realistic models of V1.