Neuronal mechanisms of cortical processing in early vision

项目总结 视觉信息从眼睛通过开关通路传递到大脑，这些通路发出信号 视觉场景中明暗特征的存在。在所有动物身上都存在着开和离的通路 然而，包括苍蝇和灵长类在内的成像视觉系统，我们仍然对它们是如何形成的知之甚少 它们在视觉处理中相互作用。尽管神经科学教科书将路径上和路径下的描述为共享 等大脑皮层间隙，最近的研究表明，非通路在很大程度上支配大脑皮层 回应。我们假设这种皮质优势源于对比的不同。 我们最近发现的通路上和下通路之间的反应函数。因为对比度饱和是 光刺激在ON通路中更为明显，在空间上扭曲，在驾驶时效率较低 大脑皮层的反应比暗刺激更强，这会导致大脑皮层失控。正因为如此，更大的 对于灯光的空间失真，我们预测对比度饱和度的开/关差异将有较大的 不仅在皮质功能方面，而且在人类视觉感知和视觉疾病方面也有意义。因此，这 Proposal使用开/关对比饱和度的差异作为概念框架来预测和 研究不同刺激条件下皮层关闭优势的变化及其意义 这些变化使人们对光明和黑暗的感知发生了变化。我们的概念框架预测大脑皮层关闭 由于镜头的正常变化，当图像失焦时，优势将会增加 适应能力(例如，近距离注视目标时背景模糊)或视觉疾病(例如 弱视、近视)。反过来，当看到较高的空间频率时，皮质关闭优势将减少 高平均亮度，这是户外常见的。来检验我们的预测并调查 关于皮层功能，我们将测量皮层单个神经元对黑暗和光明的反应 各种刺激条件下的目标(例如，不同的对比度，空间频率，平均亮度， 亮度分布)。然后，我们将使用相同的刺激条件来测量明/暗视觉的变化 人类的敏锐度和视觉突出性。为了全面描述单个神经元对多个 刺激维度，我们将使用我们多年来一直在开发的创新多电极阵列 在过去的几年里，从分离良好的单个神经元中记录了很长一段时间。这项新颖的技术 这种方法使我们能够获得对调节开/关的刺激空间的前所未有的表征 通过测试一系列刺激条件的大组合来发出信号，这些条件不能用以前的 方法：研究方法。

PROJECT SUMMARY Visual information is transferred from the eye to the brain through ON and OFF pathways that signal the presence of light and dark features in visual scenes. ON and OFF pathways are present in all animals with image-forming visual-systems including flies and primates, however, we still have a poor understanding of how they interact in visual processing. While neuroscience textbooks describe ON and OFF pathways as sharing equal cortical space, recent work has demonstrated that the OFF pathway greatly dominates cortical responses. We hypothesize that this cortical OFF dominance originates from a difference in the contrast response function between ON and OFF pathways that we recently discovered. Because contrast saturation is more pronounced within the ON pathway, light stimuli are spatially distorted and less effective at driving cortical responses than dark stimuli, which causes the cortex to be OFF dominated. Because of this greater spatial distortion for lights, we predict that ON/OFF differences in contrast saturation will have major implications not only in cortical function but also in human visual perception and visual disease. Therefore, this proposal uses the differences in ON/OFF contrast saturation as a conceptual framework to predict and investigate how cortical OFF dominance changes under different stimulation conditions and the implications of these changes for the perception of lights and darks. Our conceptual framework predicts that cortical OFF dominance will increase when the image is out of focus either because of normal changes in lens accommodation (e.g. blurred background when fixating a target at close distance) or visual disease (e.g. amblyopia, myopia). In turn, cortical OFF dominance will decrease when seeing high spatial frequencies with high mean luminance, which are common outdoors. To test our predictions and investigate the dynamics of ON and OFF cortical function, we will measure the responses of cortical single neurons to dark and light targets under a large variety of stimulus conditions (e.g. different contrasts, spatial frequency, mean luminance, luminance distribution). We will then use the same stimulus conditions to measure changes in light/dark visual acuity and visual salience in humans. To fully characterize cortical responses of single neurons to multiple stimulus dimensions, we will use an innovative multielectrode array that we have been developing over the past years to record from well-isolated single neurons for prolonged periods of time. This novel technical approach allows us to obtain an unprecedented characterization of the stimulus space that modulates ON/OFF signaling by testing a large combination of stimulus conditions that could not be fully explored with previous methods.