小柯机器人

美国加州大学旧金山分校Massimo Scanziani和Andreas J. Keller课题组取得新突破。他们的最新研究发现反馈可在视皮层神经元中产生第二个感受野。相关论文于2020年5月20日在线发表于《自然》杂志。

研究人员发现反馈投射到小鼠初级视觉皮层中的兴奋性神经元上会产生由非前馈感受野（ffRF）刺激引起的第二个感受野。与ffRF刺激产生的响应相比，此反馈感受野（fbRF）刺激引起的响应更慢且具有延迟性。这些反应优选通过麻醉和沉默较高的视区而降低。来自较高视觉区域的反馈输入相对于初级视觉皮层中的假定目标具有分散的感受野，这使得fbRF能够生成。

具有fbRF的神经元位于皮层中，这些皮层会收到较强的反馈投影，并且在主输入层中不存在，这与层状处理层次结构一致。覆盖fbRF和ffRF大而均匀的刺激抑制了这些反应，这表明fbRF和ffRF是相互拮抗的。表达生长抑素的抑制神经元是由这些大刺激引起的，而表达小白蛋白和血管活性肠肽的抑制神经元具有相互拮抗的fbRF和ffRF，类似于兴奋性神经元。

因此，反馈投影可以使神经元能够使用周围信息来估计ffRF所缺少的信息，并报告整个视觉空间中刺激特征的差异，而与ffRF内部还是外部发生的激发无关。除了作为ffRF的补充，该研究发现的fbRF可能有助于预测处理 。

据介绍，动物通过将感觉器官连接到大脑的途径来感知环境。在视觉系统中，这些前馈通路定义了经典的前馈感受野（ffRF），即视觉刺激激发神经元的空间区域。视觉系统还使用视觉环境（围绕刺激物的视觉场景）来预测刺激物的含量，因此，已经确定了由ffRF之外的刺激物激发的神经元。但是，尚不清楚在ffRF之外产生激发刺激的机制。

附：英文原文

Title: Feedback generates a second receptive field in neurons of the visual cortex

Author: Andreas J. Keller, Morgane M. Roth, Massimo Scanziani

Issue&Volume: 2020-05-20

Abstract: Animals sense the environment through pathways that link sensory organs to the brain. In the visual system, these feedforward pathways define the classical feedforward receptive field (ffRF), the area in space in which visual stimuli excite a neuron1. The visual system also uses visual context—the visual scene surrounding a stimulus—to predict the content of the stimulus2, and accordingly, neurons have been identified that are excited by stimuli outside their ffRF3,4,5,6,7,8. However, the mechanisms that generate excitation to stimuli outside the ffRF are unclear. Here we show that feedback projections onto excitatory neurons in the mouse primary visual cortex generate a second receptive field that is driven by stimuli outside the ffRF. The stimulation of this feedback receptive field (fbRF) elicits responses that are slower and are delayed in comparison with those resulting from the stimulation of the ffRF. These responses are preferentially reduced by anaesthesia and by silencing higher visual areas. Feedback inputs from higher visual areas have scattered receptive fields relative to their putative targets in the primary visual cortex, which enables the generation of the fbRF. Neurons with fbRFs are located in cortical layers that receive strong feedback projections and are absent in the main input layer, which is consistent with a laminar processing hierarchy. The observation that large, uniform stimuli—which cover both the fbRF and the ffRF—suppress these responses indicates that the fbRF and the ffRF are mutually antagonistic. Whereas somatostatin-expressing inhibitory neurons are driven by these large stimuli, inhibitory neurons that express parvalbumin and vasoactive intestinal peptide have mutually antagonistic fbRF and ffRF, similar to excitatory neurons. Feedback projections may therefore enable neurons to use context to estimate information that is missing from the ffRF and to report differences in stimulus features across visual space, regardless of whether excitation occurs inside or outside the ffRF. By complementing the ffRF, the fbRF that we identify here could contribute to predictive processing.

DOI: 10.1038/s41586-020-2319-4

Source: https://www.nature.com/articles/s41586-020-2319-4

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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