Committee on Computational Neuroscience, University of Chicago, Chicago, IL 60637.
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637.
Proc Natl Acad Sci U S A. 2021 Dec 7;118(49). doi: 10.1073/pnas.2115772118.
Tactile nerve fibers fall into a few classes that can be readily distinguished based on their spatiotemporal response properties. Because nerve fibers reflect local skin deformations, they individually carry ambiguous signals about object features. In contrast, cortical neurons exhibit heterogeneous response properties that reflect computations applied to convergent input from multiple classes of afferents, which confer to them a selectivity for behaviorally relevant features of objects. The conventional view is that these complex response properties arise within the cortex itself, implying that sensory signals are not processed to any significant extent in the two intervening structures-the cuneate nucleus (CN) and the thalamus. To test this hypothesis, we recorded the responses evoked in the CN to a battery of stimuli that have been extensively used to characterize tactile coding in both the periphery and cortex, including skin indentations, vibrations, random dot patterns, and scanned edges. We found that CN responses are more similar to their cortical counterparts than they are to their inputs: CN neurons receive input from multiple classes of nerve fibers, they have spatially complex receptive fields, and they exhibit selectivity for object features. Contrary to consensus, then, the CN plays a key role in processing tactile information.
触觉神经纤维分为几类，根据它们的时空反应特性很容易区分。由于神经纤维反映了局部皮肤变形，它们各自携带关于物体特征的模糊信号。相比之下，皮质神经元表现出异质的反应特性，反映了对来自多个传入纤维类别的会聚输入的计算，这使它们对物体的行为相关特征具有选择性。传统观点认为，这些复杂的反应特性是在皮质本身内部产生的，这意味着在两个中间结构——楔束核 (CN) 和丘脑——中，感觉信号并没有被处理到任何显著程度。为了验证这一假设，我们记录了 CN 对一系列刺激的反应，这些刺激被广泛用于描述外周和皮质的触觉编码，包括皮肤凹陷、振动、随机点图案和扫描边缘。我们发现，CN 的反应与皮质的反应更相似，而不是与它们的输入相似：CN 神经元接收来自多个纤维类别的输入，它们具有空间复杂的感受野，并且对物体特征具有选择性。与共识相反，CN 在处理触觉信息方面起着关键作用。
