Higley Michael J, Contreras Diego
Department of Neuroscience, University of Pennsylvania, School of Medicine, 215 Stemmler Hall, Philadelphia, PA 19104, USA.
J Neurophysiol. 2007 Jan;97(1):647-58. doi: 10.1152/jn.00777.2006. Epub 2006 Oct 25.
The neural integration of afferent inputs evoked by spatiotemporally distributed sensory stimuli is a critical step in the formation of coherent and continuous perceptual representations. Integration mechanisms in various systems include linear and nonlinear summation of sensory responses. One well-known example in the rat barrel system is the suppressive interaction between responses to the consecutive deflection of neighboring whiskers. The mechanism underlying cross-whisker suppression has long been postulated to rely on intracortical postsynaptic inhibition, although this hypothesis has been challenged by recent reports. Here we show, using intracellular and extracellular recordings in vivo, that cross-whisker suppression occurs in the absence of cortical activity. Instead, suppression arises from local circuit operations at multiple levels of the subcortical afferent pathway and is amplified by the nonlinear transformation of synaptic input into spike output in both the thalamus and cortex. Because these cellular processes are common to neural circuits subserving visual and auditory modalities, we propose that the suppressive mechanisms elucidated here are a general property of thalamocortical sensory systems.
由时空分布的感觉刺激诱发的传入输入的神经整合是形成连贯和连续感知表征的关键步骤。各种系统中的整合机制包括感觉反应的线性和非线性总和。大鼠桶状系统中一个著名的例子是相邻触须连续偏转反应之间的抑制性相互作用。长期以来，人们一直假定跨触须抑制的机制依赖于皮质内突触后抑制，尽管这一假设受到了最近报告的挑战。在这里，我们通过体内细胞内和细胞外记录表明，跨触须抑制在没有皮质活动的情况下也会发生。相反，抑制来自皮质下传入通路多个水平的局部回路操作，并通过丘脑和皮质中突触输入到尖峰输出的非线性转换而放大。由于这些细胞过程对于服务于视觉和听觉模式的神经回路是常见的，我们提出这里阐明的抑制机制是丘脑皮质感觉系统的一般特性。
