Center for Complex Systems and Brain Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL, 33431, USA.
Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society, 46 Deutschordenstrasse, 60528, Frankfurt, Germany.
Sci Rep. 2018 May 3;8(1):6991. doi: 10.1038/s41598-018-25267-1.
Top-down modulation of sensory processing is a critical neural mechanism subserving numerous important cognitive roles, one of which may be to inform lower-order sensory systems of the current 'task at hand' by conveying behavioral context to these systems. Accumulating evidence indicates that top-down cortical influences are carried by directed interareal synchronization of oscillatory neuronal populations, with recent results pointing to beta-frequency oscillations as particularly important for top-down processing. However, it remains to be determined if top-down beta-frequency oscillations indeed convey behavioral context. We measured spectral Granger Causality (sGC) using local field potentials recorded from microelectrodes chronically implanted in visual areas V1/V2, V4, and TEO of two rhesus macaque monkeys, and applied multivariate pattern analysis to the spatial patterns of top-down sGC. We decoded behavioral context by discriminating patterns of top-down (V4/TEO-to-V1/V2) beta-peak sGC for two different task rules governing correct responses to identical visual stimuli. The results indicate that top-down directed influences are carried to visual cortex by beta oscillations, and differentiate task demands even before visual stimulus processing. They suggest that top-down beta-frequency oscillatory processes coordinate processing of sensory information by conveying global knowledge states to early levels of the sensory cortical hierarchy independently of bottom-up stimulus-driven processing.
自上而下的感觉加工调制是一个重要的神经机制，支持着许多重要的认知角色，其中之一可能是通过将行为背景传达给这些系统，告知低阶感觉系统当前的“手头任务”。越来越多的证据表明，自上而下的皮质影响是通过振荡神经元群体的定向区域间同步来传递的，最近的结果指出β频带振荡对自上而下的处理特别重要。然而，尚不确定自上而下的β频带振荡是否确实传递了行为背景。我们使用慢性植入两只猕猴视觉区域 V1/V2、V4 和 TEO 的微电极记录的局部场电位来测量谱格兰杰因果关系（sGC），并对自上而下的 sGC 的空间模式应用多元模式分析。我们通过区分两种不同任务规则下（V4/TEO 到 V1/V2）β峰 sGC 的自上而下模式来对行为背景进行解码，这些任务规则决定了对相同视觉刺激的正确反应。结果表明，自上而下的定向影响是由β振荡传递到视觉皮层的，并且在视觉刺激处理之前就区分了任务需求。它们表明，自上而下的β频带振荡过程通过将全局知识状态传递到感觉皮质层次结构的早期水平来协调感觉信息的处理，而与自下而上的刺激驱动处理无关。
