Numerical data underlying Fig 4.

Active and passive sensing strategies are integral to an animal’s behavioral repertoire. Nevertheless, there is a lack of information regarding the neuronal circuitry that underpins these strategies, particularly at the thalamus level. We evaluated how active versus passive whisker deflections are represented in single neurons of the ventral posteromedial thalamus (VPM) and the posterior medial thalamus (POm) in awake mice. These are the first- and higher-order thalamic nuclei of the whisker system, respectively. VPM neurons robustly responded to both active and passive whisker deflections, while POm neurons showed a preference for passive deflections and responded poorly to active touches. This response disparity could not be explained by stimulus kinematics and only in part by the animal’s voluntary whisking state. In contrast, cortical activity significantly influenced POm’s responses to passive touch. Inhibition of the barrel cortex strongly attenuated whisker responses in POm and simultaneously increased the whisking phase coding. This suggests that POm receives touch information from the cortex which strongly adapts and is gated by rare events. Together, these findings suggest two thalamic relay streams, where VPM robustly relays both active and passive deflection, while POm’s sensitivity requires top-down cortical involvement to signal salient events such as unexpected deflections, originating in the environment.

主动与被动感知策略是动物行为谱中不可或缺的组成部分。然而，目前仍缺乏支撑此类策略的神经环路相关研究信息，尤其是在丘脑层面。我们对清醒小鼠的腹后内侧丘脑（ventral posteromedial thalamus, VPM）与后内侧丘脑（posterior medial thalamus, POm）的单个神经元活动进行分析，以探究主动与被动胡须偏转的神经表征模式；二者分别属于胡须感知系统的一级与高阶丘脑核团。VPM神经元可对主动与被动两种胡须偏转模式产生强烈响应，而POm神经元则偏好被动偏转，对主动触碰的响应极弱。这种响应差异无法通过刺激运动学特征解释，仅能部分归因于动物的自主胡须摆动状态。与之相反，皮层活动可显著影响POm神经元对被动触碰的响应。抑制桶状皮层可大幅削弱POm神经元的胡须响应，同时增强对胡须摆动相位的编码能力。这提示POm接收来自皮层的触碰信号，此类信号会因罕见事件发生显著适配与门控调控。综上，本研究结果提示存在两条丘脑中继通路：VPM可稳定中继主动与被动两种胡须偏转信号；而POm的感知敏感性需要自上而下的皮层调控，以编码来自环境的意外偏转等显著事件。