Higher-order thalamus input to the cortex Sensory information can only be used meaningfully in the brain when integrated with and compared with internally generated top-down signals. However, we know little about the brainwide afferents that convey such top-down signals, their information content, and learning-related plasticity. Pardi et al. identified the higher-order thalamus as a major source of top-down input to mouse auditory cortex and investigated a circuit in cortical layer 1 that facilitates plastic changes and flexible responses. These results demonstrate how top-down feedback information can reach cortical areas through a noncortical structure that has received little attention despite its widespread connections with the cortex. Science, this issue p. 844 Synaptic imaging identifies thalamic afferents to the cortex as a highly experience-dependent, dynamically controlled source of top-down information. The sensory neocortex is a critical substrate for memory. Despite its strong connection with the thalamus, the role of direct thalamocortical communication in memory remains elusive. We performed chronic in vivo two-photon calcium imaging of thalamic synapses in mouse auditory cortex layer 1, a major locus of cortical associations. Combined with optogenetics, viral tracing, whole-cell recording, and computational modeling, we find that the higher-order thalamus is required for associative learning and transmits memory-related information that closely correlates with acquired behavioral relevance. In turn, these signals are tightly and dynamically controlled by local presynaptic inhibition. Our results not only identify the higher-order thalamus as a highly plastic source of cortical top-down information but also reveal a level of computational flexibility in layer 1 that goes far beyond hard-wired connectivity.

中文翻译：

---

用于联想记忆的丘脑皮质自上而下电路

输入到皮层的高阶丘脑 感觉信息只有在与内部生成的自上而下的信号进行整合和比较时，才能在大脑中有意义地使用。然而，我们对传达这种自上而下的信号的全脑传入、它们的信息内容和与学习相关的可塑性知之甚少。帕迪等人。确定高阶丘脑是小鼠听觉皮层自上而下输入的主要来源，并研究了皮层 1 中促进塑性变化和灵活反应的电路。这些结果证明了自上而下的反馈信息如何通过非皮层结构到达皮层区域，尽管它与皮层有广泛的联系，但很少受到关注。科学，这个问题 p。844 突触成像将丘脑传入皮层识别为高度依赖经验、动态控制的自上而下信息源。感觉新皮层是记忆的关键基质。尽管丘脑与丘脑有很强的联系，直接丘脑皮层交流在记忆中的作用仍然难以捉摸。我们对小鼠听觉皮层第 1 层（皮层关联的主要位点）中的丘脑突触进行了慢性体内双光子钙成像。结合光遗传学、病毒追踪、全细胞记录和计算建模，我们发现高阶丘脑是联想学习所必需的，并传输与获得的行为相关性密切相关的记忆相关信息。反过来，这些信号受到局部突触前抑制的严格和动态控制。