Fear and anxiety are brain states that evolved to mediate defensive responses to threats. The defense reaction includes multiple interacting behavioral, autonomic and endocrine adjustments, but their integrative nature is poorly understood. In particular, although threat has been associated with various cardiac changes, there is no clear consensus regarding the relevance of these changes for the integrated defense reaction. Here we identify rapid microstates that are associated with specific behaviors and heart rate dynamics, which are affected by long-lasting macrostates and reflect context-dependent threat levels. In addition, we demonstrate that one of the most commonly used defensive behavioral responses—freezing as measured by immobility—is part of an integrated cardio-behavioral microstate mediated by Chx10⁺ neurons in the periaqueductal gray. Our framework for systematic integration of cardiac and behavioral readouts presents the basis for a better understanding of complex neural defensive states and their associated systemic functions.

恐惧和焦虑是进化来调节对威胁的防御反应的大脑状态。防御反应包括多种相互作用的行为、自主神经和内分泌调节，但人们对它们的综合性质知之甚少。特别是，尽管威胁与各种心脏变化有关，但对于这些变化与综合防御反应的相关性还没有明确的共识。在这里，我们确定了与特定行为和心率动态相关的快速微观状态，这些状态受到持久宏观状态的影响并反映了上下文相关的威胁级别。此外，我们证明最常用的防御行为反应之一——通过不动来测量的冻结——是由导水管周围灰质中的Chx10 ⁺神经元介导的综合心脏行为微状态的一部分。我们的心脏和行为读数系统集成框架为更好地理解复杂的神经防御状态及其相关的系统功能奠定了基础。