Neural oscillations in the infralimbic cortex after electrical stimulation of the amygdala. Relevance to acute stress processing.

The stress system coordinates the adaptive reactions of the organism to stressors. Therefore, dys-functions in this circuit may correlate to anxiety-related disorders, including depression.Comprehending the dynamics of this network may lead to a better understanding of the mecha-nisms that underlie these diseases. The central nucleus of the amygdala (CeA) activates thehypothalamic–pituitary–adrenal axis and brainstem nodes by triggering endocrine, autonomic andbehavioral stress responses. The medial prefrontal cortex plays a significant role in regulating reac-tions to stressors, and is specifically important for limiting fear responses. Brain oscillations reflectneural systems activity. Synchronous neuronal assemblies facilitate communication and synapticplasticity, mechanisms that cooperatively support the temporal representation and long-term con-solidation of information. The purpose of this article was to delve into the interactions betweenthese structures in stress contexts by evaluating changes in oscillatory activity. We particularlyanalyzed the local field potential in the infralimbic region of the medial prefrontal cortex (IL) inurethane-anesthetized rats after the electrical activation of the central nucleus of the amygdala bymimicking firing rates induced by acute stress. Electrical CeA activation induced a delayed, but sig-nificant, change in the IL, with prominent slow waves accompanied by an increase in the theta andgamma activities, and spindles. The phase-amplitude coupling of both slow waves and theta oscilla-tions significantly increased with faster oscillations, including theta-gamma coupling and thenesting of spindles, theta and gamma oscillations in the slow wave cycle. These results are furtherdiscussed in neural processing terms of the stress response and memory formation.应激系统可协调生物体对应激源的适应性反应。因此，该神经环路的功能异常或与抑郁等焦虑相关精神障碍存在关联。解析该网络的动态运作机制，有助于深入理解上述疾病的潜在发病机制。杏仁核中央核（central nucleus of the amygdala, CeA）可通过触发内分泌、自主神经及行为层面的应激反应，激活下丘脑-垂体-肾上腺轴（hypothalamic–pituitary–adrenal axis）与脑干核团。内侧前额叶皮层（medial prefrontal cortex）在调控应激反应中发挥关键作用，尤其在抑制恐惧反应方面至关重要。脑振荡可反映神经系统的活动状态。同步化神经元集群能够促进神经元间通讯与突触可塑性，二者协同支持信息的时序表征与长期巩固过程。本研究旨在通过评估振荡活动的变化，解析应激状态下上述脑结构间的相互作用机制。本研究特别针对乌拉坦（urethane）麻醉的大鼠，在通过模拟急性应激诱导的神经元放电速率刺激杏仁核中央核后，对其内侧前额叶皮层下边缘亚区（infralimbic region, IL）的局部场电位（local field potential）进行了分析。电刺激CeA可诱导IL区域出现延迟但显著的活动变化，表现为显著的慢波活动增强，同时伴随theta节律（theta oscillations）、gamma节律（gamma oscillations）及纺锤波（spindles）活动的提升。慢波与theta振荡的相位-振幅耦合（phase-amplitude coupling）均显著增强，且与快速振荡存在关联，具体包括theta-gamma耦合，以及纺锤波、theta与gamma振荡在慢波周期内的嵌套现象。最后，本文将从应激反应与记忆形成的神经加工层面，对上述结果展开进一步讨论。