Fear protects organisms by increasing vigilance and preparedness, and by coordinating survival responses during life-threatening encounters. The fear circuit must thus operate on multiple timescales ranging from preparatory sustained alertness to acute fight-or-flight responses. Here we studied the brain basis of sustained and acute fear using naturalistic functional magnetic resonance imaging (fMRI) enabling analysis of different time-scales of fear responses. Subjects (N = 37) watched feature-length horror movies while their hemodynamic brain activity was measured with fMRI. Time-variable intersubject correlation (ISC) was used to quantify the reliability of brain activity across participants, and seed-based phase synchronization was used for characterizing dynamic connectivity. Subjective ratings of fear were used to assess how synchronization and functional connectivity varied with emotional intensity. These data suggest that acute and sustained fear are supported by distinct neural pathways, with sustained fear amplifying mainly sensory responses, and acute fear increasing activity in brainstem, thalamus, amygdala and cingulate cortices. Sustained fear increased ISC in regions associated with acute fear, and also amplified functional connectivity within this network. The results were replicated in an independent experiment with a different subject sample and stimulus movie. The functional interplay between cortical networks involved in sustained anticipation of, and acute response to, threat involves a complex and dynamic interaction that depends on the proximity of threat, and the need to employ threat appraisals and vigilance for decision making and response selection.

中文翻译：

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用于无条件的急性和持续恐惧的可分离神经系统

恐惧通过提高警惕和准备，以及在危及生命的遭遇中协调生存反应来保护生物体。因此，恐惧回路必须在多个时间尺度上运作，从准备性持续警觉到急性的战斗或逃跑反应。在这里，我们使用自然功能磁共振成像 (fMRI) 研究了持续和急性恐惧的大脑基础，从而能够分析恐惧反应的不同时间尺度。受试者 (N = 37) 观看长篇恐怖电影，同时使用 fMRI 测量他们的血液动力学大脑活动。时变主体间相关性 (ISC) 用于量化参与者大脑活动的可靠性，并使用基于种子的相位同步来表征动态连接。恐惧的主观评级用于评估同步和功能连接如何随情绪强度而变化。这些数据表明，急性和持续性恐惧受到不同神经通路的支持，持续性恐惧主要放大感觉反应，急性恐惧增加脑干、丘脑、杏仁核和扣带回皮质的活动。持续的恐惧增加了与急性恐惧相关的区域的 ISC，也放大了该网络内的功能连接。结果在具有不同主题样本和刺激电影的独立实验中得到复制。皮层网络之间的功能相互作用涉及对威胁的持续预期和急性反应，涉及复杂和动态的相互作用，取决于威胁的接近程度，