新研究发现，当人受到凶猛动物威胁时，与凶猛动物的距离决定了大脑的哪个部分参与这个情况的处理。确定人类大脑中涉及对付威胁的部分也许能帮助患有焦虑紊乱的人。Dean Mobbs 和英国的这项研究是建立在用大鼠研究得到的类似结果之上的。在他们的这项研究中，志愿者用一个计算机游戏装置，用一个红点代表凶猛动物，它能通过键盘电击游戏者使其感到疼痛。研究人员用功能磁共振成像监测游戏者大脑中的血液流动，当凶猛动物在远处时，高级的前额叶皮层是活跃的。这个区域是基于价值的复杂决定的中心，它让被测试者产生有充分准备的逃离路线。但是，当凶猛动物出现在近处时，血液流向低级的中脑，那是涉及搏斗、逃离、或装死决定的快速反射的区域。在一篇相关的研究评述中Stephen Maren进一步解释了这项研究。
英文原文：
Science 24 August 2007:
Vol. 317. no. 5841, pp. 1079 - 1083
DOI: 10.1126/science.1144298
When Fear Is Near: Threat Imminence Elicits Prefrontal-Periaqueductal Gray Shifts in Humans
Dean Mobbs,* Predrag Petrovic, Jennifer L. Marchant, Demis Hassabis, Nikolaus Weiskopf, Ben Seymour, Raymond J. Dolan, Christopher D. Frith
Humans, like other animals, alter their behavior depending on whether a threat is close or distant. We investigated spatial imminence of threat by developing an active avoidance paradigm in which volunteers were pursued through a maze by a virtual predator endowed with an ability to chase, capture, and inflict pain. Using functional magnetic resonance imaging, we found that as the virtual predator grew closer, brain activity shifted from the ventromedial prefrontal cortex to the periaqueductal gray. This shift showed maximal expression when a high degree of pain was anticipated. Moreover, imminence-driven periaqueductal gray activity correlated with increased subjective degree of dread and decreased confidence of escape. Our findings cast light on the neural dynamics of threat anticipation and have implications for the neurobiology of human anxiety-related disorders.
Wellcome Trust Centre for Neuroimaging, Functional Imaging Laboratory, University College London, London WC1N 3BG, UK.
* To whom correspondence should be addressed. E-mail: d.mobbs@fil.ion.ucl.ac.uk
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