一项研究发现，人类大脑可能根据威胁物的接近程度、轨迹以及对其的预期从而对其做出不同的反应。Dean Mobbs及其同事使用功能磁共振成像（fMRI）观察了20位实验参与者的大脑活动，当时参与者们在观看他们认为是科学家把一个捕鸟蛛放在每位参与者脚边的实时视频。
尽管这些视频其实是预先录制的，这些参与者认为这个蜘蛛是放在了6个隔间中的1个，由这组科学家操纵诱使这只蜘蛛爬向或者爬离每位参与者。参与者报告了在整个实验期间他们预期的和真实的恐惧体验。这组作者观察到，无论捕鸟蛛与参与者的绝对距离是多少，当捕鸟蛛慢慢接近而不是撤退的时候，大脑的恐慌反应中心出现了更大的活动，参与者也报告了更大的恐惧。
这组作者报告说，一些大脑区域活动的涨落是根据蜘蛛的轨迹，而另外一些区域仅仅在极端恐惧或蜘蛛距离参与者最远的时候才有反应。这些结果提示，大脑的“恐惧网络”的不同组件有不同的威胁-响应功能。此外这组作者说，这一信息可能会帮助科学家诊断和治疗临床恐惧症的患者。
推荐英文摘要：
PNAS doi: 10.1073/pnas.1009076107
Neural activity associated with monitoring the oscillating threat value of a tarantula
Dean Mobbsa,1, Rongjun Yua, James B. Rowea,b, Hannah Eicha, Oriel FeldmanHalla, and Tim Dalgleisha
aCognition and Brain Sciences Unit, Medical Research Council-Cognition and Brain Sciences Unit, Cambridge CB2 7EF, United Kingdom; and
bDepartment of Clinical Neurosciences, University of Cambridge, Cambridge CB2 2QQ, United Kingdom
Phylogenetic threats such as spiders evoke our deepest primitive fears. When close or looming, such threats engage evolutionarily conserved monitoring systems and defense reactions that promote self-preservation. With the use of a modified behavioral approach task within functional MRI, we show that, as a tarantula was placed closer to a subject's foot, increased experiences of fear coincided with augmented activity in a cascade of fear-related brain networks including the periaqueductal gray, amygdala, and bed nucleus of the stria terminalis. Activity in the amygdala was also associated with underprediction of the tarantula's threat value and, in addition to the bed nucleus of the stria terminalis, with monitoring the tarantula's threat value as indexed by its direction of movement. Conversely, the orbitofrontal cortex was engaged as the tarantula grew more distant, suggesting that this region emits safety signals or expels fear. Our findings fractionate the neurobiological mechanisms associated with basic fear and potentially illuminate the perturbed reactions that characterize clinical phobias.
