Functional Anatomy of Face Processing in the Primate Brain

人类下颞叶(IT)皮质的损害可能导致被称为面容失认症的综合征，即无法识别熟悉的面孔。猴子IT皮层的单细胞记录揭示了神经元的存在，这些神经元被面部的视觉图像选择性地激活。此外，人类和猴子大脑的功能磁共振成像(FMRI)都显示了人脸选择性区域，在这些区域，人脸引起的fMRI信号比非人脸物体引起的更大。总而言之，这些研究指向灵长类大脑中处理面孔的专门神经机制。到目前为止，我们的团队和其他人已经证明，面部处理的神经回路由大脑大脑区域的网络组成，这些区域位于颞叶和前额叶皮质以及杏仁核中。 在过去的一年里，我们在调节人脸加工的神经机制方面有了一些重要的发现： 1.电刺激杏仁核导致猴子颞叶面部选择性区域的fMRI激活比对象选择性区域更强，这表明大脑皮质的人脸处理受到杏仁核反馈的强烈调制，这可能传达了另一种表情发出的情感信号，并将观众的注意力集中在诊断面部特征上。 2.结合机器学习方法对fMRI信号的多体素模式分析表明，情绪表情和面部认同的分类存在于人脑的不同神经基础上：前者位于杏仁核和后上颞沟(STS)，后者位于梭形面部区域和前下颞叶皮质。 3.第一次经颅磁刺激(TBS)通过后STS传递暂时扰乱神经活动，与通过顶端传递的TBS相比，在后STS、前STS和杏仁核对动态面孔(而不是对身体或物体)的神经反应减少，这表明人类对动态面孔的感知是通过STS的皮质-杏仁核通路。 4.鼻内注射催产素是一种神经肽，也是自闭症的潜在治疗方法，它选择性地改变了猴子对情绪表达的fMRI反应，显著降低了对面孔反应区域对恐惧和攻击性面孔的反应，而对安抚和中性面孔的反应保持不变，从而解释了催产素对社会认知的有益影响。 5.药物失活结合功能磁共振成像研究表明，脸部加工区之间的功能网络是层级组织的：Face对杏仁核的激活依赖于前颞叶脸部区域的输入，而这些前部区域的激活则依赖于更多的后部颞叶脸部区域的输入。 6.人类对结构面孔差异的检测导致后顶叶皮质(PPC)相对于特征面孔差异更强的激活，而以PPC为中心的经颅磁刺激削弱了它们在结构面孔差异检测上的表现，而不是特征面孔差异检测，这表明PPC内的空间机制对于结构面孔加工以及更广泛地说对于真实面孔的感知是必要的。 7.Moebius综合征是一种罕见的遗传性神经疾病，以面瘫为特征，患者表现出识别他人情绪表达的能力受损，这表明对情绪表达的感知取决于自己产生这些表情的能力。 8.猴子的眼球运动模式表明，它们和人类一样，会经历面部幻觉，即在无生命的物体上感知面部的体验，这表明这种错觉是由我们与其他物种共享的广泛调整的面部检测机制驱动的。

Lesions of inferior temporal (IT) cortex in humans can result in the syndrome termed prosopagnosia, an inability to recognize familiar faces. Single-cell recordings from IT cortex of monkeys have revealed the existence of neurons that are selectively activated by visual images of faces. Additionally, functional magnetic resonance imaging (fMRI) of both human and monkey brains has demonstrated face-selective regions, in which the fMRI signal evoked by faces is greater compared to that evoked by non-face objects. Together, these studies point to specialized neural machinery in the primate brain for processing faces. Thus far, our group and others have shown that the neural circuitry for face processing consists of a network of brain regions in the temporal and prefrontal cortex as well as in the amygdala. During the past year, we have made a number of important discoveries regarding the neural mechanisms mediating face processing: 1. Electrical stimulation of the amygdala led to stronger fMRI activation in face- than object-selective regions in the monkey temporal lobe, indicating that cortical face processing is strongly modulated by feedback from the amygdala, which likely conveys the emotion signaled by anothers expression and focuses the viewers attention on diagnostic facial features. 2. Multi-voxel pattern analysis of fMRI signals together with machine learning methods revealed that the classification of emotional facial expression and facial identity occurs in different neural substrates of the human brain: the amygdala and posterior superior temporal sulcus (STS) for the former and the fusiform face area and anterior inferior temporal cortex for the latter. 3. Thetaburst transcranial magnetic stimulation (TBS), which temporarily disrupts neural activity, delivered over the posterior STS reduced the neural response to dynamic faces (but not to bodies or objects) in the posterior STS, anterior STS and amygdala, compared to TBS delivered over the vertex, indicating a cortico-amygdala pathway via the STS for dynamic face perception in humans. 4. Intranasal administration of oxytocin, a neuropeptide and potential treatment for autism, selectively altered fMRI responses to emotional expressions in monkeys, significantly reducing responses to both fearful and aggressive faces in face-responsive regions while leaving responses to appeasing and neutral faces unchanged, thereby explaining the beneficial effects of oxytocin on social cognition. 5. Pharmacological inactivation combined with fMRI in monkeys demonstrated that the functional network among the face-processing regions is hierarchically organized: activation of the amygdala by faces depends on inputs from the anterior temporal lobe face regions, whereas activation of these anterior regions depends on inputs from more posterior temporal lobe face regions. 6. Detection of configural face differences by humans led to stronger activation relative to featural face differences in the posterior parietal cortex (PPC), and transcranial magnetic stimulation centered on PPC impaired their performance on configural but not featural difference detections, indicating that spatial mechanisms within the PPC are necessary for configural face processing and, more broadly, for veridical face perception. 7. Patients with Moebius syndrome, a rare genetic neurological disorder characterized by facial paralysis, showed an impairment in their ability to recognize emotional expressions in others, indicating that the perception of emotional expressions depends on the ability to produce those expressions oneself. 8. The pattern of eye movements in monkeys reveals that, like humans, they experience face pareidolia, the experience of perceiving faces on inanimate objects, indicating that this illusion is driven by a broadly-tuned face detection mechanism that we share with other species.