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fMRI都显示了脸部选择性区域，在这些区域，脸部引起的fMRI信号比非脸部物体引起的更大。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.与正常猴子不同，双侧杏仁核受损的猴子没有表现出相对于物体的观看面孔或虚幻面孔的偏好，这表明杏仁核对于我们对面孔的最早专门反应至关重要，这一行为被认为是有效社交的先驱。 2.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利影响。 3.不同于腹侧流中的面部选择性区域都表现出对侧的视野偏向，而在后上颞沟(PSTS)中的面部选择性区域则没有，这表明该区域可能形成了解剖学上不同的视觉通路的一部分，该视觉通路优先处理运动的生物信息，如面部表情和人类运动。 4.位于人脑皮质侧面的类别选择区域(面部、身体和场景)更多地被运动激活，而位于腹侧的区域则不被激活，这提示了人脑皮质区域的新的组织原则。 5.与中性面孔相比，恐惧面孔引起的激活更大(称为配价效应)，这一发现贯穿于视觉皮质区域内的整个视野表征(即，不限于面孔的视网膜定位)，这一发现与杏仁核是配价效应的来源一致，因为杏仁核将广泛的投射发送回视觉皮质。 6.Moebius综合征(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情的能力受损，但他们识别身体运动产生的表情的能力并不受损，这表明对面部情绪表情的感知取决于自己产生这些表情的能力。 7.静息状态fMRI显示，与健康对照组相比，MOS患者的后部STS-杏仁核连接性较梭形脸部区-杏仁体连接性降低，提示MOS患者面部情绪表达加工的神经回路可能发生了改变。 8.脑磁图数据的Granger因果关系分析表明，在结构面孔加工过程中，背向流视觉区域向腹侧流视觉区发送信息，这表明视觉空间信息在结构面孔加工过程中被传递到面孔加工区域。 9.与猴子一样，在人类大脑皮层后部发现了几个曲率选择性区域，这些区域与面部选择性区域重叠，这表明面部选择性可能来自曲率选择性。

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, 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. Monkeys with bilateral amygdala lesions, unlike normal monkeys, showed no preference for viewing faces or illusory faces relative to objects, indicating that the amygdala is critical for our earliest specialized response to faces, a behavior thought to be a precursor for efficient social communication. 2. 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. 3. Unlike face-selective regions in the ventral stream, which all showed a contralateral visual field bias, that in the posterior superior temporal sulcus (pSTS) did not, indicating that this area may form part of a anatomically distinct visual pathway that preferentially processes moving biological information such as facial expressions and human movement. 4. Category-selective areas (for faces, bodies and scenes) located laterally in the human cortex were activated more by moving than by static visual stimuli (regardless of the object category), whereas those located ventrally were not, suggesting a new organizing principle for cortical areas in the human brain. 5. The greater activation evoked by fearful compared to neutral faces (termed the valence effect) was found throughout the entire visual field representation within visual cortical areas (that is, not confined to the retinotopic location of the faces), a finding consistent with the amygdala being the source of the valence effect inasmuch as the amygdala sends widespread projections back to visual cortex. 6. Patients with Moebius syndrome (MoS), a rare genetic neurological disorder characterized by facial paralysis, showed an impaired ability to recognize emotional expressions in others, but not in their ability to recognize expressions produced by body movements, indicating that the perception of facial emotional expressions depends on the ability to produce those expressions oneself. 7. Resting-state fMRI showed reduced posterior STS-amygdala connectivity relative to fusiform face area-amygdala connectivity in MoS compared to healthy controls, suggesting that the neurocircuitry underlying facial emotional expression processing may be altered in MoS. 8. Granger causality analysis of MEG data revealed that, during configural face processing but not during featural face processing, dorsal stream visual areas send information to ventral stream visual areas, indicating that visuospatial information is transmitted to face-processing regions during configural face processing. 9. As in monkeys, several curvature-selective regions of the posterior cerebral cortex were identified in humans that overlapped face-selective regions, suggesting that face selectivity might arise from curvature selectivity.