Neurophysiology of Face Perception and Social Information Processing

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Face images courtesy of the Face-Place Database Project, Copyright 2008, Michael J. Tarr.

Face perception of brain involves a series of neural processes that enable and facilitate the perception, recognition, and interpretation of the face, particularly the human face. While face perception allows humans to readily recognize faces from other non-face objects and to distinguish individual identities based on face, it also facilitates processing social information by enabling us to read emotions and make impression from faces. This wiki page summarizes brain areas involved in general face processing and neural basis of face perception that entails social information processing.


Neuroanatomy and physiology of face perception

Figure 1. Brain areas implicated in face perception: the occipital face area (OFA), fusiform face area (FFA), and the superior temporal sulcus (fSTS).[2]

Face perception involves diverse and extensive areas in the brain. After an initial stage of visual analysis in occipital lobe, the visual information of facial features travels through two parallel neural streams. One is a ventral pathway, which includes portions of fusiform gyrus and inferior temporal cortex, dedicated to discriminating faces from non-face objects or processing invariant aspects of faces like an individual identity. Another pathway is more dorsal sectors of the temporal lobe, including the superior temporal sulcus (STS), and they are found to process variant facial features such as facial expressions and movements. The ventral stream is linked to anterior temporal lobe and hippocampal area, which takes charge in semantic and episodic knowledge, and the dorsal stream is linked to amygdala and other limbic systems for analyzing emotions, multisensory areas for integrating facial movements and sensory inputs, and parietal lobe for directing spatial attention to facial movements. While these neural pathways work in parallel, they interact with each other as well to give feedback to preceded processes and thus to facilitate face perception process (see Figure 1)[1].


Occipital face area (OFA)

Occipital face area (OFA) is an area located in the inferior occipital gyrus. OFA is active especially during an early stage of face detection, and its major role is to recognize individual pieces of facial parts like eyes, nose, and mouth as separate constructs, rather than as a whole[3]. A study using BOLD fMRI mapping that observed the brain activation in response to the visual perception of facial parts showed that OFA is activated when a single part of face (e.g., a nose) is presented separately, and that when facial parts are presented in combination, OFA activation is greater for a combination of related facial features like two eyes than other groupings of parts[4].

A finding from a study using a TMS simulation further supports the notion that OFA plays a critical role in the recognition of individual face features. Pitcher et al.[5] administered TMS stimulation to the right OFA immediately after participants saw two faces to be compare to each other, and they showed impairment in comparing the appearance of face parts (“are those the same eyes that I just saw? ”), rather than comparing their arrangements (“are those eyes closer together than they were?”), and no impairment was found for non-face objects (e.g., houses).

Fusiform face area (FFA)

Figure 2. Activation at FFA in response to different sets of stimuli [6]

While OFA is activated in response to individual facial features, fusiform face area (FFA), located in the lateral middle fusiform gyrus, responds to holistic identities of a human face and how facial features are configured[4]. FFA was found to show greater activation in response to a whole than a scrambled face, full front view of a face rather than a house, and a partial presentation of a human face than a human hand[6], suggesting that FFA is involved in the selective perception of human face, with preference to an intact rather than a disorganized face (see Figure 2). Also, FFA activation was correlated with within-category identification performance regarding human faces, but not with the one for non-face objects[7]. Stronger FFA activation was observed for detecting the presence of faces and distinguishing individual identities of specific faces, but not for viewing or identifying identities of non-face objects (e.g., cars seen by car experts).

Further causal link between FFA and face perception can be found from a study using electrical brain stimulation. When the FFA of a patient was stimulated by electrical charge, the patient reported a “metamorphosed” appearance of the face, but not to a non-face object, which suggests that FFA stimulation cause face-specific perceptual distortion (see related video clip)[8].

Superior temporal sulcus (fSTS)

Figure 3. Face-selective regions responding to face stimuli (LO: lateral occipital area, FFA: fusiform face area, OFA: occipital face area)[4]

Both OFA and FFA are involved in recognizing faces from non-face objects (see Figure 3) and processing invariant aspects of faces like facial features or individual identities of faces. Conversely, superior temporal sulcus (fSTS), separating the superior temporal gyrus from the middle temporal gyrus, is involved in perceiving and analyzing changeable aspects of faces such as eye gaze or facial movements [9]. In an fMRI study, viewing moving eyes or mouths activated fSTS area, while moving radial background activated brain regions other than fSTS[10], suggesting that fSTS is preferentially attuned to movements of facial features. A surgical removal of fSTS in rhesus monkeys resulted in impaired accuracy at perceiving frontal eye gaze[11], providing further evidence of the causal link between fSTS and facial movement perception.

Face perception with integrating social information

Beyond perceiving the presence of a face or detecting individual identities or facial movements, people can also extract more complicated information from faces that carries social implications. Rapid face processing in neural circuitry in combination with social information processing in other brain regions facilitates individuals’ immediate cognitive or behavioral responses in social or interpersonal contexts.

Emotion recognition

While the visual processing of facial expressions and movements is implicated in some of the areas in fSTS, the perception and recognition of emotional expression of face are represented in other regions within the limbic system including amygdala and orbitofrontal cortex. Numerous studies have revealed the role of amygdala in processing of fearful facial expression. Lesions of the amygdala are found to cause deficits in the recognition of fearful facial expressions[12], and direct electrical stimulation on amygdala would produce fearful emotional responses[13]. Recently, further studies have also investigated amygdala activation in response to emotional expressions other than fear. An event-related fMRI study showed that the activation of amygdala and fusiform cortex was evident for high intensities of all emotional faces of disgust, fear, happiness, and sadness[14].

There are evidences that suggest the connection between amygdala and FFA. When emotional faces (i.e., fearful faces) were presented and correctly identified by participants, increased activity in the fusiform gyrus was observed along with amygdala responses[15]. Also, such enhanced fusiform gyrus activity was found to disappear with amygdala damage in the ipsilateral hemisphere[16], further supporting that emotion recognition in face perception process involves the interaction between amygdala and FFA.

Impression formation

Figure 4. Examples of face stimuli for face perception study on trustworthiness and dominance.[25]

People use information from physical features and nonverbal behaviors to form impressions of individuals. Such impression formation process is implicated in face perception, as personal attributes can be inferred from appearance of facial features or subtle facial expressions.

Trustworthiness

A series of studies have mapped out brain areas involved in perception of trustworthiness (see Figure 4 for examples of stimuli). In an event-related fMRI study, increased activity in amygdala and right insula was observed in response to faces that were judged to be untrustworthy[17], and further evidence of amygdala’s involvement in trustworthiness perception can be found from a study with bilateral amygdala damage, where patients with amygdala damage tend to judge untrustworthy faces as more trustworthy[18].

Attractiveness

Several fMRI studies have identified brain regions that respond to different levels of facial attractiveness, and found the involvement of reward-related areas. When young heterosexual males were rating faces of attractive females, greater activation of brain regions in reward circuitry and a particular enhancement in nucleus accumbens (NAcc) [19]. Attractive faces were also found to produce activation of medial orbitofrontal cortex (mOFC), a region involved in representing reward value of a stimulus[20]. These findings altogether suggest that viewing attractive faces works similar to responding to reward neurologically.

Intergroup face perception and racial biases

Figure 5. Composite correlation maps displaying regions where magnitude of activation to Black vs. White faces is correlated with implicit racial attitude measures.[22]

For more information about intergroup face perception in social cognitive neuroscience, see Intergroup Face Perception.


Perception of faces of different groups, especially of different race groups, and subsequent stereotypes or biases are also implicated in brain regions and their neural underpinnings. FFA is found to exhibit differential activations towards the faces of one’s own or other races[21]. When European American or African American participants were presented with target faces of either European American or African American, FFA activation was greater for the faces that matched with one’s own race, while participants showed enhanced recognition memory for same-race target faces as well. One of the possible explanations of this finding is that greater familiarity with and subsequent advantage in individuating the faces of one’s own race might drive stronger neural responses to same-race faces.

An fMRI study has also shown that amygdala activity in response to novel African American faces is positively correlated with implicit racial bias in Caucasian participants as measured by Implicit Associate Test (IAT) and startle eyeblink responses (see figure 5). The finding indicates that greater implicit racial prejudice predicts greater difference in amygdala activation between Black faces and White faces. However, further research also suggested that when the given other-race faces are familiar to observers[23], or have averted rather than direct gaze[24], the correlations become weaker.

References

  1. Purves, D. (2008). Principles of cognitive neuroscience. Sunderland, Mass: Sinauer Associates.
  2. Downing, P. E. (2007). Face Perception: Broken into Parts. Current Biology, 17(20), R888.
  3. Pitcher, D.; Walsh, V., & Duchaine, B. (2011). "The role of the occipital face area in the cortical face perception network". Experimental Brain Research 209 (4): 481–493.
  4. Arcurio, L.R.; Gold, J.M., & James, T.W. (2012). "The response of face-selective cortex with single face parts and part combinations". Neuropsychologia 50 (10): 2454–2459.
  5. Pitcher, D., Walsh, V., Yovel, G., & Duchaine, B. (2007). TMS to the right occipital face area impairs face part processing in the first 100 milliseconds after stimulus presentation. Curr Biol, 17, 1568-1573.
  6. Kanwisher, N., McDermott, J., & Chun, M. M. (1997). The fusiform face area: a module in human extrastriate cortex specialized for face perception. The Journal of Neuroscience, 17(11), 4302-4311.
  7. Grill-Spector, K., Knouf, N., & Kanwisher, N. (2004). The fusiform face area subserves face perception, not generic within-category identification. Nature neuroscience, 7(5), 555-562.
  8. Parvizi, J., Jacques, C., Foster, B. L., Withoft, N., Rangarajan, V., Weiner, K. S., & Grill-Spector, K. (2012). Electrical stimulation of human fusiform face-selective regions distorts face perception. The Journal of Neuroscience, 32(43), 14915-14920.
  9. Liu J, Harris A, Kanwisher N. (2010). Perception of face parts and face configurations: An fmri study. Journal of Cognitive Neuroscience. (1), 203–211.
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  11. Campbell, R., Heywood, C. A., Cowey, A., Regard, M., & Landis, T. (1990). Sensitivity to eye gaze in prosopagnosic patients and monkeys with superior temporal sulcus ablation. Neuropsychologia, 28(11), 1123-1142.
  12. Adolphs, R., Tranel, D., Damasio, H., & Damasio, A. (1994). Impaired recognition of emotion in facial expressions following bilateral damage to the human amygdala. Nature, 372(6507), 669-672.
  13. Halgren, E. (1982). Mental phenomena induced by stimulation in the limbic system. Human neurobiology, 1(4), 251.
  14. Winston, J. S., O'Doherty, J., & Dolan, R. J. (2003). Common and distinct neural responses during direct and incidental processing of multiple facial emotions. Neuroimage, 20(1), 84-97.
  15. Williams, M.A., et al. (2008). Stimulus-driven and strategic neural responses to fearful and happy facial expressions in humans. European Journal of Neuroscience, 27, 3074-3082.
  16. Vuilleumier, P., & Pourtois, G. (2007). Distributed and interactive brain mechanisms during emotion face perception: evidence from functional neuroimaging. Neuropsychologia, 45(1), 174-194.
  17. Winston, J. S., Strange, B. A., O'Doherty, J., & Dolan, R. J. (2002). Automatic and intentional brain responses during evaluation of trustworthiness of faces. Nature neuroscience, 5(3), 277-283.
  18. Adolphs, R., Tranel, D., & Damasio, A. R. (1998). The human amygdala in social judgment. Nature, 393(6684), 470-474.
  19. Aharon, I., Etcoff, N., Ariely, D., Chabris, C. F., O'Connor, E., & Breiter, H. C. (2001). Beautiful faces have variable reward value: fMRI and behavioral evidence. Neuron, 32(3), 537-551.
  20. O’Doherty, J., Winston, J., Critchley, H., Perrett, D., Burt, D. M., & Dolan, R. J. (2003). Beauty in a smile: the role of medial orbitofrontal cortex in facial attractiveness. Neuropsychologia, 41(2), 147-155.
  21. Golby, A. J., Gabrieli, J. D., Chiao, J. Y., & Eberhardt, J. L. (2001). Differential responses in the fusiform region to same-race and other-race faces. Nature neuroscience, 4(8), 845-850.
  22. Phelps, E. A., O'Connor, K. J., Cunningham, W. A., Funayama, E. S., Gatenby, J. C., Gore, J. C., & Banaji, M. R. (2000). Performance on indirect measures of race evaluation predicts amygdala activation. Journal of Cognitive Neuroscience, 12(5), 729-738.
  23. Walker, P. M., Silvert, L., Hewstone, M., & Nobre, A. C. (2008). Social contact and other-race face processing in the human brain. Social Cognitive and Affective Neuroscience, 3(1), 16-25.
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