Editing Face perception (section)

==Neuroanatomy==

=== Key areas of the brain ===
[[File:Fusiform face area face recognition.jpg|alt=A side-on image of an fMRI scan of a human brain.|thumb|A computer-enhanced fMRI scan of a person who has been asked to look at faces]]
Facial perception has neuroanatomical correlates in the brain.

The '''fusiform face area''' ([[Brodmann area#BA37,FusiformGyrus|BA37— Brodmann area 37]]) is located in the lateral fusiform gyrus. It is thought that this area is involved in holistic processing of faces and it is sensitive to the presence of facial parts as well as the configuration of these parts. The fusiform face area is also necessary for successful face detection and identification. This is supported by fMRI activation and studies on prosopagnosia, which involves lesions in the fusiform face area.<ref name="Liu">{{cite journal|last1=Liu|first1=Jia|last2=Harris|first2=Alison|last3=Kanwisher|first3=Nancy|date=January 2010|title=Perception of Face Parts and Face Configurations: An fMRI Study|journal=Journal of Cognitive Neuroscience|volume=22|issue=1|pages=203–211|doi=10.1162/jocn.2009.21203|pmc=2888696|pmid=19302006}}</ref><ref name="Rossion">{{cite journal|last1=Rossion|first1=B.|date=1 November 2003|title=A network of occipito-temporal face-sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing|journal=Brain|volume=126|issue=11|pages=2381–95|doi=10.1093/brain/awg241|pmid=12876150}}</ref><ref name="McCarthy 1997">{{cite journal |last1=McCarthy |first1=Gregory |last2=Puce |first2=Aina |author-link2=Aina Puce |last3=Gore |first3=John C. |last4=Allison |first4=Truett |date=October 1997 |title=Face-Specific Processing in the Human Fusiform Gyrus |journal=Journal of Cognitive Neuroscience |volume=9 |issue=5 |pages=605–610 |doi=10.1162/jocn.1997.9.5.605 |pmid=23965119 |s2cid=23333049 |hdl-access=free |hdl=2022/22741}}</ref><ref>{{Cite journal|last1=Baldauf|first1=D.|last2=Desimone|first2=R.|date=25 April 2014|title=Neural Mechanisms of Object-Based Attention|journal=Science|language=en|volume=344|issue=6182|pages=424–7|doi=10.1126/science.1247003|pmid=24763592|bibcode=2014Sci...344..424B|s2cid=34728448|issn=0036-8075|doi-access=free}}</ref><ref name=":15">{{Cite journal|last1=de Vries|first1=Eelke|last2=Baldauf|first2=Daniel|date=1 October 2019|title=Attentional Weighting in the Face Processing Network: A Magnetic Response Image-guided Magnetoencephalography Study Using Multiple Cyclic Entrainments|url=https://doi.org/10.1162/jocn_a_01428|journal=Journal of Cognitive Neuroscience|volume=31|issue=10|pages=1573–88|doi=10.1162/jocn_a_01428|pmid=31112470|hdl=11572/252722|s2cid=160012572|issn=0898-929X|hdl-access=free}}</ref>

The '''occipital face area''' is located in the inferior occipital gyrus.<ref name="Rossion" /><ref name=":15" /> Similar to the fusiform face area, this area is also active during successful face detection and identification, a finding that is supported by fMRI and MEG activation.<ref name="Liu" /><ref name=":15" /> The occipital face area is involved and necessary in the analysis of facial parts but not in the spacing or configuration of facial parts. This suggests that the occipital face area may be involved in a facial processing step that occurs prior to fusiform face area processing.<ref name="Liu" /><ref name=":15" />

The '''superior temporal sulcus''' is involved in recognition of facial parts and is not sensitive to the configuration of these parts. It is also thought that this area is involved in gaze perception.<ref name=":15" /><ref name="Campbell">{{cite journal|last1=Campbell|first1=R.|last2=Heywood|first2=C.A.|last3=Cowey|first3=A.|last4=Regard|first4=M.|last5=Landis|first5=T.|date=January 1990|title=Sensitivity to eye gaze in prosopagnosic patients and monkeys with superior temporal sulcus ablation|journal=Neuropsychologia|volume=28|issue=11|pages=1123–42|doi=10.1016/0028-3932(90)90050-x|pmid=2290489|s2cid=7723950}}</ref> The superior temporal sulcus has demonstrated increased activation when attending to gaze direction.<ref name="Liu" /><ref name=":15" /><ref name="Marquardt">{{cite journal|last1=Marquardt|first1=Kira|last2=Ramezanpour|first2=Hamidreza|last3=Dicke|first3=Peter W.|last4=Thier|first4=Peter|date=March 2017|title=Following Eye Gaze Activates a Patch in the Posterior Temporal Cortex That Is not Part of the Human 'Face Patch' System|journal=eNeuro|volume=4|issue=2|pages=ENEURO.0317–16.2017|doi=10.1523/ENEURO.0317-16.2017|pmc=5362938|pmid=28374010}}</ref>

During face perception, major activations occur in the extrastriate areas bilaterally, particularly in the above three areas.<ref name="Liu" /><ref name="Rossion" /><ref name=":15" /> Perceiving an inverted human face involves increased activity in the inferior temporal cortex, while perceiving a misaligned face involves increased activity in the occipital cortex. No results were found when perceiving a dog face, suggesting a process specific to human faces.<ref name=":92">{{cite journal|last1=Tsujii|first1=T.|last2=Watanabe|first2=S.|last3=Hiraga|first3=K.|last4=Akiyama|first4=T.|last5=Ohira|first5=T.|date=March 2005|title=Testing holistic processing hypothesis in human and animal face perception: evidence from a magnetoencephalographic study|journal=International Congress Series|volume=1278|pages=223–6|doi=10.1016/j.ics.2004.11.151}}</ref> Bilateral activation is generally shown in all of these specialized facial areas.<ref name="McCarthy">{{cite journal|last1=Andreasen|first1=N. C.|author2=O'Leary DS|author3=Arndt S|last4=Cizadlo|first4=T|last5=Hurtig|first5=R|last6=Rezai|first6=K|last7=Watkins|first7=GL|last8=Ponto|first8=LB|last9=Hichwa|first9=RD|display-authors=3|name-list-style=vanc|year=1996|title=Neural substrates of facial recognition|journal=The Journal of Neuropsychiatry and Clinical Neurosciences|volume=8|issue=2|pages=139–46|doi=10.1176/jnp.8.2.139|pmid=9081548}}</ref><ref>{{cite journal|last1=Haxby|first1=JV|last2=Horwitz|first2=B|last3=Ungerleider|first3=LG|last4=Maisog|first4=JM|last5=Pietrini|first5=P|last6=Grady|first6=CL|date=1 November 1994|title=The functional organization of human extrastriate cortex: a PET-rCBF study of selective attention to faces and locations|journal=The Journal of Neuroscience|volume=14|issue=11|pages=6336–53|doi=10.1523/JNEUROSCI.14-11-06336.1994|pmc=6577268|pmid=7965040}}</ref><ref>{{cite journal|last1=Haxby|first1=James V|last2=Ungerleider|first2=Leslie G|last3=Clark|first3=Vincent P|last4=Schouten|first4=Jennifer L|last5=Hoffman|first5=Elizabeth A|last6=Martin|first6=Alex|date=January 1999|title=The Effect of Face Inversion on Activity in Human Neural Systems for Face and Object Perception|journal=Neuron|volume=22|issue=1|pages=189–199|doi=10.1016/S0896-6273(00)80690-X|pmid=10027301|s2cid=9525543|doi-access=free}}</ref><ref>{{cite journal |last1=Puce |first1=Aina |author-link=Aina Puce |last2=Allison |first2=Truett |last3=Asgari |first3=Maryam |last4=Gore |first4=John C. |last5=McCarthy |first5=Gregory |date=15 August 1996 |title=Differential Sensitivity of Human Visual Cortex to Faces, Letterstrings, and Textures: A Functional Magnetic Resonance Imaging Study |journal=The Journal of Neuroscience |volume=16 |issue=16 |pages=5205–15 |doi=10.1523/JNEUROSCI.16-16-05205.1996 |pmc=6579313 |pmid=8756449}}</ref><ref>{{cite journal|last1=Puce|first1=A.|last2=Allison|first2=T.|last3=Gore|first3=J. C.|last4=McCarthy|first4=G.|date=1 September 1995|title=Face-sensitive regions in human extrastriate cortex studied by functional MRI|journal=Journal of Neurophysiology|volume=74|issue=3|pages=1192–9|doi=10.1152/jn.1995.74.3.1192|pmid=7500143}}</ref><ref>{{cite journal|last1=Sergent|first1=Justine|last2=Ohta|first2=Shinsuke|last3=Macdonald|first3=Brennan|date=1992|title=Functional neuroanatomy of face and object processing. A positron emission tomography study|journal=Brain|volume=115|issue=1|pages=15–36|doi=10.1093/brain/115.1.15|pmid=1559150}}</ref> However, some studies show increased activation in one side over the other: for instance, the right fusiform gyrus is more important for facial processing in complex situations.<ref name="McCarthy 1997" />

=== BOLD fMRI mapping and the fusiform face area ===
The majority of fMRI studies use [[Blood-oxygen-level-dependent imaging|blood oxygen level dependent]] (BOLD) contrast to determine which areas of the brain are activated by various cognitive functions.<ref>{{cite journal|last1=KannurpattiRypmaBiswal|first1=S.S.B.|title=Prediction of task-related BOLD fMRI with amplitude signatures of resting-state fMRI|journal=Frontiers in Systems Neuroscience|date=March 2012|volume=6|pages=7|doi=10.3389/fnsys.2012.00007|pmid=22408609|pmc=3294272|first2=Bart|last2=Biswal|first3=B|last3=Bharat |doi-access=free}}</ref>

One study used BOLD [[functional magnetic resonance imaging|fMRI]] mapping to identify activation in the brain when subjects viewed both cars and faces. They found that the [[occipital face area]], the fusiform face area, the [[superior temporal sulcus]], the amygdala, and the anterior/inferior cortex of the temporal lobe all played roles in contrasting faces from cars, with initial face perception beginning in the fusiform face area and occipital face areas. This entire region forms a network that acts to distinguish faces. The processing of faces in the brain is known as a "sum of parts" perception.<ref name="Gold 2012 427–434">{{cite journal|last=Gold|first=J.M.|author2=Mundy, P.J.|author3=Tjan, B.S.|title=The perception of a face is no more than the sum of its parts|journal=Psychological Science|year=2012|volume=23|issue=4|pages=427–434|doi=10.1177/0956797611427407|pmid=22395131|pmc=3410436}}</ref>

However, the individual parts of the face must be processed first in order to put all of the pieces together. In early processing, the occipital face area contributes to face perception by recognizing the eyes, nose, and mouth as individual pieces.<ref>{{cite journal|last=Pitcher|first=D.|author2=Walsh, V.|author3=Duchaine, B.|title=The role of the occipital face area in the cortical face perception network|journal=Experimental Brain Research|year=2011|volume=209|issue=4|pages=481–493|doi=10.1007/s00221-011-2579-1|pmid=21318346|s2cid=6321920}}</ref>

Researchers also used BOLD fMRI mapping to determine the patterns of activation in the brain when parts of the face were presented in combination and when they were presented singly.<ref name=Arcurio12>{{cite journal|last=Arcurio|first=L.R.|author2=Gold, J.M.|author3=James, T.W.|year=2012|title=The response of face-selective cortex with single face parts and part combinations|journal=Neuropsychologia|volume=50|issue=10|pages=2454–9|doi=10.1016/j.neuropsychologia.2012.06.016|pmc=3423083|pmid=22750118}}</ref> The occipital face area is activated by the visual perception of single features of the face, for example, the nose and mouth, and preferred combination of two-eyes over other combinations. This suggests that the occipital face area recognizes the parts of the face at the early stages of recognition.

On the contrary, the fusiform face area shows no preference for single features, because the fusiform face area is responsible for "holistic/configural" information,<ref name=Arcurio12/> meaning that it puts all of the processed pieces of the face together in later processing. This is supported by a study which found that regardless of the orientation of a face, subjects were impacted by the configuration of the individual facial features. Subjects were also impacted by the coding of the relationships between those features. This shows that processing is done by a summation of the parts in later stages of recognition.<ref name="Gold 2012 427–434" />

=== The fusiform gyrus and the amygdala ===
The fusiform gyri are preferentially responsive to faces, whereas the parahippocampal/lingual gyri are responsive to buildings.<ref name=Gorno01>{{cite journal|last1=Gorno-Tempini|first1=M. L.|last2=Price|first2=CJ|title=Identification of famous faces and buildings: A functional neuroimaging study of semantically unique items|journal=Brain|date=1 October 2001|volume=124|issue=10|pages=2087–97|doi=10.1093/brain/124.10.2087|pmid=11571224 |doi-access=free}}</ref>

While certain areas respond selectively to faces, facial processing involves many neural networks, including visual and emotional processing systems. While looking at faces displaying emotions (especially those with fear facial expressions) compared to neutral faces there is increased activity in the right fusiform gyrus. This increased activity also correlates with increased amygdala activity in the same situations.<ref name="Vuilleumier">{{cite journal|last1 = Vuilleumier|first1 = P|last2 = Pourtois|first2 = G|year = 2007|title = Distributed and interactive brain mechanisms during emotion face perception: Evidence from functional neuroimaging|journal = Neuropsychologia|volume = 45|issue = 1|pages = 174–194|doi=10.1016/j.neuropsychologia.2006.06.003|pmid = 16854439|citeseerx = 10.1.1.410.2526|s2cid = 5635384 }}</ref> The emotional processing effects observed in the fusiform gyrus are decreased in patients with amygdala lesions.<ref name="Vuilleumier"/> This demonstrates connections between the amygdala and facial processing areas.<ref name="Vuilleumier"/>

Face familiarity also affects the fusiform gyrus and amygdala activation. Multiple regions activated by similar face components indicates that facial processing is a complex process.<ref name="Vuilleumier"/> Increased brain activation in precuneus and cuneus often occurs when differentiation of two faces are easy (kin and familiar non-kin faces) and the role of posterior medial substrates for visual processing of faces with familiar features (faces averaged with that of a sibling).<ref>{{cite journal|last1=Platek|first1=Steven M.|last2=Kemp|first2=Shelly M.|title=Is family special to the brain? An event-related fMRI study of familiar, familial, and self-face recognition|journal=Neuropsychologia|date=February 2009|volume=47|issue=3|pages=849–858|doi=10.1016/j.neuropsychologia.2008.12.027|pmid=19159636|s2cid=12674158 }}</ref>

The object form topology hypothesis posits a topological organization of neural substrates for object and facial processing.<ref name=Ishai99>{{Cite journal|author1=Ishai A|author2=Ungerleider LG|author3=Martin A|author4= Schouten JL|author5=Haxby JV|title=Distributed representation of objects in the human ventral visual pathway|journal=Proc. Natl. Acad. Sci. U.S.A.|volume=96|issue=16|pages=9379–84|date=August 1999|pmid=10430951|pmc=17791|doi=10.1073/pnas.96.16.9379|bibcode=1999PNAS...96.9379I |doi-access=free}}</ref> However, there is disagreement: the category-specific and process-map models could accommodate most other proposed models for the neural underpinnings of facial processing.<ref>{{cite journal|last1=Gauthier|first1=Isabel|title=What constrains the organization of the ventral temporal cortex?|journal=Trends in Cognitive Sciences|date=January 2000|volume=4|issue=1|pages=1–2|doi=10.1016/s1364-6613(99)01416-3|pmid=10637614|s2cid=17347723 }}</ref>

Most neuroanatomical substrates for facial processing are perfused by the middle cerebral artery. Therefore, facial processing has been studied using measurements of mean cerebral blood flow velocity in the middle cerebral arteries bilaterally. During facial recognition tasks, greater changes occur in the right middle cerebral artery than the left.<ref>{{cite journal|last1=Droste|first1=D W|last2=Harders|first2=A G|last3=Rastogi|first3=E|title=A transcranial Doppler study of blood flow velocity in the middle cerebral arteries performed at rest and during mental activities.|journal=Stroke|date=August 1989|volume=20|issue=8|pages=1005–11|doi=10.1161/01.str.20.8.1005|pmid=2667197 |doi-access=free}}</ref><ref>{{cite journal|last1=Harders|first1=A. G.|last2=Laborde|first2=G.|last3=Droste|first3=D. W.|last4=Rastogi|first4=E.|title=Brain Activity and Blood flow Velocity Changes: A Transcranial Doppler Study|journal=International Journal of Neuroscience|date=January 1989|volume=47|issue=1–2|pages=91–102|doi=10.3109/00207458908987421|pmid=2676884 }}</ref> Men are right-lateralized and women left-lateralized during facial processing tasks.<ref>{{Cite journal|author=Njemanze PC|title=Asymmetry in cerebral blood flow velocity with processing of facial images during head-down rest|journal=Aviat Space Environ Med|volume=75|issue=9|pages=800–5|date=September 2004|pmid=15460633}}</ref>

Just as memory and cognitive function separate the abilities of children and adults to recognize faces, the familiarity of a face may also play a role in the perception of faces.<ref name="Gold 2012 427–434"/> Recording [[event-related potentials]] in the brain to determine the timing of facial recognition<ref name="Zheng 2012 1451–1461">{{cite journal|last1=Zheng|first1=Xin|last2=Mondloch|first2=Catherine J.|last3=Segalowitz|first3=Sidney J.|title=The timing of individual face recognition in the brain|journal=Neuropsychologia|date=June 2012|volume=50|issue=7|pages=1451–61|doi=10.1016/j.neuropsychologia.2012.02.030|pmid=22410414|s2cid=207237508 }}</ref> showed that familiar faces are indicated by a stronger N250,<ref name="Zheng 2012 1451–1461"/> a specific wavelength response that plays a role in the visual memory of faces.<ref>{{cite journal|last=Eimer|first=M.|author2=Gosling, A.|author3=Duchaine, B.|title=Electrophysiological markers of covert face recognition in developmental prosopagnosia|journal=Brain|year=2012|volume=135|issue=2|pages=542–554|doi=10.1093/brain/awr347|pmid=22271660|doi-access=free}}</ref> Similarly, all faces elicit the [[N170]] response in the brain.<ref>{{cite journal|last=Moulson|first=M.C.|author2=Balas, B.|author3=Nelson, C.|author4=Sinha, P.|year=2011|title=EEG correlates of categorical and graded face perception|journal=Neuropsychologia|volume=49|issue=14|pages=3847–53|doi=10.1016/j.neuropsychologia.2011.09.046|pmc=3290448|pmid=22001852}}</ref>

The brain conceptually needs only ~50 neurons to encode any human face, with facial features projected on individual axes (neurons) in a 50-dimensional "Face Space".<ref>{{cite journal|last1=Chang|first1=Le|last2=Tsao|first2=Doris Y.|date=June 2017|title=The Code for Facial Identity in the Primate Brain|journal=Cell|volume=169|issue=6|pages=1013–28.e14|doi=10.1016/j.cell.2017.05.011|pmid=28575666|pmc=8088389|s2cid=32432231}}</ref>