Editing Face perception (section)

=== 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>