Fusiform face area
The fusiform face area (FFA) is a part of the human visual system that, it is speculated, is specialized for facial recognition, although there is some evidence that it also processes categorical information about other objects, in particular familiar ones. It is located in the fusiform gyrus (Brodmann area 37).
The FFA is located in the ventral stream on the ventral surface of the temporal lobe on the lateral side of the fusiform gyrus. It is lateral to the parahippocampal place area. It displays some lateralization, usually being larger in the right hemisphere.
The FFA was discovered and continues to be investigated in humans using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies. Usually, a participant views images of faces, objects, places, bodies, scrambled faces, scrambled objects, scrambled places, and scrambled bodies. This is called a functional localizer. Comparing the neural response between faces and scrambled faces will reveal areas that are face-responsive, while comparing cortical activation between faces and objects will reveal areas that are face-selective.
The human FFA was first described by Justine Sergent in 1992 and later named by Nancy Kanwisher in 1997 who proposed that the existence of the FFA is evidence for domain specificity in the visual system. More recently, it has been suggested that the FFA processes more than just faces. Some groups, including Isabel Gauthier and others, maintain that the FFA is an area for recognizing fine distinctions between well-known objects. Gauthier et al. tested both car and bird experts, and found some activation in the FFA when car experts were identifying cars and when bird experts were identifying birds. Studies have also suggested that the FFA may be composed of functional clusters that are at a finer spatial scale than prior investigations have measured. Recent evidence also shows that electrical stimulation of these functional clusters selectively distorts face perception, which is sound causal support for the role of these functional clusters in perceiving the facial image. However, the debate about the functional role of the FFA is ongoing.
A 2009 magnetoencephalography study found that objects incidentally perceived as faces, an example of pareidolia, evoke an early (165-millisecond) activation in the FFA, at a time and location similar to that evoked by faces, whereas other common objects do not evoke such activation. This activation is similar to a face-specific ERP component N170. The authors suggest that face perception evoked by face-like objects is a relatively early process, and not a late cognitive reinterpretation phenomenon.
One case study on prosopagnosia provided evidence that faces are processed in a special way. A patient known as C. K., who suffered brain damage as a result of a car accident, later developed object agnosia. He experienced great difficulty with basic-level object recognition, also extending to body parts, but performed very well at recognizing faces. A later study showed that C. K. was unable to recognize faces that were inverted or otherwise distorted, even in cases where they could easily be identified by normal subjects. This is taken as evidence that the fusiform face area is specialized for processing faces in a normal orientation.
Based on these advances, IBM in 2010 applied for a patent on how to extract mental images of human faces from the human brain. The proposed design builds on a feedback loop based on brain measurements of the fusiform gyrus area in the brain assuming that activation is proportional with facial familiarity.
Function and controversy
The fusiform face area (FFA) is a part of the brain located in the fusiform gyrus with a debated purpose. Some researchers believe that the FFA is evolutionary purposed for face perception. Others believe that the FFA discriminates between any familiar stimuli.
Psychologists debate whether the FFA is activated by faces for an evolutionary or expertise reason. The conflicting hypotheses stem from the ambiguity in FFA activation, as the FFA is activated by both familiar objects and faces. A study regarding novel objects called greebles determined this phenomenon. When first exposed to greebles, a person's FFA was activated more strongly by faces than by greebles. After familiarizing himself with individual greebles or becoming a greeble expert, a person's FFA was activated equally by faces and greebles. Likewise, children suffering from autism have been shown to develop object recognition at a similarly impaired pace as face recognition. Studies of late patients of autism have discovered that autistic people have lower neuron densities in the FFA This raises an interesting question, however: Is the poor face perception due to a reduced number of cells or is there a reduced number of cells because autistic people seldom perceive faces? Asked simply: Are faces simply objects with which every person has expertise?
There is evidence supporting the FFA's evolutionary face-perception. Case studies into other dedicated areas of the brain may suggest that the FFA is intrinsically designed to recognize faces. Other studies have recognized areas of the brain essential to recognizing environments and bodies. Without these dedicated areas, people are incapable of recognizing places and bodies. Similar research regarding prosopagnosia has determined that the FFA is essential to the recognition of unique faces. However, these patients are capable of recognizing the same people normally by other means, such as voice. Studies involving language characters have also been conducted in order to ascertain the role of the FFA in face recognition. These studies have found that objects, such as Chinese characters, elicit a high response in different areas of the FFA than those areas that elicit a high response from faces. This data implies that certain areas of the FFA have evolutionary face-perception purposes.
Evidence from infants
The FFA is underdeveloped in children and does not fully develop until adolescence. This calls into question the evolutionary purpose of the FFA, as children show the ability to differentiate faces. Two-year-old babies have been shown to prefer the face of their mother. Although the FFA is underdeveloped in two-year-old babies, they have the ability to recognize their mother. Babies as early as three months old have shown the ability to distinguish between faces. During this time, babies exhibit the ability to differentiate between genders, showing a clear preference for female faces. It is theorized that, in terms of evolution, babies focus on women for food. Infants do not appear to use this area for the perception of faces; however, given that the adult human brain has been studied far more extensively than the infant brain, and that infants are still undergoing major neurodevelopmental processes, it may simply be that the FFA is not located in anatomically familiar area. It may also be that activation for many different percepts and cognitive tasks in infants is diffuse in terms of neural circuitry, as infants are still going under large periods of neurogenesis and neural pruning; this may make it more difficult to distinguish the signal, or what we would imagine as visual and complex familiar objects (like faces), from the noise, including static firing rates of neurons, and activity that is dedicated to a different task entirely than the activity of face processing. Infant vision involves only light and dark recognition, recognizing only major features of the face, activating the amygdala. These findings question the evolutionary purpose of the FFA.
Evidence from emotions
Studies into what else may trigger the FFA validates arguments about its evolutionary purpose. There are countless facial expressions humans use that disturb the structure of the face. These disruptions and emotions are first processed in the amygdala and later transmitted to the FFA for facial recognition. This data is then used by the FFA to determine more static information about the face. The fact that the FFA is so far downstream in the processing of emotion suggests that it has little to do with emotion perception and instead deals in face perception.
Recent evidence, however, shows that the FFA has other functions regarding emotion. The FFA is differentially activated by faces exhibiting different emotions. A study has determined that the FFA is activated more strongly by fearful faces than neutral faces. This implies that the FFA has functions in processing emotion despite its downstream processing and questions its evolutionary purpose to identify faces.
- Sergent J, Ohta S, MacDonald B (Feb 1992). "Functional neuroanatomy of face and object processing. A positron emission tomography study". Brain 115 (1): 15–36. doi:10.1093/brain/115.1.15. PMID 1559150.
- Kanwisher N, McDermott J, Chun MM (Jun 1, 1997). "The fusiform face area: a module in human extrastriate cortex specialized for face perception". J Neurosci. 17 (11): 4302–11. PMID 9151747.
- Gauthier I, Skudlarski P, Gore JC, Anderson AW (Feb 2000). "Expertise for cars and birds recruits brain areas involved in face recognition". Nat Neurosci. 3 (2): 191–7. doi:10.1038/72140. PMID 10649576.
- Weiner KS, Grill-Spector K (Oct 2010). "Sparsely-distributed organization of face and limb activations in human ventral temporal cortex". NeuroImage 52 (4): 1559–73. doi:10.1016/j.neuroimage.2010.04.262. PMID 20457261.
- Parvizi J, Jacques C, Foster BL, Witthoft N, Rangarajan V, Weiner KS, Grill-Spector K (Oct 2012). "Electrical stimulation of human fusiform face-selective regions distorts face perception". J Neurosci 32 (43): 14915–20. doi:10.1523/jneurosci.2609-12.2012. PMID 23100414.
- Hadjikhani N, Kveraga K, Naik P, Ahlfors SP (February 2009). "Early (N170) activation of face-specific cortex by face-like objects". Neuroreport 20 (4): 403–7. doi:10.1097/WNR.0b013e328325a8e1. PMC 2713437. PMID 19218867.
- Behrmann M, Moscovitch M, Winocur G (October 1994). "Intact visual imagery and impaired visual perception in a patient with visual agnosia". J Exp Psychol Hum Percept Perform 20 (5): 1068–87. doi:10.1037/0096-1522.214.171.1248. PMID 7964528.
- Moscovitch M, Winocur G, Behrmann M (1997). "What is special about face recognition? Nineteen experiments on a person with visual object agnosia and dyslexia but normal face recognition". J Cogn Neurosci 9 (5): 555–604. doi:10.1162/jocn.19126.96.36.1995.
- IBM Patent Application: Retrieving mental images of faces from the human brain
- Gauthier, I; Behrmann M Tarr MJ (1999). "Can Face Recognition Really be Dissociated from Object Recognition?". Journal of Cognitive Neuroscience 11 (4): 349–70. doi:10.1162/089892999563472. PMID 10471845.
- Scherf, S; Behrmann M Minshew N Luna B (April 2008). "Atypical Development of Face and Greeble Recognition in Autism". Journal of Child Psychiatry 49 (8): 838–47. doi:10.1111/j.1469-7610.2008.01903.x.
- van Kooten, IA; Palmen SJ, von Cappeln P, Steinbusch HW, Korr H, Heinsen H, Hof PR, van Engeland H, Schmitz C. (April 2008). "Neurons in the Fusiform Gyrus are Fewer and Smaller in Autism". Brain 131 (4): 987–99. doi:10.1093/brain/awn033.
- Gazzaniga, Michael; Ivry, Richard B.; Mangun, George R. (2014). Cognitive Neuroscience: The Biology of the Mind (4th ed.). New York City: W.W. Norton Company Inc. p. 247. ISBN 978-0-393-91348-4.
- Epstein, Russell; Kanwisher, Nancy (April 1998). "A cortical representation of the local visual environment". Nature 392 (6676): 598–601. doi:10.1038/33402. PMID 9560155.
- Downing, Paul; Yuhong Jiang; Miles Shuman; Nancy Kanwisher (September 2001). "A Cortical Area Selective for Visual Processing of the Human Body". Science 293 (5539): 2470–2473. doi:10.1126/science.1063414. PMID 11577239.
- Liu, J; Kanwisher N Harris A (2010). "Perception of Face Parts and Face Configuration: an fMRI Study". Journal of Cognitive Neuroscience 22 (1): 203–11. doi:10.1162/jocn.2009.21203. PMC 2888696. PMID 19302006.
- Prieto, EA; Caharel S Henson R Rossion B (2011). "Face-sensitivity Despite Right Lateral Occipital Brain Damage in Acquired Prosopagnosia". Frontiers in Human Neuroscience 5: 138. doi:10.3389/fnhum.2011.00138.
- Fu, S; Chunliang F Shichun G Yuejia L Raja P (2012). "Neural Adaptation Provides Evidence for Categorical Differences in Processing of Faces and Chinese Characters: an ERP Study of the N170". In Barton, Jason Jeremy Sinclair. PLoS One 7 (7): e41103. doi:10.1371/journal.pone.0041103. PMC 3404057. PMID 22911750.
- Bushnell, I.W.R. (2001). "Mother's Face Recognition in Newborn Infants: Learning and Memory". Infant and Child Development 10: 67–74. doi:10.1002/icd.248.
- Goldstein, Bruce (2013). Sense and Perception. Belmont, CA: Cengage Lerning. p. 91. ISBN 978-1133958499.
- Quinn, P.C.; Yahr J, Kuhn A. Slater A.M. Pascalils O. (2002). "Representation of the Gender of Human Faces by Infants: a Preference for Female". Perception 31 (9): 1109–21. doi:10.1068/p3331. PMID 12375875.
- Adolphs, R (April 2002). "Neural Systems for Recognizing Emotion". Current Opinions in Neurobiology 12 (2): 169–71. doi:10.1016/S0959-4388(02)00301-X.
- Guyer, Amanda; Monk, Christopher S. McClure-Tone, Erin B. Nelson, Eric E. Roberson-Nay, Roxann Adler, Abby D. Fromm, Stephen J. Leibenluft, Ellen Pine, Daniel S. Ernst, Monique (July 2010). "A Developmental Examination of Amygdala Response to Facial Expressions". Journal of Cognitive Neuroscience 20 (9): 1565–82. doi:10.1162/jocn.2008.20114. PMC 2902865. PMID 18345988.
- McKone et al., Trends in Cognitive Science, 2007
- Carlson, Neil R., Physiology of Behavior, 9th ed., 2007. ISBN 0-205-46724-5
- Bukach, C. M., I. Gauthier, and M. Tarr. 2006. Beyond faces and modularity: The power of an expertise framework. TRENDS in Cognitive Sciences 10:159-166.