For the past two decades, there has been a controversy over the purpose of the fusiform face area (FFA), located in the fusiform gyrus, in the brain. Neuroscientists have been debating whether the FFA is activated by faces for evolutionary or expertise reasons. The supporters of the minority view “do not believe that the FFA is specialized for face processing and have rather proposed that face processing is mediated by numerous regions of the brain” (Slotnick). In class, we discussed eight studies that had mixed views.
For example, Nancy Kanwisher and Doris Tsao have been big proponents of the majority view. Kanwisher et al. (1997) was one of the early studies to find a region in the fusiform gyrus in 12 of 15 participants that responded more strongly to faces than object stimuli (Figure 2). The data showed that the FFA is specifically involved in the perception of faces since higher peaks of signal change occur during face epochs than during nonface epochs, such as houses (Figure 3). Tsao et al. (2006) tested cell response in monkey M1 and monkey M2 to 96 images of faces, bodies, fruits, gadgets, hands, and scrambled patterns. Their results showed that 97% of cells were face selective. However, they considered cells that were selectively inhibited by faces to be face selective too. If the scientists required an excitatory response to faces only, then about 90% of cells were face selective. Also, many cells gave significant responses to a few particular nonface objects (Figure 2A). This shows that the FFA does not respond only to faces.
Schalk et al. (2017) suggests that the FFA is causally involved in face perception only and that nearby color-preferring regions are causally involved in color perception only. Thus, “stimulation of the FFA does affect the perception of other stimuli beyond faces, but it does so by adding a face percept” (12287). However, the transcript excerpts from the patient’s report during electrical stimulation of electrodes show some bias in the way this study was conducted, which can make some of the results unreliable.
Frank Haist and James Haxby have been proponents of the minority view. First, Haist et al. (2010) do not support the hypothesis that the FFA and OFA are specialized for face processing. To their knowledge, they found the first report of face-equivalent activation of the FFA for nonface objects. Under individuation task conditions, the researchers found that diverse nonface objects, including watches, activate the FFA and OFA just as much as faces. Second, Haxby et al. (2001) propose that the FFA is specialized for expert visual recognition of individual exemplars from any object category, not just faces. The result of their study indicates that the representations of faces and objects in the ventral temporal cortex are widely distributed, and when the “analysis was further restricted to regions that responded maximally to single category (houses, faces, or cats) or a small number of categories, the patterns of response to other categories within these regions were still significantly distinct” (Figure 4).
David Coggan and Kalanit Grill-Spector had some mixed views. Coggan et al. (2016) argued that the neural representation in the ventral visual pathway is tightly linked to the statistical properties of the image. They hypothesized that if category-selective patterns are based on more basic image properties, similar patterns should be elicited by both intact and scrambled images. This turned out to be true. Their results showed that brain responses to intact images were better predicted by responses to locally scrambled images than those to globally scrambled images. On the other hand, Grill-Spector et al. (2004) suggests that the increase in FFA activation for “identified and/or detected stimuli compared to stimuli that were not detected was greater for faces than for all other stimulus categories tested” (556). Although the BOLD signal from the FFA was positively correlated with successful identification and detection of faces, it was also positively correlated with the identification and detection of birds. It is unclear whether the response was to bird faces or the perception of some nonface stimuli.
Tanaka, K. (1993) suggested that there is a sequential cortical pathway from V1 to TE and a backward pathway that originates from the TE. Also, they found that most cells in TE required moderately complex features for their activation (Fig 2). For example, figure 1 shows the gradual reduction of the complexity of the tiger head image. The elimination of the intermediate features of the tiger head did not reduce the magnitude of the response until the very end of the image decomposition.
Taking all these articles together, it is clear to me that the FFA responds strongly to faces. However, the FFA also has a minimal response to nonfaces, such as birds, watches, and round objects. If the FFA is specialized for face perception, there has to be an evolutionary reason behind it. Therefore, I would propose a study on how human infants and newborns recognize faces. Infants tend to recognize their parents, especially their mothers. There must be a neurological mechanism behind that. My methodology would be that I would measure the P170 to check for any signs of cortical specialization for faces on newborn babies and conduct the study from the day he/she is born until adolescence. My hypothesis is that the FFA is evolutionarily specialized for face perception and that that allows the infants to identify their parents’ faces. Of the infant’s life, I expect the brain to grow, leading to the generation of more neurons. There would be larger neural connections, as well as more areas in the brain which could respond to faces, potentially causing the FFA to respond minimally to nonfaces. My alternative hypothesis is that the FFA is not activated in newborns and infants at all.
Coggan, David D, et al. “Category-Selective Patterns of Neural Response in the Ventral Visual
Pathway in the Absence of Categorical Information.” NeuroImage, U.S. National Library
Grill-Spector, Kalanit, et al. “The Fusiform Face Area Subserves Face Perception, Not Generic
within-Category Identification.” Nature Neuroscience, U.S. National Library of
Medicine, May 2004.
Haist, Frank, et al. “Individuating Faces and Common Objects Produces Equal Responses in
Putative Face-Processing Areas in the Ventral Occipitotemporal Cortex.” Frontiers in
Human Neuroscience, Frontiers Research Foundation.
Haxby, J V, et al. “Distributed and Overlapping Representations of Faces and Objects in Ventral
Temporal Cortex.” Science (New York, N.Y.), U.S. National Library of Medicine, 28
Kanwisher, Nancy, et al. “The Fusiform Face Area: A Module in Human Extrastriate Cortex
Specialized for Face Perception.” Journal of Neuroscience, Society for Neuroscience, 1
Schalk, Gerwin, et al. “Facephenes and Rainbows: Causal Evidence for Functional and
Anatomical Specificity of Face and Color Processing in the Human Brain.” PNAS,
National Academy of Sciences, 14 Nov. 2017.
Slotnick, Scott D. “Chapter 2.” Controversies in Cognitive Neuroscience, 2012.
Tanaka, K. “Neuronal Mechanisms of Object Recognition.” Science (New York, N.Y.), U.S.
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Tsao, Doris Y, et al. “A Cortical Region Consisting Entirely of Face-Selective Cells.” Science
(New York, N.Y.), U.S. National Library of Medicine.