Know Your Brain: Fusiform Face Area
Where is the fusiform face area?
What is the fusiform face area and what does it do?
By the late 1990s, researchers had built up a fair amount of evidence that suggested there are parts of our brain that are especially active when we look at faces. This research led neuroscientists to hypothesize that certain neurons are specialized to process information about faces, and that these neurons are essential to normal face perception. According to this view, the parts of the brain involved in face perception might be distinct from the parts of the brain involved in perceiving other things like objects.
In 1997, researchers published a groundbreaking study that not only supported the idea of face-specific processing in the brain, but also added some important anatomical detail. The study, by Nancy Kanwisher and colleagues, used functional magnetic resonance imaging (fMRI) to identify areas of the brain that were highly active when participants looked at faces. In the process, the researchers found a region about the size of a blueberry on the inferior (bottom) surface of the temporal lobe that displayed a disproportionate amount of activity when participants viewed faces—but not when they viewed other things like houses, hands, or cars. In most patients, this activity was seen predominantly on the right side of the brain.
The data suggested to Kanwisher and her fellow researchers that this region—found in a gyrus known as the fusiform gyrus—was specialized for processing information about faces; they called it the fusiform face area, or FFA. The hypothesis that the FFA is a face-processing module aligned with previous imaging studies that had also linked face perception to this general area of the brain, as well as with cases of patients who had experienced damage to the FFA and subsequently developed a condition known as prosopagnosia, which involves an impairment in the ability to recognize faces.
Further studies also supported the hypothesis of Kanwisher et al. For example, an experiment with monkeys that recorded the activity of neurons in the FFA found that 97% of the neurons in the area were active in response to facial imagery, but not in response to images of things like objects or other body parts. And another study found that delivering short bursts of electrical charge to the FFA caused disruptions in the perception of faces. Today—over 20 years after the initial publication by Kanwisher et al. that coined the term fusiform face area—it’s safe to say there is convincing evidence that the FFA is involved in perceiving faces.
Nevertheless, there is still a great deal of debate about the details surrounding the anatomy and function of the FFA. For instance, some argue that while parts of the FFA may play a role in face perception, the region probably consists of multiple visual areas that should be considered as distinct (both anatomically and functionally) rather than as one structure devoted to face perception. Additionally, some argue that—rather than being localized primarily to the FFA—face recognition involves a network of brain regions that extends beyond just the FFA to include other parts of the occipital and temporal lobes as well. According to both of these perspectives, attributing such a large role in face perception to the FFA alone may be a bit of an oversimplification.
But probably the loudest critique of the idea that the FFA is a primary face-processing area of the brain is the suggestion that the FFA is not only specialized for the perception of faces, but also for the perception of all objects we have a high level of familiarity and experience with. This idea is sometimes referred to as the expertise hypothesis, and it suggests that the FFA is activated in response to faces because we are, to some degree, face experts. For example, one study found activity in the FFA to also be increased in response to objects like cars and birds, and the increase was correlated with the degree of expertise someone had in identifying these objects (birdwatchers and car aficionados displayed greater activity). Another study found the FFA to be active when chess experts viewed chess positions on a chessboard, and yet another found that experienced radiologists had more activity in the FFA when viewing x-rays than med students did.
The expertise hypothesis, however, has also faced its fair share of criticism. The studies supporting the expertise hypothesis have tended to be small, and often the effects seen in those studies have not been very large. Nevertheless, a 2019 analysis of the results of 18 studies found that, even when the methodological concerns stated above are taken into consideration, the evidence strongly favors the expertise hypothesis. Thus, the precise role of the FFA in face perception continues to be debated.
References (in addition to linked text above):
Burns EJ, Arnold T, Bukach CM. P-curving the fusiform face area: Meta-analyses support the expertise hypothesis. Neurosci Biobehav Rev. 2019;104:209-221. doi:10.1016/j.neubiorev.2019.07.003
Kanwisher N, McDermott J, Chun MM. The fusiform face area: a module in human extrastriate cortex specialized for face perception. J Neurosci. 1997;17(11):4302-4311. doi:10.1523/JNEUROSCI.17-11-04302.1997
Weiner KS, Grill-Spector K. The improbable simplicity of the fusiform face area. Trends Cogn Sci. 2012;16(5):251-254. doi:10.1016/j.tics.2012.03.003