Imagine you’re at a coffee shop. You decide to fix your hair in the reflection of the window. You start to think that this wasn’t the best location to try to fix it, because your reflection seems a bit distorted. After another couple of seconds, you stop moving and realize that your reflection is not mirroring you. Staring back at you is another person around your age with similar hair. They seem utterly confused why you had just been intently staring at them and frantically messing with your hair. How could you possibly explain to them that you had thought they were your reflection?

This scenario is one that the famous late neuroscientist Dr. Oliver Sacks actually faced when attempting to fix his beard one day (5). He was a professor of neurology and psychiatry at Columbia University, and has talked in detail about his diagnosis of prosopagnosia, commonly known as face blindness. Prosopagnosia is a neurological disorder in which people cannot recognize faces, and there are varying degrees of it (4).

Prosopagnosia affects around 2.5% of the population (1). Even though it isn’t incredibly common, there’s a very, very good chance somebody you know has it and might not even realize. People often just think they’re just pretty bad at recognizing faces. For those who have it, it can be socially crippling. Sadly, there is no cure, but people can often use non-face related cues to help with identifying a person (such as, “hey, this must be my neighbor John because that’s his dog”) (6).

So, before diving into prosopagnosia, how does facial recognition even work? A cognitive psychologist would now explain to you bottom-up and top-down processes. Both of these processes interact to guide visual recognition, but they are also how we take in our environment on a day to day basis.

• Bottom-up processing refers to taking in surrounding sensory cues as they are presented and then working towards a bigger picture.
• Top-down processing relies on prior knowledge and information stored in one of our sensory systems. We work from seeing the bigger pictures towards finding the smaller details.

The other important types of processing are holistic and parallel. Holistic facial processing has more support, but eye tracking studies show that humans still pay the most attention to the eyes, nose, and mouth when looking at a face (2).

• Parallel processing is the idea that we engage in multiple processes concurrently.
• Holistic processing says we see things as a whole and not just the individual parts.

Ok, great. We’ve established some important aspects of how facial recognition works. Now, what about the brain activity and regions involved? Before I discuss this, I want to preface this by saying there are other areas involved, and so this is not a comprehensive list; however, the following regions are considered to play some of the most important parts.

 

With that said, let’s now talk about the brain regions that play a key role: the lateral fusiform gyrus (or the fusiform face area), and the occipital face area (3). The fusiform gyrus is a fold in the brain that appears to coordinate neural systems controlling facial perception (7). The occipital face area is a region in the inferior occipital gyrus that plays an important part of facial processing (7).

Time to dive into some possible reasons as to why prosopagnosia occurs. As mentioned earlier, the right fusiform gyrus is incredibly important in facial recognition. This means that if it is damaged or has an abnormality, prosopagnosia might result. A stroke, traumatic brain injury, or certain neurodegenerative diseases might also cause it. It is also possible that a congenital disorder present at birth could cause prosopagnosia (4).

In the past, there have been autopsies of patients with prosopagnosia to try to see what brain regions are changed. This has revealed some really interesting information. Almost all of these patients had damage in the fusiform gyrus and lesions in the right visual-association cortex (specifically on the underside of the occipitotemporal cortex) (2). Pretty fascinating stuff.

So, to end this, I just want to reiterate two key points. First, facial recognition is a pretty complicated, VERY important thing in our lives. And two, prosopagnosia is one of the possible outcomes resulting from problems within facial recognition areas.

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References:

1. Corrow, S., Dalrymple, K., & Barton, J. (2016). Prosopagnosia: current perspectives. Eye Brain. DOI: 10.2147/EB.S92838.
2. Piepers, D., Robbins, R. (2012). Review and Clarification of the Terms “holistic,” “configural,” and “relational” in the Face Perception Literature. Front Psychol, 3(559). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3571734/.
3. Pitcher, D., Walsh, V. & Duchaine, B. (2011). The role of the occipital face area in the cortical face perception network. Exp Brain Res, 209(481). DOI: 10.1007/s00221-011-2579-1
4. “Prosopagnosia Information Page.” (2018). National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services. https://www.ninds.nih.gov/Disorders/All-Disorders/Prosopagnosia-Information-Page.
5. Sacks, Oliver. (2010) “Face-Blind.” The New Yorker. https://www.newyorker.com/magazine/2010/08/30/face-blind.
6. “Strangers in the Mirror.” (2010). Radiolab, WYNC Studios. https://www.wnycstudios.org/story/91967-strangers-in-the-mirror.
7. Ward, T., Bernier, R. (2013). Face Perception. Encyclopedia of Autism Spectrum Disorders. DOI:10.1007/978-1-4419-1698-3