Do I Know You?

Yesterday, when I was studying for the upcoming Psychology test, I stumbled across a disease associated with recognition on the first page of Chapter 4. This impairment is known as prosopagnosia, something that was described through the story of Heather Sellers, a woman who cannot recognize faces. So, I decided to research this disease. Here is what I learned: 

Prosopagnosia, also called face blindness, is an impairment in the recognition of faces. It is often accompanied by other types of recognition impairments (place recognition, car recognition, facial expression of emotion, etc.) though sometimes it appears to be limited to facial identity. Not surprisingly, prosopagnosia can create serious social problems. Prosopagnosics often have difficulty recognizing family members, close friends, and even themselves. They often use alternative routes to recognition, but these routes are not as effective as recognition via the face.

Reports of prosopagnosia date back centuries, but Bodamer's report (1947) of two individuals was a momentous paper in that he described the symptoms and declared it to be distinct from agnosia. He referred to their condition as prosopagnosia, which he coined by combining the Greek word for face (prosopon) with the medical term for recognition impairment (agnosia). Since that time, more than a hundred case reports have been published.

Everyone sometimes has trouble recognizing faces, and it is even more common for people to have trouble remembering other people's names. Prosopagnosia is much more severe than these everyday problems that everyone experiences. Prosopagnosics often have difficulty recognizing people that they have encountered many times. In extreme cases, prosopagnosics have trouble recognizing even those people that they spend the most time with such as their spouses and their children.

One of the telltale signs of prosopagnosia is great reliance on non-facial information such as hair, gait, clothing, voice, and other information. Prosopagnosics also sometimes have a difficult time envisioning the facial appearance of acquaintances. One of the most common complaints of prosopagnosics is that they have trouble following the plot of television shows and movies, because they cannot keep track of the identity of the characters.

Most of the cases of prosopagnosia that have been documented have been due to brain damage suffered after adulthood from head trauma, stroke, and progressive diseases. The following are examples of acquired prosopagnosia: these individuals had normal face recognition abilities that were then impaired. It seems probable that more cases of acquired prosopagnosia have been found for two reasons. First, their impairment with faces is usually quite evident to these individuals, because they have experienced normal face recognition in the past and so they quickly notice their impairment. Second, because these individuals have had brain damage, they are in contact with medical doctors who have assessed their face recognition abilities. 

Conversely, in cases of developmental prosopagnosia, the beginning of prosopagnosia transpired before developing normal face recognition abilities (adult levels of face recognition are reached during teenage years). Developmental prosopagnosia has been used to refer to individuals whose prosopagnosia is genetic in nature, individuals who experienced brain damage prior to experience with faces (prenatal brain damage or immediate brain damage), and individuals who experienced brain damage or severe visual problems during childhood. However, these causes should be differentiated, because they are different paths to prosopagnosia and so probably result in different types of impairment; and are referred to as genetic prosopagnosia, preexperiential prosopagnosia, and postexperiential prosopagnosia, respectively. In some cases, it may be difficult to determine the cause of prosopagnosia, but many times individuals will either know that family members are also prosopagnosic or be aware of potential incidents that may have resulted in brain damage.

Individuals with developmental prosopagnosia often do not realize that they are unable to recognize faces as well as others. They have never recognized faces normally so their impairment is not apparent to them. It is also difficult for them to notice, because individuals with normal face recognition rarely discuss their reliance on faces. As a result, there are a number of individuals who have not recognized their prosopagnosia until well into adulthood. It is possible that this condition is more common than acquired prosopagnosia.

There are a range of explanations for prosopagnosia.These explanations suggest that the system necessary for normal face recognition is not working properly. However, the explanations differ in their characterization of the impaired procedures. It appears that prosopagnosia actually refers to a number of different types of impairments, so no one explanation will account for all cases of prosopagnosia.

So, how do we recognize faces? Well, let's start with the beginning of vision. Light waves enter the eye through the cornea, the protective film around the eye. Then, it travels to the iris, which adjusts light intake, and the pupil. Afterwards, the light is transferred to the lends, which causes the light to bend onto the retina through a process called accommodation. In the retina, the light waves are transduced in the rods and cones which trigger the horizontal, bipolar, and amacrine cells to pass the information to the ganglion cells. The axons of ganglion cells leave the eye and form the optic nerve, which transports the information to the thalamus, which distributes the neural message to the visual cortex. 

In the brain, the feature detection cells respond to specific and different features, such as edges, lines, and angles. Then, in parallel processing, teams of brain cells process combined information about color, movement, form, and depth, simultaneously. And in the final process, recognition, perception occurs. The brain interprets the constructed image based on information from stored images. 

Thanks to an area on the underside of the brain's right hemisphere, we can recognize a human face. An individual with prosopagnosia senses the same sensations we receive when looking at a friend, and their perception is almost normal. Thus, they may recognize people from their hair, their gait, their voice, or particular physique, just not their face. 

Source: https://www.faceblind.org/research/