Prosopagnosia, The Inability To Recognize Human Faces
It is very easy to believe that our visual system works by giving us reliable information about the external environment and that the brain is simply a receptacle for these images that tell us about what is happening in the world. However, the truth is that our nervous system has a very active role in processing this information so that it is coherent and makes sense.
The prosopagnosia It is a phenomenon that serves to remind us of this fact.
In short, it is about a failure of our nervous system whose consequence is that whoever experiences it is not able to recognize human faces. This means that despite having perfect eyes and being able to collect all the visual information related to a person’s face, it is not able to detect the patterns that make that face unique. In short: we see the face but we don’t recognize it.
Prosopagnosia is a type of visual agnosia since there are several types of neurological disorders in which what is seen is not recognized in a normal way by the brain. It is also one of the best-known types of agnosia thanks to, among other people, the recently deceased neurologist Oliver Sacks, who spoke about his experience with patients with visual agnosia in one of his most famous books: The man who mistook his wife for a hat.
How do people with prosopagnosia perceive faces?
People with prosopagnosia perceive faces as an image similar to something blurry, and are able to notice the existence of the typical organs of a face (eyes, nose, etc.) but not their exact location within the whole. However, there are cases in which they can recognize some characteristics of the faces of a few people, or be better at roughly perceiving the faces of certain groups (people of a certain sex, or with Asian features, etc.). ).
prosopagnosia does not make it impossible to recognize someone since people with this neurological disorder can identify others by their way of walking, their clothes, their hair…
What are the causes of prosopagnosia?
Prosopagnosia can be due to lesions in specific areas of the brain, but it can also be a condition that you are born with. It is believed that the part of the brain that functions abnormally in people with this disorder is the fusiform gyrusan area of ​​the cerebral cortex located in the temporal lobe, near the temples. Thanks to the fusiform gyrus we are extremely sensitive to all the subtleties that a human face can contain, and also thanks to it we have an unprecedented propensity to see faces in all kinds of things, including inanimate objects (these “illusions” are called pareidolias) .
When the fusiform gyrus or the neural networks that connect this area with other parts of the brain function abnormally, This can translate into an inability to detect the visual patterns necessary to “see” a face as a whole.
The brain has mechanisms to overcome this condition
However, in a certain sense the brain does receive visual information about faces, so other areas of the nervous system can process this information subconsciously. This explains why people with prosopagnosia show emotional activation when seeing the faces of close people (their mother, their friends, etc.), even if they do not consciously recognize them. This occurs because, although the fusiform gyrus does not work well, part of the visual information is processed in parallel by the limbic system, responsible for triggering emotional responses.
