Why do some people face blindness?

For a long time, people didn't think that face blindness was a big deal. After all, it's just the ability to distinguish faces. However, as time goes by, more and more people find that in this case, face blindness is not just the inability to distinguish faces. Severe face blindness may even make it impossible to distinguish young and old, men and women by their faces, or even feel each other's emotions after seeing a face.

To understand face blindness, we must first understand how our eyes see things. At the bottom of the eye is a structure called retina. There are many photosensitive cells on this structure. Photoreceptor cell array projects nerve information to the visual cortex of our brain through a bundle of thick nerve fibers, and is processed into other information that our memory center and language center can understand by a group of complex nerve cells in the visual cortex. On this same road, any step of work is disturbed, which may lead to problems in our understanding and cognition of what we see. Since there is this cognitive dissonance, there must be a fixed area related to facial recognition in the brain, called fusiform gyrus, which is located at the bottom of the cerebral cortex. There are some nerve cells in this area that are specially used to deal with the cognition of the whole facial features.

Human recognition of facial features is highly specific. Even a very abstract facial symbol like J^_^ can stimulate the rapid response of fusiform gyrus's central nervous system. This is also the source of many legends similar to the human face on Mars.

Fortunately, eye movement tracking technology is very developed now. Through the tracking of eye movements, we can now know that when normal people look at their faces, their eyes always wander back and forth at the three key points of eyes, nose and mouth to quickly extract the basic features of faces. Eye movement patterns of face-blind people are different. His eyes will move aimlessly all over his face, and accordingly, when observing facial photos with magnetic resonance vibration, the active areas of brain nuclei are different.