Brains without a face
Association areas are a distinctive characteristic of human brain. Many animals have motor and sensory cortex which are similar to ours.
What happens in these association regions of our brain is a complex interpretation of inner and outer information, which basically results in our own behaviour.
In particular, the temporal association cortex plays a key role in the identification and recognition of complicated stimuli.
This is not a surprise, considering that here is also located the so-called ventral stream, where our brain processes shape and colour of what the eyes see. In particular, the temporal lobe is the site of V3 and V4 areas.
As for most of the other regions of human brain, the function of the temporal association lobe has been understood with the help of patients who present specific issues in this part.
Prosopagnosis has been crucial, in this very case. This condition consists in the inability to recognize people, even very familiar to us, such as parents and relatives, and it's frequently a consequence of damages in the right inferior temporal lobe.
A milestone in the study of prosopagnosis is the article "CAN WE LOSE MEMORIES OF FACES - CONTENT SPECIFICITY AND AWARENESS IN A PROSOPAGNOSIC", ETCOFF NL; FREEMAN R; CAVE KR, JOURNAL OF COGNITIVE NEUROSCIENCE 3 (1): 25-41.
Here is described the case of patient, L.H., who developed prosopagnosis as a consequence of a severe head injury. He could recognize common objects, whether someone was a friend or not and, according to. voice, way of walking, posture, etc., he could even recognize someone's identity. However, when he had to use his visual memory only, he was at a loss.
Studies on monkeys have revealed that in the inferior temporal lobe there are groups of neurons whose frequency of action potentials is hugely increased when another monkey's face is shown.
These cells have the organization of those, simpler, present in the visual primary cortex (V1) for detecting the orientation of objects. Both types describes functional columns. It's easy to understand that, while the columns in V1 are innate, those which deal with faces develop according to our experiences (which, here, means life).
Each column, for example, have cells which are sensitive to the orientation of the face.
Interestingly, the studies with rhesus have shown that these cells won't increase their activity if we show the monkey an image containing parts of a real face and others, taken from, say, tools, in order to create a fake.
What is still unknown is how our brain actually recognize the different faces, but it's possible that different groups of neurons react varying their potential, according to the differences of shapes of our visage.
