杏吧原创

A man with a rare brain lesion may help increase our understanding of how we process faces. To him, the right half of every face looks as if it is melting. This could suggest that each brain hemisphere typically processes one half of the face.

The man, known as A.D., noticed three years ago that the faces he saw on TV were distorted, saying that they looked as if they were melting. He then discovered that when he looked in the mirror, his own face was also affected. In each case it was only the right half of a person鈥檚 face that was distorted. 鈥淓verything on the right side is longer, tighter and fallen,鈥� he told researchers.

Doctors then found that A.D. has a lesion in the fibres connecting the brain鈥檚 two hemispheres.聽By looking at the different experiences of people with brain lesions and those without, scientists can make an educated guess as to how that part of the brain is involved in typical neural processing. 鈥淚鈥檓 not saying our brains are all the same, but we do share a universal architecture,鈥� says Jorge Almeida at Coimbra University in Portugal.

The researchers showed A.D. pictures of 20 faces and 20 other objects, like a car and a bell. They found that distortions only occurred when he looked at faces. They also found that regardless of the angle or depth the faces were presented in, A.D. only ever saw the right half of the person鈥檚 face as if it was melting. This was true even when the faces were presented upside down.

These results suggest two new key aspects of typical face processing, says Brad Duchaine at Dartmouth College in New Hampshire, who worked on the study with Almeida.

鈥淲e already knew that faces were processed differently to other objects, but now we know that we automatically fit new faces into a template, so that we can compare it to other faces stored in our memories,鈥� he says. This would explain why A.D. always saw the same part of the face as distorted.

鈥淚t also suggests that the two halves of a face are processed in separate hemispheres at some point,鈥� says Duchaine. He speculates that this may increase visual processing speed, as we normally look at the middle of a person鈥檚 face and so each of our eyes initially takes in information from opposite sides of a face.

鈥淗umans may have a capacity to process the two face halves independently, in part because faces are symmetrical and are therefore redundant in information processing terms in some situations,鈥� says John Towler at Swansea University, UK.