Face recognition is particularly associated with a part of the temporal lobe called the fusiform gyrus. Although it’s controversial whether this area is specifically for faces, or is more generally specialised for perceptual expertise of which faces are just the most important example, it’s clear that it is key for understanding faces.
Cibu Thomas from Carnegie Mellon University discovered the problem by focusing on two major white matter tracts that link the fusiform area to other parts of the brain. Both have names that positively trip off the tongue – the inferior longitudinal fasciculus (ILF) and the inferior fronto-occipito fasciculus (IFOF). Thomas studied the tracts using a technique called diffusion tensor imaging (DTI), which measures the flow of water along their length.
The flowing water revealed severe problems with the structural integrity of both white matter tracts in the brains of prosopagnosics. Normal individuals didn’t show any problems, nor did areas of white matter in the prosopagnosics that connected areas completely unrelated to face processing.
In other words, the fibres that connect important perceptual areas in the brain may be much thinner in people who have problems recognising faces.
The image on the left shows the connections between the temporal and the occipital lobes in the participants with the condition and the controls.
As usual, the Not Exactly Rocket Science write-up is clear, concise and engaging, and if you’d like to know a bit more what it’s like to live without recognising faces The Guardian recently published a personal account of day-to-day life from someone with prosopagnosia who can’t even recognise himself in the mirror.