Fusiform gyrus · Grey Matter

The fusiform gyrus is the long ridge on the underside of the temporal and occipital lobes where the visual system recognises complex shapes as particular things, above all faces and, in readers, written words.

Fusiform gyrus. The fusiform gyrus is the long ridge on the underside of the temporal and occipital lobes where the visual system recognises complex shapes as particular things, above all faces and, in readers, written words.

It runs along the lower surface of the brain, between the occipital pole and the front of the temporal lobe, at the end of the ventral visual stream that carries what-it-is information forward from the visual cortex. In 1997 Kanwisher and colleagues found a patch on it, larger on the right, that responds far more to faces than to other objects, the fusiform face area; a patch at the same height on the left responds to written words (the visual word form area) as reading is learned.

Damage to it, usually on the right or both sides, can cause prosopagnosia: faces are seen clearly but not recognised, even those of family, and people are identified by voice, gait or clothing instead.

Recognising a face is a circuit. The fusiform gyrus identifies the face, the anterior temporal lobe retrieves who the person is, the hippocampus retrieves where they were last met, and the amygdala gives the encounter its emotional weight.

Its face selectivity is partly learned. The area's preference strengthens through childhood, and expertise with other categories (cars, birds) recruits it too.

Questions: What happens in the brain when you recognise a friend's face in a crowd? The visual cortex extracts edges and features, and the fusiform face area on the underside of the temporal lobe (larger on the right) assembles them into a face and matches it to the faces it knows. The anterior temporal lobe retrieves who the person is, the hippocampus brings back where and when you last met, and the amygdala and reward circuits add the warmth or unease that belongs to that person. Damage to the fusiform region can leave someone seeing a face clearly and recognising nobody (prosopagnosia), and recognising friends by their voice instead.