In monkeys, researchers have identified two new areas of the brain that facilitate the recognition of familiar faces. Scientists have known for some time that there is a network of brain regions for facial recognition, yet the underlying process for how primates distinguish between familiar and unfamiliar faces has remained elusive. One hypothesis is that familiar and unfamiliar face recognition use the same neural machinery, but with different efficiency. An alternative hypothesis is that separate neural systems are at play. In a new study, Sofia Landi and Winrich Freiwald confirm the latter. Using functional MRI, they studied the brain activity of four macaques as they were exposed to both familiar and unfamiliar faces, as well as familiar and unfamiliar objects. They observed two areas of the brain, the perirhinal cortex (PR) and one in the temporal pole (TP), that were specifically involved in recognizing personally familiar faces, but not the other three scenarios. The researchers even detected differences between when a monkey looked at a photo of an unfamiliar face several times and thus became visually familiar with that given face, compared to seeing photos of monkeys they have personally met. The authors then conducted a classic facial recognition experiment, where a face is initially blurred and transitions into focus, providing a gradient for recognition. Where other visual processing regions display consistent activity during the transition, the TP and PR circuits sporadically become active upon facial recognition.
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Science