Scientists discover a new class of memory cells for remembering faces
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The idea of a grandmother neuron first showed up in the 1960s as a theoretical brain cell that would code for a specific, complex concept, all by itself. One neuron for the memory of one's grandmother, another to recall one's mother, and so on. At its heart, the notion of a one-to-one ratio between brain cells and objects or concepts was an attempt to tackle the mystery of how the brain combines what we see with our long-term memories.
Scientists have since discovered plenty of sensory neurons that specialize in processing facial information, and as many memory cells dedicated to storing data from personal encounters. But a grandmother neuron -- or even a hybrid cell capable of linking vision to memory -- never emerged. "The expectation is that we would have had this down by now," Freiwald says. "Far from it! We had no clear knowledge of where and how the brain processes familiar faces."
Recently, Freiwald and colleagues discovered that a small area in the brain's temporal pole region may be involved in facial recognition. So the team used functional magnetic resonance imaging as a guide to zoom in on the TP regions of two rhesus monkeys, and recorded the electrical signals of TP neurons as the macaques watched images of familiar faces (which they had seen in-person) and unfamiliar faces that they had only seen virtually, on a screen.
The team found that neurons in the TP region were highly selective, responding to faces that the subjects had seen before more strongly than unfamiliar ones. And the neurons were fast -- discriminating between known and unknown faces immediately upon processing the image.
Interestingly, these cells responded threefold more strongly to familiar over unfamiliar faces even though the subjects had in fact seen the unfamiliar faces many times virtually, on screens. "This may point to the importance of knowing someone in person," says neuroscientist Sofia Landi, first author on the paper. "Given the tendency nowadays to go virtual, it is important to note that faces that we have seen on a screen may not evoke the same neuronal activity as faces that we meet in-person."
https://www.sciencedaily.com/releases/2021/07/210701140929.htm
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