Scientists in the US have accurately reconstructed images of human faces by monitoring the responses of monkey brain cells. The brains of primates can resolve different faces with remarkable speed and reliability, but the underlying mechanisms are not fully understood. The researchers showed pictures of human faces to macaques and then recorded patterns of brain activity. The work could inspire new facial recognition algorithms, they report.
In earlier investigations, Professor Doris Tsao from the California Institute of Technology (Caltech) and colleagues had used functional magnetic resonance imaging (fMRI) in humans and other primates to work out which areas of the brain were responsible for identifying
faces. Six areas were found to be involved, all of which are located in part of the brain known as the inferior temporal (IT)
cortex. The researchers described these six areas as “face patches.” Further research showed that face patches were jammed with particular nerve cells (neurons) that emit signals more strongly when they’re presented with faces, rather than when they ‘see’ other objects.
The team members called these neurons ‘face cells’. Doris’s team came up with 50 different dimensions that could describe a face, such as the distance between the eyes, or the width of the hairline, as well as non-shape-related features such as skin tone. Then, they inserted electrodes into the brains of macaque monkeys so that they could record individual signals from single face cells within the face patches.
The results, published in the journal Cell, suggest that around 200 neurons encode different characteristics of a face. But when all are combined, the information contributed by each nerve cell
allows the macaque brain to build a clear image of someone’s face. “We’ve discovered that this code is extremely simple,” said Doris. “A practical consequence of our findings is that we can now reconstruct a face that a monkey is seeing by monitoring the electrical activity of only 205 neurons in the monkey’s brain.”
When placed side by side, photos that the monkeys were shown and faces recreated from their brain activity were nearly identical. Face cells from just two of the face patches - 106 cells in one patch and 99 cells in another - were enough to reconstruct the faces. Whatever its all about pratices
