Researchers Identify Neurons in the Visual Cortex of Humans Responding to the Face


Avraham slapped his face and laughed, when he said to himself, "Can a child be born of a hundred-year-old man, or can Sara give birth to a child at the age of ninety?" Genesis 17:17 (The Israel Bible ™)

Although intensive research on us can recognize the faces of friends and relatives that we have not seen for years or celebrities we have never met, how the brain actually resolves remains a mystery.

Our world will be far different – and much poorer and more confusing – if everyone has the same face. Thanks to our parent genes that were revealed to us, everyone except identical siblings looked different and their faces revealed important information. Unfortunately, among crazy people, the ability to recognize the faces of people they had known for decades was greatly disturbed.

Most of us can recognize a famous person's face even if it only appears a split second or the face of an old college friend even after decades of not seeing it. Many of us can feel other people's moods based solely on facial expressions. Often, we can ascertain whether someone can be trusted by only seeing his face.

A study has just been published at Neurology, medical journal from the American Academy of Neurology, identified for the first time neurons in the human visual cortex that selectively respond to the face. This research was conducted by Dr. Vadim Axelrod, head Cognition and Awareness Laboratory at the Multidisciplinary Gonda (Goldschmied) Brain Research Center at Bar-Ilan University, working with the team from the Institut du Cerveau et de la Moelle Épinière and the Pitié-Salpêtrière Hospital led by Prof. Lionel Naccache.

The researchers showed that neurons in the visual cortex (around the Fusiform Face Area) responded much more strongly to the face than city landscapes or objects. The brain's response is much more energetic when the person sees famous actors or politicians than when he sees the Louvre in Paris, the Taj Mahal in Agra, India, scissors or backpacks or, for that matter, faces unknown to the participants in the experiment. In additional experiments, neurons showed the selectivity of faces for human and animal faces that appeared in the film (clip from Charlie Chaplin Circus)

"In the early 1970s, Prof. Charles Gross and colleagues found neurons in the visual cortex of ape monkeys that respond to the face. In humans, facial selective activity has been extensively investigated, primarily using non-invasive tools such as functional magnetic resonance imaging (fMRI) and electroencephalograms, "explained Axelrod, lead author of the paper.

"Surprisingly, facial neurons in the posterior temporal visual cortex have never been identified before in humans. In our study, we had a very rare opportunity to record nerve activity in a single patient while micro-electrodes were implanted around the Fusiform Face Area – the most important facial selective region of the human brain. "

Perhaps the most famous neuron that responds to the face is the so-called "Jennifer Aniston cell," neurons in the medial temporal lobe that respond to images different from certain people (eg, Jennifer Aniston in original studies published in Natural by Quiroga and colleagues in 2005). "But the neurons in the visual cortex that we report here are very different from the neurons in the medial temporal lobe," said Axelrod. "First, neurons in the visual cortex respond strongly to all types of faces, regardless of the person's identity. Second, they respond much earlier. In particular, while in our case, a strong response can be observed in 150 milliseconds to show a picture, "Jennifer Aniston cells" usually need 300 milliseconds or more to respond. "

These results provide unique insight into the functioning of the human brain at the cellular level during facial processing. This finding also helps bridge the understanding of cross-species face mechanisms (such as between monkeys and humans). "This is really interesting," researcher Bar-Ilan concluded, "that after nearly half a century since the discovery of facial neurons in ape monkeys, it is now possible to show similar neurons in humans."


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