In the 1960s the grandmother’s ‘neuron theory’ was postulated, which comes to say that in our brain there would be a neuron capable of recognizing the face of each of our loved ones. Thus, we would have a special neuron for our mother, another for our father, for our grandmother, etc. A hypothesis that was nothing more than an attempt to understand the complexity of our brain and the process by which our memory combines its memories with the information we receive from our senses in the present moment.
Since then, scientists have discovered many sensory neurons specialized in processing facial information, as well as other memory cells dedicated to storing data from our personal encounters. But the mythical ‘grandmother’s neuron’ has never been found, that hybrid cell capable of combining vision and memory.
Now, a new work published in the journal Science describes a new type of neurons that are located in the temporal region of the brain that links the perception of the face with long-term memory. It is not exactly that ‘grandmother’s neuron’, since, instead of a single cell, it is a whole population of neurons that, collectively, are capable of remembering faces and making us feel that flash of recognition when we meet each other. someone whose face reminds us of a loved one.
The Rockefeller University team of scientists used functional magnetic resonance imaging to study the temporal regions of the brains of two Rhesus monkeys and recorded electrical signals from neurons while showing the macaques images of faces of three different types: familiar , that they had seen in person, strangers, and that they had seen only in virtual form.
The scientists found that neurons in this region are highly selective, responding much more strongly to familiar faces. In addition, this discrimination was done in a very short time. The results also revealed that the cells responded more strongly to the faces of acquaintances in person, much more than to faces they had only seen through screens. “This may indicate the importance of meeting someone in person,” explains neuroscientist Sofia Landi, first author of the article. “Given the current trend towards virtualization of relationships, it is important to note that the faces we have seen on a screen may not evoke the same neural activity as the faces we meet in person.”
The findings constitute the first evidence for a hybrid brain cell, similar to the legendary grandmother’s neuron. Cells in the temporal region behave like sensory cells, with reliable and rapid responses to visual stimuli. But they also act as memory cells that respond only to stimuli that the brain has seen before, in this case, familiar individuals, reflecting a change in the brain as a result of past encounters. But the cells are not, strictly speaking, ‘grandmother’s neurons ‘, since instead of one cell encoding a single familiar face, the cells in this region appear to function in groups, collectively.
In the future, the findings may also have clinical implications for people with prosopagnosia or difficulty distinguishing a familiar face. “People with facial blindness often suffer from depression. At worst they can’t even recognize their close relatives,” says Winrich Freiwald, professor of neuroscience and behavior at Rockefeller University. “This discovery is the first brick to design strategies that allow us to help them in the future.”