No, we don’t mean to say that Rachel from “Friends” has only one nerve cell… This was the title of the talk Rodrigo Quian Quiroga, from the University of Leicester, gave at the PRBB a couple of weeks ago. This physicist did a PhD in maths and then turned to neuroscience, something that fascinates him. “I can see you. Isn’t this amazing?”, he said to start the talk. As the Chilean researcher said, we can all remember and have emotions. How do neurons do that? This is what Quian Quiroga has been trying to understand for the last 10 years, and he was invited by the Pasqual Maragall Foundation (FPM) to the PRBB to tell us about his latest research into a particular type of neurons at the hippocampus, which he calls ‘concept cells’.
He discovered them by doing single cell recordings in epilepsy patients who were subject to surgery to remove a specific area of the hippocampus. During 1 or 2h, the researcher had time to do some tests, with the patient awake. He showed them hundreds of unrelated pictures, and checked if the sight of these images was activating some neurons. In a specific patient, he found a neuron that fired every time the patient saw an image of Jennifer Aniston. Also, it wasn’t a specific image of Jennifer Aniston, but any picture of her. Or the sound of her voice, or her name written or spoken. Basically, this neuron responded to the ‘concept’ of Jennifer Aniston!
But the American actress isn’t the only one who has a neuron just for herself. In different patients, Quiroga found neurons responding to different concepts, always concepts that were familiar to the patient: mostly he discovered other celebrities, such as Maradona or Hally Berry, but he even found a patient with ‘concept neurons’ firing at pictures of himself. He found only one person who didn’t seem to have these neurons, and the patient turned out to be autistic – someone who cannot think abstract.
He then discovered that these neurons don’t fire to a single concept, but are able to make associations and fire to related concepts. Thus, the Jennifer Aniston neuron could also fire, although less strongly, to images of her friend Phoebe in the popular TV series.
How durable is the ‘memory’ of these cells? Will a neuron that fires for Brad Pitt today still do so in 10 years? The scientist thinks this depends on how familiar the person is with the concept and his relation to it. In any case, these cells are, he thinks, the building blocks for explicit memory functions, and the neural substrate to make associations. We probably all have thousands of these cells in the hippocampus, and the most familiar a concept is, the more neurons we will have encoding for it. If one of these neurons fires to 3 or 4 different concepts, and another one fires to one of those plus 5 new ones, the neurons might activate each other and create networks of related concepts, which would build our memory.
A fascinating story that will surely bring more surprises. Stay tuned for Quian Quiroga’s research!