Tag Archive | hippocampus

“Memory is built on concept neurones”

So, here’s the interview to Rodrigo Quian Quiroga, who came recently to give a talk at the PRBB. The title “The Jenifer Anniston neurone” was interesting… the content was much more so!

This interview was published in the PRBB monthly newspaper, Ellipse.

You can also read an earlier post about his talk here.

 

Figuring out how the brain works is the obsession of Rodrigo Quian, professor at the University of Leicester (UK). This challenge led him to apply his physics training and a PhD in maths to neuroscience. With the discovery of the “Jennifer Aniston neurone”, or concept cells, it seems we have taken a step towards the understanding of memory.

 

 

How can we “see” neurones?

We work on patients with epilepsy requiring hippocampus surgery. As part of this they have electrodes attached to the brain for several hours. This allows us to talk to them and detect how the neurones respond to stimuli we present them with.

Why the Jennifer Aniston neurone?

We did experiments where we showed patients people close to them like relatives and celebrities. The first neurone I found responded to pictures of Jennifer Aniston. It was a shock to discover that somewhere in the brain are neurones that respond in such a specific way to abstract concepts.

Did it only respond to photos?

It responded to various photos of Aniston, images as different in colour and format as we were able to find. The same with her name when written or spoken. Specifically, to the ‘concept’ of Jennifer Aniston. We found neurones that responded to different famous people depending on the person. The only neurones that did not respond were in an autistic patient.

One neurone per concept?

If I could find one neurone that responded to Jennifer Aniston, there must be more because if it was the only one, the probability of me finding it among the thousands of neurones in that area is practically zero. There has to be a network of neurones that encode a concept. These concept cells can quickly generate associations, so there are neurones that respond to two concepts, but they are always related to one another. This is a key mechanism for generating memories. I think they are the building blocks of memory and the link between perception and memory. This is a radically different idea to what was believed until now, that the basis of memory was distributed networks of millions of neurones.

Can you locate complex thoughts like phobias?

Often a complex thought is an association of simple thoughts. My old mentor at Caltech, Christof Koch, said it was necessary to break down the difficult problem of consciousness into related problems that are simpler and easier to attack. The consciousness of self is a very complex thing. One must first understand how the flow of consciousness works. That is, that one thing makes me think about another thing and that about another and so on. This can be studied in the neurones generating associations between two concepts and, from the moment we have made this association, we can see if the neurone also responds to the association and encodes it. In a few tests we have found that these concept cells begin to respond to the association we have created.

What other experiments are you working on?

We want to know if neurone response changes according to the presentation of the stimulus, for example the exposure time to the photos. The results demonstrate that neural response is closely related to the conscious perception of the patient. That is, if the patient believes that he has seen something, then the neurone is activated. In fact, it is even possible to predict beforehand when neurones will be activated and know what image a patient is looking at only from the neurone records.

 

The New Cajal Era

The New Cajal Era

More than 100 years have passed after the first contributions made by Santiago Ramón y Cajal to the neural network theory. Nowadays neuroscientists take advantage of innovative tools to study neural circuits in order to understand complex behaviours.

This image by David D’Amico, from the group on neurobehavioral phenotyping of mouse models of disease at the CRG, shows the hippocampus of a transgenic mouse expressing yellow fluorescent protein (YFP) in specific subsets of central neurons. This type of tansgenic mice help scientists to understand neural networks in both physiological and pathological conditions.

The Jennifer Aniston neuron

Rodrigo Quian Quiroga

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!

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!

Effects of cannabis on the hippocampus

Effects of cannabis at the hippocampus

In this image provided by Emma Puighermanal (Neuropharmacology lab, UPF) and obtained by Xavier Sanjuan, from the microscopy service of the UPF, shows a cut of the hippocampus of a mouse. It has been labelled against the kinase p-p70S6K (red), the dendritic marker MAP2 (blue) and the cannabinoide receptor CB1 (green). After administering Δ9-tetrahidrocannabinol (THC), the main psychoactive component of marijuana, the signalling pathway for mTOR/ p70S6K is activated in the hippocampus. This pathway is responsible for the amnesic effects of cannabis.

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