Liset Menéndez de la Prida, neuroscientist: ‘It’s not normal to constantly seek pleasure; it’s important to be bored, to be calm’

Neuroscientist Liset Menéndez de la Prida says that human beings have the most powerful organ in the known universe: the brain. “It’s a fabulous weapon. It allows us to transform the world, understand ourselves, ask ourselves what we are… All animals have a brain that allows them to survive, but we have done something much more powerful with it: we not only survived, but we have created a culture, a civilization… And there’s an enormous journey ahead: we might blow ourselves up before then through our own fault, but we have an unparalleled capacity for transformation and understanding,” she says enthusiastically via videoconference from her office at the Cajal Institute headquarters in Madrid, where she investigates how the brain constructs memory by navigating space and time, and how these processes are altered by illness.

Menéndez de la Prida is the director of the new Cajal Neuroscience Center of Spain’s national research center (CSIC), and has just published Cerebro, espacio y tiempo (in English, Brain, Space and Time), a book in which she unpacks how our ancient brain positioning system allows us to locate the here and now, recall a past memory, construct another mental time in dreams, or transport ourselves into the future by imagining an experience that has not yet occurred.

In a conversation with EL PAÍS, the 54-year-old scientist, trained in physics and with a doctorate in neuroscience, breaks down the neural intricacies of memory and life, while also addressing the challenges facing neuroscience — and humanity — amid the “frantic” pace of technological change. “The brain is a reflection of who we are. It is our strength and our burden. Two sides of the same coin,” she says.

Question. You say that we have a neural GPS. What is that?

Answer. It’s a triangulation system implemented in a biological way. It allows us to pinpoint a location, generate a map of the space, of the elements that pass by. We have a series of neurons that specialize in representing different locations in space or elements associated with those locations.

Q. How do we remember, for example, the way home?

A. What happens first is that you have a model of space: your brain has developed the concepts of wall, street, traffic light, window. And, as you explore space, you develop a specialization in certain neurons that respond to the presence of these elements. As you explore and experience things, a flow of neural activity is generated that reflects these elements and links their activity together to establish connections. These connections generate sequences that reflect what you have experienced. From this, you create a representation, infer a location, and generate a memory of that linked sequence of events.

Q. In the book, you argue that memory is the most important function of the brain. How is it constructed?

A. We tend to prioritize emotional aspects. This triggers a response in the brain, helping neurons to connect more firmly. When the photographer came to take my photos for this interview, he told me that he had edited his memory of February 23 [the 1981 Spanish coup attempt]: he thought he had seen it on television, but that wasn’t true [it was only broadcast on the radio]. Since he was young, his memories were of his brother and father and what he saw later on television. That’s pure neuroscience: when you relive that event, your memory ends up generating a representation that you believe is real, but it’s not perfect. That editing of memory, those emotional elements, and those relationships between what happened and what you recall, determine the fragility of the representation.

Q. So memory is never truly faithful to the events you experienced?

A. Exactly. You manipulate it. Memory has a compositional aspect because it’s a composition of sequences of neural activity. And since those same neurons were activated in other sequences, in another experience, when you recall them, it’s very easy for them to trigger the activations of other sequences. Memory is always labile, editable. Human beings don’t want to deceive themselves; there’s no intention behind it, but depending on the emotional nature of things, it happens.

Q. In the book, you also talk a lot about the role of time. How does the brain organize time?

A. All experience is ordered in time and space. Time is the succession of things. There is physical time that is measurable, objective. But mental time doesn’t align with physical time in a one-to-one way, because in mental time, what you are doing is experiencing what you are living. Now, for example, I am paying attention to this conversation, not to what is happening in the street, and that changes my sense of time. That’s why it’s fickle: it’s embedded within the representation itself and the elements that pass by, and therefore, it is memory. Time is memory.

Q. We also travel through time when we dream. What is the purpose of dreaming?

A. Dreaming serves to reactivate past experiences, to cleanse the memory, to edit it. It serves to recombine representations. And it helps us generate that capacity for creativity because in dreams the brain’s experience is not limited to real space: you can imagine you are flying and actually fly because reality doesn’t hold you back in that flow. Your brain freely rehearses other recombinations, other sequences, other chains of events. And from there come representations that you hadn’t perceived while awake.

Q. In the book, you give the example of a shrew that manages to escape a snake and feels an automatic sense of relief, and is, as you say, “flooded with dopamine.” And that’s when neural connections are strengthened, the memory chain… How do all those external variables — like TikTok or ultra-processed foods, which constantly immerse us in artificial dopamine — distort our brains?

A. We can’t be constantly exposed to stimulation, because otherwise we’ll need more and more for our neurons to respond. A life where you’re constantly seeking pleasure isn’t normal. It’s important to be bored, to be calm, and to let the [neural] system relax and reorganize itself without that constant barrage of stimulants that prevents it from functioning at its natural, normal range.

Q. The brain is not evolving as rapidly as our way of life has in the last 100 years. What consequences will that have?

A. Biologically, each generation pays the price for the consequences, and culturally, we pass them on to the next. But I don’t see a cataclysm of civilization. I see that we are moving forward, that we are trying to understand the world, and that we are trying to establish rules for living with one another.

Q. You say that the next evolution will be that of man and machine. What do you mean by that?

A. We are becoming increasingly hybridized with machines. New technologies are interfacing with the brain. It’s difficult to imagine what the next technological leap will be, but given the current trend, it’s clear that brain-machine interfaces will be a major focus. This co-evolution is necessary because otherwise, a generation will pay the price.

Cognitive diseases are going to start increasing, those caused by pushing our cognitive system to its limits. We’re already beginning to see it: excessive attention, information overload, having to pay attention to many things at once… This shortens our attention span because our brain can’t maintain focus for very long periods.

Q. Do you foresee new diseases associated with our way of life?

A. Yes, that’s stress, anxiety, or cognitive load. Our ability to absorb, for example, work, reaches a limit at some point. That mental fatigue takes its toll on the brain. These are all functional alterations of a brain without underlying pathology, but they reflect the impact of a lifestyle.

Q. You say that the brain hides its secrets in the most unexpected places. What are the great mysteries it still holds?

A. Well, what is consciousness? How does all that mental activity make us aware that we are something in the world, that we are something in the eyes of others? These are the tough questions of neuroscience: the self, identity, the fragility of memory, why we lose our memories… Is there a limit to cognitive capacity, or is it infinite? How much can we learn or store in this gray matter?

Sign up for our weekly newsletter to get more English-language news coverage from EL PAÍS USA Edition