Per què alguns records perduren per sempre?

Memories are an integral part of our lives, shaping who we are and how we perceive the world around us. From the first time you saw snow to a magical night of kings or the day your little brother was born, certain memories stay with us for a lifetime. But have you ever wondered how our brains store these memories long-term? A groundbreaking study conducted by a team of American researchers, published in Science Advances, has shed light on the biological mechanisms behind long-term memories. The key to this research lies in understanding the role of a molecule called KIBRA, which acts as a glue with other molecules, allowing memories to stabilize and solidify over time.

The process of how the brain stores memories is one of the fundamental questions that neuroscience has yet to definitively answer. However, the simplest explanation is that the brain restructures itself with each memory through the actions of synapses, where neurons communicate with each other to transmit information. It is in this process that memories are formed and stored.

„When a memory is formed, the connection between neurons changes,“ says Lluís Fuentemilla, a researcher at the University of Barcelona and the Bellvitge Biomedical Research Institute. „The brain prioritizes preserving memories related to strong emotions, whether they are good or bad,“ adds Raül Andero, an ICREA researcher at the Autonomous University of Barcelona. Neurons store information in memory in the form of two patterns: strong synapses and weak synapses. „For example, weak synapses would be what you ate ten weeks ago, and strong synapses, for example, when you rode a motorcycle for the first time,“ explains Andero. However, the molecules in synapses are unstable, constantly moving within neurons and wearing out. In fact, they are replaced within days or even hours. So how do memories remain stable over decades if the key element in the neuronal process is so mutable?

According to the research led by the University of New York, the answer to this question revolves around the molecule KIBRA, which is found in the kidney and the brain. Scientists conducted a study with laboratory mice and analyzed how this element interacts with other essential molecules for memory formation, such as the protein Mzeta (PKMzeta), which is crucial for generating memories but is also highly degradable. This allowed them to determine that KIBRA acts as a „persistent synaptic tag.“ In simple terms, it functions as a sticky tag that adheres to strong synapses and PKMzeta, maintaining memories even over long periods and preventing weak synapses from forming.

For Fuentemilla, it all comes down to a signaling process. Humans, unlike artificial intelligence, are capable of learning something with a single experience. „The formation of memories involves very rapid structural changes that succeed each other. This is the paradox: when you generate a new memory, all synapses are restructured, and what you just remembered is immediately lost to make room for an even newer memory,“ he explains. In other words, the same mechanism must be able to preserve acquired memory immediately or long ago while making space for new memories.

„The KIBRA protein identifies which changes are the most important. That is, as you build memories, you maintain strong synapses,“ points out the expert, referring to the memory that marks you. This operation could be likened to a traffic light: there is a series of rapid changes that occur and, as they happen, they are tagged. The brain classifies in green those memories that must be kept for their importance. In contrast, it marks in red those that are dispensable.

This tagging, however, „is not linked to what is happening, but to how the brain will work with this information later,“ clarifies the UB researcher. „In memory formation, not only does the moment we have the experience intervene, but at a cerebral level, it continues to work over time.“ At the same time, the research highlights the importance of the interaction between the proteins PKMzeta and KIBRA. „We know hundreds of proteins that are necessary for memory to exist. But these authors show for the first time that these two proteins must act together for it to form,“ adds Andero.

Understanding how our brains store and preserve memories is crucial for elucidating and treating conditions such as Alzheimer’s. Additionally, according to Andero, it can promote the development of new drugs and accumulate valuable scientific knowledge in the long term. „In the future, someone will take this idea and give it a completely unexpected twist,“ he expresses.