How many times have we heard people say “my hair stand on end when I remember”, or “don’t remind me, please”? The realism with which we evoke our experiences, whether good or bad, never ceases to amaze us. Until recently it was believed that a memory was the product of a simple linear sequence of actions of neurons. But studies point to a much more complex mathematical formula, a symphony of communication between nerve cells.
During decades,a challenge for neuroscientists has been to know how memories are recorded in the brain. Today, Dr. Joe Z. Tsien, director of the Center for Neurobiology Systems at Boston University, and his colleagues have discovered the basic mechanism for extracting vital information and preserving it.
? It all started with a work we did on learning and memory ,? he explains during a telephone interview from his laboratory. “In 1999 we created asuperratóngenetically enhanced who learned faster and remembered things longer. That’s when I started wondering how exactly the mnemonic process works. “
Could we visualize the activity pattern of neurons when a memory is constructed? And discern the organizing principles that allow you to extract and record the most important details of an experience? But to answer those questions, better equipment had to be designed. “Until then it was possible to record the electrical signals of hundreds of neurons in awake monkeys, but researchers working with mice had only been able to do so with 20 or 30 at a time,” writes the neurobiologist in an article published in the journalScientific American.
Before long, Tsien and his laboratory colleague, Longnian Lin, developed a recording device with which to monitor the activity of a greater number of neurons in mice moving freely. “We managed to insert a lot of tiny electrodes into the animal’s brain,” Tsien recalls. The next step wasdesign different situations to stress rodents: a miniature earthquake inside a box, a free fall from a cookie jar, and a simulated bird attack – with a sudden gust of air on its back. These negative experiences left an indelible mark on the memory. “The goal was to take advantage of what the brain seems to do best:record memories of events that can profoundly affect life“, precise Tsien.
Withholding such events requires the concerted work of an enormous number of cells. This facilitates the work when it comes to finding the neurons that are activated by the experience and collecting enough data to decipher the organizational patterns involved in the process. The experiments consisted of subjecting the mice to seven episodes of each event, separated by periods of rest. The team recorded the electrical activity of about 260 neurons in the CA1 region of the hippocampus, a key area for memory formation in animals and humans.
With the help of a powerful mathematical method, capable of projecting a large number of dimensions – in this case, 520: the activity of 260 neurons before and after an event – into a three-dimensional graphic space, the researchers discovered that there are neurons with very obvious behavior, and thatthe linear current of signals between one nerve cell and another is not enough to explain how the brain generates and stores a memory. What they observed, instead, was thatthey activated in groups, which they baptized asneural slaps? “neural gangs”?. Specifically, they followed a triangular path through the hippocampus, a pattern repeating itself from time to time, like a school of fish maneuvering in unison to flee from a predator. According to Tsien, “this proves that the information was being recorded. We imagine that successivereplaysthey correspond to the memory of the experience. “
His theory is that each of theslapsit is responsible for capturing and storing the multiple aspects associated with an event, from the most general and abstract to specific details. For example, in an earthquake there must be a group associated with the fear stimulus, a second that responds to any alteration in movement, a third that is activated by the earthquake, and a fourth that recognizes the scene of the events.
Although the idea that perception and memory are represented by neural “cliques” is not new, Tsien’s work has provided the first experimental data on how information is encoded and ordered. “The observations support the idea that hierarchical and categorical organization constitutes a universal principle within our brain”, explains the neurobiologist. In the case of memory, these properties make it possible to “generate an almost unlimited number of neuronal activation patterns, as many as the number of experiences that an organism can live”.
Tsien has begun to apply his discoveries to the design of a new generation of advanced computers and networks. In order to equate the brain with a computer, the researchers translated the activities of neural clicks into a binary code – a system of zeros and ones in which 0 symbolizes the inactive state of neurons and 1, activity. to compare the minds of several mice subjected to the same experience. Tsien went a little further and designed a system that converted the neuronal activity of rodents when they felt a tremor into a binary sequence that opened a hatch to escape.
Today’s computers fail to mimic certain human abilities, such as recognizing a classmate even after 20 years have passed and he has grown a beard. But Tsien dares to predict a future in which we will download our memories to a hard drive. And perhaps then computers, equipped with sophisticated sensors and a logical architecture similar to that of our hippocampus, will end up surpassing our cognitive prowess.
As if this were not enough, Tsien believes that “if we could simultaneously record the activity of many neurons, we could read people’s thoughts.” If there is such a sensitive technology, it could be known, for example, if an Alzheimer’s patient who can no longer speak is able to understand a conversation.
Maria iriondo
