Scientists have discovered ‘uncertain regions’ that allow the brain to rapidly form new memories

The neocortex is the largest and most complex part of the brain and has long been recognized as the ultimate repository of memory. But how are the imprints of past events and experiences put there? have unconventional ways of communicating with the neocortex to rapidly control memory formation.

Memory is one of the brain’s most fundamental and fascinating functions, allowing us to learn from our experiences and recall our past. As such, it is a central component of our personal and collective human identities.Furthermore, the mechanistic understanding of memory has implications from the treatment of memory disorders and anxiety disorders, to artificial intelligence, efficient hardware and It has implications that extend into software design, so it’s not only very interesting, but also very important.

To form memories, the brain interpolates between sensory signals that come “bottom-up” (or outside-in) from the environment and internally-generated “top-down” signals that convey information about past experiences and the present. You have to build an association. Purpose. These top-down (or inside-out) signals are still shrouded in mystery and are therefore a major focus of current research.

Work over the past few years has begun to identify several such top-down projection systems, all of which showed some commonalities. They signaled by excitation, the standard way of transmitting information between cortical regions, and also demonstrated a common mechanism for encoding memory. Stimuli with learned relevance evoke stronger responses in these systems, suggesting that this positive enhancement is one piece of the puzzle: memory tracing.

“In contrast to these systems, long-range inhibitory pathways are much more sparse and few in number, but there is growing evidence that they can have surprisingly powerful effects on network function and behavior.” said Johannes Letzkus, professor at the university.Former research group at the Max Planck Institute for Brain Research, whose leader is the University of Freiburg, led a new study published in neuron“We set out to determine whether such inputs could exist in the neocortex and, if so, how they uniquely contribute to memory.”

Dr. Anna Schroeder, lead author of the study and a postdoctoral fellow in the Letzkus lab, chose to address this issue by focusing primarily on the inhibitory subthalamic nucleus, the zone of uncertainty. . Although the function of this brain region, as its name suggests, remains a mystery, her preliminary findings suggest that inhibitory neurons selectively innervate regions of the neocortex known to be important for learning. Her preliminary findings showed that sending projections. To study the plasticity of this system at all stages of learning, she implemented an innovative approach that allows tracking the responses of individual zone-of-uncertainty synapses in the neocortex before, during, and after the learning paradigm. I made it

“The results were amazing,” recalls Schroeder. “About half of the synapses showed stronger positive responses during learning, while the other half did the exact opposite. In fact, what we observed was a complete redistribution of inhibition within the system due to learning.” bottom.”

This suggests that synapses in the uncertainty zone encode previous experiences in a unique, bidirectional manner. This was especially clear when scientists compared the magnitude of plasticity with the strength of acquired memory. They found a positive correlation. This indicates that uncertainty zone projections encode learned relevance of sensory stimuli.

In another experiment, Schroeder found that silencing these projections during the learning phase impairs memory traces later. This indicates that the bidirectional plasticity that occurs in these projections is necessary for learning. She also found that these inhibitory projections preferentially form functional connections with other inhibitory neurons in the neocortex, indeed forming long-range disinhibition circuits.

“This connectivity means that activation of the zone of uncertainty results in a net excitation of neocortical circuits,” says Schroeder. “However, combining this with the redistribution of inhibition seen in learning indicates that this pathway likely yields richer computational outcomes for neocortical processing.”

Scientists were particularly intrigued by populations of zona synapses exhibiting negative potentiation. I felt that I might offer it.

Further analysis, conducted in collaboration with Professor Henning Sprekeler and his team’s laboratory at the Technical University of Berlin, surprisingly shows that these negative responses are the main drivers of changes in stimulus representation that occur during learning itself. turned out to be a factor.

This work provides the first functional analysis of how long-range inhibition shapes neocortical computation. The signals identified in this study may be important not only for memory, but for many additional brain functions such as attention. It is one of the few areas of canonical coverage and opens up interesting possibilities for future translational research.

Ultimately, we hope that this work will inspire other researchers to continue to explore the role of long-range inhibition in regulating neocortical function, both from unidentified zones and from other as yet unidentified sources. I’m here.