Summary: A recent discovery has identified a specific type of neuronal connection in the prefrontal cortex that is responsible for updating our understanding of the world and its rules.
The connection, formed by inhibitory neurons, communicates with neurons located far away in the opposite hemisphere of the prefrontal cortex. The role of this connection was explored using an imaginative test in mice, where mice lacking the ability to adapt to change were found to deactivate long-distance inhibitory neuronal connections.
The finding contributes to our understanding of brain function and may help study conditions such as schizophrenia, bipolar disorder, or autism spectrum disorder, where patients have difficulty adapting to change.
- The study discovered a specific type of neuronal connection in the prefrontal cortex, formed by inhibitory neurons, that updates our understanding of the world and its rules.
- These inhibitory neurons were found to communicate with neurons far away from them, in the opposite hemisphere of the prefrontal cortex.
- When these long-distance inhibitory neuronal connections were deactivated in mice, the mice were unable to adapt to the changes, indicating potential implications for psychiatric conditions such as schizophrenia, bipolar disorder, and the autism spectrum. disorders.
Source: Paris Brain Institute
To adapt to perceived changes in our environment, the brain constantly updates the activity of neural circuits in the prefrontal cortex, a region involved in attention, anticipation, and decision-making.
But until now, researchers didn’t know what mechanisms were responsible for these changes — which are essential to mice, primates, and humans if they want to survive.
“By studying this amazing ability, we found a specific type of neuronal connection in the prefrontal cortex, which helps to update our representation of the world – and more importantly, the rules this, explains Kathleen Cho, a researcher in the ‘Cellular physiology of cortical microcircuits’ team at the Paris Brain Institute.
“Thanks to this, we don’t continue to use an inappropriate approach to achieve a goal. Such as typing an outdated code, over and over again, to unlock the door.”
This newly discovered connection is formed by inhibitory neurons, a class of nerve cells that have the ability to read the activity of other neurons. The researchers hypothesized that these inhibitory neurons transmit electrical and chemical information to areas located in their immediate vicinity. But while exploring how they work in mice, Kathleen Cho and her colleagues at the University of California made an important discovery.
“We noticed that a subclass of inhibitory neurons, parvalbumin-expressing interneurons, can communicate with neurons very far away from them, in the opposite hemisphere of the prefrontal cortex,” said the researcher.
The secrets of a long-distance relationship
To better understand the exact function of these interneurons, the team observed their activity in mice during an imaginative test. The researchers presented the animals with bowls in which food was hidden.
Initially, the presence of garlic or sand in the container indicated the exact location of the reward. Then, this clue is replaced by another, forcing the mice to recognize and exploit the new rule to dig for food.
However, when the famous long-distance inhibitory neuronal connections were deactivated in a group of rodents through an optogenetic technique, they proved unable to adapt to the change.
They continued to look for food wherever they found sand or the smell of garlic. In a way, the mice are stuck in their old habits…
The researchers also showed that long-distance inhibitory connections synchronize variations in high-frequency neuronal electrical activity – gamma oscillations – between the two hemispheres of the prefrontal cortex.
“This synchronization is associated with a specific event: the moment when the mice realize that the rule is no longer valid,” Cho said.
These synchronization effects, surprisingly, persist over time. Mice in which parvalbumin-expressing interneurons were deactivated remained unable to integrate new rules for several days.
Subsequently, the artificial stimulation of gamma synchronization compensated for this deficiency and completely restored their flexibility.
A slight lack of flexibility
Previous research has shown poor synchronization of gamma waves in the prefrontal cortex, and abnormalities in inhibitory neurons exist in many schizophrenic patients. This mental illness results in great difficulty adapting to change – a symptom also observed in bipolar disorder or autism spectrum disorder.
Further studies will be needed to determine what role dysfunctional inhibitory neuronal connections play in these diseases.
“We do not know which cells in the prefrontal cortex receive information through these distant connections, the researcher added. We also do not know what molecular mechanisms are involved in long-term changes in neuronal activity”.
Answering these questions can help us understand under what conditions the brain is committed to retaining certain information… and opening up to new ones.
About this neuroscience research news
Author: Mary Simon
Source: Paris Brain Institute
Please contact: Marie Simon – Paris Brain Institute
Image: Image credited to Neuroscience News
Original Research: Open access.
“Long-range inhibition synchronizes and updates prefrontal task activity” by Kathleen Cho et al. Nature
Long-range inhibition synchronizes and updates prefrontal task activity
Changes in activity patterns within the medial prefrontal cortex allow rodents, non-human primates and humans to update their behavior to adapt to environmental changes—for example, during of cognitive tasks.
Parvalbumin-expressing inhibitory neurons in the medial prefrontal cortex are important for learning new strategies during a rule-shift task, but circuit interactions that switch prefrontal network dynamics from maintenance to update of task-related activity patterns remains unknown. We describe here a mechanism linking parvalbumin-expressing neurons, a new callosal inhibitory connection, and changes in task representations.
Whereas nonspecific ablation of all callosal projections did not prevent rats from learning rule transfers or disrupt the evolution of activity patterns, selective ablation of only callosal projections of parvalbumin-expressing neurons impairs rule-shift learning, desynchronizes the gamma-frequency activity required for learning and prevents the reorganization of prefrontal activity patterns that normally accompany learning. – rule change study.
This dissociation shows how callosal parvalbumin-expressing projections shift the operating mode of prefrontal circuits from maintenance to update by transmitting gamma synchrony and gating the ability of other callosal inputs to maintain previously established neural representations.
Thus, callosal projections arising from parvalbumin-expressing neurons represent a key circuit locus for understanding and correcting deficits in behavioral flexibility and gamma synchrony implicated in schizophrenia and related disorders. condition.
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