Stabilization of Working Memory Representations in the Secondary Motor Cortex with Extensive Practice

Основные понятия

Working memory representations in the secondary motor cortex (M2) stabilize with extensive practice, while representations in other brain regions remain more volatile.

Аннотация

The article investigates the mechanisms underlying the generation and evolution of working memory neuronal representations at the population level over long timescales. The researchers trained head-fixed mice to perform an olfactory delayed-association task and used optogenetic inhibition and mesoscopic calcium imaging to study the dynamics of working memory representations in different brain regions.
Key findings:

Optogenetic inhibition of secondary motor neurons during the late-delay and choice epochs strongly impaired the task performance of the mice, indicating the importance of these neurons for working memory.
Many late-delay-epoch-selective neurons emerged in the secondary motor cortex (M2) as the mice learned the task, and the working memory late-delay decoding accuracy substantially improved in M2, but not in the primary motor cortex (M1) or retrosplenial cortex (RSA), as the mice became experts.
During the early expert phase, working memory representations during the late-delay epoch drifted across days in M2, while the stimulus and choice representations stabilized.
Simultaneous volumetric calcium imaging of up to 73,307 M2 neurons, including superficial layer 5 neurons, revealed stabilization of late-delay working memory representations with continued practice.
The article suggests that delay- and choice-related activities that are essential for working memory performance drift during learning and stabilize only after several days of expert performance, particularly in the secondary motor cortex.

Статистика

Mice were trained to perform an olfactory delayed-association task with a 5 s delay.
Optogenetic inhibition of secondary motor neurons during the late-delay and choice epochs strongly impaired the task performance of the mice.
Working memory late-delay decoding accuracy substantially improved in the M2, but not in the M1 or RSA, as the mice became experts.
Simultaneous volumetric calcium imaging of up to 73,307 M2 neurons was performed.

Цитаты

"Working memory, the process through which information is transiently maintained and manipulated over a brief period, is essential for most cognitive functions1,2,3,4."
"During the early expert phase, working-memory representations during the late-delay epoch drifted across days, while the stimulus and choice representations stabilized."
"In contrast to single-plane layer 2/3 (L2/3) imaging, simultaneous volumetric calcium imaging of up to 73,307 M2 neurons, which included superficial L5 neurons, also revealed stabilization of late-delay working-memory representations with continued practice."

Ключевые выводы из

Volatile working memory representations crystallize with practice - Nature

by Arash Bellaf... в www.nature.com 05-15-2024

https://www.nature.com/articles/s41586-024-07425-w

Дополнительные вопросы

How do the dynamics of working memory representations in other brain regions, such as the prefrontal cortex, compare to the findings in the secondary motor cortex?

The dynamics of working memory representations in other brain regions, particularly the prefrontal cortex, may exhibit similarities and differences compared to the findings in the secondary motor cortex. While the study focused on the emergence and stabilization of late-delay working-memory representations in the secondary motor cortex (M2), it is known that the prefrontal cortex plays a crucial role in working memory processes. The prefrontal cortex is involved in the active maintenance and manipulation of information during working memory tasks. Studies have shown that neuronal activity in the prefrontal cortex is essential for working memory performance and that the prefrontal cortex interacts with other brain regions, including the secondary motor cortex, to support working memory functions. Therefore, while the specific dynamics of working memory representations may vary across different brain regions, there is likely coordination and interaction between these regions to facilitate working memory processes.

What are the potential implications of the stabilization of working memory representations for cognitive flexibility and adaptability?

The stabilization of working memory representations, as observed in the study, can have significant implications for cognitive flexibility and adaptability. Working memory is crucial for various cognitive functions, including decision-making, problem-solving, and learning. When working memory representations stabilize with practice and expertise, it indicates that the brain has optimized the neural circuits involved in maintaining and manipulating information over short periods. This optimization can lead to improved cognitive performance, as individuals can more efficiently process and retain information, leading to better decision-making and problem-solving abilities. Additionally, stabilized working memory representations may enhance cognitive flexibility by allowing individuals to adapt quickly to new information or changing circumstances. Overall, the stabilization of working memory representations can enhance cognitive abilities and support adaptive behavior in various contexts.

Could the insights from this study on the dynamics of working memory representations be applied to understand the neural mechanisms underlying other cognitive processes, such as decision-making or learning?

The insights gained from this study on the dynamics of working memory representations have the potential to be applied to understand the neural mechanisms underlying other cognitive processes, such as decision-making or learning. Working memory is closely linked to decision-making processes, as it involves the temporary storage and manipulation of information to guide choices and actions. By studying how working memory representations evolve and stabilize over time, researchers can gain valuable insights into how the brain processes and integrates information to make decisions. Similarly, learning involves the acquisition of new information and skills, which rely on working memory to encode and retain knowledge. Understanding how working memory representations change with practice and expertise can provide valuable information on the neural mechanisms that support learning and memory consolidation. Therefore, the findings from this study can serve as a foundation for investigating the neural basis of decision-making, learning, and other cognitive processes that rely on working memory functions.