Separating Cognitive and Motor Processes: A Breakthrough in Mouse Behavioral Research

Academic Background

In the study of animal behavior, cognitive processes and motor processes are often closely intertwined. For example, when a mouse explores its environment, its facial expressions or active sampling behaviors not only reflect movement but are also closely related to neural activity across much of the brain. However, researchers have long faced a fundamental question: whether cognitive processes and motor processes can be separated, or if they are driven by common neural mechanisms. If these two cannot be distinguished, researchers may mistakenly interpret movement-related neural activity as indicative of cognitive processes, thereby affecting the correct understanding of neural circuit functions.

To address this issue, a research team from Boston University designed a behavioral task to explore the separability of cognitive and motor processes through experiments on mice. Their study not only demonstrated how to assess this separability but also developed a novel method to isolate neural dynamics associated with cognition and movement. The findings provide new insights into how the brain supports complex behaviors and lay the groundwork for developing conceptual and computational models of neural circuit function in the future.

Paper Source

This paper, titled “Separating cognitive and motor processes in the behaving mouse,” was co-authored by Munib A. Hasnain, Jaclyn E. Birnbaum, Juan Luis Ugarte Nunez, Emma K. Hartman, Chandramouli Chandrasekaran, and Michael N. Economo. The research team comes from multiple departments at Boston University, including the Department of Biomedical Engineering, the Center for Neurophotonics, and the Center for Systems Neuroscience. The paper was published in Nature Neuroscience in 2024.

Research Process and Results

1. Behavioral Task Design

The research team designed a two-context task that required mice to perform directional licking behaviors in two different cognitive environments. The task included a delayed-response task (DR task) and a water-cued task (WC task). In the DR task, mice needed to delay their response for a period after hearing an auditory cue before acting; in the WC task, mice received water rewards at random times and locations. This design allowed the mice to switch behaviors in different contexts, involving multiple cognitive processes such as perceptual decision-making, motor planning, and contextual encoding.

2. Recording of Movement and Neural Activity

To capture the movements of mice while performing tasks, the research team used high-speed cameras to record the movements of the tongue, jaw, nose, and paws of the mice and calculated motion energy to quantify these movements. Simultaneously, they recorded neural activity in the anterior lateral motor cortex (ALM) of the mice using high-density silicon probes to study neural dynamics related to cognition and movement.

3. Optogenetic Intervention

To further investigate the role of the motor cortex in the task, the research team used optogenetics to inhibit the ALM or tongue-jaw motor cortex (TJM1) of the mice at specific time points. The results showed that inhibiting these areas significantly affected the execution and planning of movements in mice, indicating their critical roles in the task.

4. Subspace Decomposition of Neural Dynamics

The research team developed a novel subspace decomposition method to separate neural activity into a “movement-potent subspace” related to movement and a “movement-null subspace” related to cognition. Using this method, they found that neural dynamics associated with cognition and movement are separable in the brain and encoded by distinct populations of neurons.

5. Relationship Between Cognition and Movement

The results indicate that although cognitive processes and motor processes are highly correlated in time, their neural dynamics in the brain are separable. For instance, choice-related neural signals exhibited stable internal representations in the “movement-null subspace,” while movement-related signals primarily appeared in the “movement-potent subspace.” This separability provides new perspectives on how the brain handles complex behaviors.

Conclusions and Implications

The main conclusion of this study is that neural dynamics associated with cognitive processes and motor processes are separable in the brain and encoded by different populations of neurons. This finding not only resolves the long-standing debate over whether cognitive and motor processes are driven by common neural mechanisms but also provides a new methodological approach for future neuroscience research. Through subspace decomposition, researchers can more accurately isolate neural signals related to specific cognitive and motor processes, thereby better understanding the function of neural circuits.

Research Highlights

1. Innovative Subspace Decomposition Method: The research team developed a new subspace decomposition method capable of effectively separating neural dynamics related to cognition and movement.
2. Two-Context Task Design: By designing a complex two-context task, the research team successfully simulated multiple cognitive processes in mice, providing an ideal experimental platform for studying the relationship between cognition and movement.
3. Combination of Optogenetics and Neural Recording: By combining optogenetics with neural recording techniques, the research team revealed the critical roles of the motor cortex in cognitive and motor processes.
4. Separability of Neural Dynamics: The study first demonstrated that neural dynamics related to cognition and movement are separable in the brain, providing an important theoretical foundation for future neuroscience research.

Other Valuable Information

The research team also discovered that certain cognitive processes (e.g., choice) exhibit stable and persistent representations in the brain, while others (e.g., urgency) are closely related to movement. This finding further reveals how the brain processes different types of cognitive tasks and offers new directions for future research. Additionally, the methods developed by the research team can be widely applied to other behavioral tasks and species, providing new tools for broad research in the field of neuroscience.

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This paper not only provides new perspectives on understanding how the brain processes cognitive and motor processes but also offers significant methodological contributions to future neuroscience research. Through innovative experimental design and data analysis methods, the research team successfully resolved a long-standing controversy in the field and paved the way for future studies.