by Ingrid Fadelli, Medical Xpress

Schematic of potential relationships between internal and movementrelated dynamics. a, Internal and movement-related dynamics that are independent and separable. Left: schematic depicting an internal process (I) and a motor process (M) that are each governed by separate latent dynamics, L1 and L2, respectively. L1 and L2 evolve within the movement-null (green) and movementpotent (pink) subspaces, respectively. Right: cartoon time series of separable, independent latent dynamics (L1 and L2) and related processes (I and M). b, Same as a in the case of latent dynamics that are separable but dependent. I and M may be loosely correlated in time. c, Same as a and b in the case of inseparable processes governed by a single set of latent dynamics (L1). Credit: Hasnain et al.

When animals and humans explore their surrounding environment or complete specific tasks, their brains simultaneously support both their mental (i.e., cognitive) processes and physical movements. For instance, some brain processes could contribute to memory encoding and decision-making, while others plan and execute their body movements or facial expressions.

As they typically occur simultaneously, these cognitive and motor neural processes are often intertwined. Therefore, determining which signals are linked to mental processes and which can be attributed to motor functions has so far proved fairly challenging.

Researchers at Boston University recently devised a new experimental approach to study cognitive and motor processes in the mouse brain, distinguishing and isolating the two. This approach, outlined in a paper published in Nature Neuroscience, could open new possibilities for neuroscience research, potentially improving the present understanding of neural circuits and their functions.

"The cognitive processes supporting complex animal behavior are closely associated with movements responsible for critical processes, such as facial expressions or the active sampling of our environments, " Munib A. Hasnain, Jaclyn E. Birnbaum and their colleagues wrote in their paper.

"These movements are strongly related to neural activity across much of the brain and are often highly correlated with ongoing cognitive processes. A fundamental issue for understanding the neural signatures of cognition and movements is whether cognitive processes are separable from related movements or if they are driven by common neural mechanisms."

To overcome the limitations of previous approaches used to study cognitive and motor processes, the researchers created a new task specifically applicable to mice. As part of this task, mice make movements based on the sensory information they are exposed to while also performing natural and spontaneous movements unrelated to the task.

"We demonstrate how the separability of cognitive and motor processes can be assessed and, when separable, how the neural dynamics associated with each component can be isolated, " wrote Hasnain, Birnbaum and their colleagues. "We designed a behavioral task in mice that involves multiple cognitive processes, and we show that dynamics commonly taken to support cognitive processes are strongly contaminated by movements."

Using a new method they developed, Hasnain, Birnbaum and their colleagues were able to separate the brain signals associated with internal thought processes that the mice engaged in while completing a task from signals associated with spontaneous movements. Notably, the approach is easy to implement in experimental settings and does not require tracking the mice's body movements using additional equipment.

Cortical dependence and uninstructed movements during a two-context task. Credit: Nature Neuroscience (2025). DOI: 10.1038/s41593-024-01859-1

"When cognitive and motor components are isolated using a novel approach for subspace decomposition, we find that they exhibit distinct dynamical trajectories and are encoded by largely separate populations of cells, " wrote the researchers.

"Accurately isolating dynamics associated with particular cognitive and motor processes will be essential for developing conceptual and computational models of neural circuit function."

This initial study carried out by Hasnain, Birnbaum and their colleagues demonstrates the promise of their approach for breaking down brain activity associated with cognition and movement as mice engage in a simple behavioral task. The new methods they introduced could soon be employed by other neuroscientists to further improve the present understanding of neural circuits, which could also inform the development of more advanced brain-inspired computational models.

More information: Hasnain et al, Separating cognitive and motor processes in the behaving mouse, Nature Neuroscience (2025). DOI: 10.1038/s41593-024-01859-1. Journal information: Nature Neuroscience

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