Brain-wide activations related to forepaw force control identified by behaving mouse fMRI

Control of upper limb force is crucial for motor skill acquisition. Rodent models have been instrumental in elucidating the behavioral and neural mechanisms underlying skilled movements. Integrating these models with advanced neuroimaging approaches, such as awake functional magnetic resonance imaging (fMRI) in behaving mice, enables whole-brain mapping of motor activity. However, experimental paradigms supporting awake fMRI during upper limb motor behavior in mice remain limited. Here, we developed an MRI-compatible head-fixation system that enables male and female mice to perform a unilateral forepaw force control task for water reward during ultra-high-field (11.1 T) fMRI. Mice successfully acquired the task, as evidenced by increased rewarded presses, convergence of force output toward the rewarded threshold, and reduced force variability. Significant activation clusters related to forepaw force were identified across multiple cortical regions, including the primary and secondary motor cortex, anterior cingulate cortex, and primary somatosensory cortex. Activation extended to subcortical structures, including the cerebellum, striatum, hypothalamus, and thalamus (ventrolateral and ventroposterior nuclei). Analysis of limb kinematics from synchronized video recordings revealed strong spatial correspondence between forepaw-related and force-dependent activation maps. Region-of-interest analyses further identified engagement of medullary structures, specifically the lateral rostral medulla and caudal medulla, in forepaw force control. Notably, the cerebellum and caudal medulla exhibited later peak responses relative to cortical regions. Together, these results establish a robust framework for awake fMRI during forelimb motor tasks and provide a comprehensive map of cortical, subcortical, and brainstem circuits underlying forelimb force control in mice. Significance Statement Control of forelimb force is fundamental to motor function, yet its underlying neural mechanisms remain unclear. We present an awake mouse fMRI approach that enables simultaneous measurement of forepaw force and whole-brain activity during a controlled motor task. This method reveals a distributed network spanning cortical, subcortical, cerebellar, and brainstem regions involved in forelimb force control. By directly linking behavior to brain-wide activation, this framework overcomes key limitations of anesthetized imaging and provides a translational bridge between animal and human studies. Importantly, this framework can serve as a bridge between animal and human studies and can be used to investigate circuit-level dysfunction in disorders such as stroke and to develop targeted strategies for motor recovery.