A Physiologically Detailed Biomechanical Model of the Mouse Distal Forelimb for Simulation of Fine Motor Control

A comprehensive biomechanical model of the mouse's distal forelimb has been developed, capturing the intricate musculature, tendon routing, and digit-level skeletal structure that are often overlooked in previous models. This advanced representation, built from high-resolution anatomical reconstructions and computational simulations, offers a detailed depiction of the wrist and each digit, enabling the study of complex movements.

The model's capabilities are demonstrated through simulations of various tasks, with a particular focus on grasping, grasping with supination, wrist flexion, and flexion of the first digit. These simulations were designed to explore the intricate interplay between intrinsic and extrinsic muscles during grasping. To ensure the model's reliability, its performance was evaluated by comparing simulated marker trajectories with those from a torque-driven reference motion, assessing temporal shuffle control, and aligning muscle-driven simulations with experimentally recorded electromyography (EMG) activity.

The results show that the model accurately reproduces the coordinated movements of the distal forelimb. It also reveals a strong correlation between simulations driven by torque and those powered by muscle activity, confirming the model's capability to generate realistic muscle excitation patterns. These findings closely match the EMG activity observed during actual grasping movements in mice.

By establishing this model, researchers now have a robust tool for investigating fine motor control, neuromuscular coordination, and movement impairments in mice. It not only serves as a foundation for future studies on neurological disorders but also provides valuable insights into the underlying biomechanical mechanisms of these critical processes.