Implementation and validation of a computational model of the feline forelimb

Abstract

Postural control incorporates multiple neural and mechanical systems at various levels of the motor control system, yet the question of how all these systems interact remains unanswered. This dissertation describes development of a biologically based, three-dimensional mathematical model of the forelimb of the domestic cat that integrates skeletal anatomy, muscular architecture, and neural control. Previous work has shown that muscle architecture profoundly affects its function. However, even though the forelimbs of quadrupeds contribute to posture and locomotion differently from hindlimbs, most models of quadruped motion are based upon hindlimb mechanics. The proposed work consists of three main steps: (1) architectural and anatomical characterization, which involves acquisition of muscle attachment data, measurement of whole muscle and muscle fiber properties, and estimation of limb kinematic parameters; (2) model development and implementation, wherein the data will be integrated into a mathematical model using special-purpose software; and (3) model validation, including verification of model estimates against experimentally obtained measurements of muscle moment arms, and prediction of limb kinetics, namely end-point forces arising from perturbations to the limb. It was found that the forelimb does indeed possess structure, particularly at the shoulder and antebrachium, that allows for more diverse movements. The neural wiring in these regions is more complex than in the hindlimb, and there exists substantial muscular structure in place for non-sagittal motion and object suppression and retrieval. Other results showed that the kinematics of the limb alone produce a restorative response to postural disturbance but that the magnitude is reduced, indicating that neural input acts as a modulatory influence on top of the intrinsic mechanism of limb architecture. Furthermore the model demonstrated many of the essential features found in the experiments. This study represents the implementation of the first forelimb model of the cat incorporating mechanical properties and serves as a key component of a full quadruped model to explore posture and locomotion.