Comparative anatomy of the motor system: differences in the organization of corticospinal control in different species

Abstract

Publisher Summary This chapter highlights some of the important differences between the organization and function of the motor system in the various animal models that are available to the clinical scientist. It also discusses some crucial differences between these models and the human motor system, the role of descending projections to dorsal horn activity in the control of sensory afferent input, and the capacity of direct cortico-motoneuronal projections to the motor nuclei to support voluntary execution of skilled hand and finger movements. There are some important differences in corticospinal projections from different cortical regions within a particular species and these projections support different functions. Therefore any differences in the organization of corticospinal projections across species reflect differences in their functional role. Primate models represent the best available models that help in understanding the vulnerability of the fast corticomotoneuronal (CM) system to motor neuron disease (MND) and the consequences of this for voluntary control of the hand. However, the fundamental work on a disease such as MND cannot and should not be carried out in primates: these valuable and special animals should only be used in those aspects of research that are not tractable in other models, especially in rodents. Primate studies continue to be critical for the understanding of how the motor network operates and how the impact of pathophysiology on it can be predicted in a way that reveals the mechanisms that underlie the disease and its symptoms.