Activity of forelimb motor units and corticomotoneuronal cells during ramp-and-hold torque responses: comparisons with oculomotor cells

Abstract

Publisher Summary To compare the functional organization of the somatomotor and oculomotor systems, it may be helpful to begin by comparing the response properties of their motoneurons and monosynaptically connected premotor neurons under behavioral conditions, which are as comparable as possible. In the somatomotor system, the activity of single forelimb motor units and input cells from precentral motor cortex, during ramp-and-hold torque responses has been sufficiently characterized to provide some basis for comparison. Such ramp-and-hold responses, alternating between flexion and extension target zones, were chosen to reveal the neural activity related to changes in force and to maintain static force; for purposes of discussion, these ramp-and-hold wrist responses may be considered analogous to saccadic eye movements followed by fixation. This chapter discusses the response properties and organization of somatic motor units and corticomotoneuronal (CM) cells, with brief comments on some interesting analogies with comparable oculomotor neurons. More information on the correlational linkages of the observed cells with their inputs and their targets would be helpful for understanding the source and consequences of their response properties.