Brainstem neurons are peculiar for oculomotor organization

Abstract

Publisher Summary This chapter describes the structural and functional aspects of neurons and neural circuits in the oculomotor system, including some comparisons to the skeletal motor system. Size is significant for neural to neural translation. The size principle is shown not to be a rigid absolute criterion because the values of velocity sensitivity varied significantly for individual neurons depending on whether they were computed during fast (including saccades) or slow phases of vestibular nystagmus. This was expected because separate sources of presynaptic afferents are known to be involved, and therefore, the differences reflect unique arborization patterns onto target motoneurons. Nonetheless, these velocity values were correlated, but less well, with conduction velocity and position sensitivity. This led to the conclusion that both motoneurons and internuclear neuron properties during recruitment and frequency potentiation are dependent upon the distribution of neuronal properties throughout the pool, as well as the pattern of synaptic effects from separate afferent systems. In addition, the interdigitated population of motoneurons and internuclear neurons in the abducens nucleus co-varied in other ways, such as their extent of static hysteresis, the influence of alertness, and position-dependent non-linearities.