Models of sensorimotor transformations and vestibular reflexes.

The vestibulo-ocular and vestibulo-collic reflexes are well-studied sensorimotor systems with dynamic properties that have been successfully modeled. Recently proposed matrix and tensorial models attempt to describe the spatial organization of these reflexes in three dimensions. Here we describe experiments that test these models. We show that a matrix model of the vestibulo-ocular reflex provides a satisfactory description of its spatial properties. The vestibulo-collic reflex is more complex, but a tensorial model makes close predictions of neck muscle excitation by the vestibulo-collic reflex. In addition, our preliminary data show that the cervico-collic or neck stretch reflex produces essentially the same spatial pattern of neck muscle excitation as the vestibulo-collic reflex, a finding predicted by the tensorial model. We conclude by showing electromyographic and single neuron responses that can be modeled only by combining models of dynamics with models of spatial organization. We believe that the development of such models is the next major challenge in the application of quantitative methods to analysis of reflex behavior.