Perception of neck rotation assessed by 'remembered saccades'

A new technique for the assessment of cervical afferent function is described. It is based on the perception of trunk rotation around the earth-fixed head and assessed by the accuracy of eye saccades in the direction of trunk displacement. It was found that normal subjects were able to locate trunk position accurately (mean error 15%), independently of trunk displacement amplitude (10-40 degrees) or velocity (5-40 degrees s-1). It is concluded that normal man has accurate perception of trunk rotation and that neck-spinal afferents carry a tonic signal with efficient access to the ocular motor system. A patient with absent vestibular function showed identical results to those of normal subjects; this suggests that the enhancement of the cervico-ocular reflex observed in such patients is not mediated by an increase in neck-spinal afferent sensitivity.