Vestibular memory-contingent saccades involve somatosensory input from the body support

Humans use vestibular head-in-space information when redirecting gaze towards remembered target location in space. This study shows that neck input is also involved. Normal subjects performed saccades towards remembered locations in space of a previously seen target following passive horizontal rotations of the head or trunk. Saccades based on vestibular input alone fell short at low stimulus frequencies. Addition of neck input modified the responses, making them more accurate when the head was rotated on the stationary trunk. The results support a concept according to which vestibular input is channeled via proprioceptive coordinate transformations through the haptically perceived body support before yielding a sense of head motion in space. The loop is also involved in the saccadic gaze mechanism.