Gaze stabilization by optokinetic reflex (OKR) and vestibulo-ocular reflex (VOR) during active head rotation in man

Vestibulo-ocular reflex (VOR)-optokinetic reflex (OKR) interaction was studied in normal human subjects during active sine-like head movements in the horizontal plane for a variety of vestibular-optokinetic stimulus combinations (frequency range, 0.05-1.6 Hz). At low to mid frequencies (< 0.2 Hz) the eyes tended to be stabilized on the optokinetic pattern, independently of whether the head, the pattern, or both were rotated. At higher frequencies, the OKR gain was attenuated and, in each of the differing stimulus combinations, the eyes became increasingly stabilized in space. Qualitatively similar results were obtained when, for the same visual-vestibular combinations, the head was passively rotated at 0.05 and 0.8 Hz. The data could be simulated by a model which assumes a linear interaction of vestibular and optokinetic signals. It considers the OKR with its negative feedback loop of primordial importance for image stabilization on the retina and the VOR only as a useful addition which compensates for the limited bandwidth of the OKR during high frequency/velocity head rotations in a stationary visual environment.