GAZE STABILIZATION BY OPTOKINETIC REFLEX (OKR) AND VESTIBULOOCULAR REFLEX (VOR) DURING ACTIVE HEAD ROTATION IN MAN

Vestibule-ocular reflex (VOR)-optokinetic reflex (OKR) interaction was studied in normal human subjects during active sine-like head movemen ts in the horizontal plane for a variety of vestibular-optokinetic sti mulus combinations (frequency range, 0.05-1.6 Hz). At low to mid frequ encies (<0,2 Hz) the eyes tended to be stabilized on the optokinetic p attern, independently of whether the head, the pattern, or both were r otated, At higher frequencies, the OKR gain was attenuated and, in eac h of the differing stimulus combinations, the eyes became increasingly stabilized in space, Qualitatively similar results mere 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 whi ch assumes a linear interaction of vestibular and optokinetic signals, It considers the OKR with its negative feedback loop of primordial im portance for image stabilization on the retina and the VOR only as a u seful addition which compensates for the limited bandwidth of the OKR during high frequency/velocity head rotations in a stationary visual e nvironment. (C) 1997 Elsevier Science Ltd.