Gain of the vestibulo-ocular reflex in monkey at high rotational frequencies

The gain of the vestibulo-ocular reflex (VOR) was measued in alert monkeys during sinusoidal oscillations of the animals over a frequency range extending from 0.5 to 6 Hz. In confirmation of the results of previous investigators the gain of the VOR was found to be consistently below unity in the dark at rotational frequencies up to 1 Hz. When visual information was present to augment the vestibular input the gain increased to a value of 1 over this same frequency range. In contrast, as the rotational frequency increased above 1 Hz, the gain in the dark increased steadily until it exceeded unity at about 2 Hz. Peak gain (mean = 1.3) was reached in the dark at about 4 Hz and declined sharply at higher frequencies to fall below one at 6 Hz. Gain in the presence of fixed visual images remained at one over this entire range of frequencies.