VESTIBULAR AND OPTOKINETIC FUNCTION IN THE NORMAL GUINEA-PIG

Vestibular and optokinetic function was quantitatively studied in the normal guinea pig through investigation of the vestibule-ocular reflex (VOR), optokinetic nystagmus (OKN), and the visual vestibule-ocular r eflex (VVOR) by means of sinusoidal stimulation with a computer-contro lled rate table (VOR and VVOR) or an optokinetic drum. The VOR exhibit ed high-pass filter characteristics with steady state gain achieved at 0.125 Hz. The maximum gain was 0.55 at a velocity of 60 degrees/s. Th e VOR was modeled by a transfer function with best fits obtained with an adaptation time constant of 12.5 seconds. The OKN showed low-pass f ilter characteristics with a decrease in gain for increase in stimulus amplitude. The maximum gain measured was 0.64. A fractional pole mode l provided a fit of these data. The VVOR exhibited a mean gain of betw een 0.6 and 0.7 across the stimulus bandwidth and peak velocities. A m odel based on a linear combination of the actual OKN and VOR gains pro vided an estimate of the VVOR gain.