Visual influence on postural control in the cat.

The influence of horizontal optokinetic stimulation on posture and postural readjustments, induced by horizontal rotation of a turntable, were studied in the cat. Optokinetic stimulations at constant velocities lead to modifications of posture depending on the velocity of the stimulus. However, habituation as well as interindividual variability of these postural responses make difficult a systematic and quantitative approach to the phenomenon. Optokinetic stimulations at sinusoidal velocities induced reproductible postural responses, whose phase and gain were studied at different velocities and frequencies of stimulation. At low frequencies (from 0.05 Hz to 0.2 Hz) the postural responses tend to lead the position of the optokinetic stimulus while a lag appears at higher frequencies (up to 1 Hz). In these conditions the gain increases and seems to depend on the performances of the simultaneously elicited oculomotor response. Induced postural readjustments are also modulated by the relative velocity of the visual stimulation with respect to the cat. A given visual input is more effective on an induced postural readjustment than on the posture of a static animal, especially at low frequencies (from 0.05 Hz to 0.3 Hz). These data extend to the cat the strong visual component of the postural control system previously described in other species.