The nystagmic response of the pigeon to constant angular acceleration at liminal and supraliminal intensities.

Abstract

An apparatus which provides perfectly constant angular acceleration over a wide range of intensities was used to measure the sensitivity of 23 homing pigeons as indicated by head movements. The absolute threshold is an acceleration of about 0.79[degree]/sec2, at which intensity the response has an average latency of 9.9 sec. This latency decreased curvilinearly with increased intensity of stimulus until it was inappreciable at 7.52[degree]/sec2. Vision increased the threshold to 1.76[degree]/ sec3 when an artificial environment was accelerated with the bird. Vigor of response increased with intensity of stimulus. Repetition of equal accelerations produced ha-bituation. The stimulus values of equal rates of acceleration and retardation were equal regardless of direction. Contrary to tradition, the 2 horizontal canals proved equal in sensitivity to acceleration in either direction. The threshold of sensitivity to vestibular stimulation is sufficiently high to render the nystagmic head reflex "entirely worthless as a mechanism for preserving directional orientation during prolonged flight. This function, in both bird and human aviator, is specifically mediated by vision.".