Short latency vestibular responses to pulsed linear acceleration.

Far-field vestibular responses to pulsed linear cranial acceleration have not been reported in detail for any species. In this study, precisely defined pulsed linear accelerations were used to elicit vestibular neural responses recorded from the surfaces of the skulls of 23 White Leghorn chicks. Traditional signal averaging techniques were used to resolve responses. At moderate intensities, responses consisted of a series of four to seven dominant peaks occurring within a period of 8 ms, having amplitudes between 0.3 and 20 microV peak-to-peak. The mean response threshold was 0.120 +/- 0.045 g. Latencies and amplitudes varied systematically as a function of stimulus intensity. Hypothermia prolonged response latencies. Response peaks did not invert on stimulus inversion, were present in response to cranial but not trunk acceleration, were not attenuated by broad-band auditory masking or by ambient light conditions, and disappeared with complete bilateral destruction of the labyrinth. The results rule out major contributions from auditory, somatosensory, and visual modalities and support the hypothesis that the responses reflect bilateral neural activity in the vestibular system. The findings suggest that direct noninvasive assessment of peripheral vestibular function can be achieved using pulsed linear acceleration stimuli.