Low-frequency tuning in the human vestibular–ocular projection is determined by both peripheral and central mechanisms

We recently reported that a major contribution to the low-frequency tuning and sensitivity of the human vestibular system is the biomechanical properties of the vestibular end-organs. In the current paper, we investigate the contribution of additional mechanisms to low-frequency tuning. We compared the response properties of the vestibular system in 6 human volunteers to trains of 2 ms pulses of sound and transmastoid vibration using pulse repetition frequencies of 12.5, 25, 50, 100, 200 and 400 Hz. Measurements were made using two separate pathways arising from the vestibular apparatus: to the neck using vestibular evoked myogenic potentials (VEMPs), and to the eyes using ocular vestibular evoked myogenic potentials (OVEMPs). For both sound and vibration the two response pathways produced different tuning to pulse trains. The vestibulo-ocular pathway was characterised by a band-pass tuning with best frequency of 100 Hz whereas the vestibulo-collic pathway showed a peak at 400 Hz with sound only. These results suggest that properties of the vestibulo-ocular pathway also contribute to the low-frequency tuning that occurs for the OVEMP, in addition to previously reported end-organ effects.