Three-channel Lissajous' trajectory of human auditory brain-stem evoked potentials. III. Effects of click rate

Three-channel Lissajous' trajectories (3-CLT) of the human auditory brain-stem evoked potentials (ABEPs) were recorded from 14 adult subjects using click rates of 10, 55 and 80/sec. The 3-CLTs were analysed and described in terms of their constituent planar segments and their trajectory amplitudes at each stimulus rate. Increasing stimulus rate resulted in an increase of planar segment duration which was more pronounced for segments 'a' and 'e', an increase in apex latency which was more pronounced the later the component and a decrease in planar segment size and peak trajectory amplitude which was more pronounced the earlier the component. These findings support the involvement of synaptic efficacy changes in the effects of stimulus rate on ABEP. The results are explained by overlapping convergence and divergence in the ascending auditory pathway. These results support the notion that the principal generator of each component is activated by the principal generator of the previous component, with some temporal overlap of their activities. Such temporal overlap may be minimized by using low intensity high rate stimuli.