Frequency specificity of the auditory brain stem response

Brain stem responses were obtained from eight young adult listeners with normal hearing. These potentials were evoked using three stimuli: a click, a 500 Hz, tone pip with a 2.5 ms. rise time, and a 500 Hz. tone pip with a 5.0 ms. rise time. Each stimulus was presented in quiet and in the presence of three high pass noises and one low pass noise. No significant difference in the latency-intensity function was obtained for the click between the quiet and the low pass noise conditions. There was, however, a significant prolongation of the latency in the presence of high pass noise. The latency of the brain stem response to the 500 Hz. tone pip was essentially unaffected by the high pass noise except for the 1200 Hz. high pass noise condition. These data indicated that for the tone pips a more basal region of the basilar membrane would be involved at high intensity stimulus levels. This involvement of basal regions, however, would not extend beyond the region responsive to a 2400 Hz. stimulus. The threshold for the click was significantly elevated in the high pass noise conditions but not in the low pass noise condition. The threshold of the 500 Hz. tone pip was significantly higher than that of the click in quiet and in the presence of noise.