Perceptual encoding in auditory brainstem responses: Effects of stimulus frequency

Purpose: A central question about auditory perception concerns how acoustic information is represented at different stages of processing. The auditory brainstem response (ABR) provides a potentially useful index of the earliest stages of this process. However, it is unclear how basic acoustic characteristics (e.g., differences in tones spanning a wide range of frequencies) are indexed by ABR components. This study addresses this by investigating how ABR amplitude and latency track stimulus frequency for tones ranging from 250 to 8000 Hz. Method: In a repeated-measures experimental design, listeners were presented with brief tones (250, 500, 1000, 2000, 4000, and 8000 Hz) in random order while electroencephalography was recorded. ABR latencies and amplitudes for Wave V (6–9 ms) and in the time window following the Wave V peak (labeled as Wave VI; 9–12 ms) were measured. Results: Wave V latency decreased with increasing frequency, replicating previous work. In addition, Waves V and VI amplitudes tracked differences in tone frequency, with a nonlinear response from 250 to 8000 Hz and a clear log-linear response to tones from 500 to 8000 Hz. Conclusions: Results demonstrate that the ABR provides a useful measure of early perceptual encoding for stimuli varying in frequency and that the tonotopic organization of the auditory system is preserved at this stage of processing for stimuli from 500 to 8000 Hz. Such a measure may serve as a useful clinical tool for evaluating a listener’s ability to encode specific frequencies in sounds.