Properties of the Brain-stem Response Slow-Wave Component: I. Latency, Amplitude, and Threshold Sensitivity

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Abstract
• A slow-wave component of the brainstem response recordable to signals at low sensation levels shows some promise for estimating hearing thresholds at low frequencies. This study describes several properties of this slow-wave response (SWR) in 30 normal hearing subjects and examines correlations with psychophysical thresholds. Acoustic signals were tone pips at 0.25, 0.5, 1, 2, and 4 kHz with 3-ms rise-fall times and no plateau. Repetition rate was 40/s. The EEG was filtered at 20 to 1,500 Hz before averaging. Results showed SWR thresholds were on the average about 15 dB higher than behavioral thresholds; however, the range was 0- to 35-dB sensation level. A large decrease in SWR amplitude and a 20-dB increase in threshold could occur in states of deep sleep. The SWR appears to be useful for estimating low-frequency thresholds, but the 35-dB threshold range in normal hearing subjects should be considered when interpreting some SWR results. (Arch Otolaryngol 1983;109:6-12)