A comparison of the effects of sedatives on the auditory evoked cortical response

Several sedatives were selected that were judged to be amenable for routine clinical use in electroencephalic response audiometry (ERA). These sedatives were investigated to determine which were most effective for ERA; the relationship between sleep stages and the auditory evoked cortical response (AECR), the reliability of the AECR in sleep, and whether either the early or late response was more consistent or detectable during sedation. The early response was evoked by tone pips with a 10-musec rise-decay time and an acoustic duration of 5 msec. Tone pips were presented at a rate of 8 per sec and an averaged response was based upon 1500 stimulus presentations. The late response was evoked by tone bursts centered at 1000 Hz with a 10-msec rise-decay time and an acoustic duration of 150 msec. All tone pips and tone bursts were presented at 40 dB sensation level. Eleven normal hearing adults were selected as subjects who demonstrated clear and consistent eerly and late AECR's while awake and in natural sleep. Early and late responses were analyzed to determine the percentage of detectable responses, and amplitude and latency under all sedatives and different sleep stages. The results showed that nonbarbiturates and sleep stage 2 and 3 were more effective for ERA.