Abstract
The properties of an auditory evoked response with peak latency of 5 to 8 msec was studiedin order to examine its clinical usefulness. The response is thought to represent neural activity of the brain stem auditory nuclei and has been called "brain stem response" in recent literatures.
The subjects used in this study were 17 adults, 4 young children aged 2 to 5 years and 8 infants aged 7 to 17 months. All of them were proved to have normal hearing. Active electrode was attached to the vertex while reference and ground electrodes were placed on one of the ear lobes and root of the nose respectively. The responses were led to a medical computer through an amplifier and a filter. As a rule, 2000 signals were averaged in a test run and were recorded with a X-Y recorder. Clicks and short tone bursts were used for auditory stimulation.
The response consisted several positive deflections at the scalp electrode, of which the 5th was the largest in the majority of cases. The mean peak latency and the amplitude of the largest component of the response was 5.69 msec and 0.91ttV in adults with the stimulus intensity of 80dB HL. The latency was longer and the amplitude was smaller in infants than those in adults. However, the latency and the amplitude reached adult values in the young children aged above 2 years. The responses were traciable down to the intensity levels of 5 to 10 dB above subjective thresholds in the adult group. The minimal number of times of averaging required for detecting the response in normal adults ranged 35, 50 and 130 at 80, 60 and 20 dB HL respectively.
The results obtained in this study strongly suggest that the brain stem response will be an useful index for assessing hearing thresholds and detecting brain stem lesions.
