The influence of click phase and rate upon latencies and latency distributions of the normal brain-stem auditory evoked potentials.

The effect of the phase of the click stimulus and its relation to the stimulus repetition rate on the brain-stem auditory evoked potentials (BAEPs) was investigated in 43 normal subjects, with condensation (C) and rarefaction (R) clicks of 10 and 50 Hz rate, using a piezoelectric headphone . The distribution of C and R latencies for component I seemed to be bimodal, probably reflecting (at least) two subcomponents in I separated by about 0.20 msec. C clicks tended to evoke the first and R clicks the second subcomponent. Condensation clicks gave significantly shorter absolute mean latencies for components I, IN, II, III, IIIN , IV and VI (10 Hz) and components IN, II, III, IIIN and IV (50 Hz). The V/I relative amplitude means were not influenced by phase, but increased with rate. Standard deviations were greatest for component IV latencies and increased only insignificantly with the higher repetition rate. A significantly smaller number of IV components was identified with R as compared to C clicks. Increasing the stimulus rate to 50 Hz detected wave IV in 12 of the 18 records where R clicks failed to identify IV with 10 Hz stimulation. The importance of the stimulus characteristics is discussed and some suggestions for clinical use of BAEP are made.