The 3-channel Lissajous' trajectory of the auditory brain-stem response. VII. Planar segments in humans

Auditory brain-stem response (ABR) recorded from 3 orthogonally placed electrode pairs reveals a voltage-voltage-voltage plot of activity known as the 3-channel Lissajous' trajectory (3-CLT). ABR 3-CLT responses have been recorded from 9 human subjects in response to monaural, 70 dB nHL clicks. Responses were simultaneously recorded from 3 electrode channels in the vertical, horizontal and anterior-posterior plane. These 3 channels were combined to form human ABR 3-CLTs. Analysis of data included inspection of single-channel data, determination of segments along the trajectory which fall into distinct planes, and derivation of overall amplitude by time measures known as vector amplitude plots. Depending upon definition, 9 or 10 sequential, overlapping planar segments are found in the ABR 3-CLT of human subjects. Measures of planar apex latency and duration of planar segments were found to be reasonably consistent between subjects as were the orientations of planar segments. Vector amplitude plots (absolute amplitude of 3-channel recordings over time) derived from the human 3-CLT demonstrate 8 fast peaks which appear to be superimposed upon slow wave activity. These plots are shown to be potentially useful in determining optimal electrode orientations for single-channel recording of various ABR peaks. It was concluded that planar-segment formation in the ABR 3-CLT is a consistent finding in human subjects and that this technique is a promising clinical and research tool.