Vector analysis of auditory brain stem responses (BSR) in human beings.

The purpose of the present study is to clarify the origins of BSRs. We recorded BSR by three ortho-diagonal leads (X-axis: right ear canal to left ear canal, Y-axis: vertex to submental position, Z-axis; forehead to inion). We studied the waveforms on each of the three planes: frontal, sagittal, and horizontal and analysed their vectors on the basis of Lissajous'figures. Lissajous'figures revealed the following: (1) The vector of wave I is almost horizontal and is directed towards the non-stimulated side. (2) Wave II seems to be derived from the cochlear nuclei and double firings of the auditory nerves. (3) Wave III represents the activities of the circuits of the auditory pathways in the brain stem. (4) The vector of Wave V is the largest of the five responses, and is directed towards the fronto-parietal region, tilting slightly to the non-stimulated side.