Effects of amplifier type (single-ended vs. differential) and electrode placement on early auditory evoked potentials

The effects of amplifier type (single-ended versus differential) and electrode location on early auditory evoked potentials were investigated in normally hearing subjects. Each subject was tested with six electrode combinations using 70 dB nHL clicks. One differential recording was made for each subject by placing the non-inverting (A+), inverting (A-), and common (C) electrodes on the vertex, ipsilateral neck, and contralateral neck, respectively. Five single-ended recordings were obtained from each subject. One electrode (positive) was situated on the vertex, whereas the second electrode (negative) was variously placed on (1) ipsilateral mastoid, (2) ipsilateral neck, (3) seventh cervical vertebra, (4) ipsilateral wrist, and (5) lower forehead. Because the vertex-lower forehead montage yielded identifiable responses in only one of 13 subjects, this condition was omitted from data analyses. No statistically significant latency or amplitude differences were observed among the remaining five electrode combinations for Waves I, III, or V. These data suggest that any of the five electrode combinations may be used for recording early auditory evoked potentials. Moreover, it is important to note that the single-ended recordings can yield auditory evoked potentials comparable to conventional differential recordings.