Test-retest reliability of the vestibular sensory-evoked potential (VsEP) in C57BL/6J mice.

Abstract

The vestibular sensory-evoked potential (VsEP) is an electrical potential that provides a direct test of vestibular function in animals. VsEP recordings are carried out using subcutaneous stainless steel electrodes placed over the nuchal crest (noninverting), behind either the left or right pinna (inverting), and at the hip (ground). A noninvasive head clip is used to secure the head to a mechanical shaker for delivery of a linear vestibular stimulus measured in units of jerk (g/msec). Frequent repositioning of the noninvasive head clip and skin electrodes may be necessary during recording for particular protocols; however, the test-retest reliability of the VsEP response (latency, amplitude, and threshold) has not been determined. The purpose of this study was to determine the possible effects of frequent repositioning of the noninvasive head clip and skin electrodes on VsEP response parameters (latencies, amplitudes, and thresholds). We hypothesize that the VsEP response will remain stable and reliable with such repeated measurements in a given animal across time. Linear VsEP responses were recorded from ten C57 mice (ages: 2.45 mo ±0.20; weights: 17.94 g ±1.51). Two standard threshold protocols and four repeated VsEP measurements at +6 dB re: 1.0 g/msec were performed, with four selected time points of head clip repositioning. In addition, three novice investigators performed measurements of noninverting electrode placement and head clip positioning. VsEP response latency, amplitude, and threshold means did not significantly change with frequent repositioning of the head clip and skin electrodes; however, increased variability was observed. The findings demonstrate that repositioning does not introduce significant changes in mean parameter values of the recorded VsEP response waveform; however, mean absolute difference calculations demonstrated that frequent repositioning increased response variance. For VsEP protocols requiring frequent repositioning, standardized electrode montage, optimal placement of the noninverting electrode at the nuchal crest, and increased sample size are suggested.