The Sinusoidal Galvanic Body-Sway Response

Abstract

Galvanic body-sway responses to sinusoidal stimulus currents were obtained from eight neurootologicálly normal young adult male subjects. In all subjects, the body swayed sinusoidally in response to the sinusoidal stimulus. The most effective stimulus frequency differed in different subjects and ranged from 0.025 Hz to 0.200 Hz. The responses of all subjects declined abruptly as frequency was increased above 0.200 Hz and were barely recognizable at 0.800 Hz. Trapezoidal galvanic-response wave form and sinusoidal frequency response appeared to be related. Subjects with “a.c.” trapezoidal responses had negative sinusoidal stimulus-response phase angles at low frequencies and a low-frequency “cutoff.” Subjects with “d.c.” trapezoidal responses had positive phase angles at low frequencies and relatively flat frequency-response curves across the low-frequency range. Clinical cases demonstrating depression of the sinusoidal galvanic body-sway response coincident with depression of the trapezoidal response are presented. However, test-retest variability of the sinusoidal response is much greater than that of the trapezoidal response. Therefore, clinically, the sinusoidal response should be regarded as providing only a qualitative supplement to the quantitative results provided by the trapezoidal response.