MONAURAL AND BINAURAL GALVANIC VESTIBULAR STIMULATION IN HUMAN DYNAMIC BALANCE FUNCTION

Spontaneous dynamic balance reactions to galvanic binaural and monaura l stimulation were investigated in lateral sway. Low-intensity current s were used to stimulate the vestibular apparatus of subjects, who wer e standing with their eyes closed on a rocking platform. Head and body base movements were measured in the lateral plane, simultaneously. In monaural as well as in binaural stimulation mode. the onset of the cu rrent induced a lateral biphasic stereotyped postural responses: first ly the pressure centre moved towards the cathode side then the whole b ody swayed towards the anode side. The cut-off of the current resulted in a similar pattern of movement but in the opposite direction. Two m ain features characterised the response obtained in monaural mode. Fir st, the amplitude of the dynamic balance response was half the size of that recorded in binaural stimulation mode. Second, cathodal monaural stimulation on one side or anodal monaural stimulation on the opposit e side elicited superimposable responses. The results demonstrate that in healthy subjects, postural response to binaural galvanic vestibula r stimulation results from the linear sum of two equivalent stimulatio ns: one from the cathodal excitation and the other from the anodal inh ibition. The method could be used in clinical studies to detect vestib ular asymmetries and dysfunction. (C) 1997 Elsevier Science B.V.