| Abstract: | In 13 healthy volunteers, we recorded stabilographic postural reactions (side inclinations of the body) to unilateral galvanic
vestibular stimulation (GVS) by rectangular current pulses (4 sec long, 2, 3, 4, 5, or 6 mA). For the cathodal GVS, the dependence
of the magnitude of reaction was linear within this range. The corresponding dependence for the anodal GVS was close to linear
at small currents, but the increment of the magnitude became smaller with further increase in the stimulation intensity, and
a plateau was formed. A significant divergence between the two curves was observed with stimulation currents 4 mA and higher.
This difference can be explained considering modern concepts on the mechanism of GVS-induced effects (an increase or a decrease
in the level of tonic impulsation in fibers of the vestibular nerve under the influence of polarization). Anodal GVS continues
to suppress tonic activity up to the moment where all GVS-sensitive vestibular afferents stop to generate impulses; a further
increase in the intensity of hyperpolarizing current is not accompanied by a decrease in the activity in the vestibular nerve
and, consequently, by an increase in the magnitude of postural reactions. The tested approach can be used for qualitative
estimation of the vestibular tone in humans.
Neirofiziologiya/Neurophysiology, Vol. 37, No. 2, pp. 169–176, March–April, 2005. |
