Three-dimensional spatial characteristics of caloric nystagmus

Abstract

We investigated the three-dimensional spatial characteristics of caloric nystagmus during excitation and inhibition of the lateral semicircular canal in five normal human subjects. Each subject was repositioned in 45 degrees steps at 1-min intervals such that the right lateral semicircular canal plane was reoriented in pitch, from 135 degrees backwards from the upright position to 135 degrees forwards, while the right ear was continuously stimulated with air at 44 degrees C. In orientations in which caloric stimulus resulted in excitation of the right lateral semicircular canal, the eye velocity axis was orthogonal to the average orientation of the right lateral semicircular canal plane. However, in orientations in which caloric stimulus resulted in inhibition of the right lateral semicircular canal, the eye velocity axis was orthogonal to the average orientation of the left and not the right lateral semicircular canal plane. These findings suggest that velocity and direction of caloric nystagmus depend not only on the absolute magnitude of vestibular activity on the stimulated side but also on the differences in activity between the left and right vestibular nuclei, most probably mediated centrally via brainstem commissural pathways.

How vestibular stimulation interacts with illusory hand ownership

“…Second, the duration of GVS can be selected very precisely (with ms-accuracy), whereas it is impossible to stop the caloric stimulation with high temporal accuracy, because the water cannot be removed from the external ear canal that fast and the caloric effects may persist. Finally, we wanted to minimize the visual side effects of the artificial vestibular stimulation and caloric stimulation has been reported to evoke a strong nystagmus (Aw, Haslwanter, Fetter, & Dichgans, 2000), visual illusions and hallucinations (Kolev, 1995;Yen Pik Sang, Jauregui-Renaud, Green, Bronstein, & Gresty, 2006).…”

Impulsive Testing of Individual Semicircular Canal Function

“…1,2 Three-dimensional nystagmus recordings do show some promise for measuring anterior but not for measuring posterior semicircular-canal function. 3,4 Standard rotational tests only measure the function of the two lateral semicircular canals together, and in practice only upS to about 1 Hz. 5 In view of these limitations, we wondered if vestibulo-ocular reflex (VOR) responses to rapid, passive head rotations could be a measure of individual semicircular-canal function in a Address for correspondence: G.M.…”

The human vestibular cortex revealed by coordinate-based activation likelihood estimation meta-analysis

“…When thermal energy is transmitted through the temporal bone to the inner ear, a convective flow of the endolymph is created, stimulating the vestibular sensors in the crista ampullaris of the semicircular canals. CVS stimulates mainly the horizontal semicircular canals, although a weak stimulation of the vertical canals has been reported (Aw et al, 2000). In addition, semicircular canals' signals can influence the neural processing of otolithic signals to modify tilt and translation perception (Merfeld et al, 2005).…”

“…This variability renders difficult the direct comparison of the patterns of activation shown in previous neuroimaging studies. While CVS predominantly stimulates the pathways from the horizontal semicircular canals to the cortex (with a weaker contribution of the anterior and posterior canals, Aw et al, 2000) and interacts with the neural processing of gravito-inertial signals (Peterka et al, 2004), sounds mainly activate pathways running from the saccule to the cerebral cortex (with a potential contribution of the semicircular canals (Xu et al, 2009;see Fig. 1 legend for a detailed description).…”