Vestibulothalamic projections in man--a sixth primary sensory pathway

Abstract

1. Responses suggesting activation of the vestibular system, elicited by electrical stimulation of the human thalamus during 22 routine stereotaxic neurosurgical procedures, were examined in a retrospective study to determine the possible existence of vestibulothalamo-cortical projections in man. 2. Such responses were most frequently described as sensations of movement through space and were associated with two distinct vestibulothalamic projections: a) an anterior relay was situated ventral to the medial lemniscus, passing lateral to the red nucleus and dorsal to the subthalamic nucleus prior to terminating in the nucleus ventrointermedius (Vim) (comparable to VPLo in primates); b) a posterior relay associated with the auditory pathway (lateral lemniscus and brachium of the inferior colliculus) projected to the medial geniculate body. 3. The production of sensations of motion in conscious patients by stimulating areas that are similar to those reported constituting vestibulothalamic pathways in cats and primates implies a distinct primary sensory cortical projection for processing information from the vestibular receptors pertaining to the recognition of spatial movements.

The thalamocortical vestibular system in animals and humans

“…Hawrylyshyn et al (1978) were able to evoke in conscious patients sensations of movement by stimulating a vestibulothalamic pathway "situated ventral to the medial lemniscus, passing lateral to the red nucleus and dorsal to the subthalamic nucleus prior to terminating in the Vim." A more recent study using H 2 15 O PET measurements demonstrated projections of the Vim to the parieto-insular vestibular cortex (PIVC), the main vestibular cortical area (Ceballos-Baumann et al, 2001).…”

“…Therefore, by relaying vestibular cues, and particularly graviceptive cues, this thalamic region could be involved in encoding gravity and controlling body orientation in space. Finally, a contribution of the MGN has also been suggested in humans during neurosurgical explorations of the thalamus (Hawrylyshyn et al, 1978). Sensations of movements through space were evoked during the stimulation of a vestibulothalamic pathway "associated with the auditory pathway (lateral lemniscus and brachium of the inferior colliculus)" to the MGN.…”

Investigation of the Surgical Target for Alleviation of Involuntary Movement Disorders

“…Two ves tibular paths are represented, one traversing the lateral lemniscus and medial geniculate, the other the subthalamus and the target area in V.i.m. [3].…”

What Goes on in the Motor Thalamus?

“…Apparently intermingled with kinesthetic cells, we have found evi dence with macrostimulation, but not yet with microstimulation, for the rostral vestibulothalamic pathway described in subhuman primates, the stimulation of which induces a feeling of faintness, nausea or vertigo [17].…”