Repeated Galvanic Vestibular Stimulation Modified the Neuronal Potential in the Vestibular Nucleus

Abstract

Vestibular nucleus (VN) and cerebellar flocculus are known as the core candidates for the neuroplasticity of vestibular system. However, it has been still elusive how to induce the artificial neuroplasticity, especially caused by an electrical stimulation, and assess the neuronal information related with the plasticity. To understand the electrically induced neuroplasticity, the neuronal potentials in VN responding to the repeated electrical stimuli were examined. Galvanic vestibular stimulation (GVS) was applied to excite the neurons in VN, and their activities were measured by an extracellular neural recording technique. Thirty-eight neuronal responses (17 for the regular and 21 for irregular neurons) were recorded and examined the potentials before and after stimulation. Two-third of the population (63.2%, 24/38) modified the potentials under the GVS repetition before stimulation (p=0.037), and more than half of the population (21/38, 55.3%) changed the potentials after stimulation (p=0.209). On the other hand, the plasticity-related neuronal modulation was hardly observed in the temporal responses of the neurons. The modification of the active glutamate receptors was also investigated to see if the repeated stimulation changed the number of both types of glutamate receptors, and the results showed that AMPA and NMDA receptors decreased after the repeated stimuli by 28.32 and 16.09%, respectively, implying the modification in the neuronal amplitudes.

Electrical stimulation of the peripheral and central vestibular system

“…To date, however, only a handful of in-vivo studies have investigated how GVS alters signal transmission in central vestibular pathways. One 2020 study assessing how vestibular nuclei neurons encode combined GVS and motion stimulation [45] reported that sub additive responses similar to those reported for the integration of semicircular canal and otolith afferents in these cells [46]. This same group also reported that repeated GVS reduces vestibular nuclei neuronal potentials [45].…”

“…One 2020 study assessing how vestibular nuclei neurons encode combined GVS and motion stimulation [45] reported that sub additive responses similar to those reported for the integration of semicircular canal and otolith afferents in these cells [46]. This same group also reported that repeated GVS reduces vestibular nuclei neuronal potentials [45]. Notably, this reduction was accompanied by a decrease in AMPA and NMDA receptors, leading to proposal that GVS induces a reduction in the number of glutamate receptors that in turn modifies neuronal potentials in the vestibular nucleus.…”

Galvanic vestibular stimulation down-regulated NMDA receptors in vestibular nucleus of PD model

“…The extracellular neural recording in the vestibular nucleus (VN) was performed based on our previous studies 25 , 14 , 20 . The neural recording was initiated by defining a center on the skull.…”

“…Vestibular system is a highly plastic system, and its plastic mediation is built by the molecular and cellular modification [14][15][16][17] . The modified responses are mainly regulated by various types of neurotransmitters, and the glutamate is one of excitatory neurotransmitters, which is known as the most abundant amino acid in the brain 18,19 .…”

“…Galvanic vestibular stimulation (GVS) is known to relieve some motor disabilities, which directly activates the vestibular afferent neurons [22][23][24] . The generated signals are then transmitted to the vestibular nucleus, which is one of the core nuclei converging the incoming sensory information 25,14 . Using the conveyed information by GVS, various affirmative effects were observed in the Parkinson's disease patients; the improvements in the anterior bending posture 26 , in upper and lower extremities 27 , and in body sway 28 .…”