Modulation of Memory by Vestibular Lesions and Galvanic Vestibular Stimulation

Abstract

For decades it has been speculated that there is a close association between the vestibular system and spatial memories constructed by areas of the brain such as the hippocampus. While many animal studies have been conducted which support this relationship, only in the last 10 years have detailed quantitative studies been carried out in patients with vestibular disorders. The majority of these studies suggest that complete bilateral vestibular loss results in spatial memory deficits that are not simply due to vestibular reflex dysfunction, while the effects of unilateral vestibular damage are more complex and subtle. Very recently, reports have emerged that sub-threshold, noisy galvanic vestibular stimulation can enhance memory in humans, although this has not been investigated for spatial memory as yet. These studies add to the increasing evidence that suggests a connection between vestibular sensory information and memory in humans.

Vestibular stimulation enhances hippocampal long-term potentiation via activation of cholinergic septohippocampal cells

“…Besides participating in formation of spatial memory [3,88,89], septohippocampal cholinergic neurons may also be important for sensorimotor processing in which activation of the vestibular system provides a sensory signal to assist in motor planning [90]. A number of studies have demonstrated that vestibular stimulation can improve cognition in humans (reviewed in [91][92][93]). Given that synaptic plasticity is altered in patients with Alzheimer's disease [94] and degeneration of basal forebrain cholinergic neurons is a pathological hallmark of this disease [14,15,95,96], vestibular stimulation may provide a novel treatment to improve hippocampus-dependent cognitive deficits in affected patients.…”

Noisy Galvanic Vestibular Stimulation Modulates the Amplitude of EEG Synchrony Patterns

“…The fact that noisy GVS modulated alpha, beta and gamma power in occipital electrodes O1 and O2, which corresponds to the striate cortex [70], is not surprising. GVS has been previously demonstrated to enhance visual processing, such as visual memory recall in normal subjects [12] and spatial processing performance in stroke patients [15], [17], [71], [72]. A more remarkable observation, however, is that theta, alpha and gamma power were significantly modulated throughout prefrontal and parietal (Pz/P4) electrodes, which correspond to the precuneus [70].…”

Sensorintegrative dysfunction underlying vestibular disorders after traumatic brain injury: A review

“…Stimulation of vestibular periphery has been shown to have therapeutic benefits for cognition (see Smith et al [57]) and persistent pain [58]. Although untested as of yet, additional possibilities exist for intermodal benefits from peripheral stimulation, such as hearing and vision improvements or anxiety reduction from vestibular training.…”