Abstract
The human vestibular cortex has mostly been approached using functional magnetic resonance imaging and positron emission tomography combined with artificial stimulation of the vestibular receptors or nerve. Few studies have used electroencephalography and benefited from its high temporal resolution to describe the spatiotemporal dynamics of vestibular information processing from the first milliseconds following vestibular stimulation. Evoked potentials (EPs) are largely used to describe neural processing of other sensory signals, but they remain poorly developed and standardized in vestibular neuroscience and neuro-otology. Yet, vestibular EPs of brainstem, cerebellar, and cortical origin have been reported as early as the 1960s. This review article summarizes and compares results from studies that have used a large range of vestibular stimulation, including natural vestibular stimulation on rotating chairs and motion platforms, as well as artificial vestibular stimulation (e.g., sounds, impulsive acceleration stimulation, galvanic stimulation). These studies identified vestibular EPs with short latency (<20 ms), middle latency (from 20 to 50 ms), and late latency (>50 ms). Analysis of the generators (source analysis) of these responses offers new insights into the neuroimaging of the vestibular system. Generators were consistently found in the parieto-insular and temporo-parietal junction—the core of the vestibular cortex—as well as in the prefrontal and frontal areas, superior parietal, and temporal areas. We discuss the relevance of vestibular EPs for basic research and clinical neuroscience and highlight their limitations.
Highlights
The vestibular system has long been associated with postural, oculomotor, and autonomic reflexes
We have reviewed results from pioneering electrophysiological studies and more recent studies using state-of-the-art EEG indicating that VestibularEvoked Potentials (VestEPs) can be considered meaningful electrophysiological signatures of vestibular information processing from the vestibular nerve to the cerebral cortex, owing to the high temporal resolution of EEG
After summarizing the main findings regarding VestEPs with components of short (< 20 ms), middle (20–50 ms), and late (> 50 ms) latency, we discuss how VestEPs studies are informative regarding the parallel vs. hierarchical processing of vestibular signals in the cerebral cortex, and regarding hemispheric dominance of vestibular information processing
Summary
The vestibular system has long been associated with postural, oculomotor, and autonomic reflexes. Recent studies from neuroscience and neurology have provided a large corpus of data showing that vestibular functions reach far beyond oculomotor and postural reflex control [1, 2]. There seems to be no primary vestibular cortex, functional and anatomical data suggest that the parietal operculum (area OP2), the posterior insula, and/or the retroinsular cortex are the core area underpinning vestibular information processing [11, 15,16,17,18]. The operculoinsular and retroinsular cortex is considered the human homologue of the parieto-insular vestibular cortex (PIVC) described in several non-human primate species [19, 20]. Anatomical studies and direct electrophysiological recordings in non-human primates corroborate results from fMRI and PET studies regarding the localization of the vestibular cortex [reviewed in [10]]
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