Cortical Projection of Peripheral Vestibular Signaling

Abstract

The cerebral projection of vestibular signaling was studied by using PET with a special differential experimental protocol. Caloric vestibular stimulation (CVS)-induced regional cerebral blood flow (rCBF) changes were investigated in two populations. Butanol perfusion scans were carried out on six healthy volunteers and on six patients following the removal of tumors from the right cerebello pontine angle. The complete loss of the vestibular function postoperatively allowed a comparison of the rCBF changes in the populations with or without this input and offered a promising functional approach whereby to delineate the cortical region most responsive to pure vestibular input. The activations by left-sided and right-sided CVS were determined for both the healthy volunteers and the patient population. Statistical analysis of the data obtained following left-sided CVS did not reveal any cerebral region for which there was a significant difference in CVS-induced response by these two populations. In the case of right-sided CVS, however, the statistical comparison of the CVS-related responses demonstrated a single contralateral area characterized by a significantly different degree of response. This cortical area corresponds to part of the cortical region described recently which can be activated by both CVS and neck vibration. It appears to be anatomically identical to the aggregate of the somatosensory area SII and the retroinsular cortex described in primates, a region identified by other investigators as an analog of the parietoinsular vestibular cortex.

Body ownership and embodiment: Vestibular and multisensory mechanisms

“…Congruently, epileptic patients with vestibular aurae suffer from lesions surrounding the superior temporal gyrus and the temporoparietal cortex [99,107]. This location has also been confirmed by functional neuroimaging studies in healthy subjects using caloric and galvanic stimulation of the peripheral vestibular system revealing unanimously predominant activations centered on the TPJ and insula [6,19,20,32,39,46,47,50,51,70,72,85,94,95,110,112,118] with activations in the superior temporal gyrus, posterior insula, inferior parietal lobule (angular and supramarginal gyri), and postcentral gyrus. Although many regions surrounding the TPJ/insula have been found activated, opinions concerning the exact location of the human homologue of the PIVC differ (Fig.…”

“…Yen Pik Sang et al [120] reported that caloric vestibular stimulations in healthy subjects may induce transient symptoms of depersonalization and derealisation (''body feels strange/different in some ways'', ''feeling of detachment or separation from surroundings'') by a disintegration in personal space and/or disintegration between personal and extrapersonal space. In a PET study on depersonalization, Simeon et al [106] found brain activation changes related to embodiment in regions that have also been shown to be activated by caloric vestibular stimulation, such as the superior temporal gyrus, posterior insula and inferior parietal lobule [19,20,39,47,50,112]. Collectively, these findings suggest that caloric vestibular stimulation interferes with self-processing and embodiment, also inducing symptoms of depersonalization, which share several aspects with out-ofbody experiences [105].…”

“…3B). In somatosensory cortex vestibular stimulations activate the anterior tip of the intraparietal sulcus [50,85,94,112] and the primary somatosensory cortex, near the central sulcus [20,47,50,100]. These regions represent probably the human homologue of two monkey areas that have been found to integrate vestibular and somatosensory information: area 2v, at the base of the intraparietal sulcus [53] and area 3av at the hand/arm and neck/trunk representations [66,96].…”

“…These regions are likely homologous to monkey area 7 [82] and the ventral and medial intraparietal areas [27,77] receiving vestibular information as well as visual, somatosensory and auditory cues. There is finally evidence of vestibular projections to the primary motor and premotor cortices (including also the frontal eye fields), and to the inferior frontal gyrus, in relation to the vestibular control of motor and oculomotor functions [6,47,50,85,94].…”

Mental transformation abilities in patients with unilateral and bilateral vestibular loss

“…Relatively few previous studies have investigated vestibular-cognitive interactions in patients with vestibular disorders, yet relevant literature is growing (for a review see Smith et al 2005;Hanes and McCollum 2006;Borel et al 2008). In this context, it is noteworthy that vestibular sensory information is processed in the central vestibular system including the vestibular nuclei, parts of the cerebellum and the thalamus (Chen-Huang and McCrea 1999;McCrea and Luan 2003;Dieterich and Brandt 2008), along with various cortical regions including the insula and parts of the temporal, parietal, and frontal lobes (Brandt and Dieterich 1999;de Waele et al 2001;Emri et al 2003), and the hippocampus (Vitte et al 1996). Clinical studies revealed impaired performance of vestibular patients in spatial tasks such as spatial perception (Bohmer and Mast 1999a, b;Clement et al 2009), spatial memory, and navigation (Schautzer et al 2003;Brandt et al 2005;Peruch et al 2005).…”