Sensory system interactions during simultaneous vestibular and visual stimulation in PET

Abstract

The patterns of regional cerebral blood flow (rCBF) increases and decreases in PET were compared for unimodal vestibular, unimodal visual, and for simultaneous vestibular and visual stimulation. Thirteen healthy volunteers were exposed to a) caloric vestibular stimulation, b) small-field visual motion stimulation in roll, c) simultaneous caloric vestibular and visual pattern stimulation. Unimodal vestibular stimulation led to activations of vestibular cortex areas, in particular the parieto-insular vestibular cortex (PIVC), and concurrent deactivations of visual cortical areas [Brodmann area (BA) 17-19]. Unimodal visual motion stimulation led to activations of the striate visual cortex and the motion-sensitive area in the middle temporal/middle occipital gyri (BA 19/37) with concurrent deactivations in the PIVC. Simultaneous bimodal stimulation resulted in activations of the cortical representation of both sensory modalities. In the latter condition activations and deactivations were significantly smaller compared to unimodal stimulation. The findings are consistent with the concept of an inhibitory reciprocal vestibulo-visual interaction in all three stimulus conditions.

Body ownership and embodiment: Vestibular and multisensory mechanisms

“…Accordingly, we propose that this spatial dissociation between self and body location (that is very prominent in out-of-body experiences) might reflect partial disembodiment as it can be observed in patients with autoscopic phenomena in whom vestibular illusions are often associated symptoms [14,17,83] and in healthy subjects using multisensory conflict and virtual reality [84]. This observation is supported by the activation of the vestibular cortex by galvanic vestibular stimulations [6,32,37,46,51,85,110] overlapping with key structures of embodiment such as the TPJ and the temporooccipital cortex [5,16].…”

Contribution of Muscle Strength and Integration of Afferent Input to Postural Instability in Persons with Stroke

“…22 Vice versa, vestibular stimulation through caloric irrigation activates vestibular cortical regions while simultaneously deactivating occipital cortex regions. 22 Thus, when challenged with a task where redundant sensory systems are not available, persons with stroke may require more time to process and integrate sensory information or may be unable to deactivate the necessary cortical areas for re-weighting this sensory input. As a result, stability is compromised and falls occur.…”

Vestibular and visual responses in human posterior insular cortex

“…However, by applying temperatures only through pods and primarily to sites of the ear canal in close vicinity to the pods we reduced the stimulation intensity compared with procedures involving immediate contact of hot or cold medium to the skin surface of the entire ear canal; this is the case for direct injection of water (Deutschländer et al 2002;Dieterich et al 2003;Suzuki et al 2001), tempered air (Naito et al 2003), or nitrogen gas (Fasold et al 2002). Therefore, to increase the likelihood of inducing self-motion sensations with only mild vestibular stimulation, we decided to use bilateral caloric stimulation in our experiments.…”

“…Further support for a more complex organization at the potential cortical vestibular hub comes from contradictory findings on activation patterns during visual motion: on the one hand, activity during stimulation with visual motion seems to be absent or even suppressed in the putative human homologue of primate PIVC (see Deutschländer et al 2002;Dieterich et al 1998;Kleinschmidt et al 2002). On the other hand, previous imaging studies employing visual motion stimuli reported activation at a location that is in close proximity or potentially overlapping with the putative human PIVC (Beer et al 2009;Claeys et al 2003;Orban et al 2003;Sunaert et al 1999).…”