Distorted own-body representations in patients with dizziness and during caloric vestibular stimulation

Abstract

There is increasing evidence that vestibular disorders evoke deficits reaching far beyond imbalance, oscillopsia and spatial cognition. Yet, how vestibular disorders affect own-body representations, in particular the perceived body shape and size, has been overlooked. Here, we explored vestibular contributions to own-body representations using two approaches. Study 1 measured the occurrence and severity of distorted own-body representations in 60 patients with dizziness and 60 healthy controls using six items from the Cambridge Depersonalization Scale. 12% of the patients have experienced distorted own-body representations (their hands or feet felt larger or smaller), 37% reported abnormal sense of agency, 35% reported disownership for the body, and 22% reported disembodiment. These proportions were larger in patients than controls. Study 2 aimed at testing whether artificial stimulation of the vestibular apparatus produced comparable distortions of own-body representations in healthy volunteers. We compared the effects of right-warm/left-cold caloric vestibular stimulation (CVS), left-warm/right-cold CVS and sham CVS on internal models of the left and right hands using a pointing task. The perceived length of the dorsum of the hand was increased specifically during left-warm/right-cold CVS, and this effect was found for both hands. Our studies show a vestibular contribution to own-body representations and should help understand the complex symptomatology of patients with dizziness.

The brain-body disconnect: A somatic sensory basis for trauma-related disorders

“…effects on higher self-related constructs such as agency (Synofzik et al, 2008;Lopez et al, 2012;Lenggenhager and Lopez, 2015), embodiment (Schwabe and Blanke, 2008;Ferrè et al, 2014;Macauda et al, 2015;Lopez, 2016;Lopez et al, 2018), self-other distinction and first person perspective (Ferrè et al, 2014), and bodily self-awareness (Lenggenhager et al, 2006(Lenggenhager et al, , 2012Blanke, 2012).…”

“…In corroboration, removing the cortex of young mammals does not appear to compromise the sensorimotor coherence, basic autonomic processes, or raw affective responses required for a brainstem-level sense of self ( Kolb and Tees, 1990 ; Panksepp et al, 1994 ; Shewmon et al, 1999 ; Panksepp, 2005 ; Merker, 2007 ). Further, manipulations of somatic sensory input in healthy adults have cascading effects on higher self-related constructs such as agency ( Synofzik et al, 2008 ; Lopez et al, 2012 ; Lenggenhager and Lopez, 2015 ), embodiment ( Schwabe and Blanke, 2008 ; Ferrè et al, 2014 ; Macauda et al, 2015 ; Lopez, 2016 ; Lopez et al, 2018 ), self-other distinction and first person perspective ( Ferrè et al, 2014 ), and bodily self-awareness ( Lenggenhager et al, 2006 , 2012 ; Blanke, 2012 ).…”

Caloric vestibular stimulation has no effect on perceived body size

“…In this line, it has been discussed that the multisensory (vestibular) cortex in humans 3,4 may serve as a convergence zone of various sensory input, involved in perceiving shape and size of the body and in generating bodily self-representation 1,2,5–8 . In line with these assumptions, studies have reported that vestibular stimulation at the peripheral organ may temporarily increase the perceived length 9,10 and width 9 of the own hands or decrease the perceived width of own thighs 11 . These observations suggested that vestibular information indeed may be used to scale the internal representation of body segments.…”

“…In fact, the previously reported effects of vestibular stimulation on hand size by Lopez et al . 9,10 and on thigh width by Schönherr and May 11 were based on tactile and/or proprioceptive information only; vision was excluded in these experiments. If visual feedback indeed plays this decisive role for the representation of our body image, modulations on the perceived size of arms and legs by vestibular stimulation should only be detected if vision of the extremities is excluded.…”

The disappearing hand: vestibular stimulation does not improve hand localisation

“…neglect, somatoparaphrenia, phantom limb sensations) suggests that vestibular stimulation can attenuate dysfunctional bodily self-consciousness (for reviews see Grabherr, Macauda & Lenggenhager, 2015; Lopez, 2015; Mast et al, 2014). Patients with impaired vestibular function on the other hand are prone to distorted own body representations (Lopez et al, 2018) and out-of-body experiences (Lopez & Elzière, 2018).…”