Ownership illusions in patients with body delusions: Different neural profiles of visual capture and disownership

Abstract

The various neurocognitive processes contributing to the sense of body ownership have been investigated extensively in healthy participants, but studies in neurological patients can shed unique light into such phenomena. Here, we aimed to investigate whether visual capture by a fake hand (without any synchronous or asynchronous tactile stimulation) affects body ownership in a group of hemiplegic patients with or without disturbed sensation of limb ownership (DSO) following damage to the right hemisphere. We recruited 31 consecutive patients, including seven patients with DSO. The majority of our patients (64.5% overall and up to 86% of the patients with DSO) experienced strong feelings of ownership over a rubber hand within 15 sec following mere visual exposure, which correlated with the degree of proprioceptive deficits across groups and in the DSO group. Using voxel-based lesion-symptom mapping analysis, we were able to identify lesions associated with this pathological visual capture effect in a selective fronto-parietal network, including significant voxels (p < .05) in the frontal operculum and the inferior frontal gyrus. By contrast, lesions associated with DSO involved more posterior lesions, including the right temporoparietal junction and a large area of the supramarginal gyrus, and to a lesser degree the middle frontal gyrus. Thus, this study suggests that our sense of ownership includes dissociable mechanisms of multisensory integration.

Welcoming back my arm: Affective touch increases body ownership following right hemisphere stroke

“…However, our exploratory VLSM using less restrictive criteria revealed that lesions in the insula and corpus callosum, and, resulted in significantly less increase in body ownership following other-affective touch. These findings are consistent with the proposed role of the insula in body awareness, as well as the importance of white matter tracts in self-awareness (Pacella et al, 2019) and body ownership (Moro et al, 2016;Martinaud et al, 2017) and warrant further study.…”

“…First, affective touch may reduce the unusual, sensory symptoms often reported by right hemisphere stroke patients, in particular "feelings of deafference". We have previously argued that DSO may be the result of an inability to integrate current sensory signals with prior expectations about the sensory state of the body (Martinaud et al, 2017). Hence, disownership may occur when patients are unable to use current, aberrant signals from the body (e.g.…”

“…Although it can be hard to systematically sample such subjective, spontaneous feelings by the bedside, in a previous study we showed that DSO may be at least partly explained as sensations about the affected arm, which cannot be explained by existing top-down expectations of selfhood (Martinaud et al, 2017). Specifically, we found that almost all of our sample of patients with right perisylvian lesions (N = 31), with and without DSO symptoms, experienced feelings of ownership over a rubber hand within 15 seconds and without any tactile stimulation (a phenomenon termed visual capture of ownership, VOC).…”

Vestibular modulation of multisensory integration during actual and vicarious tactile stimulation

“…The vestibular system may reduce the relative weight of somatosensory stimuli while increasing the relevance of exteroceptive ones in order to allow the resolution of perceptual ambiguity (Zeller, Litvak, Friston, & Classen, ). This would be consistent with the visual capture effects observed in stroke patients with right peri‐sylvian lesions (Martinaud et al, ) and with reports of symptoms remission following right‐hemisphere vestibular stimulation in patients with dis‐ownership feelings (Bisiach, Rusconi, & Vallar, ; Rode et al, ).…”

“…Moreover, the enhancement of proprioceptive drift during right vestibular stimulation was greater following affective compared with neutral touch conditions. These findings were interpreted as a right-hemisphere stimulation-induced enhancement of vision over proprioception (see also Martinaud, Besharati, Jenkinson, & Fotopoulou, 2017;Samad, Chung, & Shams, 2015). However, the specific mechanism by which touch enhances body ownership during LGVS remains unclear.…”