Body ownership alterations emerge from proprioceptive impairment and frontoparietal network damage

2083 

Abstract Submission 

Giulio Mastria¹, Tommaso Bertoni², Henri Perrin³, Nikita Akulenko², Gaia Risso⁴, Michel Akselrod², Eleonora Guanziroli⁵, Franco Molteni⁵, Patric Hagmann⁶, Michela Bassolino⁴, Andrea Serino²

¹Geneva University Hospitaal, Geneva, Geneva, ²CHUV-UNIL, Lausanne, Vaud, ³CHUV, Lausanne, Vaud, ⁴HES-SO Valais-Wallis, Sion, Valais, ⁵Valduce Hospital, Costa Masnaga, Lecco, ⁶Department of Radiology, Lausanne University Hospital and University of Lausanne (CHUV-UNIL), Lausanne, Switzerland

Giulio Mastria  
Geneva University Hospitaal
Geneva, Geneva

Tommaso Bertoni  
CHUV-UNIL
Lausanne, Vaud

Henri Perrin  
CHUV
Lausanne, Vaud

Nikita Akulenko  
CHUV-UNIL
Lausanne, Vaud

Gaia Risso  
HES-SO Valais-Wallis
Sion, Valais

Michel Akselrod  
CHUV-UNIL
Lausanne, Vaud

Eleonora Guanziroli  
Valduce Hospital
Costa Masnaga, Lecco

Franco Molteni  
Valduce Hospital
Costa Masnaga, Lecco

Patric Hagmann  
Department of Radiology, Lausanne University Hospital and University of Lausanne (CHUV-UNIL)
Lausanne, Switzerland

Michela Bassolino  
HES-SO Valais-Wallis
Sion, Valais

Andrea Serino  
CHUV-UNIL
Lausanne, Vaud

The sense of body ownership refers to the feeling that our body belong to us and it plays a crucial role in our perception of our body's position and movement. Alterations in the sense of ownership for the contralesional upper limb are relatively common in the acute phase after cerebral stroke, with patients experiencing difficulties in self-attributing the affected limb, visually perceived, or persistently denying ownership of it (i.e., somatoparaphrenia). Our understanding of the pathophysiological mechanisms underlying these alterations is still poor, limiting the development of effective neurorehabilitative approaches.
Body ownership shares its neural substrate with multisensory integration processes and motor control. According to most accepted accounts, sensorimotor and multisensory integration deficits are key factors determining body ownership alterations in stroke patients; however experimental evidence supporting this view is scarce.

We used a virtual reality reaching task implementing a varying visuo-motor rotation, thus introducing a mismatch in visuo-proprioceptive cues about hand's position during movement execution. We studied the weight attributed to the virtual hand in guiding reaching movements and used it as an implicit proxy of body ownership, which was also assessed by subjective ratings. We modelled body ownership as the product of an online Bayesian inference process, wherein the brain infers ownership over the virtual hand based on the degree of congruency between visual and proprioceptive inputs, influencing the extent of visual adjustments applied to reaching movements. We then performed network based lesion analysis in order to investigate the neural source of body ownership alterations in stroke patients.

We found that stroke patients exhibit an increased tendency to perceive ownership for an incongruent virtual hand and to incorporate it into their motor planning when performing movements with the affected limb, compared to both the intact limb and to a group of age-matched healthy controls. Importantly, this tendency also correlated with diminished ownership for a congruent virtual hand, simulating patient's actual limb. This constitutes novel, quantitative evidence that pathological alterations in subjective body experience affect visuo-proprioceptive sensorimotor loops underlying motor control. The Bayesian inference model effectively explained these alterations as stemming from proprioceptive deficits, reducing the ability to detect visuo-proprioceptive disparities. Finally, through the analysis of brain lesions, we further linked body ownership deficit to alterations in connectivity within the frontoparietal network, affecting connections between the intraparietal sulcus and the supramarginal gyrus with the premotor and dorsolateral prefrontal cortex. This indicates that, besides somatosensory deficits, alterations in body ownership and underlying sensorimotor loops may be attributed to a specific impairment in multisensory integration processes.

This paper provides, for the first time, a quantitative model explaining how somatosensory loss and multisensory integration deficits contribute to body ownership alterations in stroke patients. Moreover, it sheds light on the link between patients' subjective bodily experience and closed-loop motor control. These findings have great relevance for neurorehabilitation: some of the current neurorehabilitation strategies (e.g., prism adaptation, mirror therapy) are based on the manipulation of multisensory feedback, but we have limited knowledge about how the interaction between sensory modalities during functional tasks might affect the efficacy of the intervention. Our framework may be used to predict the capability of a lesioned brain to process and combine multisensory information, supporting body ownership and motor control, and may allow adapting the neurorehabilitation strategy accordingly.

Bayesian Modeling ²

Visuo-Motor Functions ¹

Perception: Multisensory and Crossmodal

Computational Neuroscience

MRI

Neurological

STRUCTURAL MRI

Tractography

WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC

Other - Stroke