Peri-personal space as a prior in coupling visual and proprioceptive signals

Abstract It has been suggested that the integration of multiple body-related sources of information within the peri-personal space (PPS) scaffolds body ownership. However, a normative computational framework detailing the functional role of PPS is still missing. Here we cast PPS as a visuo-proprioceptive Bayesian inference problem whereby objects we see in our environment are more likely to engender sensations as they come near to the body. We propose that PPS is the reflection of such an increased a priori probability of visuo-proprioceptive coupling that surrounds the body. To test this prediction, we immersed participants in a highly realistic virtual reality (VR) simulation of their right arm and surrounding environment. We asked participants to perform target-directed reaches toward visual, proprioceptive, and visuo-proprioceptive targets while visually displaying their reaching arm (body visible condition) or not (body invisible condition). Reach end-points are analyzed in light of the coupling prior framework, where the extension of PPS is taken to be represented by the spatial dispersion of the coupling prior between visual and proprioceptive estimates of arm location. Results demonstrate that if the body is not visible, the spatial dispersion of the visuo-proprioceptive coupling relaxes, whereas the strength of coupling remains stable. By demonstrating a distance-dependent alteration in visual and proprioceptive localization attractive pull toward one another (stronger pull at small spatial discrepancies) when the body is rendered invisible – an effect that is well accounted for by the visuo-proprioceptive coupling prior – the results suggest that the visible body grounds visuo-proprioceptive coupling preferentially in the near vs. far space

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Own Body Perception as Bayesian Causal Inference

This dissertation investigates the principles of multisensory integration that underlie the perception of ownership over one's body. To that end, three experimental approaches have been utilized: 1) an investigation of the rubber hand illusion from the perspective of Bayesian causal inference operating in peripersonal space has indicated that this phenomenon is governed by the same principles of statistical inference that govern perception of external objects, 2) an investigation of the same model formulated to operate in the somatotopic space -- that which lines the surface of the body -- revealed that the integration of visual and tactile representations is again governed by the same process of causal inference, and 3) an investigation of the malleability of the somatotopic space has revealed that brief exposure to synchronous visual-tactile pairs at different locations can cause a recalibration of that space. In combination, these three investigations have made use of the Bayesian causal inference model that has been implemented in different ways, in order to model the respective spaces of relevance. Seeking to synthesize a complete account of body ownership, I then proceed to propose a unified account that makes use of the principles of Bayesian causal inference and performs a combined computation that operates in both somatotopic and peripersonal spaces in performing the inference as to which object is my body

Own Body Perception as Bayesian Causal Inference

This dissertation investigates the principles of multisensory integration that underlie the perception of ownership over one's body. To that end, three experimental approaches have been utilized: 1) an investigation of the rubber hand illusion from the perspective of Bayesian causal inference operating in peripersonal space has indicated that this phenomenon is governed by the same principles of statistical inference that govern perception of external objects, 2) an investigation of the same model formulated to operate in the somatotopic space -- that which lines the surface of the body -- revealed that the integration of visual and tactile representations is again governed by the same process of causal inference, and 3) an investigation of the malleability of the somatotopic space has revealed that brief exposure to synchronous visual-tactile pairs at different locations can cause a recalibration of that space. In combination, these three investigations have made use of the Bayesian causal inference model that has been implemented in different ways, in order to model the respective spaces of relevance. Seeking to synthesize a complete account of body ownership, I then proceed to propose a unified account that makes use of the principles of Bayesian causal inference and performs a combined computation that operates in both somatotopic and peripersonal spaces in performing the inference as to which object is my body

Recalibrating the body: visuotactile ventriloquism aftereffect

Visuotactile ventriloquism is a recently reported effect showing that somatotopic tactile representations (namely, representation of location along the surface of one’s arm) can be biased by simultaneous presentation of a visual stimulus in a spatial localization task along the surface of the skin. Here we investigated whether the exposure to discrepancy between tactile and visual stimuli on the skin can induce lasting changes in the somatotopic representations of space. We conducted an experiment investigating this question by asking participants to perform a localization task that included unisensory and bisensory trials, before and after exposure to spatially discrepant visuotactile stimuli. Participants localized brief flashes of light and brief vibrations that were presented along the surface of their forearms, and were presented either individually (unisensory conditions) or were presented simultaneously at the same location or different locations. We then compared the localization of tactile stimuli in unisensory tactile conditions before and after the exposure to discrepant bisensory stimuli. After exposure, participants exhibited a shift in their tactile localizations in the direction of the visual stimulus that was presented during the exposure block. These results demonstrate that the somatotopic spatial representations are capable of rapidly recalibrating after a very brief exposure to visually discrepant stimuli

Perception of body ownership is driven by Bayesian sensory inference.

Recent studies have shown that human perception of body ownership is highly malleable. A well-known example is the rubber hand illusion (RHI) wherein ownership over a dummy hand is experienced, and is generally believed to require synchronized stroking of real and dummy hands. Our goal was to elucidate the computational principles governing this phenomenon. We adopted the Bayesian causal inference model of multisensory perception and applied it to visual, proprioceptive, and tactile stimuli. The model reproduced the RHI, predicted that it can occur without tactile stimulation, and that synchronous stroking would enhance it. Various measures of ownership across two experiments confirmed the predictions: a large percentage of individuals experienced the illusion in the absence of any tactile stimulation, and synchronous stroking strengthened the illusion. Altogether, these findings suggest that perception of body ownership is governed by Bayesian causal inference--i.e., the same rule that appears to govern the perception of outside world

Perception of Body Ownership Is Driven by Bayesian Sensory Inference

<div><p>Recent studies have shown that human perception of body ownership is highly malleable. A well-known example is the rubber hand illusion (RHI) wherein ownership over a dummy hand is experienced, and is generally believed to require synchronized stroking of real and dummy hands. Our goal was to elucidate the computational principles governing this phenomenon. We adopted the Bayesian causal inference model of multisensory perception and applied it to visual, proprioceptive, and tactile stimuli. The model reproduced the RHI, predicted that it can occur without tactile stimulation, and that synchronous stroking would enhance it. Various measures of ownership across two experiments confirmed the predictions: a large percentage of individuals experienced the illusion in the absence of any tactile stimulation, and synchronous stroking strengthened the illusion. Altogether, these findings suggest that perception of body ownership is governed by Bayesian causal inference—i.e., the same rule that appears to govern the perception of outside world.</p></div

Simulation Results: Spatial Extent.

<p>The probability of experiencing the illusion is plotted as a function of the distance (in centimeters) between the rubber hand and the real hand. As the distance between the two increases, the illusion becomes weaker and eventually fails to occur. These results are qualitatively and quantitatively consistent with empirical findings from human participants [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117178#pone.0117178.ref025" target="_blank">25</a>].</p