Reliability-based weighting of visual and vestibular cues in displacement estimation

Contains fulltext : 150540.pdf (publisher's version ) (Open Access)When navigating through the environment, our brain needs to infer how far we move and in which direction we are heading. In this estimation process, the brain may rely on multiple sensory modalities, including the visual and vestibular systems. Previous research has mainly focused on heading estimation, showing that sensory cues are combined by weighting them in proportion to their reliability, consistent with statistically optimal integration. But while heading estimation could improve with the ongoing motion, due to the constant flow of information, the estimate of how far we move requires the integration of sensory information across the whole displacement. In this study, we investigate whether the brain optimally combines visual and vestibular information during a displacement estimation task, even if their reliability varies from trial to trial. Participants were seated on a linear sled, immersed in a stereoscopic virtual reality environment. They were subjected to a passive linear motion involving visual and vestibular cues with different levels of visual coherence to change relative cue reliability and with cue discrepancies to test relative cue weighting. Participants performed a two-interval two-alternative forced-choice task, indicating which of two sequentially perceived displacements was larger. Our results show that humans adapt their weighting of visual and vestibular information from trial to trial in proportion to their reliability. These results provide evidence that humans optimally integrate visual and vestibular information in order to estimate their body displacement.15 p

Weighted visual and vestibular cues for spatial updating during passive self-motion

When walking or driving, it is of the utmost importance to continuously track the spatial relationship between objects in the environment and the moving body in order to prevent collisions. Although this process of spatial updating occurs naturally, it involves the processing of a myriad of noisy and ambiguous sensory signals. Here, using a psychometric approach, we investigated the integration of visual optic flow and vestibular cues in spatially updating a remembered target position during a linear displacement of the body. Participants were seated on a linear sled, immersed in a stereoscopic virtual reality environment. They had to remember the position of a target, briefly presented before a sideward translation of the body involving supra-threshold vestibular cues and whole-field optic flow that provided slightly discrepant motion information. After the motion, using a forced response participants indicated whether the location of a brief visual probe was left or right of the remembered target position. Our results show that in a spatial updating task involving passive linear self-motion humans integrate optic flow and vestibular self-displacement information according to a weighted-averaging process with, across subjects, on average about four times as much weight assigned to the visual compared to the vestibular contribution (i.e., 79% visual weight). We discuss our findings with respect to previous literature on the effect of optic flow on spatial updating performance

Feasibility and safety of intranasally administered mesenchymal stromal cells after perinatal arterial ischaemic stroke in the Netherlands (PASSIoN): a first-in-human, open-label intervention study

Background: Perinatal arterial ischaemic stroke (PAIS) is an important cause of neurodevelopmental disabilities. In this first-in-human study, we aimed to assess the feasibility and safety of intranasally delivered bone marrow-derived allogeneic mesenchymal stromal cells (MSCs) to treat PAIS in neonates. Methods: In this open-label intervention study in collaboration with all neonatal intensive care units in the Netherlands, we included neonates born at full term (>= 36 weeks of gestation) with MRI-confirmed PAIS in the middle cerebral artery region. All eligible patients were transferred to the neonatal intensive care unit of the Wilhelmina Children's Hospital. Neonates received one dose of 45-50 x 10(6) bone-marrow derived MSCs intranasally within 7 days of presenting signs of PAIS. The primary endpoints were acute and subacute safety outcomes, including vital signs, blood markers, and the occurrence of toxicity, adverse events, and serious adverse events. The occurrence of unexpected cerebral abnormalities by a repeat MRI at 3 months of age was a secondary endpoint. As part of standard clinical follow-up at Wilhelmina Children's Hospital, we assessed corticospinal tract development on MRI and performed motor assessments at 4 months of age. This study is registered with ClinicalTrials.gov, NCT03356821. Findings: Between Feb 11, 2020, and April 29, 2021, ten neonates were enrolled in the study. Intranasal administration of MSCs was well tolerated in all ten neonates. No serious adverse events were observed. One adverse event was seen: a mild transient fever of 38 degrees C without the need for clinical intervention. Blood inflammation markers (C-reactive protein, procalcitonin, and leukocyte count) were not significantly different pre-administration versus postadministration and, although thrombocyte levels increased (p=0.011), all were within the physiological range. Followup MRI scans did not show unexpected structural cerebral abnormalities. All ten patients had initial pre-Wallerian changes in the corticospinal tracts, but only four (40%) patients showed asymmetrical corticospinal tracts at follow-up MRI. Abnormal early motor assessment was found in three (30%) infants. Interpretation: This first-in-human study demonstrates that intranasal bone marrow-derived MSC administration in neonates after PAIS is feasible and no serious adverse events were observed in patients followed up until 3 months of age. Future large-scale placebo-controlled studies are needed to determine the therapeutic effect of intranasal MSCs for PAIS. Copyright (C) 2022 Published by Elsevier Ltd. All rights reserved.</p