Multisensory Integration Processes Research Articles

Virtual dynamic interaction games reveal impaired multisensory integration in women with migraine.

In this cross-sectional observational study, we aimed to investigate sensory profiles and multisensory integration processes in women with migraine using virtual dynamic interaction systems. Compared to studies on unimodal sensory processing, fewer studies show that multisensory integration differs in patients with migraine. Multisensory integration of visual, auditory, verbal, and haptic modalities has not been evaluated in migraine. A 12-min virtual dynamic interaction game consisting of four parts was played by the participants. During the game, the participants were exposed to either visual stimuli only or multisensory stimuli in which auditory, verbal, and haptic stimuli were added to the visual stimuli. A total of 78 women participants (28 with migraine without aura and 50 healthy controls) were enrolled in this prospective exploratory study. Patients with migraine and healthy participants who met the inclusion criteria were randomized separately into visual and multisensory groups: Migraine multisensory (14 adults), migraine visual (14 adults), healthy multisensory (25 adults), and healthy visual (25 adults). The Sensory Profile Questionnaire was utilized to assess the participants' sensory profiles. The game scores and survey results were analyzed. In visual stimulus, the gaming performance scores of patients with migraine without aura were similar to the healthy controls, at a median (interquartile range [IQR]) of 81.8 (79.5-85.8) and 80.9 (77.1-84.2) (p = 0.149). Error rate of visual stimulus in patients with migraine without aura were comparable to healthy controls, at a median (IQR) of 0.11 (0.08-0.13) and 0.12 (0.10-0.14), respectively (p = 0,166). In multisensory stimulation, average gaming score was lower in patients with migraine without aura compared to healthy individuals (median [IQR] 82.2 [78.8-86.3] vs. 78.6 [74.0-82.4], p = 0.028). In women with migraine, exposure to new sensory modality upon visual stimuli in the fourth, seventh, and tenth rounds (median [IQR] 78.1 [74.1-82.0], 79.7 [77.2-82.5], 76.5 [70.2-82.1]) exhibited lower game scores compared to visual stimuli only (median [IQR] 82.3 [77.9-87.8], 84.2 [79.7-85.6], 80.8 [79.0-85.7], p = 0.044, p = 0.049, p = 0.016). According to the Sensory Profile Questionnaire results, sensory sensitivity, and sensory avoidance scores of patients with migraine (median [IQR] score 45.5 [41.0-54.7] and 47.0 [41.5-51.7]) were significantly higher than healthy participants (median [IQR] score 39.0 [34.0-44.2] and 40.0 [34.0-48.0], p < 0.001, p = 0.001). The virtual dynamic game approach showed for the first time that the gaming performance of patients with migraine without aura was negatively affected by the addition of auditory, verbal, and haptic stimuli onto visual stimuli. Multisensory integration of sensory modalities including haptic stimuli is disturbed even in the interictal period in women with migraine. Virtual games can be employed to assess the impact of sensory problems in the course of the disease. Also, sensory training could be a potential therapy target to improve multisensory processing in migraine.

Evolution of neural circuitry and cognition.

Neural circuits govern the interface between the external environment, internal cues and outwardly directed behaviours. To process multiple environmental stimuli and integrate these with internal state requires considerable neural computation. Expansion in neural network size, most readily represented by whole brain size, has historically been linked to behavioural complexity, or the predominance of cognitive behaviours. Yet, it is largely unclear which aspects of circuit variation impact variation in performance. A key question in the field of evolutionary neurobiology is therefore how neural circuits evolve to allow improved behavioural performance or innovation. We discuss this question by first exploring how volumetric changes in brain areas reflect actual neural circuit change. We explore three major axes of neural circuit evolution-replication, restructuring and reconditioning of cells and circuits-and discuss how these could relate to broader phenotypes and behavioural variation. This discussion touches on the relevant uses and limitations of volumetrics, while advocating a more circuit-based view of cognition. We then use this framework to showcase an example from the insect brain, the multi-sensory integration and internal processing that is shared between the mushroom bodies and central complex. We end by identifying future trends in this research area, which promise to advance the field of evolutionary neurobiology.

Separation of bimodal fMRI responses in mouse somatosensory areas into V1 and non-V1 contributions

Multisensory integration is necessary for the animal to survive in the real world. While conventional methods have been extensively used to investigate the multisensory integration process in various brain areas, its long-range interactions remain less explored. In this study, our goal was to investigate interactions between visual and somatosensory networks on a whole-brain scale using 15.2-T BOLD fMRI. We compared unimodal to bimodal BOLD fMRI responses and dissected potential cross-modal pathways with silencing of primary visual cortex (V1) by optogenetic stimulation of local GABAergic neurons. Our data showed that the influence of visual stimulus on whisker activity is higher than the influence of whisker stimulus on visual activity. Optogenetic silencing of V1 revealed that visual information is conveyed to whisker processing via both V1 and non-V1 pathways. The first-order ventral posteromedial thalamic nucleus (VPM) was functionally affected by non-V1 sources, while the higher-order posterior medial thalamic nucleus (POm) was predominantly modulated by V1 but not non-V1 inputs. The primary somatosensory barrel field (S1BF) was influenced by both V1 and non-V1 inputs. These observations provide valuable insights for into the integration of whisker and visual sensory information.

Multisensory mechanisms of gait and balance in Parkinson’s disease: an integrative review

Understanding the neural underpinning of human gait and balance is one of the most pertinent challenges for 21st-century translational neuroscience due to the profound impact that falls and mobility disturbances have on our aging population. Posture and gait control does not happen automatically, as previously believed, but rather requires continuous involvement of central nervous mechanisms. To effectively exert control over the body, the brain must integrate multiple streams of sensory information, including visual, vestibular, and somatosensory signals. The mechanisms which underpin the integration of these multisensory signals are the principal topic of the present work. Existing multisensory integration theories focus on how failure of cognitive processes thought to be involved in multisensory integration leads to falls in older adults. Insufficient emphasis, however, has been placed on specific contributions of individual sensory modalities to multisensory integration processes and cross-modal interactions that occur between the sensory modalities in relation to gait and balance. In the present work, we review the contributions of somatosensory, visual, and vestibular modalities, along with their multisensory intersections to gait and balance in older adults and patients with Parkinson’s disease. We also review evidence of vestibular contributions to multisensory temporal binding windows, previously shown to be highly pertinent to fall risk in older adults. Lastly, we relate multisensory vestibular mechanisms to potential neural substrates, both at the level of neurobiology (concerning positron emission tomography imaging) and at the level of electrophysiology (concerning electroencephalography). We hope that this integrative review, drawing influence across multiple subdisciplines of neuroscience, paves the way for novel research directions and therapeutic neuromodulatory approaches, to improve the lives of older adults and patients with neurodegenerative diseases.

Multisensory perception depends on the reliability of the type of judgment.

The brain engages the processes of multisensory integration and recalibration to deal with discrepant multisensory signals. These processes consider the reliability of each sensory input, with the more reliable modality receiving the stronger weight. Sensory reliability is typically assessed via the variability of participants' judgments, yet these can be shaped by factors both external and internal to the nervous system. For example, motor noise and participant's dexterity with the specific response method contribute to judgment variability, and different response methods applied to the same stimuli can result in different estimates of sensory reliabilities. Here we ask how such variations in reliability induced by variations in the response method affect multisensory integration and sensory recalibration, as well as motor adaptation, in a visuomotor paradigm. Participants performed center-out hand movements and were asked to judge the position of the hand or rotated visual feedback at the movement end points. We manipulated the variability, and thus the reliability, of repeated judgments by asking participants to respond using either a visual or a proprioceptive matching procedure. We find that the relative weights of visual and proprioceptive signals, and thus the asymmetry of multisensory integration and recalibration, depend on the reliability modulated by the judgment method. Motor adaptation, in contrast, was insensitive to this manipulation. Hence, the outcome of multisensory binding is shaped by the noise introduced by sensorimotor processing, in line with perception and action being intertwined.NEW & NOTEWORTHY Our brain tends to combine multisensory signals based on their respective reliability. This reliability depends on sensory noise in the environment, noise in the nervous system, and, as we show here, variability induced by the specific judgment procedure.

Sensory dominances depend on the wine quality dimension

The definition of the term “organoleptic quality” in sensory evaluation of food products does not seem to be consensual. Descriptive or liking methods are generally used to differentiate between wines. Nevertheless, quality evaluation of a product such as wine is defined as an integrated impression, like acceptability, pleasure, aesthetic or emotional experiences during tasting. According to the ‘modality appropriateness’ hypothesis which predicts that wine tasters weigh the most suitable sensory inputs for a specific assessment, the nature of the quality dimensions may modulate sensory influences. The aim of the present study was to evaluate whether the dominant senses during wine assessment depend on the wine quality dimension being evaluated: emotional and aesthetic approaches, assessment of the exemplarity to a PDO, or liking. Expert wine tasters assessed these questions on twenty wines repeatedly, under different tasting conditions: global (all senses), unimodal (visual, smell and taste), and combined senses (visual/smell, visual/in-mouth sensations and olfaction/in-mouth sensations). Psychometric index and regression models suggested a dominance of smell in emotional, and aesthetic assessments, and of visual dominance for exemplarity decisions. Liking is a more plural composite model of wine assessment. As these different dimensions do not share the same multisensory integration processes, quality assessments require a more holistic and multidimensional approach.

Cross-modal exposure restores multisensory enhancement after hemianopia.

Hemianopia is a common consequence of unilateral damage to visual cortex that manifests as a profound blindness in contralesional space. A noninvasive cross-modal (visual-auditory) exposure paradigm has been developed in an animal model to ameliorate this disorder. Repeated stimulation of a visual-auditory stimulus restores overt responses to visual stimuli in the blinded hemifield. It is believed to accomplish this by enhancing the visual sensitivity of circuits remaining after a lesion of visual cortex; in particular, circuits involving the multisensory neurons of the superior colliculus. Neurons in this midbrain structure are known to integrate spatiotemporally congruent visual and auditory signals to amplify their responses, which, in turn, enhances behavioral performance. Here we evaluated the relationship between the rehabilitation of hemianopia and this process of multisensory integration. Induction of hemianopia also eliminated multisensory enhancement in the blinded hemifield. Both vision and multisensory enhancement rapidly recovered with the rehabilitative cross-modal exposures. However, although both reached pre-lesion levels at similar rates, they did so with different spatial patterns. The results suggest that the capability for multisensory integration and enhancement is not a pre-requisite for visual recovery in hemianopia, and that the underlying mechanisms for recovery may be more complex than currently appreciated.

Metacognitive awareness in the sound-induced flash illusion.

Hundreds (if not thousands) of multisensory studies provide evidence that the human brain can integrate temporally and spatially discrepant stimuli from distinct modalities into a singular event. This process of multisensory integration is usually portrayed in the scientific literature as contributing to our integrated, coherent perceptual reality. However, missing from this account is an answer to a simple question: how do confidence judgements compare between multisensory information that is integrated across multiple sources, and multisensory information that comes from a single, congruent source in the environment? In this paper, we use the sound-induced flash illusion to investigate if confidence judgements are similar across multisensory conditions when the numbers of auditory and visual events are the same, and the numbers of auditory and visual events are different. Results showed that congruent audiovisual stimuli produced higher confidence than incongruent audiovisual stimuli, even when the perceptual report was matched across the two conditions. Integrating these behavioural findings with recent neuroimaging and theoretical work, we discuss the role that prefrontal cortex may play in metacognition, multisensory causal inference and sensory source monitoring in general. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

Different time scales of common-cause evidence shape multisensory integration, recalibration and motor adaptation.

Perceptual coherence in the face of discrepant multisensory signals is achieved via the processes of multisensory integration, recalibration and sometimes motor adaptation. These supposedly operate on different time scales, with integration reducing immediate sensory discrepancies and recalibration and motor adaptation reflecting the cumulative influence of their recent history. Importantly, whether discrepant signals are bound during perception is guided by the brains' inference of whether they originate from a common cause. When combined, these two notions lead to the hypothesis that the time scales on which integration and recalibration (or motor adaptation) operate are associated with different time scales of evidence about a common cause underlying two signals. We tested this prediction in a well-established visuo-motor paradigm, in which human participants performed visually guided hand movements. The kinematic correlation between hand and cursor movements indicates their common origin, which allowed us to manipulate the common-cause evidence by titrating this correlation. Specifically, we dissociated hand and cursor signals during individual movements while preserving their correlation across the series of movement endpoints. Following our hypothesis, this manipulation reduced integration compared with a condition in which visual and proprioceptive signals were perfectly correlated. In contrast, recalibration and motor adaption were not affected by this manipulation. This supports the notion that multisensory integration and recalibration deal with sensory discrepancies on different time scales guided by common-cause evidence: Integration is prompted by local common-cause evidence and reduces immediate discrepancies, whereas recalibration and motor adaptation are prompted by global common-cause evidence and reduce persistent discrepancies.

Is the rubber hand illusion associated with somatic symptom reporting?

Current approaches to somatic symptom perception conceptualize somatic symptoms partly as somato-visceral or body illusions evoked by an interaction between bottom-up (sensory) and top-down (expectations, attention) processes. Similar processes of multisensory integration are assumed to contribute to the rubber hand illusion (RHI). Findings concerning the strength and direction of associations between these two phenomena, symptom perception and the RHI, are equivocal. Individuals of a non-clinical sample (N = 63; 56% females; Mage = 20.4; SD = 1.6) completed the Patient Health Questionnaire Somatic Symptom Scale (PHQ-15) and participated in an experiment that evoked the RHI. In repeated measures analyses of variance with the PHQ-15 score as covariate, no significant interaction effects between the PHQ-15 score and indicators of the RHI, i.e., proprioceptive drift (F(1,61) < 0.001 p = 0.993, partial η2 < 0.001; BF10 = 0.307), felt body ownership(F(1,59) = 0.043, p = 0.836, partial η2 = 0,001; BF10 = 0.501), and felt body disownership (F(1,59) = 0.148, p = 0.702, partial η2 = 0.002; BF10 = 1.972) were found. Overall, frequentist and Bayesian analysis indicated that the support for a possible association between the PHQ-15 and indicators of the RHI remains inconclusive, i.e., neither the null nor the alternative hypotheses were sufficiently supported. At least in this non-clinical sample, the association between somatic symptom distress and the strength of the RHI appears so weak (perhaps non-existing), that both phenomena (somatic symptom distress and the RHI) appear distinct and largely unrelated.

Eating, Smelling, and Seeing: Investigating Multisensory Integration and (In)congruent Stimuli while Eating in VR.

Integrating taste in AR/VR applications has various promising use cases - from social eating to the treatment of disorders. Despite many successful AR/VR applications that alter the taste of beverages and food, the relationship between olfaction, gustation, and vision during the process of multisensory integration (MSI) has not been fully explored yet. Thus, we present the results of a study in which participants were confronted with congruent and incongruent visual and olfactory stimuli while eating a tasteless food product in VR. We were interested (1) if participants integrate bi-modal congruent stimuli and (2) if vision guides MSI during congruent/incongruent conditions. Our results contain three main findings: First, and surprisingly, participants were not always able to detect congruent visual-olfactory stimuli when eating a portion of tasteless food. Second, when confronted with tri-modal incongruent cues, a majority of participants did not rely on any of the presented cues when forced to identify what they eat; this includes vision which has previously been shown to dominate MSI. Third, although research has shown that basic taste qualities like sweetness, saltiness, or sourness can be influenced by congruent cues, doing so with more complex flavors (e.g., zucchini or carrot) proved to be harder to achieve. We discuss our results in the context of multimodal integration, and within the domain of multisensory AR/VR. Our results are a necessary building block for future human-food interaction in XR that relies on smell, taste, and vision and are foundational for applied applications such as affective AR/VR.

Computational modeling of human multisensory spatial representation by a neural architecture.

Our brain constantly combines sensory information in unitary percept to build coherent representations of the environment. Even though this process could appear smooth, integrating sensory inputs from various sensory modalities must overcome several computational issues, such as recoding and statistical inferences problems. Following these assumptions, we developed a neural architecture replicating humans' ability to use audiovisual spatial representations. We considered the well-known ventriloquist illusion as a benchmark to evaluate its phenomenological plausibility. Our model closely replicated human perceptual behavior, proving a truthful approximation of the brain's ability to develop audiovisual spatial representations. Considering its ability to model audiovisual performance in a spatial localization task, we release our model in conjunction with the dataset we recorded for its validation. We believe it will be a powerful tool to model and better understand multisensory integration processes in experimental and rehabilitation environments.

Are Linguistic and Motricity domains intertwined in Schizophrenia? A preliminary analysis.

IntroductionThe disruption of minimal Self is believed to be a core element of Schizophrenia and intimately connected to a disruption of bodily self, which in turn leads to impairments in intersubjectivity dimension. Motor abnormalities have been associated to Schizophrenia since the early conceptualization of the disorder, as well as inefficient body-related multisensory integration processes are considered nowadays a plausible origin of disembodied Self. In particular, there is evidence for significant abnormalities in Peripersonal Space (PPS) extension in Schizophrenia patients. PPS is the plastic sector of space immediately surrounding our body, whose coherent representation is based on efficient body-related multisensory integration processes. With a specific experimental task based on multisensory integration processing, we estimated PPS size and PPS boundary’s demarcation in 27 Schizophrenia patients, confirming a narrower PPS size and weaker bodily boundary in patients, thus paving the way for a deeper investigation of the mechanisms underlying the disruption of bodily self (Ferroni et al., Schziophr.Bull.2022, 5 1085-1093). We suggest that disembodiment might be responsible for the loss of the immediate linkage between Self and others (“intercorporeality”), so linking the disruption of the corporeal dimension to specific anomalies of intersubjectivity in Schizophrenia patients. Since language is one of the most important instrument through which intersubjectivity unfolds, it is intriguing to hypothesize a connection between language and multi-sensory processing.ObjectivesTherefore, the present study was aimed at investigating possible correlations between patients’ motor impairments in multi-sensory integration processes and their alterations in language and communicative interactions.MethodsTwenty-five outpatients were recruited in an experimental task investigating PPS extension; they were administered the Scale for the Assessment of Thought, Language and Communication (TLC) and the Clinical Language Disorder Rating Scale (CLANG).ResultsOur data showed significant correlations between TLC and CLANG total scores and PPS size, with narrower PPS size for more severe formal thought disorders and higher language and communication impairments.ConclusionsOur preliminary results seem to confirm the presence of a link between language impairment and multi-sensory processing, suggesting that bodily and linguistic disorganization may have a common origin which has yet to be explored in depth. Future research is needed to identify linguistic and motor endophenotypic patterns, potentially intertwined with each other, capable of early predicting Schizophrenia development and thus usable as early diagnostic tools.Disclosure of InterestNone Declared

Exploring multisensory integration of non-naturalistic sounds on body perception in young females with eating disorders symptomatology: a study protocol

BackgroundBodily illusions can be used to investigate the experience of being in a body by manipulating the underlying processes of multisensory integration. Research suggests that people with eating disorders (EDs) may have impairments in visual, interoceptive, proprioceptive, and tactile bodily perception. Furthermore, people with EDs also show abnormalities in integrating multisensory visuo-tactile and visual-auditory signals related to the body, which may contribute to the development of body image disturbances. Visuo-auditory integration abnormalities have been observed also in people with subthreshold ED symptomatology. However, it remains unclear whether these impairments are specific to bodily signals or if they extend to any auditory signals.MethodsWe will recruit 50 participants (aged 18–24; females assigned at birth) with ED symptomatology (subthreshold group) and 50 control participants. The Eating Disorder Examination Questionnaire will be administered to screen for ED symptomatology and divide the sample into two groups accordingly (control and subthreshold group using a clinical cut-off score of 2.8). The strength of both illusions will be measured implicitly with estimations of body part position and size, and explicitly with self-report questionnaires. As a secondary aim, regression analysis will be run to test the predictive role of susceptibility for both illusions on interoceptive body awareness (measured by the Multidimensional Assessment of Interoceptive Awareness Scale) and sensory-processing sensitivity (measured by the Highly Sensitive Person Scale).DiscussionOur study may contribute to our understanding of the mechanisms underlying body image disturbances. The results may pave the way for novel clinical interventions targeting early symptoms prior to the development of the disorder in young females.

Multisensory benefits for speech recognition in noisy environments.

A series of our previous studies explored the use of an abstract visual representation of the amplitude envelope cues from target sentences to benefit speech perception in complex listening environments. The purpose of this study was to expand this auditory-visual speech perception to the tactile domain. Twenty adults participated in speech recognition measurements in four different sensory modalities (AO, auditory-only; AV, auditory-visual; AT, auditory-tactile; AVT, auditory-visual-tactile). The target sentences were fixed at 65 dB sound pressure level and embedded within a simultaneous speech-shaped noise masker of varying degrees of signal-to-noise ratios (-7, -5, -3, -1, and 1 dB SNR). The amplitudes of both abstract visual and vibrotactile stimuli were temporally synchronized with the target speech envelope for comparison. Average results showed that adding temporally-synchronized multimodal cues to the auditory signal did provide significant improvements in word recognition performance across all three multimodal stimulus conditions (AV, AT, and AVT), especially at the lower SNR levels of -7, -5, and -3 dB for both male (8-20% improvement) and female (5-25% improvement) talkers. The greatest improvement in word recognition performance (15-19% improvement for males and 14-25% improvement for females) was observed when both visual and tactile cues were integrated (AVT). Another interesting finding in this study is that temporally synchronized abstract visual and vibrotactile stimuli additively stack in their influence on speech recognition performance. Our findings suggest that a multisensory integration process in speech perception requires salient temporal cues to enhance speech recognition ability in noisy environments.

Learning multisensory cue integration: A computational model of crossmodal synaptic plasticity enables reliability-based cue weighting by capturing stimulus statistics.

The brain forms unified, coherent, and accurate percepts of events occurring in the environment by integrating information from multiple senses through the process of multisensory integration. The neural mechanisms underlying this process, its development and its maturation in a multisensory environment are yet to be properly understood. Numerous psychophysical studies suggest that the multisensory cue integration process follows the principle of Bayesian estimation, where the contributions of individual sensory modalities are proportional to the relative reliabilities of the different sensory stimuli. In this article I hypothesize that experience dependent crossmodal synaptic plasticity may be a plausible mechanism underlying development of multisensory cue integration. I test this hypothesis via a computational model that implements Bayesian multisensory cue integration using reliability-based cue weighting. The model uses crossmodal synaptic plasticity to capture stimulus statistics within synaptic weights that are adapted to reflect the relative reliabilities of the participating stimuli. The model is embodied in a simulated robotic agent that learns to localize an audio-visual target by integrating spatial location cues extracted from of auditory and visual sensory modalities. Results of multiple randomized target localization trials in simulation indicate that the model is able to learn modality-specific synaptic weights proportional to the relative reliabilities of the auditory and visual stimuli. The proposed model with learned synaptic weights is also compared with a maximum-likelihood estimation model for cue integration via regression analysis. Results indicate that the proposed model reflects maximum-likelihood estimation.

Causal Inference of Body Ownership in the Posterior Parietal Cortex.

How do we come to sense that a hand in view belongs to our own body or not? Previous studies have suggested that the integration of vision and somatosensation in the frontoparietal areas plays a critical role in the sense of body ownership (i.e., the multisensory perception of limbs and body parts as our own). However, little is known about how these areas implement the multisensory integration process at the computational level and whether activity predicts illusion elicitation in individual participants on a trial-by-trial basis. To address these questions, we used functional magnetic resonance imaging and a rubber hand illusion-detection task and fitted the registered neural responses to a Bayesian causal inference model of body ownership. Thirty healthy human participants (male and female) performed 12 s trials with varying degrees of asynchronously delivered visual and tactile stimuli of a rubber hand (in view) and a (hidden) real hand. After the 12 s period, participants had to judge whether the rubber hand felt like their own. As hypothesized, activity in the premotor and posterior parietal cortices was related to illusion elicitation at the level of individual participants and trials. Importantly, activity in the posterior parietal cortex fit the predicted probability of illusion emergence of the Bayesian causal inference model based on each participant's behavioral response profile. Our findings suggest an important role for the posterior parietal cortex in implementing Bayesian causal inference of body ownership and reveal how trial-by-trial variations in neural signatures of multisensory integration relate to the elicitation of the rubber hand illusion.SIGNIFICANCE STATEMENT How does the brain create a coherent perceptual experience of one's own body based on information from the different senses? We examined how the likelihood of eliciting a classical bodily illusion that depends on vision and touch—the rubber hand illusion—is related to neural activity measured by functional magnetic resonance imaging. We found that trial-by-trial variations in the neural signal in the posterior parietal cortex, a well known center for sensory integration, fitted a statistical function that describes how likely it is that the brain infers that a rubber hand is one's own given the available visual and tactile evidence. Thus, probabilistic analysis of sensory information in the parietal lobe underlies our unitary sense of bodily self.

Weight illusion by presenting vibration to the fingertip

It is difficult for humans to perceive weight accurately, because the perception of weight is produced by the process of multisensory integration. This implies that, by manipulating certain factors, the weight of an object could be perceived differently from the actual weight. Here, the effects of vibration on weight perception were investigated using behavioral tests and questionnaires. As a behavioral test, from a number of identically appearing non-vibrating boxes of different weights, participants had to select a box that they perceived to be of the same weight as a vibrating box. They were also asked whether vibration affected the perceived weight of the box. Even though they reported that vibration created an illusion of weight, the results of the behavioral test did not show a statistically significant effect of vibration on perceived weight. Furthermore, we investigated how the frequency of vibration affected the illusion and found that the weight illusion requires smaller acceleration of vibration at lower frequencies, such as 30 Hz. The illusion was more intense at lower frequencies than at higher frequencies, such as 200 and 300 Hz. Thus, this study demonstrated that vibrotactile stimuli presented to the fingertips produce a weight illusion: vibrating objects are perceived to feel heavier. Even though the principles of this illusion are still unknown, the effect is concrete, and our approach allows easy implementation in virtual reality applications.

Tool-use Extends Peripersonal Space Boundaries in Schizophrenic Patients.

Background and HypothesisA primary disruption of the bodily self is considered a core feature of schizophrenia (SCZ). The “disembodied” self might be underpinned by inefficient body-related multisensory integration processes, normally occurring in the peripersonal space (PPS), a plastic sector of space surrounding the body whose extent is altered in SCZ. Although PPS is a malleable interface marking the perceptual border between self and others, no study has addressed the potential alteration of its plasticity in SCZ. We investigated the plasticity of PPS in SCZ patients after a motor training with a tool in the far space.Study DesignTwenty-seven SCZ patients and 32 healthy controls (HC) underwent an audio-tactile task to estimate PPS boundary before (Session 1) and after (Session 3) the tool-use. Parameters of PPS, including the size and the slope of the psychometric function describing audio-tactile RTs as a function of the audio-tactile distances, were estimated.Study ResultsResults confirm a narrow PPS extent in SCZ. Surprisingly, we found PPS expansion in both groups, thus showing for the first time a preserved PPS plasticity in SCZ. Patients experienced a weaker differentiation from others, as indicated by a shallower PPS slope at Session 1 that correlated positively with negative symptoms. However, at Session 3, patients marked their bodily boundary in a steeper way, suggesting a sharper demarcation of PPS boundaries after the action with the tool.ConclusionsThese findings highlight the importance of investigating the multisensory and motor roots of self-disorders, paving the way for future body-centred rehabilitation interventions that could improve patients’ altered body boundary.

The vision of dreams: from ontogeny to dream engineering in blindness.

Vitali H, Campus C, De Giorgis V, Signorini S, Gori M. The vision of dreams: from ontogeny to dream engineering in blindness. J Clin Sleep Med. 2022;18(8):2051-2062.