On the Role of Interoception in Body and Object Perception: A Multisensory-Integration Account

Both stimulus-specific and configurational features of multiple visual stimuli shape the spatial ventriloquism effect

Studies on multisensory perception often focus on simplistic conditions in which one single stimulus is presented per modality. Yet, in everyday life, we usually encounter multiple signals per modality. To understand how multiple signals within and across the senses are combined, we extended the classical audio-visual spatial ventriloquism paradigm to combine two visual stimuli with one sound. The individual visual stimuli presented in the same trial differed in their relative timing and spatial offsets to the sound, allowing us to contrast their individual and combined influence on sound localization judgements. We find that the ventriloquism bias is not dominated by a single visual stimulus but rather is shaped by the collective multisensory evidence. In particular, the contribution of an individual visual stimulus to the ventriloquism bias depends not only on its own relative spatio-temporal alignment to the sound but also the spatio-temporal alignment of the other visual stimulus. We propose that this pattern of multi-stimulus multisensory integration reflects the evolution of evidence for sensory causal relations during individual trials, calling for the need to extend established models of multisensory causal inference to more naturalistic conditions. Our data also suggest that this pattern of multisensory interactions extends to the ventriloquism aftereffect, a bias in sound localization observed in unisensory judgements following a multisensory stimulus.

A conceptual framework on body representations and their relevance for mental disorders

Many mental disorders are accompanied by distortions in the way the own body is perceived and represented (e.g., eating disorders, body dysmorphic disorder including muscle dysmorphia, or body integrity dysphoria). We are interested in the way these distortions develop and aim at better understanding their role in mental health across the lifespan. For this purpose, we first propose a conceptual framework of body representation that defines this construct and integrates different perspectives (e.g., cognitive neuroscience, clinical psychology) on body representations. The framework consists of a structural and a process model of body representation emphasizing different goals: the structural model aims to support researchers from different disciplines to structure results from studies and help collectively accumulate knowledge about body representations and their role in mental disorders. The process model is reflecting the dynamics during the information processing of body-related stimuli. It aims to serve as a motor for (experimental) study development on how distorted body representations emerge and might be changed. Second, we use this framework to review the normative development of body representations as well as the development of mental disorders that relate to body representations with the aim to further clarify the potential transdiagnostic role of body representations.

On the interplay between time and space perception in discontinuous stimulus displays

The present study examined whether and how the mutual perceptual biases of temporal and spatial information, known as the kappa and the tau effects, depend on the duration and spatial extent of sensory stimulation as well as on the magnitude of spatio-temporal discrepancy. Three small circles were presented in succession at different spatial positions. The time points of presentation and the spatial position of the second circle systematically varied. Participants judged either whether the temporal interval between the first and the second circle was longer than the interval between the second and the third circle (Experiment 1) or whether the spatial distance between the first and the second circle was larger than the distance between the second and the third circle (Experiment 2), or both in separate blocks of trials (Experiment 3). The impact of spatial information on temporal perception (i.e., the kappa effect) increased with velocity of motion presumably imputed by the participants to the static displays and decreased with spatio-temporal discrepancy. No inverse biases (i.e., no tau effects) were observed. These results are considered as an indication that integration of spatial and temporal signals follow the same basic principles as multisensory integration of redundant signals, such as those from vision and touch.

Sensory augmentation for a rapid motor task in a multisensory environment

BACKGROUND

Sensory substitution and augmentation systems (SSASy) seek to either replace or enhance existing sensory skills by providing a new route to access information about the world. Tests of such systems have largely been limited to untimed, unisensory tasks.

OBJECTIVE

To test the use of a SSASy for rapid, ballistic motor actions in a multisensory environment.

METHODS

Participants played a stripped-down version of air hockey in virtual reality with motion controls (Oculus Touch). They were trained to use a simple SASSy (novel audio cue) for the puck's location. They were tested on ability to strike an oncoming puck with the SASSy, degraded vision, or both.

RESULTS

Participants coordinated vision and the SSASy to strike the target with their hand more consistently than with the best single cue alone, t(13) = 9.16, p <.001, Cohen's d = 2.448.

CONCLUSIONS

People can adapt flexibly to using a SSASy in tasks that require tightly timed, precise, and rapid body movements. SSASys can augment and coordinate with existing sensorimotor skills rather than being limited to replacement use cases - in particular, there is potential scope for treating moderate vision loss. These findings point to the potential for augmenting human abilities, not only for static perceptual judgments, but in rapid and demanding perceptual-motor tasks.

Changes in body perception following virtual object manipulation are accompanied by changes of the internal reference scale

Changes in body perception often arise when observers are confronted with related yet discrepant multisensory signals. Some of these effects are interpreted as outcomes of sensory integration of various signals, whereas related biases are ascribed to learning-dependent recalibration of coding individual signals. The present study explored whether the same sensorimotor experience entails changes in body perception that are indicative of multisensory integration and those that indicate recalibration. Participants enclosed visual objects by a pair of visual cursors controlled by finger movements. Then either they judged their perceived finger posture (indicating multisensory integration) or they produced a certain finger posture (indicating recalibration). An experimental variation of the size of the visual object resulted in systematic and opposite biases of the perceived and produced finger distances. This pattern of results is consistent with the assumption that multisensory integration and recalibration had a common origin in the task we used.

Role of Immersive Virtual Reality in Motor Behaviour Decision-Making in Chronic Pain Patients

Primary chronic pain is a major contributor to disability worldwide, with an estimated prevalence of 20-33% of the world's population. The high socio-economic impact of musculoskeletal pain justifies seeking an appropriate therapeutic strategy. Immersive virtual reality (VR) has been proposed as a first-line intervention for chronic musculoskeletal pain. However, the growing literature has not been accompanied by substantial progress in understanding how VR exerts its impact on the pain experience and what neurophysiological mechanisms might be involved in the clinical effectiveness of virtual reality interventions in chronic pain patients. The aim of this review is: (i) to establish the state of the art on the effects of VR on patients with chronic pain; (ii) to identify neuroplastic changes associated with chronic pain that may be targeted by VR intervention; and (iii) to propose a hypothesis on how immersive virtual reality could modify motor behavioral decision-making through an interactive experience in patients with chronic pain.