Abnormal multisensory integration in relapsing-remitting multiple sclerosis.

Temporal Binding Window (TBW) represents a reliable index of efficient multisensory integration process, which allows individuals to infer which sensory inputs from different modalities pertain to the same event. TBW alterations have been reported in some neurological and neuropsychiatric disorders and seem to negatively affects cognition and behavior. So far, it is still unknown whether deficits of multisensory integration, as indexed by an abnormal TBW, are present even in Multiple Sclerosis. We addressed this issue by testing 25 participants affected by relapsing-remitting Multiple Sclerosis (RRMS) and 30 age-matched healthy controls. Participants completed a simultaneity judgment task (SJ2) to assess the audio-visual TBW; two unimodal SJ2 versions were used as control tasks. Individuals with RRMS showed an enlarged audio-visual TBW (width range = from - 166 ms to + 198 ms), as compared to healthy controls (width range = - 177/ + 66 ms), thus showing an increased tendency to integrate temporally asynchronous visual and auditory stimuli. Instead, simultaneity perception of unimodal (visual or auditory) events overall did not differ from that of controls. These results provide first evidence of a selective deficit of multisensory integration in individuals affected by RRMS, besides the well-known motor and cognitive impairments. The reduced multisensory temporal acuity is likely caused by a disruption of the neural interplay between different sensory systems caused by multiple sclerosis.

Somatosensory cortical representation of the body size.

The knowledge of the size of our own body parts is essential for accurately moving in space and efficiently interact with objects. A distorted perceptual representation of the body size often represents a core diagnostic criterion for some psychopathological conditions. The metric representation of the body was shown to depend on somatosensory afferences: local deafferentation indeed causes a perceptual distortion of the size of the anesthetized body part. A specular effect can be induced by altering the cortical map of body parts in the primary somatosensory cortex. Indeed, the present study demonstrates, in healthy adult participants, that repetitive Transcranial Magnetic Stimulation to the somatosensory cortical map of the hand in both hemispheres causes a perceptual distortion (i.e., an overestimation) of the size of the participants' own hand (Experiments 1-3), which does not involve other body parts (i.e., the foot, Experiment 2). Instead, the stimulation of the inferior parietal lobule of both hemispheres does not affect the perception of the own body size (Experiment 4). These results highlight the role of the primary somatosensory cortex in the building up and updating of the metric of body parts: somatosensory cortical activity not only shapes our somatosensation, it also affects how we perceive the dimension of our body.

Losing my hand. Body ownership attenuation after virtual lesion of the primary motor cortex.

A fundamental component of the self-awareness is the sensation that we are acting with our own body. Thus, a coherent sense of self implies the existence of a tight link between the sense of body ownership and the motor system. Here, we investigated this issue by taking advantage of a well-known experimental manipulation of body ownership, i.e., the rubber hand illusion (RHI), during which the subjects perceive a fake hand as part of their own body. To test the effect of the motor system down-regulation on the RHI susceptibility, we designed a sham-controlled study, where the primary motor cortex (M1) excitability was modulated by off-line low-frequency repetitive transcranial magnetic stimulation (rTMS). After rTMS (real or sham), subjects underwent the RHI either on the right hand, contralateral to the inhibited hemisphere (Experiment 1), or on the left hand, ipsilateral to the inhibited hemisphere (Experiment 2). Only in Experiment 1, the procedure strengthened the illusory experience, as proved by a significant increase, in rTMS compared to Sham, of both subjective (Embodiment/Disembodiment Questionnaires) and objective (Proprioceptive Drift) RHI measures. This evidence demonstrates that, when the M1 activity is down-regulated, the sense of body ownership is attenuated and the subjects become more prone to incorporate an alien body part. This, in turn, supports the existence of a mutual interaction between the sense of body ownership and the motor system, shedding new light on the construction of a coherent sense of self as an acting body.

Multisensory integration and motor resonance in the primary motor cortex.

Humans are endowed with a motor system that resonates to speech sounds, but whether concurrent visual information from lip movements can improve speech perception at a motor level through multisensory integration mechanisms remains unknown. Therefore, the aim of the study was to explore behavioral and neurophysiological correlates of multisensory influences on motor resonance in speech perception. Motor-evoked potentials (MEPs), by single pulse transcranial magnetic stimulation (TMS) applied over the left lip muscle (orbicularis oris) representation in the primary motor cortex, were recorded in healthy participants during the presentation of syllables in unimodal (visual or auditory) or multisensory (audio-visual) congruent or incongruent conditions. At the behavioral level, subjects showed better syllable identification in the congruent audio-visual condition as compared to the unimodal conditions, hence showing a multisensory enhancement effect. Accordingly, at the neurophysiological level, increased MEPs amplitudes were found in the congruent audio-visual condition, as compared to the unimodal ones. Incongruent audio-visual syllables resulting in illusory percepts did not increase corticospinal excitability, which in fact was comparable to that induced by the real perception of the same syllable. In conclusion, seeing and hearing congruent bilabial syllables increases the excitability of the lip representation in the primary motor cortex, hence documenting that multisensory integration can facilitate speech processing by influencing motor resonance. These findings highlight the modulation role of multisensory processing showing that it can boost speech perception and that multisensory interactions occur not only within higher-order regions, but also within primary motor areas, as shown by corticospinal excitability changes.

The sense of body ownership shapes the visual representation of body size.

The conscious body image includes the visual representation of body-parts size; whether this component of body perception can flexibly adapt to changes of the sense of ownership of one's body-parts remains to be demonstrated. The present study addresses this issue, showing that the ownership of a novel hand affects the conscious visual perception of the size of the really owned hand. Through a series of experiments in healthy adults, we assess how the embodiment of fake hands of different sizes (i.e., Rubber Hand Illusion, RHI) affects visual size estimation of the own hand. Our results demonstrate that the embodiment of a fake hand bigger in size than the own hand (Experiment 1), but not of a smaller fake hand (Experiment 2), affects the perception of similarity in size between the own hand and a visual model of the own hand, with a tendency toward an overestimation of the size of the hand exposed to the RHI (Experiment 1). The illusory ownership of a bigger hand does not affect the visual estimate of object size (Experiment 3). These findings show the tight link between the body image and the sense of ownership, the latter being able to change stored representations of body-parts size. This evidence might pave the way for restoring pathological alteration of body image through strategies accessing the body schema. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Mapping urban socioeconomic inequalities in developing countries through Facebook advertising data.

Ending poverty in all its forms everywhere is the number one Sustainable Development Goal of the UN 2030 Agenda. To monitor the progress toward such an ambitious target, reliable, up-to-date and fine-grained measurements of socioeconomic indicators are necessary. When it comes to socioeconomic development, novel digital traces can provide a complementary data source to overcome the limits of traditional data collection methods, which are often not regularly updated and lack adequate spatial resolution. In this study, we collect publicly available and anonymous advertising audience estimates from Facebook to predict socioeconomic conditions of urban residents, at a fine spatial granularity, in four large urban areas: Atlanta (USA), Bogotá (Colombia), Santiago (Chile), and Casablanca (Morocco). We find that behavioral attributes inferred from the Facebook marketing platform can accurately map the socioeconomic status of residential areas within cities, and that predictive performance is comparable in both high and low-resource settings. Our work provides additional evidence of the value of social advertising media data to measure human development and it also shows the limitations in generalizing the use of these data to make predictions across countries.

Perceptual Representation of Own Hand Size in Early Childhood and Adulthood.

Hand size perceptual distortions characterize adult human cognition. Notwithstanding the importance of uncovering how hand size representation develops in humans, studies in this field are still at a preliminary stage. Indeed, it is yet to be understood whether hand size distortions are present and reliable in early childhood and whether they differ from adults' distortions, offering a more in-depth insight into the emergence and development of such representations. We addressed this issue by comparing 4- to 6- year-old children and adults' representation of their own hand size, as assessed with a 2-forced choice visual perceptual task. To test participants' ability to estimate their own hand size, children and adults judged whether pictures of their own hand, resized to appear smaller or bigger than their own hand, matched or not its actual dimension. Results show that children aged 4 to 6 years tend to underestimate their own hand size, while adults underestimate their own hand more weakly. This evidence suggests that body-parts perceptual distortions are already in place in early childhood, and thus represent a characteristic of the human body representation.