Biology subjects

Serino, A.

Publications and source records attributed to Serino, A..

9 recordsLinked to original sources

bioRxiv2024

Multisensory integration in Peripersonal Space indexes consciousness states in sleep and disorders of consciousness

Conscious experience encompasses not only the awareness of external objects, but also a phenomenal representation of the embodied subject of the experience. The latter is mediated by the integration of multisensory stimuli between the body and the environment, a process mediated by the Peripersonal Space (PPS) system. Here we thus tested the hypothesis that a neural marker of PPS representation may index the presence of conscious experience. Using high-density EEG in awake participants, we identified a "PPS index", characterized by high-beta oscillations in centroparietal regions during the integration of audiotactile stimuli presented near versus far from the body. We then examined this marker across two models of altered consciousness, i.e., sleep and disorders of consciousness. The PPS index persisted during dreaming and waking conscious states but was absent during dreamless, unconscious states. Moreover, the same index predicted behavioural measures of consciousness and clinical outcome in patients recovering from disorders of consciousness. These results suggest that multisensory integration within the PPS is tightly linked to the presence of conscious experience.

neuroscience↗

bioRxiv2024

Proprioception Impacts Body Perception in Healthy Aging: Insights from a Psychophysical and Computational Approach

The experience of owning a body (body ownership, BO) and the perception of our body dimensions (metric body representation, mBR) depend on the integration of multisensory cues. As the human sensory system is subjected to a decline along the lifespan, encompassing all sensory modalities, we hypothesize that body perception may be different in older, as compared to young adults. Here, we investigate this hypothesis by comparing the multisensory processing underlying BO and mBR in healthy older (> 65 years) and young individuals. First, we applied rigorous computational and psychophysical methods to assess alterations in mBR and BO quantitatively. We then modeled the manifold relationship between the observed body misperceptions and the potential underlying sensory, motor, and cognitive factors. The results highlight significant differences between the two groups, with higher distortions in perceived arm dimensions and an increased tendency to experience BO towards a virtual hand in the aged group. These differences in both mBR and BO are explained by the reduced proprioceptive abilities of older adults, suggesting a crucial role of proprioception in driving age-dependent plasticity in body representations. Overall, our modeling and experimental approach provide new perspectives on altered body perception during aging, suggesting that they stem from the physiological proprioceptive decline occurring in older adults, and laying the groundwork to generate prevention and stimulation strategies to restore accurate body perception in aging.

neuroscience↗

bioRxiv2023

Human primary motor cortex indexes the onset of subjective intention in brain-machine-interface mediated actions

Self-initiated behavior is accompanied by the experience of willing our actions. Here, we leverage the unique opportunity to examine the full intentional chain - from will (W) to action (A) to environmental effects (E) - in a tetraplegic person fitted with a primary motor cortex (M1) brain machine interface (BMI) generating hand movements via neuromuscular electrical stimulation (NMES). This combined BMI-NMES approach allowed us to selectively manipulate each element of the intentional chain (W, A, and E) while performing extra-cellular recordings and probing subjective experience. Our results reveal single-cell, multi-unit, and population-level dynamics in human M1 that encode W and may predict its subjective onset. Further, we show that the proficiency of a neural decoder in M1 reflects the degree of W-A binding, tracking the participants subjective experience of intention in (near) real time. These results point to M1 as a critical node in forming the subjective experience of intention and demonstrate the relevance of intention-related signals for translational neuroprosthetics.

neuroscience↗

bioRxiv2021

Virtual reality-based sensorimotor adaptation shapes subsequent spontaneous and naturalistic stimulus-driven brain activity

Our everyday life summons numerous novel sensorimotor experiences, to which our brain needs to adapt in order to function properly. However, tracking plasticity of naturalistic behaviour and associated brain modulations is challenging. Here we tackled this question implementing a prism adaptation training in virtual reality (VRPA) in combination with functional neuroimaging. Three groups of healthy participants (N=45) underwent VRPA (with a spatial shift either to the left/right side, or with no shift), and performed fMRI sessions before and after training. To capture modulations in free-flowing, task-free brain activity, the fMRI sessions included resting state and free viewing of naturalistic videos. We found significant decreases in spontaneous functional connectivity between large-scale cortical networks - namely attentional and default mode/fronto-parietal networks - only for adaptation groups. Additionally, VRPA was found to bias visual representations of naturalistic videos, as following rightward adaptation, we found upregulation of visual response in an area in the parieto-occipital sulcus (POS) in the right hemisphere. Notably, the extent of POS upregulation correlated with the size of the VRPA induced after-effect measured in behavioural tests. This study demonstrates that a brief VRPA exposure is able to change large-scale cortical connectivity and correspondingly bias the representation of naturalistic sensory inputs. Significance statementIn the current work, we tested how a brief sensorimotor experience changes subsequent brain activity and connectivity. Using virtual reality (VR) as a tool for sensorimotor training opens a window for creating otherwise impossible sensory experiences and sensorimotor interactions. Specifically, we studied how VR adaptation training in ecological conditions modulates spontaneous functional connectivity and brain representation of naturalistic real-life-like stimuli. Previous adaptation studies used artificial, lab-designed setups both during adaptation and while measuring subsequent aftereffects. Testing brain response while observing naturalistic stimuli and in resting state allowed us to stay as close as possible to naturalistic real-life-like conditions, not confounded by performance during a task. The current work demonstrates how rapid changes in free-flowing brain activity and connectivity occur following short-term VR visuomotor adaptation training in healthy individuals. Moreover, we found a link between sensory responses to naturalistic stimuli and adaptation-induced behavioural aftereffect, thus demonstrating a common source of training-induced spatial recalibration, which affects both behaviour and brain representations of naturalistic stimuli. These findings might have meaningful implications both for understanding the mechanisms underlying visuomotor plasticity in healthy individuals and for using VR adaptation training as a tool for rehabilitating brain-damaged patients suffering from deficits in spatial representation.

neuroscience↗

bioRxiv2021

Acute stress affects peripersonal space representation

Peripersonal space (PPS) is the region of space surrounding the body. It has a dedicated multisensory-motor representation, whose purpose is to predict and plan interactions with the environment, and which can vary depending on environmental circumstances. Here, we investigated the effect on the PPS representation of an experimentally induced stress response. We assessed PPS representation in healthy humans, before and after a stressful manipulation, by quantifying visuotactile interactions as a function of the distance from the body, while monitoring salivary cortisol concentration. Participants, who showed a cortisol stress response, presented enhanced visuotactile integration for stimuli close to the body and reduced for far stimuli. Conversely, individuals, with a less pronounced cortisol response, showed a reduced difference in visuotactile integration between the near and the far space. In our interpretation, physiological stress resulted in a freezing-like response, where multisensory-motor resources are allocated only to the area immediately surrounding the body.

neuroscience↗

bioRxiv2020

Palm-to-finger cortical functional interactions in primary somatosensory cortex: a 7T fMRI study

Many studies focused on the cortical representations of fingers, while the palm is relatively neglected despite its importance for hand function. Here, we investigated palm representation (PR) and its interactions with finger representations (FRs) in primary somatosensory cortex (S1). Few studies in humans suggested that PR is located medially with respect to FRs in S1, yet to date, no study directly quantified the somatotopic organization of PR and the five FRs. Importantly, the relationship between the somatotopic organization and the cortical functional interactions between PR and FRs remains largely unexplored. Using 7T fMRI, we mapped PR and the five FRs at the single subject level. First, we analyzed the cortical distance between PR and FRs to determine their somatotopic organization. Results show that the PR was located medially with respect to D5. Second, we tested whether the observed cortical distances would predict palm-finger functional interactions. Using three complementary measures of functional interactions (co-activations, pattern similarity and resting-state connectivity), we show that palm-finger functional interactions were not determined by their somatotopic organization, that is, there was no gradient moving from D5 to D1, except for resting-state connectivity, which was predicted by the somatotopy. Instead, we show that the representational geometry of palm-finger functional interactions reflected the physical structure of the hand. Collectively, our findings suggest that the spatial proximity between topographically organized neuronal populations do not necessarily predicts their functional interactions, rather the structure of the sensory space (e.g. the hand shape) better predicts the observed functional interactions.

neuroscience↗

bioRxiv2019

Rapid Recalibration of Peri-Personal Space; Psychophysical, Electrophysiological, and Neural Network Modeling Evidence

Interactions between individuals and the environment are mediated by the body and occur within the peri-personal space (PPS) - the space surrounding the body. The multisensory encoding of this space plastically adapts to different bodily constraints and stimuli features. However, these remapping effects have only been demonstrated on the time-scale of days, hours, or minutes. Yet, if PPS mediates human-environment interactions in an adaptive manner, its representation should be altered by sensory history on trial-to-trial timescale. Here we test this idea first via a visuo-tactile reaction time paradigm in augmented reality where participants are asked to respond as fast as possible to touch, as visual object approach them. Results demonstrate that reaction times to touch are facilitated as a function of visual proximity, and the sigmoidal function describing this facilitation shifts closer to the body if the immediately precedent trial had indexed a smaller visuo-tactile disparity (i.e., positive serial dependency). Next, we derive the electroencephalographic correlates of PPS and demonstrate that this measure is equally shaped by recent sensory history. Finally, we demonstrate that a validated neural network model of PPS is able to account for the present results via a simple Hebbian plasticity rule. The present findings suggest that PPS encoding remaps on a very rapid time-scale and is sensitive to recent sensory history.

neuroscience↗

bioRxiv2018

Viewing one’s body during encoding boosts episodic memory

Episodic autobiographical memories (EAMs) are recollections of contextually rich and personally relevant past events. EAM has been linked to the sense of self, allowing one to mentally travel back in subjective time and re-experience past events. However, the sense of self has recently been linked to online multisensory processing and bodily self-consciousness (BSC). It is currently unknown whether EAM depends on BSC mechanisms. Here, we used a new immersive virtual reality (VR) system that maintained the perceptual richness of life episodes and fully controlled the experimental stimuli during encoding and retrieval, including the participants body. We report that the present VR setup permits to measure recognition memory for complex and embodied 3D scenes during encoding and retrieval, that recognition memory depends on delay and number of changed elements, and that viewing ones body as part of the virtual scene (as found in BSC studies) enhances delayed retrieval. This body effect was not observed when no virtual body or a moving control object was shown. These data show that embodied views improve recognition memory for 3D life-like scenes, thereby linking the sense of self, and BSC in particular, to episodic memory and the re-experiencing of specific past events in EAM.

neuroscience↗

bioRxiv2018

Audio-tactile and peripersonal space processing around the trunk in human parietal and temporal cortex: an intracranial EEG study

Interactions with the environment happen by the medium of the body within ones peripersonal space (PPS) - the space surrounding the body. Studies in monkey and humans have highlighted a multisensory distributed cortical network representing the PPS. However, electrophysiological evidence for a multisensory encoding of PPS in humans is lacking. Here, we recorded for the first time intracranial electroencephalography (iEEG) in humans while administering tactile stimulation (T) on the trunk, approaching auditory stimuli (A), and the combination of the two (AT). To map PPS, in AT trials, tactile stimulation was delivered when the sound was far, at an intermediate location, or close to the body. We first identified electrodes showing AT multisensory integration (i.e., AT vs. A+T): 19% of the recording electrodes. Among those electrodes, we identified those showing a PPS effect (30% of the AT electrodes), i.e., a modulation of the evoked response to AT stimulation as a function of the distance between the sound and body. For most sites, AT multisensory integration and PPS effects had similar spatiotemporal characteristics, with an early response (~50ms) in the insular cortex, and later responses (~200ms) in pre- and post-central gyri. Superior temporal cortex showed a different response pattern with AT multisensory integration at ~100ms without PPS effect. These results, representing the first iEEG delineation of PPS processing in humans, show that PPS processing happens at neural sites where also multisensory integration occurs and at similar time periods, suggesting that PPS representation (around the trunk) is based on a spatial modulation of multisensory integration.

neuroscience↗