In recent decades, new virtual reality (VR)-based protocols have been proposed for the rehabilitation of Unilateral Spatial Neglect (USN), a debilitating disorder of spatial awareness. However, it remains unclear which type of VR protocol and level of VR immersion can maximize the clinical benefits. To answer these questions, we conducted a systematic review of the use of VR for the rehabilitation of USN. Studies between 2000 and 2022 that met the inclusion criteria were classified according to their research design and degree of immersion (non-immersive, NIVR; semi-immersive, SIVR; immersive, IVR). A total of 375 studies were identified, of which 26 met the inclusion criteria. Improvements were found in 84.6% of the reviewed studies: 85.7% used NIVR, 100% used SIVR and 55.6% used IVR. However, only 42.3% of them included a control group and only 19.2% were randomized control trials (RCT). VR protocols may offer new opportunities for USN rehabilitation, although further RCTs are needed to validate their clinical efficacy.

In some patients with unilateral spatial neglect, symptoms reflect impaired lateralized spatial attention and representation (perceptual bias) whereas in others the inability to respond to stimuli located in contralesional space (response bias). Here, we investigated whether prismatic adaptation (PA) and visual scanning training (VST) differentially affect perceptual and response bias and whether rehabilitation outcome depends on the type of bias underlying symptoms. Two groups of neglect patients in the subacute phase were evaluated before, immediately after, and two weeks following 10 days of PA (n = 9) or VST (n = 9). Standard neuropsychological tests (i.e., Behavioural Inattentional Test, Diller cancellation test, and Line Bisection test) were administered to assess neglect symptoms, while the Landmark task was used to disentangle perceptual and response biases. Performance on the Landmark task revealed that PA was more effective in improving the perceptual bias, while VST mainly modulated the response bias. Neuropsychological tests performance suggested that VST is better suited to modulate neglect in patients with response bias, while PA may be effective in patients with both types of bias. These findings may offer novel insights into the efficacy of PA and VST in the rehabilitation of perceptual and response biases in patients with neglect.

Introduction: On Earth, self-produced somatosensory stimuli are typically perceived as less intense than externally generated stimuli of the same intensity, a phenomenon referred to as somatosensory attenuation (SA). Although this phenomenon arises from the integration of multisensory signals, the specific contribution of the vestibular system and the sense of gravity to somatosensory cognition underlying distinction between self-generated and externally generated sensations remains largely unknown. Here, we investigated whether temporary modulation of the gravitational input by head-down tilt bed rest (HDBR)–a well-known Earth-based analog of microgravity—might significantly affect somatosensory perception of self- and externally generated stimuli.Methods: In this study, 40 healthy participants were tested using short-term HDBR. Participants received a total of 40 non-painful self- and others generated electrical stimuli (20 self- and 20 other-generated stimuli) in an upright and HDBR position while blindfolded. After each stimulus, they were asked to rate the perceived intensity of the stimulation on a Likert scale.Results: Somatosensory stimulations were perceived as significantly less intense during HDBR compared to upright position, regardless of the agent administering the stimulus. In addition, the magnitude of SA in upright position was negatively correlated with the participants’ somatosensory threshold. Based on the direction of SA in the upright position, participants were divided in two subgroups. In the subgroup experiencing SA, the intensity rating of stimulations generated by others decreased significantly during HDBR, leading to the disappearance of the phenomenon of SA. In the second subgroup, on the other hand, reversed SA was not affected by HDBR.Conclusion: Modulation of the gravitational input by HDBR produced underestimation of somatosensory stimuli. Furthermore, in participants experiencing SA, the reduction of vestibular inputs by HDBR led to the disappearance of the SA phenomenon. These findings provide new insights into the role of the gravitational input in somatosensory perception and have important implications for astronauts who are exposed to weightlessness during space missions.

Action recognition is a fundamental aspect of human interaction. This process is mediated by the activation of shared sensorimotor representations during action execution and observation. Although complex movements involving balance or head and trunk rotations require vestibular signals for effective execution, their role in the recognition of others' actions is still unknown. To investigate the causal involvement of the vestibular system in the discrimination of actions performed by others and whether this is influenced by motor familiarity. In a single-blind design involving 25 healthy participants, Galvanic Vestibular Stimulation (GVS) was administered during an Action Discrimination Task (ADT), in which videos of actions categorized as vestibular/non-vestibular and familiar/unfamiliar were presented. Following each video, participants were required to identify the climax of the previously viewed action between two image options, using a two-alternative forced choice paradigm. The ADT was performed in active and sham GVS conditions, with left or right anodal montages. Response Times (RTs), Accuracy, and subjective motor familiarity were recorded for each action category. In sham GVS condition, an overall familiarity effect was observed, where RTs for familiar actions were faster than RTs for unfamiliar ones, regardless of vestibular engagement (p < .001; η_p² = .80). Conversely, under active GVS, a selective interference of the identification of vestibular familiar actions was observed compared to sham. Specifically, GVS prolonged RTs for recognizing familiar vestibular actions (p = .004, d = .59) while concurrently enhancing visual sensitivity (d’) for the same actions (p = .03, r = .21). These findings demonstrate the contribution of the vestibular system to action recognition. GVS disrupted the sensorimotor representation of vestibular actions and led to increased reliance on an alternative processing system focused on visual analysis of limb positions. This dissociation provides valuable insights for future investigations into the complex relationship between vestibular signals and cognitive processes involved in action identification, essential for developing innovative GVS interventions, particularly for individuals with sensorimotor or vestibular disorders.

Background: Emerging evidence indicates an association between vestibular dysfunction and Depersonalization/Derealization (DD) symptoms. However, substantial heterogeneity in the studied populations, experimental paradigms, and assessment methodologies limits clear conclusions regarding the involvement of the vestibular system in the onset of DD symptoms. Objective: To clarify the contribution of the vestibular system to DD symptoms in vestibular patients and healthy individuals undergoing vestibular stimulation. Methods: Following PRISMA guidelines, we reviewed studies examining: (1) DD symptoms in vestibular patients, and (2) DD symptoms in healthy individuals during vestibular stimulation. Results: Twenty-three studies met the inclusion criteria. Among these, 86.9% reported DD symptoms either in patients with vestibular disorders (14/15) or in healthy individuals during vestibular stimulations (6/8). Additionally, 82.61% of the studies identified an association between DD symptoms and anxiety or spatial disorientation. Conclusions: Together, these findings indicate that vestibular alterations may contribute to the emergence of DD symptoms. Anxiety and spatial disorientation were found to frequently co-occur suggesting an interaction between vestibular processing, affective regulation, and spatial cognition. This association can be interpreted within a neurofunctional framework, which posits that vestibular alterations disrupt multisensory integration in parietotemporal, insular, and hippocampal regions, contributing to the core phenomenology of DD.