Vestibular Stimulation Research Articles

Finding Balance with Vestibular Stimulation

Weakening of the vestibular system through disease or aging leads to imbalance, restricted mobility, and falls (Hain et al., 2018). Vestibular weakness affects one-third of people over the age of 40, and 85% of those over 80 years (Agrawal et al., 2009). The delicate cells of the vestibular system do not regenerate and thus it becomes an incurable chronic condition. A promising treatment is noisy galvanic vestibular stimulation (nGVS), a non-invasive electrical stimulation, delivered to the vestibular system, aiming to restore absent vestibular information and improve balance (McLaren et al., 2022). This presentation reports the results of a scoping review investigating the stimulation parameters that can be manipulated to improve the efficacy of nGVS. A comprehensive systematic search of five databases up to December 2022 identified studies applying nGVS to people with the aim of improving their postural control. Two independent reviewers screened and identified eligible studies and extracted parameter data. Thirty-one studies met the eligibility criteria. The review identified that a broad array of settings have been employed across studies. The nGVS parameters of waveform, amplitude, frequency band, duration of stimulation, method of amplitude optimization, size and composition of electrodes and the electrode skin interface are all likely to influence the efficacy of nGVS. However, the ability to draw robust conclusions about the selection of optimal nGVS parameters is hindered by a lack of studies that directly compare parameter settings. I propose a guideline for the accurate reporting of nGVS parameters. This will help establish standardized stimulation protocols bringing us one step closer to becoming a readily available clinical treatment.

Optimal Design of Galvanic Vestibular Stimulation for Patients with Vestibulopathy and Cerebellar Disorders.

Galvanic vestibular stimulation (GVS) has shown positive outcomes in various neurological and psychiatric disorders, such as enhancing postural balance and cognitive functions. In order to expedite the practical application of GVS in clinical settings, our objective was to determine the best GVS parameters for patients with vestibulopathy and cerebellar disorders using optimal design calculation. A total of 31 patients (26 males, mean age 57.03 ± 14.75 years, age range 22-82 years) with either unilateral or bilateral vestibulopathy (n = 18) or cerebellar ataxia (n = 13) were enrolled in the study. The GVS intervention included three parameters, waveform (sinusoidal, direct current [DC], and noisy), amplitude (0.4, 0.8, and 1.2 mA), and duration of stimulation (5 and 30 min), resulting in a total of 18 GVS intervention modes as input variables. To evaluate the effectiveness of GVS, clinical vertigo and gait assessments were conducted using the Dizziness Visual Analogue Scale (D-VAS), Activities-specific Balance Confidence Scale (ABC), and Scale for Assessment and Rating of Ataxia (SARA) as output variables. Optimal design and local sensitivity analysis were employed to determine the most optimal GVS modes. Patients with unilateral vestibulopathy experienced the most favorable results with either noisy or sinusoidal GVS at 0.4 mA amplitude for 30 min, followed by DC GVS at 0.8 mA amplitude for 5 min. Noisy GVS at 0.8 or 0.4 mA amplitude for 30 min demonstrated the most beneficial effects in patients with bilateral vestibulopathy. For patients with cerebellar ataxia, the optimal choices were noisy GVS with 0.8 or 0.4 mA amplitude for 5 or 30 min. This study is the first to utilize design optimization methods to identify the GVS stimulation parameters that are tailored to individual-specific characteristics of dizziness and imbalance. A sensitivity analysis was carried out along with the optimal design to offset the constraints of a limited sample size, resulting in the identification of the most efficient GVS modes for patients suffering from vestibular and cerebellar disorders.

Combining Vestibular Rehabilitation and Noisy Galvanic Vestibular Stimulation for Treatment of Unilateral Vestibulopathy: A Randomized Controlled Trial

Background and Aim: Vestibular Rehabilitation (VR) is a well-accepted treatment for Unilateral Vestibulopathy (UVP). Since noisy Galvanic Vestibular Stimulation (nGVS) improves the processing of vestibular inputs, we assessed the synergistic effects of adding nGVS to vestibular rehabilitation for the treatment of UVP. Methods: Patients with UVP were randomly assigned into two groups receiving either VR for four weeks (VR group, n=12) or VR for four weeks combined with nGVS for three sessions (VR+nGVS group; n=12). Outcome measurements were postural control parameters measured with eyes open/closed conditions on hard/soft surfaces, Vestibulo-Ocular Reflex (VOR) gain, and Dizziness Handicap Inventory (DHI) scores that were assessed at baseline and after four weeks. Results: All postural control parameters, mean total and subscale scores of DHI, and mean VOR gain in directions of affected canals significantly improved in both groups after interventions (p<0.05) except mean mediolateral displacement in conditions with eyes closed on hard surface and with eyes open on soft surface, mean mediolateral velocity in conditions with eyes closed on hard surface, ability to stance with eye closed condition on soft surface and mean emotional subscale of DHI in VR group. Improvements were significantly higher in postural control outcomes measured in stances with eyes closed on hard surface and with eyes open and closed on soft surface, mean VOR gains in directions of affected horizontal and anterior canals, and mean total, physical, and functional scores of DHI in VR+nGVS group (p<0.05). Conclusion: When combined with VR, nGVS shows additional therapeutic effects in UVP patients. Keywords: Unilateral peripheral vestibulopathy; vestibular compensation; galvanic vestibular stimulation; vestibular rehabilitation; postural control

Vestibular contribution to spatial encoding.

Determining the spatial relation between objects and our location in the surroundings is essential for survival. Vestibular inputs provide key information about the position and movement of our head in the three-dimensional space, contributing to spatial navigation. Yet, their role in encoding spatial localisation of environmental targets remains to be fully understood. We probed the accuracy and precision of healthy participants' representations of environmental space by measuring their ability to encode the spatial location of visual targets (Experiment 1). Participants were asked to detect a visual light and then walk towards it. Vestibular signalling was artificially disrupted using stochastic galvanic vestibular stimulation (sGVS) applied selectively during encoding targets' location. sGVS impaired the accuracy and precision of locating the environmental visual targets. Importantly, this effect was specific to the visual modality. The location of acoustic targets was not influenced by vestibular alterations (Experiment 2). Our findings indicate that the vestibular system plays a role in localising visual targets in the surrounding environment, suggesting a crucial functional interaction between vestibular and visual signals for the encoding of the spatial relationship between our body position and the surrounding objects.

How a Subclinical Unilateral Vestibular Signal Improves Binocular Vision.

The present study aimed to determine if an infra-liminal asymmetric vestibular signal could account for some of the visual complaints commonly encountered in chronic vestibular patients. We used infra-liminal galvanic vestibular stimulation (GVS) to investigate its potential effects on visuo-oculomotor behavior. A total of 78 healthy volunteers, 34 aged from 20 to 25 years old and 44 aged from 40 to 60 years old, were included in a crossover study to assess the impact of infra-liminal stimulation on convergence, divergence, proximal convergence point, and stereopsis. Under GVS stimulation, a repeated measures ANOVA showed a significant variation in near convergence (p < 0.001), far convergence (p < 0.001), and far divergence (p = 0.052). We also observed an unexpected effect of instantaneous blocking of the retest effect on the far divergence measurement. Further investigations are necessary to establish causal relationships, but GVS could be considered a behavioral modulator in non-pharmacological vestibular therapies.

Post-activation depression of the Hoffman reflex is not altered by galvanic vestibular stimulation in healthy subjects.

The comprehension of the neural elements interacting in the spinal cord affected by vestibular input will contribute to the understanding of movement execution in normal and pathological conditions. In this context, Hoffman's reflex (H-reflex) has been used to evaluate transient excitability changes on the spinal cord descending pathways. The post-activation depression (P-AD) of the H-reflex consists of evoking consecutive responses (>1 Hz) provoking an amplitude depression, which has been shown to diminish in pathological conditions (i.e., spasticity, diabetic neuropathy). Galvanic Vestibular Stimulation (GVS) is a non-invasive method that activates the vestibular afferents and has been used to study the excitability of the H-reflex applied as a conditioning pulse. To our knowledge, there are no reports evaluating the P-AD during and after GVS. Our primary aim was to determine if GVS alters the P-AD evoked by stimulating the tibial nerve at 0.1, 1, 5, and 10 Hz, recording in the gastrocnemius and soleus muscles. Direct current stimulation of 2.0 ± 0.6 mA with the cathode ipsilateral (Ipsi) or contralateral (Contra) to the H-reflex electrode montage was applied bilaterally over the mastoid process in 19 healthy subjects. The P-AD's immediate post-GVS response (P Ipsi, P Contra) was also analyzed. Secondarily, we analyzed the excitability of the H-reflex during GVS. Responses evoked at 0.1 Hz with GVS, post-GVS, and a Control (no GVS) condition were used for comparisons. Our results show that P-AD persisted in all subjects despite increased excitability induced by GVS: statistical significance was found when comparing P-AD at 1, 5, and 10 Hz with the corresponding condition (Control, Ipsi, P Ipsi, Contra, P Contra) at 0.1 Hz (p < 0.001). Additionally, the increase in excitability produced by GVS was quantified for the first H-reflex of each P-AD stimulation frequency. The percentage change for all GVS conditions surpassed the Control by at least 20%, being statistically significant for Contra compared to Control (p < 0.01). In summary, although GVS increases the excitability of the vestibulospinal pathway at a premotor level, the neural inhibitory mechanism present in P-AD remains unaltered in healthy subjects.

Prosthetic Stimulation of the Vestibular Nerve Can Evoke Robust Eye and Head Movements Despite Prior Labyrinthectomy.

Prosthetic electrical stimulation can evoke compensatory eye and head movement despite vestibular implant electrode insertion occurring years after prior labyrinthectomy. Vestibular implants sense head rotation and directly stimulate the vestibular nerve, bypassing damaged end organs. Animal research and current clinical trials have demonstrated the efficacy of this approach. However, candidacy criteria for vestibular implants currently require presence of a patent labyrinth in the candidate ear and at least aidable hearing in the opposite ear, thus excluding patients who have undergone prior labyrinthectomy for unilateral Menière's disease that later progressed to bilateral vestibular hypofunction. Eight years after right unilateral labyrinthectomy, we implanted stimulating electrodes in the previously exenterated right ear ampullae of a rhesus macaque monkey. The left labyrinth had long-standing hypofunction due to intratympanic gentamicin injection and surgical disruption. We used three-dimensional video-oculography to measure eye movement responses to prosthetic electrical stimulation. We also measured head-movement responses to prosthetic stimulation with the head unrestrained. Bilateral vestibular hypofunction was confirmed by absence of vestibuloocular reflex responses to whole-body rotation without prosthetic stimulation. For a subset of the implanted electrodes, prosthetic vestibular stimulation evoked robust compensatory eye and head movements. One electrode reliably elicited responses aligned with the implanted ear's anterior canal nerve regardless of the return electrode used. Similarly, a second electrode also elicited responses consistent with excitation of the horizontal canal nerve. Responses grew quasilinearly with stimulation rate and current amplitude. Prosthetic electrical stimulation targeting the vestibular nerve can be effective years after labyrinthectomy, if at least some parts of the vestibular nerve's ampullary branches remain despite destruction or removal of the membranous labyrinth.

Head Orientation Modulates Vestibular Cerebellar Evoked Potentials (VsCEPs) and Reflexes Produced by Impulsive Mastoid and Midline Skull Stimulation

The cerebellum plays a critical role in the modulation of vestibular reflexes, dependent on input from proprioceptive afferents. The mechanism of this cerebellar control is not well understood. In a sample of 11 healthy human subjects, we investigated the effects of head orientation on ocular, cervical, postural and cerebellar short latency potentials evoked by impulsive stimuli applied at both mastoids and midline skull sites. Subjects were instructed to lean backwards with the head positioned straight ahead or held rotated in different degrees of yaw towards the right and left sides. Impulsive mastoid stimulation, a potent method of utricular stimulation, produced localised vestibular cerebellar evoked potentials (VsCEPs: P12-N17) which were strongly modulated by head orientation. The response was larger on the side opposite to the direction of head rotation and with stimulation on the side of rotation. In contrast, ocular VEMPs (oVEMPs: n10-p16) were present but showed little change with head posture, while cervical VEMPs (cVEMPs: p15-n23) were larger with the head held rotated away from the side of the recording. Postural effects with lateral vestibular stimulation were strongly modulated by head rotation, with more powerful effects occurring bilaterally with stimulation on the side of rotation. The duration of the postural EMG changes was similar to the post-excitation inhibition of the electrocerebellogram (ECeG), consistent with cerebellar participation. We conclude that head rotation selectively affects evoked vestibular reflexes towards different targets, consistent with their physiological roles. Changes in VsCEPs may contribute to the modulation of postural reflexes by the cerebellum.

Modulation of sleep using noninvasive stimulations during sleep.

Among the various sleep modulation methods for improving sleep, three methods using noninvasive stimulation during sleep have been reviewed and summarized. The first method involves noninvasive direct brain stimulation to induce a current directly in the brain cortex. Electrically or magnetically applied stimulations trigger electrical events such as slow oscillations or sleep spindles, which can also be recorded by an electroencephalogram. The second method involves sensory stimulation during sleep, which provides stimulation through the sensory pathway to invoke equivalent brain activity like direct brain stimulation. Olfactory, vestibular, and auditory stimulation methods have been used, resulting in several sleep-modulating effects, which are characteristic and depend on the experimental paradigm. The third method is to modulate sleep by shifting the autonomic balance affecting sleep homeostasis. To strengthen parasympathetic dominance, stimulation was applied to decrease heart rate by synchronizing the heart rhythm. These noninvasive stimulation methods can strengthen slow-wave sleep, consolidate declarative or procedural memory, and modify sleep macrostructure. These stimulation methods provide evidence and possibility for sleep modulation in our daily life as an alternative method for the treatment of disturbed sleep and enhancing sleep quality and performance beyond the average level.

Quantification of Visual Feature Selectivity of the Optokinetic Reflex in Mice

The optokinetic reflex (OKR) is an essential innate eye movement that is triggered by the global motion of the visual environment and serves to stabilize retinal images. Due to its importance and robustness, the OKR has been used to study visual-motor learning and to evaluate the visual functions of mice with different genetic backgrounds, ages, and drug treatments. Here, we introduce a procedure for evaluating OKR responses of head-fixed mice with high accuracy. Head fixation can rule out the contribution of vestibular stimulation on eye movements, making it possible to measure eye movements triggered only by visual motion. The OKR is elicited by a virtual drum system, in which a vertical grating presented on three computer monitors drifts horizontally in an oscillatory manner or unidirectionally at a constant velocity. With this virtual reality system, we can systematically change visual parameters like spatial frequency, temporal/oscillation frequency, contrast, luminance, and the direction of gratings, and quantify tuning curves of visual feature selectivity. High-speed infrared video-oculography ensures accurate measurement of the trajectory of eye movements. The eyes of individual mice are calibrated to provide opportunities to compare the OKRs between animals of different ages, genders, and genetic backgrounds. The quantitative power of this technique allows it to detect changes in the OKR when this behavior plastically adapts due to aging, sensory experience, or motor learning; thus, it makes this technique a valuable addition to the repertoire of tools used to investigate the plasticity of ocular behaviors.

Training augmentation using additive sensory noise in a lunar rover navigation task.

The uncertain environments of future space missions means that astronauts will need to acquire new skills rapidly; thus, a non-invasive method to enhance learning of complex tasks is desirable. Stochastic resonance (SR) is a phenomenon where adding noise improves the throughput of a weak signal. SR has been shown to improve perception and cognitive performance in certain individuals. However, the learning of operational tasks and behavioral health effects of repeated noise exposure aimed to elicit SR are unknown. We evaluated the long-term impacts and acceptability of repeated auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS) on operational learning and behavioral health. Subjects (n = 24) participated in a time longitudinal experiment to access learning and behavioral health. Subjects were assigned to one of our four treatments: sham, AWN (55 dB SPL), nGVS (0.5 mA), and their combination to create a multi-modal SR (MMSR) condition. To assess the effects of additive noise on learning, these treatments were administered continuously during a lunar rover simulation in virtual reality. To assess behavioral health, subjects completed daily, subjective questionnaires related to their mood, sleep, stress, and their perceived acceptance of noise stimulation. We found that subjects learned the lunar rover task over time, as shown by significantly lower power required for the rover to complete traverses (p < 0.005) and increased object identification accuracy in the environment (p = 0.05), but this was not influenced by additive SR noise (p = 0.58). We found no influence of noise on mood or stress following stimulation (p > 0.09). We found marginally significant longitudinal effects of noise on behavioral health (p = 0.06) as measured by strain and sleep. We found slight differences in stimulation acceptability between treatment groups, and notably nGVS was found to be more distracting than sham (p = 0.006). Our results suggest that repeatedly administering sensory noise does not improve long-term operational learning performance or affect behavioral health. We also find that repetitive noise administration is acceptable in this context. While additive noise does not improve performance in this paradigm, if it were used for other contexts, it appears acceptable without negative longitudinal effects.

Comparison of vestibular input statistics during natural activities and while piloting an aircraft.

The present study investigates the statistics and spectral content of natural vestibular stimuli experienced by healthy human subjects during three unconstrained activities. More specifically, we assessed how the characteristics of vestibular inputs are altered during the operation of a complex human-machine interface (a flight in a helicopter simulator) compared with more ecological tasks, namely a walk in an office space and a seated visual exploration task. As previously reported, we found that the power spectra of vestibular stimuli experienced during self-navigation could be modeled by two power laws but noted a potential effect of task intensity on the transition frequency between the two fits. In contrast, both tasks that required a seated position had power spectra that were better described by an inverted U shape in all planes of motion. Taken together, our results suggest that 1) walking elicits stereotyped vestibular inputs whose power spectra can be modeled by two power laws that intersect at a task intensity-dependent frequency; 2) body posture induces changes in the frequency content of vestibular information; 3) pilots tend to operate their aircraft in a way that does not generate highly nonecological vestibular stimuli; and 4) nevertheless, human-machine interfaces used as a means of manual navigation still impose some unnatural, contextual constraints on their operators.NEW & NOTEWORTHY Building upon previously published research, this study assesses and compares the vestibular stimuli experienced by healthy subjects in natural tasks and during the interaction with a complex machine: a helicopter simulator. Our results suggest the existence of an anatomical filter, meaning that body posture shapes vestibular spectral content. Our findings further indicate that operators control their machine within a constrained operating range such that they experience vestibular stimulations that are as ecological as possible.

Combination of Vestibular Rehabilitation and Galvanic VestibularStimulation ImprovesVerbal andVisuospatial Memory: A Randomized Control Trial in Patients with Amnestic Mild Cognitive Impairment

Background and Aim: Considering the critical input of the vestibular system to the hippocampus as an area involved in cognition, and vestibular disorders reported in patients with amnestic Mild Cognitive Impairment (aMCI), we aimed to investigate the effects of Vestibular Rehabilitation (VR) with and without noisy Galvanic Vestibular Stimulation (nGVS) on cognitive function in patients with aMCI. Methods: In a randomized controlled trial, twenty-two patients with aMCI were randomly assigned to two groups receiving: 1) VR for four weeks (VR group); 2) VR for four weeks with nGVS for three sessions (GVS+VR group). Outcome measures were Rey's Auditory-Verbal Learning Test (RAVLT), Corsi blocks, Visual Search (VS), and match to sample tests. Results: Mean immediate and delayed recalls of RAVLT, all of the outcomes of Corsi blocks and VS tests, and the error rate of the match to sample tests improved significantly after intervention in VR and GVS+VR groups. Between-group differences were observed for learning and delayed recalls of RAVLT (p=0.001, d=0.444 and p&lt;0.001, d=0.512 respectively), reaction times 1 and 2 in VS (p=0.007, d=0.325 and p=0.001, d=0.446 respectively), the total correct trial of Corsi blocks (p=0.026, d=0.235), and error rate of the match to sample (p=0.017, d=0.266) tests. Conclusion: The synergistic effect of VR and GVS suggested that simultaneous use of both stimulations improves verbal and visuospatial memory in aMCI patients. Study protocol location: https://irct.ir/trial/47249 Trial registration number: IRCT20160131026279N3 Keywords: Mild cognitive impairment; spatial memory; verbal memory; hippocampus; galvanic vestibular stimulation; vestibular rehabilitation

Effects of a short period of postural training on postural stability and vestibulospinal reflexes.

The effects of postural training on postural stability and vestibulospinal reflexes (VSRs) were investigated in normal subjects. A period (23 minutes) of repeated episodes (n = 10, 50 seconds) of unipedal stance elicited a progressive reduction of the area covered by centre of pressure (CoP) displacement, of average CoP displacement along the X and Y axes and of CoP velocity observed in this challenging postural task. All these changes were correlated to each other with the only exception of those in X and Y CoP displacement. Moreover, they were larger in the subjects showing higher initial instability in unipedal stance, suggesting that they were triggered by the modulation of sensory afferents signalling body sway. No changes in bipedal stance occurred soon and 1 hour after this period of postural training, while a reduction of CoP displacement was apparent after 24 hours, possibly due to a beneficial effect of overnight sleep on postural learning. The same period of postural training also reduced the CoP displacement elicited by electrical vestibular stimulation (EVS) along the X axis up to 24 hours following the training end. No significant changes in postural parameters of bipedal stance and VSRs could be observed in control experiments where subjects were tested at identical time points without performing the postural training. Therefore, postural training led to a stricter control of CoP displacement, possibly acting through the cerebellum by enhancing feedforward mechanisms of postural stability and by depressing the VSR, the most important reflex mechanism involved in balance maintenance under challenging conditions.

Effects of noisy galvanic vestibular stimulation on functional reach test

Balance disorders are a risk factor for falls in older individuals, and an increased center of pressure (COP) sway path length during standing and decreased reach distance in the functional reach test (FRT) predispose them to falls. Reportedly, noisy galvanic vestibular stimulation (nGVS) reduces COP sway path length during standing in young and community-dwelling older individuals and suggested to be a promising approach to improve balance function. However, the effect of nGVS on FRT remains unclear. Therefore, this study aimed to clarify the effect of nGVS on the FRT reach distance. This study has a cross-over design and included 20 healthy young adults. Interventions under nGVS (stimulation intensity: 0.2 mA) and sham (stimulation intensity: 0 mA) conditions were randomly administered to each participant. The participants underwent COP sway during standing measurements and FRT pre-intervention and post-intervention under each condition, and COP sway path length and the FRT reach distance were calculated. Statistical analysis revealed a significant decrease in post-intervention COP sway path length compared with pre-intervention COP sway path length under the nGVS condition. Conversely, the FRT reach distance remained the same under both nGVS and sham conditions. Thus, nGVS may improve the standing balance function but cannot change the FRT reach distance in healthy young individuals.

High-current galvanic vestibular stimulation impairs working memory span, but not other executive functions

Patients with peripheral vestibular dysfunction (PVD) suffer not only from physical problems such as imbalance or vertigo but also from neuropsychological difficulties, including executive deficits. However, it is unclear whether the PVD directly causes executive problems. To examine the causal vestibular influence on executive functions, we induced either high-current (2 mA), low-current (0.8 mA), or sham current (0 mA) galvanic vestibular stimulation (GVS) in 79 healthy participants. Participants solved three tasks, measuring the core executive components (working memory, inhibition, cognitive flexibility) before and during GVS. High-current GVS impaired working memory span, but not inhibition and cognitive flexibility performance. Low-current GVS did not influence executive performance. Results indicate a causal vestibular influence on working memory span. Joint cortical areas of vestibular and working memory processing are discussed. Since high-current GVS in healthy participants serves as a model for an artificial vestibular dysfunction, our results could improve the diagnostics and therapy of patients with PVD.

Effects of additive sensory noise on cognition.

Adding noise to a system to improve a weak signal's throughput is known as stochastic resonance (SR). SR has been shown to improve sensory perception. Some limited research shows noise can also improve higher order processing, such as working memory, but it is unknown whether SR can broadly improve cognition. We investigated cognitive performance while applying auditory white noise (AWN) and/or noisy galvanic vestibular stimulation (nGVS). We measured cognitive performance (n = 13 subjects) while completing seven tasks in the cognition test battery (CTB). Cognition was assessed with and without the influence of AWN, nGVS, and both simultaneously. Performance in speed, accuracy, and efficiency was observed. A subjective questionnaire regarding preference for working in noisy environments was collected. We did not find broad cognitive performance improvement under the influence of noise (p > 0.1). However, a significant interaction was found between subject and noise condition for accuracy (p = 0.023), indicating that some subjects exhibited cognitive changes with the addition of noise. Across all metrics, noisy environment preference may trend to be a potential indicator of whether subjects will exhibit SR cognitive benefits with a significant predictor in efficiency (p = 0.048). This study investigated using additive sensory noise to induce SR in overall cognition. Our results suggest that using noise to improve cognition is not applicable for a broad population; however, the effect of noise differs across individuals. Further, subjective questionnaires may be a means to identify which individuals are sensitive to SR cognitive benefits, but further investigation is needed.

0394 Effect of electrical vestibular nerve stimulation on sleep quality in young adults with insomnia: a randomized controlled trial

Abstract Introduction Insomnia is a common sleep disorder among all age groups which adversely affects physical and mental health. Young adults are considered a high-risk population group due to increased use of electronic media at bedtime, stress associated with balancing educational demands and unhealthy sleep practices. Previous research suggests that electrical vestibular nerve stimulation (VeNS) may improve sleep outcomes by influencing the hypothalamus and brainstem nuclei involved in regulating the circadian rhythm and wakefulness. The present study is a randomised, double blinded, sham-controlled trial with the aim of assessing the efficacy of VeNS on the sleep quality of young adults suffering from insomnia. Methods Eighty adults aged 18-24 years who scored 15 or higher on the Insomnia Severity Index (ISI) were recruited. Participants assigned to the intervention group (n=40) received 30 minutes per day of VeNS with 5 sessions per week for 4 weeks, while the control group (n=40) received sham stimulation for the same period. ISI scores were recorded at baseline and repeated weekly. The primary outcome was between-group change in ISI from baseline to day 28. Secondary outcomes included between-group change in the emotional states of depression, anxiety and stress measured by the DASS-21 questionnaire, and quality of life (QoL) measured by the WHOQoL-BREF. Results A group-by-time interaction effect on change in ISI score from day 0 to day 28 (F3, 248 = 295.56; P&amp;lt; 0.001) was observed. The intervention group had a higher reduction in mean ISI score relative to the control group at day 28 (mean change [95% CI]: 7.23 [6.78, 7.67] vs. 0.98 [0.89, 1.06], P&amp;lt; 0.001; respectively). Furthermore, the intervention group showed improvements in depression, anxiety, and stress scores (P&amp;lt; 0.001) and QoL outcomes (P&amp;lt; 0.001) compared with the control group. Conclusion Regular VeNS usage over 4 weeks lead to a clinically meaningful decrease in ISI scores and improved general well-being in young adults with insomnia. VeNS may have potential as a drug-free and non-invasive therapy to improve sleep outcomes. Support (if any)

0396 Efficacy of electrical vestibular nerve stimulation for the management of insomnia: a randomized controlled trial

Abstract Introduction Insomnia is one of the most prevalent health concerns in the general population. Cognitive behavioural therapy (CBT) and pharmacological interventions are recommended for the treatment of insomnia. However, CBT can be expensive and difficult to access, while the use of pharmacotherapy can be limited by reports of adverse events. Due to these limitations, there is a strong need for alternative measures to manage insomnia. Preliminary research indicates the potential that electrical vestibular nerve stimulation (VeNS) has as a non-invasive method for managing insomnia. The aim of this study is to evaluate the efficacy of VeNS as a method of managing sleep quantity and quality in individuals with insomnia, as compared to a sham control. Methods The study was a two-armed, double-blind randomized controlled trial that was conducted across two research sites in the United Kingdom (UK) and Hong Kong (HK). Participants aged over 18 years with an Insomnia Severity Index (ISI) score of 15 or higher were randomly assigned to intervention and control groups. The intervention group was instructed to use the VeNS device at home for 30 minutes daily for 4 weeks, while the control group was instructed to use the sham device for the same period. ISI values were captured at baseline, at 2 weeks and at 4 weeks. Sleep quality and quality of life (QoL) were assessed at baseline and at 4 weeks using the Pittsburgh Sleep Quality Index (PSQI) and the 36-item Short Form Health Survey (SF-36), respectively. Results A total of 146 participants were recruited from the HK (n=94) and UK (n=52) research sites. The study has recently been completed with the statistical analysis ongoing. The between-group change in ISI values (primary outcome), sleep quality and QoL from baseline to week 4 will be examined. Conclusion The results of this study will help determine whether the relatively inexpensive, and non-invasive technique of VeNS is effective in the management of insomnia. The data collected will be used to support regulatory submissions, primarily to the US Food and Drug Administration. Support (if any)

Effect of Multisensory Stimulation on the Physical Growth of Premature Infants

Introduction: Height and head circumference is one of the criteria for physical health of preterm infants and indicates their neuromuscular development. The aim of this study was to investigate the effect of multisensory stimulation on height and head circumference of preterm infants.&#x0D; Methods: The present study was a clinical trial study; which was performed on premature infants admitted to the neonatal intensive care unit at Shahid Motahari Hospital in Jahrom City, Iran, in 2016. Initially, 80 infants with a gestational age of 32 to 36 weeks were randomly divided into two groups of multisensory stimulation and control. The intervention method in this study was that the intervention group had a multisensory stimulation program (auditory stimulation, tactile stimulation, visual stimulation and vestibular stimulation) by mothers for 12 minutes per day and 5 times a week until discharge and in the control group they only received the usual care ward. The height and head circumference were measured by the researcher with a meter until the day the infant was discharged from the ward. Data were analyzed using SPSS software version 16.&#x0D; Results: There was no significant difference between the two groups of preterm infants in terms of fetal age, birth weight and sex. Based on the comparison between groups, a significant difference was observed in the two groups in terms of height and head circumference (P &lt;0.001).&#x0D; Conclusion: The findings of this study show that multisensory stimulation affects the physical development of premature infants.