Brain Mechanism for Enhanced Hand Function with Remote Sensory Stimulation

The neurological bases for remote vibration enhanced sensory feedback and motor function are yet poorly understood. The purpose of this dissertation was to identify and examine the effect of vibration on finger tactile sensation in healthy adults and how imperceptible random vibration applied to the wrist changes cortical activity for fingertip sensation and precision grip. In a series of studies on healthy adults, white-noise vibration was applied to one of four locations (dorsum hand by the second knuckle, thenar and hypothenar areas, and volar wrist) at one of four intensities (zero, 60%, 80%, and 120% of the sensory threshold for each vibration location), while the fingertip sensation, the smallest vibratory signal that could be perceived on the thumb and index fingertip pads, was assessed. Vibration intensities significantly affected the fingertip sensation (p.01), all compared with the zero vibration condition. The next step was to examine the cortical activity for this vibration-enhanced fingertip sensation. We measured somatosensory evoked potentials to assess peak-to-peak response to light touch of the index fingertip with applied wrist vibration versus without. We observed increased peak-to-peak somatosensory evoked potentials with wrist vibration, especially with increased amplitude of the later component for the somatosensory, motor, and premotor cortex with wrist vibration. These findings corroborate an enhanced cortical-level sensory response motivated by vibration. It is possible that the cortical modulation observed here is the result of the establishment of transient networks for improved perception. Finally, we examined the effect of imperceptible vibration applied to the wrist on cortical control for precision grip. We measured β-band power to assess peak-to-peak response while subjects performed precision pinch with wrist vibration versus without. We observed increased peak-to-peak β-band power amplitude with wrist vibration, especially with event-related synchronization for the prefrontal, sensorimotor, motor, premotor, and supplementary motor areas with vibration. The enhanced motor function may possibly be a result of higher recalibration following movement and faster motor learning

Effect of Remote Vibrotactile Noise on Pinch Force Maintenance Ability and Brain Activity

Noise has been used to enhance detection of signals thereby improving performance of nonlinear systems (referred to as stochastic resonance ). In biological systems, the noise and signal integration may occur not only at the receptor level but also in the central nervous system, thereby allowing noise remotely applied from a signal to enhance the system\u27s response to the signal. However, integration of tactile signal and noise within the central nervous system has not been demonstrated in humans. In addition, whether the enhanced detection of tactile signals with remote noise results in changes in motor behavior is unknown. The objectives of this thesis were to elucidate the effect of remote vibrotactile noise on hand motor control (Aim 1) and to demonstrate feasibility for quantifying the effect of remote vibrotactile noise on electroencephalography (EEG) activity (Aim 2). Aim 1 found that remote vibrotactile noise had little effect on young, healthy persons\u27 ability to maintain a target pinch force level. While remote noise may have enhanced people\u27s ability to detect very weak signals such as the monofilament stimulation in a previous study, it appears that remote noise was not effective during pinching activity involving strong tactile signals in this thesis. Aim 2 developed methods for quantifying the effect of remote vibrotactile noise on the somatosensory cortex EEG activity in response to monofilament stimulation at the fingertip. A pilot data from one subject showed a trend for strengthened sensation/sensory feedback and sensorimotor information processing, as evidenced by increased peak-to-peak amplitude of event-related potentials and changes in power spectral densities with remote vibrotactile noise at 60% of sensory threshold, but not at 80% and 120% of the sensory threshold. In conclusion, this thesis demonstrated that remote vibrotactile noise did not influence young healthy adults\u27 ability to maintain pinch force. This thesis also demonstrated the ability for quantifying the effect of remote vibrotactile noise on EEG activity in response to fingertip stimulation, with a trend for improved sensory information processing. The results of this thesis may guide future investigation regarding the use of remote vibrotactile noise to influence brain activity, tactile sensing, and motor control

Effect of Remote Sensory Noise on Hand Function Post Stroke

Hand motor impairment persists after stroke. Sensory inputs may facilitate recovery of motor function. This pilot study tested the effectiveness of tactile sensory noise in improving hand motor function in chronic stroke survivors with tactile sensory deficits, using a repeated measures design. Sensory noise in the form of subthreshold, white noise, mechanical vibration was applied to the wrist skin during motor tasks. Hand dexterity assessed by the Nine Hole Peg Test and the Box and Block Test and pinch strength significantly improved when the sensory noise was turned on compared with when it was turned off in chronic stroke survivors. The subthreshold sensory noise to the wrist appears to induce improvements in hand motor function possibly via neuronal connections in the sensoriomotor cortex. The approach of applying concomitant, unperceivable mechanical vibration to the wrist during hand motor tasks is easily adoptable for clinic use as well as unsupervised home use. This pilot study suggests a potential for a wristband-type assistive device to complement hand rehabilitation for stroke survivors with sensorimotor deficit

Role of Sensation in Altered Phalanx Grip Force in Persons with Stroke

Many individuals experience hand impairment after stroke leading to decreased ability to perform daily living activities. Previous research studies have investigated how stroke survivors\u27 pinch grip control differs from healthy individuals, even though many individuals can only grasp with power grip after stroke. Furthermore, many stroke survivors experience tactile sensory deficit in their paretic limb in addition to motor deficit. It is currently unknown how stroke induced tactile sensory deficit affects power grip force directional control, which is important in terms of preventing object slippage and power grip normal force generation. Additionally it is unknown if power grip could be improved through tactile sensory enhancement. This dissertation investigated how stroke survivors\u27 power grip force control is different from healthy individuals. Also, the effect of stroke induced tactile sensory deficit on power grip force control and the benefits of a sensory enhancement method using remote subsensory vibrotactile noise on power grip phalanx force deviation was assessed. In addition, the effect of noise on the tactile sensation for stroke survivors with tactile sensory deficit and their performance on two dynamic gripping tasks, the Box and Block Test (`BBT\u27, number of blocks moved in 60 seconds) and the Nine Hole Peg Test (`NHPT\u27, time to pick up, place, and remove 9 pegs from 9 holes), were investigated. The theoretical framework of this dissertation is that tactile sensation is critical for grip control and impairment or enhancement of tactile sensation impacts power grip force control post stroke. Results showed that stroke survivors, especially those with tactile sensory deficit, gripped with increased phalanx force deviation compared to healthy individuals, showing reduced directional force control and increasing their chances of dropping objects. Remote subsensory vibrotactile noise improved fingertip and upper palm tactile sensation for stroke survivors with tactile sensory deficit. The noise also improved phalanx force directional control during power grip (reducing phalanx force deviation) for stroke survivors with and without tactile sensory deficit and age-matched healthy controls and improved the BBT score and time to complete the NHPT for stroke survivors with tactile sensory deficit. Overall, stroke survivors, particularly those with tactile sensory deficit, appear to have reduced phalanx force control during power grip, which may biomechanically result from a muscle activation pattern. Remote subsensory vibrotactile noise may have enhanced tactile sensation and hand motor control via stochastic resonance and interneuronal connections and could have potential as a wearable rehabilitation device for stroke survivors. This dissertation contributes to the long term goal of increasing stroke survivors\u27 independence in completing daily living activities

Avaliação dos efeitos da estimulação vibrotátil senoidal no controle neurofisiológico da força muscular

Orientador: Leonardo Abdala EliasTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A realimentação das vias sensoriais periféricas é de suma importância, não apenas para a percepção sensorial, mas também para o controle neural dos movimentos voluntários. As aferentes cutâneas são responsáveis por uma ampla gama de sensações de toque e têm um papel crucial na modulação do comportamento motor. Um interessante efeito induzido pela estimulação dos mecanorreceptores cutâneos é a melhora do desempenho sensório-motor. O efeito benéfico da estimulação vibrotátil é atribuído à ocorrência de ressonância estocástica no sistema nervoso. A hipótese principal é que uma intensidade específica do estímulo vibrotátil aumentaria o influxo das aferentes, melhorando assim a integração sensório-motora no sistema nervoso central. Neste trabalho, pretendemos avaliar os efeitos de uma estimulação vibrotátil senoidal no controle neurofisiológico da força muscular. Primeiramente, exploramos os efeitos da estimulação vibrotátil senoidal na variabilidade da força muscular durante tarefas visuomotoras isométricas. Ademais, avaliamos a influência da intensidade de contração e lateralidade na melhora motora causada pela estimulação vibrotátil. Por fim, avaliamos as propriedades de disparos de uma população de unidades motoras registradas durante uma tarefa motora aprimorada pela estimulação vibrotátil. No final deste material, forneceremos novas interpretações dos mecanismos neurofisiológicos por trás da influência das aferentes sensoriais cutâneas no controle da força muscularAbstract: Peripheral feedback is of paramount importance not only for sensory perception but also for the neural control of voluntary movements. Cutaneous afferents are responsible for a wide range of touch sensation and have a crucial role in modulating motor behavior. An exciting effect induced by the stimulation of mechanoreceptors at the skin is the improvement of sensorimotor performance. The beneficial effect of vibrotactile stimulation is attributed to the occurrence of stochastic resonance in the nervous system. The central hypothesis is that a specific intensity of vibrotactile stimulus would increase the afferent inflow, thereby improving the sensorimotor integration in the central nervous system. In this work, we aim at evaluating the effects of a sinusoidal vibrotactile stimulation on the neurophysiological control of muscle force. We first explored the effects of sinusoidal vibrotactile stimulation on force steadiness during isometric visuomotor tasks. We further evaluated the influence of contraction intensity and handedness on the motor improvement caused by vibrotactile stimulation. Finally, we evaluated the firing properties of a population of motor units recorded during a motor-enhanced task. At the end of this material, we will provide novel interpretations on the neurophysiological mechanisms behind the influence of cutaneous sensory inputs on muscle force controlDoutoradoEngenharia BiomédicaDoutora em Engenharia Elétrica88881.134842/2016-01CAPE

Stochastic Resonance Reduces Sway and Gait Variability in Individuals With Unilateral Transtibial Amputation: A Pilot Study

Sub-threshold (imperceptible) vibration, applied to parts of the body, impacts how people move and perceive our world. Could this idea help someone who has lost part of their limb? Sub-threshold vibration was applied to the thigh of the affected limb of 20 people with unilateral transtibial amputation. Vibration conditions tested included two noise structures: pink and white. Center of pressure (COP) excursion (range and root-mean-square displacements) during quiet standing, and speed and spatial stride measures (mean and standard deviations of step length and width) during walking were assessed. Pink noise vibration decreased COP displacements in standing, and white noise vibration decreased sound limb step length standard deviation in walking. Sub-threshold vibration positively impacted aspects of both posture and gait; however, different noise structures had different effects. The current study represents foundational work in understanding the potential benefits of incorporating stochastic resonance as an intervention for individuals with amputation

A Pilot Study To Investigate The Effects Of Imperceptible Wrist Vibration On The Corticospinal Motor Excitability Of Healthy Adults

The study investigated changes in corticomotor excitability of healthy adults with imperceptible white-noise vibration applied to the wrist. Previous studies have shown that the application of unperceivable white-noise vibration to the wrist induced improvements in sensory and motor function of the hand, not only in stroke survivors but also in healthy adults (Seo et al., 2014; Hur et al., 2014; Enders et al., 2013; Lakshminarayanan et al., 2015). Despite the potential that this vibration protocol me be adopted for therapy and in daily living activities to result in clinical benefits of stroke survivors and others with sensorimotor issues, knowledge about the way this vibration affects the neurophysiology, specifically the sensorimotor excitability, is not well understood. The purpose of this study was to investigate the neurophysiological effects of the imperceptible white-noise vibration on corticospinal motor excitability of the hand. Motor excitability was assessed using Transcranial Magnetic Stimulation (TMS), and by measuring the cortical silent period, intracortical inhibition and facilitation, and slope of the recruitment curve of the primary motor cortex for a hand muscle. These measures were compared between the vibration on and off conditions which were tested in a random order. Twelve healthy adults were tested. The results showed that the vibration resulted in marginally less intracortical inhibition when compared to the off condition (p 0.29). Taken together with previous studies, imperceptible white-noise vibration may improve hand function by enhancing sensation and not directly the motor excitability of the hand, although more Subjects need to be tested for intracortical inhibition. This study contributes to elucidating neural mechanisms of the vibration-based sensory stimulation approach

IEEE Trans Biomed Eng

Timely reaction to perturbation is important in activities of daily living. Modulation of reaction time to and early recovery from perturbation via vibrotactile noise was investigated. It was hypothesized that subthreshold vibrotactile noise applied to the upper extremity can accelerate a person's reaction to and recovery from handle perturbation. This intervention was developed based on previous studies in which the earliest cue available for people to detect handle perturbation was somatosensation detecting changes in pressure on the hand whose sensitivity can improve with subthreshold vibrotactile noise. To induce a handle perturbation, a sudden upward load was applied to the handle that subjects were lightly grasping. Eighteen healthy subjects were instructed to stop the handle from moving up when they detected the perturbation. The muscle reaction time and handle stabilization time with and without vibrotactile noise were determined. The results showed that the muscle reaction time and handle stabilization time significantly decreased by 3 ms ( ) and 6 ms ( ), respectively, when vibrotactile noise was applied to the upper extremity, regardless of where the noise was applied among four different locations within the upper extremity ( p > 0.05). In conclusion, the application of subthreshold vibrotactile noise enhanced persons' muscle reaction time to handle perturbation and led to early recovery from the perturbation. Use of the vibrotactile noise may increase a person's ability to rapidly respond to perturbation of a grasped object in potentially dangerous situations such as holding onto ladder rungs from elevation or manipulating knives.T42 OH008672/OH/NIOSH CDC HHSUnited States/UIC ERC T42OH008672/OH/NIOSH CDC HHSUnited States/2022-03-01T00:00:00Z24845272PMC888781611030vault:4099

Stochastic resonance in chua's circuit driven by alpha-stable noise

Thesis (Master)--Izmir Institute of Technology, Electronics and Communication Engineering, Izmir, 2012Includes bibliographical references (leaves: 75-80)Text in English; Abstract: Turkish and Englishx, 80 leavesThe main aim of this thesis is to investigate the stochastic resonance (SR) in Chua's circuit driven by alpha-stable noise which has better approximation to a real-world signal than Gaussian distribution. SR is a phenomenon in which the response of a nonlinear system to a sub-threshold (weak) input signal is enhanced with the addition of an optimal amount of noise. There have been an increasing amount of applications based on SR in various fields. Almost all studies related to SR in chaotic systems assume that the noise is Gaussian, which leads researchers to investigate the cases in which the noise is non-Gaussian hence has infinite variance. In this thesis, the spectral power amplification which is used to quantify the SR has been evaluated through fractional lower order Wigner Ville distribution of the response of a system and analyzed for various parameters of alpha-stable noise. The results provide a visible SR effect in Chua’s circuit driven by symmetric and skewed-symmetric alpha-stable noise distributions. Furthermore, a series of simulations reveal that the mean residence time that is the average time spent by the trajectory in an attractor can vary depending on different alpha-stable noise parameters