Virtual reality visual feedback and its effect on brain excitability

This dissertation examines manipulation of visual feedback in virtual reality (VR) to increase excitability of distinct neural networks in the sensorimotor cortex. The objective is to explore neural responses to visual feedback of motor activities performed in complex virtual environments during functional magnetic resonance imaging (fMRI), and to identify sensory manipulations that could further optimize VR rehabilitation of persons with hemiparesis. In addition, the effects of VR therapy on brain reorganization are investigated. An MRI-compatible VR system is used to provide subjects with online visual feedback of their hand movement. First, the author develops a protocol to analyze variability in movement kinematics between experimental sessions and conditions and its possible effect on modulating neural activity. Second, brain reorganization after 2 weeks of robot-assisted VR therapy is examined in 10 chronic stroke subjects in terms of change in extent of activation, interhemispheric dominance, connectivity network of ipsilesional primary motor cortex (iM1) and the interhemispheric interaction between iM 1 and contralesional M1 (cM 1). After training, brain activity during a simple paretic hand movement is re-localized in terms of bilateral change in activity or a shift of interhemispheric dominance (re-lateralization) toward the ipsilesional hemisphere that is positively correlated with improvement in clinical scores. Dynamic causal modeling (DCM) shows that interhemispheric coupling between the bilateral motor cortices tends to decrease after training and to negatively correlate with improvement in scores for clinical scales, and with the amount of re-lateralization. Third, the dissertation studies if visual discordance in VR of finger movement would facilitate activity in select brain networks. In a study of 12 healthy subjects, the amplitude of finger movement is manipulated (hypometric feedback) resulting in higher activation of contralateral M1. In a group of 11 stroke subjects, bidirectional, hypometric and hypermetric,VR visual discordance is used. Both feedback conditions cause small increase in activity of the iM1 contralateral to movement and stronger recruitment of both posterior parietal cortices and the ipsilesional fusiform gyrus (iFBA). Fourth, the effect of mirrored-visual feedback on the activity of the ipsilesional sensorimotor cortex of stroke subjects is examined. While subjects move the non-paretic hand during the fMRI experiment, they receive either veridical feedback of the movement or a mirrored feedback. The results show recruitment of iM1 and both posterior parietal cortices during the mirrored feedback. Effective connectivity analysis show increase correlation of iM1 and contralesional SPL (cSPL) with iFBA suggesting a role of the latter in the evaluation of feedback and in visuomotor processing. DCM analysis shows increased modulation of iM1 by cSPL area during the mirrored feedback, an observation that proves the influence of visual feedback on modulating primary motor cortex activation. This dissertation provides evidence that it is possible to enhance brain excitability through manipulation of virtual reality feedback and that brain reorganization can result from just two weeks of VR training. These findings should be exploited in the design of neuroscience-based rehabilitation protocols that could enhance brain reorganization and motor recovery

Using wavelet and template analysis to classify hand postures in unsupervised daily activities

This project\u27s goal was to identify determinants that characterize different types of activities an individual do in daily life, knowing the quality of hand function is essential to plan more effective rehabilitation therapies and treatments for upper limb movement disorders. The first part of the project was Jebsen-Taylor study where healthy individuals and individuals with brain injury performed seven activities classified as precision grasp, cylindrical grasp, and palmar grasp while metacarpal joint angles were measured in real time. The data from those seven activities was used to determine parameters that characterize each type of activity and which might be used as evaluation parameters after treatment. The determinants studied were the mean and variance of joints\u27 angles, range of motion, flexion and extension speed, and range of motion. A glove was used to record hand activity of an individual for 24 hours. Characteristics of these hand activities produce signals that are localized in both time and frequency, thus wavelet transform was used to detect the instance of change in the type of activity. Three clusters built after analyzing the seven activities were used to scan the 24 hr data and summarize the types of activity that had been performed by the subject in addition to reporting multiple parameters of the hand as range of motion and speed. The result was that the subject did no activity for 8 hours, precision grasp activities for 2 hours, palmar grasp activities for 12 hours and cylindrical grasp activities for 1 hour

A hidden cause of infertility in hypothyroid patients

Methylene tetrahydrofolate reductase (MTHFR) gene mutations could be the cause of infertility in hypothyroid patients. Hence, it is worthy to screen for MTHFR gene mutations in infertile hypothyroid females and their partners if infertility persists after optimizing thyroid function

Cascade of Nonlinear Entropy and Statistics to Discriminate Fetal Heart Rates

International audience—Fetal heart rate discrimination is an evolving field in biomedical engineering with many efforts dedicated to avoid preterm deliveries by way of improving fetus monitoring methods and devices. Entropy analysis is a nonlinear signal analysis technique that has been progressively developed to improve the discriminability of a several physiological signals, with Kernel based entropy parameters (KBEPs) found advantageous over standard techniques. This study is the first to apply KBEPs to analyze fetal heart rates. Specifically, it explores the usability of the cutting-edge nonlinear KBEPs in discriminating between healthy fetuses and fetuses under distress. The database used in this study comprises 50 healthy and 50 distressed fetal heart rate signals with severe intrauterine growth restriction. The Cascade analysis investigates six kernel based entropy measures on fetal heart rates discrimination, and compares them to four standard entropies. The study presents a statistical evaluation of the discrimination power of each parameter (paired t-test statistics and distribution spread). Simulation results showed that the distribution ranges in 80% of the entropy parameters in the distressed heart group are higher than those in the healthy control group. Moreover, the results show that it is advantageous to choose Circular entropy then Cauchy entropy (p < 0.001) over the standard techniques, in order to discriminate fetal heart rates

The New Jersey Institute of Technology Robot-Assisted Virtual Rehabilitation (NJIT-RAVR) system for children with cerebral palsy: a feasibility study

<p>Abstract</p> <p>Background</p> <p>We hypothesize that the integration of virtual reality (VR) with robot assisted rehabilitation could be successful if applied to children with hemiparetic CP. The combined benefits of increased attention provided by VR and the larger training stimulus afforded by adaptive robotics may increase the beneficial effects of these two approaches synergistically. This paper will describe the NJIT-RAVR system, which combines adaptive robotics with complex VR simulations for the rehabilitation of upper extremity impairments and function in children with CP and examine the feasibility of this system in the context of a two subject training study.</p> <p>Methods</p> <p>The NJIT-RAVR system consists of the Haptic Master, a 6 degrees of freedom, admittance controlled robot and a suite of rehabilitation simulations that provide adaptive algorithms for the Haptic Master, allowing the user to interact with rich virtual environments. Two children, a ten year old boy and a seven year old girl, both with spastic hemiplegia secondary to Cerebral Palsy were recruited from the outpatient center of a comprehensive pediatric rehabilitation facility. Subjects performed a battery of clinical testing and kinematic measurements of reaching collected by the NJIT-RAVR system. Subjects trained with the NJIT-RAVR System for one hour, 3 days a week for three weeks. The subjects played a combination of four or five simulations depending on their therapeutic goals, tolerances and preferences. Games were modified to increase difficulty in order to challenge the subjects as their performance improved. The testing battery was repeated following the training period.</p> <p>Results</p> <p>Both participants completed 9 hours of training in 3 weeks. No untoward events occurred and no adverse responses to treatment or complaints of cyber sickness were reported. One participant showed improvements in overall performance on the functional aspects of the testing battery. The second subject made improvements in upper extremity active range of motion and in kinematic measures of reaching movements.</p> <p>Conclusion</p> <p>We feel that this study establishes the feasibility of integrating robotics and rich virtual environments to address functional limitations and decreased motor performance in children with mild to moderate cerebral palsy.</p

The Role of Premotor Areas in Dual Tasking in Healthy Controls and Persons With Multiple Sclerosis: An fNIRS Imaging Study

Persons with multiple sclerosis (pwMS) experience declines in physical and cognitive abilities and are challenged by dual-tasks. Dual-tasking causes a drop in performance, or what is known as dual-task cost (DTC). This study examined DTC of walking speed (WS) and cognitive performance (CP) in pwMS and healthy controls (HCs) and the effect of dual-tasking on cortical activation of bilateral premotor cortices (PMC) and bilateral supplementary motor area (SMA). Fourteen pwMS and 14 HCs performed three experimental tasks: (1) single cognitive task while standing (SingCog); (2) single walking task (SingWalk); and (3) dual-task (DualT) that included concurrent performance of the SingCog and SingWalk. Six trials were collected for each condition and included measures of cortical activation, WS and CP. WS of pwMS was significantly lower than HC, but neuropsychological (NP) measures were not significantly different. pwMS and HC groups had similar DTC of WS, while DTC of CP was only significant in the MS group; processing speed and visual memory predicted 55% of this DTC. DualT vs. SingWalk recruited more right-PMC activation only in HCs and was associated with better processing speed. DualT vs. SingCog recruited more right-PMC activation and bilateral-SMA activation in both HC and pwMS. Lower baseline WS and worse processing speed measures in pwMS predicted higher recruitment of right-SMA (rSMA) activation suggesting maladaptive recruitment. Lack of significant difference in NP measures between groups does not rule out the influence of cognitive factors on dual-tasking performance and cortical activations in pwMS, which might have a negative impact on quality of life

Lower extremity robotic exoskeleton devices for overground ambulation recovery in acquired brain injury—A review

Acquired brain injury (ABI) is a leading cause of ambulation deficits in the United States every year. ABI (stroke, traumatic brain injury and cerebral palsy) results in ambulation deficits with residual gait and balance deviations persisting even after 1 year. Current research is focused on evaluating the effect of robotic exoskeleton devices (RD) for overground gait and balance training. In order to understand the device effectiveness on neuroplasticity, it is important to understand RD effectiveness in the context of both downstream (functional, biomechanical and physiological) and upstream (cortical) metrics. The review identifies gaps in research areas and suggests recommendations for future research. We carefully delineate between the preliminary studies and randomized clinical trials in the interpretation of existing evidence. We present a comprehensive review of the clinical and pre-clinical research that evaluated therapeutic effects of RDs using various domains, diagnosis and stage of recovery

Evaluation of Homocysteine, Folic Acid and Vitamin B12 Levels among Egyptian Children with Idiopathic Epilepsy

Objective: To evaluate relationship between homocysteine (Hcy), folic acid and vitamin B12 with anti-epileptic drugs in epileptic patients and their role in epilepsy control.Patient and Methods: The study included 60 patients with idiopathic epilepsy and thirty non-epileptic children of the same age and sex served as controls. All cases were subjected to physical and neurological examination and electroencephalogram (EEG). Serum level of folic acid, homocysteine (Hcy) and vitamin B12 were done for both epileptic patients and controls. Non parametric test, one way ANOVA and Pearson’s correlation were used for analysis of data.Result: 44 patients (73.3%) had generalized epilepsy and the remaining patients had partial epilepsy (simple or complex). 37 patients (61.6%) were in grade I, 3 patients (5 %) were in grade II and the remaining 20 patients (33.3 %) were in grade III epilepsy. Vitamin B12 was significantly higher in epileptic patients. Duration of anti-epileptic drug treatment was correlated significantly to folic acid and Hcy level.Conclusion: antiepileptic drugs might upset the homeostatic balance of Hcy and its cofactors and cause abnormalities of their serum levels. The duration of anti-epileptic drug treatment was related to decrease of folic acid and increase in homocysteine levels

Neural Patterns of Reorganization after Intensive Robot-Assisted Virtual Reality Therapy and Repetitive Task Practice in Patients with Chronic Stroke

Several approaches to rehabilitation of the hand following a stroke have emerged over the last two decades. These treatments, including repetitive task practice (RTP), robotically assisted rehabilitation and virtual rehabilitation activities, produce improvements in hand function but have yet to reinstate function to pre-stroke levels—which likely depends on developing the therapies to impact cortical reorganization in a manner that favors or supports recovery. Understanding cortical reorganization that underlies the above interventions is therefore critical to inform how such therapies can be utilized and improved and is the focus of the current investigation. Specifically, we compare neural reorganization elicited in stroke patients participating in two interventions: a hybrid of robot-assisted virtual reality (RAVR) rehabilitation training and a program of RTP training. Ten chronic stroke subjects participated in eight 3-h sessions of RAVR therapy. Another group of nine stroke subjects participated in eight sessions of matched RTP therapy. Functional magnetic resonance imaging (fMRI) data were acquired during paretic hand movement, before and after training. We compared the difference between groups and sessions (before and after training) in terms of BOLD intensity, laterality index of activation in sensorimotor areas, and the effective connectivity between ipsilesional motor cortex (iMC), contralesional motor cortex, ipsilesional primary somatosensory cortex (iS1), ipsilesional ventral premotor area (iPMv), and ipsilesional supplementary motor area. Last, we analyzed the relationship between changes in fMRI data and functional improvement measured by the Jebsen Taylor Hand Function Test (JTHFT), in an attempt to identify how neurophysiological changes are related to motor improvement. Subjects in both groups demonstrated motor recovery after training, but fMRI data revealed RAVR-specific changes in neural reorganization patterns. First, BOLD signal in multiple regions of interest was reduced and re-lateralized to the ipsilesional side. Second, these changes correlated with improvement in JTHFT scores. Our findings suggest that RAVR training may lead to different neurophysiological changes when compared with traditional therapy. This effect may be attributed to the influence that augmented visual and haptic feedback during RAVR training exerts over higher-order somatosensory and visuomotor areas