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Functional principal component analysis as a new methodology for the analysis of the impact of two rehabilitation protocols in functional recovery after stroke

JNER - Wed, 09/10/2014 - 00:00
Background: This study addressed the problem of evaluating the effectiveness of two protocols of physiotherapy for functional recovery after stroke. In particular, the study explored the use of Functional Principal Component Analysis (FPCA), a multivariate data analysis in order to assess and clarify the process of regaining independence after stroke. Methods: A randomized double-blind controlled trial was performed. Thirteen subjects with residual hemiparesis after a single stroke episode were measured in both in- and outpatient settings at a district hospital. All subjects were able to walk before suffering the stroke and were hemodynamically stable within the first week after stroke. Control and target groups were treated with conventional physiotherapy for stroke, but specific techniques were added for treatment of the target group depending on patients’ functional levels.Independence level was assessed with the Barthel Index (BI) throughout 7 evolution stages (hemodynamic stability, beginning of standing, beginning of physical therapy sessions in the physiotherapy ward and monthly assessment for 6 months after stroke). Results: FPCA was applied for data analysis. Statistically significant differences were found in the dynamics of the recovery process between the two physiotherapy protocols. The target group showed a trend of improvement six months after stroke that was not present in the control group. Conclusions: FPCA is a method which may be used to provide greater insight into the analysis of the rehabilitation process than that provided by conventional parametric methods. So, by using the whole curves as basic data parameters, subtle differences in the rehabilitation process can be found.FPCA represents a future aid for the fine analysis of similar physiotherapy techniques, when applied in subjects with a huge variability of functional recovery, as in the case of post-stroke patients.

Infant trunk posture and arm movement assessment using pressure mattress, inertial and magnetic measurement units (IMUs)

JNER - Sat, 09/06/2014 - 00:00
Background: Existing motor pattern assessment methods, such as digital cameras and optoelectronic systems, suffer from object obstruction and require complex setups. To overcome these drawbacks, this paper presents a novel approach for biomechanical evaluation of newborn motor skills development. Multi-sensor measurement system comprising pressure mattress and IMUs fixed on trunk and arms is proposed and used as alternative to existing methods. Observed advantages seem appealing for the focused field and in general. Combined use of pressure distribution data and kinematic information is important also for posture assessment, ulcer prevention, and non-invasive sleep pattern analysis of adults. Methods: Arm kinematic parameters, such as root-mean-square acceleration, spectral arc length of hand velocity profile, including arm workspace surface area, and travelled hand path are obtained with the multi-sensor measurement system and compared to normative motion capture data for evaluation of adequacy. Two IMUs per arm, only one IMU on upper arm, and only one IMU on forearm sensor placement options are studied to assess influence of system configuration on method precision. Combination of pressure mattress and IMU fixed on the trunk is used to measure trunk position (obtained from mat), rotation (from IMUs) and associated movements on surface (from both). Measurement system is first validated on spontaneous arm and trunk movements of a dedicated baby doll having realistic anthropometric characteristics of newborns. Next, parameters of movements in a healthy infant are obtained with pressure mattress, along with trunk and forearm IMU sensors to verify appropriateness of method and parameters. Results: Evaluation results confirm that full sensor set, comprising pressure mattress and two IMUs per arm is a reliable substitution to optoelectronic systems. Motor pattern parameter errors are under 10% and kinematic estimation error is in range of 2 cm. Although, use of only forearm IMU is not providing best possible kinematic precision, the simplicity of use and still acceptable accuracy are convincing for frequent practical use. Measurements demonstrated system high mobility and usability. Conclusions: Study results confirm adequacy of the proposed multi-sensor measurement system, indicating its enviable potential for accurate infant trunk posture and arm movement assessment.

Comparison of range-of-motion and variability in upper body movements between transradial prosthesis users and able-bodied controls when executing goal-oriented tasks

JNER - Sat, 09/06/2014 - 00:00
Background: Current upper limb prostheses do not replace the active degrees-of-freedom distal to the elbow inherent to intact physiology. Limited evidence suggests that transradial prosthesis users demonstrate shoulder and trunk movements to compensate for these missing volitional degrees-of-freedom. The purpose of this study was to enhance understanding of the effects of prosthesis use on motor performance by comparing the movement quality of upper body kinematics between transradial prosthesis users and able-bodied controls when executing goal-oriented tasks that reflect activities of daily living. Methods: Upper body kinematics were collected on six able-bodied controls and seven myoelectric transradial prosthesis users during execution of goal-oriented tasks. Range-of-motion, absolute kinematic variability (standard deviation), and kinematic repeatability (adjusted coefficient-of-multiple-determination) were quantified for trunk motion in three planes, shoulder flexion/extension, shoulder ab/adduction, and elbow flexion/extension across five trials per task. Linear mixed models analysis assessed between-group differences and correlation analysis evaluated association between prosthesis experience and kinematic repeatability. Results: Across tasks, prosthesis users demonstrated increased trunk motion in all three planes and shoulder abduction compared to controls (p ≤ 0.004). Absolute kinematic variability was greater for prosthesis users for all degrees-of-freedom irrespective of task, but was significant only for degrees-of-freedom that demonstrated increased range-of-motion (p ≤ 0.003). For degrees-of-freedom that did not display increased absolute variability for prosthesis users, able-bodied kinematics were characterized by significantly greater repeatability (p ≤ 0.015). Prosthesis experience had a strong positive relationship with average kinematic repeatability (r = 0.790, p = 0.034). Conclusions: The use of shoulder and trunk movements by prosthesis users as compensatory motions to execute goal-oriented tasks demonstrates the flexibility and adaptability of the motor system. Increased variability in movement suggests that prosthesis users do not converge on a defined motor strategy to the same degree as able-bodied individuals. Kinematic repeatability may increase with prosthesis experience, or encourage continued device use, and future work is warranted to explore these relationships. As compensatory dynamics may be necessary to improve functionality of transradial prostheses, users may benefit from dedicated training that encourages optimization of these dynamics to facilitate execution of daily living activity, and fosters adaptable but reliable motor strategies.

Measures of gait stability: performance on adults and toddlers at the beginning of independent walking

JNER - Wed, 09/03/2014 - 00:00
Background: Quantifying gait stability is a topic of high relevance and a number of possible measures have been proposed. The problem in validating these methods is the necessity to identify a-priori unstable individuals. Since proposed methods do not make any assumption on the characteristics of the subjects, the aim of the present study was to test the performance of gait stability measures on individuals whose gait is a-priori assumed unstable: toddlers at the onset of independent walking. Methods: Ten toddlers, ten adults and ten elderly subjects were included in the study. Data from toddlers were acquired longitudinally over a 6-month period to test if the methods detected the increase in gait stability with experience, and if they could differentiate between toddlers and young adults. Data from elderly subjects were expected to indicate a stability value in between the other two groups. Accelerations and angular velocities of the trunk and of the leg were measured using two tri-axial inertial sensors. The following methods for quantifying gait stability were applied: stride time variability, Poincaré plots, harmonic ratio, short term Lyapunov exponents, maximum Floquet multipliers, recurrence quantification analysis and multiscale entropy. An unpaired t-test (level of significance of 5%) was performed on the toddlers and the young adults for each method and, for toddlers, for each evaluated stage of gait development. Results: Methods for discerning between the toddler and the adult groups were: stride time variability, Poincaré plots, harmonic ratio, short term Lyapunov exponents (state space composed by the three linear accelerations of the trunk), recurrence quantification analysis and multiscale entropy (when applied on the vertical or on the antero-posterior L5 accelerations). Conclusions: Results suggested that harmonic ratio and recurrence quantification analysis better discern gait stability in the analyzed subjects, differentiating not only between unstable toddlers and stable healthy adults, but also evidencing the expected trend of the toddlers towards a higher stability with walking experience, and indicating elderly subjects as stable as or less stable than young adults.

Postural stabilization during bilateral and unilateral vibration of ankle muscles in the sagittal and frontal planes

JNER - Mon, 09/01/2014 - 00:00
Background: The purpose was to investigate the postural consequences of proprioceptive perturbation of the Triceps Surae and Peroneus Longus muscles. These muscles are known to control posture respectively in the sagittal and frontal planes during standing. Methods: Standard parameters and the time course of center of pressure (CoP) displacements were recorded in 21 young adults, instructed to maintain their balance during tendon vibration. Following 4 s of baseline recording, three types of vibration (80 Hz) were applied for 20 s each on the Peroneus or Achilles tendons, either unilaterally or bilaterally (with eyes shut). The recording continued for a further 24 s after the end of the vibration during the re-stabilization phase. To evaluate the time course of the CoP displacement, each phase of the trial was divided into periods of 4 seconds. Differences between the type of tendon vibration, phases and periods were analyzed using ANOVA. Results: During all tendon vibrations, the speed of the CoP increased and a posterior displacement occurred. These changes were greater during Achilles than during Peroneus vibration for each type of vibration and also during bilateral compared with unilateral vibration. All maximal posterior positions occurred at a similar instant (between 12.7 and 14 s of vibration). Only unilateral Achilles vibration led to a significant medio-lateral displacement compared to the initial state. Conclusions: The effect of the proprioceptive perturbation seems to be influenced by the position of the vibrated muscle according to the planes of the musculoskeletal postural organization. The amplitude of the destabilization may be related to the importance of the muscle for postural control. The medial CoP displacement which occurred during unilateral Achilles vibration is not a general reaction to a single-limb perturbation. Proprioceptive input from the non-perturbed leg was not sufficient for the antero-posterior displacement to be avoided; however, it helped to gain stability over time. The non-perturbed limb clearly plays an important role in the restoration of the postural referential, both during and immediately following the end of the vibration. The results demonstrated that at least 16 s of vibration are necessary to induce most postural effects in young adults.

Muscle synergy stability and human balance maintenance

JNER - Sat, 08/30/2014 - 00:00
Background: The signals that the central nervous system (CNS) produces and sends to the muscles to effect movement are not entirely understood. Muscle synergy theory suggests that the central nervous system produces a small number of signals that pass through a network that distributes combinations of these signals to the muscles. Though these synergies are rather stable over time, some variability is present. Methods: Here, we investigated the variability of muscle synergy and defined a synergy stability index (SSI) to quantify it. We measured the activity of muscles responsible for maintaining lateral balance in humans standing on a platform that was subjected to lateral disturbance from the platform. We then calculated muscle synergies attributed to postural reflex and automatic response by using non-negative matrix factorization (NMF). Finally, from the calculated muscle synergies, we obtained SSI. Results: We observed a positive proportional relation between balance performance and SSI. Participants who were adept at maintaining balance were found to have invariant muscle synergies, and non-adept participants showed variable muscle synergies. Conclusions: These results suggest that SSI can be used to quantitatively evaluate balance maintenance ability.

The influence of fear of falling on gait variability: results from a large elderly population-based cross-sectional study

JNER - Fri, 08/29/2014 - 00:00
ObjectiveTo compare gait variability among older community-dwellers with and without fear of falling and history of falls, and 2) to examine the association between gait variability and fear of falling while taking into account the effect of potential confounders. Methods: Based on a cross-sectional design, 1,023 French community-dwellers (mean age ± SD, 70.5 ± 5.0 years; 50.7% women) were included in this study. The primary endpoints were fear of falling, stride-to-stride variability of stride time and walking speed measured using GAITRite® system. Age, gender, history of falls, number of drugs daily taken per day, body mass index, lower-limb proprioception, visual acuity, use of psychoactive drugs and cognitive impairment were used as covariables in the statistical analysis. P-values less than 0.05 were considered as statistically significant. Results: A total of 60.5% (n = 619) participants were non-fallers without fear of falling, 19% (n = 194) fallers without fear of falling, 9.9% (n = 101) non-fallers with fear of falling, and 10.7% (n = 109) fallers with fear of falling. Stride-to-stride variability of stride time was significantly higher in fallers with fear of falling compared to non-fallers without fear of falling. Full adjusted linear regression models showed that only lower walking speed value was associated to an increase in stride-to-stride variability of stride time and not fear of falling, falls or their combination. While using a walking speed ≥1.14 m/s (i.e., level of walking speed that did not influence stride-to-stride variability of stride time), age and combination of fear of falling with history of previous falls were significantly associated with an increased stride-to-stride variability of stride time. Conclusions: The findings show that the combination of fear of falling with falls increased stride-to-stride variability of stride time. However, the effect of this combination depended on the level of walking speed, increase in stride-to-stride variability of stride time at lower walking speed being related to a biomechanical effect overriding fear of falling-related effects.

Kinematics of turning during walking over ground and on a rotating treadmill

JNER - Sat, 08/23/2014 - 00:00
Background: After neurological injury, gait rehabilitation typically focuses on task oriented training with many repetitions of a particular movement. Modern rehabilitation devices, including treadmills, augment gait rehabilitation. However, they typically provide gait training only in the forward direction of walking, hence the mechanisms associated with changing direction during turning are not practiced. A regular treadmill extended with the addition of rotation around the vertical axis is a simple device that may enable the practice of turning during walking. The objective of this study was to investigate to what extent pelvis and torso rotations in the transversal plane, as well as stride lengths while walking on the proposed rotating treadmill, resemble those in over ground turning. Methods: Ten neurologically and orthopedically intact subjects participated in the study. We recorded pelvis and torso rotations in the transversal plane and the stride lengths during over ground turning and while walking on a rotating treadmill in four experimental conditions of turning. The similarity between pelvis and torso rotations in over ground turning and pair-matching walking on the rotating treadmill was assessed using intra-class correlation coefficient (ICC - two-way mixed single measure model). Finally, left and right stride lengths in over ground turning as well as while walking on the rotating treadmill were compared using a paired t-test for each experimental condition. Results: An agreement analysis showed average ICC ranging between 0.9405 and 0.9806 for pelvis and torso rotation trajectories respectively, across all experimental conditions and directions of turning. The results of the paired t-tests comparing left and right stride lengths showed that the stride of the outer leg was longer than the stride of the inner leg during over ground turning as well as when walking on the rotating treadmill. In all experimental conditions these differences were statistically significant. Conclusions: In this study we found that pelvis rotation and torso rotation are similar when turning over ground as compared to walking on a rotating treadmill. Additionally, in both modes of turning, we found that the stride length of the outer leg is significantly longer than the stride length of the inner leg.

Comparing integrated training of the hand and arm with isolated training of the same effectors in persons with stroke using haptically rendered virtual environments, a randomized clinical trial

JNER - Sat, 08/23/2014 - 00:00
Background: Robotically facilitated therapeutic activities, performed in virtual environments have emerged as one approach to upper extremity rehabilitation after stroke. Body function level improvements have been demonstrated for robotically facilitated training of the arm. A smaller group of studies have demonstrated modest activity level improvements by training the hand or by integrated training of the hand and arm. The purpose of this study was to compare a training program of complex hand and finger tasks without arm movement paired with a separate set of reaching activities performed without hand movement, to training the entire upper extremity simultaneously, utilizing integrated activities. Methods: Forty individuals with chronic stroke recruited in the community, participated in a randomized, blinded, controlled trial of two interventions. Subjects were required to have residual hand function for inclusion. The first, hand and arm separate (HAS) training (n = 21), included activities controlled by finger movement only, and activities controlled by arm movement only, the second, hand and arm together (HAT) training (n = 20) used simulations controlled by a simultaneous use of arm and fingers. Results: No adverse reactions occurred. The entire sample demonstrated mean improvements in Wolf Motor Function Test scores (21%) and Jebsen Test of Hand Function scores (15%), with large effect sizes (partial r2 = .81 and r2 = .67, respectively). There were no differences in improvement between HAS and HAT training immediately after the study. Subjects in the HAT group retained Wolf Motor Function Test gains better than in the HAS group measured three months after the therapy but the size of this interaction effect was small (partial r2 = .17). Conclusions: Short term changes in upper extremity motor function were comparable when training the upper extremity with integrated activities or a balanced program of isolated activities. Further study of the retention period is indicated.Trial registrationNCT01072461.

Investigating the role of neuropathic pain relief in decreasing gait variability in diabetes mellitus patients with neuropathic pain: a randomized, double-blind crossover trial

JNER - Wed, 08/20/2014 - 00:00
Background: Subjects with diabetes mellitus (DM) develop gait dysfunction contributing to falls, reluctance to perform activities and injuries. Neuropathic pain (NeP) related to diabetic peripheral neuropathy (DPN) is associated with increased gait variability that may contribute to gait dysfunction. We used a portable device (GaitMeter™) and related gait and balance measures to measure gait parameters in painful DPN (PDPN) subjects prior to and during analgesia. Our hypothesis was that PDPN subjects would have decreased gait step variability when receiving pharmacological relief of NeP. Methods: DPN subjects with at least moderate NeP were assessed in a randomized, double-blind crossover study of pregabalin versus placebo. The outcome measure was variability in step length and step velocity. Testing for Timed Get-Up-and-Go Test, Tinetti Mobility Scales, Sway Testing, a Physiological Profile Approach, and fall-related surveys were also performed. DPN severity was quantified using the Utah Early Neuropathy Score. Results: PDPN subjects developed increased, rather than decreased, step length and step velocity variability during pregabalin treatment. There were no significant differences between cohorts for other physiological gait and balance testing. Non-significant NeP relief occurred in the pregabalin phase of study as compared with placebo. There was a negative relationship for step length with pain severity. Conclusion: Analgesia did not decrease gait variability in PDPN patients, and in fact, increased gait variability was seen during pregabalin treatment. Other important relationships of gait dysfunction with PDPN should be sought.

Facilitation of corticospinal excitability by virtual reality exercise following anodal transcranial direct current stimulation in healthy volunteers and subacute stroke subjects

JNER - Mon, 08/18/2014 - 00:00
Background: There is growing evidence that the combination of non-invasive brain stimulation and motor skill training is an effective new treatment option in neurorehabilitation. We investigated the beneficial effects of the application of transcranial direct current stimulation (tDCS) combined with virtual reality (VR) motor training. Methods: In total, 15 healthy, right-handed volunteers and 15 patients with stroke in the subacute stage participated. Four different conditions (A: active wrist exercise, B: VR wrist exercise, C: VR wrist exercise following anodal tDCS (1 mV, 20 min) on the left (healthy volunteer) or affected (stroke patient) primary motor cortex, and D: anodal tDCS without exercise) were provided in random order on separate days. We compared during and post-exercise corticospinal excitability under different conditions in healthy volunteers (A, B, C, D) and stroke patients (B, C, D) by measuring the changes in amplitudes of motor evoked potentials in the extensor carpi radialis muscle, elicited with single-pulse transcranial magnetic stimulation. For statistical analyses, a linear mixed model for a repeated-measures covariance pattern model with unstructured covariance within groups (healthy or stroke groups) was used. Results: The VR wrist exercise (B) facilitated post-exercise corticospinal excitability more than the active wrist exercise (A) or anodal tDCS without exercise (D) in healthy volunteers. Moreover, the post-exercise corticospinal facilitation after tDCS and VR exercise (C) was greater and was sustained for 20 min after exercise versus the other conditions in healthy volunteers (A, B, D) and in subacute stroke patients (B, D). Conclusions: The combined effect of VR motor training following tDCS was synergistic and short-term corticospinal facilitation was superior to the application of VR training, active motor training, or tDCS without exercise condition. These results support the concept of combining brain stimulation with VR motor training to promote recovery after a stroke.

A biomechanical cause of low power production during FES cycling of subjects with SCI

JNER - Sat, 08/16/2014 - 00:00
Background: The goal of Functional Electrical Stimulation (FES) cycling is to provide the health benefits of exercise to persons with paralysis. To achieve the greatest health advantages, patients should produce the highest possible mechanical power. However, the mechanical power output (PO) produced during FES cycling is very low. Unfavorable biomechanics is one of the important factors reducing PO. The purpose of this study was to investigate the primary joints and muscles responsible for power generation and the role of antagonistic co-contraction in FES cycling. Methods: Sixteen subjects with complete spinal cord injury (SCI) pedaled a stationary recumbent FES tricycle at 60 rpm and a workload of 15 W per leg, while pedal forces and crank angle were recorded. The joint muscle moments, power and work were calculated using inverse dynamics equations. Results: Two characteristic patterns were found; in 12 subjects most work was generated by the knee extensors in the propulsion phase (83% of total work), while in 4 subjects most work was shared between by the knee extensors (42%) and flexors (44%), respectively during propulsive and recovery phases. Hip extensors produced only low net work (12 & 7%). For both patterns, extra concentric work was necessary to overcome considerable eccentric work (-82 & -96%). Conclusions: The primary power sources were the knee extensors of the quadriceps and the knee flexors of the hamstrings. The antagonistic activity was generally low in subjects with SCI because of the weakness of the hamstrings (compared to quadriceps) and the superficial and insufficient hamstring mass activation with FES.

Continuous and simultaneous estimation of finger kinematics using inputs from an EMG-to-muscle activation model

JNER - Thu, 08/14/2014 - 00:00
Background: Surface electromyography (EMG) signals are often used in many robot and rehabilitation applications because these reflect motor intentions of users very well. However, very few studies have focused on the accurate and proportional control of the human hand using EMG signals. Many have focused on discrete gesture classification and some have encountered inherent problems such as electro-mechanical delays (EMD). Here, we present a new method for estimating simultaneous and multiple finger kinematics from multi-channel surface EMG signals.MethodIn this study, surface EMG signals from the forearm and finger kinematic data were extracted from ten able-bodied subjects while they were tasked to do individual and simultaneous multiple finger flexion and extension movements in free space. Instead of using traditional time-domain features of EMG, an EMG-to-Muscle Activation model that parameterizes EMD was used and shown to give better estimation performance. A fast feed forward artificial neural network (ANN) and a nonparametric Gaussian Process (GP) regressor were both used and evaluated to estimate complex finger kinematics, with the latter rarely used in the other related literature. Results: The estimation accuracies, in terms of mean correlation coefficient, were 0.85±0.07, 0.78±0.06 and 0.73±0.04 for the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and the distal interphalangeal (DIP) finger joint DOFs, respectively. The mean root-mean-square error in each individual DOF ranged from 5 to 15%. We show that estimation improved using the proposed muscle activation inputs compared to other features, and that using GP regression gave better estimation results when using fewer training samples. Conclusion: The proposed method provides a viable means of capturing the general trend of finger movements and shows a good way of estimating finger joint kinematics using a muscle activation model that parameterizes EMD. The results from this study demonstrates a potential control strategy based on EMG that can be applied for simultaneous and continuous control of multiple DOF(s) devices such as robotic hand/finger prostheses or exoskeletons.

Utilization of a novel digital measurement tool for quantitative assessment of upper extremity motor dexterity: a controlled pilot study

JNER - Wed, 08/13/2014 - 00:00
Background: The current methods of assessing motor function rely primarily on the clinician’s judgment of the patient’s physical examination and the patient’s self-administered surveys. Recently, computerized handgrip tools have been designed as an objective method to quantify upper-extremity motor function. This pilot study explores the use of the MediSens handgrip as a potential clinical tool for objectively assessing the motor function of the hand. Methods: Eleven patients with cervical spondylotic myelopathy (CSM) were followed for three months. Eighteen age-matched healthy participants were followed for two months. The neuromotor function and the patient-perceived motor function of these patients were assessed with the MediSens device and the Oswestry Disability Index respectively. The MediSens device utilized a target tracking test to investigate the neuromotor capacity of the participants. The mean absolute error (MAE) between the target curve and the curve tracing achieved by the participants was used as the assessment metric. The patients’ adjusted MediSens MAE scores were then compared to the controls. The CSM patients were further classified as either “functional” or “nonfunctional” in order to validate the system’s responsiveness. Finally, the correlation between the MediSens MAE score and the ODI score was investigated. Results: The control participants had lower MediSens MAE scores of 8.09%±1.60%, while the cervical spinal disorder patients had greater MediSens MAE scores of 11.24%±6.29%. Following surgery, the functional CSM patients had an average MediSens MAE score of 7.13%±1.60%, while the nonfunctional CSM patients had an average score of 12.41%±6.32%. The MediSens MAE and the ODI scores showed a statistically significant correlation (r=-0.341, p<1.14×10-5). A Bland-Altman plot was then used to validate the agreement between the two scores. Furthermore, the percentage improvement of the the two scores after receiving the surgical intervention showed a significant correlation (r=-0.723, p<0.04). Conclusions: The MediSens handgrip device is capable of identifying patients with impaired motor function of the hand. The MediSens handgrip scores correlate with the ODI scores and may serve as an objective alternative for assessing motor function of the hand.

Shotgun approaches to gait analysis: insights & limitations

JNER - Tue, 08/12/2014 - 00:00
Background: Identifying features for gait classification is a formidable problem. The number of candidate measures is legion. This calls for proper, objective criteria when ranking their relevance. Methods: Following a shotgun approach we determined a plenitude of kinematic and physiological gait measures and ranked their relevance using conventional analysis of variance (ANOVA) supplemented by logistic and partial least squares (PLS) regressions. We illustrated this approach using data from two studies involving stroke patients, amputees, and healthy controls. Results: Only a handful of measures turned out significant in the ANOVAs. The logistic regressions, by contrast, revealed various measures that clearly discriminated between experimental groups and conditions. The PLS regression also identified several discriminating measures, but they did not always agree with those of the logistic regression.Discussion & conclusionExtracting a measure’s classification capacity cannot solely rely on its statistical validity but typically requires proper post-hoc analysis. However, choosing the latter inevitably introduces some arbitrariness, which may affect outcome in general. We hence advocate the use of generic expert systems, possibly based on machine-learning.

Assessing the feasibility of online SSVEP decoding in human walking using a consumer EEG headset

JNER - Sat, 08/09/2014 - 00:00
Background: Bridging the gap between laboratory brain-computer interface (BCI) demonstrations and real-life applications has gained increasing attention nowadays in translational neuroscience. An urgent need is to explore the feasibility of using a low-cost, ease-of-use electroencephalogram (EEG) headset for monitoring individuals’ EEG signals in their natural head/body positions and movements. This study aimed to assess the feasibility of using a consumer-level EEG headset to realize an online steady-state visual-evoked potential (SSVEP)-based BCI during human walking. Methods: This study adopted a 14-channel Emotiv EEG headset to implement a four-target online SSVEP decoding system, and included treadmill walking at the speeds of 0.45, 0.89, and 1.34 meters per second (m/s) to initiate the walking locomotion. Seventeen participants were instructed to perform the online BCI tasks while standing or walking on the treadmill. To maintain a constant viewing distance to the visual targets, participants held the hand-grip of the treadmill during the experiment. Along with online BCI performance, the concurrent SSVEP signals were recorded for offline assessment. Results: Despite walking-related attenuation of SSVEPs, the online BCI obtained an information transfer rate (ITR) over 12 bits/min during slow walking (below 0.89 m/s). Conclusions: SSVEP-based BCI systems are deployable to users in treadmill walking that mimics natural walking rather than in highly-controlled laboratory settings. This study considerably promotes the use of a consumer-level EEG headset towards the real-life BCI applications.

Continuous gait cycle index estimation for electrical stimulation assisted foot drop correction

JNER - Sat, 08/09/2014 - 00:00
Background: Walking impairment after stroke can be addressed with the use of drop foot stimulators (DFS). Many studies have demonstrated that DFS improves walking speed, reduces spasticity and reduces the physiologic effort of walking. Current DFS, through activation of the common peroneal nerve, elicit ankle dorsiflexion during swing phase of gait. DFS are generally piloted by force sensing resistor placed in the shoe of the affected side with stimulation triggered ON by heel rise and triggered OFF by heel strike. A tilt sensor can also be used with stimulation triggered by the tilt of the shank of the affected leg. These triggering approaches are the standard for initiating stimulation. However, the real-time modulation of FES intensity to provide more optimized delivery of stimulation and also to regulate dorsiflexion in the presence of disturbances, such as fatigue and spasticity may increase the number of potential users of DFS. Concerning research domain, stimulators that would allow modulating the stimulation pattern in between heel rise and strike events would allow exploring new stimulation strategies. We propose to extract continuous information: the gait cycle index (GCI), from one inertial measurement unit (IMU) measuring shank tilt angle. In order to illustrate the use of this real-time information, we show the feasibility of piloting an electrical stimulator. Methods: 12 subjects with post-stroke hemiplegia participated. A wireless IMU was placed on the unaffected shank and was used to estimate GCI. Subjects performed 3 trials in each of the 3 conditions: C1 no stimulation aid, C2 electrical stimulation assistance triggered by heel switch, C3 electrical stimulation assistance triggered from GCI. Results: 1) the proposed algorithm was able to real-time estimate GCI, 2) events could be extracted from GCI information in order to trig a DFS. Conclusion: The estimation of the continuous GCI in individuals with stroke is possible. Events can be extracted from this information in order to trig a stimulator. These results are a first step towards the possibility to investigate new DFS paradigms based on real-time modulation of stimulation parameters.

The feasibility of using haptic devices to engage people with chronic traumatic brain injury in virtual 3D functional tasks

JNER - Fri, 08/08/2014 - 00:00
Background: The primary aim of this study was to assess the level of engagement in computer-based simulations of functional tasks, using a haptic device for people with chronic traumatic brain injury. The objectives were to design functional tasks using force feedback device and determine if it could measure motor performance improvement. Methods: A prospective crosssectional study was performed in a biomedical research facility. The testing environment consisted of a single, interactive, stylus-driven computer session navigating virtual scenes in 3D space. Subjects had a haptic training session (TRAIN) and then had three chances to perform each virtual task: (i) remove tools from a workbench (TOOL), (ii) compose 3 letter words (SPELL), (iii) manipulate utensils to prepare a sandwich (SAND), and (iv) tool use (TUSE). Main Outcome Measures included self-report of engagement in the activities, improved performance on simulated tasks and observer estimate as measured by time to completion or number of words completed from baseline, correlations among performance measures and self-reports of boredom, neuropsychological symptom inventory (NSI), and The Purdue Peg Motor Test (PPT). Results: Participants were 19 adults from the community with a 1 year history of non-penetrating traumatic brain injury (TBI) and were able to use computers. Seven had mild, 3 moderate and 9 severe TBIs. Mean score on the Boredom Proneness Scale (BPS): 107 (normal range 81–117); mean NSI:32; mean PPT 54 (normal range for assembly line workers >67). Responses to intervention: 3 (15%)subjects did not repeat all three trials of the tasks; 100% reported they were highly engaged in the interactions; 6 (30%) reported they had a high level of frustration with the tasks, but completed them with short breaks. Performance measures: Comparison of baseline to post training: TOOL time decreased by (mean) 60 sec; SPELL increased by 2.7 words; TUSE time decreased by (mean) 68 sec; and SAND time decreased by (mean) 72 sec. PPT correlated with TOOL (r=−0.65, p=0.016) and TUSE time (r=−0.6, p=0.014). SPELL correlated with Boredom score (r=0.41, p=0.08) and NSI (r=−.49, p=0.05). Conclusion: People with chronic TBI of various ages and severity report being engaged in using haptic devices that interact with 3D virtual environments. Haptic devices are able to capture objective data that provide useful information about fine motor and cognitive performance.

A comparison of three accelerometry-based devices for estimating energy expenditure in adults and children with cerebral palsy

JNER - Tue, 08/05/2014 - 00:00
Background: Advanced accelerometry-based devices have the potential to improve the measurement of everyday energy expenditure (EE) in people with cerebral palsy (CP). The aim of this study was to investigate the ability of two such devices (the Sensewear ProArmband and the Intelligent Device for Energy Expenditure and Activity) and the ability of a traditional accelerometer (the RT3) to estimate EE in adults and children with CP. Methods: Adults (n = 18; age 31.9 ± 9.5 yr) and children (n = 18; age 11.4 ± 3.2 yr) with CP (GMFCS levels I-III) participated in this study. Oxygen uptake, measured by the Oxycon Mobile portable indirect calorimeter, was converted into EE using Weir’s equation and used as the criterion measure. Participants’ EE was measured simultaneously with the indirect calorimeter and three accelerometers while they rested for 10 minutes in a supine position, walked overground at a maximal effort for 6 minutes, and completed four treadmill activities for 5 minutes each at speeds of 1.0 km.h−1, 1.0 km.h−1 at 5% incline, 2.0 km.h−1, and 4.0 km.h−1. Results: In adults the mean absolute percentage error was smallest for the IDEEA, ranging from 8.4% to 24.5% for individual activities (mean 16.3%). In children the mean absolute percentage error was smallest for the SWA, ranging from 0.9% to 23.0% for individual activities (mean 12.4%). Limits of agreement revealed that the RT3 provided the best agreement with the indirect calorimeter for adults and children. The upper and lower limits of agreement for adults were 3.18 kcal.min−1 (95% CI = 2.66 to 3.70 kcal.min−1) and -2.47 kcal.min−1 (95% CI = -1.95 to -3.00 kcal.min−1), respectively. For children, the upper and lower limits of agreement were 1.91 kcal.min−1 (1.64 to 2.19 kcal.min−1) and -0.92 kcal.min−1 (95% CI = -1.20 to -0.64 kcal.min−1) respectively. These limits of agreement represent -67.2% to 86.3% of mean EE for adults and -36.5% to 76.3% of mean EE for children, respectively. Conclusions: Although the RT3 provided the best agreement with the indirect calorimeter the RT3 could significantly overestimate or underestimate individual estimates of EE. The development of CP-specific algorithms may improve the ability of these devices to estimate EE in this population.

Altered regional homogeneity in experimentally induced low back pain: a resting-state fMRI study

JNER - Thu, 07/31/2014 - 00:00
Background: Functional imaging studies have indicated that patients with low back pain can have significant reductions in cerebral cortex grey matter. However, the mechanisms governing the nociceptive pathways in the human brain are unclear. The aim of this study was to use functional magnetic resonance imaging (fMRI) and regional homogeneity (ReHo) to investigate changes in resting-state brain activity in subjects that experienced experimentally induced low back pain. Methods: Healthy subjects (n = 15) underwent fMRI (3.0 T) at baseline and during painful stimulation (intramuscular injection of 3% hypertonic saline). Results: Compared to the scans conducted at baseline, scans conducted during experimentally induced low back pain showed increased ReHo on the right side in the medial prefrontal cortex, precuneus, insula, parahippocampal gyrus and cerebellum (posterior lobe), but decreased ReHo in the primary somatosensory cortex, anterior cingulate cortex and parahippocampal gyrus on the left side. The right inferior parietal lobule also showed a decreased ReHo (P < 0.05, cluster threshold ≥10). Conclusions: These findings suggest that abnormally spontaneous resting-state activity in some brain regions may be associated with pain processing. These changes in neural activity may contribute to the recognition, execution, memory and emotional processing of acute low back pain.

HIVE is supported by the European Commission under the Future and Emerging Technologies program.

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