Journal of NeuroEngineering and Rehabilitation - Latest articles

Investigating the complexity of respiratory patterns during the laryngeal chemoreflex

Andrei Dragomir, Yasemin Akay, Aidan K Curran and Metin Akay — 2008-06-20

Background: The laryngeal chemoreflex exists in infants as a primary sensory mechanism for defending the airway from the aspiration of liquids. Previous studies have hypothesized that prolonged apnea associated with this reflex may be life threatening and might be a cause of sudden infant death syndrome. Methods: In this study we quantified the output of the respiratory neural network, the diaphragm EMG signal, during the laryngeal chemoreflex and eupnea in early postnatal (3-10 days) piglets. We tested the hypothesis that diaphragm EMG activity corresponding to reflex-related events involved in clearance (restorative) mechanisms such as cough and swallow exhibit lower complexity, suggesting that a synchronized homogeneous group of neurons in the central respiratory network are active during these events. Nonlinear dynamic analysis was performed using the approximate entropy to assess the complexity of respiratory patterns. Results: Diaphragm EMG, genioglossal activity EMG, as well as other physiological signals (tracheal pressure, blood pressure and respiratory volume) were recorded from 5 unanesthetized chronically instrumented intact piglets. Approximate entropy values of the EMG during cough and swallow were found significantly (p<0.05 and p<0.01 respectively) lower than those of eupneic EMG. Conclusions: Reduced complexity values of the respiratory neural network output corresponding to coughs and swallows suggest synchronous neural activity of a homogeneous group of neurons. The higher complexity values exhibited by eupneic respiratory activity are the result of a more random behaviour, which is the outcome of the integrated action of several groups of neurons involved in the respiratory neural network.

Gait characteristics of subjects with chronic fatigue syndrome and controls at self-selected and matched velocities

Lorna Paul, Danny Rafferty, Leslie Wood and William Maclaren — 2008-05-27

Background: Gait abnormalities have been reported in individuals with Chronic Fatigue Syndrome (CFS) however no studies exist to date investigating the kinematics of individuals with CFS in over-ground gait. The aim of this study was to compare the over-ground gait pattern (sagittal kinematics and temporal and spatial) of individuals with CFS and control subjects at their self-selected and at matched velocities. Methods: Twelve individuals with CFS and 12 matched controls participated in the study. Each subject walked along a 7.2 m walkway three times at each of three velocities: self-selected, relatively slow (0.45 ms-1) and a relatively fast (1.34 ms-1). A motion analysis system was used to investigate the sagittal plane joint kinematics and temporal spatial parameters of gait. Results: At self-selected velocity there were significant differences between the two groups for all the temporal and spatial parameters measured, including gait velocity (P = 0.002). For the kinematic variables the significant differences were related to both ankles during swing and the right ankle during stance. At the relatively slower velocity the kinematic differences were replicated. However, the step distances decreased in the CFS population for the temporal and spatial parameters. When the gait pattern of the individuals with CFS at the relatively fast walking velocity (1.30 ± 0.24 ms-1) was compared to the control subjects at their self-selected velocity (1.32 ± 0.15 ms-1) the gait pattern of the two groups was very similar, with the exception of both ankles during swing. Conclusion: The self-selected gait velocity and/or pattern of individuals with CFS may be used to monitor the disease process or evaluate therapeutic intervention. These differences may be a reflection of the relatively low self-selected gait velocity of individuals with CFS rather than a manifestation of the condition itself.

A haptic-robotic platform for upper-limb reaching stroke therapy: Preliminary design and evaluation results

2008-05-22

Background: It has been shown that intense training can significantly improve post-stroke upper-limb functionality. However, opportunities for stroke survivors to practice rehabilitation exercises can be limited because of the finite availability of therapists and equipment. This paper presents a haptic-enabled exercise platform intended to assist therapists and moderate-level stroke survivors perform upper-limb reaching motion therapy. This work extends on existing knowledge by presenting: 1) an anthropometrically-inspired design that maximizes elbow and shoulder range of motions during exercise; 2) an unobtrusive upper body postural sensing system; and 3) a vibratory elbow stimulation device to encourage muscle movement. Methods: A multi-disciplinary team of professionals were involved in identifying the rehabilitation needs of stroke survivors incorporating these into a prototype device. The prototype system consisted of an exercise device, postural sensors, and a elbow stimulation to encourage the reaching movement. Eight experienced physical and occupational therapists participated in a pilot study exploring the usability of the prototype. Each therapist attended two sessions of one hour each to test and evaluate the proposed system. Feedback about the device was obtained through an administered questionnaire and combined with quantitative data. Results: Seven of the nine questions regarding the haptic exercise device scored higher than 3.0 (somewhat good) out of 4.0 (good). The postural sensors detected 93 of 96 (97%) therapist-simulated abnormal postures and correctly ignored 90 of 96 (94%) of normal postures. The elbow stimulation device had a score lower than 2.5 (neutral) for all aspects that were surveyed, however the therapists felt the rehabilitation system was sufficient for use without the elbow stimulation device. Conclusion: All eight therapists felt the exercise platform could be a good tool to use in upper-limb rehabilitation as the prototype was considered to be generally well designed and capable of delivering reaching task therapy. The next stage of this project is to proceed to clinical trials with stroke patients.

Leg joint power output during progressive resistance FES-LCE cycling in SCI subjects: developing an index of fatigue

Stephenie A Haapala, Pouran D Faghri and Douglas J Adams — 2008-04-26

Background: The purpose of this study was to investigate the biomechanics of the hip, knee and ankle during a progressive resistance cycling protocol in an effort to detect and measure the presence of muscle fatigue. It was hypothesized that knee power output can be used as an indicator of fatigue in order to assess the cycling performance of SCI subjects. Methods: Six spinal cord injured subjects (2 incomplete, 4 complete) between the ages of twenty and fifty years old and possessing either a complete or incomplete spinal cord injury at or below the fourth cervical vertebra participated in this study. Kinematic data and pedal forces were recorded during cycling at increasing levels of resistance. Ankle, knee and hip power outputs and resultant pedal force were calculated. Ergometer cadence and muscle stimulation intensity were also recorded. Results: The main findings of this study were: (a) ankle and knee power outputs decreased, whereas hip power output increased with increasing resistance, (b) cadence, stimulation intensity and resultant pedal force in that combined order were significant predictors of knee power output and (c) knowing the value of these combined predictors at 10 rpm, an index of fatigue can be developed, quantitatively expressing the power capacity of the knee joint with respect to a baseline power level defined as fatigue. Conclusion: An index of fatigue was successfully developed, proportionalizing knee power capacity during cycling to a predetermined value of fatigue. The fatigue index value at 0/8th kp, measured 90 seconds into active, unassisted pedaling was 1.6. This indicates initial power capacity at the knee to be 1.6 times greater than fatigue. The fatigue index decreased to 1.1 at 2/8th kp, representing approximately a 30% decrease in the knee's power capacity within a 4 minute timespan. These findings suggest that the present cycling protocol is not sufficient for a rider to gain the benefits of FES and thus raises speculation as to whether or not progressive resistance cycling is an appropriate protocol for SCI subjects.

Effects of attention on the control of locomotion in individuals with chronic low back pain

2008-04-25

Background: People who suffer from low back pain (LBP) exhibit an abnormal gait pattern, characterized by shorter stride length, greater step width, and an impaired thorax-pelvis coordination which may undermine functional walking. As a result, gait in LBP may require stronger cognitive regulation compared to pain free subjects thereby affecting the degree of automaticity of gait control. Conversely, because chronic pain has a strong attentional component, diverting attention away from the pain might facilitate a more efficient walking pattern. Methods: Twelve individuals with LBP and fourteen controls participated. Subjects walked on a treadmill at comfortable speed, under varying conditions of attentional load: (a) no secondary task, (b) naming the colors of squares on a screen, (c) naming the colors of color words ("color Stroop task"), and (d) naming the colors of words depicting motor activities. Markers were attached to the thorax, pelvis and feet. Motion was recorded using a three-camera SIMI system with a sample frequency of 100 Hz. To examine the effects of health status and attention on gait, mean and variability of stride parameters were calculated. The coordination between thoracic and pelvic rotations was quantified through the mean and variability of the relative phase between those oscillations. Results: LBP sufferers had a lower walking speed, and consequently a smaller stride length and lower mean thorax-pelvis relative phase. Stride length variability was significantly lower in the LBP group but no significant effect of attention was observed. In both groups gait adaptations were found under performance of an attention demanding task, but significantly more so in individuals with LBP as indicated by an interaction effect on relative phase variability. Conclusion: Gait in LBP sufferers was characterized by less variable upper body movements. The diminished flexibility in trunk coordination was aggravated under the influence of an attention demanding task. This provides further evidence that individuals with LBP tighten their gait control, and this suggests a stronger cognitive regulation of gait coordination in LBP. These changes in gait coordination reduce the capability to deal with unexpected perturbations, and are therefore maladaptive.

Effects of an attention demanding task on dynamic stability during treadmill walking

Jonathan B Dingwell, Roland T Robb, Karen L Troy and Mark D Grabiner — 2008-04-21

Background: People exhibit increased difficulty balancing when they perform secondary attention-distracting tasks while walking. However, a previous study by Grabiner and Troy (J. Neuroengineering Rehabil., 2005) found that young healthy subjects performing a concurrent Stroop task while walking on a motorized treadmill exhibited decreased step width variability. However, measures of variability do not directly quantify how a system responds to perturbations. This study re-analyzed data from Grabiner and Troy 2005 to determine if performing the concurrent Stroop task directly affected the dynamic stability of walking in these same subjects. Methods: Thirteen healthy volunteers walked on a motorized treadmill at their self-selected constant speed for 10 minutes both while performing the Stroop test and during undisturbed walking. This Stroop test consisted of projecting images of the name of one color, printed in text of a different color, onto a wall and asking subjects to verbally identify the color of the text. Three-dimensional motions of a marker attached to the base of the neck (C5/T1) were recorded. Marker velocities were calculated over 3 equal intervals of 200 sec each in each direction. Mean variability was calculated for each time series as the average standard deviation across all strides. Both "local" and "orbital" dynamic stability were quantified for each time series using previously established methods. These measures directly quantify how quickly small perturbations grow or decay, either continuously in real time (local) or discretely from one cycle to the next (orbital). Differences between Stroop and Control trials were evaluated using a 2-factor repeated measures ANOVA. Results: Mean variability of trunk movements was significantly reduced during the Stroop tests compared to normal walking. Conversely, local and orbital stability results were mixed: some measures showed slight increases, while others showed slight decreases. In many cases, different subjects responded differently to the Stroop test. While some of our comparisons reached statistical significance, many did not. In general, measures of variability and dynamic stability reflected different properties of walking dynamics, consistent with previous findings. Conclusion: These findings demonstrate that the decreased movement variability associated with the Stroop task did not translate to greater dynamic stability.

Hypothesis testing for evaluating a multimodal pattern recognition framework applied to speaker detection

Patricia Besson and Murat Kunt — 2008-03-27

Background: Speaker detection is an important component of many human-computer interaction applications, like for example, multimedia indexing, or ambient intelligent systems. This work addresses the problem of detecting the current speaker in audio-visual sequences. The detector performs with few and simple material since a single camera and microphone meets the needs.MethodA multimodal pattern recognition framework is proposed, with solutions provided for each step of the process, namely, the feature generation and extraction steps, the classification, and the evaluation of the system performance. The decision is based on the estimation of the synchrony between the audio and the video signals. Prior to the classification, an information theoretic framework is applied to extract optimized audio features using video information. The classification step is then defined through a hypothesis testing framework in order to get confidence levels associated to the classifier outputs, allowing thereby an evaluation of the performance of the whole multimodal pattern recognition system. Results: Through the hypothesis testing approach, the classifier performance can be given as a ratio of detection to false-alarm probabilities. Above all, the hypothesis tests give means for measuring the whole pattern recognition process effciency. In particular, the gain offered by the proposed feature extraction step can be evaluated. As a result, it is shown that introducing such a feature extraction step increases the ability of the classifier to produce good relative instance scores, and therefore, the performance of the pattern recognition process. Conclusion: The powerful capacities of hypothesis tests as an evaluation tool are exploited to assess the performance of a multimodal pattern recognition process. In particular, the advantage of performing or not a feature extraction step prior to the classification is evaluated. Although the proposed framework is used here for detecting the speaker in audiovisual sequences, it could be applied to any other classification task involving two spatio-temporal co-occurring signals.

Human-machine interfaces based on EMG and EEG applied to robotic systems

2008-03-26

Background: Two different Human-Machine Interfaces (HMIs) were developed, both based on electro-biological signals. One is based on the EMG signal and the other is based on the EEG signal. Two major features of such interfaces are their relatively simple data acquisition and processing systems, which need just a few hardware and software resources, so that they are, computationally and financially speaking, low cost solutions. Both interfaces were applied to robotic systems, and their performances are analyzed here. The EMG-based HMI was tested in a mobile robot, while the EEG-based HMI was tested in a mobile robot and a robotic manipulator as well. Results: Experiments using the EMG-based HMI were carried out by eight individuals, who were asked to accomplish ten eye blinks with each eye, in order to test the eye blink detection algorithm. An average rightness rate of about 95% reached by individuals with the ability to blink both eyes allowed to conclude that the system could be used to command devices. Experiments with EEG consisted of inviting 25 people (some of them had suffered cases of meningitis and epilepsy) to test the system. All of them managed to deal with the HMI in only one training session. Most of them learnt how to use such HMI in less than 15 minutes. The minimum and maximum training times observed were 3 and 50 minutes, respectively. Conclusion: Such works are the initial parts of a system to help people with neuromotor diseases, including those with severe dysfunctions. The next steps are to convert a commercial wheelchair in an autonomous mobile vehicle; to implement the HMI onboard the autonomous wheelchair thus obtained to assist people with motor diseases, and to explore the potentiality of EEG signals, making the EEG-based HMI more robust and faster, aiming at using it to help individuals with severe motor dysfunctions.

A new measurement method for spine reposition sense

2008-03-26

Background: A cost effective tool for the measurement of trunk reposition sense is needed clinically. This study evaluates the reliability and validity of a new clinical spine reposition sense device. Methods: The first part of this three part investigation included 45 asymptomatic subjects examined in the first 20 repeated trials portion assessing spine reposition sense. The second portion, test-retest, examined 57 asymptomatic subjects. Initial testing consisted of subjects sitting on the device and performing 20 trials of a self-determined 2/3 trunk flexion position. The second portion of the study involved 7 trials of trunk flexion performed twice. The angular position for each trial was calculated and the mean reposition error from the initial 2/3 position was determined. For the third portion, the new device was compared to the Skill Technologies 6D (ST6D) Imperial Motion Capture and Analysis System. Results: ICC (3,1) for trials 4–7 was 0.79 and 0.76 for time one and time two, respectively and the test-retest ICC (3,k) was 0.38. Due to the poor test-retest ICC, the Bland Altman method was used to compare test and retest absolute errors. Most measurement differences were small and fell within the 95% confidence interval. Comparable measures between the two methods were found using the Bland Altman method to compare the reposition sense device to the ST6D system. Conclusion: The device may be a cost effective clinical technique for sagittal trunk reposition sense measurement.

Efficacy of motor imagery in post-stroke rehabilitation: a systematic review

2008-03-14

Background: Evaluation of how Motor Imagery and conventional therapy (physiotherapy or occupational therapy) compare to conventional therapy only in their effects on clinically relevant outcomes during rehabilitation of persons with stroke.DesignSystematic review of the literature Methods: We conducted an electronic database search in seven databases in August 2005 and also hand-searched the bibliographies of studies that we selected for the review.Two reviewers independently screened and selected all randomized controlled trials that compare the effects of conventional therapy plus Motor Imagery to those of only conventional therapy on stroke patients.The outcome measurements were: Fugl-Meyer Stroke Assessment upper extremity score (66 points) and Action Research Arm Test upper extremity score (57 points).Due to the high variability in the outcomes, we could not pool the data statistically. Results: We identified four randomized controlled trials from Asia and North America. The quality of the included studies was poor to moderate. Two different Motor imagery techniques were used (three studies used audiotapes and one study had occupational therapists apply the intervention). Two studies found significant effects of Motor Imagery in the Fugl-Meyer Stroke Assessment: Differences between groups amounted to 11.0 (1.0 to 21.0) and 3.2 (-4 to 10.3) respectively and in the Action Research Arm Test 6.1 (-6.2 to 18.4) and 15.8 (0.5 to 31.0) respectively. One study did not find a significant effect in the Fugl-Meyer Stroke Assessment and Color trail Test (p = 0.28) but in the task-related outcomes (p > 0.001). Conclusion: Current evidence suggests that Motor imagery provides additional benefits to conventional physiotherapy or occupational therapy. However, larger and methodologically sounder studies should be conducted to assess the benefits of Motor imagery.