Optimisation of hand posture stimulation using an electrode array and iterative learning control

Nonlinear optimisation-based search algorithms have been developed for the precise stimulation of muscles in the wrist and hand, to enable stroke patients to attain predefined gestures. These have been integrated in a system comprising a 40 element surface electrode array that is placed on the forearm, an electrogoniometer and data glove supplying position data from 16 joint angles, and custom signal generation and switching hardware to route the electrical stimulation to individual array elements. The technology will be integrated in a upper limb rehabilitation system currently undergoing clinical trials to increase their ability to perform functional tasks requiring fine hand and finger movement. Initial performance results from unimpaired subjects show the successful reproduction of six reference hand postures using the system.

Feedback control of the forearm movement of tetraplegic patient based on microsoft kinect and multi-pad electrodes

We present a novel system for control of elbow movements by electrical stimulation of the biceps and triceps in tetraplegic patients. The operation of the system uses the novel algorithm and applies closed loop control. Movement of the arm is generated via multi-pad electrodes developed by Tecnalia Serbia, Ltd. by the stimulator that allows asynchronous activation of individual pads. The electrodes are positioned over the innervation of the biceps and triceps muscles on the upper arm. This layout allows distributed activation; thereby, selective and low fatiguing activation of paralyzed muscles. The sensory feedback comes from the image acquired by the Microsoft Kinect system and the depth stream analysis is performed in real time by the computer running in the MatLab environment. The image based feedback allows control of the hand position at the target by cocontraction of the antagonists. The control adjusts the stimulation intensity and results with the tracking of the desired movement. The algorithm was proven to operate efficiently in a tetraplegic patient.

Closed-loop control of ankle plantarflexors and dorsiflexors using an inverted pendulum apparatus: A pilot study

Considerable demand exists for a device to facilitate hands-free, stable stance in individuals with neurological disorders such as spinal cord injury (SCI) and stroke. In this regard, applying functional electrical stimulation (FES) to muscles of the lower limbs in closed loop has shown promise. In particular, it has been suggested that a PID control strategy could offer functional benefits to stability by mimicking the neurological control strategy employed in able-bodied stance. In this proof of concept study, we tested this assertion by examining the potential of a PID control strategy with gravity compensation to effectively maintain balance during quiet stance by regulating FES-induced contractions of the ankle plantarflexors and dorsiflexors in able-bodied individuals. A novel Inverted Pendulum Standing Apparatus (IPSA) was employed to simulate quiet stance whilst minimizing the voluntary control of able-bodied subjects. Quiet and perturbed standing trials were performed in 3 able-bodied subjects. Performance metrics including those pertaining to stability during quiet stance (root mean square difference), perturbation rejection capabilities (settling time, peak deviation), and ability to transition from an offset initial position (settling time), were examined. For all 3 subjects and for all of the metrics examined, our results showed that the proposed closed-loop controlled FES system improved performance in comparison to voluntary control. These results indicate that the PID plus gravity control strategy used in this study offers meaningful benefits over voluntary control in terms of standing stability. Thus, the controller could potentially be applied to the problem of improving or restoring standing ability in some neurologic patient populations.

The modified drawing test for assessment of arm movement quality

The cerebrovascular accident often results in motor impairment of one of the upper limbs, hence, compromising the quality of life of stroke survivors. Rehabilitation aims to restore the movement abilities of the paralyzed/paretic upper limb. An important element in rehabilitation is to apply a quantified measure of the quality of movement, in order to follow the recovery and select the most appropriate therapeutic modality. We developed a method that uses data recorded during planar movements and outputs an objective measure that relates to the smoothness, velocity and precision of the movement. This method is universal, in a sense that hand position can be recorded by any available means (e.g., robot assistant, digitizing board, motion tracking systems, etc). The method follows the Drawing Test, but generates results that show the ability of the patient to make point to point movements and track the presented trajectory. The method is based on measurements of hand position during movement along a target path in form of a 2 cm wide rectangle. The patient?s task is to move the hand along the target path as quickly as possible, with as few contacts (collisions) with the sides of the path. This paper addresses the aspects of automatic detection of parameters that quantify the quality of movement (speed, smoothness and precision). The use of this method is presented with 10 patients.

Volitional cycling augmented by functional electrical stimulation in hemiparetic adolescents: A case series study

The aim of this work was to assess the feasibility of a treatment based on volitional cycling augmented by Functional Electrical Stimulation (FES) on hemiparetic adolescents. Six chronic hemiparetic adolescents were included in a case series study. Patients underwent FES-cycling training combined with voluntary pedaling. The intervention consisted of 21 sessions lasting 30 minutes each. Patients were evaluated before, after training, and at a 3-month follow-up visit through clinical scales (Winter scale, observational gait scale, gross motor function measurement, Boyd test and Ashworth scale), a standard gait analysis and a voluntary pedaling test. Results were compared with an age-matched healthy control group (N=6). Two subjects withdrew the study before the completion of the intervention. Concerning the four remaining subjects, the clinical scales showed a slight level of disability already at baseline and no changes were observed after the intervention. In terms of walking ability, some significant improvements (Kruskal-Wallis test, p-value<0.05) were obtained after training in two out of four subjects: an increase of about 16% and 41% of the ankle range of motion and of about 18% and 33% of the ankle propelling power were achieved for two subjects, respectively. During pedaling, the work produced by the paretic leg while pulling the pedal significantly increased in 3 out of 4 subjects. In one subject a more symmetrical cycling movement was observed, whilst for another subject a significant improvement in terms of co-contraction between rectus femoris and biceps femoris was achieved. In conclusion, this study assessed the feasibility of FES-cycling training on hemiparetic adolescents, but did not provide evidences about the effectiveness of this intervention in improving motor recovery and walking ability. However, since only a small group of patients with a low level of disability was involved in the study, further investigations are needed to provide conclusive results.

Walking with functional electrical stimulation and unlocking braces in thoracic-level paraplegia

Walking was tested in 4 people with thoracic-level paraplegia using stimulation of quadriceps muscles, the flexor reflex and unlocking knee-ankle-foot orthoses (KAFO). Heart rate, speed, distance, kinematics and ground reaction forces were measured while subjects walked using a walker. None of the subjects could walk without the system; all could walk continuously for at least 4 minutes with it. Joint angles and some other kinematic features resembled normal walking, but the walking was too slow (average speed: 3.8 m/min.) and too demanding (heart rate: 128 b/min; physiological cost index: 15 b/m) to be practical. Subjects supported about 1/3 of their weight with their arms during stance and about 2/3 during swing. Our results suggest that the braces reduced the effort needed and that the low speeds were due to both a lack of power at push-off and the time needed to stabilize the hip and trunk. The high heart rates arose from excessive contraction of the arm and trunk muscles for balance and propulsion.

A comparison of customized strategies to manage muscle fatigue in isometric artificially elicited muscle contractions for incomplete SCI subjects

Muscle fatigue due to functional electrical stimulation still prevents its widespread use as a gait rehabilitation tool for spinal cord injured subjects. Although there is an active research towards optimization of pulse parameters to delay muscle fatigue, changes in stimulated muscle's performance during repeated contractions due to fatigue have not been yet determined. In this work, a study conducted in two phases with a sample of incomplete spinal cord injured patients is presented. In the first phase, a fatigue protocol based on submaximal isometric contractions allowed to obtain an objective criterion for estimation of fatigue of knee muscles from initial changes in muscle performance. The criterion is incorporated in the fatigue protocol in the second phase of the study, to compare two novel customized fatigue management strategies. Results showed that knee flexor muscles develop less force and lower fatigue than extensor muscles. Muscle fatigue management strategies based on customized modulations of stimulation frequency are valid to delay muscle fatigue.

Electrical stimulation of the forearm: A method for transmitting sensory signals from the artificial hand to the brain

This research is in line with an important comment from the first amputee who tried the prosthetic hand with tactile feedback developed within the Smarthand project [1]. While trying the system with tactile feedback the patient said: "It's a feeling I have not had in a long time. When I grab something tightly I can feel it in the fingertips. It's strange since I don't have them anymore! It's amazing." We describe here the instrumentation and methods for testing the abilities of humans to discriminate sensations generated by electrical stimulation applied to the skin on the forearm. The instruments allowed testing of electrical stimulation with various properties (pulse duration, intensity, and rate). We tested the perception and pain thresholds, with the emphasis that comfortable sensations are a must. During the tests subjects were asked to locate the point on the skin that was stimulated and describe their perception of the elicited sensation. Results of first tests with small concentric electrodes suggest that non-amputees can distinguish up to seven perceptual qualities (the most common one was vibration, followed by tingling and tickling). Certain sensations had a higher occurrence rate along one axial line of the forearm than another of the forearm. In terms of spatial acuity, the subjects had more difficulties in distinguishing between the positions in the axial direction of the forearm compared with the circumferential direction. These results guided the design of the new array electrode with multiple cathodes and anodes positioned circumferential to the forearm. The results of the tests conducted with this electrode design showed high location discernment accuracy, and demonstrated the ability to memorize and later accurately recall six different electrical ?messages? created by delivering electrical stimulation onto three different electrode pads with two different stimulation parameters.

Comparison of TMS-induced arm activation and upper limb functional tests in hemiparetic stroke

Stroke has a major impact in the total cost of healthcare in the Western world as stroke is the most common cause of long-term disability [1]. In attempts to enhance motor recovery after stroke effective treatment strategies have been developed in recent years. Appropriate evaluation of the intervention programs requires comprehensive and accurate assessment of the residual abnormal function. In the present study we compare two well-known clinical functional scoring tests developed for the assessment of hemiparetic upper limb function due to stroke and navigated transcranial magnetic stimulation (nTMS), which measures involuntary target muscle response to cortical stimulation. The aim is to investigate the equivalence of these methods and thus add objective evidence of the limb function to strengthen evidence-based practice. In addition to functional tests, four muscles of both arms were studied in twenty chronic stroke patients. Those patients without motor evoked potentials (MEP) to nTMS in the affected upper limb had significantly lower total score in Action Research Arm Test and Wolf Motor Function Test and longer performance time than those patients with MEP. Patients, in whom MEP in each of the four target muscles was elicitable, had better than average scores in clinical functional tests while patients, in whom no MEP was elicitable in any target muscle, had worse than average scores. Transcranial magnetic stimulation adds crucial information when clinical assessment based on voluntary activation by command is challenging, e.g. in patients suffering from cognitive deficits.

New algorithm for packet routing in mobile ad-hoc networks

Mobile ad-hoc networks (MANET) are one of wireless networks implementation. MANET is very popular technology initially based on military purposes. Specific modifications of MANET created a possibility to implement several new wireless networks. One of them is a wireless mesh network (WMN). Over the last ten years, WMNs have gained more and more attention and are now considered as a convincing solution for providing better Internet access services for end users. WMN is an emerging technology that offers a cost-effective and scalable method to connect wireless devices. The main problem in WMNs is a routing protocol, especially because it has to enable the access to network for both mesh and conventional clients. Most of the existing ad hoc routing protocols use minimum hop-count as a metric for identifying the best packet routes. This paper presents neural network based approach to routing protocol for WMN. Neural networks are capable to analyze very complex network environments and solve routing problems on optimal (or almost optimal) way.