Andrej M. Savić

Surface‐distributed low‐frequency asynchronous stimulation delays fatigue of stimulated muscles

Introduction: One important reason why functional electrical stimulation (FES) has not gained widespread clinical use is the limitation imposed by rapid muscle fatigue due to non‐physiological activation of the stimulated muscles. We aimed to show that asynchronous low‐pulse‐rate (LPR) electrical stimulation applied by multipad surface electrodes greatly postpones the occurrence of muscle fatigue compared with conventional stimulation (high pulse rate, HPR). Methods: We compared the produced force vs. time of the forearm muscles responsible for finger flexion in 2 stimulation protocols, LPR (fL = 10 Hz) and HPR (fH = 40 Hz). Results: Surface‐distributed low‐frequency asynchronous stimulation (sDLFAS) doubles the time interval before the onset of fatigue (104 ± 80%) compared with conventional synchronous stimulation. Conclusions: Combining the performance of multipad electrodes (increased selectivity and facilitated positioning) with sDLFAS (decreased fatigue) can improve many FES applications in both the lower and upper extremities. Muscle Nerve 48: 930–937, 2013

Toward a Hybrid BCI for Grasp Rehabilitation

We present a feasibility study of hybrid brain- computer interface (BCI) for control of Functional Electrical stimulation (FES) during grasp rehabilitation. Proposed BCI operates in two stages sequentially. First stage is a steady-state visual evoked potential (SSVEP) based method for selection of one of the three objects for grasping. Second stage is event- related desynchronisation (ERD) based detection of the onset of reach-to-grasp selected object. In the first stage, adequate stimulation pattern for selected object is determined, while the second stage triggers FES to assist desired grasp. Mean detec- tion accuracies of SSVEP based selection and ERD based detection of the onset of movement for three subjects tested were 98.1% and 100% respectively. Obtained results suggest that this approach could be tested for the control of FES dur- ing Functional Electrical Therapy (FET). Hybrid BCI system is by definition composed of multiple BCIs or of a BCI and another system (13). We propose a hybrid system that combines one SSVEP based BCI for automatic selection of the grasping strategy and event- related desynchronisation (ERD) based BCI for triggering of FES. This hybrid BCI operates sequentially in two stag- es, Fig. 1. In the first stage system runs as an object for grasp selector. By object selection, type of grasp i.e. stimu- lation pattern is identified. This selection is based on detec- tion of SSVEP in the users EEG from the visual cortex. SSVEPs can be evoked by focused visual attention on one of the objects equipped with flashing light sources of differ- ent frequencies. Three SSVEP frequencies are chosen to serve as indicators for three basic grasps: palmar, lateral and precision grasp. In the second stage after the adequate FES pattern has been identified, system waits for information on the onset of reaching movement towards selected object. This information can be extracted from ERD of EEG signal (14).

Balloons and bavoons versus spikes and shikes: ERPs reveal shared neural processes for shape-sound-meaning congruence in words, and shape-sound congruence in pseudowords.

There is something about the sound of a pseudoword like takete that goes better with a spiky, than a curvy shape (Köhler, 1929:1947). Yet despite decades of research into sound symbolism, the role of this effect on real words in the lexicons of natural languages remains controversial. We report one behavioural and one ERP study investigating whether sound symbolism is active during normal language processing for real words in a speakers native language, in the same way as for novel word forms. The results indicate that sound-symbolic congruence has a number of influences on natural language processing: Written forms presented in a congruent visual context generate more errors during lexical access, as well as a chain of differences in the ERP. These effects have a very early onset (40-80 ms, 100-160 ms, 280-320 ms) and are later overshadowed by familiar types of semantic processing, indicating that sound symbolism represents an early sensory-co-activation effect.

ArmAssist Robotic System versus Matched Conventional Therapy for Poststroke Upper Limb Rehabilitation: A Randomized Clinical Trial

The ArmAssist is a simple low-cost robotic system for upper limb motor training that combines known benefits of repetitive task-oriented training, greater intensity of practice, and less dependence on therapist assistance. The aim of this preliminary study was to compare the efficacy of ArmAssist (AA) robotic training against matched conventional arm training in subacute stroke subjects with moderate-to-severe upper limb impairment. Twenty-six subjects were enrolled within 3 months of stroke and randomly assigned to the AA group or Control group (n = 13 each). Both groups were trained 5 days per week for 3 weeks. The primary outcome measure was Fugl-Meyer Assessment-Upper Extremity (FMA-UE) motor score, and the secondary outcomes were Wolf Motor Function Test-Functional Ability Scale (WMFT-FAS) and Barthel index (BI). The AA group, in comparison to the Control group, showed significantly greater increases in FMA-UE score (18.0 ± 9.4 versus 7.5 ± 5.5, p = 0.002) and WMFT-FAS score (14.1 ± 7.9 versus 6.7 ± 7.8, p = 0.025) after 3 weeks of treatment, whereas the increase in BI was not significant (21.2 ± 24.8 versus 13.1 ± 10.7, p = 0.292). There were no adverse events. We conclude that arm training using the AA robotic device is safe and able to reduce motor deficits more effectively than matched conventional arm training in subacute phase of stroke. The study has been registered at the ClinicalTrials.gov, ID: NCT02729649.

Movement Related Cortical Potentials and Sensory Motor Rhythms during Self Initiated and Cued Movements

In this study we have explored the two EEG phenomena that accompany movement preparation and execution: movement related cortical potentials (MRCP) and event-related desynchronization/synchronization (ERD/ERS). The experiments comprised the two conditions for motor task initiation, self paced and cued. The aim of the study was to explore how the introduction of the cue influences the morphological features of the MRCP and ERD/ERS curves. Preliminary results of the tests in 9 healthy subjects showed statistically significant differences in MRCP components for the two conditions and no significant differences in ERD/ERS morphology. Brain-Computer Interface algorithms for online control of assistive devices for restoration of movement may benefit from these results.

Motor Imagery Driven BCI with Cue-Based Selection of FES Induced Grasps

We present a BCI supported assistive system that comprises selective Functional Electrical Stimulation (FES) driven by subject’s motor imagery (MI). BCI control is based on subjects’ ability to voluntarily modulate their EEG sensory- motor rhythms. Event-related desynchronisation (ERD) of the alphoid mu rhythm is used for on-line detection of subjects’ execution of MI task. Current BCI-FES system can induce three types of grasp, palmar, lateral and precision. Cue-based brain switch is used to trigger the predefined FES pattern for each grasping type. System was tested on 4 healthy subjects who gained control over the BCI with mean accuracy of 88.8%.

Long-term physical activity modulates brain processing of somatosensory stimuli: Evidence from young male twins

Leisure-time physical activity is a key contributor to physical and mental health. Yet the role of physical activity in modulating cortical function is poorly known. We investigated whether precognitive sensory brain functions are associated with the level of physical activity. Physical activity history (3-yr-LTMET), physiological measures and somatosensory mismatch response (sMMR) in EEG were recorded in 32 young healthy twins. In all participants, 3-yr-LTMET correlated negatively with body fat%, r=-0.77 and positively with VO2max, r=0.82. The fat% and VO2max differed between 15 physically active and 17 inactive participants. Trend toward larger sMMR was seen in inactive compared to active participants. This finding was significant in a pairwise comparison of 9 monozygotic twin pairs discordant for physical activity. Larger sMMR reflecting stronger synchronous neural activity may reveal diminished gating of precognitive somatosensory information in physically inactive healthy young men compared to the active ones possibly rendering them more vulnerable to somatosensory distractions from their surroundings.

Numerical simulation of iontophoresis in the drug delivery system

Abstract The architecture and composition of stratum corneum act as barriers and limit the diffusion of most drug molecules and ions. Much effort has been made to overcome this barrier and it can be seen that iontophoresis has shown a good effect. Iontophoresis represents the application of low electrical potential to increase the transport of drugs into and across the skin or tissue. Iontophoresis is a noninvasive drug delivery system, and therefore, it is a useful alternative to drug transportation by injection. In this study, we present a numerical model and effects of electrical potential on the drug diffusion in the buccal tissue and the stratum corneum. The initial numerical results are in good comparison with experimental observation. We demonstrate that the application of an applied voltage can greatly improve the efficacy of localized drug delivery as compared to diffusion alone.

Validating ArmAssist Assessment as outcome measure in upper-limb post-stroke telerehabilitation.

The ArmAssist is a low-cost robotic system for post-stroke upper-limb telerehabilitation based on serious games. The system incorporates a set of games for the assessment of arm function, the ArmAssist Assessment (AAA), which allows a remote monitoring of the progress of the patient and an automatic adaptation of the therapy. In this study, different components of the AAA are compared against three widely-used clinical tests, the Fugl-Meyer Assessment (FMA) [1], the Action Research Arm Test (ARAT) [2] and the Wolf Motor Function Test (WMFT) [3] in order to select the most clinically meaningful ones for the final score provided to patients and therapist, and evaluate their capability to predict or even improve some aspects of these standard scales. All four tests were performed in 38 separate sessions in 19 post-stroke individuals in their sub-acute phase, as part of a broader study. Statistically significant correlation could be shown with the three clinical tests. These preliminary results are promising for the validation of AAA as a fast, automatic and clinically meaningful tool for remote progress assessment and therapy adaptation; however, more data and further analysis is needed to confirm this.

Post-stroke Robotic Upper-Limb Telerehabilitation Using Serious Games to Increase Patient Motivation: First Results from ArmAssist System Clinical Trial

Research findings indicate that intensive therapy is essential for achieving better outcome in post-stroke rehabilitation. However, with the increasing number of stroke patients and limited healthcare resources, it is difficult to provide the needed amount of therapy. Robot-assisted rehabilitation based on serious games may offer the solution for providing a more autonomous and scalable training that can be transferred out of the clinic and into home environments. Robots offer precision and repeatability of movements that can be used to provide safe and intensive rehabilitation exercises, both at home and in the clinic. Serious games can provide an enjoyable and effective way to motivate patients to increase both the quality and quantity of therapy. In addition, these technologies can also be used to remotely assess the motor performance of patients and the therapy progress. The ArmAssist is a recent example of a low-cost robotic system designed specifically for post-stroke upper-limb telerehabilitation. The system incorporates a set of serious games for assessment and training, further described in this paper. Preliminary results from the ongoing clinical study reveal very positive responses from 10 patients and 2 therapists about the usability and integration of the system in the clinical setting. Training with this system is shown to be beneficial and enjoyable, and highly motivates patients to continue and endure longer durations of training. More data and analysis is required to extract further conclusions.