Dynamics of movement-related cortical potentials and sensorimotor oscillations during palmar grasp movements.

Movement-related cortical potentials (MRCP) and sensorimotor oscillatory electroencephalographic (EEG) activity (event-related desynchronization/synchronization-ERD/ERS) provide complementary information of the associated motor activity. The aim of this study was to provide comparative spatio-temporal analysis of both EEG phenomena associated with palmar grasping motions including hand opening and closing phases. Nine healthy participants were instructed to perform self-paced, right hand grasping movements. EEG was recorded from 28 sites synchronous with electromyography (EMG) of wrist/fingers extensors and flexors. Statistical analysis of the EEG data revealed significant differences (p < .05) between the idle state (baseline) and motor preparation/execution periods in majority of recorded channels. The earliest statistical significance in MRCPs was observed for channel FC3 at -460.9 ms, while the earliest significant ERD was observed at 164.1 ms for channel C3. MRCP and ERD/ERS topographies in our study are in line with the results of previous studies comparing MRCP and ERD/ERS spatio-temporal patterns during upper limb movements, however, results of our study show that MRCP significant differences compared to the baseline appear in most channels earlier than ERD (on average 613.6 ± 191.5 ms earlier). This implies an advantage of MRCP signals for grasping movements' prediction, which is in contrast to previous reports. Moreover, combined spatio-temporal information on MRCP and ERD/ERS presented in this paper may serve for future optimization of grasp movement prediction/detection hybrid algorithms in the context of restorative brain-computer interface technology.

Validation of computerized square-drawing based evaluation of motor function in patients with stroke.

Human-administered clinical scales are commonly used for quantifying motor performance and determining the course of therapy in post-stroke individuals. Computerized methods aim to improve consistency, resolution and duration of patients' evaluation. The objective of this study was to test the validity of computerized square-drawing test (DT) for assessment of shoulder and elbow function by using novel set of DT-based kinematic measures and explore their relation with Wolf Motor Function Test (WMFT) scoring. Forty-seven stroke survivors were tested before and after the rehabilitation program. DT involved drawing a square in horizontal plane using a mechanical manipulandum and a digitizing board. Depending on the initial classification of patients into low or high performance groups, the two different outcome metrics were derived from DT kinematic data for evaluation of each group. Linear regression models applied to map DT outcome values to WMFT scores for both groups resulted with high correlation coefficients and low mean absolute prediction error. In conclusion, we have identified a set of kinematic measures suitable for fast and objective motor function evaluation and functional classification, strongly correlating with WMFT score in post-stroke individuals. The results support validation of square-drawing motor function assessment, encouraging its use in clinical settings.

An Expert System for Quantification of Bradykinesia Based on Wearable Inertial Sensors.

Wearable sensors and advanced algorithms can provide significant decision support for clinical practice. Currently, the motor symptoms of patients with neurological disorders are often visually observed and evaluated, which may result in rough and subjective quantification. Using small inertial wearable sensors, fine repetitive and clinically important movements can be captured and objectively evaluated. In this paper, a new methodology is designed for objective evaluation and automatic scoring of bradykinesia in repetitive finger-tapping movements for patients with idiopathic Parkinson's disease and atypical parkinsonism. The methodology comprises several simple and repeatable signal-processing techniques that are applied for the extraction of important movement features. The decision support system consists of simple rules designed to match universally defined criteria that are evaluated in clinical practice. The accuracy of the system is calculated based on the reference scores provided by two neurologists. The proposed expert system achieved an accuracy of 88.16% for files on which neurologists agreed with their scores. The introduced system is simple, repeatable, easy to implement, and can provide good assistance in clinical practice, providing a detailed analysis of finger-tapping performance and decision support for symptom evaluation.

Analysis of on-surface and in-air movement in handwriting of subjects with Parkinson's disease and atypical parkinsonism.

The purpose of this paper is to emphasize the importance of in-air movement besides on-surface movement for handwriting analysis. The proposed method uses a classification of drawing healthy subjects and subjects with Parkinson's disease, according to their on-surface and in-air handwriting parameters during their writing on a graphical tablet. Experimental results on real data sets demonstrate that the highest accuracy of subject's classification was obtained by combining both on-surface and in-air kinematic parameters.

Simple gastric motility assessment method with a single-channel electrogastrogram.

Surface electrogastrography (EGG) is a non-invasive technique that is used to record myoelectrical activity of the stomach using cutaneous electrodes placed on the abdomen. Gastric motility assessment by EGG is a candidate for standard clinical procedure based on the quantification of parameters characteristic of gastric motility disorders. Despite its noticeable benefits, EGG is not widely implemented in clinical practice. The main reasons are: (1) lack of standardization of electrode placement, (2) time-consuming diagnostic procedures and (3) a complex multi-channel recording setup. We proposed a methodology in which an easy-to-use single-channel EGG, with a less time-consuming protocol (<1 h), would provide sufficient information for gastric motility assessment. Recordings from the three anatomical landmarks in 20 healthy young subjects were compared under two conditions, fasting and postprandial by evaluating the dominant frequency (DF). Our results showed that there is a statistically significant increase of DF after meal ingestion (p<0.05) in each of the three channels. However, when the study group was divided into two subgroups based on body mass index (BMI), the most appropriate recording location was above the body of the stomach (according to statistical significance p=7.82×10-6). We showed that a less time-consuming recording session with light meal intake could be used for the assessment of gastric myoelectrical activity (GMA).

Challenges of Stride Segmentation and Their Implementation for Impaired Gait.

Stride segmentation represents important but challenging part of the gait analysis. Different methods and sensor systems have been proposed for detection of markers for segmentation of gait sequences. This task is often performed with wearable sensors comprising force sensors and/or inertial sensors. In this paper, we have compared four different methods for stride segmentation based on signals collected from force sensing resistors, accelerometers and gyro sensors. The results were evaluated on 15 healthy and 15 patients with Parkinson's disease, and expressed in terms of number of imprecisely, missed or wrongly detected gait events, as well as temporal absolute error. It was established that the methods using the inertial data, provide results with up to 12% higher error rate comparing to detection from force sensing resistors.

Design and test of a Microsoft Kinect-based system for delivering adaptive visual feedback to stroke patients during training of upper limb movement.

The present paper describes the design and test of a low-cost Microsoft Kinect-based system for delivering adaptive visual feedback to stroke patients during the execution of an upper limb exercise. Eleven sub-acute stroke patients with varying degrees of upper limb function were recruited. Each subject participated in a control session (repeated twice) and a feedback session (repeated twice). In each session, the subjects were presented with a rectangular pattern displayed on a vertical mounted monitor embedded in the table in front of the patient. The subjects were asked to move a marker inside the rectangular pattern by using their most affected hand. During the feedback session, the thickness of the rectangular pattern was changed according to the performance of the subject, and the color of the marker changed according to its position, thereby guiding the subject's movements. In the control session, the thickness of the rectangular pattern and the color of the marker did not change. The results showed that the movement similarity and smoothness was higher in the feedback session than in the control session while the duration of the movement was longer. The present study showed that adaptive visual feedback delivered by use of the Kinect sensor can increase the similarity and smoothness of upper limb movement in stroke patients.

Quantification of Finger-Tapping Angle Based on Wearable Sensors.

We propose a novel simple method for quantitative and qualitative finger-tapping assessment based on miniature inertial sensors (3D gyroscopes) placed on the thumb and index-finger. We propose a simplified description of the finger tapping by using a single angle, describing rotation around a dominant axis. The method was verified on twelve subjects, who performed various tapping tasks, mimicking impaired patterns. The obtained tapping angles were compared with results of a motion capture camera system, demonstrating excellent accuracy. The root-mean-square (RMS) error between the two sets of data is, on average, below 4°, and the intraclass correlation coefficient is, on average, greater than 0.972. Data obtained by the proposed method may be used together with scores from clinical tests to enable a better diagnostic. Along with hardware simplicity, this makes the proposed method a promising candidate for use in clinical practice. Furthermore, our definition of the tapping angle can be applied to all tapping assessment systems.

Finger tapping analysis in patients with Parkinson's disease and atypical parkinsonism.

The goal of this study was to investigate repetitive finger tapping patterns in patients with Parkinson's disease (PD), progressive supranuclear palsy-Richardson syndrome (PSP-R), or multiple system atrophy of parkinsonian type (MSA-P). The finger tapping performance was objectively assessed in PD (n=13), PSP-R (n=15), and MSA-P (n=14) patients and matched healthy controls (HC; n=14), using miniature inertial sensors positioned on the thumb and index finger, providing spatio-temporal kinematic parameters. The main finding was the lack or only minimal progressive reduction in amplitude during the finger tapping in PSP-R patients, similar to HC, but significantly different from the sequence effect (progressive decrement) in both PD and MSA-P patients. The mean negative amplitude slope of -0.12°/cycle revealed less progression of amplitude decrement even in comparison to HC (-0.21°/cycle, p=0.032), and particularly from PD (-0.56°/cycle, p=0.001), and MSA-P patients (-1.48°/cycle, p=0.003). No significant differences were found in the average finger separation amplitudes between PD, PSP-R and MSA-P patients (pmsa-pd=0.726, pmsa-psp=0.363, ppsp-pd=0.726). The lack of clinically significant sequence effect during finger tapping differentiated PSP-R from both PD and MSA-P patients, and might be specific for PSP-R. The finger tapping kinematic parameter of amplitude slope may be a neurophysiological marker able to differentiate particular forms of parkinsonism.

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 speaker's 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.

Quantitative and qualitative gait assessments in Parkinson's disease patients.

BACKGROUND/AIM: Postural impairments and gait disorders in Parkinson's disease (PD) affect limits of stability, impaire postural adjustment, and evoke poor responses to perturbation. In the later stage of the disease, some patients can suffer from episodic features such as freezing of gait (FOG). Objective gait assessment and monitoring progress of the disease can give clinicians and therapist important information about changes in gait pattern and potential gait deviations, in order to prevent concomitant falls. The aim of this study was to propose a method for identification of freezing episodes and gait disturbances in patients with PD. A wireless inertial sensor system can be used to provide follow-up of the treatment effects or progress of the disease. METHODS: The system is simple for mounting a subject, comfortable, simple for installing and recording, reliable and provides high-quality sensor data. A total of 12 patients were recorded and tested. Software calculates various gait parameters that could be estimated. User friendly visual tool provides information about changes in gait characteristics, either in a form of spectrogram or by observing spatiotemporal parameters. Based on these parameters, the algorithm performs classification of strides and identification of FOG types. RESULTS: The described stride classification was merged with an algorithm for stride reconstruction resulting in a useful graphical tool that allows clinicians to inspect and analyze subject's movements. CONCLUSION: The described gait assessment system can be used for detection and categorization of gait disturbances by applying rule-based classification based on stride length, stride time, and frequency of the shank segment movements. The method provides an valuable graphical interface which is easy to interpret and provides clinicians and therapists with valuable information regarding the temporal changes in gait.

Feasibility of a hybrid brain-computer interface for advanced functional electrical therapy.

We present a feasibility study of a novel hybrid brain-computer interface (BCI) system for advanced functional electrical therapy (FET) of grasp. FET procedure is improved with both automated stimulation pattern selection and stimulation triggering. The proposed hybrid BCI comprises the two BCI control signals: steady-state visual evoked potentials (SSVEP) and event-related desynchronization (ERD). The sequence of the two stages, SSVEP-BCI and ERD-BCI, runs in a closed-loop architecture. The first stage, SSVEP-BCI, acts as a selector of electrical stimulation pattern that corresponds to one of the three basic types of grasp: palmar, lateral, or precision. In the second stage, ERD-BCI operates as a brain switch which activates the stimulation pattern selected in the previous stage. The system was tested in 6 healthy subjects who were all able to control the device with accuracy in a range of 0.64-0.96. The results provided the reference data needed for the planned clinical study. This novel BCI may promote further restoration of the impaired motor function by closing the loop between the "will to move" and contingent temporally synchronized sensory feedback.

Automatic identification and classification of freezing of gait episodes in Parkinson's disease patients.

Alternation of walking pattern decreases quality of life and may result in falls and injuries. Freezing of gait (FOG) in Parkinson's disease (PD) patients occurs occasionally and intermittently, appearing in a random, inexplicable manner. In order to detect typical disturbances during walking, we designed an expert system for automatic classification of various gait patterns. The proposed method is based on processing of data obtained from an inertial sensor mounted on shank. The algorithm separates normal from abnormal gait using Pearson's correlation and describes each stride by duration, shank displacement, and spectral components. A rule-based data processing classifies strides as normal, short (short(+)) or very short (short(-)) strides, FOG with tremor (FOG(+)) or FOG with complete motor block (FOG(-)). The algorithm also distinguishes between straight and turning strides. In 12 PD patients, FOG(+) and FOG(-) were identified correctly in 100% of strides, while normal strides were recognized in 95% of cases. Short(+) and short(-) strides were identified in about 84% and 78%. Turning strides were correctly identified in 88% of cases. The proposed method may be used as an expert system for detailed stride classification, providing warning for severe FOG episodes and near-fall situations.

A method for assessing the arm movement performance: probability tube.

Quantification of motor performance is an important component of the rehabilitation of humans with sensory-motor disability. We developed a method for assessing arm movement performance of trainees (patients) termed "probability tube" (PT). PT captures the stochastic characteristics of a desired movement when repeated by an expert (therapist). The PT is being generated automatically from data recorded during point-to-point movement executed not more than 15 repetitions by the clinician and/or other non-expert programmer in just a few minutes. We introduce the index, termed probability tube score (PTS), as a single "goodness-of-fit" value allowing quantified analysis of the recovery and effects of the therapy. This index in fact scores the difference between the movement (velocity profile) executed by the trainee and the velocity profile of the desired movement (executed by the expert). We document the goodness of the automatic method with results from studies which included healthy subjects and show the use of the PTS in healthy and post-stroke hemiplegic subjects.

Control of robot assistant for rehabilitation of upper extremities.

The assisted movement in humans with paresis of upper extremities is becoming popular for neurorehabilitation. We propose a novel method for trajectory selection and assistance control. This paper presents simulation of a planar two degrees of freedom robot that assists horizontal movement of the hand. The control assumes that during the exercise the hand needs to follow healthy alike trajectories. The robot is assumed to provide minimal assistance and operate as a teacher of the movement.

Advances in the use of electrical stimulation for the recovery of motor function.

This chapter sheds light on several issues that are being explored to optimize the application of electrical stimulation in a motor neural prosthesis (MNP) for the restoration of movement in humans with paralysis. Although several MNPs are commercially available, there are issues that limit their use in therapy and/or daily assistance: (1) the users' intention of what and how to move needs to be effectively transmitted to the MNP controller; (2) interface to the neural pathways that leads to physiological-like activation should be improved; (3) artificial control of the MNP should match the biological control of the preserved biological systems; and (4) sensors information should be fused and provided to both the controller of the MNP and the user. We suggest that with the improved use of cortical or other physiological signals, application of multipad electrodes with special protocols, rule-based control that mimics biological control, and with the incorporation of micro- and nanotechnologies, wireless communications, and microcontrollers, the MNP operation can be greatly enhanced. The chapter specifically addresses the control of MNP for the upper extremities and provides details on the new surface multipad electrodes that are of interest for neurorehabilitation of stroke patients.

Electrical stimulation for the suppression of pathological tremor.

Pathological tremor is manifested as an involuntary oscillation of one or more body parts. Tremor greatly decreases the quality of life and often prevents the patient from performing daily activities. We hypothesized that sensors-driven multichannel electrical stimulation could stabilize affected joints by activating the antagonistic muscles during involuntary activation of agonist muscles and vice versa (out-of-phase stimulation). Here, we present the new system (hardware and software) and the testing of its operation. The hardware consists of a multichannel stimulator and inertial sensors for feedback. The software implements adaptive sensors-driven control for the out-of-phase stimulation. The system was initially applied to healthy persons at the wrist and elbow joints to test the efficiency of the hardware and software solutions. Predefined rhythmic stimulation resulted in tremulous movement, which subjects could not prevent; yet, they were still able to functionally use their hand. The system was then applied to seven patients with Parkinson's disease and essential tremor for minimization of the wrist joint tremor. In six patients, the adaptive out-of-phase stimulation resulted in a significant decrease in the amplitude of tremor (67 ± 13%). In one patient, the stimulation did not result in the expected reduction of tremor.

Influence of planar manipulandum to the hand trajectory during point to point movement.

We present the analysis of the planar manipulandum effects to the trajectory of point to point movements in horizontal plane. This analysis is of significance for the control of a haptic robot that can be used for the rehabilitation of hemiplegic patients. The effects were assessed by comparing data collected in experiments with healthy subjects when performing simple movements that are used in the therapy of stroke patients. We found significant differences between the preferred trajectories and the deviations from the preferred trajectories (p<0.01) when moving with and without the manipulandum. This result suggests that for the design of the controller of a robot assistant inertial properties of the robot mechanism must be considered even in the case that it is used only for the assessment (passive) or within the bio-feedback.

Learning arm/hand coordination with an altered visual input.

The focus of this study was to test a novel tool for the analysis of motor coordination with an altered visual input. The altered visual input was created using special glasses that presented the view as recorded by a video camera placed at various positions around the subject. The camera was positioned at a frontal (F), lateral (L), or top (T) position with respect to the subject. We studied the differences between the arm-end (wrist) trajectories while grasping an object between altered vision (F, L, and T conditions) and normal vision (N) in ten subjects. The outcome measures from the analysis were the trajectory errors, the movement parameters, and the time of execution. We found substantial trajectory errors and an increased execution time at the baseline of the study. We also found that trajectory errors decreased in all conditions after three days of practice with the altered vision in the F condition only for 20 minutes per day, suggesting that recalibration of the visual systems occurred relatively quickly. These results indicate that this recalibration occurs via movement training in an altered condition. The results also suggest that recalibration is more difficult to achieve for altered vision in the F and L conditions compared to the T condition. This study has direct implications on the design of new rehabilitation systems.