Radim Krupicka

Gait symmetry measures: A review of current and prospective methods

Abstract Gait symmetry is important in measuring gait pattern alterations for establishing the level of functional limitation due to pathology, observing its changes over time and evaluating rehabilitative intervention effects. The aim of this topical review is twofold: 1) to present used symmetry measures and summarize their application to a diverse range of gait data and to demonstrate their capabilities in their utilization in research and practice, 2) to expose newly developed symmetry measures and highlight their perspectives. We divided symmetry measures into four subgroups: symmetry indices, complete gait cycle symmetry measures, statistically-based measures and approaches, and nonlinear measures. For each, we will discuss their advantages and limitations and raise new questions and recommendations about their development and clinical use.

Split-Belt Treadmill to Study Reactive Responses to Unexpected Gait Perturbation

The aim is to presents a solution and realization of the design of new split-belt treadmill for controlled, unexpected perturbation during walking to study recovery responses and dynamic stability of the human gait. The construction of the split-belt treadmill consists of several subsystems. The most important subsystems are: actuator, control and sensory subsystem. Actuator subsystem is based on two asynchronous motors, two inverters and two gears (for each belt separately). Control subsystem is made up of Modbus communications between the control computer and two inverters with respect to the parameters of the asynchronous motors. The sensory subsystem is based on the incremental angular speed sensor used to record the behavior of the treadmill belts. The control itself is created through the MatLab software and special custom-made user interface that allows to define a wide range of perturbation schemes. It was then verified whether the belts had the desired speed. Verification of the system has shown that at the recommended speeds of running the belts (at 2.4 km/h), the system is stable, shows no variations in proband load, and real changes in belt velocities are achieved with minimum deviations from the desired values. The main benefit of the described work is the creation of a functional control of the prototype of the treadmill for controlled, mechanical gait perturbations. The split-belt treadmill is designed to study reactive responses during walking that can be further used to fall-risk assessment, clinical or rehabilitation intervention.

Wave Kurtosis: A Novel, Specific Parameter for TUG-Turn Quantification

The Timed Up and Go test (TUG) is widely used in both research and clinical settings. The most common parameter for quantification of functional decline is the duration of a performed TUG. Analysis of the turn part of the TUG could provide valuable information about functional decline. Notwithstanding, there are only a few studies that deals with the TUG turn processing. This study proposes a novelty parameter—wave kurtosis (WK) that provides quantitative metrics for describing and comparing turn patterns. The WK is designed to evaluate the shape of the signal waveform. The WK quantifies the peak of the signal, its position and tails. The TUG-turn angular rate was analysed. Intra-class correlations (ICC) of WK and the strength of a linear association between WK and established turn parameters (turn duration, peak angular rate, and mean angular rate) were calculated. The reliability of WK about the vertical axis was moderate (ICC > 0.50), while reliabilities of the frontal axis and sagittal axis varied according to the subject group. The WK about the vertical axis was moderately correlated with turn duration, mean value and peak value. Utilization of waveform parameters opens a new area of TUG turn analysis and may allow for a more sensitive determination of movement disorders or fall risk assessment. Therefore, future studies utilizing turn movement may benefit from the use of the wave kurtosis.

Automated Neurons Recognition and Sorting for Diamond Based Microelectrode Arrays Recording: A Feasibility Study

Microelectrode arrays (MEA) are extensively used for recording and stimulating neural activity in vitro and in vivo. Depositing nanostructured boron doped diamond (BDD) onto the neuroelectrodes makes it possible to obtain dual mode low-noise neuroelectrical and neurochemical information simultaneously. The signal processing procedure requires finding and distinguishing individual neurons spikes in the recordings. Spike identification is usually done manually which is inaccurate and inappropriate for complex datasets. In this paper, we present a methodology and two algorithms for neurons recognition and evaluation based on unsupervised learning. Forty-five extracellular randomly selected signals from 26 unique measurements of embryonic hippocampal rat neurons (20 kHz, 6 min) were recorded on the commercial 60 TiN channels MEA. The signals were filtered in the 300–3000 Hz band and an amplitude detector (4x std of the background noise) was used for spike detection. WaveClus features were computed and its 3 PCA components were extracted for every spike. The optimal number of clusters were evaluated by an expert rater. K-means + gap criterion (alg. 1) and the Gaussian Mixture Model + Bayesian Information Criterion (alg. 2) were implemented and compared. The total IntraClass Correlation showed a significant inter-rater agreement for all 3 rater procedures (ICC = 0.69, p < 0.001), when post hoc weighted Cohen’s Kappas for 2 raters were 0.85 (expert vs. alg. 1; p < 0.001) and 0.62 (expert vs. alg. 2; p < 0.001). This will contribute to the objective definition of dual mode BDD MEA performance criteria and for a comparison with the current system.

System for Motor Evoked Potentials Acquisition and Analysis

Biological signal acquisition is a fundamental part of the following signal processing methods. This study is focused on hardware and software solution for an electrophysiological measurement in neurological patients and healthy controls. This paper deals with a design and an implementation of the system for transcranial magnetic stimulation (TMS) applied over the human motor cortex, which has the diagnostic and potential therapeutic effect, respectively. The system was successfully used for examinations of 22 neurological patients (mean age 51 ± (SD) 17 years) suffering from dystonia of various distribution and etiology treated by chronic deep brain stimulation of globus pallidus interna (GPi DBS). Established values of the motor-evoked potential’s (MEP) parameters are in line with the current literature. Designed system for TMS examination is an effective tool for studying the pathophysiology of neurological diseases.

A New Approach to Gait Variability Quantification using Cyclograms.

Human gait is cyclic movement and its properties are not constant. Gait variability is widely assessed by fluctuation in spatio-temporal parameters. Since this method operate on a single parameter of the gait cycle, the cycle signal in its entirety does not affect the result. The objective of this work is to present new gait variability assessment method. In order to quantify the variability of entire gait cycle, we have proposed and tested the method based on synchronized cyclograms. The novel approach showed the ability to assess gait variability. The method is not restricted to gait variability assessment and would be beneficial in different areas of cyclic movement variability analysis.

P 056 - The effect of medication on walking turns in Parkinson disease

More than half of Parkinsons disease patients (PD) report difficulty in turning. We observed different numbers of turn steps, turn times, turn types, and turn qualities in PD patients compared to healthy adults. Although medication has an effect on motor impairments in PD, its effect on the complex walking turn task is still unclear. The aim of this paper is to investigate the effect of medication on the walking turn. All subjects performed an instrumented extended Timed Up & Go Test (TUG) wearing gyro-accelerometers. The PD patients were assessed twice, first after a withdrawal of medication (OFF) and then after taking a dose of medication (ON). The parameters calculated were duration, mean and the wave kurtosis of the angular rate. The mean angular rate and the waveform kurtosis showed significant differences between the CG and ON (p < 0.05), and the CG and OFF (p < 0.05) A significant difference between ON and OFF was found in the duration and mean angular rate parameters (p < 0.001 and p < 0.0001, respectively). Our findings showed a difference in some turning parameters, namely duration and mean angular rate, between PD patients with and without medication. According to our results, medication decreases turn duration. Moreover, the mean angular rate increased with medication. These results support the view that turning is positively affected by medication.

P 104 - Head and hand tremor measurement and analysis for the differentiation between essential and dystonic tremors

Head tremor is a common clinical manifestation in essential tremor (ET) and can also occur as dystonic tremor (DT) in cervical dystonia. The clinical differentiation of head tremor due to ET and DT is not easy. Therefore, we developed instrumental methods using an accelerometer and an optical motion capture system to precisely measure and analyze head and hand tremor, and for distinguishing between ET and DT. Head tremor was measured with a Wireless XSens accelerometer and hand tremor by the Optitrack V120 Trio (MOCAP) and the tremor amplitude was computed. We included 24 patients fulfilling the criteria for ET (12 M, 12 F, mean age 58, SD 10) and 26 patients with cervical dystonia (5 M, 21 F mean age 64, SD 10). In supine position, visible head tremor disappeared in 5 out of 13 ET (38%) and in 8 out of 20 DT patients (40%). In ET patients, we found a strong correlation between the amplitudes of head tremor in sitting and supine position (rho=0.91, p<0.001). In contrast, in patients with DT, the correlation was weak (rho = 0.49, p = 0.01). Tremor of the upper limbs was significantly higher in the ET group, compared to DT (p < 0.001). Measurement of hand tremor with MOCAP confirmed the predicted difference in tremor of the upper limbs in patients with ET and DT. In the contrary, the analysis of head tremor amplitude did not confirm the hypothesis that head tremor disappears in supine position in patients with ET. The correlations show that the ET is just suppressed and depends on its amplitude. DT suppression is unpredictable.

P 024 - Near-infrared spectroscopy patterns of cortical activity during gait in Parkinson’s disease patients treated with DBS STN

Disorders of gait seriously affect the functional state and quality of life of patients with Parkinsons disease (PD). Impaired brain function underlies disorders of movement control in PD, however functional brain imaging with magnetic resonance (fMRI) is not feasible during gait. Near-Infrared Spectroscopy (NIRS) is a portable imaging method for measuring brain activity. It uses low-energy optical radiation to detect local changes of (de)oxyhemoglobin concentration in the cerebral cortex, like a fMRI. We included 8 patients with advanced PD chronically treated with DBS STN. Brain activity was recorded with the NIRSport. Gait was examined in 10 cycles, during which the active and resting phases alternated. Changes in oxyhemoglobin concentration were calculated from the native NIRS signal using a modified transformation of the Lambert-Beer Law. The signals were filtered in the 0.015-0.3 Hz band and the least-squares algorithm was fitted with the HRF function for each cycle separately, from which the median was finally calculated. The activity of the motor cortex was significantly higher during gait in the OFF compared to ON state (p = 0.02). In contrast, in other regions no differences were found. A higher motor cortex activity shown in the DBS OFF compared to ON state may reflect the impairment of gait control in PD. In general terms, the present study demonstrates the potential utility of the NIRS method in detecting functional changes of the brain during gait in patients with PD.

P07-Automatic pallidal neurons recognition based on the detection of the number of clusters from microrecordings in dystonia

Intraoperative microelectrode records (MER) are considered as the standard electrophysiological method for the precise positioning of the deep brain stimulation (DBS) electrode into the Globus pallidus interna (GPi). The final GPi position is chosen based on the firing patterns of individual neurons. Finding the number of neurons is usually done manually during the spike sorting. We propose methodology for neurons recognition based on the unsupervised learning. Thirty MERs (24 kHz 10s) of the basal ganglia from 10 patients (43.3(±14), 5F) with dystonia were recorded during DBS implantation. MERs were filtered in the 300–3000 Hz band and the amplitude detector (3× std of the background noise) was used to detect spikes. The WaveClus features were computed and its 2 PCA components were extracted for every spike. The optimal number of clusters evaluated by an expert rater, K-means + gap criterion (alg. 1) and the GMM + BIC (alg. 2) were analyzed. The total Intraclass correlation showed a significant inter-rater agreement for all 3 rater procedures (ICC = 0.62, p  It can contribute to better description of type of the GPi neurons involved in (non)motor functions. Supported by the GACR No. 16-13323S and AZV No. 16-28119a.