TY - GEN AU - Tibold, Róbert AU - Farmer, SF AU - Davare, M TI - Modulation of 5-30 Hz EMG-EMG coherence during grip force tasks with varying precision constraints PY - 2015 UR - https://m2.mtmt.hu/api/publication/3040264 ID - 3040264 N1 - Skilled hand movements involve functional interactions across an extensive parieto-frontal cortical network. The neural mechanisms by which these structures cooperate spatio- temporally are not fully understood. One way to investigate how these different areas interact is to analyse common oscillatory drive in the electromyogram (EMG) since oscillatory activity facilitates synchrony between neuronal ensembles. Here we varied the task precision constraints to test whether different levels of activity in sensorimotor loops could alter the oscillatory interactions between the neural sources that underlie grip force control. To address this issue we quantified changes in EMG-EMG coherence between rectified surface EMG signals acquired simultaneously from first dorsal interosseous and abductor pollicis brevis while healthy individuals (n=9) performed visuomotor grip force tracking tasks at distinct force levels requiring either low or high precision. In a “force control” condition, subjects squeezed with their index finger and thumb a manipulandum with 2 force sensors (ATI mini40-E) to move a cursor on a computer screen along a predefined force target path by controlling their force. In a “position control” condition, two Phantom Desktop (Geomagic) haptic devices were attached to the index finger and thumb. Subjects had to vary their grip aperture to move the cursor along the target path whilst force exerted by the robots was kept constant. We found tracking performance improved as precision constraints increased in the position but not force control task, suggesting sensorimotor feedback loops acted more efficiently when processing position rather than force. A pooled coherence analysis with extended Chi^2 statistics revealed (1) a significant increase in the magnitude of coherence at 9-11 Hz frequencies when comparing high vs. low precision conditions and (2) a suppression of the coherence at 16–30 Hz frequencies for both precision levels in the position control task. There was an overall lack of coherence changes in the force control task. We suggest the increased common drive in the alpha-band is a signature of an enhanced oscillatory activity in cortical ensembles involved in sensorimotor control of position, but not force signals. It is plausible alpha-band oscillations implement generic filtration of neural activity interfering with high precision requirements, thus reallocating the computational resources on the control of grasp. These results are in line with the disengagement theory of task- irrelevant cortical regions achieved through “gating by inhibition” where the necessary information is routed to the task-relevant brain areas. LA - English DB - MTMT ER - TY - JOUR AU - Tibold, Róbert AU - Fuglevand, AJ TI - Prediction of muscle activity during loaded movements of the upper limb. JF - JOURNAL OF NEUROENGINEERING AND REHABILITATION J2 - J NEUROENG REHABIL VL - 12 PY - 2015 PG - 12 SN - 1743-0003 DO - 10.1186/1743-0003-12-6 UR - https://m2.mtmt.hu/api/publication/3040236 ID - 3040236 AB - BACKGROUND: Accurate prediction of electromyographic (EMG) signals associated with a variety of motor behaviors could, in theory, serve as activity templates needed to evoke movements in paralyzed individuals using functional electrical stimulation. Such predictions should encompass complex multi-joint movements and include interactions with objects in the environment. METHODS: Here we tested the ability of different artificial neural networks (ANNs) to predict EMG activities of 12 arm muscles while human subjects made free movements of the arm or grasped and moved objects of different weights and dimensions. Inputs to the trained ANNs included hand position, hand orientation, and thumb grip force. RESULTS: The ability of ANNs to predict EMG was equally as good for tasks involving interactions with external loads as for unloaded movements. The ANN that yielded the best predictions was a feed-forward network consisting of a single hidden layer of 30 neural elements. For this network, the average coefficient of determination (R2 value) between predicted and actual EMG signals across all nine subjects and 12 muscles during movements that involved episodes of moving objects was 0.43. CONCLUSION: This reasonable accuracy suggests that ANNs could be used to provide an initial estimate of the complex patterns of muscle stimulation needed to produce a wide array of movements, including those involving object interaction, in paralyzed individuals. LA - English DB - MTMT ER - TY - CHAP AU - Laczkó, József AU - Szolgay, Péter AU - Tibold, Róbert ED - PPKE, ITK TI - Movement rehabilitation T2 - The Jedlik Laboratories Research Activity PB - Pázmány University ePress CY - Budapest SN - 9789638988010 PY - 2013 SP - 36 EP - 39 PG - 4 UR - https://m2.mtmt.hu/api/publication/2735279 ID - 2735279 LA - English DB - MTMT ER - TY - THES AU - Tibold, Róbert TI - Neuromorphic modeling of reaching arm movements PY - 2012 SP - 112 DO - 10.15774/PPKE.ITK.2012.004 UR - https://m2.mtmt.hu/api/publication/2561325 ID - 2561325 LA - English DB - MTMT ER - TY - JOUR AU - Tibold, Róbert AU - Laczkó, József TI - The Effect of Load on Torques in Point-to-Point Arm Movements. a 3D Model TS - a 3D Model JF - JOURNAL OF MOTOR BEHAVIOR J2 - J MOTOR BEHAV VL - 44 PY - 2012 IS - 5 SP - 341 EP - 350 PG - 10 SN - 0022-2895 DO - 10.1080/00222895.2012.709200 UR - https://m2.mtmt.hu/api/publication/2071457 ID - 2071457 AB - ABSTRACT A dynamic, 3-dimensional model was developed to simulate slightly restricted (pronation-supination was not allowed) point-to-point movements of the upper limb under different external loads, which were modeled using 3 objects of distinct masses held in the hand. The model considered structural and biomechanical properties of the arm and measured coordinates of joint positions. The model predicted muscle torques generated by muscles and needed to produce the measured rotations in the shoulder and elbow joints. The effect of different object masses on torque profiles, magnitudes, and directions were studied. Correlation analysis has shown that torque profiles in the shoulder and elbow joints are load invariant. The shape of the torque magnitude-time curve is load invariant but it is scaled with the mass of the load. Objects with larger masses are associated with a lower deflection of the elbow torque with respect to the sagittal plane. Torque direction-time curve is load invariant scaled with the mass of the load. The authors propose that the load invariance of the torque magnitude-time curve and torque direction-time curve holds for object transporting arm movements not restricted to a plane. LA - English DB - MTMT ER - TY - CHAP AU - Tibold, Róbert AU - Laczkó, József ED - Simone, Frattasi TI - The effect of load on variances of object replacing arm movements T2 - Proceedings of the 4th International Symposium on Applied Sciences in Biomedical and Communication Technologies, ISABEL'11 PB - Association for Computing Machinery (ACM) CY - New York, New York SN - 1450309135 T3 - ACM international conference proceeding PY - 2011 PG - 3 DO - 10.1145/2093698.2093882 UR - https://m2.mtmt.hu/api/publication/3333112 ID - 3333112 LA - English DB - MTMT ER - TY - CHAP AU - Laczkó, József AU - Tibold, Róbert ED - Bércesné Novák, Ágnes TI - Neuromorph Movement Control T2 - Complex Development of Teaching Materials for Molekular Bionics BSc and Infobionics MSc = Molekuláris bionika és infobionika szakok tananyagának komplex fejlesztése konzorciumi keretben PB - Pázmány Péter Katolikus Egyetem Kiadója CY - Budapest SN - 9789633080481 PY - 2011 SP - 37 EP - 38 PG - 2 UR - https://m2.mtmt.hu/api/publication/2429733 ID - 2429733 LA - English DB - MTMT ER - TY - GEN AU - Laczkó, József AU - Tibold, Róbert TI - Variances of joint torques and muscle activities during arm movements with loads. Program No. 810.19 TS - Program No. 810.19 PY - 2011 UR - https://m2.mtmt.hu/api/publication/1861952 ID - 1861952 N1 - [Előadás] LA - English DB - MTMT ER - TY - JOUR AU - Tibold, Róbert AU - Fazekas, Gábor AU - Laczkó, József TI - Three-Dimensional Model to Predict Muscle Forces and Their Relation to Motor Variances in Reaching Arm Movements JF - JOURNAL OF APPLIED BIOMECHANICS J2 - J APPL BIOMECH VL - 27 PY - 2011 IS - 4 SP - 362 EP - 374 PG - 13 SN - 1065-8483 DO - 10.1123/jab.27.4.362 UR - https://m2.mtmt.hu/api/publication/1854515 ID - 1854515 AB - A three-dimensional (3-D) arm movement model is presented to simulate kinematic properties and muscle forces in reaching arm movements. Healthy subjects performed reaching movements repetitively either with or without a load in the hand. Joint coordinates were measured. Muscle moment arms, 3-D angular acceleration, and moment of inertias of arm segments were calculated to determine 3-D joint torques. Variances of hand position, arm configuration, and muscle activities were calculated. Ratios of movement variances observed in the two conditions (load versus without load) showed no differences for hand position and arm configuration variances. Virtual muscle force variances for all muscles except deltoid posterior and EMG variances for four muscles increased significantly by moving with the load. The greatly increased variances in muscle activity did not imply equally high increments in kinematic variances. We conclude that enhanced muscle cooperation through synergies helps to stabilize movement at the kinematic level when a load is added. LA - English DB - MTMT ER - TY - JOUR AU - Tibold, Róbert TI - The Effect of Load on Different Levels of Movement Controlling in Reaching Arm Movements JF - PÁZMÁNY PÉTER CATHOLIC UNIVERSITY PHD PROCEEDINGS J2 - PÁZMÁNY PÉTER CATHOLIC UNIVERSITY PHD PROCEEDINGS PY - 2010 SP - 9 EP - 12 PG - 4 SN - 1788-9197 UR - https://m2.mtmt.hu/api/publication/2435396 ID - 2435396 LA - English DB - MTMT ER -