[EN] Limb movement is associated with well defined cortical activation patterns. Structural and functional changes in the brain affect the characteristics of these patterns (strength and topography). Novel strategies for poststroke motor rehabilitation could monitor cortical activity as an additional index of engagement and/or recovery. In this work we analyze differences in cortical activation related to movements of the affected vs. unaffected foot (dorsiflexion). Our results show stronger cortical activation during movements of the affected foot, and stronger responses at the vertex. Online assessment of cortical activation and the experiment described in this work could be added to traditional motor rehabilitation.This work was supported by the FP7 EU Research Project BETTER (247935). The authors are thankful to Silvia Mena del Horno and Javier Bonilla for assistance during the experiments.Belda Lois, JM. (2013). Cortical Activation Patterns of Cue-Paced Foot Movement in Subacute Stroke Patients. Biomedical Engineering / Biomedizinische Technik. 58(1):1-2. https://doi.org/10.1515/bmt-2013-4446S1258

G. R. Müller-Putz

J. M. Belda-Lois

T. Solis-Escalante

English

[EN] Limb movement is associated with well defined cortical activation patterns. Structural and functional changes in the brain affect the characteristics of these patterns (strength and topography). Novel strategies for poststroke motor rehabilitation could monitor cortical activity as an additional index of engagement and/or recovery. In this work we analyze differences in cortical activation related to movements of the affected vs. unaffected foot (dorsiflexion). Our results show stronger cortical activation during movements of the affected foot, and stronger responses at the vertex. Online assessment of cortical activation and the experiment described in this work could be added to traditional motor rehabilitation.This work was supported by the FP7 EU Research Project BETTER (247935). The authors are thankful to Silvia Mena del Horno and Javier Bonilla for assistance during the experiments.Belda Lois, JM. (2013). Cortical Activation Patterns of Cue-Paced Foot Movement in Subacute Stroke Patients. Biomedical Engineering / Biomedizinische Technik. 58(1):1-2. https://doi.org/10.1515/bmt-2013-44461258

Belda Lois, Juan Manuel

RiuNet

CORTICAL ACTIVATION PATTERNS OF CUE-PACED FOOTMOVEMENT IN SUBACUTE STROKE PATIENTST. Solis-Escalante1, J. M. Belda-Lois2, and G. R. Müller-Putz11Institute for Knowledge Discovery, Graz University of Technology, Austria2Instuto de Biomecánica de Valencia, Universitat Politécnica de Valencia, Spainteodoro.solisescalante@tugraz.atAbstract: Limb movement is associated with well definedcortical activation patterns. Structural and functionalchanges in the brain affect the characteristics of these pat-terns (strength and topography). Novel strategies for post-stroke motor rehabilitation could monitor cortical activityas an additional index of engagement and/or recovery. Inthis work we analyze differences in cortical activation re-lated to movements of the affected vs. unaffected foot (dorsi-flexion). Our results show stronger cortical activation dur-ing movements of the affected foot, and stronger responsesat the vertex. Online assessment of cortical activation andthe experiment described in this work could be added totraditional motor rehabilitation.Keywords: Event-related (de)synchronization, Post-movement beta rebound, Subacute stroke, EEGIntroductionNovel strategies for improving post-stroke motor rehabili-tation may monitor cortical activation during therapy [1, 2].Cortical activation patterns related to limb movement arevisible in the EEG as changes in the amplitude of senso-rimotor rhythms. These changes are described as event-related desyncrhonization (ERD) and event-related syn-chronization (ERS) [3]. In general, ERD can be interpretedas a correlate of an active cortical area, while ERS can beassociated with a deactivated or inhibited state of large neu-ronal networks. After a stroke, structural and functionalchanges in the brain affect the characteristics of ERD andERS patterns, i.e., strength and topography [4, 5, 6]. In thiswork, we investigate the cortical activation patterns of sub-acute stroke patients during foot movements of the affectedand unaffected side of their body.MethodsExperimental paradigm and data acquisition: Elevensubacute stroke patients (ischemic stroke, time after lesion8±2 months, age 63±14 yr., right handed, 5 female, 8with left hemiparesis) were recruited by the Instituto deBiomecánica de Valencia, Spain. The participants’ taskwas to perform left or right foot dorsiflexions followingcues shown on a computer screen (8 runs with 10 move-ments per leg). Movement side (left and right) and du-ration (3 to 4 s) were randomized. Online feedback, rep-resenting muscle activity, was presented to assist patientswith the execution of the foot movements. The experimentcue0 21 43 65 7 8 Time (s)9beepfixation cross10 (0.5 to 2.5 s)Inactive footTASOCzref gndFigure 1: Experimental paradigm, online feedback, andelectrode montage. Top: Schematic of the paradigm timing.Bottom left: Online feedback shows the muscle activity ofboth legs. Bottom right: Thirty-one electrodes around thevertex (electrode position Cz) used to record EEG. Elec-trode positions in red are Fz, C3, Cz, C4, and Pz.was approved by the local ethics committee and all partic-ipants gave written informed consent. EEG was recordedfrom 31 sites using a custom cap (Easycap, Herrsching,Germany) and active electrodes (g.tec, Schiedelberg, Aus-tria). The reference electrode was on the left earlobe andthe ground electrode was on the right mastoid. EMG wasrecorded from each leg: extensor hallucis longus (HL), tib-ialis anterior (TA), soleus (SO), and gastrocnemius (GA).Two monopolar channels were recorded from each muscleusing adhesive Ag/AgCl electrodes (reference on the righthip). Signals were acquired at 1.2 kHz using biosignal am-plifiers (g.USBamp) with filters between 0.1 and 100 Hz forEEG, 0.1 and 500 Hz for EMG, and a notch filter (50 Hz).Fig. 1 illustrates the paradigm timing, the cues on screen,the online feedback, and the EEG montage.Cortical activation: Laplacian filters were applied to theEEG data to improve the SNR [7]. Afterwards, the EEGwas filtered between 6 and 40 Hz and downsampled to600 Hz. Incorrectly performed trials (wrong leg movement,left/right co-contraction, late reaction time) and trials withartifacts (EEG>25µV) were rejected. Only nine deriva-tions close to electrode position Cz were considered (seeFig. 1), because ERD and ERS related to foot movementsare prominent at the vertex [8, 9]. Onset and offset of in-Biomed Tech 2013; 58 (Suppl. 1) © 2013 by Walter de Gruyter · Berlin · Boston. DOI 10.1515/bmt-2013-4446Brought to you by | Universidad Politecnica Valencia Biblioteca GeneralAuthenticated | 158.42.250.70Download Date | 3/20/14 10:31 AMdividual movements were identified from the TA signalsand used as triggers. The analysis focused on the peri-movement ERD and the post-movement ERS. Frequencybands showing the strongest ERD or ERS (average from500 ms to 1.5 s relative to movement onset/offset) were se-lected for further analysis. ERD and ERS waveforms werecomputed for each patient using a participant-specific fre-quency band. To summarize cortical activation, ERD wasintegrated in a 2.5 s window following movement onset,whereas ERS was integrated between 500 ms and 1.5 s, rel-ative to movement offset.Statistical analysis: Statistical significance was evalu-ated for the ERD and ERS independently, with two-wayANOVAs with factors SIDE × ELECTRODE. The factorSIDE had two levels: affected vs. unaffected side of thebody, whereas the factor ELECTRODE had nine levels:anterior-ipsilateral, anterior-central, anterior-contralateral,central-ipsilateral, vertex, central-contralateral, posterior-ipsilateral, posterior-central, and posterior-contralateral;relative to the affected side of the body. Significance valueswere corrected (Greenhouse-Geiser) if sphericity violationsoccurred.ResultsPeri-movement ERD: The average frequency band forERD was 10.7±5.2 and 22.4±7.5 Hz. Significant differ-ences were found for the main factor SIDE (F(1,10) =8.21, p<0.05), indicating that the ERD was stronger duringmovements of the affected foot (−381±293) than duringmovements of the unaffected foot (−275±226).Post-movement ERS: The average frequency band forERS was 17.1±5.1 and 24.1±6.1 Hz. Significant dif-ferences were found for the main factor ELECTRODE(F(8,80)=4.11, p<0.05, Greenhouse-Geiser corrected) andfor the interaction SIDE × ELECTRODE (F(8,80)=2.34,p<0.05). Multiple comparisons between electrode posi-tions revealed significant differences (p<0.05, Bonferronicorrected) between the vertex and the electrode positionsanterior ipsilateral, anterior contralateral, and central con-tralateral, i.e., the ERS at the vertex is stronger (147±171)than the anterior locations (ipsilateral: 9±66, contralateral:45±90) and the central contralateral to the affected foot (af-fected hemisphere: 10±75). The multiple comparisons didnot show significant differences for the interaction SIDE ×ELECTRODE.DiscussionThe aim of our work was to investigate the cortical activa-tion patterns of foot movements in subacute stroke patients.We found higher levels of cortical activity (ERD) for move-ments of the affected foot than during movements of theunaffected foot. Also, the post-movement response (ERS)at the vertex was stronger than pre-central positions and thecentral-contralateral to the affected foot (i.e., affected hemi-sphere). Experimental sessions of cue-paced active footmovement (with feedback) could be used as a novel strategyfor motor rehabilitation. Online monitoring of cortical ac-tivation and comparisons between movements of both feet,could be useful to assess motor recovery (i.e., changes incortical activation) [4, 5, 6]. Further work will focus on thepost-movement ERS and possible differences between sub-acute stroke patients and healthy persons.AcknowledgementThis work was supported by the FP7 EU Research ProjectBETTER (247935). The authors are thankful to SilviaMena del Horno and Javier Bonilla for assistance duringthe experiments.Bibliography[1] J. J. Daly and J. R. Wolpaw, “Brain-computer interfacesin neurological rehabilitation,” The Lancet Neurology,vol. 7, pp. 1032–1043, 2008. Review of BCIs in neuro-logical rehabilitation.[2] M. A. Dimyan and L. G. Cohen, “Neuroplasticity inthe context of motor rehabilitation after stroke.,” NatureReviews Neurology, vol. 7, pp. 76–85, 2011.[3] G. Pfurtscheller and F. H. Lopes da Silva, “Event-related EEG/MEG synchronization and desynchro-nization: basic principles,” Clinical Neurophysiology,vol. 110, pp. 1842–1857, 1999.[4] M. Stȩpień, J. Conradi, G. Waterstraat, F. U. Hohle-feld, G. Curio, and V. V. Nikulin, “Event-related desyn-chronization of sensorimotor EEG rhythms in hemi-paretic patients with acute stroke.,” Neuroscience Let-ters, vol. 488, pp. 17–21, Jan 2011.[5] V. Kaiser, I. Daly, F. Pichiorri, D. Mattia, G. R. Müller-Putz, and C. Neuper, “Relationship between electricalbrain responses to motor imagery and motor impair-ment in stroke,” Stroke, 2012.[6] K. Laaksonen, E. Kirveskari, J. P. Mäkelä, M. Kaste,S. Mustanoja, L. Nummenmaa, T. Tatlisumak, andN. Forss, “Effect of afferent input on motor cortex ex-citability during stroke recovery.,” Clinical Neurophys-iology, vol. 123, pp. 2429–2436, Dec 2012.[7] B. Hjorth, “An on-line transformation of EEG scalp po-tentials into orthogonal source derivations,” Electroen-cephalography and Clinical Neurophysiology, vol. 39,pp. 526–530, 1975.[8] C. Neuper and G. Pfurtscheller, “Post movement syn-chronization of beta rhythms in the EEG over the cor-tical foot area in man,” Neuroscience Letters, vol. 216,pp. 17–20, 1996.[9] G. R. Müller-Putz, D. Zimmermann, B. Graimann,K. Nestinger, G. Korisek, and G. Pfurtscheller, “Event-related beta EEG-changes during passive and attemptedfoot movements in paraplegic patients,” Brain Re-search, vol. 1137, pp. 84–91, 2007.Brought to you by | Universidad Politecnica Valencia Biblioteca GeneralAuthenticated | 158.42.250.70Download Date | 3/20/14 10:31 AM

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