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Original Research ARTICLE

Offline identification of imagined speed of wrist movements in paralyzed ALS patients from single-trial EEG

Ying Gu¹, Dario Farina¹*, Ander Ramos Murguialday², Kim Dremstrup¹, Pedro Montoya³ and Niels Birbaumer^2,4

Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark

Institute of Medical Psychology and Behavioral Neurobiology, Eberhard-Karls-University, Tübingen, Germany

Department of Psychology, Universitat of the Baleares, Palma, Spain

Istituto di Ricovero e Cura a Carattere Scientifico, Ospedale San Camillo, Italy

The study investigated the possibility of identifying the speed of an imagined movement from EEG recordings in amyotrophic lateral sclerosis (ALS) patients. EEG signals were acquired from four ALS patients during imagination of wrist extensions at two speeds (fast and slow), each repeated up to 100 times in random order. The movement-related cortical potentials (MRCPs) and averaged sensorimotor rhythm associated with the two tasks were obtained from the EEG recordings. Moreover, offline single-trial EEG classification was performed with discrete wavelet transform for feature extraction and support vector machine for classification. The speed of the task was encoded in the time delay of peak negativity in the MRCPs, which was shorter for faster than for slower movements. The average single-trial misclassification rate between speeds was 30.4 ± 3.5% when the best scalp location and time interval were selected for each individual. The scalp location and time interval leading to the lowest misclassification rate varied among patients. The results indicate that the imagination of movements at different speeds is a viable strategy for controlling a brain-computer interface system by ALS patients.

Keywords:

paralysis, MRCP, motor imagination, brain-computer interface

Citation:

Gu Y, Farina D, Murguialday AR, Dremstrup K, Montoya P and Birbaumer N (2009). Offline identification of imagined speed of wrist movements in paralyzed ALS patients from single-trial EEG. Front. Neurosci. 3:62. doi: 10.3389/neuro.20.003.2009

Received:

30 April 2009;

Paper pending published:

27 May 2009;

Accepted:

15 July 2009;

Published online:

10 August 2009.

Edited by:

Gert Pfurtscheller, Graz University of Technology, Austria

Reviewed by:

Florin Popescu, Fraunhofer FIRST, Germany
Gernot Mueller-Putz, Graz University of Technology, Austria

© 2009 Gu, Farina, Murguialday, Dremstrup, Montoya and Birbaumer. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

*Correspondence:

Dario Farina, Center for Sensory-Motor Interaction, Faculty of Engineering, Science and Medicine, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D-3, DK-9220 Aalborg E, Denmark. e-mail: df@hst.aau.dk