%0 Journal Article %J Brain topography %D 2000 %T Mu and beta rhythm topographies during motor imagery and actual movements. %A Dennis J. McFarland %A Miner, L. A. %A Theresa M Vaughan %A Jonathan Wolpaw %K beta rhythm %K EEG %K imagery %K mu rhythm %K sensorimotor cortex %X People can learn to control the 8-12 Hz mu rhythm and/or the 18-25 Hz beta rhythm in the EEG recorded over sensorimotor cortex and use it to control a cursor on a video screen. Subjects often report using motor imagery to control cursor movement, particularly early in training. We compared in untrained subjects the EEG topographies associated with actual hand movement to those associated with imagined hand movement. Sixty-four EEG channels were recorded while each of 33 adults moved left- or right-hand or imagined doing so. Frequency-specific differences between movement or imagery and rest, and between right- and left-hand movement or imagery, were evaluated by scalp topographies of voltage and r spectra, and principal component analysis. Both movement and imagery were associated with mu and beta rhythm desynchronization. The mu topographies showed bilateral foci of desynchronization over sensorimotor cortices, while the beta topographies showed peak desynchronization over the vertex. Both mu and beta rhythm left/right differences showed bilateral central foci that were stronger on the right side. The independence of mu and beta rhythms was demonstrated by differences for movement and imagery for the subjects as a group and by principal components analysis. The results indicated that the effects of imagery were not simply an attenuated version of the effects of movement. They supply evidence that motor imagery could play an important role in EEG-based communication, and suggest that mu and beta rhythms might provide independent control signals. %B Brain topography %V 12 %P 177–186 %8 03/2000 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/10791681 %R 10.1023/A:1023437823106 %0 Journal Article %J Archives of physical medicine and rehabilitation %D 1998 %T Answering questions with an electroencephalogram-based brain-computer interface. %A Miner, L. A. %A Dennis J. McFarland %A Jonathan Wolpaw %K User-Computer Interface %X OBJECTIVE: To demonstrate that humans can learn to control selected electroencephalographic components and use that control to answer simple questions. METHODS: Four adults (one with amyotrophic lateral sclerosis) learned to use electroencephalogram (EEG) mu rhythm (8 to 12Hz) or beta rhythm (18 to 25Hz) activity over sensorimotor cortex to control vertical cursor movement to targets at the top or bottom edge of a video screen. In subsequent sessions, the targets were replaced with the words YES and NO, and individuals used the cursor to answer spoken YES/NO questions from single- or multiple-topic question sets. They confirmed their answers through the response verification (RV) procedure, in which the word positions were switched and the question was answered again. RESULTS: For 5 consecutive sessions after initial question training, individuals were asked an average of 4.0 to 4.6 questions per minute; 64% to 87% of their answers were confirmed by the RV procedure and 93% to 99% of these answers were correct. Performances for single- and multiple-topic question sets did not differ significantly. CONCLUSIONS: The results indicate that (1) EEG-based cursor control can be used to answer simple questions with a high degree of accuracy, (2) attention to auditory queries and formulation of answers does not interfere with EEG-based cursor control, (3) question complexity (at least as represented by single versus multiple-topic question sets) does not noticeably affect performance, and (4) the RV procedure improves accuracy as expected. Several options for increasing the speed of communication appear promising. An EEG-based brain-computer interface could provide a new communication and control modality for people with severe motor disabilities. %B Archives of physical medicine and rehabilitation %V 79 %P 1029–1033 %8 09/1998 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/9749678 %R 10.1016/S0003-9993(98)90165-4 %0 Journal Article %J Electroencephalography and clinical neurophysiology %D 1998 %T EEG-based communication: analysis of concurrent EMG activity. %A Theresa M Vaughan %A Miner, L. A. %A Dennis J. McFarland %A Jonathan Wolpaw %K augmentative communication %K conditioning %K Electroencephalography %K Electromyography %K mu rhythm %K Rehabilitation %K sensorimotor cortex %X OBJECTIVE: Recent studies indicate that people can learn to control the amplitude of mu or beta rhythms in the EEG recorded from the scalp over sensorimotor cortex and can use that control to move a cursor to targets on the computer screen. While subjects do not move during performance, it is possible that inapparent or unconscious muscle contractions contribute to the changes in the mu and beta rhythm activity responsible for cursor movement. We evaluated this possibility. METHODS: EMG was recorded from 10 distal limb muscle groups while five trained subjects used mu or beta rhythms to move a cursor to targets at the bottom or top edge of a computer screen. RESULTS: EMG activity was very low during performance, averaging 4.0+/-4.4% (SD) of maximum voluntary contraction. Most important, the correlation, measured as r2, between target position and EMG activity averaged only 0.01+/-0.02, much lower than the correlation between target position and the EEG activity that controlled cursor movement, which averaged 0.39+/-0.18. CONCLUSIONS: These results strongly support the conclusion that EEG-based cursor control does no depend on concurrent muscle activity. EEG-based communication and control might provide a new augmentative communication option for those with severe motor disabilities. %B Electroencephalography and clinical neurophysiology %V 107 %P 428–433 %8 12/1998 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/9922089 %R 10.1016/S0013-4694(98)00107-2