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An X, Höhne J, Ming D, Blankertz B. Exploring combinations of auditory and visual stimuli for gaze-independent brain-computer interfaces. PLoS One 2014; 9:e111070. [PMID: 25350547 PMCID: PMC4211702 DOI: 10.1371/journal.pone.0111070] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 09/20/2014] [Indexed: 12/03/2022] Open
Abstract
For Brain-Computer Interface (BCI) systems that are designed for users with severe impairments of the oculomotor system, an appropriate mode of presenting stimuli to the user is crucial. To investigate whether multi-sensory integration can be exploited in the gaze-independent event-related potentials (ERP) speller and to enhance BCI performance, we designed a visual-auditory speller. We investigate the possibility to enhance stimulus presentation by combining visual and auditory stimuli within gaze-independent spellers. In this study with N = 15 healthy users, two different ways of combining the two sensory modalities are proposed: simultaneous redundant streams (Combined-Speller) and interleaved independent streams (Parallel-Speller). Unimodal stimuli were applied as control conditions. The workload, ERP components, classification accuracy and resulting spelling speed were analyzed for each condition. The Combined-speller showed a lower workload than uni-modal paradigms, without the sacrifice of spelling performance. Besides, shorter latencies, lower amplitudes, as well as a shift of the temporal and spatial distribution of discriminative information were observed for Combined-speller. These results are important and are inspirations for future studies to search the reason for these differences. For the more innovative and demanding Parallel-Speller, where the auditory and visual domains are independent from each other, a proof of concept was obtained: fifteen users could spell online with a mean accuracy of 87.7% (chance level <3%) showing a competitive average speed of 1.65 symbols per minute. The fact that it requires only one selection period per symbol makes it a good candidate for a fast communication channel. It brings a new insight into the true multisensory stimuli paradigms. Novel approaches for combining two sensory modalities were designed here, which are valuable for the development of ERP-based BCI paradigms.
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Affiliation(s)
- Xingwei An
- Department of Biomedical Engineering, Tianjin University, Tianjin, China
- Neurotechnology Group, Berlin Institute of Technology, Berlin, Germany
- * E-mail: (XA); (DM)
| | - Johannes Höhne
- Neurotechnology Group, Berlin Institute of Technology, Berlin, Germany
- Machine Learning Group, Berlin Institute of Technology, Berlin, Germany
| | - Dong Ming
- Department of Biomedical Engineering, Tianjin University, Tianjin, China
- * E-mail: (XA); (DM)
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Thurlings ME, Brouwer AM, Van Erp JBF, Werkhoven P. Gaze-independent ERP-BCIs: augmenting performance through location-congruent bimodal stimuli. Front Syst Neurosci 2014; 8:143. [PMID: 25249947 PMCID: PMC4157540 DOI: 10.3389/fnsys.2014.00143] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 07/23/2014] [Indexed: 11/22/2022] Open
Abstract
Gaze-independent event-related potential (ERP) based brain-computer interfaces (BCIs) yield relatively low BCI performance and traditionally employ unimodal stimuli. Bimodal ERP-BCIs may increase BCI performance due to multisensory integration or summation in the brain. An additional advantage of bimodal BCIs may be that the user can choose which modality or modalities to attend to. We studied bimodal, visual-tactile, gaze-independent BCIs and investigated whether or not ERP components’ tAUCs and subsequent classification accuracies are increased for (1) bimodal vs. unimodal stimuli; (2) location-congruent vs. location-incongruent bimodal stimuli; and (3) attending to both modalities vs. to either one modality. We observed an enhanced bimodal (compared to unimodal) P300 tAUC, which appeared to be positively affected by location-congruency (p = 0.056) and resulted in higher classification accuracies. Attending either to one or to both modalities of the bimodal location-congruent stimuli resulted in differences between ERP components, but not in classification performance. We conclude that location-congruent bimodal stimuli improve ERP-BCIs, and offer the user the possibility to switch the attended modality without losing performance.
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Affiliation(s)
- Marieke E Thurlings
- Information and Computing Sciences, Utrecht University Utrecht, Netherlands ; Perceptual and Cognitive Systems, TNO Soesterberg, Netherlands
| | | | - Jan B F Van Erp
- Perceptual and Cognitive Systems, TNO Soesterberg, Netherlands
| | - Peter Werkhoven
- Information and Computing Sciences, Utrecht University Utrecht, Netherlands
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Chen CH, Ho MS, Shyu KK, Hsu KC, Wang KW, Lee PL. A noninvasive brain computer interface using visually-induced near-infrared spectroscopy responses. Neurosci Lett 2014; 580:22-6. [DOI: 10.1016/j.neulet.2014.07.042] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Revised: 07/23/2014] [Accepted: 07/24/2014] [Indexed: 10/25/2022]
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Kaufmann T, Kübler A. Beyond maximum speed--a novel two-stimulus paradigm for brain-computer interfaces based on event-related potentials (P300-BCI). J Neural Eng 2014; 11:056004. [PMID: 25080406 DOI: 10.1088/1741-2560/11/5/056004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The speed of brain-computer interfaces (BCI), based on event-related potentials (ERP), is inherently limited by the commonly used one-stimulus paradigm. In this paper, we introduce a novel paradigm that can increase the spelling speed by a factor of 2, thereby extending the one-stimulus paradigm to a two-stimulus paradigm. Two different stimuli (a face and a symbol) are presented at the same time, superimposed on different characters and ERPs are classified using a multi-class classifier. Here, we present the proof-of-principle that is achieved with healthy participants. APPROACH Eight participants were confronted with the novel two-stimulus paradigm and, for comparison, with two one-stimulus paradigms that used either one of the stimuli. Classification accuracies (percentage of correctly predicted letters) and elicited ERPs from the three paradigms were compared in a comprehensive offline analysis. MAIN RESULTS The accuracies slightly decreased with the novel system compared to the established one-stimulus face paradigm. However, the use of two stimuli allowed for spelling at twice the maximum speed of the one-stimulus paradigms, and participants still achieved an average accuracy of 81.25%. This study introduced an alternative way of increasing the spelling speed in ERP-BCIs and illustrated that ERP-BCIs may not yet have reached their speed limit. Future research is needed in order to improve the reliability of the novel approach, as some participants displayed reduced accuracies. Furthermore, a comparison to the most recent BCI systems with individually adjusted, rapid stimulus timing is needed to draw conclusions about the practical relevance of the proposed paradigm. SIGNIFICANCE We introduced a novel two-stimulus paradigm that might be of high value for users who have reached the speed limit with the current one-stimulus ERP-BCI systems.
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Affiliation(s)
- Tobias Kaufmann
- Department of Psychology I, University of Würzburg, Marcusstr. 9-11, 97070 Würzburg, Germany. Institute of Clinical Medicine, University of Oslo, Kirkeveien 166, 0450 Oslo, Norway
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Kindermans PJ, Schreuder M, Schrauwen B, Müller KR, Tangermann M. True zero-training brain-computer interfacing--an online study. PLoS One 2014; 9:e102504. [PMID: 25068464 PMCID: PMC4113217 DOI: 10.1371/journal.pone.0102504] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 06/19/2014] [Indexed: 11/18/2022] Open
Abstract
Despite several approaches to realize subject-to-subject transfer of pre-trained classifiers, the full performance of a Brain-Computer Interface (BCI) for a novel user can only be reached by presenting the BCI system with data from the novel user. In typical state-of-the-art BCI systems with a supervised classifier, the labeled data is collected during a calibration recording, in which the user is asked to perform a specific task. Based on the known labels of this recording, the BCI's classifier can learn to decode the individual's brain signals. Unfortunately, this calibration recording consumes valuable time. Furthermore, it is unproductive with respect to the final BCI application, e.g. text entry. Therefore, the calibration period must be reduced to a minimum, which is especially important for patients with a limited concentration ability. The main contribution of this manuscript is an online study on unsupervised learning in an auditory event-related potential (ERP) paradigm. Our results demonstrate that the calibration recording can be bypassed by utilizing an unsupervised trained classifier, that is initialized randomly and updated during usage. Initially, the unsupervised classifier tends to make decoding mistakes, as the classifier might not have seen enough data to build a reliable model. Using a constant re-analysis of the previously spelled symbols, these initially misspelled symbols can be rectified posthoc when the classifier has learned to decode the signals. We compare the spelling performance of our unsupervised approach and of the unsupervised posthoc approach to the standard supervised calibration-based dogma for n = 10 healthy users. To assess the learning behavior of our approach, it is unsupervised trained from scratch three times per user. Even with the relatively low SNR of an auditory ERP paradigm, the results show that after a limited number of trials (30 trials), the unsupervised approach performs comparably to a classic supervised model.
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Affiliation(s)
- Pieter-Jan Kindermans
- Electronics and Information Systems (ELIS) Dept., Ghent University, Ghent, Belgium
- * E-mail: (PJK); (KRM); (MT)
| | - Martijn Schreuder
- Machine Learning Laboratory, Technical University of Berlin, Berlin, Germany
| | - Benjamin Schrauwen
- Electronics and Information Systems (ELIS) Dept., Ghent University, Ghent, Belgium
| | - Klaus-Robert Müller
- Machine Learning Laboratory, Technical University of Berlin, Berlin, Germany
- Department of Brain and Cognitive Engineering, Korea University, Seoul, Republic of Korea
- * E-mail: (PJK); (KRM); (MT)
| | - Michael Tangermann
- BrainLinks-BrainTools Excellence Cluster, Computer Science Dept., University of Freiburg, Freiburg, Germany
- * E-mail: (PJK); (KRM); (MT)
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Horki P, Klobassa DS, Pokorny C, Müller-Putz GR. Evaluation of healthy EEG responses for spelling through listener-assisted scanning. IEEE J Biomed Health Inform 2014; 19:29-36. [PMID: 25014972 DOI: 10.1109/jbhi.2014.2328494] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We investigated whether listener-assisted scanning, an alternative communication method for persons with severe motor and visual impairments but preserved cognitive skills, could be used for spelling with EEG. To that end spoken letters were presented sequentially, and the participants made selections by performing motor execution/imagery or a cognitive task. The motor task was a brisk dorsiflexion of both feet, and the cognitive task was related to working memory and perception of human voice. The motor imagery task yielded the most promising results with respect to letter selection accuracy, albeit with a large variation in individual performance. The cognitive task yielded significant ( p = 0.05) albeit moderate results. Closer inspection of grand average ERPs for the cognitive task revealed task-related modulation of a late negative component, which is novel in the auditory BCI literature. Guidelines for further development are presented.
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Höhne J, Tangermann M. Towards user-friendly spelling with an auditory brain-computer interface: the CharStreamer paradigm. PLoS One 2014; 9:e98322. [PMID: 24886978 PMCID: PMC4041754 DOI: 10.1371/journal.pone.0098322] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 04/30/2014] [Indexed: 11/18/2022] Open
Abstract
Realizing the decoding of brain signals into control commands, brain-computer interfaces (BCI) aim to establish an alternative communication pathway for locked-in patients. In contrast to most visual BCI approaches which use event-related potentials (ERP) of the electroencephalogram, auditory BCI systems are challenged with ERP responses, which are less class-discriminant between attended and unattended stimuli. Furthermore, these auditory approaches have more complex interfaces which imposes a substantial workload on their users. Aiming for a maximally user-friendly spelling interface, this study introduces a novel auditory paradigm: "CharStreamer". The speller can be used with an instruction as simple as "please attend to what you want to spell". The stimuli of CharStreamer comprise 30 spoken sounds of letters and actions. As each of them is represented by the sound of itself and not by an artificial substitute, it can be selected in a one-step procedure. The mental mapping effort (sound stimuli to actions) is thus minimized. Usability is further accounted for by an alphabetical stimulus presentation: contrary to random presentation orders, the user can foresee the presentation time of the target letter sound. Healthy, normal hearing users (n = 10) of the CharStreamer paradigm displayed ERP responses that systematically differed between target and non-target sounds. Class-discriminant features, however, varied individually from the typical N1-P2 complex and P3 ERP components found in control conditions with random sequences. To fully exploit the sequential presentation structure of CharStreamer, novel data analysis approaches and classification methods were introduced. The results of online spelling tests showed that a competitive spelling speed can be achieved with CharStreamer. With respect to user rating, it clearly outperforms a control setup with random presentation sequences.
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Affiliation(s)
- Johannes Höhne
- Machine Learning Laboratory, Berlin Institute of Technology, Berlin, Germany
- Neurotechnology group, Berlin Institute of Technology, Berlin, Germany
| | - Michael Tangermann
- BrainLinks-BrainTools Excellence Cluster, University of Freiburg, Freiburg, Germany
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Hill NJ, Ricci E, Haider S, McCane LM, Heckman S, Wolpaw JR, Vaughan TM. A practical, intuitive brain-computer interface for communicating 'yes' or 'no' by listening. J Neural Eng 2014; 11:035003. [PMID: 24838278 PMCID: PMC4096243 DOI: 10.1088/1741-2560/11/3/035003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Previous work has shown that it is possible to build an EEG-based binary brain-computer interface system (BCI) driven purely by shifts of attention to auditory stimuli. However, previous studies used abrupt, abstract stimuli that are often perceived as harsh and unpleasant, and whose lack of inherent meaning may make the interface unintuitive and difficult for beginners. We aimed to establish whether we could transition to a system based on more natural, intuitive stimuli (spoken words 'yes' and 'no') without loss of performance, and whether the system could be used by people in the locked-in state. APPROACH We performed a counterbalanced, interleaved within-subject comparison between an auditory streaming BCI that used beep stimuli, and one that used word stimuli. Fourteen healthy volunteers performed two sessions each, on separate days. We also collected preliminary data from two subjects with advanced amyotrophic lateral sclerosis (ALS), who used the word-based system to answer a set of simple yes-no questions. MAIN RESULTS The N1, N2 and P3 event-related potentials elicited by words varied more between subjects than those elicited by beeps. However, the difference between responses to attended and unattended stimuli was more consistent with words than beeps. Healthy subjects' performance with word stimuli (mean 77% ± 3.3 s.e.) was slightly but not significantly better than their performance with beep stimuli (mean 73% ± 2.8 s.e.). The two subjects with ALS used the word-based BCI to answer questions with a level of accuracy similar to that of the healthy subjects. SIGNIFICANCE Since performance using word stimuli was at least as good as performance using beeps, we recommend that auditory streaming BCI systems be built with word stimuli to make the system more pleasant and intuitive. Our preliminary data show that word-based streaming BCI is a promising tool for communication by people who are locked in.
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Affiliation(s)
- N. Jeremy Hill
- Wadsworth Center, New York State Department of Health (Albany, NY,
USA)
- Helen Hayes Hospital (West Haverstraw, NY, USA)
| | - Erin Ricci
- Wadsworth Center, New York State Department of Health (Albany, NY,
USA)
| | - Sameah Haider
- Wadsworth Center, New York State Department of Health (Albany, NY,
USA)
- Albany Medical College (Albany, NY, USA)
| | - Lynn M. McCane
- Wadsworth Center, New York State Department of Health (Albany, NY,
USA)
| | - Susan Heckman
- Wadsworth Center, New York State Department of Health (Albany, NY,
USA)
| | - Jonathan R. Wolpaw
- Wadsworth Center, New York State Department of Health (Albany, NY,
USA)
- University at Albany, State University of New York (Albany, NY, USA)
| | - Theresa M. Vaughan
- Wadsworth Center, New York State Department of Health (Albany, NY,
USA)
- Helen Hayes Hospital (West Haverstraw, NY, USA)
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Winkler I, Brandl S, Horn F, Waldburger E, Allefeld C, Tangermann M. Robust artifactual independent component classification for BCI practitioners. J Neural Eng 2014; 11:035013. [DOI: 10.1088/1741-2560/11/3/035013] [Citation(s) in RCA: 181] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kindermans PJ, Tangermann M, Müller KR, Schrauwen B. Integrating dynamic stopping, transfer learning and language models in an adaptive zero-training ERP speller. J Neural Eng 2014; 11:035005. [PMID: 24834896 DOI: 10.1088/1741-2560/11/3/035005] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Most BCIs have to undergo a calibration session in which data is recorded to train decoders with machine learning. Only recently zero-training methods have become a subject of study. This work proposes a probabilistic framework for BCI applications which exploit event-related potentials (ERPs). For the example of a visual P300 speller we show how the framework harvests the structure suitable to solve the decoding task by (a) transfer learning, (b) unsupervised adaptation, (c) language model and (d) dynamic stopping. APPROACH A simulation study compares the proposed probabilistic zero framework (using transfer learning and task structure) to a state-of-the-art supervised model on n = 22 subjects. The individual influence of the involved components (a)-(d) are investigated. MAIN RESULTS Without any need for a calibration session, the probabilistic zero-training framework with inter-subject transfer learning shows excellent performance--competitive to a state-of-the-art supervised method using calibration. Its decoding quality is carried mainly by the effect of transfer learning in combination with continuous unsupervised adaptation. SIGNIFICANCE A high-performing zero-training BCI is within reach for one of the most popular BCI paradigms: ERP spelling. Recording calibration data for a supervised BCI would require valuable time which is lost for spelling. The time spent on calibration would allow a novel user to spell 29 symbols with our unsupervised approach. It could be of use for various clinical and non-clinical ERP-applications of BCI.
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Affiliation(s)
- Pieter-Jan Kindermans
- Electronics and Information Systems (ELIS) Department, Ghent University, Sint Pietersnieuwstraat 41, B-9000 Ghent, Belgium
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61
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Lorenz R, Pascual J, Blankertz B, Vidaurre C. Towards a holistic assessment of the user experience with hybrid BCIs. J Neural Eng 2014; 11:035007. [DOI: 10.1088/1741-2560/11/3/035007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Mainsah BO, Colwell KA, Collins LM, Throckmorton CS. Utilizing a language model to improve online dynamic data collection in P300 spellers. IEEE Trans Neural Syst Rehabil Eng 2014; 22:837-46. [PMID: 24808413 DOI: 10.1109/tnsre.2014.2321290] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
P300 spellers provide a means of communication for individuals with severe physical limitations, especially those with locked-in syndrome, such as amyotrophic lateral sclerosis. However, P300 speller use is still limited by relatively low communication rates due to the multiple data measurements that are required to improve the signal-to-noise ratio of event-related potentials for increased accuracy. Therefore, the amount of data collection has competing effects on accuracy and spelling speed. Adaptively varying the amount of data collection prior to character selection has been shown to improve spelling accuracy and speed. The goal of this study was to optimize a previously developed dynamic stopping algorithm that uses a Bayesian approach to control data collection by incorporating a priori knowledge via a language model. Participants ( n = 17) completed online spelling tasks using the dynamic stopping algorithm, with and without a language model. The addition of the language model resulted in improved participant performance from a mean theoretical bit rate of 46.12 bits/min at 88.89% accuracy to 54.42 bits/min ( ) at 90.36% accuracy.
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63
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64
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Treder MS, Purwins H, Miklody D, Sturm I, Blankertz B. Decoding auditory attention to instruments in polyphonic music using single-trial EEG classification. J Neural Eng 2014; 11:026009. [PMID: 24608228 DOI: 10.1088/1741-2560/11/2/026009] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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65
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Geuze J, Farquhar J, Desain P. Towards a communication brain computer interface based on semantic relations. PLoS One 2014; 9:e87511. [PMID: 24516552 PMCID: PMC3917851 DOI: 10.1371/journal.pone.0087511] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 12/21/2013] [Indexed: 11/23/2022] Open
Abstract
This article investigates a possible Brain Computer Interface (BCI) based on semantic relations. The BCI determines which prime word a subject has in mind by presenting probe words using an intelligent algorithm. Subjects indicate when a presented probe word is related to the prime word by a single finger tap. The detection of the neural signal associated with this movement is used by the BCI to decode the prime word. The movement detector combined both the evoked (ERP) and induced (ERD) responses elicited with the movement. Single trial movement detection had an average accuracy of 67%. The decoding of the prime word had an average accuracy of 38% when using 100 probes and 150 possible targets, and 41% after applying a dynamic stopping criterium, reducing the average number of probes to 47. The article shows that the intelligent algorithm used to present the probe words has a significantly higher performance than a random selection of probes. Simulations demonstrate that the BCI also works with larger vocabulary sizes, and the performance scales logarithmically with vocabulary size.
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Affiliation(s)
- Jeroen Geuze
- Radboud University Nijmegen, Donders Institute for Brain, Cognition, and Behaviour, Nijmegen, The Netherlands
| | - Jason Farquhar
- Radboud University Nijmegen, Donders Institute for Brain, Cognition, and Behaviour, Nijmegen, The Netherlands
| | - Peter Desain
- Radboud University Nijmegen, Donders Institute for Brain, Cognition, and Behaviour, Nijmegen, The Netherlands
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66
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Kaufmann T, Herweg A, Kübler A. Toward brain-computer interface based wheelchair control utilizing tactually-evoked event-related potentials. J Neuroeng Rehabil 2014; 11:7. [PMID: 24428900 PMCID: PMC3898245 DOI: 10.1186/1743-0003-11-7] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 12/23/2013] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND People with severe disabilities, e.g., due to neurodegenerative disease, depend on technology that allows for accurate wheelchair control. For those who cannot operate a wheelchair with a joystick, brain-computer interfaces (BCI) may offer a valuable option. Technology depending on visual or auditory input may not be feasible as these modalities are dedicated to processing of environmental stimuli (e.g., recognition of obstacles, ambient noise). Herein we thus validated the feasibility of a BCI based on tactually-evoked event-related potentials (ERP) for wheelchair control. Furthermore, we investigated use of a dynamic stopping method to improve speed of the tactile BCI system. METHODS Positions of four tactile stimulators represented navigation directions (left thigh: move left; right thigh: move right; abdomen: move forward; lower neck: move backward) and N = 15 participants delivered navigation commands by focusing their attention on the desired tactile stimulus in an oddball-paradigm. RESULTS Participants navigated a virtual wheelchair through a building and eleven participants successfully completed the task of reaching 4 checkpoints in the building. The virtual wheelchair was equipped with simulated shared-control sensors (collision avoidance), yet these sensors were rarely needed. CONCLUSION We conclude that most participants achieved tactile ERP-BCI control sufficient to reliably operate a wheelchair and dynamic stopping was of high value for tactile ERP classification. Finally, this paper discusses feasibility of tactile ERPs for BCI based wheelchair control.
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Affiliation(s)
- Tobias Kaufmann
- Department of Psychology I, University of Würzburg, Marcusstr 9-11, Würzburg 97070, Germany
| | - Andreas Herweg
- Department of Psychology I, University of Würzburg, Marcusstr 9-11, Würzburg 97070, Germany
| | - Andrea Kübler
- Department of Psychology I, University of Würzburg, Marcusstr 9-11, Würzburg 97070, Germany
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Huggins JE, Guger C, Allison B, Anderson CW, Batista A, Brouwer AM(AM, Brunner C, Chavarriaga R, Fried-Oken M, Gunduz A, Gupta D, Kübler A, Leeb R, Lotte F, Miller LE, Müller-Putz G, Rutkowski T, Tangermann M, Thompson DE. Workshops of the Fifth International Brain-Computer Interface Meeting: Defining the Future. BRAIN-COMPUTER INTERFACES 2014; 1:27-49. [PMID: 25485284 PMCID: PMC4255956 DOI: 10.1080/2326263x.2013.876724] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The Fifth International Brain-Computer Interface (BCI) Meeting met June 3-7th, 2013 at the Asilomar Conference Grounds, Pacific Grove, California. The conference included 19 workshops covering topics in brain-computer interface and brain-machine interface research. Topics included translation of BCIs into clinical use, standardization and certification, types of brain activity to use for BCI, recording methods, the effects of plasticity, special interest topics in BCIs applications, and future BCI directions. BCI research is well established and transitioning to practical use to benefit people with physical impairments. At the same time, new applications are being explored, both for people with physical impairments and beyond. Here we provide summaries of each workshop, illustrating the breadth and depth of BCI research and high-lighting important issues for future research and development.
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Affiliation(s)
- Jane E. Huggins
- Department of Physical Medicine and Rehabilitation, Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 325 East Eisenhower, Room 3017; Ann Arbor, Michigan 48108-5744, 734-936-7177
| | - Christoph Guger
- Christoph Guger, g.tec medical engineering GmbH/Guger Technologies OG, Austria, Sierningstrasse 14, 4521 Schiedlberg, Austria, +43725122240-0
| | - Brendan Allison
- University of California at San Diego, La Jolla, CA 91942 (415) 490 7551
| | - Charles W. Anderson
- Department of Computer Science, Colorado State University, Fort Collins, CO 80523; telephone: 970-491-7491
| | - Aaron Batista
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, 3501 5th Av, BST3 4074; Pittsburgh, PA 15261; (412) 383-5394
| | - Anne-Marie (A.-M.) Brouwer
- The Netherlands Organization for Applied Scientific Research; P.O. Box 23/Kampweg 5, 3769 ZG Soesterberg, the Netherlands, ++31 (0)888 665960
| | - Clemens Brunner
- Institute for Knowledge Discovery, Laboratory of Brain-Computer Interfaces, Graz University of Technology, Inffeldgasse 13/4, 8010; Graz, Austria
| | - Ricardo Chavarriaga
- Center for Neuroprosthetics, École Polytechnique Fédérale de Lausanne, Switzerland, EPFL-STI-CNBI, Station 11, 1005 Lausanne, Switzerland; Telephone: +41 21 693 6968
| | - Melanie Fried-Oken
- Oregon Health & Science University; Institute on Development & Disability; 707 SW Gaines Street; Portland, Oregon, United States; O: 503.494.7587, F: 503.494.6868
| | - Aysegul Gunduz
- Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611, USA; Phone: +1 (352) 273 6877; Fax: +1 (352) 273 9221
| | - Disha Gupta
- Dept. of Neurology, Albany Medical College/Brain Computer Interfacing Lab, Wadsworth Center, NY State Dept. of Health, Albany, New York, USA
| | - Andrea Kübler
- Institute of Psychology, University of Würzburg; Marcusstr.9-11; 97070 Würzburg, Germany. Phone.: 0049 931 31 80179; Fax: 0049 931 31 82424
| | - Robert Leeb
- Center for Neuroprosthetics, École Polytechnique Fédérale de Lausanne, Switzerland
| | - Fabien Lotte
- Inria Bordeaux Sud-Ouest/LaBRI, 200 avenue de la vieille tour, 33405, Talence Cedex, France, Tel: +33 5 24 57 41 26
| | - Lee E. Miller
- Departments of Physiology, Physical Medicine and Rehab, and Biomedical Engineering; Feinberg School of Medicine; Northwestern University; Chicago, Illinois, United States; Ward 5-01; 303 East Chicago Avenue; Chicago, Illinois 60611; Phone: (312) 503 – 8677; Fax: (312) 503 – 5101
| | - Gernot Müller-Putz
- Institute for Knowledge Discovery, Laboratory of Brain-Computer Interfaces, Graz University of Technology, Inffeldgasse 13/4, 8010; Graz, Austria
| | - Tomasz Rutkowski
- Life Science Center of TARA, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577 Japan; TEL: +81 (0)29-853-6261
| | - Michael Tangermann
- Excellence Cluster BrainLinks-BrainTools, Dept. Computer Science, University of Freiburg, Freiburg, Germany, Albertstr. 23; 79104 Freiburg; Germany; Phone: +49.(0)761.2038423, Fax : +49.(0)761.2038417
| | - David Edward Thompson
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2800 Plymouth Road, Bdlg 26 Rm G06W-B; Ann Arbor, MI 48109; 734-763-7104
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68
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Zander TO, Brönstrup J, Lorenz R, Krol LR. Towards BCI-Based Implicit Control in Human–Computer Interaction. HUMAN–COMPUTER INTERACTION SERIES 2014. [DOI: 10.1007/978-1-4471-6392-3_4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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69
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Speier W, Arnold C, Pouratian N. Evaluating true BCI communication rate through mutual information and language models. PLoS One 2013; 8:e78432. [PMID: 24167623 PMCID: PMC3805537 DOI: 10.1371/journal.pone.0078432] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 09/10/2013] [Indexed: 11/19/2022] Open
Abstract
Brain-computer interface (BCI) systems are a promising means for restoring communication to patients suffering from “locked-in” syndrome. Research to improve system performance primarily focuses on means to overcome the low signal to noise ratio of electroencephalogric (EEG) recordings. However, the literature and methods are difficult to compare due to the array of evaluation metrics and assumptions underlying them, including that: 1) all characters are equally probable, 2) character selection is memoryless, and 3) errors occur completely at random. The standardization of evaluation metrics that more accurately reflect the amount of information contained in BCI language output is critical to make progress. We present a mutual information-based metric that incorporates prior information and a model of systematic errors. The parameters of a system used in one study were re-optimized, showing that the metric used in optimization significantly affects the parameter values chosen and the resulting system performance. The results of 11 BCI communication studies were then evaluated using different metrics, including those previously used in BCI literature and the newly advocated metric. Six studies' results varied based on the metric used for evaluation and the proposed metric produced results that differed from those originally published in two of the studies. Standardizing metrics to accurately reflect the rate of information transmission is critical to properly evaluate and compare BCI communication systems and advance the field in an unbiased manner.
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Affiliation(s)
- William Speier
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, United States of America
- Medical Imaging Informatics Group, University of California Los Angeles, Los Angeles, California, United States of America
| | - Corey Arnold
- Medical Imaging Informatics Group, University of California Los Angeles, Los Angeles, California, United States of America
| | - Nader Pouratian
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
- Interdepartmental Program in Neuroscience, University of California Los Angeles, Los Angeles, California, United States of America
- Brain Research Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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70
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Yaming Xu, Nakajima Y. A Two-Level Predictive Event-Related Potential-Based Brain–Computer Interface. IEEE Trans Biomed Eng 2013; 60:2839-47. [DOI: 10.1109/tbme.2013.2265103] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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71
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Aloise F, Aricò P, Schettini F, Salinari S, Mattia D, Cincotti F. Asynchronous gaze-independent event-related potential-based brain-computer interface. Artif Intell Med 2013; 59:61-9. [PMID: 24080078 DOI: 10.1016/j.artmed.2013.07.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Revised: 07/30/2013] [Accepted: 07/31/2013] [Indexed: 10/26/2022]
Abstract
OBJECTIVE In this study a gaze independent event related potential (ERP)-based brain computer interface (BCI) for communication purpose was combined with an asynchronous classifier endowed with dynamical stopping feature. The aim was to evaluate if and how the performance of such asynchronous system could be negatively affected in terms of communication efficiency and robustness to false positives during the intentional no-control state. MATERIAL AND METHODS The proposed system was validated with the participation of 9 healthy subjects. A comparison was performed between asynchronous and synchronous classification technique outputs while users were controlling the same gaze independent BCI interface. The performance of both classification techniques were assessed both off-line and on-line by means of the efficiency metric introduced by Bianchi et al. (2007). This latter metric allows to set a different misclassification cost for wrong classifications and abstentions. Robustness was evaluated as the rate of false positives occurring during voluntary no-control states. RESULTS The asynchronous classifier did not exhibited significantly higher accuracy or lower error rate with respect to the synchronous classifier (accuracy: 74.66% versus 87.96%, error rate: 7.11% versus 12.04% respectively). However, the on-line and off-line analysis revealed that the communication efficiency was significantly improved (p<.05) with the asynchronous classification modality as compared with the synchronous. Furthermore, the asynchronous classifier proved to be robust to false positives during intentional no-control state which occur during the ongoing visual stimulation (less than 1 false positive every 6min). CONCLUSION As such, the proposed ERP-BCI system which combines an asynchronous classifier with a gaze independent interface is a promising solution to be further explored in order to increase the general usability of ERP-based BCI systems designed for severely disabled people with an impairment of the voluntary control of eye movements. In fact, the asynchronous classifier can improve communication efficiency automatically adapting the number of stimulus repetitions to the current user's state and suspending the control if he/she does not intend to select an item.
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Affiliation(s)
- Fabio Aloise
- Neuroelectrical Imaging and BCI Lab, Fondazione Santa Lucia IRCCS, Via Ardeatina 306, 00142 Rome, Italy; Department of Computer, Control, and Management Engineering Antonio Ruberti, Sapienza University, Via Ariosto 25, 00185 Rome, Italy.
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72
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Brain Evoked Potential Latencies Optimization for Spatial Auditory Brain–Computer Interface. Cognit Comput 2013. [DOI: 10.1007/s12559-013-9228-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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73
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Höhne J, Tangermann M. How stimulation speed affects Event-Related Potentials and BCI performance. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:1802-5. [PMID: 23366261 DOI: 10.1109/embc.2012.6346300] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In most paradigms for Brain-Computer Interfaces (BCIs) that are based on Event-Related Potentials (ERPs), stimuli are presented with a pre-defined and constant speed. In order to boost BCI performance by optimizing the parameters of stimulation, this offline study investigates the impact of the stimulus onset asynchrony (SOA) on ERPs and the resulting classification accuracy. The SOA is defined as the time between the onsets of two consecutive stimuli, which represents a measure for stimulation speed. A simple auditory oddball paradigm was tested in 14 SOA conditions with a SOA between 50 ms and 1000 ms. Based on an offline ERP analysis, the BCI performance (quantified by the Information Transfer Rate, ITR in bits/min) was simulated. A great variability in the simulated BCI performance was observed within subjects (N=11). This indicates a potential increase in BCI performance (≥ 1.6 bits/min) for ERP-based paradigms, if the stimulation speed is specified for each user individually.
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Affiliation(s)
- Johannes Höhne
- Machine Learning Department, Berlin Institute of Technology, Berlin, Germany.
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74
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Kaufmann T, Holz EM, Kübler A. Comparison of tactile, auditory, and visual modality for brain-computer interface use: a case study with a patient in the locked-in state. Front Neurosci 2013; 7:129. [PMID: 23898236 PMCID: PMC3721006 DOI: 10.3389/fnins.2013.00129] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 07/05/2013] [Indexed: 12/03/2022] Open
Abstract
This paper describes a case study with a patient in the classic locked-in state, who currently has no means of independent communication. Following a user-centered approach, we investigated event-related potentials (ERP) elicited in different modalities for use in brain-computer interface (BCI) systems. Such systems could provide her with an alternative communication channel. To investigate the most viable modality for achieving BCI based communication, classic oddball paradigms (1 rare and 1 frequent stimulus, ratio 1:5) in the visual, auditory and tactile modality were conducted (2 runs per modality). Classifiers were built on one run and tested offline on another run (and vice versa). In these paradigms, the tactile modality was clearly superior to other modalities, displaying high offline accuracy even when classification was performed on single trials only. Consequently, we tested the tactile paradigm online and the patient successfully selected targets without any error. Furthermore, we investigated use of the visual or tactile modality for different BCI systems with more than two selection options. In the visual modality, several BCI paradigms were tested offline. Neither matrix-based nor so-called gaze-independent paradigms constituted a means of control. These results may thus question the gaze-independence of current gaze-independent approaches to BCI. A tactile four-choice BCI resulted in high offline classification accuracies. Yet, online use raised various issues. Although performance was clearly above chance, practical daily life use appeared unlikely when compared to other communication approaches (e.g., partner scanning). Our results emphasize the need for user-centered design in BCI development including identification of the best stimulus modality for a particular user. Finally, the paper discusses feasibility of EEG-based BCI systems for patients in classic locked-in state and compares BCI to other AT solutions that we also tested during the study.
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Affiliation(s)
- Tobias Kaufmann
- Department for Psychology I, Institute for Psychology, University of Würzburg Würzburg, Germany
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75
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Schreuder M, Höhne J, Blankertz B, Haufe S, Dickhaus T, Tangermann M. Optimizing event-related potential based brain-computer interfaces: a systematic evaluation of dynamic stopping methods. J Neural Eng 2013; 10:036025. [PMID: 23685458 DOI: 10.1088/1741-2560/10/3/036025] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE In brain-computer interface (BCI) research, systems based on event-related potentials (ERP) are considered particularly successful and robust. This stems in part from the repeated stimulation which counteracts the low signal-to-noise ratio in electroencephalograms. Repeated stimulation leads to an optimization problem, as more repetitions also cost more time. The optimal number of repetitions thus represents a data-dependent trade-off between the stimulation time and the obtained accuracy. Several methods for dealing with this have been proposed as 'early stopping', 'dynamic stopping' or 'adaptive stimulation'. Despite their high potential for BCI systems at the patient's bedside, those methods are typically ignored in current BCI literature. The goal of the current study is to assess the benefit of these methods. APPROACH This study assesses for the first time the existing methods on a common benchmark of both artificially generated data and real BCI data of 83 BCI sessions, allowing for a direct comparison between these methods in the context of text entry. MAIN RESULTS The results clearly show the beneficial effect on the online performance of a BCI system, if the trade-off between the number of stimulus repetitions and accuracy is optimized. All assessed methods work very well for data of good subjects, and worse for data of low-performing subjects. Most methods, however, are robust in the sense that they do not reduce the performance below the baseline of a simple no stopping strategy. SIGNIFICANCE Since all methods can be realized as a module between the BCI and an application, minimal changes are needed to include these methods into existing BCI software architectures. Furthermore, the hyperparameters of most methods depend to a large extend on only a single variable-the discriminability of the training data. For the convenience of BCI practitioners, the present study proposes linear regression coefficients for directly estimating the hyperparameters from the data based on this discriminability. The data that were used in this publication are made publicly available to benchmark future methods.
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76
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Kindermans PJ, Verschore H, Schrauwen B. A unified probabilistic approach to improve spelling in an event-related potential-based brain-computer interface. IEEE Trans Biomed Eng 2013; 60:2696-705. [PMID: 23674419 DOI: 10.1109/tbme.2013.2262524] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In recent years, in an attempt to maximize performance, machine learning approaches for event-related potential (ERP) spelling have become more and more complex. In this paper, we have taken a step back as we wanted to improve the performance without building an overly complex model, that cannot be used by the community. Our research resulted in a unified probabilistic model for ERP spelling, which is based on only three assumptions and incorporates language information. On top of that, the probabilistic nature of our classifier yields a natural dynamic stopping strategy. Furthermore, our method uses the same parameters across 25 subjects from three different datasets. We show that our classifier, when enhanced with language models and dynamic stopping, improves the spelling speed and accuracy drastically. Additionally, we would like to point out that as our model is entirely probabilistic, it can easily be used as the foundation for complex systems in future work. All our experiments are executed on publicly available datasets to allow for future comparison with similar techniques.
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77
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Acqualagna L, Blankertz B. Gaze-independent BCI-spelling using rapid serial visual presentation (RSVP). Clin Neurophysiol 2013; 124:901-8. [PMID: 23466266 DOI: 10.1016/j.clinph.2012.12.050] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 11/27/2012] [Accepted: 12/05/2012] [Indexed: 11/18/2022]
Affiliation(s)
- Laura Acqualagna
- Machine Learning Laboratory, Berlin Institute of Technology, Berlin, Germany.
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78
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Lim JH, Hwang HJ, Han CH, Jung KY, Im CH. Classification of binary intentions for individuals with impaired oculomotor function: 'eyes-closed' SSVEP-based brain-computer interface (BCI). J Neural Eng 2013; 10:026021. [PMID: 23528484 DOI: 10.1088/1741-2560/10/2/026021] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Some patients suffering from severe neuromuscular diseases have difficulty controlling not only their bodies but also their eyes. Since these patients have difficulty gazing at specific visual stimuli or keeping their eyes open for a long time, they are unable to use the typical steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) systems. In this study, we introduce a new paradigm for SSVEP-based BCI, which can be potentially suitable for disabled individuals with impaired oculomotor function. APPROACH The proposed electroencephalography (EEG)-based BCI system allows users to express their binary intentions without needing to open their eyes. A pair of glasses with two light emitting diodes flickering at different frequencies was used to present visual stimuli to participants with their eyes closed, and we classified the recorded EEG patterns in the online experiments conducted with five healthy participants and one patient with severe amyotrophic lateral sclerosis (ALS). MAIN RESULTS Through offline experiments performed with 11 participants, we confirmed that human SSVEP could be modulated by visual selective attention to a specific light stimulus penetrating through the eyelids. Furthermore, the recorded EEG patterns could be classified with accuracy high enough for use in a practical BCI system. After customizing the parameters of the proposed SSVEP-based BCI paradigm based on the offline analysis results, binary intentions of five healthy participants were classified in real time. The average information transfer rate of our online experiments reached 10.83 bits min(-1). A preliminary online experiment conducted with an ALS patient showed a classification accuracy of 80%. SIGNIFICANCE The results of our offline and online experiments demonstrated the feasibility of our proposed SSVEP-based BCI paradigm. It is expected that our 'eyes-closed' SSVEP-based BCI system can be potentially used for communication of disabled individuals with impaired oculomotor function.
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Affiliation(s)
- Jeong-Hwan Lim
- Department of Biomedical Engineering, Hanyang University, Seoul 133-731, Korea
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79
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Ruf CA, De Massari D, Furdea A, Matuz T, Fioravanti C, van der Heiden L, Halder S, Birbaumer N. Semantic classical conditioning and brain-computer interface control: encoding of affirmative and negative thinking. Front Neurosci 2013; 7:23. [PMID: 23471568 PMCID: PMC3590492 DOI: 10.3389/fnins.2013.00023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 02/11/2013] [Indexed: 11/30/2022] Open
Abstract
The aim of the study was to investigate conditioned electroencephalography (EEG) responses to factually correct and incorrect statements in order to enable binary communication by means of a brain-computer interface (BCI). In two experiments with healthy participants true and false statements (serving as conditioned stimuli, CSs) were paired with two different tones which served as unconditioned stimuli (USs). The features of the USs were varied and tested for their effectiveness to elicit differentiable conditioned reactions (CRs). After acquisition of the CRs, these CRs to true and false statements were classified offline using a radial basis function kernel support vector machine. A mean single-trial classification accuracy of 50.5% was achieved for differentiating conditioned “yes” versus “no” thinking and mean accuracies of 65.4% for classification of “yes” and 68.8% for “no” thinking (both relative to baseline) were found using the best US. Analysis of the area under the curve of the conditioned EEG responses revealed significant differences between conditioned “yes” and “no” answers. Even though improvements are necessary, these first results indicate that the semantic conditioning paradigm could be a useful basis for further research regarding BCI communication in patients in the complete locked-in state.
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Affiliation(s)
- Carolin A Ruf
- Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen Tübingen, Germany
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80
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Nambu I, Ebisawa M, Kogure M, Yano S, Hokari H, Wada Y. Estimating the intended sound direction of the user: toward an auditory brain-computer interface using out-of-head sound localization. PLoS One 2013; 8:e57174. [PMID: 23437338 PMCID: PMC3577758 DOI: 10.1371/journal.pone.0057174] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 01/18/2013] [Indexed: 11/18/2022] Open
Abstract
The auditory Brain-Computer Interface (BCI) using electroencephalograms (EEG) is a subject of intensive study. As a cue, auditory BCIs can deal with many of the characteristics of stimuli such as tone, pitch, and voices. Spatial information on auditory stimuli also provides useful information for a BCI. However, in a portable system, virtual auditory stimuli have to be presented spatially through earphones or headphones, instead of loudspeakers. We investigated the possibility of an auditory BCI using the out-of-head sound localization technique, which enables us to present virtual auditory stimuli to users from any direction, through earphones. The feasibility of a BCI using this technique was evaluated in an EEG oddball experiment and offline analysis. A virtual auditory stimulus was presented to the subject from one of six directions. Using a support vector machine, we were able to classify whether the subject attended the direction of a presented stimulus from EEG signals. The mean accuracy across subjects was 70.0% in the single-trial classification. When we used trial-averaged EEG signals as inputs to the classifier, the mean accuracy across seven subjects reached 89.5% (for 10-trial averaging). Further analysis showed that the P300 event-related potential responses from 200 to 500 ms in central and posterior regions of the brain contributed to the classification. In comparison with the results obtained from a loudspeaker experiment, we confirmed that stimulus presentation by out-of-head sound localization achieved similar event-related potential responses and classification performances. These results suggest that out-of-head sound localization enables us to provide a high-performance and loudspeaker-less portable BCI system.
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Affiliation(s)
- Isao Nambu
- Nagaoka University of Technology, Nagaoka, Niigata, Japan
| | | | - Masumi Kogure
- Nagaoka University of Technology, Nagaoka, Niigata, Japan
| | - Shohei Yano
- Nagaoka National College of Technology, Nagaoka, Niigata, Japan
| | | | - Yasuhiro Wada
- Nagaoka University of Technology, Nagaoka, Niigata, Japan
- * E-mail:
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81
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Schreuder M, Thurlings ME, Brouwer AM, Van Erp JBF, Tangermann M. Exploring the use of tactile feedback in an ERP-based auditory BCI. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2012:6707-10. [PMID: 23367468 DOI: 10.1109/embc.2012.6347533] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Giving direct, continuous feedback on a brain state is common practice in motor imagery based brain-computer interfaces (BCI), but has not been reported for BCIs based on event-related potentials (ERP), where feedback is only given once after a sequence of stimuli. Potentially, direct feedback could allow the user to adjust his strategy during a running trial to obtain the required response. In order to test the usefulness of such feedback, directionally congruent vibrotactile feedback was given during an online auditory BCI experiment. Users received either no feedback, short feedback pulses or continuous feedback. The feedback conditions showed reduced performance both on a behavioral task and in terms of classification accuracy. Several explanations are discussed that give interesting starting points for further research on this topic.
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Affiliation(s)
- Martijn Schreuder
- BBCI Group of the Machine Learning Department, Berlin Institute of Technology, Berlin, Germany
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82
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Lulé D, Noirhomme Q, Kleih SC, Chatelle C, Halder S, Demertzi A, Bruno MA, Gosseries O, Vanhaudenhuyse A, Schnakers C, Thonnard M, Soddu A, Kübler A, Laureys S. Probing command following in patients with disorders of consciousness using a brain–computer interface. Clin Neurophysiol 2013; 124:101-6. [DOI: 10.1016/j.clinph.2012.04.030] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 02/27/2012] [Accepted: 04/13/2012] [Indexed: 12/13/2022]
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83
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Xu H, Zhang D, Ouyang M, Hong B. Employing an active mental task to enhance the performance of auditory attention-based brain–computer interfaces. Clin Neurophysiol 2013; 124:83-90. [DOI: 10.1016/j.clinph.2012.06.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Revised: 06/12/2012] [Accepted: 06/13/2012] [Indexed: 11/25/2022]
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84
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Hill NJ, Moinuddin A, Häuser AK, Kienzle S, Schalk G. Communication and control by listening: toward optimal design of a two-class auditory streaming brain-computer interface. Front Neurosci 2012; 6:181. [PMID: 23267312 PMCID: PMC3525941 DOI: 10.3389/fnins.2012.00181] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 11/30/2012] [Indexed: 11/30/2022] Open
Abstract
Most brain-computer interface (BCI) systems require users to modulate brain signals in response to visual stimuli. Thus, they may not be useful to people with limited vision, such as those with severe paralysis. One important approach for overcoming this issue is auditory streaming, an approach whereby a BCI system is driven by shifts of attention between two simultaneously presented auditory stimulus streams. Motivated by the long-term goal of translating such a system into a reliable, simple yes-no interface for clinical usage, we aim to answer two main questions. First, we asked which of two previously published variants provides superior performance: a fixed-phase (FP) design in which the streams have equal period and opposite phase, or a drifting-phase (DP) design where the periods are unequal. We found FP to be superior to DP (p = 0.002): average performance levels were 80 and 72% correct, respectively. We were also able to show, in a pilot with one subject, that auditory streaming can support continuous control and neurofeedback applications: by shifting attention between ongoing left and right auditory streams, the subject was able to control the position of a paddle in a computer game. Second, we examined whether the system is dependent on eye movements, since it is known that eye movements and auditory attention may influence each other, and any dependence on the ability to move one’s eyes would be a barrier to translation to paralyzed users. We discovered that, despite instructions, some subjects did make eye movements that were indicative of the direction of attention. However, there was no correlation, across subjects, between the reliability of the eye movement signal and the reliability of the BCI system, indicating that our system was configured to work independently of eye movement. Together, these findings are an encouraging step forward toward BCIs that provide practical communication and control options for the most severely paralyzed users.
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Affiliation(s)
- N Jeremy Hill
- New York State Department of Health, Wadsworth Center Albany, NY, USA
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85
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Maddox RK, Cheung W, Lee AKC. Selective attention in an overcrowded auditory scene: implications for auditory-based brain-computer interface design. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2012; 132:EL385-EL390. [PMID: 23145699 PMCID: PMC3482251 DOI: 10.1121/1.4757696] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 09/17/2012] [Indexed: 05/29/2023]
Abstract
Listeners are good at attending to one auditory stream in a crowded environment. However, is there an upper limit of streams present in an auditory scene at which this selective attention breaks down? Here, participants were asked to attend one stream of spoken letters amidst other letter streams. In half of the trials, an initial primer was played, cueing subjects to the sound configuration. Results indicate that performance increases with token repetitions. Priming provided a performance benefit, suggesting that stream selection, not formation, is the bottleneck associated with attention in an overcrowded scene. Results' implications for brain-computer interfaces are discussed.
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Affiliation(s)
- Ross K Maddox
- Department of Speech and Hearing Sciences, and Institute for Learning and Brain Sciences, University of Washington, Seattle, Washington 98195, USA.
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Käthner I, Ruf CA, Pasqualotto E, Braun C, Birbaumer N, Halder S. A portable auditory P300 brain-computer interface with directional cues. Clin Neurophysiol 2012; 124:327-38. [PMID: 22959257 DOI: 10.1016/j.clinph.2012.08.006] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 08/08/2012] [Accepted: 08/09/2012] [Indexed: 10/27/2022]
Abstract
OBJECTIVES The main objective of the current study was to implement and evaluate a P300 based brain-computer interface (BCI) speller that uses directional cues of auditory stimuli, which are presented over headphones. The interstimulus interval (ISI) was successively reduced to determine the optimal combination of speed and accuracy. The study further aimed at quantifying the differences in subjective workload between the auditory and the visual P300 spelling application. The influence of workload, mood and motivation on BCI performance and P300 amplitude was investigated. METHODS Twenty healthy participants performed auditory and visual spelling tasks in an EEG experiment with online feedback. RESULTS Sixteen of twenty participants performed at or above a level necessary for satisfactory communication (≥70% spelling accuracy) with the auditory BCI. Average bit rates of up to 2.76 bits/min (best subject 7.43 bits/min) were achieved. A significantly higher workload was reported for the auditory speller compared to the visual paradigm. Motivation significantly influenced P300 amplitude at Pz in the auditory condition. CONCLUSIONS The results of the online study suggest that the proposed paradigm offers a means of communication for most healthy users. SIGNIFICANCE The described auditory BCI can serve as a communication channel for completely paralyzed patients.
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87
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van der Waal M, Severens M, Geuze J, Desain P. Introducing the tactile speller: an ERP-based brain-computer interface for communication. J Neural Eng 2012; 9:045002. [PMID: 22831906 DOI: 10.1088/1741-2560/9/4/045002] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In this study, a tactile speller was developed and compared with existing visual speller paradigms in terms of classification performance and elicited event-related potentials (ERPs). The fingertips of healthy participants were stimulated with short mechanical taps while electroencephalographic activity was measured. The letters of the alphabet were allocated to different fingers and subjects could select one of the fingers by silently counting the number of taps on that finger. The offline and online performance of the tactile speller was compared to the overt and covert attention visual matrix speller and the covert attention Hex-o-Spell speller. For the tactile speller, binary target versus non-target classification accuracy was 67% on average. Classification and decoding accuracies of the tactile speller were lower than the overt matrix speller, but higher than the covert matrix speller, and similar to Hex-o-Spell. The average maximum information transfer rate of the tactile speller was 7.8 bits min(-1) (1.51 char min(-1)), with the best subject reaching a bit-rate of 27 bits min(-1) (5.22 char min(-1)). An increased amplitude of the P300 ERP component was found in response to attended stimuli versus unattended stimuli in all speller types. In addition, the tactile and overt matrix spellers also used the N2 component for discriminating between targets and non-targets. Overall, this study shows that it is possible to use a tactile speller for communication. The tactile speller provides a useful alternative to the visual speller, especially for people whose eye gaze is impaired.
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Affiliation(s)
- Marjolein van der Waal
- Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
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88
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Schaeff S, Treder MS, Venthur B, Blankertz B. Exploring motion VEPs for gaze-independent communication. J Neural Eng 2012; 9:045006. [PMID: 22832017 DOI: 10.1088/1741-2560/9/4/045006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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89
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Höhne J, Krenzlin K, Dähne S, Tangermann M. Natural stimuli improve auditory BCIs with respect to ergonomics and performance. J Neural Eng 2012; 9:045003. [PMID: 22831919 DOI: 10.1088/1741-2560/9/4/045003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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90
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Tangermann M, Müller KR, Aertsen A, Birbaumer N, Braun C, Brunner C, Leeb R, Mehring C, Miller KJ, Müller-Putz GR, Nolte G, Pfurtscheller G, Preissl H, Schalk G, Schlögl A, Vidaurre C, Waldert S, Blankertz B. Review of the BCI Competition IV. Front Neurosci 2012; 6:55. [PMID: 22811657 PMCID: PMC3396284 DOI: 10.3389/fnins.2012.00055] [Citation(s) in RCA: 347] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Accepted: 03/30/2012] [Indexed: 11/13/2022] Open
Abstract
The BCI competition IV stands in the tradition of prior BCI competitions that aim to provide high quality neuroscientific data for open access to the scientific community. As experienced already in prior competitions not only scientists from the narrow field of BCI compete, but scholars with a broad variety of backgrounds and nationalities. They include high specialists as well as students. The goals of all BCI competitions have always been to challenge with respect to novel paradigms and complex data. We report on the following challenges: (1) asynchronous data, (2) synthetic, (3) multi-class continuous data, (4) session-to-session transfer, (5) directionally modulated MEG, (6) finger movements recorded by ECoG. As after past competitions, our hope is that winning entries may enhance the analysis methods of future BCIs.
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Affiliation(s)
- Michael Tangermann
- Machine Learning Laboratory, Berlin Institute of Technology Berlin, Germany
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91
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Kaufmann T, Völker S, Gunesch L, Kübler A. Spelling is Just a Click Away - A User-Centered Brain-Computer Interface Including Auto-Calibration and Predictive Text Entry. Front Neurosci 2012; 6:72. [PMID: 22833713 PMCID: PMC3400942 DOI: 10.3389/fnins.2012.00072] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 04/30/2012] [Indexed: 11/13/2022] Open
Abstract
Brain–computer interfaces (BCI) based on event-related potentials (ERP) allow for selection of characters from a visually presented character-matrix and thus provide a communication channel for users with neurodegenerative disease. Although they have been topic of research for more than 20 years and were multiply proven to be a reliable communication method, BCIs are almost exclusively used in experimental settings, handled by qualified experts. This study investigates if ERP–BCIs can be handled independently by laymen without expert support, which is inevitable for establishing BCIs in end-user’s daily life situations. Furthermore we compared the classic character-by-character text entry against a predictive text entry (PTE) that directly incorporates predictive text into the character-matrix. N = 19 BCI novices handled a user-centered ERP–BCI application on their own without expert support. The software individually adjusted classifier weights and control parameters in the background, invisible to the user (auto-calibration). All participants were able to operate the software on their own and to twice correctly spell a sentence with the auto-calibrated classifier (once with PTE, once without). Our PTE increased spelling speed and, importantly, did not reduce accuracy. In sum, this study demonstrates feasibility of auto-calibrating ERP–BCI use, independently by laymen and the strong benefit of integrating predictive text directly into the character-matrix.
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Affiliation(s)
- Tobias Kaufmann
- Department for Psychology I, Institute for Psychology, University of Würzburg Würzburg, Germany
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92
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Hill NJ, Schölkopf B. An online brain-computer interface based on shifting attention to concurrent streams of auditory stimuli. J Neural Eng 2012; 9:026011. [PMID: 22333135 PMCID: PMC3366495 DOI: 10.1088/1741-2560/9/2/026011] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We report on the development and online testing of an electroencephalogram-based brain-computer interface (BCI) that aims to be usable by completely paralysed users-for whom visual or motor-system-based BCIs may not be suitable, and among whom reports of successful BCI use have so far been very rare. The current approach exploits covert shifts of attention to auditory stimuli in a dichotic-listening stimulus design. To compare the efficacy of event-related potentials (ERPs) and steady-state auditory evoked potentials (SSAEPs), the stimuli were designed such that they elicited both ERPs and SSAEPs simultaneously. Trial-by-trial feedback was provided online, based on subjects' modulation of N1 and P3 ERP components measured during single 5 s stimulation intervals. All 13 healthy subjects were able to use the BCI, with performance in a binary left/right choice task ranging from 75% to 96% correct across subjects (mean 85%). BCI classification was based on the contrast between stimuli in the attended stream and stimuli in the unattended stream, making use of every stimulus, rather than contrasting frequent standard and rare 'oddball' stimuli. SSAEPs were assessed offline: for all subjects, spectral components at the two exactly known modulation frequencies allowed discrimination of pre-stimulus from stimulus intervals, and of left-only stimuli from right-only stimuli when one side of the dichotic stimulus pair was muted. However, attention modulation of SSAEPs was not sufficient for single-trial BCI communication, even when the subject's attention was clearly focused well enough to allow classification of the same trials via ERPs. ERPs clearly provided a superior basis for BCI. The ERP results are a promising step towards the development of a simple-to-use, reliable yes/no communication system for users in the most severely paralysed states, as well as potential attention-monitoring and -training applications outside the context of assistive technology.
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Affiliation(s)
- N J Hill
- Wadsworth Center, New York State Department of Health, Albany, NY, USA.
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93
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Tangermann M, Hohne J, Stecher H, Schreuder M. No surprise--sequence event-related potentials for brain-computer interfaces. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2012:2501-2504. [PMID: 23366433 DOI: 10.1109/embc.2012.6346472] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
INTRODUCTION In the field of Brain-Computer Interfaces (BCI), the original two-class oddball paradigm has been extended to multiple stimuli with balanced probabilities and random presentation sequences. Exploiting the differences between standard and deviant ERP responses, these multi-class paradigms are suitable for communication and control. METHODS The present study investigates the effect of giving up the randomness of stimulation sequences in favor of a repeated, predictable pattern. Data of healthy subjects (n=10) who performed a single session with a 6-class spatial auditory ERP paradigm were analyzed offline. Their auditory evoked potentials (AEP) resulting from the potentially simpler task (using fixed sequences) are compared with the AEP evoked by pseudo-randomized stimulation sequences. RESULTS Class-discriminative EEG responses between target and non-target stimuli were observed for both conditions. The binary classification error estimated for standard epochs of was comparable for both conditions (random: 24%, fixed: 25%). Expanding the standard epochs to include pre-stimulus intervals, we found that the regular structure of the fixed sequence can be exploited. Compared to the standard epoch, the MSE improves by 7%, while in the random condition an improvement could not be observed.
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Affiliation(s)
- Michael Tangermann
- Dept. Machine Learning, Berlin Institute of Technology (TU Berlin), Berlin, Germany. michael.tangermann at tu-berlin.de
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Schettini F, Aloise F, Arico P, Salinari S, Mattia D, Cincotti F. Control or no-control? Reducing the gap between brain-computer interface and classical input devices. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2012:1815-1818. [PMID: 23366264 DOI: 10.1109/embc.2012.6346303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In order to improve Brain Computer Interface usability for real life context, they should be able to adapt their speed to the user's current psychophysical state and to understand from the ongoing EEG when he/she intends to suspend the control. In this work we evaluated an asynchronous classifier which provides these feature with 20 healthy subjects, who were engaged in an environmental control task or in a spelling task. We also demonstrated how the proposed classifier can improve communication efficiency with respect to classical synchronous classifiers.
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