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See detailThe auditory P300-based single-switch brain–computer interface:Paradigm transition from healthy subjects to minimally consciouspatients
Pokorny, Christoph; Klobassa, Daniela; Pichler, Gerald et al

in Artificial Intelligence in Medicine (2013), 59(2), 81-90

Objective: Within this work an auditory P300 brain–computer interface based on tone stream segregation,which allows for binary decisions, was developed and evaluated.Methods and materials: Two tone ... [more ▼]

Objective: Within this work an auditory P300 brain–computer interface based on tone stream segregation,which allows for binary decisions, was developed and evaluated.Methods and materials: Two tone streams consisting of short beep tones with infrequently appearingdeviant tones at random positions were used as stimuli. This paradigm was evaluated in 10 healthysubjects and applied to 12 patients in a minimally conscious state (MCS) at clinics in Graz, Würzburg,Rome, and Liège. A stepwise linear discriminant analysis classifier with 10 × 10 cross-validation was usedto detect the presence of any P300 and to investigate attentional modulation of the P300 amplitude.Results: The results for healthy subjects were promising and most classification results were better thanrandom. In 8 of the 10 subjects, focused attention on at least one of the tone streams could be detectedon a single-trial basis. By averaging 10 data segments, classification accuracies up to 90.6 % could bereached. However, for MCS patients only a small number of classification results were above chance leveland none of the results were sufficient for communication purposes. Nevertheless, signs of consciousnesswere detected in 9 of the 12 patients, not on a single-trial basis, but after averaging of all correspondingdata segments and computing significant differences. These significant results, however, strongly variedacross sessions and conditions.Conclusion: This work shows the transition of a paradigm from healthy subjects to MCS patients. Promisingresults with healthy subjects are, however, no guarantee of good results with patients. Therefore, moreinvestigations are required before any definite conclusions about the usability of this paradigm for MCSpatients can be drawn. Nevertheless, this paradigm might offer an opportunity to support bedside clinicalassessment of MCS patients and eventually, to provide them with a means of communication. [less ▲]

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See detailProbing command following in patients with disorders of consciousness using a brain-computer interface.
Lule, Dorothee; Noirhomme, Quentin ULg; Kleih, Sonja C. et al

in Clinical Neurophysiology (2013), 124(1), 101-6

OBJECTIVE: To determine if brain-computer interfaces (BCIs) could serve as supportive tools for detecting consciousness in patients with disorders of consciousness by detecting response to command and ... [more ▼]

OBJECTIVE: To determine if brain-computer interfaces (BCIs) could serve as supportive tools for detecting consciousness in patients with disorders of consciousness by detecting response to command and communication. METHODS: We tested a 4-choice auditory oddball EEG-BCI paradigm on 16 healthy subjects and 18 patients in a vegetative state/unresponsive wakefulness syndrome, in a minimally conscious state (MCS), and in locked-in syndrome (LIS). Subjects were exposed to 4 training trials and 10 -12 questions. RESULTS: Thirteen healthy subjects and one LIS patient were able to communicate using the BCI. Four of those did not present with a P3. One MCS patient showed command following with the BCI while no behavioral response could be detected at bedside. All other patients did not show any response to command and could not communicate with the BCI. CONCLUSION: The present study provides evidence that EEG based BCI can detect command following in patients with altered states of consciousness and functional communication in patients with locked-in syndrome. However, BCI approaches have to be simplified to increase sensitivity. SIGNIFICANCE: For some patients without any clinical sign of consciousness, a BCI might bear the potential to employ a "yes-no" spelling device offering the hope of functional interactive communication. [less ▲]

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See detailBrain-computer interface in disorders of consciousness: answering simple questions with a P3 speller
Noirhomme, Quentin ULg; Chatelle, Camille ULg; Kleih, Sonja et al

Poster (2010, June)

Objective: In the recovery from coma, the acquisition of command following represents an important milestone, indicating emergence from the vegetative state (Schnakers et al., 2009). In some patients ... [more ▼]

Objective: In the recovery from coma, the acquisition of command following represents an important milestone, indicating emergence from the vegetative state (Schnakers et al., 2009). In some patients, recovery of consciousness may precede motor recovery. Brain-computer interfaces (BCI) might permit these patients to show non-motor dependent signs of awareness and in a next step might enable communication. This study aimed at testing to what extent an EEG-based BCI could help detecting signs of awareness and communication in disorders of consciousness. We employed a P300 based BCI where healthy volunteers and patients with locked-in syndrome and in a minimally conscious state were asked to answer yes or no to simple questions by paying attention to one out of four auditorily presented stimuli (‘yes’, ‘no’, ‘stop’, ‘go’). Methods: We studied 13 patients with a minimally conscious state (MCS, 5 TBI – 8 anoxic, mean time post injury 70±109 months; mean age 42 ± 21) and 2 in pseudo-coma or locked in syndrome (LIS; brainstem stroke, time post injury 26 and 46 months; aged 63 and 29)) and 16 healthy controls (aged 45±19). Patients were evaluated using the Coma Recovery Scale Revised (CRS-R). An auditory P300 four choice speller paradigm (Furdea et al., 2009) based on the BCI2000 system (Schalk et al., 2004) was used. 16-Channel EEG was recorded using a g.tec USBAmp amplifier. A trial constituted of 15 presentation of four sounds the order of presentation being pseudo-randomized (sound duration: ~400ms; inter-stimulus interval: ~600ms). After a training session of 4 trials, patients and healthy subjects were required to answer 10 or 12 questions, respectively. Questions were of the following kind: “Is your name Quentin?”, “Is your mother’s name Dorothée?”. A stepwise linear discriminant analysis based on the training session was used to classify the data and to provide online feedback. Offline, all training and testing sequences were pooled. Sequences with artifacts were discarded and a leave-one-out approach was used to classify the data. Results: Healthy subjects presented a mean correct response rate of 73% online and 93% offline. Note that online classification failed for one control subject due to a presumed change in cognitive strategy between training and testing sessions. LIS patients showed a correct response rate of 30 and 60% (online) and 36 and 79% (offline). Three MCS patients had a correct response rate of ≥50% offline (10, 18, 0% online and 50, 53, 57% offline). Two of these three patients did not show any command following at the bedside. The 10 remaining MCS cases showed online and offline correct answers <50% (mean 33±9% online and 25±13% offline). Conclusion: Our auditory P300-based BCI permitted functional interactive communication in 15/16 controls (online) and in all offline. Our data obtained in patients with locked-in syndrome and disorders of consciousness demonstrate the potential clinical usefulness of the technique following coma but also show lower accuracy in patients as compared to healthy volunteers. This might be due to fluctuating attentional levels and exhaustibility in the MCS and to the suboptimal EEG recording quality due to movement, ocular and respiration artifacts in these challenging patients. Further algorithmic developments should include automatic artifact detection and single trial classification. Despite the need for further improvement in BCI devices adapted to post-coma patients, our results already indicate that MCS patients without any clinical sign of command-following can employ a yes-no speller offering the hope of functional interactive communication and a possibility for decision making and autonomy. Bibliography Furdea A, Halder S, Krusienski DJ, Bross D, Nijboer F, Birbaumer N, Kübler A, 2009, An auditory oddball (P300) spelling system for brain-computer interfaces, Psychophysiology. May; 46(3):617-25. Schalk G., McFarland D.J., Hinterberger T., Birbaumer N., and Wolpaw J.R. 2004, BCI2000: A General-Purpose Brain-Computer Interface (BCI) System, IEEE Trans Biomed Eng, 51(6). Schnakers C, Vanhaudenhuyse A, Giacino J, Ventura; Boly M, Majerus S, Moonen G, Laureys S, 2009, Diagnostic accuracy of the vegetative and minimally conscious state: Clinical consensus versus standardized neurobehavioral assessment, BMC Neurology, 9 (35). [less ▲]

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See detailLife can be worth living in locked-in syndrome
Lule, Dorothee; Zickler, K.; Hacker, S. et al

in Progress in Brain Research (2009), 177

The locked-in syndrome (LIS) describes patients who are awake and conscious but severely deefferented leaving the patient in a state of almost complete immobility and loss of verbal communication. The ... [more ▼]

The locked-in syndrome (LIS) describes patients who are awake and conscious but severely deefferented leaving the patient in a state of almost complete immobility and loss of verbal communication. The etiology ranges from acute (e.g., brainstem stroke, which is the most frequent cause of LIS) to chronic causes (e.g., amyotrophic lateral sclerosis; ALS). In this article we review and present new data on the psychosocial adjustment to LIS. We refer to quality of life (QoL) and the degree of depressive symptoms as a measure of psychosocial adjustment. Various studies suggest that despite their extreme motor impairment, a significant number of LIS patients maintain a good QoL that seems unrelated to their state of physical functioning. Likewise, depression is not predicted by the physical state of the patients. A successful psychological adjustment to the disease was shown to be related to problem-oriented coping strategies, like seeking for information, and emotional coping strategies like denial--the latter may, nevertheless, vary with disease stage. Perceived social support seems to be the strongest predictor of psychosocial adjustment. QoL in LIS patients is often in the same range as in age-matched healthy individuals. Interestingly, there is evidence that significant others, like primary caregivers or spouses, rate LIS patients' QoL significantly lower than the patients themselves. With regard to depressed mood, ALS patients without symptoms focus significantly more often on internal factors that can be retained in the course of the disease contrary to patients with depressive symptoms who preferably name external factors as very important, such as health, which will degrade in the course of the disease. Typically, ALS patients with a higher degree of depressive symptoms experience significantly less "very pleasant" situations. The herein presented data strongly question the assumption among doctors, health-care workers, lay persons, and politicians that severe motor disability necessarily is intolerable and leads to end-of-life decisions or euthanasia. Existing evidence supports that biased clinicians provide less-aggressive medical treatment in LIS patients. Thus, psychological treatment for depression, effective strategies for coping with the disease, and support concerning the maintenance of the social network are needed to cope with the disease. Novel communication devices and assistive technology now offers an increasing number of LIS patients to resume a meaningful life and an active role in society. [less ▲]

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