TY  - JOUR
A1  - Simon, Nadine
A1  - Käthner, Ivo
A1  - Ruf, Carolin A.
A1  - Pasqualotto, Emanuele
A1  - Kübler, Andrea
A1  - Halder, Sebastian
T1  - An auditory multiclass brain-computer interface with natural stimuli: Usability evaluation with healthy participants and a motor impaired end user
JF  - Frontiers in Human Neuroscience
N2  - Brain-computer interfaces (BCIs) can serve as muscle independent communication aids. Persons, who are unable to control their eye muscles (e.g., in the completely locked-in state) or have severe visual impairments for other reasons, need BCI systems that do not rely on the visual modality. For this reason, BCIs that employ auditory stimuli were suggested. In this study, a multiclass BCI spelling system was implemented that uses animal voices with directional cues to code rows and columns of a letter matrix. To reveal possible training effects with the system, 11 healthy participants performed spelling tasks on 2 consecutive days. In a second step, the system was tested by a participant with amyotrophic lateral sclerosis (ALS) in two sessions. In the first session, healthy participants spelled with an average accuracy of 76% (3.29 bits/min) that increased to 90% (4.23 bits/min) on the second day. Spelling accuracy by the participant with ALS was 20% in the first and 47% in the second session. The results indicate a strong training effect for both the healthy participants and the participant with ALS. While healthy participants reached high accuracies in the first session and second session, accuracies for the participant with ALS were not sufficient for satisfactory communication in both sessions. More training sessions might be needed to improve spelling accuracies. The study demonstrated the feasibility of the auditory BCI with healthy users and stresses the importance of training with auditory multiclass BCIs, especially for potential end-users of BCI with disease.
KW  - P300
KW  - EEG
KW  - auditory BCI
KW  - brain-computer interface
KW  - communication
KW  - ALS
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-126450
VL  - 8
IS  - 1039
ER  - 
TY  - JOUR
A1  - Martens, Suzanne
A1  - Bensch, Michael
A1  - Halder, Sebastian
A1  - Hill, Jeremy
A1  - Nijboer, Femke
A1  - Ramos-Murguialday, Ander
A1  - Schoelkopf, Bernhard
A1  - Birbaumer, Niels
A1  - Gharabaghi, Alireza
T1  - Epidural electrocorticography for monitoring of arousal in locked-in state
JF  - Frontiers in Human Neuroscience
N2  - Electroencephalography (EEG) often fails to assess both the level (i.e., arousal) and the content (i.e., awareness) of pathologically altered consciousness in patients without motor responsiveness. This might be related to a decline of awareness, to episodes of low arousal and disturbed sleep patterns, and/or to distorting and attenuating effects of the skull and intermediate tissue on the recorded brain signals. Novel approaches are required to overcome these limitations. We introduced epidural electrocorticography (ECoG) for monitoring of cortical physiology in a late-stage amytrophic lateral sclerosis patient in completely locked-in state (CLIS) Despite long-term application for a period of six months, no implant related complications occurred. Recordings from the left frontal cortex were sufficient to identify three arousal states. Spectral analysis of the intrinsic oscillatory activity enabled us to extract state-dependent dominant frequencies at <4, similar to 7 and similar to 20 Hz, representing sleep-like periods, and phases of low and elevated arousal, respectively. In the absence of other biomarkers, ECoG proved to be a reliable tool for monitoring circadian rhythmicity, i.e., avoiding interference with the patient when he was sleeping and exploiting time windows of responsiveness. Moreover, the effects of interventions addressing the patient's arousal, e.g., amantadine medication, could be evaluated objectively on the basis of physiological markers, even in the absence of behavioral parameters. Epidural ECoG constitutes a feasible trade-off between surgical risk and quality of recorded brain signals to gain information on the patient's present level of arousal. This approach enables us to optimize the timing of interactions and medical interventions, all of which should take place when the patient is in a phase of high arousal. Furthermore, avoiding low responsiveness periods will facilitate measures to implement alternative communication pathways involving brain-computer interfaces (BCI).
KW  - temporal-lobe epilepsy
KW  - neuroprosthetic devices
KW  - brain computer interface
KW  - event-related potentials
KW  - intraoperative electrocoicography
KW  - electrocorticography
KW  - epidural recording
KW  - locked-in state
KW  - coma
KW  - consciousness
KW  - paralyzed patients
KW  - EEG
KW  - sleep
KW  - communication
KW  - frequencies
KW  - amyotrophic-lateral-sclerosis
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-114863
VL  - 8
ER  -