TY - JOUR A1 - Käthner, Ivo A1 - Kübler, Andrea A1 - Halder, Sebastian T1 - Rapid P300 brain-computer interface communication with a head-mounted display JF - Frontiers in Neuroscience N2 - Visual ERP (P300) based brain-computer interfaces (BCIs) allow for fast and reliable spelling and are intended as a muscle-independent communication channel for people with severe paralysis. However, they require the presentation of visual stimuli in the field of view of the user. A head-mounted display could allow convenient presentation of visual stimuli in situations, where mounting a conventional monitor might be difficult or not feasible (e.g., at a patient's bedside). To explore if similar accuracies can be achieved with a virtual reality (VR) headset compared to a conventional flat screen monitor, we conducted an experiment with 18 healthy participants. We also evaluated it with a person in the locked-in state (LIS) to verify that usage of the headset is possible for a severely paralyzed person. Healthy participants performed online spelling with three different display methods. In one condition a 5 x 5 letter matrix was presented on a conventional 22 inch TFT monitor. Two configurations of the VR headset were tested. In the first (glasses A), the same 5 x 5 matrix filled the field of view of the user. In the second (glasses B), single letters of the matrix filled the field of view of the user. The participant in the LIS tested the VR headset on three different occasions (glasses A condition only). For healthy participants, average online spelling accuracies were 94% (15.5 bits/min) using three flash sequences for spelling with the monitor and glasses A and 96% (16.2 bits/min) with glasses B. In one session, the participant in the LIS reached an online spelling accuracy of 100% (10 bits/min) using the glasses A condition. We also demonstrated that spelling with one flash sequence is possible with the VR headset for healthy users (mean: 32.1 bits/min, maximum reached by one user: 71.89 bits/min at 100% accuracy). We conclude that the VR headset allows for rapid P300 BCI communication in healthy users and may be a suitable display option for severely paralyzed persons. KW - speller performance KW - face perception KW - stimulus KW - rapid BCI KW - locked-in state KW - P300 KW - head-mounted display KW - brain-computer interface Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148520 VL - 9 IS - 207 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 -