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  - 
TY  - JOUR
A1  - Real, Ruben G. L.
A1  - Kotchoubey, Boris
A1  - Kübler, Andrea
T1  - Studentized continuous  wavelet transform (t-CWT) in the analysis of individual ERPs: real and simulated EEG data
N2  - This study aimed at evaluating the performance of the Studentized Continuous Wavelet Transform (t-CWT) as a method for the extraction and assessment of event-related brain potentials (ERP) in data from a single subject. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of the t-CWT were assessed and compared to a variety of competing procedures using simulated EEG data at six low signal-to-noise ratios. Results show that the t-CWT combines high sensitivity and specificity with favorable PPV and NPV. Applying the t-CWT to authentic EEG data obtained from 14 healthy participants confirmed its high sensitivity. The t-CWT may thus be well suited for the assessment of weak ERPs in single-subject settings.
KW  - electroencephalogram
KW  - wavelet
KW  - EEG
KW  - t-CWT
KW  - significance
KW  - detection
KW  - ERP
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-113581
ER  -