@article{ErlbeckMochtyKuebleretal.2017,
  author    = {Erlbeck, Helena and Mochty, Ursula and K{\"u}bler, Andrea and Real, Ruben G. L.},
  title     = {Circadian course of the P300 ERP in patients with amyotrophic lateral sclerosis - implications for brain-computer interfaces (BCI)},
  series = {BMC Neurology},
  volume    = {17},
  journal   = {BMC Neurology},
  number    = {3},
  doi       = {10.1186/s12883-016-0782-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157423},
  year      = {2017},
  abstract  = {Background: Accidents or neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) can lead to progressing, extensive, and complete paralysis leaving patients aware but unable to communicate (locked-in state). Brain-computer interfaces (BCI) based on electroencephalography represent an important approach to establish communication with these patients. The most common BCI for communication rely on the P300, a positive deflection arising in response to rare events. To foster broader application of BCIs for restoring lost function, also for end-users with impaired vision, we explored whether there were specific time windows during the day in which a P300 driven BCI should be preferably applied. Methods: The present study investigated the influence of time of the day and modality (visual vs. auditory) on P300 amplitude and latency. A sample of 14 patients (end-users) with ALS and 14 healthy age matched volunteers participated in the study and P300 event-related potentials (ERP) were recorded at four different times (10, 12 am, 2, \& 4 pm) during the day. Results: Results indicated no differences in P300 amplitudes or latencies between groups (ALS patients v. healthy participants) or time of measurement. In the auditory condition, latencies were shorter and amplitudes smaller as compared to the visual condition. Conclusion: Our findings suggest applicability of EEG/BCI sessions in patients with ALS throughout normal waking hours. Future studies using actual BCI systems are needed to generalize these findings with regard to BCI effectiveness/efficiency and other times of day.},
  language  = {en}
}
@phdthesis{Erlbeck2015,
  author    = {Erlbeck, Helena},
  title     = {The event-related potentials Mismatch Negativity, P300, and N400: Effects of attentional modulation and application in patients with disorders of consciousness},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-121041},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {The present work comprises four studies dealing with the investigation of the auditory event-related potentials (ERP) Mismatch Negativity (MMN), P300, and N400 under different attentional instructions, and with their application in patients with disorders of consciousness (DOC) to assess residual cognitive functioning. In guided interviews (study 1), practitioners working with DOC patients stated their general interest in and an objective need for the complementation of current diagnostic procedures by reliable and valid ERP-based methods. Subsequently, in study 2, simple oddball and semantic paradigms were applied to 19 behaviorally non-responsive DOC patients revealing the presence of at least one ERP in eight patients investigated. In the third and fourth study, specific attentional effects on ERPs were investigated in healthy participants to define optimal instructions and stimulus parameters. In study 3, MMN and N400 amplitudes were assessed in 18 participants, and in study 4, MMN and P300 amplitudes were assessed in 32 participants. Both studies included an ignore task (attention on simultaneous visual stimuli), a passive task, and a focused task and revealed distinct attentional effects on P300 and N400 with largest amplitudes in the focused task, smaller ones in the passive task and no ERP in the ignore task. An MMN was elicited in all tasks, but still, amplitudes differed as a function of task. In addition, study 4 included oddball paradigms comprising several deviants in different dimensions. Higher amplitudes were found in this multifeature paradigm compared to traditional oddball paradigms and larger amplitudes were elicited by deviants highly different from standards. It is concluded that ERPs represent a promising tool to complement clinical assessment of DOC patients. Application of ERP paradigms should include focused instructions, especially when using semantic material. Furthermore, multifeature paradigms have been proven especially useful eliciting large amplitudes and allowing for the investigation of several dimensions of deviants at the same time.},
  subject      = {Bewusstseinsst{\"o}rung},
  language  = {en}
}
@article{ErlbeckKueblerKotchoubeyetal.2014,
  author    = {Erlbeck, Helena and K{\"u}bler, Andrea and Kotchoubey, Boris and Veser, Sandra},
  title     = {Task instructions modulate the attentional mode affecting the auditory MMN and the semantic N400},
  series = {Frontiers in Human Neuroscience},
  volume    = {8},
  journal   = {Frontiers in Human Neuroscience},
  number    = {654},
  doi       = {10.3389/fnhum.2014.00654},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-115553},
  year      = {2014},
  abstract  = {Event-related potentials (ERPs) have been proven to be a useful tool to complement clinical assessment and to detect residual cognitive functions in patients with disorders of consciousness. These ERPs are of ten recorded using passive or unspecific instructions. Patient data obtained this way are then compared to data from healthy participants, which are usually recorded using active instructions. The present study investigates the effect of attentive modulations and particularly the effect of activevs. passive instruction on the ERP components mismatch negativity (MMN) and N400. A sample of 18 healthy participants listened to three auditory paradigms: anoddball, aword priming, and a sentence paradigm. Each paradigm was presented three times with different instructions: ignoring auditory stimuli, passive listening, and focused attention on the auditory stimuli. After each task, the participants indicated their subjective effort. The N400 decreased from the focused task to the passive task, and was extinct in the ignore task. The MMN exhibited higher amplitudes in the focused and passive task compared to the ignore task. The data indicate an effect of attention on the supratemporal component of the MMN. Subjective effort was equally high in the passive and focused tasks but reduced in the ignore task. We conclude that passive listening during EEG recording is stressful and attenuates ERPs, which renders the interpretation of the results obtained in such conditions difficult.},
  language  = {en}
}