@article{KaethnerKueblerHalder2015, author = {K{\"a}thner, Ivo and K{\"u}bler, Andrea and Halder, Sebastian}, title = {Rapid P300 brain-computer interface communication with a head-mounted display}, series = {Frontiers in Neuroscience}, volume = {9}, journal = {Frontiers in Neuroscience}, number = {207}, doi = {10.3389/fnins.2015.00207}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148520}, year = {2015}, abstract = {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.}, language = {en} } @phdthesis{Real2015, author = {Real, Ruben}, title = {Living with severe motor impairments - from consciousness to quality of life}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-138562}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {The impact of acquired severe motor impairments is pervasive and may lead to a complete loss of communication and voluntary motor control, rendering the patient behaviourally unresponsive. In routine clinical care it may thus be unclear, whether some of these patients are even conscious. Given that finding a cure is unlikely, care focuses on providing the best possible quality of life (QoL), and knowing its predictors might contribute to that aim. Patients who still can communicate often report a high QoL, and several predictors have been identified. However, many instruments used to assess QoL require at least residual verbal and motor abilities. Thus, a method to assess QoL independent of these requirements is desirable. In addition, many instruments assume QoL to be temporarily stable, and little information is available on predictors of instantaneous QoL, i.e. QoL as it fluctuates from moment to moment throughout the day.}, subject = {Myatrophische Lateralsklerose}, language = {en} } @phdthesis{Kaethner2015, author = {K{\"a}thner, Ivo R. J.}, title = {Auditory and visual brain-computer interfaces as communication aids for persons with severe paralysis}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-135477}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2015}, abstract = {Brain-computer interfaces (BCIs) could provide a muscle-independent communication channel to persons with severe paralysis by translating brain activity into device commands. As a means of communication, in particular BCIs based on event-related potentials (ERPs) as control signal have been researched. Most of these BCIs rely on visual stimulation and have been investigated with healthy participants in controlled laboratory environments. In proof-of-principle studies targeted end users gained control over BCI systems; however, these systems are not yet established as an assistive technology for persons who would most benefit from them. The main aim of this thesis is to advance the usability of ERP-BCIs for target users. To this end, five studies with BCIs have been conducted that enabled users to communicate by focusing their attention on external stimuli. Two studies were conducted in order to demonstrate the advantages and to further improve the practical application of visual BCIs. In the first study, mental workload was experimentally manipulated during prolonged BCI operation. The study showed the robustness of the visual ERP-BCI since users maintained a satisfactory level of control despite constant distraction in the form of background noise. Moreover, neurophysiological markers that could potentially serve as indicators of high mental workload or fatigue were revealed. This is a first step towards future applications in which the BCI could adapt to the mental state of the user (e.g. pauses if high mental workload is detected to prevent false selections). In the second study, a head-mounted display (HMD), which assures that stimuli are presented in the field of view of the user, was evaluated. High accuracies and information transfer rates, similar to a conventional display, were achieved by healthy participants during a spelling task. Furthermore, a person in the locked-in state (LIS) gained control over the BCI using the HMD. The HMD might be particularly suited for initial communication attempts with persons in the LIS in situations, where mounting a conventional monitor is difficult or not feasible. Visual ERP-BCIs could prove valuable for persons with residual control over eye muscles and sufficient vision. However, since a substantial number of target users have limited control over eye movements and/or visual impairments, BCIs based on non-visual modalities are required. Therefore, a main aspect of this thesis was to improve an auditory paradigm that should enable motor impaired users to spell by focusing attention on different tones. The two conducted studies revealed that healthy participants were able to achieve high spelling performance with the BCI already in the first session and stress the importance of the choice of the stimulus material. The employed natural tones resulted in an increase in performance compared to a previous study that used artificial tones as stimuli. Furthermore, three out of five users with a varying degree of motor impairments could gain control over the system within the five conducted sessions. Their performance increased significantly from the first to the fifth session - an effect not previously observed for visual ERP-BCIs. Hence, training is particularly important when testing auditory multiclass BCIs with potential users. A prerequisite for user satisfaction is that the BCI technology matches user requirements. In this context, it is important to compare BCIs with already established assistive technology. Thus, the fifth study of this dissertation evaluated gaze dependent methods (EOG, eye tracking) as possible control signals for assistive technology and a binary auditory BCI with a person in the locked-in state. The study participant gained control over all tested systems and rated the ease of use of the BCI as the highest among the tested alternatives, but also rated it as the most tiring due to the high amount of attention that was needed for a simple selection. Further efforts are necessary to simplify operation of the BCI. The involvement of end users in all steps of the design and development process of BCIs will increase the likelihood that they can eventually be used as assistive technology in daily life. The work presented in this thesis is a substantial contribution towards the goal of re-enabling communication to users who cannot rely on motor activity to convey their thoughts.}, subject = {Gehirn-Computer Schnittstelle}, language = {en} } @article{SimonKaethnerRufetal.2015, author = {Simon, Nadine and K{\"a}thner, Ivo and Ruf, Carolin A. and Pasqualotto, Emanuele and K{\"u}bler, Andrea and Halder, Sebastian}, title = {An auditory multiclass brain-computer interface with natural stimuli: Usability evaluation with healthy participants and a motor impaired end user}, series = {Frontiers in Human Neuroscience}, volume = {8}, journal = {Frontiers in Human Neuroscience}, number = {1039}, doi = {10.3389/fnhum.2014.01039}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-126450}, year = {2015}, abstract = {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.}, language = {en} } @article{KleihHerwegKaufmannetal.2015, author = {Kleih, Sonja C. and Herweg, Andreas and Kaufmann, Tobias and Staiger-S{\"a}lzer, Pit and Gerstner, Natascha and K{\"u}bler, Andrea}, title = {The WIN-speller: a new intuitive auditory brain-computer interface spelling application}, series = {Frontiers in Neuroscience}, volume = {9}, journal = {Frontiers in Neuroscience}, doi = {10.3389/fnins.2015.00346}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-125972}, pages = {346}, year = {2015}, abstract = {The objective of this study was to test the usability of a new auditory Brain-Computer Interface (BCI) application for communication. We introduce a word based, intuitive auditory spelling paradigm the WIN-speller. In the WIN-speller letters are grouped by words, such as the word KLANG representing the letters A, G, K, L, and N. Thereby, the decoding step between perceiving a code and translating it to the stimuli it represents becomes superfluous. We tested 11 healthy volunteers and four end-users with motor impairment in the copy spelling mode. Spelling was successful with an average accuracy of 84\% in the healthy sample. Three of the end-users communicated with average accuracies of 80\% or higher while one user was not able to communicate reliably. Even though further evaluation is required, the WIN-speller represents a potential alternative for BCI based communication in end-users.}, language = {en} }