Brain-Computer Interfaces

Reading the mind and translating the thoughts into actions without acting have always been materials of which dreams and fairytales were made. Recent developments in human-machine interface (HMI) technology, however, open the door to make these dreams come true. New microchip design, microstimulation technology to interact with neuronal tissue, powerful computers, sophisticated signal detection algorithms and the rapidly growing field of neuroscience allow us to tap into a completely new application of interfaces, i.e. the restoration of lost motor or sensory function.

Brain-Computer Interfaces for communication and control

Brain-computer interfaces (BCI) are systems that allow us to translate in real-time the electrical activity of the brain in commands to control devices. They do not rely on muscular activity and can therefore provide communication and control for those who are severely paralyzed (locked-in) due to injury or disease. It has been shown that locked-in patients are able to achieve EEG controlled cursor or limb movement and patients have successfully communicated by means of a BCI.

The locked-in syndrome

Neurological diseases may lead to paralysis of the entire motor system restricting both verbal and nonverbal communication. The term locked-in refers to a state in which individuals are conscious and alert, but unable to use their muscles and therefore cannot communicate their needs, wishes, and emotions: the healthy brain is locked into a paralysed body. Causes of the locked-in syndrome may be stroke, traumatic brain injury, cerebral palsy, or degenerative neurological diseases such as amyotrophic lateral slcerosis.

Amyotrophic lateral sclerosis (ALS)

Amyotrophic lateral sclerosis is a progressive neurodegenerative disease of the motor system. The cause of the disease is yet to be fully understood and no curative treatment is available. It involves steadily progressive degeneration of central and peripheral motoneurons. Most often, paralysis begins with the lower extremities and then moves on to hands and arms, finally paralyzing breathing and swallowing and also facial muscles. In the final stage patients can only survive if they chose artificial ventilation.

From a healthy individual's point of view one might consider the quality of life in such patients very low. However, it has been repeatedly shown that quality of life can be maintained despite the physical decline. One of our patients who depends on artificial feeding and ventilation and whose motor control is restricted to eye blinks, stated ?life itself pushes for its success? rating his quality of life as good. Quality of life and the will to live in severely paralysed patients depend heavily on the ability to communicate. By circumventing the motor output, BCIs allow a person with restricted motor abilities to maintain communication and to control external devices.

Tools for Brain-Computer-Interfaces (TOBI)

TOBI is a large integrated European project and includes leading European groups in brain-computer interaction (BCI), human-computer interaction, intelligent robotics, and applied assistive technologies.
The project aims at developing practical technology for BCI that will improve the quality of life of disabled people and the effectiveness of rehabilitation. The application areas of the TOBI-systems are: Communication and Control, Motor Substitution, Entertainment and Motor Recovery.
For these purposes we will design non-invasive brain-computer-interface-prototypes that will be combined with existing assistive technologies and rehabilitation protocols. Non-invasive brain-computer-interfaces are based on electroencephalogram (EEG) signals. This technology records the electrical activity of the brain and translates them into device commands such as cursor control on a screen or neuroprosthetic control. In a hybrid approach users can fuse brain interaction and muscle-based interaction or can switch between different channels naturally.
An important issue of TOBI is the close integration of potential users in the evaluation of the new applications; from the assessment of the most urgent user needs up to the evaluation of the impact of the TOBI-system on the user´s quality of life.
The Institute of Medical Psychology and Behavioral Neurobiology in Tübingen is specifically involved in the definition of the conditions under which BCI training is optimal. Guidelines for user training will be developed that provide information under which applications, mental strategies, feedback, psychological and social conditions the TOBI-systems work best.

The Tübingen Project Team

Prof. Dr. Andrea Kübler

Dipl.-Psych. Sonja Kleih

Dipl.-Psych. Claudia Zickler

BCIs on the basis of the electrical activity of the brain (EEG)

The electical brain activity of the user is recorded by single or multiple electrodes from the scalp (EEG). Electrodes are connected to an amplifier that bandpass filters and amplifies the electrical signals of the users' brain. Different brain states of the user that convey a message can either be achieved by self-regulation of the relevant EEG features or are elicited by mental tasks or presentation of external visual or auditory stimuli. The designs to teach users to self-regulate their EEG is as follows: the relevant features of the EEG are extracted and translated in real time into cursor movement on a computer screen (visual feedback), a stream of tones (auditory feedback), or any other distinctly changing signal. Users are provided with on-line feedback of their EEG. Self-regulation of the EEG allows the user real-time control of a cursor in one or two dimensions. The acquired signals are digitized, extracted and a specific algorithm translates the extracted features into commands that represent the users' intent. These commands can either control effectors directly such as robotic arms or indirectly via cursor movement on a computer screen to activate switches for interaction with the environment or to select items, words, or letters from a menu for communication.

Brain-Orthosis-Interface

Non-invasive Brain-Computer-Interfaces for the restoration of hand movement in chronic stroke. In cooperation with the National Institute of Health (NIH), NINDS, Human Cortical Physiology Section (Prof. Leonardo Cohen)

A non-invasive Brain-Computer-Interface system was developed to improve hand function in chronic stroke. The system is presently used with a 270-channel magnetoencephalography or a multi-channel EEG-system. It can be combined with a rehabilitation robotic system from Robotica, Caesarea, Israel (email: "Samuel Faran" Samuel(at)motorika.com).

One third of all stroke patients do not recover paralyzed hand function after 1 or more years post-stroke. One third of stroke patients retain residual movements and one third improves considerably within the first year after stroke. The Brain-Computer Interface system developed here selects the most active MEG/EEG-channels of the ipsilesional sensory motor cortex and uses oscillatory activity of the mu (sensory motor rhythm) rhythm to activate a peripheral orthosis fixed to the patient?s paralyzed arm (see figure 1).

: Fig. 1. MEG-BCI for chronic stroke. Top: Patients observe their SMR-activity represented by the red curser on a screen (right part) after instructed to increase (top goal bar (not visible)) or decrease (lower goal bar) SMR. Increase closes and decrease opens the hand in 5 steps depending upon SMR 2 sec before. Bottom: Stroke patient with hand in orthosis in the MEG during training. Note that patients not only receive visual feedback from the feedback screen but also from watching and feeling their own paralysed hand moving

Patients are trained to imagine opening and closing of the hand or movements of the forearm and together with above-threshold activation of the selected ipsilesional sensor, the brain activity opens and closes the orthosis and the patient?s hand. Patients receive visual and kinesthetic feedback of their brain activity and of the hand movement. 90% of the patients are able to voluntarily control the orthosis and the hand in 70-90% of the trials after 20 hours of training. In the course of training ipsilesional brain activity increases, and spasticity decreases significantly, but hand movement without the orthosis does not improve. Present research combines physiotherapy with the hand rehabilitation robot of Robotika, Israel with the Brain-Computer Interface and transcranial dc-stimulation of the ipsilesional cortex. It is hypothesized that the combination of voluntary control of the paralyzed hand with the brain-computer-interface, the physiotherapy with the robot and improvement of cortical plasticity through transcranial dc-stimulation may allow generalization of the voluntary control of the orthosis to the contralesional hand.

(Supported by the Deutsche Forschungsgemeinschaft and the National Institute of Health).

Electrocortical activity for BCI (ECoG)

Patients in advanced disease stages may ask for implantation of the electrodes in the brain. With electrode grids we are able to measure the electrocorticogram (ECoG) from the cortical surface. With implanted electrodes brain communication may be learned faster and may be more flexible. Implantation is provided by the Department of Neurology (Prof. Tatagiba).

Contact

Prof. Dr. Niels Birbaumer, +49 7071 297 4219, niels.birbaumer(at)uni-tuebingen.de

New approach for communication in LIS and CLIS

The state in which patients are severely paralyzed with residual voluntary control over particular muscles (e.g. eye muscles, lips, fingers) is known as locked- in state (LIS). Patients may, however, develop the completely locked-in state (CLIS) in which all motor control is lost. These patients have the greatest need for a BCI to restore communication and interaction with the social environment. Over the last ten years it has been shown that patients with severe motor disability and also patients in the LIS are able to control a BCI (e.g. to select letters and thus to communicate). However, up to now there are no documented cases of CLIS patients communicating by means of BCI. Within this study we propose a new paradigm to enable basic yes/no communication. The employment of the auditory modality and of a paradigm which consumes less attentional resources and voluntary efforts may be an alternative for the LIS patients to learn BCI skills and to transfer the skills to the CLIS. The aim of the present study is therefore to train ALS patients with the BCI and to assess its usefulness for the achievement and maintenance of basic communication in CLIS.

Contact: Carolin Ruf + 49 (0) 7071 29 74222

Email: carolin.ruf(at)medizin.uni-tuebingen.de

Funding

National Institute of Health ( NIH grants HD30146 and EB00856.)

German Research Society (SFB 550)

Bundesministerium für Wissenschaft und Forschung (Bernstein Programm)

Graduierten Kolleg Bioethik