Brain–Computer Interfaces - Index of

160 N. Birbaumer and P. Sauseng
patients with large brain damages, such as hydrancephaly (a very rare disorder in
which large parts of the brain are substituted by cerebrospinal fluid) seems to hold
some promise for future development. Particularly in the vegetative state and minimal
responsive state after brain damage, the application of BCI in cases with relatively
intact cognitive function measured with evoked cognitive brain potentials is an
important indication for future development of BCI in neurorehabilitation (see [17]).
4 Brain–Computer Interfaces in Stroke and Spinal Cord Lesions
Millions of people suffer from motor disorders where intact movement-related areas
of the brain can not generate movements because of damage to the spinal cord,
muscles or the primary motor output fibres of the cortex. First clinically relevant
attempts to by-pass the lesion with a brain–computer interface were reported by
the group of Pfurtscheller [29, 14], and in stroke by [9]). Pfurtscheller reported a
patient who was able to learn grasping movements, even to pick up a glass and bring
it to the mouth by using sensory motor rhythm (SMR) control of the contralateral
motor cortex and electrical stimulation devices attached to the muscle or nerve of
the paralyzed hand. Hochberg et al. implanted a 100 electrode grid in the primary
motor cortex of a tetraplegic man and trained the patient to use spike sequences
classified with simple linear discriminate analysis to move a prosthetic hand. No
functional movement, however, was possible with this invasively implanted device.
Buch et al. from our laboratory and the National Institutes of Health, National
Institute of Neurological Disorders and Stroke developed a non-invasive brain–
computer interface for chronic stroke patients using magnetoencephalography [9].
Figure 2 demonstrates the design of the stroke BCI: chronic stroke patients with
no residual movement 1 year after the incident do not respond to any type of rehabilitation;
their prognosis for improvement is extremely bad. Chronic stroke with
residual movement profits from physical restraint therapy developed by Taub (see
[39]) where the healthy non-paralyzed limb is fixated with a sling on the body forcing
the patient to use the paralyzed hand for daily activities over a period of about
2–3 weeks. Learned non-use, largely responsible for maladaptive brain reorganization
and persistent paralysis of the limb, is responsible for the lasting paralysis.
Movement restraint therapy, however, can not be applied to stroke patients without
any residual movement capacity because no successful contingencies of the motor
response and the reward are possible. Therefore, brain–computer interfaces can be
used to by-pass the lesion usually subcortically and drive a peripheral device or
peripheral muscles or nerves with motor activity generating brain activity.
In the Buch et al. study, 10 patients with chronic stroke without residual movement
were trained to increase and decrease sensory motor rhythm (8–15 Hz) or its
harmonic (around 20 Hz) from the ipsilesional hemisphere. MEG with 250 channels
distributed over the whole cortical surface was used to drive a hand orthosis fixed
to the paralyzed hand as seen in Fig. 2. Voluntary increase of sensorimotor rhythm
amplitude opened the hand and voluntary decrease of sensorimotor rhythm from