Brain Computer Interface Based Communication in the Completely Locked-In State

Amyotrophic lateral sclerosis is a progressive motor disease of unknown etiology resulting eventually in a complete paralysis of the motor system but affecting sensory or cognitive functions to a minor degree. There is no treatment available; patients have to decide to accept artificial respiration and feeding after the disease destroys respiratory and bulbar functions or to die of respiratory or related problems. If they opt for life and accept artificial respiration, the disease progresses until the patient loses control of the last muscular response, usually the eye muscles. If rudimentary voluntary control of at least one muscle is present the syndrome is called locked-in state (LIS); ultimately as the disease progresses most ALS patients lose the control of all muscles, the resulting condition is called completely locked-in state (CLIS). Patients in CLIS are unable to communicate with the external world because all assistive communication aids are based on some remaining motor control; hence there is a vital need for an assistive technology to help patients in CLIS to communicate needs and feelings to their family members/caregivers. Brain computer interface (BCI) represents a promising strategy to establish communication with paralyzed ALS patients, as it does not need muscle control. BCI research includes invasive (implantable electrodes on or in the neocortex) and noninvasive means (including electroencephalography (EEG), magnetoencephalography (MEG), functional magnetic resonance imaging (fMRI), and near-infrared spectroscopy (NIRS)) to record brain activity for conveying the user's intent to devices such as simple word-processing programs. Non-invasive methods have been utilized more frequently than invasive methods for people with disabilities (such as those with ALS).

For these conditions (LIS and CLIS) Brain-Computer-Interface were developed and tested extensively since the first publication of Birbaumer, 1999 of two LIS patients suffering from ALS. Patients select letters or words after learning self-regulation of the particular brain signal or by focusing their attention to the desired letter or a letter-matrix and the attention related brain potential selects the desired letter.

Different types of BCI based on EEG and/NIRS is under development to provide a means of communication to patients who have none.