A pianist plays a series of notes, and the woman echoes them on a computerized music system. The woman then goes on to play a simple improvised melody over a looped backing track. It doesn't sound like much of a musical challenge — except that the woman is paralysed after a stroke, and can make only eye, facial and slight head movements. She is making the music purely by thinking. This is a trial of a computer-music system that interacts directly with the user's brain, by picking up the tiny electrical impulses of neurons. The device, developed by composer and computer-music specialist of the University of Plymouth, UK, working with computer scientists at the University of Essex, should eventually help people with severe physical disabilities, caused by brain or spinal-cord injuries, for example, to make music for recreational or therapeutic purposes. Evidence suggests that musical participation can be beneficial for people with neurodegenerative diseases such as dementia and Parkinson's disease. But people who have almost no muscle movement have generally been excluded from such benefits, and can enjoy music only through passive listening. The development of brain–computer interfaces (BCIs) that enable users to control computer functions by mind alone offer new possibilities for such people. In general, these interfaces rely on the user's ability to learn how to self-induce particular mental states that can be detected by brain-scanning technologies. Researchers have used one of the oldest of these systems: electroencephalography (EEG), in which electrodes on the skull pick up faint neural signals.
The EEG signal can be processed quickly, allowing fast response times, and the instrument is cheaper and more portable than brain-scanning techniques such as magnetic resonance imaging and positron-emission tomography. Previous efforts using BCIs have focused on moving computer screen icons such as cursors, but researchers sought to achieve the much more complex task of enabling users to play and compose music. The trick is to teach the user how to associate particular brain signals with specific tasks by presenting a repeating stimulus — auditory, visual or tactile — and getting the user to focus on it. This elicits a distinctive, detectable pattern in the EEG signal. For example, a button could be used to generate a melody from a preselected set of notes. The user can alter the intensity of the control signal – how 'hard' the button is pressed – by varying the intensity of attention, and the result is fed back to them visually as a change in the button's size. In this way, any one of several notes can be selected by mentally altering the intensity of pressing. With a little practice, this allows users to create a melody as if they were selecting keys on a piano. And, as with learning an instrument the more one practices the better one becomes. The researchers trialled their system on a female patient who has locked-in syndrome, a form of almost total paralysis caused by brain lesions, at the Royal Hospital for Neuro-disability in London. During a two-hour session, she got the hang of the system and was eventually playing along with a backing track. She reported that it was great to be in control again.
More information:
http://www.nature.com/news/2011/110318/full/news.2011.113.html
More information:
http://www.nature.com/news/2011/110318/full/news.2011.113.html