| |
| |
| 4.
BCI - Brain–computer interfaces |
| |
4.2. Present-day BCIs
| |
4.2.4. Mu and beta rhythms
| |
4.2.4.1.
The Wadsworth BCI |
|
|
People with or without motor disabilities learn to control mu-
or beta-rhythm amplitude and use that control to move a cursor
in one or two dimensions to targets on a computer screen.
The picture shows the basic phenomenon.
 |
Picture:
sensorimotor rhythm BCI. Scalp EEG is recorded over sensorimotor
cortex. Users control the amplitude of a 8–12 Hz
mu rhythm (or a 18–26 Hz beta rhythm) to move a
cursor to a target at the top of the screen or to a target
at the bottom (or to additional targets at intermediate
locations). Frequency spectra (top) for top and bottom
targets show that control is clearly focused in the mu-rhythm
frequency band. Sample EEG traces (bottom) also indicate
that the mu rhythm is prominent when the target is at
the top and minimal when it is at the bottom. |
Users
learn over a series of 40 min sessions to control cursor movement.
They participate in 2–3 sessions per week, and most acquire
significant control within 2–3 weeks. In the initial sessions,
most employ motor imagery (e.g. imagination of hand movements,
whole body activities, relaxation, etc.) to control the cursor.
As training proceeds, imagery usually becomes less important,
and users move the cursor like they perform conventional motor
acts, that is, without thinking about the details of performance.
Source:
Brain–computer
interfaces for communication and control, Clinical Neurophysiology
113 (2002) 767–791, Jonathan R. Wolpaw, Niels Birbaumer, Dennis
J. McFarland, Gert Pfurtscheller, Theresa M. Vaughan |
|
|
