Brain–Computer Interfaces - Index of

A Simple, Spectral-Change Based, Electrocorticographic Brain–Computer Interface 243
Fig. 2 Necessary elements for co-registration of electrodes and plotting of data on template cortices.
(a) Clinical schematic; (b) Diagnostic imaging; (c) Cortical electrode position reconstruction
only is this a kind thing to do, but it makes the difference between 10 min and
10 h of experimental recording and participation. The second is that the hospital
environment requires constant interaction with physicians, nurses, and technicians,
and all of these individuals have responsibilities that take priority over the experimental
process at any time. It is important to cultivate and maintain a sympathetic
relationship with these individuals. The last reason is that the hospital room is not
a controlled environment. There is non-stationary contamination, a clinical recording
system to be managed in parallel, and constant interruption from a myriad of
sources. The researcher must be able to maintain an even disposition and be able to
constantly troubleshoot. (b) A central computer. This computer will be responsible
for recording and processing the streaming amplified potentials from the electrode
array, translating the processed signal into a control signal, and displaying the control
signal using an interface program. The computer must have a large amount
of memory, to buffer the incoming data stream, a fast processor to perform signal
processing in real-time and adequate hardware to present interface stimuli with
precision. Therefore, it is important to have as powerful a system as possible, while
remaining compact enough to be part of a portable system that can easily be brought
in and out of the hospital room. An important element not shown in the picture is
the software which reads the incoming datastream, computes the power spectral
density changes, and uses these changes to dynamically change the visual display
of an interface paradigm. We use the BCI2000 program [15] to do all of these things
simultaneously (see Chapter “Using BCI2000 in BCI Research” for details about
BCI2000). (c) A second monitor. It is a good idea to have a second monitor for
stimulus presentation. It should be compact with good resolution. (d) The subject.
It is important to make sure that the subject is in a comfortable, relaxed position,
not just to be nice, but also because an uncomfortable subject will have extraneous
sensorimotor phenomena in the cortex and also will not be able to focus on the task.
(e) Signal splitters. If a second set of amplifiers (experimental or clinical) is being
used in parallel with the clinical ones used for video monitoring, the signal will be
split after leaving the scalp, and before the clinical amplifier jack-box. The ground
must be split as well, and be common between both amplifiers, or else there is the
potential for current to be passed between the two grounds. Several clinical systems