Brain–Computer Interfaces - Index of

272 J. Mellinger and G. Schalk
recorded data. The final element is data analysis, which requires mastery of an
analysis software environment.
While BCI2000 is not intended to replace a dedicated stimulation software system
(such as Presentation or E-Prime), it provides a flexible stimulation environment
with good timing behavior, and it integrates stimulation and data recording. It also
comes with tools that provide easy-to-use, basic statistical data analyses, and provides
a number of interfaces to commercial as well as non-commercial analysis
toolboxes (Sect. 2.3). Finally, BCI2000 comes with a standardized timing evaluation
procedure that may be run on the target hardware to ensure quality of measurement.
To illustrate how BCI2000 could be useful for psychophysiological experiments,
we describe how to configure BCI2000 for a Stroop task. The Stroop task is a classical
neuropsychological paradigm designed to measure the ability of a subject to
override strongly automated behavior [31]. In a computerized version of the Stroop
task, color names are displayed as textual stimuli on a computer screen. These color
names are displayed in color; color names and actual colors do not always match,
e.g., the stimulus might be the word “red” printed in green. The subject’s task is
to respond to the actual color, not the color name, by pressing a key. In data analysis,
performance may be analyzed in terms of response time, and correctness of
responses.
Implementation of a Stroop task experiment in BCI2000 requires three steps.
First, graphics files for stimuli need to be created, which contain the names of colors
and are printed in different color. These graphics files may be created using any
graphics application such as the Paint program that comes with Windows TM .For
five color names, and five actual colors, up to 25 graphics files need to be created,
depending on whether all possible combination are to be used.
The second step is to configure BCI2000 display the stimuli. Using the
StimulusPresentation application module contained in the BCI2000 core distribution,
this requires creating a table listing all stimuli, specifying parameters for a
pseudo-random sequence in which stimuli will be presented, and deciding on stimulus
duration, inter-stimulus intervals, and inter-stimulus interval randomization.
The final step is to configure BCI2000 to record key presses during the experiment.
The respective BCI2000 component is provided within all source modules,
and is activated by adding the command-line option “–Logkeyboard=1” when
starting up a source module.
3.3 Patient Communication System
As a real-world application of BCI technology, a patient communication system uses
a BCI as an input device similar to a computer keyboard or mouse. Once a particular
BCI system has been designed and tested in laboratory experiments, BCI researchers
may want to apply the resulting system to patients. Typically, this target population
is constrained to their beds and depends on caregivers. A BCI may improve their
quality of life by increasing their independence and amount of control over their
environment.