Brain–Computer Interfaces - Index of

268 J. Mellinger and G. Schalk
processing module may profit from all existing BCI2000 components, and additionally
introduce a new filter component, purely by writing Matlab code rather than
C++. Such a filter component consists of a processing script that acts on chunks of
data, and a few helper scripts that provide configuration and initialization functions.
These scripts are executed inside a Matlab engine environment, and have full access
to BCI2000 configuration parameters and state variables. In other words, it is possible
to write Matlab scripts that request system parameters (which will appear at the
interface to the investigator and are stored in the data file) and state variables (which
will be stored along with individual data samples).
2.3.4 Online Data Exchange
In addition to the TCP/IP-based network protocol used internally by BCI2000
(which is capable but complex), BCI2000 also includes a simple UDP-based network
protocol. The protocol data format is ASCII-based and human-readable; it
consists of a sequence of names followed by numerical values. This protocol is used
to transfer information contained in state variables, and the “control signal” that is
transferred from the Signal Processing module into the application module.
This data sharing interface is useful if BCI2000 is to be connected to external
application programs such as word processors (so that the external application is
controlled by the output of the Signal Processing module), or to hardware such
as environmental control interfaces, wheelchairs, or limb prostheses. The use of
that interface requires writing a small interfacing application in any programming
language, or modifying an existing application to read data over a network
connection.
2.3.5 Operator Module Scripting
As described above, the Operator module is the experimenter’s graphical user interface
(GUI) for configuration and control of the BCI2000 system. Some of the
operations of the Operator module can be scripted to execute programmatically.
Most importantly, scripts may be tied to events such as system startup, or the
end of an experimental run. Using Operator scripting, it is possible to completely
wrap up the experimenter side of BCI2000 into scripts, and to remote-control it
from a separate application. Thus, for example, a complex series of stimulus presentation
paradigms can be realized using combinations of BCI2000 and external
applications.
2.4 Important Characteristics of BCI2000
In summary, BCI2000 provides a number of characteristics that make it a good
choice for many research applications. First, it comes with full source code in
C++ and can incorporate signal processing routines written in Matlab TM . Second,
BCI2000 does not rely on third-party components for its execution; modifications