BCI2000 Glossary

Session

A number of runs of the same participant, recorded in sequence. Files from a session are recorded into a single data directory.

Run

The time period corresponding to a single data file. A run comprises a number of trials. From the user's view, a run starts when the operator's Start button is clicked, and ends when operation is suspended, either by the application module, or by a click on the Suspend button.

Trial

In a cursor feedback paradigm, the time period during which the user moves the cursor. In an ERP paradigm, the time period following a single stimulus presentation.

Sample Block

BCI2000 processes data in chunks, which are called Sample Blocks, or Data Blocks. State variables are saved with each sample, but may only change once per sample block. Sample block size is configured through the SampleBlockSize parameter; often, ADC hardware imposes restrictions on sample block size.

The physical duration of a sample block is the inverse of the screen update rate, and determined by the ratio of sampling rate to sample block size.

Core Module

One of Data Acquisition, Signal Processing, and User Application Module. These are called core modules because they are involved in on-line processing, as opposed to the Operator Module, which controls operation, and passively displays data sent by core modules, but is not actively involved in processing.

Parameter

A system-wide setting that is constant during a run. Parameters may be of varying type (numeric, string, etc.) and shape (single-valued, list, matrix).

State

A system-wide variable similar to what in other data acquisition applications is often called "event marker." State variables reflect important events during real-time system operation, and are saved to the data file along with each sample. In the current version of BCI2000, the temporal resolution of the state variables is limited to a sample block, i.e., state variables cannot change during a sample block.

Module

A single executable that may act as Operator Module or one of the Core Modules.

Operator Module

The experimenter's user interface, from which the system is configured, started, and stopped.

Visualization

A core module may send information into a display window maintained by the operator module. Visualization data may be of type text, signal, or graphic.

State Vector

A data structure that contains all states concatenated into a single bit string. The state vector is transmitted between modules once for each sample block, but a copy is saved with each sample of data.

Control Signal

The output of the signal processing module. When the Normalizer Filter is used, this signal has zero mean and unit variance.

Source Signal

The signal that is acquired from hardware by the ADC filter, and recorded into the data file. The TransmissionFilter reduces the source signal to a user-defined subset of channels to reduce processing load in the on-line system.

Roundtrip

The time needed for a sample block to traverse the core modules. To fulfil the real-time constraint, roundtrip time may not exceed the physical duration of a sample block.