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13 Glossary

A

ActiView: Software responsible for acquiring, saving and optional transmitting data from BioSemi? 's Active2 EEG amplifier.

Acquisition: The process of collecting data/information from a device.

Acquisition computer: The computer responsible for managing the data acquisition.

Audio Midi Setup:See MIDI

Action: An action can be one of the following: modify, get or load, function, put or save. See corresponding items in this glossary.

Application (of BrainStream):

Argument: Functions can be given extra information as input to start with, these are called arguments.

B

Block: Every session is divided into different functional blocks. Every 'block' can have a different purpose, e.g. one block for training, one for online feedback, etc.

Block file: To initiate your experiment in BrainStream, you need to compose an initialization run file(s), also called a block file. Every block has a separate file, which contains or refers to all information needed to initiate the particular block.

Brainstream: BrainStream is a Matlab-based toolbox that allows you to run and analyse EEG experiments in a modular way. For a more elaborate description see the introduction of the documentation.

C

Constants (in user-defined functions): User functions can take additional (only constant) arguments besided the obligatory first event argument.

D

Data segment: A limited amount of data from the data stream source.

Data selection: The amount of data the user selects from the data stream source.

Dictionary: Defines interface between source dependent marker information (type and value) and marker names used in BrainStream.

Debug: A run mode which allows step-wise execution of programmed code.For example, when setting break points in Matlab and enabled debug mode, the experiment will stop running and Matlab waiting for you to check the code and continue the experiment by pressing 'F5' on the keyboard.

Decimation: The technique of reducing the number of samples of a signal by first low-pass filtering (in order to remove aliasing effects) and then downsampling the signal.

Default variables: Variables for which no content is defines will take the default value.

E

Event: Markers become events when received. Events have rich structure and can be regarded objects with data (optional), variables, and actions with different moments of execution relative to the onset of the event. Every subsequent same marker in the data stream instantiates a new event.

Experiment: Most BCI experiments involve measurement of several different subjects. Also, BCI experiments can consist of multiple measurements using the same subject each time (i.e. 'sessions'). Every session is divided into different functional blocks. Every 'block' can have a different purpose, e.g. one block for training, one for online feedback, etc. Every block consists of a set of several 'sequences'. Every sequence is self-paced meaning that the participant can push a button to start the next sequence. A sequence is defined as a succession of certain stimuli (e.g. a sequence of tones to generate an auditory evoked potential or a sequence of different motor imagery tasks). These stimuli can be named 'tones', 'trials', 'stimuli', 'epochs', etc. If you take these definitions into account, the hierarchical structure of a common BCI experiment summarizes to 'Experiment' --> 'Subject' --> 'Session' --> 'Block' --> 'Sequence' --> 'Stimulus'. These definitions will be used throughout this documentation. Moreover, this hierarchical structure can serve as a template to arrange locations for data storage.

Experiment definition file: The file that defines the actions for the markers involved in the experiment. This file can also be regarded: the collection of tables that together define the entire experiment.

Experiment definition table: One that defines actions for some markers involved in the experiment. A collection of tables together define the entire experiment, see experiment definition file.

Experiment file: If experiments involve execution of several blocks, references to those blocks can be put together in a single text file, in which every .blk file is denoted in one row. The text file has to be saved with the extension .exp.

F

Field:

Fieldtrip: Fieldtrip is a Matlab software toolbox for MEG and EEG analysis that is being developed at the Centre for Cognitive Neuroimaging of the Donders Institute for Brain, Cognition and Behaviour together with collaborating institutes. For more information see http://fieldtrip.fcdonders.nl/

Function:A function generates and delivers output with respect to the received input.

G

'Get' statement: Use this statement to retrieve a copy of the current content of a user variable from the global variables. The name of the variable will showup as a field in the event structure.

Global variables: All variables defined as headers (except marker, time, function and client) in experiment definition tables. Their content is maintained by BrainStream and can be retrieved (get) or updated (put).

Graphical User Interface (GUI): User friendly interface that can be used to start experiments with feedback about performance and currently executed actions.

H

I

J

K

Key: Users can define their own constants in the block file (see glossary). They should be added to an existing or new topic (see glossary) and assignments follow Matlab symantics.

L

'Load' statement: Instead of retrieving user variables from the global variables, it can also be retrieved from a previous executed block by specifying the load instead of the get action for corresponding variable. A previous block should of course have made content available via the save keyword for the same variable.

M

Markers: Specify some specific timepoint in the data stream which trigger BrainStream to execute possible defined actions (process data, update/modify information, give feedback). The way marker information is provided to BrainStream depends on the datasource in use. Therefore, a dictionary serves to translate markers into marker names which can then be processed independent of the utilized data source.

Matlab: http://www.mathworks.com/products/matlab/ : MATLABŪ is a high-level language and interactive environment that enables you to perform computationally intensive tasks faster than with traditional programming languages such as C, C++, and Fortran.

Midi: Midi (Musical Instrument Digital Interface) is a protocol which allows communication between different computers interface. Midi transmits event messages and thus no media signal such as audio.

MMM Lab: The lab of the Music, Mind, Machine group at Radboud Universiteit, Nijmegen.

Modify: BrainStream actually executes something when it encounters one of the following actions: modify, get or load, functions, put or save. The modify action permits users to directly change content of a global variable, which is especially useful for simple modifications. That is, you do not first need to retrieve a copy from the global variables (get action), change its content, and then update it (put action). Note that modify actions will always be executed first (the order is: modify, get or load, functions, put or save).

Modules:

N

O

P

Path: A path refers to the location of a folder on a drive. In many programs, such as Matlab, a path can be set in which the programs searches for definitions or functions to be used. By setting the path, these functions and definitions become easily accessible.

'Put' statement: Use this statement to update content of a user variable to the global variables. The name of the variable should exist as a field in the event structure.

Q

R

S

'Save' statement: Instead of updating user variables to the global variables, it can also be stored to disk via the save instead of the put keyword for corresponding variable. A subsequent/future block can then retrieve this information via a load keyword on corresponding variable.

Screen Sharing: A feature that allows you to access and control another remote computer by just showing its screen content and directing your mouse/keyboard inputs to this device.

Sequence: Every block consists of a set of several 'sequences'. Every sequence is self-paced meaning that the participant can push a button to start the next sequence. A sequence is defined as a succession of certain stimuli (e.g. a sequence of tones to generate an auditory evoked potential or a sequence of different motor imagery tasks).

Server: Computer running BrainStream.

Session: Multiple measurements using the same subject each time.

Stimuli: 'tones', 'trials', 'stimuli', 'epochs', etc.

Stimulus computer: The computer responsible for generating or managing the stimuli.

String: Some textual information enclosed by quotes.

Structure: A Matlab type variable that manages to keep a collection of (closely related) variables as sub-fields of its own.

T

Terminal:

Time point: e.g. DATA, EVENT

Topic: Users can define their own constants in the block file. They should be added to an existing or new topic and assignments follow Matlab symantics.

Trunk: The trunk is the main line of a program development in a group-shared repository.

U

User-defined functions: Users can write their own MATLAB functions which can be called within an Experiment when an event occurs.

User variable: A variable that is defined by the user. It can be used to exchange information between different events.

V

Variables:

Verbosity level:

W

X

X11:

Y

Z

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Topic revision: r9 - 02 Nov 2009 - 10:01:36 - JoernHorschig
 
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