EEP - Channel Groups

Channel Groups

Usage

Channel groups are useful to classify the multitude of channels that clutter your screen into different categories (e.g. high-resolution EEG/MEG). Selection of these categories from within the xcnt viewer (in the Channels menu) allows you to view only the channels belonging to a specified category.

Normally, the classification holds only for one electrode configuration; for the electrode setups most used in a laboratory, some standard configuration files will be available. Please always use descriptive comments in your configuration, especially for non-standard configuration files.

EEP modules that support this Channel Groups concept, expect this in a file called "channels.cfg", which should be located in a standard configuration directory.

Format

The channel groups configuration file follows the EEP standard configuration format, where the Sections are the identifiers of the channel groups and the Items indicate either a channel label or a reference to a channel group identifier.

A reference to a channel group is made by preceding its identifier with "$"; therefore "$EOG" indicates a channel group, that should be specified as

[EOG]
label1, label2, ...

Forward references are allowed, circular references are not allowed. Group names should be different from all available channel labels, and should consist of one word only.

A channel can only occur once within a group; repetitions will be ignored. You can specify channels that are not available in a cnt file. For example, it is possible to specify a setup for a 80-channel recording and use that for a 78-channel recording that fails two of the channels. Therefore it is not possible to recognize errors in the channel label specification.

Example

Consider an EEG recording using electrode positions F1, F2, F3, P1, P2, P3, EOGV, EOGH, REF, EKG, UKW. A possible grouping could be:

[Front]
F1, F2, F3

[Back]
P1, P2, P3

[EOG]
EOGV, EOGH

[AUX]
REF, EKG, UKW

[EEG]
$front, $back

[All]
$eeg, $eog, $aux

(A group 'All' is not really necessary, because the EEP modules process all channels as default behaviour - but this allows for a custom order of the channel display in the xcnt viewer)