Channel Definition File Formats

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Module information
Modules BESA Research Basic or higher
Version 5.2 or higher

BESA Research can read 3 types of file to define channels. These are identified by different extensions:

  • *.ela: Channel definition files containing labels and, optionally, channel types (ASCII, 1 label/line).
  • *.elp: Channel definition files containing coordinates and, optionally, channel types and labels (ASCII). This is the format of the file written by the Channel Configuration Dialog.
  • *.elb: Channel definition files stored by older versions of BESA Research (binary format). This format can still be read, but is no longer written by BESA Research.

Channel Label File Format (*.ela)

Files containing a list of channel labels are an alternative to editing electrode configurations in the application. These files can be edited using a standard text editor.

Electrode label files (.ela) require a sequence of lines corresponding to the sequence of channels in the data. Each line contains one label and an optional identifier. The format is [Identifier] {Label}, ([Identifier] can be omitted if the electrode label defines the type of signal)

Identifiers can be one of:

EEG scalp electrode
SCP scalp electrode
POL polygraphic channel
PGR polygraphic channel
ICR intracranial electrode
MEG MEG sensor
REF reference electrode (this can only occur once, and must be the last item in the file)

Examples:

Fz scalp electrode, coordinates assigned by default.ecd
Cz scalp electrode, coordinates assigned by default.ecd
VEOG vertical EOG, Polygraphic type is assigned by default
Exx xx=01, 02.. electrode number, Polygraphic type is assigned by default
EEG xx scalp electrode, coordinates must be assigned either by default.ecd or by a surface point file (*.sfp). An alternative to the "EEG" prefix is "SCP".
POL XX identifier sets Polygraphic type - an alternative to the "POL" prefix is "PGR"
ICR A01 identifier sets Intracranial type to electrode A01 - do not use A1!
ICR A02 identifier sets Intracranial type to electrode A02 - do not use A2!
MEG M01 identifier sets MEG type to electrode M01 - do not use M1!
MEG M02 identifier sets MEG type to electrode M02 - do not use M2!
REF Cz the label is assigned to the electrode reference, no channel is associated with this entry. This must be the last line of the file!

Channel Spherical Coordinate File Format (*.elp)

These files follow the same rules as the channel label files, with the addition of spherical coordinates (theta, phi) that follow the labels of EEG and MEG channels.

Labels can also be omitted. In this case, BESA Research will assign labels according to the nearest coordinate defined in the default.ecd file. To indicate that the coordinates have been assigned, the label will have a tick, e.g. Fz' instead of Fz.

Channels of other types (polygraphic; intracranial) are defined exactly as in the channel label (*.ela) file.