# Export Single Trial Data

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

## Rationale

This article describes how to export single-trial EEG or MEG raw data for further analysis in an external program, e.g. in Matlab.

## Steps to follow

The data are then displayed in the review window. Now you can either

• use the ERP module to define a condition and reject any trials with artifacts (see the BESA Help section on ERP for more information), or
• directly move to the export of all epochs around a particular trigger.

### Export data from BESA

Select "File → Export...". The export dialog opens:

Figure 1 "Export data" dialog

Make sure that the options "Epochs around triggers" and "Original data" are selected. In the section "Target formats", choose the option of choice:

• If you want to create ASCII files for offline analysis, select "ASCII multiplexed" or "ASCII vectorized"
• If you want to analyze data directly in Matlab, select "Send to MATLAB"

For the "Interval..." select a long enough time span as shown below:

Figure 2 "Epoch around trigger" dialog

Then click the "Triggers..." button to select which trigger code or condition will be used.

If you want to export the epochs around a trigger code: Make sure that the trigger code you want is selected - e.g. the trigger code 1 in this example.

Figure 3 "Trigger codes" dialog

If you want to export the epochs around a condition: Check the box "Conditions". Then ensure that the condition of choice is selected (e.g. condition "Rare" in the example in Figure 4).

Figure 4 "Epoch around condition" dialog

After clicking "OK" BESA Research either exports the data, or - if that option was chosen - sends the data to Matlab. In case of Matlab, it opens the Matlab window and creates the structure "besa_channels". From Matlab save the structure as "besa_channels.mat".

### Data in Matlab

The Matlab structure "besa_channels" contains several fields like in the following example of a 64-channel EEG file with 39 trials that survived the artifact scan:

              datafile: [1x93 char]
channeltypes: {1x64 cell}
channellabels: {1x64 cell}
channelunits: {1x64 cell}
channelcoordinates: [64x9 double]
montage: 'Original'
filters: 'Filters off'
samplingrate: 100
HSPcoordinates: [3x3 double]
HSPtypes: {'Fiducial'  'Fiducial'  'Fiducial'}
HSPlabels: {'FidNz'  'FidT9'  'FidT10'}
electrodethickness: 0
structtype: 'besa_channels'
datatype: 'Epoched_Data'
data: [1x39 struct]

The sub-structure data contains the latencies and the measured amplitudes for each channel and trial:

besa_channels.data

» ans =

1x39 struct array with fields:
amplitudes
timeoffsetsecs
latencies
event