Export Single Trial Data

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

1 Load data in BESA

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.

2 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 in figure 2:

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.

Figure 2 "Epoch around condition" dialog