What information is in EDF+ annotations?

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The EDF+ specification defines additional type of signal, so called “EDF annotations” signal. In EDF+ file exported from WinEEG we have 5 different annotations. EDF specification does not prohibit having several such signals in EDF+ file. Moreover, the Polyman software actually reads EDF+ files with multiple “EDF annotations” signals without any problems. The Polyman simply combines all “EDF annotations” signals into one. You can do it the same way.Labels of the beginning ERP trial with number of trial type

WinEEG EDf+ file structure in Polyman software

If you have issues with import of WinEEG EDF or EDF+ files into your own software or any third-party software we recommend to check these files with Polyman software that is recommended by EDF format web site.

On the other hand, the classification of all types of events into 5 “EDF annotations” signals can facilitate their interpretation. We list these signals to help you in interpreting them.

  • 1-st “EDF annotations” signal contains “time-keeping annotation”
  • 2-nd “EDF annotations” signal contains a list of functional trials, such as “Eyes open”, “Eyes closed” and etc.
  • 3-rd “EDF annotations” signal contains a list of any arbitrary events (comments) that the user adds. You can simply ignore these comments.
  • 4-th “EDF annotations” signal contains a list of the artifact epochs. This can be useful information, and it is reasonable to remove the corresponding EEG recording epochs from the subsequent analysis. Please pay attention to the length of these epochs, it can be more than one second.
  • 5-th “EDF annotations” signal contains a list of the trials which can be used to calculate ERPs. Please pay attention to the last number of this annotation. This number should be interpreted as trial label that encodes a condition and helps to sort single trials.

The EDF specification as well as the EDF+ specification also allows the use of an arbitrary sampling rate for each channel separately.

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