NIC Data Formats

When recording with NIC2, different file formats can be generated, each one serving a specific purpose:

• .easy → This is the native Neuroelectrics file format. It contains the raw EEG/stimulation data exactly as recorded, including all markers. Because it stores the full raw signal without any preprocessing, it is the most complete representation of the session. It is an ASCII file.

• .nedf → This is the Neuroelectrics extension of EDF. It was created specifically to bridge NIC2 with external analysis tools such as MATLAB and EEGLAB. It is 24-bit resolution. It is composed by a ASCII header with the file information and the EEG binary data.

• .edf → Standard European Data Format, very popular in EEG research. It is the standard binary file for EEG. It is supported by many external EEG analysis tools. Any DC signal will be filtered in this file. It is 16-bit resolution. When exporting to EDF, a 0.1 Hz high-pass filter is applied to the EEG channels only. This removes the DC component (offset/baseline drift) so the signal fits within the EDF format's limited dynamic range. Technically it is a symmetric, zero-phase FIR filter, so only the frequency content is affected: the timing/phase of the signal is preserved. You can confirm this directly in the file: each EEG channel carries the prefiltering label "HP:0.1Hz" in the EDF header (and "HP:0.1Hz Clipped") if any value exceeded the range). The accelerometer channels are not filtered. The .easy format must remain activated because the EDF file is not recorded in real time, it is generated after the recording is complete. For this reason, the .easy file is required as the primary data source during the recording process.

• Sdeeg → It is the standard binary EEG file created when using Holter Mode / SD File.

It is normal to see slight differences between formats because some (like .edf) apply preprocessing (e.g., removing DC components), while .easy and .nedf store the raw unprocessed values.

For further clarification please go to the Instructions for Use in the section “File formats & Directory” of NIC2 manual in User Manuals