Institute for Language Sciences Labs

Institute for Language Sciences Labs

How-tos

Running an EEG experiment: Introduction

Last updated on 23 January 2018 by Chris

If you have suggestions on how to improve this document, or find mistakes, please send them to labman.gw@nulluu.nl

Introduction

This page aims to give you a step-by-step guide to running your own electroencephalographic (EEG) experiments. Our BioSemi EEG equipment is located in room K.13. Technical details about the set-up can be found on the facilities page (including default filtering). Software and hardware settings can be found here.

To be a competent EEG experimenter it is important to understand that applying filters in postprocessing always distorts your data, that this is a bad thing, and hence should be avoided as much as possible.

There is no substitute for good data.

“There is no substitute for good data. It is folly to believe that artifact rejection is going to transform data into good data; it can reject occasional artifactual trials allowing good data to be better. There is not way that artifact rejection can compensate for a subject who consistently blinks in response to particular events of intrest or who emits continuous high-amplitude alpha activity. In other words, data that are contently noisy or have systematic artifacts are not likely to be much improved by artifact rejection. (J. C. Hansen, technical guru, UCSD, unpublished software documentation)”
-From An Introduction to the Event-Related Potential Technique by Steven J. Luck.

Step-by-step guide to running an EEG experiment


Step 1: Before you start.

Step 1. Before you start

Support and opening hours

Shuttling scripts and data to other computers

The lab is primarily meant for running experiments; you are expected to do some of your experiment preparation, and all of your data analysis, on computers outside the lab or in room K.06. Use the ILS Labs data server to move your data to other PCs, and to safely store it.

Step 2. Implement your experiment.

Generate the stimuli based on your experimental design and implement them in the presentation software.

Step 3. Test your experiment.

Check if all stimuli and responses are correctly presented in the test room. Also check if the triggers arrive as they should (trigger code and time) at the BioSemi software.

Step 4. Pilot your experiment with actual participants.

Learn how to use the EEG apparatus and run a pilot before you start recording participants one-after-another. Expect (slight) delays and reworks of your design.

Step 5. Run your experiment: recruit subjects.

  • Help with recruiting participants is available here.
  • A template consent form can be retrieved from the FEtC-H website

Step 6. Analyze your data.

This is a very important difficult step in doing an EEG experiment and generally requires an intermediate understanding of Fourier Transformations, epoch, artifact rejects, etc. Each experiment has a different focus and design. The focus and design determine the type of analysis that should be performed, and as such it is difficult to provide a generic guide to EEG analysis. However, there is a set of procedures that are nearly always followed. These procedures need to occur in the set order:

  1. Filter the continuous EEG data.
  2. [optional] Down sample your recorded data to a rate that is sufficient for your analysis (Remember the Nyquist limit)
    • It is a good idea to have a filter that prevents aliasing prior to down sampling.
  3. Epoch your data based on triggers of events.
  4. Reject artificial epochs.
    • This is when the electro-oculargraphy shines since it gives you the clearest indication of when a participant blinked or moved their eyes. You can select face electrodes that best reveal artifacts and use these to select ‘corrupted’ epochs.
  5. … The rest is up to you.

Useful links

Further reading

  • “An Introduction to the Event-Related Potential Technique“, S. Luck, 2005, MIT Press