EEG artefacts

In this clip Vasso and Cat demonstrate the common artefacts during EEG recordings. It is important to critically evaluate the data you've recorded. In the worst case it could have just been muscle activity. See the plot below which shows EEG from the forehead relaxed and smiling.

The positive electrode was placed at Fp1, the negative at A1 and GND at A2. Same setup as shown in the video clip.

References

The first two references describe the EMG contamination of the EEG and then the following references discuss how this contamination affects brain computer interfaces and depth of anesthesia monitors (bispectral index). Both applications can be fooled into taking EMG for EEG with quite disturbing results.

• EMG contamination of EEG: spectral and topographical characteristics.
• EMG and EOG artifacts in brain computer interface systems: A survey
• Surface Laplacian of Central Scalp Electrical Signals is Insensitive to Muscle Contamination
• Thinking activates EMG in scalp electrical recordings.
• Relation of gamma oscillations in scalp recordings to muscular activity.
• Scalp electrical recording during paralysis: quantitative evidence that EEG frequencies above 20 Hz are contaminated by EMG.
• The bispectral index declines during neuromuscular block in fully awake persons.
• Survey on the adequacy of depth of anaesthesia with bispectral index and isolated forearm technique in elective Caesarean section under general anaesthesia with sevoflurane.
• EOG and ECG can be removed from an EEG: Artifact removal from EEG signals using adaptive filters in cascade but removal of EMG is virtually impossible.

Brain computer interfaces (BCI) claim to use EEG to control, for example, a video game. However, if there are non-stationary artefacts detection of EEG might be impossible: Bernd Porr, Lucía Muñoz Bohollo (2023) BCI-Walls: A robust methodology to predict if conscious EEG changes can be detected in the presence of artefacts. Plos One.

Next clip: Using dry EEG electrodes.