What are the methods to reject ocular artifacts in the EEG?

Question

Is there any way to remove ocular artifacts from an EEG signal, other than applying independent component analysis, or manual rejection?

Answer 1

According to a review by Croft & Barry (2000), a number of possible methods exist to prevent, or reject ocular artifacts in the EEG;

Prevention/reduction of artifact instances

• Recording with eyes closed -
  A very effective method, but eye closure alters the EEG, e.g., it increases alpha band activity;
• Let subjects fixate on a target -
  Method reduces blinks, but does not eliminate them.

Rejection

• Exclude trials with amplitudes larger than, e.g., 50 microV -
  Method works only with a trial-based approach; artifacts below criterion level will remain.

Reduction

• Subtract a certain standard voltage when an artifact occurs -
  A crude method;
• Online attenuation of the EEG signal when an artifact is detected -
  Works better as the former technique, but is still crude;
• Regression techniques where different electrodes are used to estimate the artifact component in other electrodes -
  A more sophisticated method with apparently good results.

For details I refer to Croft & Barry (2000) and the primary literature cited therein.

<sub>Reference
- Croft & Barry Neurophysiol Clin (2000); 30: 5-19</sub>