The artifacts are signals with no cerebral origin. They can mainly have 3 origins (ocular, muscular and mechanical)

Eye blinks

Eye blinks make a slow signal (< 4Hz) corresponding to mechanical movement of eyelid.
The signal appear mainly on frontal area (Fp1 and Fp2).
The signal is symmetric between two hemispheres.


Eye movement

Eye movement make as well a slow signal (< 4Hz) corresponding to mechanical movement.
The eyes make a dipole, which go closer or away from some electrodes and create the signal.
The signals appear mainly on frontal and temporal area. It is more propagated than blinks.
This signal is anti symmetric between two hemispheres.


Muscular artifacts

Muscular activity give high frequency signals (> 13Hz), often much higher than cerebral signals.
The main head muscle is the jaw which can create an important signal in temporal area (seconds 0 to 5).
Frontal muscles can appear as well since they are located just under the electrodes (seconds 5 à 10).


Electrode artifacts

Sometimes, wire or electrode movements create a low frequency artifact (< 2Hz) on one electrod.
The signal has often high amplitude.
It is also possible that a mechanical artifact appear following to a head movement and on this case a signal appear on several electrodes.
Last updated: 27th of October 2010
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