EEG and noise
There are 3 types of noise that hampers EEG data, each is dealt with separately:
External noise, or noise from electric equipment, air condition, lighting, power outlet, cell phones, transportation,... Some of this noise is easy to filter out if they operate outside spectrum of interest. For instance, if you are interested in brain activities way below the 60Hz, a low pass filter will remove most of the 60 Hz noise due to power outlet. Otherwise, you can use a notch filter, but beware what it is doing to your signal in the vicinity of filtering. As for low frequency noise, we remove them using a high pass filter.
Artifact noise, due to bodily movement, like eye blink, eye movement, sweat conductivity, foot tapping, muscle tensions, heart beat, jaw movement, ... This kind of noise is harder to deal with, and this is why, most EEG system will triangulate on eye blink, and eye movement, that constitute most of artifact noise present in EEG signal. By dedicating few electrodes to monitor such movement, it becomes easier to subtract from your signal. Usually, there are eye reference electrodes below, above, and exterior of eye.
Background noise, is all neural activities that are not induced by stimulus of interest. For example, in an auditory experiment, any visual neural activities will be considered as background noise, and vice versa. It is much easier to deal with such noise in an ERP(Event Related Potential) where the stimulus is presented many times, and due to the variability of non relevant neural activities, when averaged across, they will flatten out.
There are 3 types of noise that hampers EEG data, each is dealt with separately:
External noise, or noise from electric equipment, air condition, lighting, power outlet, cell phones, transportation,... Some of this noise is easy to filter out if they operate outside spectrum of interest. For instance, if you are interested in brain activities way below the 60Hz, a low pass filter will remove most of the 60 Hz noise due to power outlet. Otherwise, you can use a notch filter, but beware what it is doing to your signal in the vicinity of filtering. As for low frequency noise, we remove them using a high pass filter.
Artifact noise, due to bodily movement, like eye blink, eye movement, sweat conductivity, foot tapping, muscle tensions, heart beat, jaw movement, ... This kind of noise is harder to deal with, and this is why, most EEG system will triangulate on eye blink, and eye movement, that constitute most of artifact noise present in EEG signal. By dedicating few electrodes to monitor such movement, it becomes easier to subtract from your signal. Usually, there are eye reference electrodes below, above, and exterior of eye.
Background noise, is all neural activities that are not induced by stimulus of interest. For example, in an auditory experiment, any visual neural activities will be considered as background noise, and vice versa. It is much easier to deal with such noise in an ERP(Event Related Potential) where the stimulus is presented many times, and due to the variability of non relevant neural activities, when averaged across, they will flatten out.