The highest frequency which can be accurately represented is one-half of the sampling rate.The sampling rate here is below the Nyquist frequency, so the result of sampling is nothing like the input.
EEG is a difference in potential between two electrodes
If two electrodes are “active”, it is called “bipolar” recording.If one electrode is “silent”, it is called “monopolar” recording. The reference sites: ear lobe, mastoid, nose.Monopolar recording is used in research, because it enables the researcher to localize the event of interest.
Bipolar recording is used in BF, because it reduces shared artifacts. Electrodes should be placed on the sites with the strongest gradients of the potentials under training. These types of artifacts can be detected by visual inspection. Eye blinks can be excluded from data analysis. EMG should be taken into account during spectral analysis.