Electroencephalography (EEG) is the recording of electrical activity along the scalp measured by an EEG Sensor or EEG Cap. Non-invasive EEG can be performed by applying different electrodes on the scalp of the subject. Most often the electrode configuration is according to the International 10-20 system, an internationally recognized method to describe and apply the location of scalp electrodes in the context of an EEG test or experiment.

The EEG is a graphical representation of the electric potential of a large number of neurons (specific: pyramid cells in the cortex). This EEG gives us information about the activity level of the brain and is a valuable tool for research and diagnosis/treatment, with high temporal resolution. Areas of application are neurofeedback, brain mapping, BCI, ERP, P300, neuromarketing etc.

The raw EEG consists of waves or frequencies. These frequencies can be grouped into frequency bands. Examples are the theta, alpha and beta band. Each of these frequency bands possess specific characteristics and are involved in various behavior. The amplitude of the frequencies is measured in micro volts (uV). As a rule of thumb: the higher the frequency, the lower the amplitude.

The EEG is measured with electrodes placed on the skin of the skull and is a non-invasive method. The electrical information coming from the brain is measured, amplified, digitized and transformed into brainwaves.  The BioTrace software is able to show you several frequency bands derived from the EEG, either fixed bands or manual set bands. With the FFT spectral analysis, you can see the total frequency distribution at a glance. Next, numerical values, like the amplitudes, median frequency and power ratios are provided.

Equipment for measuring EEG