Analyzing signals recorded by electroencephalography (EEG) may allow to determine mental states of humans based on the measured electric activity of their brains. The EEG signals can be grouped into specific wavebands, which are associated with certain brain states. In order to get the frequency information from the recorded time signal (voltage) a variety of mathematical transformation methods are available. In this project the Gabor Transformation is used to retrieve the spectral distribution of the signal at different times. A software tool for processing and displaying relevant data extracted from the EEG signals is the main focus of this work. Also, the tool is evaluated using EEG signals from experiments with patients in vegetative states.