Spectral analysis of the EEG signal will be performed by fast Fourier Transform (FFT - using MATLAB function) for each patient on 2 seconds epochs of recording, taken at 5 minutes intervals (to fit the frequency of CGMS measurements), with a resolution of 0.5 Hz. The frequency bands will be divided to delta (0.5-3.5 Hz), theta (4-7.5 Hz), alpha (8-13 Hz), beta (13.5-29.5 Hz), low gamma (30-47.5 Hz) and high gamma (52.5-80 Hz).