Slow rhythms of EEG

The wavelet transform permits an approach of the mechanisms underlying the EEG activity. Brain activity results from interaction between different brain areas. These could modulate the amplitude of EEG activity and generate slow rhythms (Steriade et al., 1993). The wavelet transform was used to extract frequency (FM) and amplitude (AM) modulations of the EEG signal. AM was decomposed in two frequency bands: a) medium frequency band (MF) in the range 0.1-0.5 Hz, which could be linked with interactions between neuron networks and b) low frequency band (LF) in the range 0.015-0.1 Hz, which could be linked with peripherical activity via the cerebral trunk. The authors preliminary results show firstly the existence of the AM in the two bands MF and LF, secondly the negative correlation between amplitude and frequency modulation.