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Prof. Dr.-Ing. habil. Jens Haueisen
Director of the BMTI Institute and head of Biomedical Engineering Group
Prof. Dr.-Ing. habil. Jens Haueisen
phone: +49 3677 69 2861
Electrical stimulation of peripheral somatosensory nerves evokes two types of early brain activity in two distinct frequency ranges that can be detected with electroencephalography (EEG) or magnetoencephalography (MEG). An oscillatory brain activity with a mean frequency around 650 Hz is overlaying the initial low frequency (up to 250 Hz) cortical responses at latencies of 18 to 30 ms after stimulus (N20, P25) (figures 1 & 2).
Using time-frequency analysis, we found that the frequency of the first oscillatory 600 Hz component increases in frequency over time (figure 3).
We could show that the 600 Hz oscillations consist of two parts (bifurcation of the dispersion curves in the time-frequency plane) and can be associated by means of source reconstruction to the Brodmann areas 3b and 1 (figure 4).
We analyzed the coupling between the active brain areas with the help of models described by a system of differential-algebraic equations. Comparing models with various degrees of coupling, we show that mutual information transfer can be distinguished from one-way information transfer for activated cortical areas estimated by source localization techniques (figure 5).