Modeling the effects of extracortical sources on the EEG-signal.

Extracortical activity play important role in generation of EEG-signal. Neuronal system in the brain seems to be specially sensitive to sources belonging to the class of functions: [Acos(αt)+Bsin(αt), exp(±αt), Bessel functions]. This representation could be reflect influence of external sources, for example electromagnetic fields, on the brain. In my previous papers I demonstrated the effect of electromagnetic field on the EEG-signal using nonlinear dynamics method - Higuchi's fractal dimension. The extracortical input from inhibitory neurons destroys the oscillatory structure of signal generated by extracortical input from excitatory neurons but do not suppresses it completely. The additional component is needed. The long-distance input from excitatory neurons take this role. The most important parameter in the model is postsynaptic neurotransmitter rate constants. It shows a biphasic effect changes for inhibitory postsynaptic potentials (IPSP) in the EEG-signals during anesthesia. The similar behavior is visible for postsynaptic rate constants but in case of excitatory postsynaptic potential (EPSP) in epileptic EEG-signals. There are two opposed processes occur. The average excitatory soma potential (he) depend on total number of excitatory and inhibitory intracortical connections. The increase of maximum value of the he occurs for bigger number of excitatory connections. The shape of the curve depend on number of inhibitory connections. [ABSTRACT FROM AUTHOR]