Synergetics of Neuronal Populations. A Survey on Experiments

Abstract

The records of brain’s spontaneous electrical activity which often reveals oscillatory rhythmic behavior with amplitudes in the range of 10 – 100 μV are called Electroencephalography (EEG). This activity (“brain waves” = EEG) can be recorded either with macroelectrodes (ca. 50 – 100 μM) placed on or in nervous masses or through the skull and scalp by simple electrodes on the skin. The complex form and changes in form, amplitude, and distribution in such states as sleep, wakefulness, alertness, problem-solving, and hearing and several clinical conditions such as epilepsy, has attracted a great deal of work {1}. The term Evoked Potential (EP) is used for responses, generally of population of neurons, which are time-locked to a distinct stimulus. Although it is small in comparison to brain waves, it may be brought out by averaging the activity after each of many repetitions of stimulus. Evoked potentials in humans and laboratory mammals have proven to be valuable not only in clinical application and in correlations with behavioral and cognitive states, but as a reservoir of higher-order physiological phenomena to be explained at the cellular level {2}. One of the most difficult problems for the understanding of excitability of brain neural populations is the question how the evoked potential is generated. There are several interpretations concerning the genesis of evoked potentials and their relation to EEG {3, 4}.