Time and frequency analysis of the brain´s distributed gamma-band system

Several paradigms or strategies-some of them introduced here-were applied to point out that the EEG serves as a functionally relevant signal (or operator) in various frequency channels. These can be brought to resonant behavior depending on functional brain states. The authors emphasize that the EEG-operators are functionally significant if 1-4 Hz, 4-7 Hz, 8-13 Hz, or 40 Hz activities can be brought to a resonant state with a high degree of synchrony. The time-locking of an internally induced EEG fragment may depend on the specific behavior (for example induced alpha templates prior to a cognitive target, 40 Hz induced rhythmicities with 300 ms latency in hippocampus during cognitive tasks). For topographic aspects see, e.g., Schurmann & Basar (1994) and Basar & Schurmann (1994). The authors assume that the analysis of evoked potentials (EPs) performed within the scope of resonance phenomena and/or induced rhythmicities can be developed into a most important tool to understand and to inter-relate sensory and cognitive functions of the brain. Once the physiological significance of 10 Hz and 40 Hz resonance phenomena is established, the type of component analysis here presented provides, the authors believe, an excellent possibility to describe functional states of the intact brain during consciousness. The authors assume that by using such methods, the analysis of EEG, sensory EPs, and event-related potentials will experience a renaissance in functional brain research