Oscillatory brain dynamics, wavelet analysis, and cognition

Author(s): Demiralp, T., Schurmann, M., BasarEroglu, C., Ademoglu, A.

Journal/Book: Brain Lang. 1999; 66: 525 B St, Ste 1900, San Diego, CA 92101-4495, USA. Academic Press Inc. 146-183.

Abstract: On the basis of a systems theoretical approach it was hypothesized that event-related potentials (ERPs) are superpositions of stimulus-evoked and time-locked EEG rhythms reflecting resonance properties of the brain (Basar, 1980). This approach led to frequency analysis of ERPs as a way of analyzing evoked rhythms. The present article outlines the basic features of ERP frequency analysis in comparison to ERP wavelet analysis, a recently introduced method of time-frequency analysis. Both methods were used in an investigation of the functional correlates of evoked rhythms where auditory and visual ERPs were recorded from the cat brain. Intracranial electrodes were located in the primary auditory cortex and in the primary visual cortex thus permitting ''cross-modality'' experiments. Responses to adequate stimulation (e.g., visual ERP recorded from the visual cortex) were characterized by high amplitude alpha (8-16 Hz) responses which were not observed for inadequate stimulation. This result is interpreted as a hint at a special role of alpha responses in primary sensory processing. The results of frequency analysis and of wavelet analysis were quite similar, with possible advantages of wavelet methods for single-trial analysis. The results of frequency analysis as performed earlier were thus confirmed by wavelet analysis. This supports the view that ERP frequency components correspond to evoked rhythms with a distinct biological significance.

Note: Article Basar E, Univ Lubeck, Inst Physiol, D-23538 Lubeck, GERMANY

Keyword(s): EEG; evoked potential; event-related potential; frequency analysis; wavelet analysis; evoked rhythm; EVENT-RELATED POTENTIALS; EVOKED-POTENTIALS; VISCERAL GANGLION; FIELD POTENTIALS; VISUAL-CORTEX; HELIX-POMATIA; CAT BRAIN; RESPONSES; HIPPOCAMPUS; SYSTEM

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