The technical, neurological, and psychological significance of 'alpha', 'delta' and 'theta' waves confounded in EEG evoked potentials: a study of peak amplitudes

In a complementary report, the analysis of peak latencies provided evidence that EEG averaged evoked potentials (AEPs) and event related potentials (E RPs) confound 'delta', 'theta', and 'alpha' frequency responses thought to be generated by the 'brain-stem', 'limbic', and 'thalamic' cortical activat ing systems, respectively. The present report deals with amplitude data obt ained from the same sample of 93 adults by recording EEG responses to audit ory tones and using narrow-band filters to distinguish '4 Hz','7 Hz', and ' 10 Hz' component waves that constitute the unfiltered AEP. Bivariate and mu ltivariate statistical analyses of peak amplitudes provide additional evide nce of the distinct and unitary nature of these component waves. Correlatio ns with age, sex, and wakefulness variables confirm that the component wave s are associated with systems that maintain behavioural arousal. The amplit ude results extend the latency findings by revealing the functional organis ation of the three arousal systems in terms of excitatory and inhibitory pr ojections. It is suggested that there are implications for future research on the physiology of brain arousal systems, and for the study of normal per sonality and temperament, as well as for the diagnosis of psychiatric disor ders and the monitoring of drug effects and therapies. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.