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

Abstract

It is suggested that lack of progress in understanding the neurological and psychological significance of EEG averaged evoked potentials (AEPs) and event related potentials (ERPs) may be due to the confounding of, ‘delta’, ‘theta’ and ‘alpha’ frequency responses generated by the ‘brain-stem’ ‘limbic’ and ‘thalamic’ cortical activating systems, respectively. This hypothesis was tested in a sample of 93 adults by recording EEG responses to auditory tones and using narrow-band filters to distinguish ‘4 Hz’, ‘7 Hz’, and ‘10 Hz’ component waves in the unfiltered AEP. Bivariate and multivariate statistical analyses of peak latencies provided evidence of the distinct and unitary nature of these component waves and demonstrated their relative influence on the P1, N1 and P2 peaks of the unfiltered AEP. The results also reveal a predicted negative relationship between the 10 and 4 Hz latencies which is attributed to inhibition of the delta frequency brain-stem ascending reticular activating system (BSARAS) by the alpha frequency diffuse thalamic projection system (DTPS). Correlations of the 4 Hz latencies, with age, sex, and behavioural arousal variables confirm that the 4 Hz latencies are associated with the maintenance of behavioural arousal, an important function of the BSARAS.