Biological Rhythms in Arousal Indices: A Potential Confounding Effect in EEG Biofeedback

Abstract

Several investigators have observed ultradian rhythmicities in physiological indices of arousal. Although EEG biofeedback has been widely explored as a means of auto‐regulating cortical arousal, alpha or theta enhancement has not yet been convincingly demonstrated in comparison to continuous baseline controls for the possible effect of endogenous cyclical arousal trends. Diurnal EEG and subjectively appraised arousal measures were recorded from 11 subjects on a 5‐min recording, 5‐min recovery schedule, continuously over 7 1/2 hrs. Subjects returned to the laboratory for an equal amount of recording during which they attempted to either raise or lower the frequency of their EEG with the aid of biofeedback. Significant ultradian rhythmicity centered at about 200 min/cycle was observed in EEG measures and in subjectively appraised arousal. Although eyes‐open frequency‐raising and frequency‐lowering biofeedback training was efficacious in comparison to long‐day baselines, eyes‐closed frequency‐lowering training was not, lending support to other studies which have failed to achieve overall eyes‐closed alpha or theta enhancement even with many hours of training. Because the observed ultradian and circadian EEG rhythmicities could be spuriously interpreted as learning curves under a biofeedback paradigm, it is argued that future designs should incorporate continuous baseline controls.

Identifying Indices of Learning for Alpha Neurofeedback Training

“…These include, changes identified within the NFT session, changes across the NFT sessions, changes within sessions compared to a resting baseline and changes across sessions compared to a baseline. It should come as no surprise that given such a variety of measures and methods that some report changes in alpha as a function of NFT (e.g., Angelakis et al 2007;Hanslmayr et al 2005) whilst others do not (e.g., Gertz and Lavie 1983;Orenstein and McWilliams 1976) and that the differences in measures used has also led some to report changes within NFT sessions but not across sessions (DeGood and Valle 1978), whilst others find changes across sessions but not within (Cho et al 2008). Furthermore, some find evidence of learning when incorporating a resting baseline (Hanslmayr et al 2005) whilst others fail to include any baseline measures (e.g., Angelakis et al 2007).…”

P300 Habituation Patterns: Individual Differences from Ultradian Rhythms

“…Gordon, Stoffer, & Lee, 1995;Klein & Armitage, 1979;Lavie, 1985;Shannahoff-Khalsa, Kennedy, Yates, & Ziegler, 1996). Indeed, ultradian changes in EEG appear related to the Basic Rest Activity Cycle (BRAC) and are a source of neuroelectric variation that modulates arousal level, which is associated with osc~llations in vigilance (Gertz & Lavie, 1983;Kleitman, 1963). Because EEG power reflects wakefulness and demonstrates ultradian cycles (cf.…”

“…How rapidly a subject's EEG desynchronizes may index the amount and timing of attentional resource allocation, which contribute to individual differences in cognitive function that are correlated with E m s (Emmerson, Dustrnan, Shearer, & Turner, 1990;O'Donnell, Friedman, Squires, Maloon, Drachman , & Swearer, 1990;Po-lich, Ladish, & Burns, 1990b;Polich & Martin, 1992). Given that the amount and frequency of EEG activity varies in an ultradian fashion (Gertz & Lavie, 1983;Manseau & Broughton, 1984;Torsvall & Akerstedt, 1987;Tsuji & Kobayashi, 1988), these changes should be manifest with concomitant variation for the P3OO ERP. Although speculative, ERD provides a possible connection between EEG changes and the cognitive operations reflected by the P3OO EW.…”

Brain Oscillations and Diurnal Variations in Hypnotic Responsiveness—A Commentary on “Diurnal Variations in Hypnotic Responsiveness: Is There an Optimal Time to be Hypnotized?”

“…Another complicating factor is that all brain oscillations, including theta oscillations, show strong 90–120-minute ultradian fluctuations in power in individuals throughout the day (Gertz & Lavie, 1983; Kaiser, 2008). Thus, while peaks in theta power or relative theta power might be observed in the morning and late afternoon or evening in large groups of individuals on average, there are marked ultradian changes in brain oscillations that shift in 90–120-minute cycles in individuals.…”