Awareness during drowsiness: Dynamics and electrophysiological correlates.

Abstract

Summary: During drowsy periods, performance on tasks requiring continuous attention becomes intermittent. Previously, we have reported that during drowsy periods of intermittent performance 7 of 10 participants performing an auditory detection task exhibited episodes of non-responding lasting about 18 s . Further, the time patterns of these episodes were repeated precisely in subsequent sessions. The 18 s cycles were accompanied by counterbalanced power changes within two frequency bands in the vertex EEG (near 4 Hz and circa 40 Hz). In the present experiment, performance patterns and concurrent EEG spectra were examined in four participants performing a continuous visuomotor compensatory tracking task in 15-20 minute bouts during a 42-hour sleep deprivation study. During periods of good performance, participants made compensatory trackball movements about twice per second attempting to keep a target disk near a central ring. Autocorrelations of time series representing the distance of the target disk from the ring center showed that during periods of poor performance, marked near 18 s cycles in performance again appeared, with phases of poor or absent performance accompanied by an increase in EEG power that was largest at 3-4 Hz. These studies show that in drowsy humans, opening and closing of the gates of behavioral awareness is marked not by the appearance of (12-14 Hz) sleep spindles, but by prominent EEG amplitude changes in the low theta band. Further, both EEG and behavioral changes during drowsiness often exhibit stereotyped 18 s cycles.

Co-modulatory spectral changes in independent brain processes are correlated with task performance

“…Consistent with earlier findings, alpha-band power increased as the DEMA increased from near-perfect performance (Akerstedt and Gillberg, 1990;Huang et al, 2009;Jung, 1995, 1996;Makeig et al, 2000;Schier, 2000). Moreover, the alpha band power decreased as the DEMA continued to increase, consistent with the biphasic trend along the human alertness-drowsiness dimension reported by Ota et al (1996).…”

“…Compatible with earlier findings in different sustained-attention tasks, delta-band power increased as task performance declined (Kirmizi-Alsan et al, 2006;Torsvall and aAkerstedt, 1987;Uchida et al, 1991), and the thetaband power of several brain regions was highly correlated with task performance changes (Akerstedt and Gillberg, 1990;Beatty et al, 1974;Campagne et al, 2004;Jung et al, 1997;Kecklund and Akerstedt, 1993;Lal and Craig, 2002;Jung, 1995, 1996;Makeig et al, 2000;Takahashi et al, 1997).…”

Tonic and phasic EEG and behavioral changes induced by arousing feedback

“…Lapses in alertness become more frequent and prolonged under conditions of sustained wakefulness or lack of sleep, and may have both subtle and catastrophic consequences for operation safety and effectiveness in a wide variety of operational environments. Several studies have demonstrated that fluctuations in human performance and alertness are accompanied by distinct power spectrum changes of the electroencephalogram (EEG) reordered noninvasively from the scalp (Makeig and Inlow, 1993;Jung, 1995, 1996;Jung et al, 1997;Makeig et al, 2000;Schier, 2000;Craig, 2002, 2005;Peiris et al, 2006;Tassi et al, 2006;Davidson et al, 2007;Huang et al, 2001Huang et al, , 2007aHuang et al, ,b, 2008Huang et al, , 2009). further demonstrated the feasibility of accurately estimating shifts in a subject's alertness level, as indexed by changes in their performance level on a simple auditory target detection task, by monitoring the changes in EEG power spectra or other measures.…”

Signal Processing for Non-Invasive Brain Biomarkers of Sensorimotor Performance and Brain Monitoring

“…For instance, in the study where subjects learn a novel tool, the absence of learning/adaptation could also be due to fatigue. Nevertheless, when considering the spectral power, the frontal biomarkers evidenced here are neither in the same spatial location (frontal midline) nor in the same frequency band (low theta band) than the fatiguerelated EEG power (Makeig et al, 2000;Oken et al, 2006). Similarly, when considering the coherence/PLV, factors such as stress or fatigue imply an increase and not a decrease in phase synchronization and is generally identified for different electrodes pairs and/or frequency bands (Andersen et al, 2009;Lorist et al, 2009) than those found in the tool learning study (see section 3.2).…”