Reduced Alpha power associated with the recall of mentation from Stage 2 and Stage REM sleep

Abstract

Relationships between Alpha (8-12 Hz) activity and cognitive processes during wakefulness raise the possibility of similar relationships between Alpha and cognitive activity during sleep. We hypothesized that Alpha power decreases during both Stage 2 and REM sleep would index the presence of sleep mentation in these stages. Absolute power for six classical EEG bands and three Alpha subbands was calculated for Stage 2 and REM sleep awakenings both with and without mentation recall. In both stages, recall was associated with lower Alpha power, especially with middle Alpha power (9.5-11.5 Hz). Unexpectedly, a similar effect for Delta power (0.5-4.0 Hz) was also observed. The Alpha effect may reflect cognitive elaboration active in the minutes preceding awakening; however, attention and memory processes cannot be excluded. The Delta effect is consistent with prior observations of regular linkages between Alpha and Delta power during sleep.

Ultradian and circadian modulation of dream recall: EEG correlates and age effects

“…Faster oscillations during REM sleep may thus turn out to be an "electrophysiological signature" for dream processing (Llinás and Ribary, 1993). Interestingly, there is also evidence for an inverse relationship between EEG slow-wave activity and dream recall, with higher levels of delta activity associated to no recall conditions during NREM sleep and, particularly, REM sleep (Esposito et al, 2004). Indeed, the inverse association was more robust for REM sleep, indicating that delta power may be a negative index of dream recall.…”

“…Furthermore, less EEG power density in the theta range (5-8.5 Hz) has been reported for successful recall subsequent to NREM sleep (Cajochen et al, 2003). With respect to REM dreaming, alpha activity (Esposito et al, 2004) and widespread 40-Hz oscillations have been associated to increased dream recall (Llinás and Ribary, 1993), as both may induce large functional states for cognitive processing. Faster oscillations during REM sleep may thus turn out to be an "electrophysiological signature" for dream processing (Llinás and Ribary, 1993).…”

“…However, the precise EEG spectral correlates of dream recall are still unclear. One likely candidate is the use of different EEG approaches, such as which sleep stages are taken into account (only NREM or REM sleep or both), and which power spectra are computed for the analysis (NREM sleep delta or REM sleep alpha power, and so forth) (Armitage et al, 1989;Esposito et al, 2004). Another possible explanation is the use of different approaches accounting for dreams, such as qualitative (dream content) or quantitative methods (dream recall and number of dreams) (Stickgold et al, 2001b).…”

“…1, right panel) (Chellappa et al, 2011). Dream recall has been associated with alpha activity in a non-topographic manner (Esposito et al, 2004), and argued as a means to cognitive elaboration active prior to awakening. Interestingly, we observed less alpha activity only in frontal derivations, which hints to a "prefrontal cortex deactivation" during REM dreaming (Maquet et al, 1996), resulting in less higher order analytic reasoning thinking.…”

Recalling and Forgetting Dreams: Theta and Alpha Oscillations during Sleep Predict Subsequent Dream Recall

“…According to previous observations (Esposito et al, 2004), we expected that a successful recall after awakening from NREM stage 2 should be associated with a lower alpha power compared with awakening with no dream recall, larger in corresponding temporo-parietal areas.…”