Brain Topogr (2017) 30:629–638
Predicting Dream Recall: EEG Activation During NREM Sleep
or Shared Mechanisms with Wakefulness?
· Aurora D’Atri
· Anastasia Mangiaruga
· Cristina Marzano
· Cinzia Schiappa
· Michele Ferrara
· Luigi De Gennaro
Received: 5 December 2016 / Accepted: 18 April 2017 / Published online: 22 April 2017
© Springer Science+Business Media New York 2017
in conﬂict with the hypothesis of common wake-sleep
mechanisms. We also conﬁrmed that EEG correlates of DR
depend on a state-like relationship.
Keywords Dream recall · EEG correlates · NREM sleep ·
Nap · Activation model · Delta activity
Although in the last years many studies have tried to
explain how we remember dreams, there are still no une-
quivocal empirical data about EEG correlates of dream
recall (DR). It is well-known that we cannot have directly
access on dream experience, so several works investigated
the EEG pattern related to the subsequent dream reports,
which are—intrinsically—retrospective (Chellappa et al.
2011; Esposito et al. 2004; Marzano et al. 2011a; Scarpelli
et al. 2015a; Siclari et al. 2014; Takeuchi et al. 2003).
For decades, the history of dream research has been
strongly inﬂuenced by the dichotomy REM sleep = dream-
ing versus NREM sleep = non-dreaming (Scarpelli et al.
2015b). More complex designs and interview techniques
highlighted the fallacy of this postulate (Cipolli et al. 2016).
Indeed, a DR rate of about 50% is obtained after awakening
from NREM sleep, especially from stage 2 (Foulkes 1962;
Pivik and Foulkes 1968) and also naptime (Foulkes 1962;
Taub 1971). Despite it is well-known that the dreaming is
not just an epiphenomenon of REM sleep and the dichot-
omy is now outdated, very few explanations on the encod-
ing and retrieval of dream contents from NREM sleep have
Under the assumption that dream recall is the only (and
viable) object of study, some evidence showed that the
mechanisms responsible for DR are substantially the same
Abstract The common knowledge of a uniqueness of
REM sleep as a privileged scenario of dreaming still per-
sists, although consolidated empirical evidence shows that
the assumption that dreaming is just an epiphenomenon
of REM sleep is no longer tenable. However, the brain
mechanisms underlying dream generation and its encoding
in memory during NREM sleep are still mostly unknown.
In fact, only few studies have investigated on the mecha-
nisms of dream phenomenology related to NREM sleep.
For this reason, our study is speciﬁcally aimed to elucidate
the electrophysiological (EEG) correlates of dream recall
(DR) upon NREM sleep awakenings. Under the assump-
tion that EEG activity predicts the presence/absence of DR
also during NREM sleep, we have investigated whether DR
from stage 2 NREM sleep shares similar brain mechanisms
to those involved in the encoding of episodic memory
during wakefulness, or it depends on the speciﬁc electro-
physiological milieu of the sleep period along the desyn-
chronized/synchronized EEG continuum. We collected DR
from a multiple nap protocol in a within-subjects design.
We found that DR is predicted by an extensive reduction
of delta activity during the last segment of sleep, encom-
passing left frontal and temporo-parietal areas. The results
could represent an update on the mechanisms underlying
the sleep mentation during NREM sleep. In particular, they
support the hypothesis that an increased cortical EEG acti-
vation is a prerequisite for DR, and they are not necessarily
* Luigi De Gennaro
Department of Psychology, Sapienza University of Rome,
Via dei Marsi, 78, 00185 Rome, Italy
Department of Biotechnological and Applied Clinical
Sciences, University of L’Aquila, Coppito, L’Aquila, Italy