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, 2011), we calculated the topographic distribution of the peak frequency of the oscillatory theta activity (6.06 Hz; Figure ?Figure2B2B). In other words, we detail the topographic distribution of the mean proportion of time in which oscillations were detected (Pepisode) in correspondence of the peak frequency of interest (6.06 Hz) in the 5-min intervals GSK2118436 preceding awakening, associated to REC and NREC conditions. The statistical map (Figure ?Figure2B2B) points to a robust difference between REC and NREC conditions, significant in correspondence of Fc1 (t = 3.60, p = 0.015). Although not significant after the correction, the differences in theta oscillations are also remarkable at Fz (t = 2.81, p = 0.037) and F3 (t = 2.78, p = 0.039), suggesting that the increase of theta oscillations in the REC condition spreads to most of the frontal area. Discussion Our preliminary data are substantially coherent with previous findings, supporting the idea that higher frontal theta oscillations (and theta activity) are associated to a successful DR (Marzano et al., 2011). Keeping in mind the relationship between frontal theta activity and memory processes (Hsieh and Ranganath, 2014; Scarpelli et al., 2015), if confirmed on a larger sample, these results may provide further support to the hypothesis that the mechanisms of encoding and retrieval of episodic memories remain buy PD-0332991 the same across wakefulness and sleep (De Megestrol Acetate Gennaro et al., 2011; Marzano et al., 2011). Moreover, our results provide arguments in favor of the ��state-like hypothesis,�� according to which the EEG correlates of DR depend on the physiological background of the sleep state in the segment closer to the time of dream report collection, rather than on stable interindividual EEG pattern characterizing each subject. Notably, the difference between REC vs. NREC conditions is significant only for the BOSC analysis. In other words, although the topographical differences are substantially coherent across the FFT and BOSC analyses, nevertheless differences are larger when comparing theta oscillations. It is possible that this specific difference may be explained by the relatively small sample size. On the other hand, this finding may also suggest that the predictive relation between EEG and presence/absence of DR mostly depends on the oscillatory theta activity, more than on tonic (background) theta activity. This would strengthen the coherence of the present results with those obtained during wakefulness on the relation between theta oscillations and encoding/consolidation of episodic memory. It is worth noting that theta activity (as calculated by FFT routines) is also an expression of homeostatic processes during sleep (even during REM sleep: Marzano et al., 2010).
