# Time Course of Sleep Inertia Dissipation in Memory Tasks
## 4 Discussion
[40], tested their participants every 10 min during the first hour, and then every 30 min. As regards the effect of sleep stage at awakening on SI, the present study did not show any differences. [PERSON] et al. [40] showed no SI as a function of waking up during St2 vs. REM sleep, after a normal night's sleep. Moreover, we did not find sleep or SI effects on semantic priming, casting doubt upon the more recent theories of a different effect of REM and NREM sleep on semantic memory [35, 61, 62]. Another study shows that the sleep stage before awakening influences the magnitude of sleep inertia, with deeper sleep with high delta power being associated with subsequent performance impairment and increased latency of the P300 event-related potential (ERP) [63]. Taken together, the data available so far do not clarify whether sleep inertia is simply an epiphenomenon of the carryover from a preceding sleep state or a precise physiological process that ensures a gradual transition from sleep to waking [64]. We would like to add a consideration regarding a possible dissociation between subjective alertness and memory performance. In the literature, it has been reported that subjective alertness may in part moderate an individual's global assessment of performance [65], but that performance rhythms are not directly mediated by levels of subjective alertness [66]. Recent studies have clarified that SI is part of a complex transition of levels of consciousness, namely from different sleep stages to wakefulness [67, 68]. This condition is accompanied by different regional activation/deactivation patterns, possibly reflecting a functional differentiation between cortical/subcortical areas that, in turn, influences human consciousness during the transitional states [69]. Within this perspective, our data bring evidence in favor of a dissociation between systems that regulate subjective vigilance and systems predisposed to memory efficiency. From an adaptive point of view, it is interesting to underline the fact that the procedural memory system already seems to perform well immediately after the last morning awakening. It could guarantee an already effective routine behavior for the new day that is about to begin. For example, many of us, despite being subjectively sleepy, are able to complete the procedures to prepare a hot cup of coffee in the morning as soon as we wake up. Globally, the present research confirms that the SI effect and its dissipation depend on the type of task used and they influence the speed of information processing more directly than the accuracy. These results further confirm the importance of considering the SI effect when planning sleep logistics for personnel who may have to perform complex tasks quickly after an abrupt awakening. Further research development could be addressed to the study of memory by introducing different tasks. It would also be interesting to evaluate working memory to establish a more united framework in terms of the memory processes in this transition phase. Conceptualization, M.O. and V.N. ; methodology, M.O. and V.N. ; formal analysis, V.N. ; investigation, M.O., M.F., L.T., M.M. and V.N. ; data curation, V.N. ; writing--original draft preparation, M.O. and V.N. ; writing--review and editing, M.O., M.F., L.T., M.M. and V.N. ; supervision, V.N. All authors have read and agreed to the published version of the manuscript. This research was funded by MIUR, grant number PRIN 2004-004113175. The study was conducted according to the guidelines of the Declaration of Helsinki, adopted as ethical reference by the Department of Psychology of the University of Bologna. Informed Consent Statement: Informed consent was obtained from all subjects involved in the study. The data presented in this study are available on reasonable request from the corresponding author. The data are not publicly available due to privacy reason. The authors declare no conflict of interest.