# Time Course of Sleep Inertia Dissipation in Memory Tasks
## 4 Discussion  
The present study aimed to investigate the effect of SI and its dissipation on long-term memory systems (semantic, episodic, and procedural) after an uninterrupted nocturnal sleep. According to the taxonomy of memory proposed by [PERSON] and [PERSON] [39], semantic memory contains all the general knowledge, language, symbols, and encyclopedic information about the world; episodic memory involves the conscious recollection of personally experienced events; and procedural memory mainly concerns motor skills, which are learned with simple exercise. The importance of the SI-memory relationship is evident since memory processes play a crucial role in reinstating the levels of cognitive efficiency of wakefulness. Specifically, our purpose was to evaluate: (a) the SI effect after an uninterrupted night's sleep; (b) the time course of SI dissipation by assessing performance at regular intervals for a total time of 80 min; (c) the SI effect assessed by comparing post-sleep performances with diurnal performance collected in the same conditions; and (d) the SI effect in relation  
Figure 3: Graphical representation of the interaction between the experimental condition and experimental trial of subjective alertness. Mean values are reported. to sleep stage of awakening (St2 vs. REM sleep). The main results showed an SI effect on the speed execution of the cognitive tasks and on subjective alertness, independently from sleep stage at awakening. Regarding the SI effect after an uninterrupted night's sleep, we did not find a systematic SI effect on different memory systems. Generally, these results partly confirm that mental functions are diversely sensitive to SI [4, 54, 55]. On this basis, it is possible to consider the results separately according to the different and independent memory systems [56]. In the semantic memory task, we observed an SI effect on RTs for lexical decisions during the first 20 min: participants were slower at detecting an Italian word until the fourth session. With regard to accuracy, we did not find any effects. Our results agreed with those of [PERSON] and [PERSON] [57], suggesting that performance speed and accuracy are differentially affected by SI during the sleep-wake transition [4, 22, 55]. This finding could indicate that RT is an index that is more sensitive to the SI effect. More probably, speed and accuracy could be reliable indices when a sleep deprivation effect is being measured. Indeed, [PERSON] et al. [58] found that both sleepiness and SI determined an increase in RTs, but after a total sleep deprivation (i.e., higher sleepiness while SI was absent), the number of lapses (i.e., accuracy) increased. The results obtained from the episodic memory task could be problematic. Indeed, we expected poor performance due to the difficulty of the task. Instead, the episodic recall, in which time of processing was not assessed, did not prove to be affected by SI. The most probable alternative interpretation is that episodic recovery is a highly complex task that could produce a very high cognitive engagement (both encoding and rehearsal processes involve attention, execution operations, deliberate effort, etc.). As regards procedural memory, no SI effect was observed in the finger tapping task, in line with a previous study [20]. Taken together, these results could indicate that long-term memory systems are differently affected by SI. As previously stated, the participants reached a high accuracy level in all cognitive tasks. This is an interesting result, considering that the subjective alertness in experimental conditions did not reach the control value throughout the whole testing session (i.e., 80 min). Our result regarding subjective alertness was in line with previous studies [24, 40, 41, 42], but we described a linear increase in subjective alertness after awakening instead of an asymptotic pattern [40, 59, 60]. This discrepancy could be explained by the fact that our data collection was carried out every 10 min from awakening, whereas others, such as [PERSON] et al.