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Sleep has been found to benefit spatial memory, by enhancing hippocampal-dependent memory consolidation ,elevating different pathways which are responsible for synaptic strength, control plasticity-related gene transcription and protein translation (Dominique Piber, 2021). Hippocampal areas activated in route-learning are reactivated during subsequent sleep (NREM sleep in particular). It was demonstrated in a particular study that the actual extent of reactivation during sleep correlated with the improvement in route retrieval and therefore memory performance the following day. The study established the idea that sleep enhances the systems-level process of consolidation that consequently enhances/improves behavioral performance. A period of wakefulness has no effect on stabilizing memory traces, in comparison to a period of sleep. Sleep after the first post-training night, i.e., on the second night, does not benefit spatial memory consolidation further. Therefore, sleeping in the first post-training night e.g. after learning a route, is most important.

Further, it has been illustrated that early and late nocturnal sleep have different effects on spatial memory. N3 of the NREM sleep, also referred to as slow wave sleep (SWS), is supposed to have a salient role for the sleep-dependent creation of spatial memory in humans. Particularly in the study conducted by Plihal and Born (1999), the performance on mental rotation tasks was higher among participants who had early sleep intervals (23.00–02.00 am) after learning the task compared to the ones who had late sleep intervals (03.00–06.00 am). These results suggest that early sleep, which is rich in SWS, has certain benefits for the formation of spatial memory. When researchers examined whether early sleep would have such an impact on word stem priming task (verbal task), the results were the opposite. This was not surprising for researchers as priming tasks mostly rely on procedural memory, and thus, it benefits more late retention sleep (dominated by REM sleep) rather than early.

Sleep deprivation and sleep has also been a researched association. Sleep deprivation hinders memory performance improvement due to an active disruption of spatial memory consolidation. As a result, spatial memory is enhanced by a period of sleep. Similar results were confirmed by another study examining the impact of total sleep deprivation (TSD) on rats’ spatial memory (Guan et al., 2004). In the first experiment conducted, the rats were trained in Morris water maze for 12 trials in 6 hours to find a hidden platform (transparent and not visible in the water) by using spatial cues in the environment. In each trial, they started from a different point and were allowed to swim for a maximum of 120 s to reach the platform. After the learning phase, they gave a probe trial to test spatial memory (after 24 h). In this trial, the hidden platform was removed from the maze and the time animals spent in the target area (which was occupied by hidden platform before) was a measure of spatial memory persistence. The control rats, who had spontaneous sleep, spent significantly more time in the target quadrant compared to ones who had total sleep deprivation. In terms of spatial learning, which is indicated by the latency to find the hidden platform, there were no differences. For both control and sleep deprived rats, the time required to find a platform was decreasing with every new trial.

In the second experiment, the rats were trained to swim to a visible platform whose location was changed in each trial. For every new trial, the rats started from the opposite side of the platform. After the training in a single trial, their memory was tested after 24 h. Platform was still in the maze. The distance and the time they needed to swim to the visible platform were considered as non-spatial memory measures. No significant difference has been found between sleep deprived rats and control rats. Similarly, in terms of spatial learning, which is indicated by latency to reach the visible platform, there were no significant differences. TSD does not affect non-spatial learning and non-spatial memory.

In reference to the effects of sleep deprivation on humans, Dominique Piber (2021) featured in his literature review the clinical observations which shows that people with severe sleep disorders frequently have abnormalities in spatial memory. As visible in the studies of both, insomnia patients who suffer from a sleep disorder which features interrupted, non-restorative sleep and deficits in cognitive performance during the day, are documented to have a negative performance in a spatial task, in comparison with the healthy participants (Li et al., 2016 ; Chen et al., 2016 ; Khassawneh et al., 2018 ; He et al., 2021 ).

Likewise, dreaming has an important role in spatial memory. A study conducted by Wamsley and Stickgold (2019) proved that participants, who incorporate a recent learning experience into their overnight dream content, show an increased overnight performance improvement. Thus, supporting the hypothesis that dreaming reflects memory processing in the sleeping brain. Moreover, according to the authors, one of the explanations is that maze‐related dreams are indicators that performance‐relevant components of task memory are being reactivated in the sleeping brain. Additionally, the study supports the idea that dream reports can include an experimental learning task during all stages of sleep, including REM and NREM.

Virtual reality (VR) has also been used to study the connection between dreams and spatial memory. Ribeiro, Gounden, and Quaglino (2021) proposed spatialized elements in a VR context and found that after a full night of sleep in a home setting, when the material studied was incorporated into the dream content, the recall performance of these elements was better than the performance obtained after a comparable wake period.