On the road of memory: investigating the relationship between memory, spatial navigation, and Déjà-vu

Objectives: This work has dual objectives, namely investigating the relation between memory and spatial navigation and that between memory and Dèjà-vu. Materials: The experimental protocol included: spatial navigation tasks assessing route (RK), landmark (LK), survey (SK) knowledge and landmark ordering (LO), Survey of Autobiographical Memory (SAM), Prospective and Retrospective Memory Questionnaire (PMRQ), I-DEA questionnaire for assessing Dèjà-vu. Participants and methods: 44 healthy participants took part in this study. Accuracy and a response time index were computed for each spatial navigation task. Four memory dimensions were extracted from SAM: episodic (SAM-E), semantic (SAM-SE), spatial (SAM-SP), and future (SAM-F). Eight factors were extracted from PMRQ, namely Prospective short-term self-cued (PSTSC), Prospective short-term environmentally-cued (PSTEC), Prospective long-term self-cued (PLTSC), Prospective long-term environmentally-cued (PLTEC), Retrospective short-term self-cued (RSTSC), Retrospective short-term environmentally-cued (RSTEC), Retrospective long-term self-cued (RLTSC), Retrospective long-term environmentally-cued (RLTEC). Results: Two-tail Spearman correlations were performed between the abovementioned variables. Results showed a negative correlation between RL and RSTSC; a positive correlation between the response times of RL and SAM-F; a negative correlation between response times on LK and PLTEC; a negative correlation between accuracy on SK and RSTEC and a positive correlation between accuracy on SK and SAM-SP; a negative correlation between accuracy on LO and RSTEC and a positive correlation between response times on LO and SAM-F. Also, results show a positive correlation between I-DEA and SAM-E as well as SAM-F. Discussion: Memory and planning processes have been hypothesized to have evolved from mechanisms developed to support spatial navigation. Our results show that environmental cues, that elicit retrospective short-term memory, can serve as environmental beacons; instead, self-cued retrospective short-memory can play a role when we have to constantly update our location. Both these mechanisms can support path integration and spatial update processes. Dèjà-vu may be associated with different neural responses in several brain regions involved in memory and emotional processes, including the hippocampus. Conclusions: Our results show a connection between Dèjà-vu and the self-perceived abilities to relive past events or imagine future ones. This is consistent with the role of the hippocampus in facilitating the construction of timeless scenes that allow recovering details linked to episodic memories and to imagine future scenes. However, our study is exploratory and further investigations are needed.