The spatiotemporal organization of episodic memory and its disruption in a neurodevelopmental disorder

Sang Ah Lee,Maria Francesca Bedeschi,Natasha Bertelsen,Marilina Mastrogiuseppe

doi:10.1038/s41598-019-53823-w

Abstract

Recent theories of episodic memory (EM) posit that the hippocampus provides a spatiotemporal framework necessary for representing events. If such theories hold true, then does the development of EM in children depend on the ability to first bind spatial and temporal information? And does this ability rely, at least in part, on normal hippocampal function? We investigated the development of EM in children 2–8 years of age (Study 1) and its impairment in Williams Syndrome, a genetic neurodevelopmental disorder characterized by visuospatial deficits and irregular hippocampal function, (Study 2) by implementing a nonverbal object-placement task that dissociates the what, where, and when components of EM. Consistent with the spatiotemporal-framework view of hippocampal EM, our results indicate that the binding of where and when in memory emerges earliest in development, around the age of 3, and is specifically impaired in WS. Space-time binding both preceded and was critical to full EM (what + where + when), and the successful association of objects to spatial locations seemed to mediate this developmental process.

Highlights

Recent theories of episodic memory (EM) posit that the hippocampus provides a spatiotemporal framework necessary for representing events
To reconcile the role of the hippocampus in EM and spatial navigation, some researchers have suggested that the hippocampal formation (HF) uses space and time as a primary scaffold for coding episodic memories and that other event-defining components are subsequently incorporated into this spatiotemporal framework[7,8]
In Study 2, we investigated how atypical hippocampal development may affect the development of episodic memory binding by conducting a similar test in young adult subjects with Williams Syndrome (WS), a genetic neurodevelopmental disorder characterized by a severe deficit in spatial cognition and irregular hippocampal function

Summary

Introduction

Recent theories of episodic memory (EM) posit that the hippocampus provides a spatiotemporal framework necessary for representing events If such theories hold true, does the development of EM in children depend on the ability to first bind spatial and temporal information? Recent findings illustrating that hippocampal and entorhinal cells represent episodic time[9,10,11,12,13,14,15,16] and studies showing specific impairment in the temporal organization of memories in patients with hippocampal damage (e.g.,17), provide considerable support for the HF’s role in representing both spatial and temporal information. If a spatiotemporal context represented by basic navigation mechanisms provides a scaffold even for coherent memories of non-navigational experiences, it follows that the ability to bind spatial and temporal information into a continuous representation is a requisite for EM. Studies with wider age ranges e.g.,18 suggest that memory for spatial contexts of events may occur earlier in development

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Discussion

Conclusion