A stable home-base promotes allocentric memory representations of episodic-like everyday spatial memory

Nicola Broadbent, Lucas Berend Lumeij, Marta Corcoles, Alice I Ayres, Mohammad Zaki Bin Ibrahim, Brittany Masatsugu, Andrea Moreno, Jose-Maria Carames, Elizabeth Begg, Lauren Strickland, Theofilos Mazidzoglou, Anna Padanyi, Monica Munoz-Lopez, Tomonori Takeuchi, Marco Peters, Richard G M Morris, Dorothy Tse

Research output: Contribution to journalArticlepeer-review

Abstract

A key issue in neurobiological studies of episodic-like memory is the geometric frame of reference in which memory traces of experience are stored. Assumptions are sometimes made that specific protocols favour either allocentric (map-like) or egocentric (body-centred) representations. There are, however, grounds for suspecting substantial ambiguity about coding strategy, including the necessity to use both frames of reference occasionally, but tests of memory representation are not routinely conducted. Using rats trained to find and dig up food in sandwells at a particular place in an event arena (episodic-like 'action-where' encoding), we show that a protocol previously thought to foster allocentric encoding is ambiguous but more predisposed towards egocentric encoding. Two changes in training protocol were examined with a view to promoting preferential allocentric encoding—one in which multiple start locations were used within a session as well as between sessions; and another that deployed a stable home-base to which the animals had to carry food reward. Only the stable home-base protocol led to excellent choice performance which rigorous analyses revealed to be blocked by occluding extra-arena cues when this was done after encoding but before recall. The implications of these findings for studies of episodic-like memory are that the representational framework of memory at the start of a recall trial will likely include a path direction in the egocentric case but path destination in the allocentric protocol. This difference should be observable in single-unit recording or calcium-imaging studies of spatially-tuned cells.

Original languageEnglish
Pages (from-to)1539-1558
Number of pages20
JournalEuropean Journal of Neuroscience
Volume51
Issue number7
Early online date16 Jan 2020
DOIs
Publication statusPublished - 1 Apr 2020
Externally publishedYes

Keywords

  • event arena
  • frames of reference
  • Humans
  • hippocampus
  • path integration
  • rats

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