CA3 NMDA receptors are crucial for rapid and automatic representation of context memory

Catherine J. Cravens, Noelia Vargas-Pinto, Kimberly M. Christian, Kazu Nakazawa

Research output: Contribution to journalArticle

Abstract

It is argued that the hippocampus contributes to acquisition of context-specific memory although neural mechanisms have not been clarified. To evaluate the role of CA3 in context-specific memory, we developed one-trial context discrimination tasks to test acquisition and retrieval of contextual memory in CA3 pyramidal cell-restricted N-methyl-d-aspartate (NMDA) receptor knockout mice. Mutants were unable to discriminate conditioned and no-shock contexts 3 h after one-trial avoidance training. These phenotypes were not evident 24 h after one-trial training or 3 h after multi-trial training. Following one-trial contextual fear conditioning, mutants showed a selective deficit in context discrimination during a retention test 3 h after acquisition, although overall freezing levels were similar to those of the control mice. As in the avoidance task, this context discrimination impairment was not observed 24 h after initial conditioning. Interestingly, extending the post-shock period to 3 min during the one-trial fear conditioning task eliminated the discrimination deficit observed at the 3 h retention interval. These results suggest that: (i) impaired rapid context discrimination during the recall test is dependent on the duration of post-shock period during conditioning; (ii) CA3 NMDA receptors are critically involved in rapid and automatic formation of a unified context memory representation from the sensory information; (iii) CA3 NMDA receptors support contextual pattern separation; (iv) fear memory to foot-shock is acquired without CA3 NMDA receptors. It appears that rapid and automatic context memory representations from one-time experience are mediated, at least in part, by CA3 NMDA receptors.

Original languageEnglish (US)
Pages (from-to)1771-1780
Number of pages10
JournalEuropean Journal of Neuroscience
Volume24
Issue number6
DOIs
StatePublished - Sep 2006
Externally publishedYes

Keywords

  • Avoidance learning
  • Conditioning
  • Fear
  • Hippocampus
  • Knockout mouse

ASJC Scopus subject areas

  • Neuroscience(all)

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