Hippocampus, aging, and segregating memories

Tatiana Manrique, Ignacio Moron, Maria Angeles Ballesteros, Rosa Maria Guerrero, Andre A. Fenton, Milagros Gallo

Research output: Contribution to journalArticle

Abstract

Rats use time-of-day cues to modulate learned taste aversion memories. If adult rats are accustomed to drinking saline in the evening and they receive a lithium chloride injection after drinking saline in the morning, they form a stronger aversion to saline than rats that were conditioned after drinking saline at the familiar time. The difference indicated that the rats formed segregated representations of saline taste and the time of day the saline was consumed. This was inferred because the modylation of learning by time of day was observed when the aversions were tested at the familiar evening drinking time. If the rats had formed a compound representation of saline taste and the time of day it was consumed, the opposite pattern of differences would be expected. We used this modulation of learning by time of day to assay whether aged rats have an impaired ability to form segregated representations of experience. We find that aged rats had similar saline aversions if they were conditioned at either the familiar or the unfamiliar time of day. Furthermore, dorsal hippocampal lesions affecting also the overlying parietal cortex in the aged rats caused greater saline aversions if the rats were conditioned after drinking saline at the familiar time of day. This indicated that aged rats are aware of the time of day but after the lesion, they act as if they do not segregate saline taste from the time of day it was consumed. The results suggest that the ability to form segregated representations of a complex experience is impaired in aging and abolished by hippocampal lesions.

Original languageEnglish (US)
Pages (from-to)57-65
Number of pages9
JournalHippocampus
Volume19
Issue number1
DOIs
StatePublished - Jan 2009

Keywords

  • Aging
  • Cognitive segregation
  • Hippocampys
  • Latent inhibition
  • Rat
  • Taste aversion
  • Taste recognition memory
  • Time-of-day

ASJC Scopus subject areas

  • Cognitive Neuroscience

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  • Cite this

    Manrique, T., Moron, I., Ballesteros, M. A., Guerrero, R. M., Fenton, A. A., & Gallo, M. (2009). Hippocampus, aging, and segregating memories. Hippocampus, 19(1), 57-65. https://doi.org/10.1002/hipo.20481