Age-associated changes in waking hippocampal sharp-wave ripples

Stephen Leigh Cowen, Daniel T. Gray, Jean Paul L. Wiegand, Lesley A. Schimanski, Carol A Barnes

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Hippocampal sharp-wave ripples are brief high-frequency (120–250 Hz) oscillatory events that support mnemonic processes during sleep and awake behavior. Although ripples occurring during sleep are believed to facilitate memory consolidation, waking ripples may also be involved in planning and memory retrieval. Recent work from our group determined that normal aging results in a significant reduction in the peak oscillatory frequency and rate-of-occurrence of ripples during sleep that may contribute to age-associated memory decline. It is unknown, however, how aging alters waking ripples. We investigated whether characteristics of waking ripples undergo age-dependent changes. Sharp-wave ripple events were recorded from the CA1 region of the hippocampus in old (n = 5) and young (n = 6) F344 male rats as they performed a place-dependent eyeblink conditioning task. Several novel observations emerged from this analysis. First, although aged rats expressed more waking ripples than young rats during track running and reward consumption, this effect was eliminated, and, in the case of track-running, reversed when time spent in each location was accounted for. Thus, aged rats emit more ripples, but young rats express a higher ripple rate. This likely results from reduced locomotor activity in aged animals. Furthermore, although ripple rates increased as young rats approached rewards, rates did not increase in aged rats, and rates in aged and young animals were not affected by eyeblink conditioning. Finally, although the oscillatory frequency of ripples was lower in aged animals during rest, frequencies in aged rats increased during behavior to levels indistinguishable from young rats. Given the involvement of waking ripples in memory retrieval, a possible consequence of slower movement speeds of aged animals is to provide more opportunity to replay task-relevant information and compensate for age-related declines in ripple rate during task performance.

Original languageEnglish (US)
JournalHippocampus
DOIs
StateAccepted/In press - Jan 1 2018

Fingerprint

Sleep
Reward
Running
Inbred F344 Rats
Task Performance and Analysis
Locomotion
Hippocampus
Conditioning (Psychology)
Memory Consolidation

Keywords

  • oscillation
  • reactivation
  • working memory

ASJC Scopus subject areas

  • Cognitive Neuroscience

Cite this

Age-associated changes in waking hippocampal sharp-wave ripples. / Cowen, Stephen Leigh; Gray, Daniel T.; Wiegand, Jean Paul L.; Schimanski, Lesley A.; Barnes, Carol A.

In: Hippocampus, 01.01.2018.

Research output: Contribution to journalArticle

Cowen, Stephen Leigh ; Gray, Daniel T. ; Wiegand, Jean Paul L. ; Schimanski, Lesley A. ; Barnes, Carol A. / Age-associated changes in waking hippocampal sharp-wave ripples. In: Hippocampus. 2018.
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