Memory for time of day (time memory) is encoded by a circadian oscillator and is distinct from other context memories

Martin Roland Ralph, Kevin Sam, Omar A Rawashdeh, Sean Cain, Caroline H Ko

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20 Citations (Scopus)


We report that the neural representation of the time of day (time memory) in golden hamsters involves the setting of a 24-h oscillator that is functionally and anatomically distinct from the circadian clock in the suprachiasmatic nucleus (SCN), but is entrained by the SCN acting as a weak zeitgeber. In hamsters, peak conditioned place avoidance (CPA) was expressed only near the time of day of the learning experience (?2?h) for the first days after conditioning. On a 14:10 light:dark cycle, with conditioning at the end of the light period (zeitgeber time 11 [ZT11]), CPA behavior, including time of day memory, was retained for more than 18 d. With conditioning in the early day (zeitgeber time 03 [ZT03]), CPA was completely lost after 5 d but reemerged after an additional 6 d, with the peak avoidance time shifted to ZT11. When the entraining light cycle was shifted immediately following learning at either ZT11 or ZT03, with no additional experience in the training apparatus, peak CPA 18 d later was always found at ZT11 on the shifted light cycles.
Original languageEnglish
Pages (from-to)540 - 547
Number of pages8
JournalChronobiology International
Issue number4
Publication statusPublished - 2013
Externally publishedYes

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