title: Retention of a 24-hour time memory in Syrian hamsters carrying the 20-hour short circadian period mutation in casein kinase-1ε (ck1εtau/tau).
abstract: Circadian rhythmic expression of conditioned place avoidance (CPA) was produced in Syrian hamsters homozygous for the circadian short period mutation, tau. In constant dim red light neither the 20 h endogenous period, nor a 20 h place conditioning schedule eliminated the 24 h modulation of CPA behavior described previously for wild type (wt) hamsters and other species. Tau mutants exhibited a 20 h rhythm superimposed on the 24 h modulation. The 20 h component was removed selectively with lesions of the suprachiasmatic nucleus. Wt animals conditioned on a 20 h schedule did not produce a 20 h rhythm, but still expressed the 24 h modulation. The results show that the context entrainable oscillator (CEO) underlying memory for the timing of an unconditioned stimulus, retains a period of about 24 h regardless of clock gene background (tau mutation) and/or the conditioning schedule (24 vs 20 h). Therefore the CEO responsible for time memory is distinct from the biological clock controlling activity; the underlying circadian molecular mechanisms may differ from the ubiquitous transcription-translation feedback oscillator; and time memory itself is not classically conditioned.
authors.affiliation: Department of Psychology, University of Toronto, 100 Saint George Street, Toronto, Ontario M5S3G3, Canada. Electronic address: Sean.Cain@monash.edu.
authors.forename: Sean W
authors.initials: SW
authors.lastname: Cain
authors.affiliation: Department of Psychology, University of Toronto, 100 Saint George Street, Toronto, Ontario M5S3G3, Canada.
authors.forename: Jeena
authors.initials: J
authors.lastname: Yoon
authors.affiliation: Department of Psychology, University of Toronto, 100 Saint George Street, Toronto, Ontario M5S3G3, Canada.
authors.forename: Tenjin C
authors.initials: TC
authors.lastname: Shrestha
authors.affiliation: Department of Psychology, University of Toronto, 100 Saint George Street, Toronto, Ontario M5S3G3, Canada. Electronic address: ralph@psych.utoronto.ca.
authors.forename: Martin R
authors.initials: MR
authors.lastname: Ralph
mesh_terms: D000818:Animals; D048149:Casein Kinase 1 epsilon / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D003213:Conditioning, Psychological / Q000502:physiology; D006224:Cricetinae; D008297:Male; D008568:Memory / Q000502:physiology*; D008647:Mesocricetus; D009154:Mutation; D013493:Suprachiasmatic Nucleus / Q000502:physiology*
chemical_list: D048149:Casein Kinase 1 epsilon
keywords: Circadian; Clock; Hamster; Learning; Memory; Period; Place conditioning; Tau