title: Infant rats can learn time intervals before the maturation of the striatum: evidence from odor fear conditioning.
abstract: Interval timing refers to the ability to perceive, estimate and discriminate durations in the range of seconds to minutes. Very little is currently known about the ontogeny of interval timing throughout development. On the other hand, even though the neural circuit sustaining interval timing is a matter of debate, the striatum has been suggested to be an important component of the system and its maturation occurs around the third post-natal (PN) week in rats. The global aim of the present study was to investigate interval timing abilities at an age for which striatum is not yet mature. We used odor fear conditioning, as it can be applied to very young animals. In odor fear conditioning, an odor is presented to the animal and a mild footshock is delivered after a fixed interval. Adult rats have been shown to learn the temporal relationships between the odor and the shock after a few associations. The first aim of the present study was to assess the activity of the striatum during odor fear conditioning using 2-Deoxyglucose autoradiography during development in rats. The data showed that although fear learning was displayed at all tested ages, activation of the striatum was observed in adults but not in juvenile animals. Next, we assessed the presence of evidence of interval timing in ages before and after the inclusion of the striatum into the fear conditioning circuit. We used an experimental setup allowing the simultaneous recording of freezing and respiration that have been demonstrated to be sensitive to interval timing in adult rats. This enabled the detection of duration-related temporal patterns for freezing and/or respiration curves in infants as young as 12 days PN during odor fear conditioning. This suggests that infants are able to encode time durations as well as and as quickly as adults while their striatum is not yet functional. Alternative networks possibly sustaining interval timing in infant rats are discussed.
authors.affiliation: Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR5292, University Lyon1 Lyon, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Boulanger Bertolus
authors.affiliation: Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR5292, University Lyon1 Lyon, France.
authors.forename: Chloe
authors.initials: C
authors.lastname: Hegoburu
authors.affiliation: Child and Adolescent Psychiatry, Emotional Brain Institute, Nathan Kline Institute, New York University School of Medicine New York, NY, USA.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Ahers
authors.affiliation: Child and Adolescent Psychiatry, Emotional Brain Institute, Nathan Kline Institute, New York University School of Medicine New York, NY, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Londen
authors.affiliation: Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR5292, University Lyon1 Lyon, France.
authors.forename: Juliette
authors.initials: J
authors.lastname: Rousselot
authors.affiliation: Child and Adolescent Psychiatry, Emotional Brain Institute, Nathan Kline Institute, New York University School of Medicine New York, NY, USA.
authors.forename: Karina
authors.initials: K
authors.lastname: Szyba
authors.affiliation: Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR5292, University Lyon1 Lyon, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Thévenet
authors.affiliation: Child and Adolescent Psychiatry, Emotional Brain Institute, Nathan Kline Institute, New York University School of Medicine New York, NY, USA.
authors.forename: Tristan A
authors.initials: TA
authors.lastname: Sullivan-Wilson
authors.affiliation: Centre de Neurosciences Paris-Sud, CNRS UMR 8195, University Paris-Sud Orsay, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Doyère
authors.affiliation: Child and Adolescent Psychiatry, Emotional Brain Institute, Nathan Kline Institute, New York University School of Medicine New York, NY, USA.
authors.forename: Regina M
authors.initials: RM
authors.lastname: Sullivan
authors.affiliation: Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR5292, University Lyon1 Lyon, France.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Mouly
keywords: freezing; infant rats; interval timing; memory; olfactory fear conditioning; ontogeny; respiration; striatum