title: Developmental Changes in Hippocampal CA1 Single Neuron Firing and Theta Activity during Associative Learning.
abstract: Hippocampal development is thought to play a crucial role in the emergence of many forms of learning and memory, but ontogenetic changes in hippocampal activity during learning have not been examined thoroughly. We examined the ontogeny of hippocampal function by recording theta and single neuron activity from the dorsal hippocampal CA1 area while rat pups were trained in associative learning. Three different age groups [postnatal days (P)17-19, P21-23, and P24-26] were trained over six sessions using a tone conditioned stimulus (CS) and a periorbital stimulation unconditioned stimulus (US). Learning increased as a function of age, with the P21-23 and P24-26 groups learning faster than the P17-19 group. Age- and learning-related changes in both theta and single neuron activity were observed. CA1 pyramidal cells in the older age groups showed greater task-related activity than the P17-19 group during CS-US paired sessions. The proportion of trials with a significant theta (4-10 Hz) power change, the theta/delta ratio, and theta peak frequency also increased in an age-dependent manner. Finally, spike/theta phase-locking during the CS showed an age-related increase. The findings indicate substantial developmental changes in dorsal hippocampal function that may play a role in the ontogeny of learning and memory.
authors.affiliation: Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, United States of America.
authors.forename: Jangjin
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, United States of America.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Goldsberry
authors.affiliation: Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, United States of America.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Harmon
authors.affiliation: Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, United States of America.
authors.forename: John H
authors.initials: JH
authors.lastname: Freeman
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000254:growth & development / Q000378:metabolism* / Q000473:pathology; D003215:Conditioning, Eyelid / Q000502:physiology*; D004558:Electric Stimulation; D004566:Electrodes; D004576:Electromyography; D005260:Female; D008297:Male; D017966:Pyramidal Cells / Q000473:pathology / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D009435:Synaptic Transmission / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology*; D013997:Time Factors