The Effects of Repetition and Sequence Length on Hippocampal Memory Trace Reactivation

Persistent Link:
http://hdl.handle.net/10150/194909
Title:
The Effects of Repetition and Sequence Length on Hippocampal Memory Trace Reactivation
Author:
Sutherland, Gary Ralph
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Patterns of hippocampal ensemble activity that occur during a spatial experience are reactivated during subsequent rest periods and slow wave sleep. Connections between active cells are thought to be strengthened, via long term potentiation (LTP), by repeated co-activation during experience, which suggests that the level of memory trace reactivation would increase proportionately with repetition. Alternatively, plasticity associated with memory formation, such as LTP-dependent place field expansion and the induction of activity-dependent immediate early gene, ARC, saturates after only a few laps, indicating that reactivation would plateau after a few repetitions. The length of the repeated sequence may also affect reactivation, since activation of a very short sequence can be repeated more frequently than a long sequence in a given time period. We studied how memory trace reactivation was affected by repetition and the length of the repeated sequence by observing the reactivated patterns of cell-pair correlations after a rat ran laps around a long circular track versus running more laps around a short track. On the shorter track, fewer cells had place fields, but they covered more of the track, resulting in generally stronger correlations among active cells. In addition, neuronal activity was recorded from dorsal and mid-ventral CA1. In mid-ventral CA1, there were fewer place fields in the environment but they were larger, with generally stronger correlations among active cells. The comparison between dorsal and mid-ventral regions is thus analogous to the comparison between the sequence of place fields on a long versus short track, respectively. Although there were more cells active in the dorsal region, but more potent correlations in the middle region, no differences in memory trace reactivation were found with respect to repetitions, track length or hippocampal region. This suggests that although spatial scaling increased along the dorsoventral axis of the hippocampus, reactivation is balanced, and possibly coherent across the hippocampal axis and it is relatively independent of sequence length or number of repetitions, at least when that number exceeds about 20.
Type:
text; Electronic Dissertation
Keywords:
CA1; Hippocampus; memory; reactivation; rodent; sharp wave
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Physiological Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
McNaughton, Bruce L
Committee Chair:
McNaughton, Bruce L

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleThe Effects of Repetition and Sequence Length on Hippocampal Memory Trace Reactivationen_US
dc.creatorSutherland, Gary Ralphen_US
dc.contributor.authorSutherland, Gary Ralphen_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractPatterns of hippocampal ensemble activity that occur during a spatial experience are reactivated during subsequent rest periods and slow wave sleep. Connections between active cells are thought to be strengthened, via long term potentiation (LTP), by repeated co-activation during experience, which suggests that the level of memory trace reactivation would increase proportionately with repetition. Alternatively, plasticity associated with memory formation, such as LTP-dependent place field expansion and the induction of activity-dependent immediate early gene, ARC, saturates after only a few laps, indicating that reactivation would plateau after a few repetitions. The length of the repeated sequence may also affect reactivation, since activation of a very short sequence can be repeated more frequently than a long sequence in a given time period. We studied how memory trace reactivation was affected by repetition and the length of the repeated sequence by observing the reactivated patterns of cell-pair correlations after a rat ran laps around a long circular track versus running more laps around a short track. On the shorter track, fewer cells had place fields, but they covered more of the track, resulting in generally stronger correlations among active cells. In addition, neuronal activity was recorded from dorsal and mid-ventral CA1. In mid-ventral CA1, there were fewer place fields in the environment but they were larger, with generally stronger correlations among active cells. The comparison between dorsal and mid-ventral regions is thus analogous to the comparison between the sequence of place fields on a long versus short track, respectively. Although there were more cells active in the dorsal region, but more potent correlations in the middle region, no differences in memory trace reactivation were found with respect to repetitions, track length or hippocampal region. This suggests that although spatial scaling increased along the dorsoventral axis of the hippocampus, reactivation is balanced, and possibly coherent across the hippocampal axis and it is relatively independent of sequence length or number of repetitions, at least when that number exceeds about 20.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectCA1en_US
dc.subjectHippocampusen_US
dc.subjectmemoryen_US
dc.subjectreactivationen_US
dc.subjectrodenten_US
dc.subjectsharp waveen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePhysiological Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMcNaughton, Bruce Len_US
dc.contributor.chairMcNaughton, Bruce Len_US
dc.contributor.committeememberMcNaughton, Bruce L.en_US
dc.contributor.committeememberBarnes, Carolen_US
dc.contributor.committeememberGothard, Katalinen_US
dc.contributor.committeememberNadel, Lynnen_US
dc.identifier.proquest10103en_US
dc.identifier.oclc659750636en_US
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