Object Recognition Memory and Gamma Synchrony in the Rat Hippocampus Open Access

Trimper, John (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/j3860746g?locale=en
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Abstract

Abstract
Object Recognition Memory and Gamma Synchrony in the Rat Hippocampus
Neuronal oscillations are believed to play a critical role in memory processing.
These rhythmic fluctuations in voltage facilitate the dynamic routing of information to
and from various brain regions by transiently linking distinct groups of cells. A recent
proposal is that intra-hippocampal oscillatory coherence in the slow (30 - 55 Hz) and fast
(65 - 90 Hz) gamma bands reflect the processes of retrieval and encoding, respectively
(Colgin & Moser, 2009). We sought to test this idea by recording local field potentials
simultaneously from hippocampal subregions CA1 and CA3 in rats ( n= 5) as they
performed variants of a novel object recognition memory task. Analyses failed to confirm
the hypothesized relationship between slow gamma coherence and memory retrieval,
indicating instead that slow gamma coherence relates to the processing of spatial and
relational memories. As predicted, oscillatory synchrony in the fast gamma range was
related to memory encoding. However, our results suggest that this relationship was
restricted to the encoding of nonspatial information. The current study advances our
understanding of the functional relationship between hippocampal gamma coherence and
memory, demonstrating a connection between oscillatory synchrony and memory
content.
Keywords: hippocampus; memory; gamma; coherence; object recognition

Table of Contents

Table of Contents
Introduction ..................................................................................................................................... 1
Method ............................................................................................................................................ 3
Subjects ............................................................................................................................... 3
Apparatus ............................................................................................................................ 3
Procedure ............................................................................................................................ 5
Data Analysis ....................................................................................................................... 6
Results ............................................................................................................................................. 8
Histology ............................................................................................................................. 8
Behavior .............................................................................................................................. 8
Local field potentials ......................................................................................................... 10
Discussion ...................................................................................................................................... 14
Slow gamma coherence relates to spatial and relational information content ............... 15
Fast gamma coherence relates to the encoding of nonspatial information .................... 17
Conclusions ....................................................................................................................... 19
References ........................................................................................................................... 21
Figures & Tables ................................................................................................................... 26
Figure 1: Task schematic ................................................................................................... 26
Figure 2: Average changes in exploration times ............................................................... 27
Figure 3: Coherence on laps 1 and 2 for each object type ............................................... 28
Figure 4: Moving window coherogram for coherence changes across laps ..................... 29
Table 1: Significant coherence changes for same object/same location ......................... 30
Table 2: Significant coherence changes for same object/different location .................... 31
Table 3: Significant coherence changes for different object/same location .................... 32

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