The involvement of entorhinal cortex in cross-modal associative memory

Pao Yue-kong Library Electronic Theses Database

The involvement of entorhinal cortex in cross-modal associative memory

 

Author: Liao, Zhengli
Title: The involvement of entorhinal cortex in cross-modal associative memory
Degree: M.Phil.
Year: 2013
Subject: Memory.
Associative storage.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Rehabilitation Sciences
Pages: xiii, 93 p. : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2639074
URI: http://theses.lib.polyu.edu.hk/handle/200/7135
Abstract: As the gateway of the hippocampal system to the neocortex, the entorhinal cortex (EC) is hypothesized as a hub in the transformation process of recent memory to remote memory. The purpose of this research is to explore the EC's role in the retrieval of recent and remote cross-modal associative memory and identify another behavioral indicator of this kind of association besides freezing percentage. In the first part of the thesis, a within-subject approach was adopted to examine the EC's role in cross-modal associative memory. An association between a visual stimulus and an auditory stimulus was induced by classical fear conditioning. The rats in the EC-intact condition exhibited 96%±2% freezing to the light stimulus in Week 1, while the rats in the EC-inactivated condition showed 2%±1% freezing. This difference lasted for the first three weeks. The result indicated that the EC participated in the retrieval of cross-modal associative memory. The freezing percentages in both conditions approached each other in the last two weeks. The mean freezing percentage in the EC-intact condition decreased to 54%±17% in Week 4, while in the EC-inactivated condition it increased to 34%±5%. This trend indicated that the dependence of the retrieval on EC decreased over time. In the second part of the thesis, a cross-modal association between light and sound was demonstrated by a delay fear conditioning and a cued-reward task. Firstly, the light and sound stimuli were combined as the conditioned stimulus and associated with a foot shock in the experiment group; only the light stimulus and the foot shock were presented to the control group. Secondly, the sound stimulus was used as the cue for water reward. Thirdly, the sound was replaced by the light to examine whether the cued-reward task was an indicator for the cross-modal associative memory. Six out of 7 rats in the experiment group, compared with 1 out of 8 rats in the control group, succeeded in getting the water reward in the first trials of the replacement. This difference between the two groups lasted for the next 20 trials. It indicated that visuoauditory association was formed in the conditioning phase and could be retrieved in the reward phase with the cued-reward task. In summary, the retrieval of cross-modal associative memory depends on the EC and the dependence decreases over time. The cued-reward task can be used as an indicator to represent the cross-modal association between visual and auditory stimuli.

Files in this item

Files Size Format
b26390747.pdf 2.299Mb PDF
Copyright Undertaking
As a bona fide Library user, I declare that:
  1. I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
  2. I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
  3. I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.

     

Quick Search

Browse

More Information