Synaptic Plasticity in Adult Rat Occipital Cortex Following Short-Term, Long-Term, and Reversal Of, Housing Complexity (Learning, Memory)
Hwang, Hwa-Min Francis
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Permalink
https://hdl.handle.net/2142/77682
Description
Title
Synaptic Plasticity in Adult Rat Occipital Cortex Following Short-Term, Long-Term, and Reversal Of, Housing Complexity (Learning, Memory)
Author(s)
Hwang, Hwa-Min Francis
Issue Date
1986
Department of Study
Neuroscience
Discipline
Neuroscience
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Neuroscience
Language
eng
Abstract
Animals exposed to a complex environment, such as a large wire cage filled with various toys, learn mazes more rapidly than rats reared in laboratory cages. Relative to rats reared individually or socially, i.e., two or three animals per cage, in standard cages, the occipital cortex of these enriched animals is heavier and thicker with more dendritic material. Synaptic studies on young rats, i.e., those reared differently for 30 days after weaning at 23-25 days of age, indicated that the occipital cortex of the enriched animals has more synapses per neuron than those of animals, either reared individually or socially. It is of interest to determine whether equivalent effects occur in mature animals. If they occur in adult brain, it is of interest to determine how rapidly they can be detected and how long they are maintained in the absence of differential housing. To answer these questions, we examined synaptic alterations in occipital cortex of adult hooded rats at various stages of differential housing.
It was found that EC animals had more synapses in layer IV of occipital cortex than SC and IC animals even after just 10 days of differential housing. The increase in synapse numbers due to 30 days of differential housing was largely maintained for at least 30 days following removal from the EC condition to the IC condition. Animals reversed from IC condition to EC condition were found to have more synapses than animals remained in IC condition and reached at the similar level of synapse number to that of animals remained in EC condition. The results of synapse increase due to differential housing were found to be parallel to the increased appearance of polyribosome aggregates (PRA) associated with spine synapses in the rat occipital cortex after experiential housing. It was believed that the PRA associated with synapses plays a role in producing molecule(s) for supporting synapse development. Because the frequency of PRA-associated synapses did not decrease significantly after animals being reversed from EC condition to IC condition, it may be that there are different populations of PRA executing different activity, at least one for synapse formation and the other for synapse maturation or supporting individual synapse efficacy.
The essence of this finding, that synapse formation can occur in the adult brain due to experience and can maintain even after removal of experiential exposure, is comparable with the notion that synaptic connections could be involved in mechanisms of brain information storage.
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