| Abstract No.: | B-D2133 |
| Country: | Canada |
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| Title: | ENVIRONMENTAL ENRICHMENT ENHANCES CROSS MODAL PLASTICITY IN BLIND MICE |
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| Authors/Affiliations: | 1 Nicole Chabot*; 1 Denis Boire; 1 Gilles Bronchti;
1 Universite du Quebec a Trois-Rivieres, QC, Canada
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| Content: | Various studies demonstrate activity in occipital cortex, normally visual, in blind person undergoing auditory or sensitive task. This compensation appears mainly after early visual deprivation. This supports the hypothesis of a reorganization of sensory pathways in those people, which differs from people that lost their sight later in life. Previous works from our lab have demonstrated that the brain structures involved in this cross modal plasticity are the inferior colliculus (IC), the visual thalamus - the dorsal part of the lateral geniculate nucleus (LGNd) and the primary (V1) and secondary (V2) visual cortices. Those structures can be activated by an auditory stimulus. It has been shown that the enriched environment stimulates cortical development, ease the recuperation following a trauma and leads to a greater number of neurons.
Objective 1: Therefore we wanted to investigate whether environmental enrichment can enhance crossmodal plasticity in the blind.
Material and methods: We used two animal models: a mutant ZRDCT/An mouse strain in which neither the retina nor the optic nerve develop, and a C57BL/6 control mouse. Both strains were grown in standard or enriched environments. We used Nissl counterstaining to investigate the effect of the environment on the size and neuronal density in V1, V2, AC and LGNd.
Results: It appears that control mice have a bigger brain than the mutant mice. In V1, V2, AC and LGNd, the volume and the number of neurons are greater in the control than in the mutant. Interestingly, there was no difference due to the environment.
Objective 2: To investigate the effect of the enrichment on the auditory activation on the structures involved in the crossmodal plasticity, we used c-Fos immunohistochemistry.
Material and methods: All animals had their whiskers trimmed to limit somatosensory activation and were placed in a noise attenuated chamber before the experiment. The next morning, all animals were submitted to white noise bursts for one hour.
Results: No effect of environment on auditory evoked activity was observed in the control mice. In the blind mice raised in enriched environment, the auditory evoked activity is greater in all its aspects. On the other hand, there is a drop of auditory evoked activity in mutant mice raised in impoverished environment. Their auditory activation is even lower than the one observed in the control mice raised in standard environment.
Conclusion: The enriched environment used in this experiment is not a naturalistic one but it is enriched enough to lead to a greater auditory activation in the mutant mice. On the contrary, the standard environment is a very impoverished environment and has a debilitating effect on the mutant mice raised in standard environment. Support Contributed By: NSERC, NATEQ.
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