| Abstract No.: | B-D2141 |
| Country: | Canada |
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| Title: | EFFECTS OF ENVIRONMENTAL ENRICHMENT AND BLINDNESS ON CORTICAL SOMATOSENSORY ACTIVITY |
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| Authors/Affiliations: | 1 Robin Tremblay*; 1 Denis Boire; 1 Gilles Bronchti;
1 Université du Québec à Trois-Rivières, QC, Canada
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| Content: | Objectives: Blind peoples show better performances in solving tactile tasks than sighted individuals. This phenomenon could be due to a stronger utilisation of somatosensory system by the blind. It has been proposed that blindness could act as environmental enrichment on non-visual structures. Our purpose is to compare anatomical and functional impacts of blindness and environmental enrichment on the somatosensory system.
Materials and methods: We raised anophthalmic ZRDCT/An mutant mice in standard (AS) or enriched (AE) housing conditions. The C57Bl/6 sighted mouse strain, raised in the same conditions (CS or CE), served as controls. We used the whisker-to-barrel system for our anatomical and functional experiments. Anatomical parameters such as areas of cortex, barrelfield and barrel rows were measured on flat mounted cytocrome oxydase stained sections. To study the posteromedial barrel subfield (BF) activity, we let animals explore an objects-filled box and used semi-quantitavive [14]C-2-deoxyglucose (2-DG) method or c-Fos immunohistochemistry. During the active exploration mice had all whiskers intact, whereas in another set of experiments, all whiskers were cut but the three caudal most of rows B and D on one side of the snout and of row C on the other. Metabolic and functional activity were measured on tangential sections through the BF (i) by densitometry on autoradiographic films (2DG) and (ii) using unbiased stereological quantification procedure (c-Fos). Partial stimulations allowed us to measure activity contrasts (stimulated versus non stimulated barrel rows activity ratios).
Results: We observed that blind mice have smaller cortical surface than sighted animals. However, BF size is not different between the two strains, indicating a higher relative area corresponding to the whiskers representation in the blind as compared to the sighted animals. A closer look on the barrel cortex showed that mutant mice had larger barrels in row A. Among the experimental groups (AS, AE, CS and CE), the control mice raised in the standard environment – CS - exhibited the lowest somatosensory-evoked metabolic activity in BF and the lowest contrasted activity between stimulated and unstimulated rows. Enriched controls and blind mice (AS and AE) exhibited all higher contrasts. The results of the c-Fos experiments confirmed that both blindness and environmental enrichment raise activity contrasts in the barrelfield. We found a higher number of c-Fos immunoreactive cells in non stimulated barrel rows, corresponding to a less segregated activity in standard housed sighted mice as compared to environmentally enriched and blind animals. In addition, environmental enrichment raises 2-DG activity in neighbouring associative cortices. However, in the blind mice, whether from the enriched environment or not, somatosensory stimulation specifically activated parietal association cortex. Coronal sections demonstrated that not only the parietal cortex was activated, but also the primary visual cortex.
Conclusion: Thus, our study demonstrates that both blindness and environmental enrichment have similar effects on SI functionalities in by raising cortical activity and influx segregation. Environmental enrichment also raises the metabolic cortical activity in general. Blindness specifically expands somatosensory activation toward the visual cortex. |
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