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. 2012;7(4):e34815.
doi: 10.1371/journal.pone.0034815. Epub 2012 Apr 11.

Environmental Enrichment Promotes Plasticity and Visual Acuity Recovery in Adult Monocular Amblyopic Rats

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Free PMC article

Environmental Enrichment Promotes Plasticity and Visual Acuity Recovery in Adult Monocular Amblyopic Rats

Paola Tognini et al. PLoS One. .
Free PMC article

Abstract

Loss of visual acuity caused by abnormal visual experience during development (amblyopia) is an untreatable pathology in adults. In some occasions, amblyopic patients loose vision in their better eye owing to accidents or illnesses. While this condition is relevant both for its clinical importance and because it represents a case in which binocular interactions in the visual cortex are suppressed, it has scarcely been studied in animal models. We investigated whether exposure to environmental enrichment (EE) is effective in triggering recovery of vision in adult amblyopic rats rendered monocular by optic nerve dissection in their normal eye. By employing both electrophysiological and behavioral assessments, we found a full recovery of visual acuity in enriched rats compared to controls reared in standard conditions. Moreover, we report that EE modulates the expression of GAD67 and BDNF. The non invasive nature of EE renders this paradigm promising for amblyopia therapy in adult monocular people.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Environmental enrichment promotes recovery of visual acuity in adult amblyopic monocular rats.
a) Electrophysiological assessment of visual acuity (VA) showed a significant difference between OND-EE rats and OND-SC animals and between OND-SC rats and untreated controls (grey shadow in the graph), but not between untreated controls and OND-EE rats (One Way ANOVA p<0.001, post-hoc Holm-Sidak test OND-SC vs. OND-EE and untreated controls p<0.05, other comparisons were not significantly different). Insert shows a schematic representation of the apparatus used for VEP recording. b) Representative examples of VA estimates for the previously deprived eye in OND-SC and OND-EE animals. Percentage of normalized VEP amplitude is plotted against log spatial frequency. Visual acuity is obtained by extrapolation to zero amplitude of the linear regression through the data points in a curve where VEP amplitude is plotted against log spatial frequency. *, statistical significance; error bars represent s.e.m.
Figure 2
Figure 2. Environmental enrichment promotes recovery of behavioural perceptual abilities in adult amblyopic monocular animals.
a) Statistical analysis showed that the visual acuity (VA) of the previously deprived eye was not different from that of the other eye (fellow eye) in OND-EE rats (paired t-test, p = 0.51); a statistical difference was instead present between the VA of the previously deprived eye and that of the fellow eye in OND-SC animals (paired t-test, p<0.05). Insert shows a schematic representation of the visual water-box task, the apparatus used for behavioral assessment of visual acuity. b) Representative examples of behavioral VA estimates for both the previously deprived and the fellow eye in OND-SC (left) and OND-EE (right) animals. Visual acuity is obtained by extrapolation to 70% of correct choices on the sigmoidal function fitting the psychometric function in which the percentage of correct choices is plotted against zero spatial frequency. *, statistical significance; error bars represent s.e.m.
Figure 3
Figure 3. Environmental enrichment induces changes of plasticity factors in the visual cortex of adult amblyopic monocular rats.
a) EE decreases GAD67 expression in the visual cortex contralateral to the previously deprived eye. The number of GAD67+ cells was statistically lower in the visual cortex of OND-EE with respect to OND-SC rats (t-test, p<0.001). b) EE increases BDNF expression in the visual cortex contralateral to the previously deprived eye. The number of BDNF+ cells was statistically higher in the visual cortex of OND-EE with respect to OND-SC rats (Mann-Whitney Rank sum test, p = 0.035). *, statistical significance; calibration bar = 40 µm; error bars represent s.e.m.

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