Weighting of binocular experience in visual cortical development

After birth the brain adapts to characteristics in the environment in order to optimise its resources with respect to the individual's circumstances. For instance, early monocular deprivation results in reduced cortical representation and visual acuity of the deprived eye. However, such a loss of visual function in one eye after only transient periods of compromised vision through injury or infection would seem to be maladaptive. I examined here whether cortical deprivation effects can be counteracted by daily periods of normal experience. Cats received variable daily regimens of monocular deprivation (by wearing a mask) and binocular exposure. Visual cortex function was subsequently assessed with optical imaging of intrinsic signals, visually evoked potentials, and extracellular electrophysiological recordings. Regardless of the overall length of visual experience, daily binocular vision for as little as 30 minutes, but no less, allowed normal ocular dominance and visual responses to be maintained despite several times longer periods of deprivation. Thus, the absolute amount of daily binocular vision rather than its relative share of the total daily exposure determined the outcome. When 30 minutes binocular exposure were broken up into two 15-minute blocks flanking the deprivation period, ocular dominance resembled that of animals with only 15 minutes binocular vision, suggesting that binocular experience must be continuous to be most effective. My results demonstrate that normal experience is clearly more efficacious in maintaining a binocular visual cortex than abnormal experience is in shifting the ocular dominance distribution. These findings con tribute to the larger debate about how much nature and nurture, respectively, contribute to the development of the brain they suggest that while experience plays a significant role, for some functions there may be an intrinsic bias towards a state that is optimally adapted to the most probable environment.EThOS - Electronic Theses Online ServiceGBUnited Kingdo