Acceleration of Visual System Development by Environmental Enrichment

Abstract

Thus far, the developmental plasticity of the visual system has been studied by altering or reducing visual experience. Here, we investigated whether a complex sensory-motor stimulation, provided by rearing animals in an enriched environment, affects visual system development. We found that raising mice in this condition causes an earlier eye opening, a precocious development of visual acuity, and an accelerated decline of white matter-induced long-term potentiation. These effects are accompanied by a precocious cAMP response element-mediated gene expression and a significant increase of BDNF protein and GAD65/67 expression in enriched pups. In addition, we showed that enriched pups experienced higher levels of licking behavior provided by adult females. Thus, rearing mice from birth in an enriched environment leads to a conspicuous acceleration of visual system development as ascertained at behavioral, electrophysiological, and molecular level.

The impact of early postnatal environmental enrichment on maternal care and offspring behaviour following weaning

“…Previous studies have shown inconsistent results as to how environmental enrichment impacts on pup licking/grooming of dams. While some (Cancedda et al 2004) found significantly more licking/grooming for female mice living in an enriched environment, others (Welberg et al 2006) did not report any enrichment-induced changes in the amount of pup licking/grooming in rats. The latter would be in line with the present results, although the overall reduced nursing time, alongside the increased time spent eating and drinking, would rather suggest a decreased maternal care.…”

“…However, measuring gross locomotor activity, although non-invasive, does not detect subtle locomotor effects, or provides qualitative insights, e.g., if activity in the pups was more directed towards to or away from objects. Effects primarily on sensory processing (Cancedda et al 2004) cannot be excluded either.…”

“…In the rat as an altricial species, this period is characterised by the impact of maternal care that correlates positively with dampened stress and anxiety responses in the offspring (Liu et al 1997;Caldji et al 1998). Whereas early postnatal enrichment in mice promotes maternal behaviour and development of the offspring (Cancedda et al 2004), the impact on maternal behaviour in rats can be detrimental, but possibly dependent on the innate level of maternal care. Although restricting environmental enrichment to the lactational period, rat studies either did not investigate behaviour in the offspring or they used dams selectively bred for either high or low innate maternal licking or grooming (Mann and Gervais 2011;Champagne and Meaney 2006).…”

Nurturing brain plasticity: impact of environmental enrichment

“…The most relevant result was the demonstration that EE from birth induces a marked acceleration in the maturation of VA, an effect consistently reported in mice and rats using both electrophysiological and behavioural methods. [33][34][35][36] The acceleration effect is quite strong, yielding a 1-week advance in the time course of VA maturation with respect to control animals. This functional outcome is accompanied by a precocious decline in the possibility of inducing LTP of layer II-III field potentials after theta-burst stimulation of the white matter (WM-LTP) in the visual cortex, 34 a well-established in vitro model of developmental plasticity.…”

“…40,41 Indeed, mice raised in EE show increased levels of the BDNF protein in their visual cortex at P7, 34,35 revealing the fact that neurotrophin BDNF is one of the crucial factors that underlie EE effects on V1 maturation. In both BDNF overexpressing mice and EE pups, higher BDNF levels were also shown to trigger the maturation of the inhibitory GABAergic system, which, by affecting receptive field development and synaptic plasticity, could determine both the accelerated maturation of VA and the decline of cortical plasticity.…”