Can the natural environment enhance developmental plasticity and adult adaptive behavior? Effects of naturalistic rearing environment on gene expression, adult brain organization, and behavior.

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Project Summary The neocortex is a uniquely mammalian feature, one which facilitates profound behavioral flexibility. Part of this flexibility comes from the capacity of the neocortex to be shaped by early sensory and motor experience, allowing the organism to tune its sensory system to the specific problems and opportunities of the environment in which it is reared. This developmental plasticity allows an animal to then generate adaptive behavior that best meets the variable demands of its environment throughout its life. It has been well established that early sensory experience can alter the sensory or motor representation within a cortical field (cortical maps), neural response properties, and cortical and subcortical connectivity. However, most studies manipulate one particular stimulus in what are necessarily very controlled and restricted environments. Further, it is not known if the differences in the dynamic nature of a given environment (restricted or highly variable) are responsible for brain/behavior alterations early in development, or if a highly dynamic environment can increase the capacity for further change in adult behavior. In the current proposal, we take advantage of a unique resource at UC Davis – field pens located on our Riparian Reserve that are 3,000 times the size of a standard laboratory cage. These field pens provide a highly enriched and dynamic semi-natural environment in which to rear rats. We will quantify tactile natural scene statistics between the semi-natural and laboratory environments, allowing us to quantify differences between the two rearing stimulus conditions, and to subsequently test each group of animals with the full set of stimuli that both groups experienced during development. A number of features of brain organization, gene expression, and behavior will be compared between laboratory rats and rats reared in these semi-natural, highly enriched conditions. While this semi-natural rearing may affect numerous genes, behaviors, and brain regions, we focus on genes associated with cortical development, areal boundary formation, and plasticity. We will sample developing animals to quantify changes in gene expression during critical periods, and relate this expression to adult performance from the same cohort (litttermates) on behaviors that require sensorimotor integration and coordination in adults. We will further quantify neural phenotypes of primary somatosensory cortex (S1), investigating somatotopy, receptive field shape, and cortico-cortical and cortico-thalamic connections. We believe this modality will be highly impacted because the large space available in the field pens will promote active tactile exploration for navigation and social interaction. This is the first study that investigates how early exposure to the rich array of natural stimuli and vastly increased movement options occurring in a natural environment impacts gene expression, neural phenotypes, and behavior.