The impact of the environment on sensorimotor cortex in rats: Functional organization, connections and behavior

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The emergence of the neocortex and its capacity to be shaped by early sensory and motor experience is the hallmark of mammalian brain evolution. This remarkable plasticity allows the neocortex to be constructed for a multi-sensory context, and to generate flexible behavior throughout a lifetime. While it is well established that early sensory experience can alter the functional organization of sensory and motor cortex, most studies have focused on either the somatosensory or the motor system in isolation, and almost exclusively studied animals reared in relatively restricted laboratory environments. Thus, the extent to which the sensory complexity, variability, and affordances of the early environment impact neural and behavioral development is unknown. Also, whether these types of dynamic environments can increase the capacity for behavioral plasticity throughout a lifetime has never been explored. In the current proposal, rats will be born and reared in two distinct environments; a laboratory cage, or in a large, highly enriched, semi-natural outdoor enclosure. We will determine if the speed with which an animal learns a sensory motor task, the accuracy of performance, and strategy by which novel tasks are learned correlate with, and can predict, differences in the functional organization, neural response properties and connections of the neocortex. We focus on areas involved in sensorimotor integration and motor control that we believe will be highly impacted by rearing condition: the primary somatosensory cortex (S1) and motor cortex (M1). We will use electrophysiological recording techniques to examine the somatotopic organization and neural response properties of S1, and intracortical microstimulation techniques to determine how muscle synergies are represented in M1 and S1. We will also quantify differences in the neuroanatomical connections of M1 and S1 with other cortical fields within and across hemispheres, as well as with the dorsal thalamus and spinal cord. Finally, to determine when these distinct environments have the greatest impact on the functional organization and connections of S1 and M1, we will examine animals at 4 important developmental time points and as adults. These studies will uncover when and how early sensory experience coupled with diverse motor opportunities impact cortical organization and connectivity in the developing brain to generate context-appropriate behavior; and if dynamic and complex sensorimotor environments generate brains and bodies capable of a larger degree of behavioral plasticity throughout a lifetime.