Office: 984 Petit Science Center
Phone: (404) 413-5425
My research is directed toward discovering mechanisms that ensure normal development of the brain and compensate for perinatal brain trauma. In particular, we are interested in the role of sensory experience in directing development of brain circuitry. Our approach is to perturb the relationship between sensory neurons and their central targets early in development, and then to study the resulting alterations in brain circuitry, using behavioral, electrophysiological, anatomical, pharmacological, immunocytochemical, computational, and molecular biological techniques.
Using the retinotectal system, we create a population mismatch between the retina and the optic tectum at birth by removing part of the tectum. The retina then makes a compressed visual map on the tectal fragment. Despite the smaller target, the properties of the tectal neurons remain unchanged. This remarkable conservation of function suggests to us that the mapping of the retina onto the tectum and the functional development of individual target cells are controlled in concert. Our investigations of the mechanisms underlying this plasticity show that the involves both NMDA receptors and inhibitory plasticity. These findings are of general importance in brain development and plasticity. Ongoing studies are addressing the molecular signals controlling topographic map formation, and the nature of the critical period for developmental plasticity in sensory systems.
Using the retinogeniculocortical system, we are investigating the consequences of changing the modality of sensory inputs to cerebral cortical areas. The retina can be induced to innervate the central auditory pathway early in development. This allows us to define the role of sensory input modality in the development and evolution of specific cortical circuitry. Our working hypothesis is that the sensory inputs can direct the formation of appropriate cortical circuitry. We have shown that the early visual experience actively alters the intrinsic and extrinsic excitatory connections of auditory cortex, as well as local inhibitory circuitry. We have been investigating the functional implications of these changes and whether they are responsible for creating the visual response properties we see in auditory cortex. We are also studying the topography of and interactions between visual and auditory neurons in this model of sensory substitution in order to understand how to promote adaptive compensation for brain trauma.