Role of Sensory Experience in Parcellation of Sensory Neocortex

Georgia State University Research Foundation, Inc., Atlanta GA

Investigators

Abstract

Project Summary Cerebral cortex in mammals is composed of multiple specialized subdivisions called "areas", but how they arise during either development or evolution is not known. An understanding of this process is important for our ability to understand how human cortex functions. The major hypothesis guiding this work is that sensory information received by a cortical area plays a significant role in defining its identity and organizing its circuitry. The function of a cortical area would thus be automatically designed for optimal processing of its inputs, even if inputs change over evolutionary time or as a response to injury. In contrast to a preprogrammed blueprint, this input-dependent organization would allow an optimal response to changes in sensory inputs. The continuing goal is to examine how developmental mechanisms could facilitate evolution of sensory cortex into its functionally specialized areas. Two paradigms will be used to investigate the role of sensory experience in cortical development in ferrets, using electrophysiological and neuroanatomical approaches. In one model, neonatal deafening produces errors in targeting such that visual thalamus innervates primary auditory cortex (AI). An investigation into the functional result of the deafness-induced rewiring is proposed here. In the other paradigm, immature retinal axons are encouraged to invade the auditory thalamus, providing visual input to A1 via the auditory pathway. Physiological study showed that as a result of the procedure, auditory cortex comes to resemble visual cortex in its mapping, response properties, and perceptual capability. Thus it appears that supplying AI with early visual input can nearly transform it into visual cortex from a functional standpoint. This apparently occurs through alterations in connectivity and in structure of a class of inhibitory cortical neurons. The objectives for this model are to continue to define the functional implications of the changes in connectivity and neuronal morphology believed to underlie cortical plasticity. This information will demonstrate what types of changes in circuitry would be sufficient for a sensory cortical area to acquire unique properties during evolution. The possibility that changing afferent activity and/or genetic identity can induce a new cortical area will be explored. The findings will be applied to models of developmental processes that act as a basis for brain evolution, and in particular models of how the number and specialization of sensory cortical areas increased during mammalian evolution. Broader Impact: Over 30% of Georgia State University students are African-American, facilitating recruitment of minority students into biological research. In addition to ongoing activities in undergraduate and graduate education, community outreach activities have and will include development of elementary and middle school lesson plans in brain development and evolution. These lessons will be adapted for use by teachers and in the NSF-funded "Bio-Bus" that travels to metro Atlanta area schools, providing hands-on biology lessons particularly for under-funded public schools with a majority African-American student population. In the context of the NSF Center for Behavioral Neuroscience, the P.I. will continue to recruit minority undergraduate students for summer research experiences with the goal of encouraging them toward graduate school. The PI has also worked to defend evolution education in Georgia through articles for the lay press, radio and TV, and through educational outreach and networking between K-12 and university faculty. See http://www.georgiascience/org.