Role of Sensory Experience in Parcellation of Sensory Neocortex

哺乳动物的大脑皮层由多个被称为“区域”的专门化区域组成，但它们是如何在发育或进化过程中出现的尚不清楚。对这一过程的理解对于我们理解人类大脑皮层的功能是很重要的。指导这项工作的主要假设是，大脑皮层区域接收到的感觉信息在确定其身份和组织其回路方面发挥着重要作用。因此，皮质区域的功能将被自动设计为对其输入的最佳处理，即使输入随着进化时间的推移而改变或作为对损伤的反应。与预先编程的蓝图不同，这种依赖输入的组织将允许对感觉输入的变化做出最佳反应。继续的目标是研究发育机制如何促进感觉皮质向其功能专门化区域的进化。使用电生理学和神经解剖学的方法，我们将使用两种范式来研究感觉体验在雪貂皮质发育中的作用。在一个模型中，新生儿耳聋会在目标定位上产生错误，以至于视觉丘脑支配初级听觉皮质(AI)。本文对耳聋重新布线的功能结果进行了研究。在另一种模式中，未成熟的视网膜轴突被鼓励侵入听觉丘脑，通过听觉通路向A1提供视觉输入。生理学研究表明，由于这一过程，听觉皮质在其映射、反应特性和感知能力方面变得与视觉皮质相似。因此，从功能的角度来看，为人工智能提供早期的视觉输入几乎可以将其转变为视觉皮质。这显然是通过改变一类抑制性皮质神经元的连接性和结构来实现的。这个模型的目标是继续定义连接和神经元形态变化的功能含义，据信这些变化是皮质可塑性的基础。这些信息将证明，在进化过程中，什么类型的电路变化足以让感觉皮层区域获得独特的特性。改变传入活动和/或遗传特性可以诱导新的皮质区域的可能性将被探索。这些发现将被应用于作为大脑进化基础的发育过程模型，特别是在哺乳动物进化过程中感觉皮质区域的数量和专门化如何增加的模型。广泛的影响：超过30%的佐治亚州立大学学生是非洲裔美国人，这促进了少数族裔学生进入生物学研究。除了正在进行的本科生和研究生教育活动外，社区外展活动已经并将包括制定关于大脑发育和进化的小学和中学课程计划。这些课程将被改编成供教师使用，并将在NSF资助的“生物巴士”(Bio-Bus)中使用，该项目将前往亚特兰大市区的学校，为资金不足的公立学校提供动手生物课程，这些公立学校的学生主要是非洲裔美国人。在NSF行为神经科学中心的背景下，P.I.将继续招募少数族裔本科生进行暑期研究体验，目的是鼓励他们进入研究生院。PI还通过为非专业媒体、广播和电视撰写文章，以及通过K-12和大学教职员工之间的教育外展和网络，为佐治亚州的进化论教育辩护。请参阅http://www.georgiascience/org.

Project SummaryCerebral 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.