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”的专门细分组成，但它们在发育或进化过程中是如何产生的尚不清楚。了解这一过程对我们理解人类皮层的功能非常重要。指导这项工作的主要假设是，皮层区域接收的感觉信息在定义其身份和组织其电路方面起着重要作用。因此，即使输入随着进化时间的推移而改变，或者作为对损伤的反应，皮层区域的功能也会自动设计为对其输入的最佳处理。与预先编程的蓝图相反，这种依赖输入的组织将允许对感官输入的变化做出最佳反应。持续的目标是研究发育机制如何促进感觉皮层向其功能专门化区域的进化。本文将采用电生理学和神经解剖学两种方法来研究雪貂皮层发育过程中感觉经验的作用。在一个模型中，新生儿耳聋会产生靶向错误，使视丘脑支配初级听觉皮层（AI）。本文对耳聋引起的神经重新布线的功能结果进行了研究。在另一种范式中，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，听觉皮层在其映射、反应特性和感知能力方面与视觉皮层相似。因此，从功能的角度来看，为人工智能提供早期视觉输入几乎可以将其转变为视觉皮层。这显然是通过一类抑制性皮质神经元的连通性和结构的改变而发生的。该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，这些变化被认为是皮层可塑性的基础。这一信息将证明回路中哪些类型的变化足以使感觉皮层区域在进化过程中获得独特的特性。研究人员将探索通过改变传入活动和/或遗传特性来诱导新的皮层区域的可能性。这些发现将应用于作为大脑进化基础的发育过程模型，特别是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。更广泛的影响：超过30%的佐治亚州立大学的学生是非裔美国人，促进招收少数民族学生从事生物研究。除了正在进行的本科和研究生教育活动外，社区外展活动已经并将包括制定中小学大脑发育和进化课程计划。这些课程将被教师和美国国家科学基金会资助的“生物巴士”使用，该巴士前往亚特兰大市区的学校，为资金不足的公立学校提供实践生物学课程，其中大部分学生是非裔美国人。在美国国家科学基金会行为神经科学中心的背景下，P.I.将继续招收少数民族本科生进行暑期研究，目的是鼓励他们进入研究生院。PI还通过为非专业媒体、广播和电视发表文章，以及通过教育推广和K-12和大学教师之间的网络，努力捍卫格鲁吉亚的进化论教育。见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.