PLASTICITY OF BARREL FIELD INTRACORTICAL CIRCUITRY

描述（由申请人提供）：本研究的目的是了解触须的触觉体验如何改变皮层桶周围隔区神经元的感受野（RF），以及隔区神经元在感觉加工和皮层可塑性中发挥的作用。解剖上，第IV层桶状神经元水平投射到桶周围的隔层，垂直投射到桶上方的第II+III层，形成帽状图案，在每个桶周围重叠。与由特定丘脑VPM输入主导的桶状神经元不同，间隔神经元是丘脑低密度输入和对侧皮质互交输入的皮层目标。当两个须几乎同时受到刺激时，隔膜中的一些细胞表现出增强（促进）的反应。如果在触须刺激之间有20-50毫秒的延迟，桶状细胞对第二个触须的反应被抑制，但在间隔细胞中没有研究它们与位置的关系。我们提出隔是专门的区域，用于修改皮层对由几个触须产生的输入的反应。我们的主要假设是，间隔区域的地形提供了一个分布式的细胞矩阵，在这个矩阵中，通过使用依赖的、皮层内连接的可塑性，可以比较和修改须输入的强度。我们提出间隔细胞作为感觉信息调节器，因为它们整合了几个桶的活动，并相互反馈以修改桶的射频。我们将测试隔膜细胞对桶状细胞反应的经验驱动修改有很大贡献的概念，使用我们开发的可塑性测试，称为“须对可塑性”。具体而言，我们希望定义须经验在确定成人间隔细胞可塑性中的作用，以显示使用依赖的可塑性是如何受到发育调节的。对间隔细胞的这些特征的分析将为桶状野皮层的感觉加工提供重要的新信息。研究结果将有助于更好地理解感觉活动如何改变皮层神经元在整个生命过程中的RF，并且实验将明确由于早期感觉经验不足（感觉剥夺）而在间隔神经元中产生的整合缺陷。

DESCRIPTION (provided by applicant): The goal of the proposed research is to understand how tactile experience with the whiskers modifies the receptive field (RF) of neurons in the septa around cortical barrels, and what role septal neurons play in sensory processing and cortical plasticity. Anatomically, layer IV barrel neurons project horizontally into the septa surrounding the barrels and vertically above the barrel to layers II+III in a cap-like pattern that overlaps around each barrel. In contrast to barrels, which are dominated by specific thalamic VPM inputs, septal neurons are the cortical target of less dense inputs from the thalamus and commissural inputs from the contralateral cortex. When two whiskers are stimulated nearly simultaneously, some cells in the septum show increased (facilitated) responses. If there is a delay of 20-50 ms between whisker stimuli, the response to the second whisker is inhibited in barrel cells, but not studied in septal cells in relation to their location. We propose that the septa are specialized regions for modifying cortical responses to inputs that are generated by several vibrissa. Our main hypothesis is that the topography in the septal regions provides a distributed cell matrix in which the strength of whisker inputs is compared and modified through use-dependent, intracortical connection plasticity. We propose that septal cells operate as sensory information modulators in that they integrate the activity of several barrels and feed back reciprocally to modify barrel RF's. We will test the notion that septal cells contribute strongly to experience-driven modifications of barrel cell responses using a test for plasticity that we developed, called "whisker pairing plasticity". Specifically, we wish to define the role of whisker experience in determining adult septal cell plasticity to show how use-dependent plasticity is developmentally regulated. Analysis of these characteristics of the septal cells will provide significant new information about sensory processing in the barrel field cortex. The results will generate a better understanding of how sensory activity modifies the RF of cortical neurons throughout life, and the experiments will specify integrative deficits that are produced in septal neurons by inadequate early sensory experience (sensory deprivation).