DYNAMIC PROPERTIES OF VISUAL CORTICAL CIRCUITS

雪貂和猫纹状体第四层神经元的感受野 皮质是定向的，长方形的，通常也是末端抑制的。 这种复杂性与 细胞在外侧膝状核中只有一个突触，它有一个 圆形、中心环绕的组织。中国的长期目标是 这里描述的项目是研究大脑的突触生理学。 纹状体皮质中的特征通路，以逐步了解如何 感觉输入是通过它所穿越的突触来重组的。 1965年，胡贝尔和威塞尔提出了一个用于响应的模型电路 结束停止的性质。他们认为，具有长接受能力的细胞 场可能会与末端停止区域重叠，并抑制那里的活动。 在接下来的几十年里，解剖学研究的结果 在活体内进行的细胞外录音导致了更详细的 原始假说的表述。目前的理论认为，最终- 第4层中的停止是从第6层通过双突触传递的 抑制性连接。的特定身份和连接性 提供抑制作用的细胞仍有待建立。 这一假说的一个中心预测是，层的激活 6应该对由以下因素驱动的突触事件有净抑制作用 膝状体皮质输入的细胞对应于那些结束- 被禁止了。来自脑片的全细胞录音将用于测试 这一预测。具体地说，对激活 丘脑和层间通路将单独和一起 与第4层中的单个单元格进行比较。所有单元格将被标记 细胞内允许生理学和解剖学之间的联系。 必要时，将从视觉上的神经元进行记录 在研究之前确定，以确保关于密钥信息 少数群体，如抑制细胞，是获得的。小路- 具体的集成将通过分析在更细的粒度上进行检查 在每个专业从一个细胞到下一个细胞提供的统一反应 丘脑和板层环路上的突触站。 了解大脑在日常情况下是如何运作的 一个标准，用来判断在这个过程中发生的变化 各种疾病以及用于测试药物的模型系统 用来治疗疾病的。从这个角度来看，视觉皮质是 一个显而易见的研究地点；它的功能和解剖结构被更好地理解 比其他任何皮质区域都要多。对突触有更深的了解 机制提供了对过程中出错过程的洞察 疾病。这里提出的工作直接涉及到 弱视的研究，检查如何异常的视觉体验 导致了中央处理的变化。

The receptive fields of neurons in layer 4 of the ferret and cat striate cortex are oriented, rectangular and frequently end-inhibited as well. this complexity stands in marked contrast to the receptive fields of cells one synapse away in the lateral geniculate nucleus, which have a circular, center-surround organization. The long-term goal of the project described here is to investigate the synaptic physiology of characteristic pathways in striate cortex to understand, stepwise, how sensory input is restructured by the synapses it traverses. In 1965, Hubel and Wiesel proposed a model circuit for the response property of end-stopping. They suggested that cells with long receptive fields might overlap the end-stopped regions and suppress activity there. Over the intervening decades, the results of anatomical investigations and extracellular recordings made in vivo have led to a more detailed formulation of the original hypothesis. current theory holds that end- stopping in layer 4 is relayed from layer 6 through a disynaptic inhibitory connection. The specific identity and connectivity of the cells providing the inhibition remain to be established. A central prediction of this hypothesis is that the activation of layer 6 should have a net inhibitory effect on synaptic events driven by geniculocortical inputs for cells corresponding to those which are end- inhibited. Whole-cell recordings from brain slices will be made to test this prediction. Specifically, the responses to activation of the thalamic and interlaminar pathways alone as well as together will be compared for single cells in layer 4. All cells will be labelled intracellularly to allow correlation between physiology and anatomy. When necessary, recordings will be made from neurons that are visually identified prior to study in order to ensure that information about key minority populations such as inhibitory cells is acquired. Pathway- specific integration will then be examined at a finer grain by analyzing the unitary response provided from one cell to the next at each major synaptic station along the thalamic and interlaminar circuits. A knowledge of how the brain operates in the everyday situation provides a standard against which to judge changes that occur in the course of various disorders as well as a model system on which to test drugs developed to treat illness. From this perspective, the visual cortex is an obvious site to study; its function and anatomy are better understood than any other cortical region. A deeper understanding of synaptic mechanisms provides insight into the processes that go awry during disease. The work proposed here bears directly on a central theme in research on amblyopia, the examination of how abnormal visual experience leads to changes in central processing.