Juxtacellular Characterization of V1 Neurons

描述（由申请人提供）：了解大脑皮层的回路是如何组织的以及它们是如何运作的是神经科学的中心目标。我们一直在研究初级视觉皮层V1，以了解它在视觉中的作用，也因为V1是大脑皮层中最容易理解的区域之一。一方面，我们通常对神经元的感受野特性有详细的了解，从V1的神经元放电到细胞外记录获得的一系列视觉刺激。另一方面，从解剖学的研究中，我们了解了复杂的神经元结构和突触连接模式，包括V1内部和V1与层外皮层之间的突触连接。我们的建议旨在弥合猴子初级视觉皮层回路中神经元结构与其接受野特性之间的差距。我们使用一种叫做松散斑块细胞旁记录的方法来监测细胞外动作电位，这使我们能够对神经元的RF进行功能表征，然后我们用示踪分子标记同一个神经元，随后恢复和重建标记神经元的三维树突和轴突树突。第4a层是外侧膝状核大细胞传入的主要目标，为第4b层提供输入。这两层都有不同形态的神经元。在这两层中也有一系列的感受野特性。我们的第一个目标是表征4ca和4b层的兴奋性神经元。我们将检验这一假设，即存在与不同形态类型相关的不同功能特征。在第6层锥体神经元中，根据其皮层内轴突树突化的模式，有不同的神经元类别。轴突模式与第4层的i细胞和p细胞分裂有关。我们将使用功能测试，使我们能够确定标记的神经元是由大细胞还是小细胞输入主导，除了调整方向，空间频率，时间频率和大小。我们的第二个目标是测试形态类在多大程度上具有特定的功能标签，运动和颜色等通路特定信息如何在不同的皮层回路中保留，以及在已识别的神经元群体中表示求和和包围抑制的程度。抑制神经元被认为在决定V1感受野的突现特性（如定向、方向和大小选择性）中起着特定的作用。兴奋性和抑制性群体之间的调节程度尚不清楚。我们的第三个目标是表征皮层输入层和核内层的抑制性神经元。有许多疾病是由皮层回路的结构-功能异常引起的，包括弱视、癫痫和精神分裂症。了解正常回路如何运作为理解神经元异常提供了机会。

DESCRIPTION (provided by applicant): Understanding how the circuits of the cortex are organized and how they function is a central goal of neuroscience. We have been studying the primary visual cortex, V1, in order to understand its role in vision and also because V1 is one of the best understood regions of the cerebral cortex. On one hand we often have detailed knowledge of the receptive field properties of neurons determined from neuronal firing in V1, to an array of visual stimuli, obtained from extracellular recording. On the other hand from anatomical studies we know about the intricate neuronal architecture and patterns of synaptic connections both within V1 and between V1 and extrastriate cortex. Our proposal aims to bridge the gap between the structure of neurons in circuits in monkey primary visual cortex and their receptive field properties. We use a method called loose-patch juxtacellular recording to monitor extracellular action potentials, that enables us to functionally characterize the RF of the neurons, and then we label same neuron with a tracer molecule and subsequently recover and reconstruct the three dimensional dendritic and axonal arbors of the labeled neurons. Layer 4a, the main target of the magnocellular afferents from the lateral geniculate nucleus, provides input to layer 4b. Both layers have a variety of neurons with distinct morphologies. There is also a range of receptive field properties in the two layers. Our first aim is to characterize the excitatory neurons in layers 4ca and 4b. We will test the hypothesis that there are distinct functional characteristics that associate with distinct morphological types. Among the pyramidal neurons of layer 6 there are distinct classes of neurons based on their pattern of intra-cortical axonal arborization. The axonal patterns are linked to the (vi- and P-cell divisions of layer 4. We will use functional tests that allow us to determine whether labeled neurons are dominated by magnocellular or parvocellular input in addition to tuning for orientation, spatial frequency, temporal frequency and size. Our second aim is to test to what degree morphological classes have specific functional labels, how pathway specific information such as motion and color are retained within different cortical circuits and the extent to which summation and surround suppression are represented within the population of identified neurons. Inhibitory neurons are thought to play specific roles in determining the emergent properties of V1 receptive fields such as orientation, direction and size selectivity. The extent or degree of tuning among the excitatory and inhibitory populations is unknown. Our third aim is to characterize inhibitory neurons in the input and infragranular layers of cortex. There are numerous disorders that are a result of structure-function abnormalities in cortical circuits including, amblyopia, epilepsy and schizophrenia. Understanding how the normal circuits operate provides opportunities for understanding neuronal abnormalities.