Intrinsic Bursting and Information Transmission by Visual Corticotectal Neurons

大脑的感觉新皮层对于感觉和知觉是必不可少的，这导致了对理解该组织功能特性的强烈努力。锥体细胞约占皮层所有神经元的80%，在第5层有一种特殊类型的锥体细胞，它表现出内在的活动爆发，是在解剖学和生理学上最独特的锥体亚群之一。这些神经元具有特别厚的顶端树突，它们投射出下行轴突，这些轴突分支支配大脑皮层下的多个区域。上丘是由这些爆发性锥体神经元支配的皮层下结构之一，对视觉刺激有反应。已知这种“皮质-顶叶”锥体神经元强烈影响上丘神经元的反应特性，但这种影响的机制尚不清楚。例如，尚不清楚接受野的特性是否通过皮质顶叶输入直接传递到上丘神经元，或者皮质顶叶的影响是否调节了上丘神经元的其他输入。本研究主要探讨清醒状态家兔皮质皮层神经元影响其上丘目标的方式，以及脑电图状态（清醒与困倦状态）如何影响皮质皮层通讯。首先，Swadlow博士将全面、全面地了解单个皮质顶盖神经元对上丘的突触影响，以及这种影响的动力学。他将通过电生理学检查单个皮质顶盖神经元的脉冲（脉冲和单尖峰）在上丘内产生的单突触电流来做到这一点。接下来，Swadlow博士将获得单个皮质顶盖神经元对上丘内特定神经亚群成员的突触影响的局部视图，以及这种影响的动态。为此，他将同时获得皮质顶叶神经元和上丘内特定亚群的细胞外电生理记录，并应用互相关方法推断突触连通性。此外，Swadlow博士将记录皮质顶盖神经元的细胞内情况，并检查与破裂行为相关的阈下感觉事件。拟议的研究将提供重要的见解，以了解在清醒的感知主体中处理感觉皮质信息的方式，以及皮质神经元如何与大脑远端区域的神经元交流并影响神经元。如果我们要了解清醒的、有知觉的哺乳动物的感知机制，这些信息是至关重要的。拟议中的研究还将通过让本科生参与PI的研究，进一步培养未来的神经生物学家。

Award Abstract The sensory neocortex of the brain is essential for sensation and perception, and this has led to an intense effort to understand the functional properties of this tissue. Pyramidal cells comprise about 80% of all neurons in the cortex, and a special type of pyramidal cell in layer-5 that shows intrinsic bursts of activity is one of the most anatomically and physiologically distinctive of pyramidal sub-populations. These neurons have especially thick apical dendrites and they project descending axons that branch to innervate multiple subcortical areas of the brain. The superior colliculus is one of the subcortical structures innervated by these bursting pyramidal neurons and is responsive to visual stimulation. Such "corticotectal" pyramidal neurons are known to strongly influence the response properties of neurons in the superior colliculus, but the mechanism of this influence is still unknown. It is not known, for example, whether receptive field properties are conveyed to superior colliculus neurons directly by corticotectal input, or whether the corticotectal influence modulates other input to the neurons of the superior colliculus. This proposal focuses on the means by which corticotectal neurons influence their targets in the superior colliculus in awake rabbits, and how EEG state (alert vs. drowsy state) may affect corticotectal communication. First, Dr. Swadlow will gain a comprehensive, global view of the synaptic impact of single corticotectal neurons on the superior colliculus, and the dynamics of this impact. He will do this by electrophysiological examination of monosynaptic currents generated within the superior colliculus by the impulses (bursts and single spikes) of single corticotectal neurons. Next, Dr. Swadlow will gain a local view of the synaptic impact of single corticotectal neurons on members of specific neural sub-populations within the superior colliculus, and the dynamics of this impact. To do this, he will obtain simultaneous extracellular electrophysiological recordings from corticotectal neurons and from specific sub-populations within the superior colliculus, and apply cross-correlation methods to infer synaptic connectivity. In addition, Dr. Swadlow will record intracellularly from corticotectal neurons and examine the sub-threshold sensory events related to bursting behavior. The proposed studies will provide important insights into both the manner in which sensory cortical information is processed in an awake, perceiving subject and how cortical neurons communicate with and influence neurons in distant regions of the brain. Such information is crucial if we are to understand the mechanisms of perception in awake, perceiving mammals. The proposed studies will also further the training of future neurobiologists through involvement of undergraduate students in the PI's research.