Corticothalamic Neurons in Sensorimotor Cortex

描述（由申请人提供）：皮质丘脑（CT）轴突是丘脑皮质轴突的10倍，这一激动人心的发现强化了长期以来的观点，即大脑皮层通过CT神经元动态调节其自身的输入。然而，皮质丘脑回路的作用仍然是一个很深的谜。这是因为在标准实验条件下，相当大比例，甚至可能是大多数的CT细胞是沉默的。最近，我们发现在大鼠的初级躯体感觉皮层中，弱反应的CT细胞，甚至一些本来沉默的细胞，在运动皮层的地形学对应区域的触觉刺激诱导的易化过程中，对面部胡须的触觉刺激变得更敏感。因此，来自其他功能相关的新皮层区域的输入可以直接影响感觉皮层中CT神经元的兴奋性，从而影响丘脑皮层回路中传入感觉信号的处理。了解这些位于战略位置的神经元可能传递的信息的性质可能会提供新的和重要的见解皮层功能及其在感觉运动行为的调节。该研究计划采用体内和体外方法相结合，以检查大鼠体感系统中CT神经元的内在电生理特性，突触输入和感受野。新的研究结果将获得两种不同类型的皮质丘脑投射系统长期假设在感觉处理过程中发挥明显不同的作用，在主动触摸。这项研究计划应该会对大脑皮层在信息处理状态下是如何调节自己的活动的--也许还有为什么--产生新的见解。

DESCRIPTION (provided by applicant): The provocative finding that there are 10-fold more corticothalamic (CT) than thalamocortical axons reinforces the long-standing view that the cerebral cortex dynamically regulates its own input via CT neurons. However, the role of corticothalamic circuitry remains a deep mystery. This is because a substantial proportion, perhaps even a majority, of CT cells are silent under standard experimental conditions. Recently, we have found in rat primary somatosensory cortex that weakly responsive CT cells, and even some that are otherwise silent, become more responsive to tactile stimulation of facial whiskers during pharmacologically- induced facilitation of the topographically corresponding area of motor cortex. Thus, inputs from other, functionally related neocortical areas can directly influence the excitability of CT neurons in sensory cortex and hence the processing of afferent, sensory signals in thalamocortical circuits. Understanding the nature of information that is potentially transmitted by these strategically located neurons will likely provide new and important insights into cortical function and its regulation during sensorimotor behaviors. The research plan employs a combination of in vivo and in vitro approaches to examine intrinsic electrophysiological properties, synaptic inputs and receptive fields of CT neurons in the rat somatosensory system. Novel findings will be obtained from two different types of corticothalamic projection systems long-postulated to play distinctly different roles in sensory processing during active touch. The research plan should lead to new insights into how - and perhaps, why - the cerebral cortex regulates its own activity during information processing states.