STATE DEPENDENT CONTROL OF RETINOGENICULATE TRANSMISSION

描述：（来自研究者摘要）现在很清楚， 背侧丘脑外侧膝状体核（LGN）的功能更多 而不是简单地将视网膜信息传递到视觉皮层。 相反，这种结构充当动态过滤器， 以及有多少视网膜信息传递到视觉皮层。的 控制这种过滤的细胞因素是复杂的神经支配 LGN细胞的模式和内在膜特性。这些都 已经在体内使用麻醉，瘫痪的动物进行了广泛的研究， 或在体外用丘脑切片制备。问题是我们 缺乏关于这些细胞因子如何与更多 动态因素，如行为状态或眼球运动，以控制 通过LGN的视觉处理的功效。动态因素可以 只能在清醒的行为动物身上进行研究的第一个目标 这个提议是为了了解LGN中的细胞如何过滤视网膜 在清醒状态下的信号。在清醒的、被束缚的猫中，我们 计划记录LGN中单个神经元的活动并研究如何 细胞兴奋性和视觉反应的各个方面受到 诸如困倦、定向警觉和集中注意力的状态。 我们通过训练猫在清醒状态下进行各种 视觉任务，我们通过监测动物来评估行为状态， 的表现，并记录脑电图活动。第二 这项建议的目的是了解眼球运动和 眶位调节LGN神经元的传递特性。 我们计划监测LGN细胞的活动之前，期间和之后， 各种注视和扫视任务。录音是由 动物的头部在一个固定的位置和凝视是通过使用监测 巩膜探测线圈技术最后，我们将开始探索一些 LGN动态调节的细胞机制 活动具体来说，我们将确定条件（即， 行为状态、眼球运动或眼眶位置）。导致LGN 细胞以强直或突发放电模式响应。突发 反应反映了电压依赖性低阈值的激活 Ca2+电导，并允许超极化LGN细胞响应 当去极化事件达到尖峰阈值时，拟议 实验解决了神经科学面临的一个重大而持久的挑战， 将认知行为与单个神经元的行为联系起来。 更具体地说，我们希望这些研究提供一个更好的 了解丘脑回路在各种疾病中的作用 觉醒、视觉注意力和眼球运动等方面。另一 这项提议的一个重要方面是了解大脑如何 调节视网膜神经节细胞的爆发反应 传输LGN细胞的爆发性放电是一个通用的实验性的 了解睡眠-觉醒周期的细胞基础的模型， 病态的丘脑皮质节律

DESCRIPTION: (from the investigator's abstract) It is now clear that the lateral geniculate nucleus (LGN) of the dorsal thalamus functions as more than a simple relay of retinal information to the visual cortex. Instead, this structure acts as a dynamic filter, determining what, when and how much retinal information gets passed on to visual cortex. The cellular factors that control this filtering are the complex innervation patterns and intrinsic membrane properties of LGN cells. These have been studied extensively in vivo using anesthetized, paralyzed animals, or in vitro with a thalamic slice preparation. The problem is that we lack information about how these cellular factors interact with more dynamic factors, such as behavioral state or eye movements, to control the efficacy of visual processing through the LGN. Dynamic factors can only be studied in an awake, behaving animal. The first objective of this proposal is to understand how cells in the LGN filter retinal signals during states of wakefulness. In awake, restrained cats, we plan to record the activity of single neurons in the LGN and examine how aspects of cellular excitability and visual responses are influenced by states such as drowsiness, orienting vigilance, and focal attention. We manipulated the awake state by training cats to perform various visuomotor tasks, We evaluate behavioral state by monitoring the animal s performance on these tasks and by recording EEG activity. The second objective of this proposal is to understand how eye movements and orbital position modulate the transfer characteristics of LGN neurons. We plan to monitor the activity of LGN cells before, during and after various fixation and saccade tasks. Recordings are conducted with the animal's head in a fixed position and gaze is monitored by using the scleral search coil technique. Finally, we will begin to explore some of the cellular mechanisms underlying the dynamic modulation of LGN activity. Specifically, we will determine the conditions (i.e., behavioral state, eye movement or orbital position). which cause LGN cells to respond in either a tonic or burst firing mode. Burst responses reflect the activation of a voltage-dependent low threshold Ca2+ conductance, and permit hyperpolarized LGN cells to respond vigorously when depolarizing events reach spike threshold. The proposed experiments address a major and enduring challenge for neuroscience which is to link cognitive behavior to the behavior of single neurons. More specifically, it is our hope that these studies provide a better understanding for the role played by thalamic circuitry in various aspects of arousal, visual attention, and eye movements. Another important aspect of this proposal is to understand how the brain regulates burst responses in LGN cells during retinogeniculate signal transmission. Burst firing in LGN cells serves a general experimental model for understanding the cellular bases of sleep-waking cycles and pathological thalamocortical rhythms.