Thalamic synchrony and the gating of information flow to cortex

描述（由申请人提供）：丘脑同步在控制信息流向皮层中的作用感觉通路的一个普遍特性是它们不断适应感觉输入特性的变化。适应不仅仅是神经活动的疲劳或衰减，而是可以从根本上改变感觉通路敏感的特征，从而改变通路编码的内容。我们最近的研究表明，通过对大鼠触须系统进行持续的触觉刺激来适应，会导致大脑皮层编码的行为相关特征发生根本性的变化：从对触觉接触的检测到对触觉/触须输入不同速度的区分。这种观察在多大程度上是普遍的，以及它是否在感知上表现出来，目前还没有得到很好的研究。在这个项目中，我们将结合电生理学和相关的功能测量和行为，通过调节丘脑向皮层输入的时间同步性，确定适应是否以牺牲检测为代价增强了识别。我们通过一项综合的、平行的研究，利用麻醉大鼠的触须通路的多种记录技术，并使用专注于触觉刺激的检测和区分的行为任务来进行研究。具体来说，我们将测试适应性是否通过调节丘脑投射输入的同步性（AIM 1），将基本的皮质加工模式从检测转换为识别。我们将直接测试这一中心假设的普遍性，跨越须的偏转速度和方向，以及在须的空间敏锐度的背景下，并确定这种现象是如何通过自适应触觉输入的统计来形成的。其次，我们将直接测试自适应是否在行为过程中将感知性能从检测器转换为鉴别器，以及丘脑同步调节是否介导了这种转换（AIM 2）。大鼠将被训练来检测胡须接触或区分附近胡须的接触，而我们通过在触须特定区域内和跨区域长期植入多电极来监测VPm丘脑的种群活动。意义：长期以来，人们一直认为适应增强了感觉通路中的信息流，人类心理物理学研究确实表明，在某些情况下，适应增强了触觉输入的可辨别性。然而，丘脑皮层回路中潜在的神经表征与由此产生的感知之间的确切联系仍然是神经科学中一个悬而未决的主要问题。我们的目标是否成功将直接决定皮层表征如何通过丘脑输入的调节而改变，以及这种调节对感知的影响。广泛影响：各种脑部疾病，如自闭症、脑震荡和酗酒，会导致空间敏锐度的适应效果受损。我们的目标的成功将为基于感觉的诊断提供更坚实的基础，并可能有助于阐明与这些改变生活的疾病相关的病理生理学。此外，我们探索的一个机制是丘脑同步及其对皮层激活的影响，这与癫痫发作和丘脑疼痛有关。

DESCRIPTION (provided by applicant): The role of thalamic synchrony in gating information flow to cortex A ubiquitous property of sensory pathways is that they continuously adapt to changes in the properties of the sensory input. Adaptation is not simply fatigue or attenuation of neural activity, but instead can fundamentally change the features to which the sensory pathway are sensitive and thus changes what the pathway encodes. We have recently shown that adaptation through ongoing tactile stimulation in the rat vibrissa system induces a fundamental change in what behaviorally relevant features the cortex encodes: from detection of a tactile contact to discrimination between different speeds of the tactile/whisker input. To what extent this observation is general and whether it manifests perceptually has not been well studied. In this project, using a combination of electrophysiology and related functional measures and behavior, we will determine whether adaptation enhances discrimination at the expense of detection through modulation of the timing synchrony of thalamic input to cortex. We do so through an integrated, parallel study using multiple recording techniques in the vibrissa pathway of the anesthetized rat, and using behavioral tasks focused on detection of and discrimination between tactile stimuli. Specifically, we will test whether adaptation switches the fundamental cortical processing mode from detection to discrimination through modulation of synchrony of projecting thalamic input (AIM 1). We will directly test the generality of this central hypothesis across whisker deflection speed and direction, and in the context of spatial acuity across whiskers, and determine how this phenomenon is shaped by the statistics of the adapting tactile input. Second, we will directly test whether adaptation switches perceptual performance from detector to discriminator during behavior and whether modulation of thalamic synchrony mediates the switch (AIM 2). Rats will be trained to either detect whisker contact or discriminate between contacts of nearby whiskers, while we monitor population activity in VPm thalamus through chronically implanted multi-electrodes within and across vibrissa-specific regions. Significance: It has long been posited that adaptation acts to enhance information flow in sensory pathways and human psychophysical studies have indeed shown that in certain circumstances adaptation acts to enhance discriminability of tactile inputs. However, the precise link between the underlying neural representations in the thalamocortical circuit and the resultant percept remains a major open question in neuroscience. Success of our aims will directly determine how the cortical representation changes through modulation in thalamic input and the consequences of this on perception. Broad Impacts: Various brain pathologies such as autism, concussive injuries, and alcoholism result in an impaired effect of adaptation on spatial acuity. Success of our aims will provide a more solid foundation for sensory-based diagnostics, and may help to shed light on the pathophysiology associated with these life-altering disorders. Further, one mechanism that we explore is that of thalamic synchrony and its effect on cortical activation, which has been implicated in seizure generation and thalamic pain. PUBLIC HEALTH RELEVANCE: Sensory input is critical in our daily lives, for both the perception of the world around us, and in providing feedback for our muscle systems that help us interact with the external world. How the nervous system performs this feat, and precisely how this helps us in our environment, is unknown. Discovery in this area can potentially help us understand a number of disorders/diseases of the nervous system for which individuals exhibit loss of acuity/sensitivity, and do not have the ability to adapt to changes in the sensory environment.