Cortical and thalamic mechanisms of selective auditory attention

描述(申请人提供)：大脑必须过滤大量涌入的感觉信息，以选择与其当前目标相关的信息，以便适当地引导适应行为。虽然对猕猴的研究已经确定了注意力对视觉处理的许多潜在作用机制，但很少有研究研究听觉系统中的相应影响。最近的发现提出了我们的首要假设，即注意力通过调节大脑中不同功能区的局部兴奋性和信息的动态路由，以牺牲被忽视的刺激为代价，增强了对所关注刺激的感觉表征。这项研究的主要目标是检验这一假说，从而确定这些相互关联的局部和基于网络的过程的机制，以及它们在听觉加工层次结构的不同节点中对注意听觉刺激加工的相对贡献。根据我们的假设，注意调节正在进行的振荡活动，以使其属性(频率和相位)与所关注的刺激流(分别是时间结构和音调)的全局声学特征相匹配，从而创建该流的阈值下神经元振荡形式的内部模型。这允许振荡起到基于模板的过滤机制的作用，该机制分离相关的流并沿着听觉对象的基本组织维度增强其处理。与此平行的是，跨分级处理阶段的振荡活动的对齐通过提供与所关注的听觉流的时间结构捆绑在一起的用于通信的公共时间参照系来偏向相关信息的传输。局部增强和基于网络的通信效果的关键是通过振荡相位重置使振荡相位与相关事件的定时对齐。越来越多的证据表明，相位重置是由丘脑直接的非丘脑皮质传入启动的，并通过丘脑的网状核受到自上而下的注意的调节。我们的第一个具体目标是确定布景 这些规则定义了初级听觉皮质中环境亚阈值活动受注意力和听觉刺激流物理特性调节的方式。我们的第二个具体目标是确定与注意相关的变化在初级和高级听皮层带状区域之间的功能连接中的机制和作用。我们的第三个具体目标是通过分析听觉丘脑和初级皮质区域的同时电生理活动，并使用电微刺激来识别启动和调节振荡PHSE重置的丘脑结构。在听觉丘脑皮质处理层次结构的不同节点上应用配对记录将提供有关动态大脑网络如何工作并受注意力调制的基本信息。这将允许对听觉感知和与注意力相关的缺陷进行直接的机械性解释，这些缺陷是许多衰弱的神经精神障碍的标志症状。

DESCRIPTION (provided by applicant): The brain must filter the overwhelming influx of sensory information to select information that is relevant to its current goals, in order to appropriately guide adaptive behavior. While studies in macaque monkeys have identified many of the mechanisms underlying attention effects on visual processing, very few studies have examined corresponding effects in the auditory system. Recent findings raise our overarching hypothesis that attention enhances the sensory representation of attended stimuli at the expense of ignored ones both by modulating local excitability within, and the dynamic routing of information across distinct functional areas in the brain. The broad goal of the proposed research is to examine this hypothesis and thus define the mechanisms of these interrelated local and network based processes, as well as their relative contributions to attentive auditory stimulus processing in different nodes of the auditory processing hierarchy. According to our hypothesis, attention modulates ongoing oscillatory activity to match its properties (frequency and phase) to the global acoustic features of the attended stimulus stream (temporal structure and pitch respectively), thereby creating an internal model of that stream in the form of subthreshold neuronal oscillations. This allows the oscillations to act as a template-based filter mechanism that segregates the relevant stream and enhances its processing along fundamental organizing dimensions of auditory objects. Parallel to this, the alignment of oscillatory activity across hierarchical processing stages biases the transmission of relevant information by providing a common temporal reference frame for communication that is tied to the temporal structure of the attended auditory stream. A key to both local enhancement and network based communication effects is the alignment of oscillatory phase to the timing of relevant events by oscillatory phase reset. Converging evidence suggests that phase reset is initiated by direct non-lemniscal thalamocortical afferents, and is modulated by top-down attention via the reticular nucleus of the thalamus. Our first specific aim is to determine the set of rules that define the way ambient subthreshold activity in primary auditory cortex is modulated by attention and by the physical properties of auditory stimulus streams. Our second specific aim is to define the mechanism and determine the role of attention related changes in functional connectivity between primary and higher level belt regions of auditory cortex. Our third specific aim is to identify the thalamic structures that initiate and modulate oscillatory phse reset by analyzing the concurrent electrophysiological activity of auditory thalamic and primary cortical regions, and using electrical microstimulation. The application of paired recordings across different nodes of the auditory thalamocortical processing hierarchy will provide fundamental information on how dynamic brain networks function, and are modulated by attention. This will allow for a direct mechanistic interpretation of auditory perceptual and attention related deficits, which are hallmark symptoms of many debilitating neuropsychiatric disorders.