Cortical and thalamic mechanisms of selective auditory attention

描述（由申请人提供）：大脑必须过滤大量涌入的感官信息，以选择与当前目标相关的信息，以便适当地指导适应性行为。虽然对猕猴的研究已经确定了视觉处理中注意力影响的许多机制，但很少有研究检查了听觉系统中相应的影响。最近的研究结果提出了我们的首要假设，即注意力通过调节大脑内部的局部兴奋性和信息在不同功能区域之间的动态传递，以牺牲被忽视的刺激为代价，增强了对被关注刺激的感觉表征。本研究的总体目标是检验这一假设，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的不同节点上对注意听觉刺激加工的相对贡献。根据我们的假设，注意力调节正在进行的振荡活动，使其属性（频率和相位）与被参与刺激流的整体声学特征（分别为时间结构和音高）相匹配，从而以阈下神经元振荡的形式创建该流的内部模型。这允许振荡作为基于模板的过滤机制，隔离相关流并增强其沿听觉对象的基本组织维度的处理。与此平行的是，跨层次处理阶段的振荡活动的一致性，通过为与参与的听觉流的时间结构相关的交流提供一个共同的时间参考框架，从而使相关信息的传输产生偏差。局部增强和基于网络的通信效果的关键是通过振荡相位复位将振荡相位对准相关事件的定时。越来越多的证据表明，阶段重置是由直接的非丘脑皮层传入事件发起的，并通过丘脑网状核由自上而下的注意调节。我们的第一个具体目标是确定集合

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.