Neuronal mechanisms of attentional selection in primary auditory cortex

描述（由申请人提供）：选择性注意通过增强任务相关刺激的神经表征，以牺牲无关刺激为代价，使感觉处理适应观察者的直接目标。先前对人类和猴子的研究表明，注意力调节视网膜之后视觉处理的每个阶段的神经元反应。虽然听觉选择性注意已经在人类中得到了广泛的研究，但对猴子的研究几乎没有触及到这个话题。本R21提案的主要目标是通过直接电生理记录猴子初级听觉皮层（A1）的选择性注意的神经机制的研究。越来越多的证据表明，神经元振荡反映了神经元群中兴奋性在不同空间和时间尺度上有组织的节律性转移，这些振荡是正常大脑功能的基本组成部分，在感觉、认知和运动操作中起着至关重要的作用。特别是，最近对视觉皮层的研究表明，正在进行的振荡活动的结构可以适应或“携带”一个参与的感觉刺激流的时间（节奏）结构。牵带使神经元振荡的高兴奋性阶段与参与流中事件的时间一致，从而放大了它们的神经元表征。由于节奏结构对许多具有生物学意义的声音刺激（如语音）至关重要，振荡干扰作为听觉系统中注意选择的一种机制将显得特别有用。这一命题有很强的心理物理学支持，但尚未在神经生理学水平上得到直接检验。我们将评估整个假设，即神经元振荡的参与声流的时间结构导致神经元对构成该流的事件的反应增强，并抑制神经元对沿着听觉处理的两个基本组织维度，时间（节奏）和频率偏离该流的刺激的反应。行为测量，以及层流电流源密度和在任务执行期间在A1中采样的多单元活动剖面，将解决定义1)参与节奏和2)参与音调频率对听觉处理的影响的具体目标。由于神经元振荡的注意力牵引对复杂环境中有效的适应性行为至关重要，因此它的中断可能会导致认知障碍。定义注意力夹带的神经基础是理解认知功能和功能障碍机制的关键一步。

DESCRIPTION (provided by applicant): Selective attention adapts sensory processing to the immediate goals of an observer by enhancing the neural representation of task relevant stimuli at the expense of irrelevant stimuli. Prior studies in both humans and monkeys show that attention modulates neuronal responses at every stage of visual processing after the retina. While auditory selective attention has been extensively studied in humans the topic is almost untouched by studies in monkeys. The broad goal of this R21 proposal is to initiate studies of the neural mechanisms of selective attention by direct electrophysiological recording in primary auditory cortex (A1) of the monkey. Accumulating evidence indicates that neuronal oscillations reflect organized rhythmic shifting of excitability in neuronal ensembles on different spatial and temporal scales, and that these oscillations are fundamental components of normal brain function with a crucial role in sensory, cognitive and motor operations. In particular, recent studies in visual cortex reveal that the structure of ongoing oscillatory activity can adapt or "entrain" to the temporal (rhythmic) structure of an attended sensory stimulus stream. Entrainment aligns the high excitability phase of neuronal oscillations with the timing of events in the attended stream, thus amplifying their neuronal representation. As rhythmic structure is essential to many biologically significant acoustic stimuli (e.g., speech sounds), oscillatory entrainment would appear particularly useful as a mechanism of attentional selection in the auditory system. This proposition has strong psychophysical support, but has not been directly tested at a neurophysiological level. We will evaluate the overall hypothesis that the entrainment of neuronal oscillations to the temporal structure of an attended acoustic stream results in enhanced neuronal responses to events that comprise that stream, and suppressed neuronal responses to stimuli that deviate from it along the two fundamental organizing dimensions of auditory processing, time (rhythm) and frequency. Behavioral measures, along with laminar current source density and multiunit activity profiles sampled in A1 during task performance will address the specific aims of defining the effects of 1) attended rhythm, and 2) attended tone frequency on auditory processing. Since attentional entrainment of neuronal oscillations appears critical to efficient, adaptive behavior in a complex environment, its disruption would likely result in cognitive impairment. Defining the neural underpinnings of attention entrainment is a crucial step in understanding the mechanisms of cognitive function and dysfunction. PUBLIC HEALTH RELEVANCE: Attention entrainment of neuronal oscillations is believed to be crucial to the effective use of ongoing physiological processes in adaptive processing of complex natural stimuli, yet the rules that govern it and its function are still largely unknown. We propose to explore oscillatory entrainment as a mechanism of auditory selective attention. Since deficits of auditory processing are key symptoms in numerous neuropsychiatric disorders, our findings will have important implications for improved understanding and treatment of these disorders, and for advancing our understanding of dynamic brain operations in general.