Neuronal Measures of the State of Visual Attention

描述（由申请人提供）：几乎所有关于注意力基础的神经元机制的研究都比较了当受试者被要求注意不同的物体、位置或特征时的平均大脑活动。这种方法隐含的假设是，当受试者遵循给定的指令时，他们的注意力状态保持相对恒定。然而，任何执行过需要注意力的任务的人都知道，注意力会迅速而广泛地漂移。实验者可以精确地指定注意条件，但在给定的实验试验中对被试的实际注意状态的影响是有限的和间接的。这是一个重要的限制，因为注意力的波动可以系统地影响对注意力如何影响神经元活动和行为能力的估计。评估一个对象在特定时刻的实际注意力状态并不容易完成。然而，在最近的实验中，我们发现，对同时记录在大脑视觉皮层的单个神经元群体的信号进行适当的分析，可以提供当前注意力状态的精确测量。这些测量结果证实，即使指令、刺激和奖励是固定的，注意力也会大幅波动。此外，他们还发现，在固定的实验情境中，这些注意力的波动与行为表现的深刻差异有关。在个体试验中测量注意力状态的能力为探索注意力如何影响感官信号和行为表现提供了有力的工具。我们提出的实验将利用这种新方法来探索有关视觉注意的神经元基础的问题，这些问题以前是无法接近的。我们的第一个具体目标是使用来自不同群体的单个V4神经元的同时记录来确定不同视网膜置换表征下的注意力控制是协调的还是独立的。我们的第二个具体目标涉及类似的实验，这将提供直接测量神经元对空间和特征注意力的控制是否耦合。最后一个具体目标是在试验中测量注意力状态作为时间的函数，以比较刺激反应的动态与外源性或内源性线索引起的注意力转移以及注意转移的行为后果。总的来说，这些实验将为将注意力分配给不同视觉刺激的机制以及它们引起的神经元调节如何改善行为表现提供新的见解。

DESCRIPTION (provided by applicant): Virtually all studies of the neuronal mechanisms that underlie attention compare average brain activity when subjects are asked to attend to different objects, locations or features. Implicit in this approach is the assumption that a subject's state of attention remains relatively constant when they follow a given instruction. Yet anyone who has performed an attention-demanding task knows that attention can drift rapidly and widely. Experimenters can specify attentional conditions precisely, but have limited and indirect influence on a subject's actual attentional state on a given experimental trial. This is an important limitation, because fluctuations in attention can systematically affect estimates of how attention influences neuronal activity and behavioral ability. Assessing the actual attentional state of a subject at a given moment has not been easy to accomplish. However, in recent experiments we have discovered that appropriate analysis of the signals from populations of individual neurons recorded simultaneously in visual cerebral cortex can provide a precise measure of current attentional state. These measurements confirm that attention fluctuates widely even when instructions, stimuli and rewards are fixed. Moreover, they reveal that these fluctuations in attention are associated with profound differences in behavioral performance within fixed experimental situations. The ability to measure attentional state within individual trials provides a powerful tool for exploring how attention affects sensory signals and behavioral performance. We propose experiments that will exploit this novel method to explore questions about the neuronal basis of visual attention that have previously been inaccessible. Our first specific aim is to use simultaneous recordings from different populations of individual V4 neurons to determine whether the control of attention at different retinotopic representations is coordinated or independent. Our second specific aim involves analogous experiments that will provide direct measurements of whether neuronal control of spatial and feature attention is coupled. The final specific aim is to measure attentional state as a function of time within trials to compare the dynamics of stimulus responses with those of attentional shifts produced by exogenous or endogenous cues and those of the behavioral consequences of the attention shifts. Collectively, these experiments will provide new insights into the mechanisms that allocate attention to different visual stimuli and how the neuronal modulations they cause improve behavioral performance.