Sequential sampling of visual objects during sustained attention.
Sequential sampling of visual objects during sustained attention.
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DOI：
10.1371/journal.pbio.2001903
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发表时间：
2017-06
期刊：
影响因子：
9.8
通讯作者：
Luo H
中科院分区：
文献类型：
--
作者：
Jia J;Liu L;Fang F;Luo H
在拥挤的视觉场景中，注意力必须高效和灵活地分布在时间和空间上，以适应不同的上下文。众所周知，选择性注意增强了相应的神经反应，这可能意味着注意力将持续停留在与任务相关的项目上。与此同时，最近的研究表明，注意力并不是保持静止的，而是随着时间的推移交替采样对象，这表明注意力是有节奏的。这些研究大多是在分裂的注意力环境中进行的。然而，目前尚不清楚这种动态机制是否在一般水平上本质上调节了注意过程。重要的是，也完全缺乏直接的神经证据来反映大脑在刺激处理过程中是否以及如何有节奏地对多个视觉对象进行采样。为了解决这些问题，在本研究中，我们使用了脑电(EEG)和时间反应函数(TRF)方法，该方法可以将仅代表单个对象的反应从整体神经元活动中分离出来，以考察不同注意背景下注意的时空特征。首先，注意力在TRF中以抑制α波段(约10赫兹)活动为特征，每隔大约200毫秒在有人和无人注意的物体之间切换，这意味着即使在需要注意力主要停留在有人注意的物体上时，也是顺序采样。其次，注意的时空模式受到任务情境的调节，因此当任务需要更均匀的注意力分布时，阿尔法中介的转换变得越来越突出。最后，转换模式与注意行为表现相关。我们的工作提供了直接的神经证据，支持时间组织机制在注意中的一般中心作用，从而使多个对象根据它们在注意上下文中的优先顺序进行排序。结果表明，选择性注意，除了经典假设的注意“焦点”之外，还包括一种动态机制，用于监控焦点之外的所有对象。我们的发现还表明，注意力通过一次对一个物体进行操作的一系列串联注意力块来实现空间(物体)到时间的转换。在拥挤的视觉场景中，注意力必须有效和灵活地分布在时间和空间上，以适应任务中的不同背景。最近的研究表明，注意是一个动态的过程，可以在时间上组织大量的信息。然而，大脑如何在多个视觉对象之间协调注意力，以及这种动态机制是否在一般水平上调节注意力，仍在很大程度上尚不清楚。在这项研究中，我们分析了多对象选择性注意任务中的脑电(EEG)记录，以提取对象特定的神经元反应。我们证明，每隔大约200毫秒，注意力就会有节奏地在视觉对象之间切换。此外，注意的时空采样轮廓会在不同的任务情境中自适应地变化，并与注意过程中的行为表现相关。我们的工作提供了直接的神经证据，支持多个对象根据它们在注意上下文中的优先顺序进行排序的想法。结果表明，注意力本质上是动态的，作为一系列串联的注意力块，一次对一个对象进行操作，以保持对整个场景的意识。
In a crowded visual scene, attention must be distributed efficiently and flexibly over time and space to accommodate different contexts. It is well established that selective attention enhances the corresponding neural responses, presumably implying that attention would persistently dwell on the task-relevant item. Meanwhile, recent studies, mostly in divided attentional contexts, suggest that attention does not remain stationary but samples objects alternately over time, suggesting a rhythmic view of attention. However, it remains unknown whether the dynamic mechanism essentially mediates attentional processes at a general level. Importantly, there is also a complete lack of direct neural evidence reflecting whether and how the brain rhythmically samples multiple visual objects during stimulus processing. To address these issues, in this study, we employed electroencephalography (EEG) and a temporal response function (TRF) approach, which can dissociate responses that exclusively represent a single object from the overall neuronal activity, to examine the spatiotemporal characteristics of attention in various attentional contexts. First, attention, which is characterized by inhibitory alpha-band (approximately 10 Hz) activity in TRFs, switches between attended and unattended objects every approximately 200 ms, suggesting a sequential sampling even when attention is required to mostly stay on the attended object. Second, the attentional spatiotemporal pattern is modulated by the task context, such that alpha-mediated switching becomes increasingly prominent as the task requires a more uniform distribution of attention. Finally, the switching pattern correlates with attentional behavioral performance. Our work provides direct neural evidence supporting a generally central role of temporal organization mechanism in attention, such that multiple objects are sequentially sorted according to their priority in attentional contexts. The results suggest that selective attention, in addition to the classically posited attentional “focus,” involves a dynamic mechanism for monitoring all objects outside of the focus. Our findings also suggest that attention implements a space (object)-to-time transformation by acting as a series of concatenating attentional chunks that operate on 1 object at a time. In a crowded visual scene, attention must be efficiently and flexibly distributed over time and space to accommodate different contexts in a task. Recent studies have proposed that attention is a dynamic process that organizes copious information temporally. However, how the brain coordinates attention among multiple visual objects and whether this dynamic mechanism mediates attention at a general level remain largely unknown. In this study, we analyze electroencephalography (EEG) recordings during a multi-object selective attention task to extract object-specific neuronal responses. We demonstrate that attention rhythmically switches between visual objects every approximately 200 ms. Furthermore, the spatiotemporal sampling profile of attention adaptively changes in various task contexts and correlates with behavioral performance during attention. Our work provides direct neural evidence supporting the idea that multiple objects are sequentially sorted according to their priority in attentional contexts. The results suggest that attention is intrinsically dynamic, acting as a series of concatenating chunks of attention that operate on 1 object at a time to maintain awareness of the whole scene.