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PLoS Biology:北京大学罗欢研究组揭示多物体选择性注意的动态神经机制

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摘要 : 2017年6月28日,国际著名学术杂志《PLoS Biology》上在线发表了北京大学心理与认知科学学院、麦戈文脑科学研究所罗欢课题组发表题为“Sequential sampling of visual object during sustained attention”研究论文。

2017年6月28日,国际著名学术杂志《PLOS BioLogy》上在线发表了北京大学心理与认知科学学院、麦戈文脑科学研究所罗欢课题组发表题为“Sequential sampling of visual object during sustained attention”研究论文。论文阐述了多物体选择性注意的动态神经机制,发现注意过程是通过对时间组块进行灵活分配来对视觉场景中的多个物体进行采样和处理。第一作者是生命科学联合中心博士生贾建荣,论文通讯作者是罗欢研究员。

研究采用脑电图结合认知行为实验发现了视觉注意对多个物体的序列采样机制。视觉系统在每时每刻都会收到大量信息,注意过程需要选择重要的信息来进行优化加工(“选择性注意”)。以往大量研究都集中在对一个物体的选择性注意方面(注意一个而抑制其他)。然而,自然视觉场景往往包含多个物体,大脑是如何在时间空间上灵活的分配注意资源来达到对多个物体的采样呢?

本研究中,罗欢课题组采用了视觉注意范式结合时间响应函数(temporal response function) 的方法从人类大脑的整体脑电活动中分离出多个物体各自的神经响应活动(图1)。实验发现即使当前任务只要求注意一个视觉物体时,注意采样却仍然以大约200-300 毫秒的节奏在两个物体间进行切换,即反映出一种序列加工模式;这一序列加工过程是通过对alpha频段(~10 Hz)的神经活动进行时空上的调控来实现的;这种序列加工模式会随当前任务所要求的注意分配而进行相应改变,当任务要求在多个物体上的注意分配更均匀时,序列采样模式变得更为明显。

这些结果,结合罗欢课题组以往的“行为振荡”发现 (Song et al., 2014; Huang et al., 2015), 支持了注意的动态性和离散性,提示了注意过程可能是由一系列基本的注意时间组块(attentional temporal chunks)联结而成,各个物体的加工被分配在不同的注意时间组块中(图2),同时当前的任务也会对组块的资源分配进行灵活调控。这一成果揭示了多物体注意的动态新机制,开辟了新的基础研究方向,也对注意障碍相关的疾病有所启示。

PLoS Biology:北京大学罗欢研究组揭示多物体选择性注意的动态神经机制
图1 视觉注意范式结合时间响应函数来分离多物体各自的神经响应活动

PLoS Biology:北京大学罗欢研究组揭示多物体选择性注意的动态神经机制
图2 结果总结&注意时间组块概念示意

原文链接:

Sequential sampling of visual objects during sustained attention

原文摘要:

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.

doi:10.1371/journal.pbio.2001903

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