Kucyi Aaron, Davis Karen D
Division of Brain, Imaging and Behaviour - Systems Neuroscience, Toronto Western Research Institute, University Health Network, Toronto, ON, Canada; Institute of Medical Science, University of Toronto, Toronto, ON, Canada.
Division of Brain, Imaging and Behaviour - Systems Neuroscience, Toronto Western Research Institute, University Health Network, Toronto, ON, Canada; Institute of Medical Science, University of Toronto, Toronto, ON, Canada; Division of Neurosurgery, Toronto Western Hospital, Toronto, ON, Canada; Department of Surgery, University Health Network, Toronto, ON, Canada.
Neuroimage. 2014 Oct 15;100:471-80. doi: 10.1016/j.neuroimage.2014.06.044. Epub 2014 Jun 25.
Humans spend much of their time engaged in stimulus-independent thoughts, colloquially known as "daydreaming" or "mind-wandering." A fundamental question concerns how awake, spontaneous brain activity represents the ongoing cognition of daydreaming versus unconscious processes characterized as "intrinsic." Since daydreaming involves brief cognitive events that spontaneously fluctuate, we tested the hypothesis that the dynamics of brain network functional connectivity (FC) are linked with daydreaming. We determined the general tendency to daydream in healthy adults based on a daydreaming frequency scale (DDF). Subjects then underwent both resting state functional magnetic resonance imaging (rs-fMRI) and fMRI during sensory stimulation with intermittent thought probes to determine the occurrences of mind-wandering events. Brain regions within the default mode network (DMN), purported to be involved in daydreaming, were assessed for 1) static FC across the entire fMRI scans, and 2) dynamic FC based on FC variability (FCV) across 30s progressively sliding windows of 2s increments within each scan. We found that during both resting and sensory stimulation states, individual differences in DDF were negatively correlated with static FC between the posterior cingulate cortex and a ventral DMN subsystem involved in future-oriented thought. Dynamic FC analysis revealed that DDF was positively correlated with FCV within the same DMN subsystem in the resting state but not during stimulation. However, dynamic but not static FC, in this subsystem, was positively correlated with an individual's degree of self-reported mind-wandering during sensory stimulation. These findings identify temporal aspects of spontaneous DMN activity that reflect conscious and unconscious processes.
人类大部分时间都在进行与刺激无关的思考，通俗地说就是“白日梦”或“思绪游走”。一个基本问题是，清醒时的自发脑活动如何体现白日梦这种持续认知与被称为“内在”的无意识过程。由于白日梦涉及自发波动的短暂认知事件，我们测试了脑网络功能连接（FC）动态与白日梦相关的假设。我们根据白日梦频率量表（DDF）确定了健康成年人白日梦的总体倾向。然后，受试者在静息状态功能磁共振成像（rs-fMRI）以及感觉刺激期间接受fMRI检查，同时伴有间歇性思维探测，以确定思绪游走事件的发生情况。对默认模式网络（DMN）中据称与白日梦有关的脑区进行了评估，包括：1）整个fMRI扫描过程中的静态FC；2）基于每次扫描中以2秒递增的30秒渐进滑动窗口内的FC变异性（FCV）的动态FC。我们发现，在静息和感觉刺激状态下，DDF的个体差异与后扣带回皮质和参与前瞻性思维的腹侧DMN子系统之间的静态FC呈负相关。动态FC分析显示，DDF在静息状态下与同一DMN子系统内的FCV呈正相关，而在刺激期间则不然。然而，在感觉刺激期间，该子系统中动态而非静态的FC与个体自我报告的思绪游走程度呈正相关。这些发现确定了反映有意识和无意识过程的自发DMN活动的时间特征。
