加拿大不列颠哥伦比亚大学一项最新研究结果发现，人在走神时大脑的活动反而比科学家以前想象的更为活跃，研究结果刊登在最新一期美国《国家科学院院刊》（PNAS）上。这项研究发现，当我们心不在焉的时候，大脑很多区域的活动都有所增强事实上，该研究表明，一些同解决复杂问题有关的大脑区域在我们进行天马行空的想象时高度活跃，而科学家之前认为这些区域在我们走神时处于休眠状态。
领导实施这项研究的不列颠哥伦比亚大学心理学教授卡琳娜·克里斯托夫（Kalina Christoff）表示：“思绪飘扬一般同懒散或精力不集中等负面事情有关。但是，这项研究却表明我们走神时大脑活动反而更为活跃，活跃程度甚至超过我们专心从事一些日常工作的时候。”
在研究中，志愿者躺在fMRI扫描仪里面，当数字出现在屏幕上时进行按键等简单活动。研究人员可以通过大脑扫描、志愿者的主动报告以及追踪志愿者的成绩来调查他们的瞬间注意力。研究结果发现，走神(最多可以占据我们清醒状态下三分之一的时间)是一种重要的认知状态，在这种状态下，我们可能在不知不觉中将注意力从当前的工作转向梳理日常生活中的重要问题。
在此之前，科学家认为大脑的“默认网络”是走神时大脑中唯一活跃的区域。大脑“默认网络”同日常轻松的智力活动有关，包括内侧前额叶皮质、后扣带回皮质和颞顶联合区(temporoparietal junction)。但是，这项研究却发现，大脑的“执行网络”在我们走神时也会被激活。大脑“执行网络”负责解决高度复杂的问题，由侧面前额叶皮质和背面后扣带回皮质构成。
克里斯托夫说：“这是一项惊人发现，两个大脑网络可以被同时激活。在此之前，科学家一直认为它们在一个被激活时，另一个处于休眠状态。”志愿者越意识不到他们的思绪飘荡，两个大脑网络越能被激活。
大脑活动的数量和质量表明，尝试解决复杂问题的人应该先停下来，转而从事更为简单的工作，让思绪自由飘荡。克里斯托夫说：“你在走神的时候，可能并没有取得直接目标——比如在课堂上读书或集中注意力听讲，但思绪可能利用这一时间去解决你人生中更为重要的问题，比如事业发展或个人关系。”
PNAS May 11, 2009, doi: 10.1073/pnas.0900234106
Experience sampling during fMRI reveals default network and executive system contributions to mind wandering
Kalina Christoffa,1, Alan M. Gordonb, Jonathan Smallwoodc, Rachelle Smitha and Jonathan W. Schoolerc
Although mind wandering occupies a large proportion of our waking life, its neural basis and relation to ongoing behavior remain controversial. We report an fMRI study that used experience sampling to provide an online measure of mind wandering during a concurrent task. Analyses focused on the interval of time immediately preceding experience sampling probes demonstrate activation of default network regions during mind wandering, a finding consistent with theoretical accounts of default network functions. Activation in medial prefrontal default network regions was observed both in association with subjective self-reports of mind wandering and an independent behavioral measure (performance errors on the concurrent task). In addition to default network activation, mind wandering was associated with executive network recruitment, a finding predicted by behavioral theories of off-task thought and its relation to executive resources. Finally, neural recruitment in both default and executive network regions was strongest when subjects were unaware of their own mind wandering, suggesting that mind wandering is most pronounced when it lacks meta-awareness. The observed parallel recruitment of executive and default network regions—two brain systems that so far have been assumed to work in opposition—suggests that mind wandering may evoke a unique mental state that may allow otherwise opposing networks to work in cooperation. The ability of this study to reveal a number of crucial aspects of the neural recruitment associated with mind wandering underscores the value of combining subjective self-reports with online measures of brain function for advancing our understanding of the neurophenomenology of subjective experience.
（译文及原文源自不知哪里。）
