Unit for Experimental Psychiatry, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104, USA.
Neuroimage. 2010 Feb 15;49(4):3426-35. doi: 10.1016/j.neuroimage.2009.11.020. Epub 2009 Nov 24.
During sustained periods of a taxing cognitive workload, humans typically display time-on-task (TOT) effects, in which performance gets steadily worse over the period of task engagement. Arterial spin labeling (ASL) perfusion functional magnetic resonance imaging (fMRI) was used in this study to investigate the neural correlates of TOT effects in a group of 15 subjects as they performed a 20-min continuous psychomotor vigilance test (PVT). Subjects displayed significant TOT effects, as seen in progressively slower reaction times and significantly increased mental fatigue ratings after the task. Perfusion data showed that the PVT activates a right lateralized fronto-parietal attentional network in addition to the basal ganglia and sensorimotor cortices. The fronto-parietal network was less active during post-task rest compared to pre-task rest, and regional CBF decrease in this network correlated with performance decline. These results demonstrate the persistent effects of cognitive fatigue in the fronto-parietal network after a period of heavy mental work and indicate the critical role of this attentional network in mediating TOT effects. Furthermore, resting regional CBF in the thalamus and right middle frontal gyrus prior to task onset was predictive of subjects' subsequent performance decline, suggesting that resting CBF quantified by ASL perfusion fMRI may be a useful indicator of performance potential and a marker of the level of fatigue in the neural attentional system.
在持续的高认知负荷工作期间，人类通常会表现出时间作业（TOT）效应，即在任务参与期间，表现会逐渐恶化。在这项研究中，使用动脉自旋标记（ASL）灌注功能磁共振成像（fMRI）来研究 15 名受试者在进行 20 分钟连续精神运动警觉测试（PVT）时 TOT 效应的神经相关性。受试者表现出明显的 TOT 效应，表现在反应时间逐渐变慢，任务后精神疲劳评分显著增加。灌注数据显示，PVT 除了基底神经节和感觉运动皮层外，还激活了右侧额顶叶注意力网络。与任务前休息相比，任务后休息时额顶叶网络的活动减少，并且该网络中的局部 CBF 下降与表现下降相关。这些结果表明，在进行大量脑力工作后，认知疲劳在额顶叶网络中会持续存在，并表明该注意力网络在介导 TOT 效应中起着关键作用。此外，任务开始前丘脑和右额中回的静息局部 CBF 可预测受试者随后的表现下降，表明 ASL 灌注 fMRI 量化的静息 CBF 可能是表现潜力的有用指标，也是神经注意力系统中疲劳水平的标志物。
