Klingberg T
Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
Cereb Cortex. 1998 Oct-Nov;8(7):593-601. doi: 10.1093/cercor/8.7.593.
When two tasks are performed simultaneously, performance often deteriorates, with concomitant increases in reaction time and error rate. Three potential neurophysiological mechanisms behind this deterioration in performance have been considered here: (i) dual-task performance requires additional cognitive operations and activation of cortical areas in addition to those active during single-task performance; (ii) two tasks interfere if they require activation of the same part of cortex; and (iii) cross-modal inhibition causes interference between two tasks involving stimuli from different sensory modalities. Positron emission tomography was used to measure regional cerebral blood flow (rCBF) during performance of an auditory working memory (WM) task, a visual WM task, both WM tasks (dual task) and a control condition. Compared to the control condition, the auditory and visual WM tasks activated sensory-specific areas in the superior temporal gyrus and occipital pole respectively. Both WM tasks also activated overlapping parts of cortex in the dorsolateral prefrontal, inferior parietal and cingulate cortex. There was no separate cortical area which was activated only in the dual task, and thus no area which could be associated with any dual task specific cognitive process such as task-coordination or divided attention. Decrease in rCBF in one WM task did not overlap with the areas of rCBF increase in the other WM task. However, an inhibitory mechanism could not be ruled out, since the rCBF increase in sensory specific areas was smaller in the dual-task condition than in the single-task conditions. The cortical activity underlying WM was to a large extent organized in a non-sensory specific, or non-parallel, way, and the results are consistent with the hypothesis that concurrent tasks interfere with each other if they demand activation of the same part of cortex.
当同时执行两项任务时，表现往往会变差，同时反应时间和错误率会增加。本文考虑了导致这种表现变差的三种潜在神经生理机制：（i）双任务执行除了需要单任务执行期间活跃的那些认知操作和皮质区域的激活外，还需要额外的认知操作和皮质区域的激活；（ii）如果两项任务需要激活皮质的同一部分，则它们会相互干扰；（iii）跨模态抑制会导致涉及来自不同感觉模态的刺激的两项任务之间的干扰。在执行听觉工作记忆（WM）任务、视觉WM任务、两项WM任务（双任务）和一种对照条件期间，使用正电子发射断层扫描来测量局部脑血流量（rCBF）。与对照条件相比，听觉和视觉WM任务分别激活了颞上回和枕极的感觉特异性区域。两项WM任务还激活了背外侧前额叶、顶下叶和扣带回皮质中重叠的皮质部分。没有仅在双任务中被激活的单独皮质区域，因此没有可以与任何双任务特定认知过程（如任务协调或分散注意力）相关联的区域。一项WM任务中rCBF的减少与另一项WM任务中rCBF增加的区域不重叠。然而，不能排除抑制机制，因为在双任务条件下感觉特异性区域中rCBF的增加小于单任务条件下的增加。WM背后的皮质活动在很大程度上是以非感觉特异性或非并行的方式组织的，并且结果与以下假设一致：如果并发任务需要激活皮质的同一部分，则它们会相互干扰。
