Jansma J M, Ramsey N F, de Zwart J A, van Gelderen P, Duyn J H
Laboratory of Functional and Molecular Imaging (LFMI), National Institutes of Health (NIH), National Institute of Neurological Disorders and Stroke (NINDS), Bethesda, Maryland 20892, USA.
Hum Brain Mapp. 2007 May;28(5):431-40. doi: 10.1002/hbm.20297.
It is unclear how effort translates into brain function. In this study we endeavored to identify the activity in a working memory task that is related to the allocation of mental resources. Such activity, if present, would be a likely candidate to explain how effort works in terms of brain function. Eleven healthy participants performed a Sternberg task with a memory-set of one, three, or five consonants in an fMRI study. Probe stimuli were either one consonant or one digit. We expected digits to be processed automatically and consonants to require working memory. Because the probe type was unpredictable and subjects had to respond as fast as possible, we expected subjects to allocate mental resources on the basis of the memory-set size, not the probe type. Accordingly, we anticipated that activity in regions involved in effort would be a function of the size of the memory-set, but independent of the type of probe. We found that the reaction-time for digits increased in line with our expectation of automatic processing and the reaction time for letters increased in line with our expectation of controlled processing. fMRI revealed that activity in the right ventral-prefrontal cortex changed as a function of effort. The ventral anterior cingulate cortex and hypothalamus showed reduced activity as a function of effort. Activity in regions regarded as pivotal for working memory (among others, the left dorsolateral prefrontal cortex, anterior cingulate cortex) appeared to be predominantly related to information processing and not involved in effort.
目前尚不清楚努力是如何转化为大脑功能的。在本研究中，我们致力于确定一项工作记忆任务中的活动，该活动与心理资源的分配有关。如果存在这样的活动，它很可能是解释努力在大脑功能方面如何起作用的一个候选因素。在一项功能磁共振成像（fMRI）研究中，11名健康参与者执行了一项斯特恩伯格任务，记忆集包含1个、3个或5个辅音。探测刺激要么是1个辅音，要么是1个数字。我们预计数字会被自动处理，而辅音则需要工作记忆。由于探测类型不可预测，且受试者必须尽快做出反应，我们预计受试者会根据记忆集的大小而非探测类型来分配心理资源。因此，我们预计参与努力的区域中的活动将是记忆集大小的函数，但与探测类型无关。我们发现，数字的反应时间按照我们对自动处理的预期增加，而字母的反应时间按照我们对受控处理的预期增加。功能磁共振成像显示，右侧腹侧前额叶皮层的活动随努力程度而变化。腹侧前扣带回皮层和下丘脑的活动随努力程度而减少。被认为对工作记忆至关重要的区域（包括左侧背外侧前额叶皮层、前扣带回皮层等）的活动似乎主要与信息处理有关，而与努力无关。
