青老年组不同难度下心算活动的脑功能磁共振成像研究

应用功能磁共振成像技术研究不同心算难度下脑区的活动以及年龄的影响。14名志愿者（20～29岁青年和60～69岁老年被试各7名）参加了该实验。实验任务为2个难度水平的连续减法心算，分别为1000—3和1000—17。结果表明：（1）心算加工激活了额叶和顶叶的许多脑区；（2）大脑左半球是心算加工的优势半球，但随着心算难度加大，大脑一侧化程度下降，而年老加剧了这一趋势；（3）青年组进行简单心算（1000—3）时，额中回未见明显激活，而老年组进行简单心算时，该脑区被明显激活。总体上，额叶和顶叶在心算活动中起着重要作用，而任务难度和年龄对心算加工时脑活动的影响以额中回区最为明显。

The Neural Correlates of Mental Calculation: An fMRI Study on the Effects of Aging and Task Difficulty

Functional magnetic resonance imaging (fMRI) was used to investigate the effects of aging and task difficulty on brain activation engaged in mental calculation. Seven young and seven old volunteers performed two tasks during MRI scanning. In one task, the subjects were instructed to continually subtract three from 1000, and in the more difficult task, to continually subtract 17 from 1000. A large set of regions in the frontal and parietal cortices was activated during mental calculation. Although there was greater activation in the left hemisphere than in the right hemisphere, there was more involvement of the right hemisphere with increased arithmetic difficulty and age. In the 1000-3 task, activation in the medial prefrontal gyrus (MPFG) was observed only in the old group. These results suggest that both frontal and parietal lobes play important roles in mental calculation, and the involvement of these regions, particularly MPFG, is influenced by arithmetic difficulty and aging.