字母顺序及计数任务加工的事件相关电位研究

目的 运用事件相关电位(event-related potentials, ERP)探讨顺序及计数任务加工的脑机制.方法 16名大学生针对呈现的双字母和参考数字图片分别完成字母顺序判断任务和字母间距与参考数字比较的计数任务, 同时记录其19通道ERP.采用2(任务:顺序、计数)×3(字母间距:1、2、3)两因素重复测量析因设计,ERP分析结果利用F值和t值的统计参数映像呈现.结果 顺序任务的反应时间显著短于计数任务F (1, 15)=502.43,P =0.00],前者正确率显著低于后者F (1, 15)=52.96,P =0.00].计数任务行为绩效存在显著距离效应:三种字母间距的反应时间(1710.6±176.6)ms,(2133.2±201.3)ms,(2437.3±198.9)ms]和正确率分别随字母间距加大而延长或降低.ERP统计参数映像显示:顺序任务的右前额颞和左额颞活动(350～800 ms)增强;计数任务的额顶网络活动(200～300 ms)增强,右顶颞活动(860～890 ms)与字母间距线性关联.结论 顺序任务比计数任务执行更快但更易出错.前者ERP效应提示右侧半球提取和利用左侧半球存贮的字母顺序知识,反映了从记忆直接提取答案策略.后者的额顶ERP效应提示工作记忆机制的参与,右顶颞区ERP效应反映字母间距离效应和计数策略的应用.

The brain mechanism underlying alphabetical order and counting processing:an ERP research

Objective To investigate neural correlates of both order and counting processes in mental arithmetic. Methods The behavioral performance and ERP were recorded from 16 undergraduate while they were performing alphabetical order and counting tasks. A two-factor design of repeated-measure was adopted with the task (order, counting) and the distance between letters (1,2,3). The statistical parametric mapping (SPM) of both F-value and t-value was presented for ERP. Results The reaction time of the counting task was significantly slower than that of the order task and the correction rate of the former was higher than the latter ( P =0.00). Distance effects were observed for behavioral performance of the counting task. The spatiotemporal pattern of SPM suggested the right prefrontal and the left frontal-temporal regions (350～800 ms) were significantly activated under order task. The frontoparietal network (200～300 ms) was specially activated under the counting condition. The right parietal-temporal cortex at 860～890 ms showed the distance effect. Conclusion The significant activation in the right frontal and the left hemisphere under the order task suggests the functional role of the right hemisphere as retrieval and utilizing knowledge of alphabetical order, which stored in the left hemisphere. The frontoparietal network effect in the counting task suggests that the executive mechanism of working memory involved. The distance effect occurring in the left occipital and the right parietal-temporal at 860～890 ms might reflect the counting strategy and problem-size effect in mental arithmetic.