Analysis of neural mechanism related to working memory based on multi-dipole estimation with high temporal resolution.

有许多高阶认知过程的神经机制很难用非人类灵长类动物来研究。心理旋转任务是其中研究得最好的一个。基于高时间分辨率的多偶极子估计，通过测量两种心理旋转任务的脑磁图，研究了不同刺激下心理旋转背后的时空活动。在一个实验中，视觉刺激包括以不同方向呈现的手部形状；在另一个实验中，视觉刺激包括以不同方向呈现的一组字母字符及其镜像。所有刺激均呈现在左视野。与视觉刺激处理相关的活动在枕叶外侧、枕颞基底区和颞下回被估计。与高级视觉加工相关的活动在我们使用的两种刺激之间是不同的。在手型实验中，我们发现在刺激呈现后200-300 ms时，右顶叶下小叶活跃。对于字母字符，在大约300 ms时左颞上区有活动。此外，在顶叶下小叶和运动前区均观察到与精神刺激相关的活动。在手部实验中，运动前活动显示左半球占优势。然而，在字母字符实验中，运动前活动的偏侧性并未表现出左半球优势。我们推断这种差异受到受试者对视觉刺激的心理旋转熟悉程度的影响。

There are many higher-order cognitive processes whose neural mechanisms are hard to study by using nonhuman primates. The mental rotation task is one of the best studied of these. We investigated the spatio-temporal brain activity underlying mental rotation of different kinds of stimuli by measuring the magnetoencephalogram of subjects performing two kinds of mental rotation tasks, based on multi-dipole estimation with high temporal resolution. Visual stimuli in one experiment consisted of hand shapes presented at various orientations, and those in the other consisted of a set of alphabetic characters and their mirror images presented at various orientations. All stimuli were presented in the left visual field. Activity associated with visual stimulus processing was estimated in the lateral occipital lobe, basal occipito-temporal area, and inferior temporal gyrus. Activities related to higher visual processing were differed between the two kinds of stimuli we used. For the hand shapes experiment, we found right inferior parietal lobule activity at 200-300 ms after the stimulus presentation. For the alphabetic characters, activity was found in the left superior temporal region at about 300 ms. Furthermore, activity related to mental stimulation in the inferior parietal lobule and premotor area were seen in the both experiments. In the experiments with hands, the premotor activity showed left-hemispheric dominance. However, in the experiments with alphabetic characters, the laterality of the premotor activity did not show left-hemispheric dominance. We inferred this difference was influenced by the subjects 'familiarity with the mental rotation of visual stimuli.