Many experimental results have been found in previous studies on whether laterality of brain cingulate gyrus exists in processing Chinese words information.OBJECTIVE:
To observe the function of right anterior cingulate gyrus and activation showed by MRI in processing Chinese words in a visual working memory judgment tasks, and evaluate the laterality of activated brain regions.DESIGN:
The Medical Psychological Research Center, Second Xiangya Hospital of Central South University.PARTICIPANTS:
Thirteen healthy volunteers (7 males and 6 females), aged (29±7) years ranging from 23 to 36 years old, participated in this fMRI study during August 2003 to Febuary 2004. They gave informed consent in accordance with guidelines set by Second Xiangya Hospital of Central South University. All subjects were native Chinese speakers and strongly right handed.METHODS:
In this study, Chinese numeral words were used as test materials and test mode of Sternberg was used in cognitive task, it was aimed to investigate the encephalic region involved in the storage and processing of Chinese numerical information. ①The head of subject was fixed with dense foam pad. Visual working task was performed according to the requests. Verbal working task was that the subject saw target items for four numerals written in Chinese, presenting for 1.5 s and then, after a short time by blank for 3.0 s. The subject saw one numeral presenting for 1.5 s and had to press one button if it was one of the shown numbers and another button if it did not belong to the presented numbers. There were two visual working memory stimuli in each stimulation block. The experiment was conducted in a single run, which consisted of seven blocks of visual working memory tasks. Different Chinese numerals were displayed in each block to avoid any practice effect (The response rate of the whole working memory task was 50%). ②The activation of brain was scanned with a 1.5T MRI scanner (GE Signa Twinspeed) (slice thickness 5 mm, slice gap 1.5 mm, slice parallel to line between pars geniculate and splenium in corpus callosum from corona capitis to superior part of cerebellum, totally 16 to 18 layers). ③The obtained images were pre-processed and statistically analysed with SPM 99 software. The procedure included timeslice adjusted, realigned, nomalized and smoothed. According to experimental task, data from each subject were analysed to obtain t value of each voxel. Brain activation image was got by Student's t test and statistic was presented by pseudo-color. Statistical parameter image was formed by overlapping brain activation image on three-dimensional structure image, and the threshold value was set at P < 0.05 with ten or more continous voxels (T ≥ 4.64, K ≥ 10 voxels). The brain activation images of all the subjects were calculated and overlapped into mean brain activation images. The regions with different activation density were found out. The activation voxels in regions-of-interest were checked to calculate a laterality index for each condition. The negative value indicated right hemisphere dominance.MAIN OUTCOME MEASURES:
fMRI activation and laterality coefficient of Chinese numerial working task.RESULTS:
Thirteen healthy subjects participated in the result analysis. ①fMRI activation of Chinese numerial working task: The results showed that the working memory task with Chinese words not only activated left cerebral cortex including left superior frontal gyrus (BA6/10), left middle frontal gyrus (BA9), left inferior frontal gyrus (BA45/9/47), but also activated right cerebral cortex including right middle frontal gyrus (BA10/46/8), right inferior frontal lobe (BA47). Specially, peak activation was located in right anterior cingulate gyrus (BA32) with an activation volume of 879 (voxels). It indicated that superior, middle and inferior frontal gyrus, bilateral Broca regions and anterior cingutate involved in the working memory of Chinese words. ② Asymmertry index : The asymmetry index was -0.47 for frontal lobe, +0.42 for temporal lobe, +0.14 for parietal lobe and -1.00 for occipital lobe. It indicated that the right frontal lobe, left temporal lobe, left parietal lobe and right occipital lobe were more involved in the Chinese numerial working task.CONCLUSION:
Brain activation in processing Chinese words in the visual working memory task broadly involves both the left and right hemisphere cortex. And right anterior cingulate gyrus (BA 32) plays an important role in integrating and processing intensive visuospatial ability.