A Study On The Brain Areas Activated By Chinese And English Writing With Functional Magnetic Resonance Image Technique

Writing is one of the most important tools of communication and is a uniquely human skill. Much of our knowledge of the functional neuroanatomy associated with writing has been derived from lesion studies, especially studies of pure agraphia, which is a clinically important disease. Ogle proposed the concept of agraphia firstly in 1867, which was caused by impai.rment of the ability to write in the absence of abnormalities in language modalities in his opinion rather than by impairment of the primary motor function, the mechanical writing disturbance. Exner firstly proposed "writing center" in 1881, and located the center in the posterior part of the left middle frontal gyrus, the Exner's area, although this idea was not accepted popularly.With the development of modern technology, the neuroimaging (CT, fMRI, SPECT, rCBF, PET-CT) and especial functional imaging was applied in clinical performance, and provided suitable conditions for studies of brain areas related to the linguistic function. Not only morphological changes but also functional variations in some brain regions were reflected through these apparatus, which offered a strong technique method to further investigate the pathophysiological mechanisms of disturbance in linguistic function, such as alexia and agraphia. People got more knowledge about substrates of linguistic function from then on. People investigated writing from the clinical data that patients suffered from agraphia caused by impairments of some involved brain regions at present. The studies on agraphia in Chinese were initiated in the 80s in our country. In the past, people observed the clinical agraphia only individually or in a small group non-systemically so that the superficial knowledge was obtained. People investigated agraphia in Chinese systemically and deeply in 90s when a set of check method for agraphia in Chinese emerged, and was applied in clinical practice.Language processing in bilingual subjects was the focus of neuropsychological and liguistic studies. The events involved in neuroimaging included the studies of production and comprehension of language, and the studies of differences in linguistic elaborating induced by different linguistic element in bilingual subjects. There are controversial arguments about whether different linguistic elaborating activated different brain regions as well as what caused the differences.People know little about the analysis of brain functional areas involved in writing, especially in Chinese writing compared to other language processing in normal individuals. In order to investigate brain functional areas involved in writing and possible communications between the neural substrates, we elucidated the activated brain regions related to writing in Chinese and English using paradigms including writing with right and left hands tasks through functional magnetic resonance imaging (fMRI) so that we could provide strong evidence to guide the rehabilitation of agraphia patients clinically.We scaned eleven healthy volunteers (age 24-32) with blood-oxygen-level-dependence(BOLD) method through fMRI to observe activated areas under the conditions of spontaneous writing and copying in Chinese and English using paradigms including writing with right and left hands tasks. The data from fMRI was analyzed statistically using SPM2 software (Welcome Department of Cognitive Institute of Neurology, London, UK) , and contrasts were set to test for voxel-wise effects of signal difference between conditioned tasks and pseudo writings using t-test. Statistical parametric maps were calculated for each subject, and voxel-wise significance level was set at P＜0.01. Activated brain structures and the approximation of Brodmann's area (BA) were identified in reference to the standard brain atlas of Talairach and Tournoux with Talairach Space utility, and the mean activated sites among 11 subjects superimposed in the standard brain. Then we determined 4 patients impaired in frontal cortex accompanying agraphia for their oral and writing ability with ABC and CAB mental scale in order to identify non-linguistic cognitive handicap and to distinguish styles of linguistic disorder so that we can analyzed the characteristics of agraphia.From the above design of experiment, the following results were found. 1. the left middle frontal gyrus Brodmann's area 9 (BA9) is the only common activated area among the 8 groups designed in our experiments, regardless of writing in Chinese or English, writing with left or right hands, writing spontaneously or copying. 2. The left middle frontal gyrus BA9, 10, 11, 21, 22, and left middle temporal gyrus BA11, 22 were common activated areas either in spontaneous writing or in copying in Chinese groups, and it was suggested that these areas were essential brain regions in Chinese writing. 3. The left anterior central gyrus BA4, left middle frontal gyrus 9 and right middle temporal gyrus BA 22 were the common activated areas in Chinese copying with left and right hands. The inferior frontal gyrus BA 47 was activated in a mirror imaging manner in Chinese writing with left and right hands. 4. The left middle frontal gyrus BA 9, 10, 11 and right middle temporal gyrus BA 21 were commonly activated among spontaneous writing or copying in Chinese and English with right hands tasks. 5. The left middle frontal gyrus BA 9, 10, left posterior central gyrus BA 3 and right middle temporal gyrus BA 21 were the common activated areas in English spontaneous writing and copying with right hands tasks. 6. The left middle frontal gyrus BA 8, 9, 10, 11, Broca's convolution BA 45, right middle frontal gyrus BA 11 and right middle temporal gyrus BA 21 were the common activated areas in Chinese and English spontaneous writing groups with right hand. 7. The left middle frontal gyrus BA 9, 10, left inferior frontal gyrus BA44, left superior frontal gyrus BA 11 and right middle frontal gyrus BA 10, middle temporal gyrus BA 21 and inferior parietal lobule BA 40 as well as putamen in left striatum was activated commonly in Chinese and English copying tasks with right hand. 8. All of 4 patients with impairment in left frontal gyrus suffered from agraphia.From the above data, we got the following conclusions. 1. The left middle frontal gyrus BA 9 is the co-activated brain region regardless of writing in Chinese or English, writing with left or right hands etc, and it is an original information site probably. 2. Activated brain regions under the conditions of spontaneous writing and copying in Chinese and English using paradigms including writing with right and left hands tasks appeared to be dominant in left hemisphere, but the dominance of writing in Chinese was less than that of writing in English. 3. The brain areas related to writing distributed inequablely in central nervous system, and localized mainly in frontal lobes, parietal lobes, and emporal lobes etc. The different activated degrees in different regions could be corelated with their different significance in writing, and the higher degrees, the more central importance. 4. Putamens in left striatum were activated together either Chinese or English copying with right hands except for cerebral regions, and this suggested that the marginal division (MrD)of the striatum is probably one of subcortical areas related to writing. 5. It was suggested that the writing procedure was a complicated language processing, requiring to restore and extract linguistic informations through a access of neural substrates to memory dictionary, requiring transient memory for extracted informations through phono, morphous, and meaning, requiring execute control units for regulating subtle locomotor of hand so that a writing performance could be finished smoothly.