The Role Of The Basal Ganglia In Chinese Writing

BackgroundThe basal ganglia (BG) belong to nuclei of gray matter deep within the cerebral hemispheres, which include the caudate nucleus, the putamen, the dorsal thalamus and the globus pallidus. During the evolution of species, the BG is turning from a motor control center in Aves to a structure being subject to the motor cortex in mammal, especially in primate. Recently, some studies revealed the BG in human is not only under control in the motor cortex, but also is a structure involving in many cognitive capacities, such as language, plan, execution function.While the role of cortical areas in linguistic processing is relatively well established, the role of the BG and the way they impact language processing are still controversial. Neurologists found that some diseases related to the BG damage, such as Parkinson's disease (PD), Huntington's disease (HD), Wilson's disease (WD), the basal ganglia with vascular damage and corticobasal degeneration are manifested with various kinds of language disorders. And studies by neurolinguists using patients sustaining BG damage have suggested the BG is involved in various aspects of language comprising phonology and syntax.Writing, which is implemented by limbs or tools, is one kind of language process. It not only needs competence of language processing but also needs help of visual, auditory, visual space, motor and so on. English, belongings to alphabetic writing systems, is a main material in former study, whereas, Chinese characters, belongings to logographic writing systems, are often semantic-phonetic compounds, symbols which include an element that represents the meaning and element that represents the pronunciation. As each character represents a single word, Chinese writing is more complex than English. The difference between the two languages is from the structure of word to figure-sound relation and figure-meaning relation. So it is necessary to study the process of Chinese writing.Most of the subjects of language study with the BG damage are PD and HD. Whether the writing process of WD with the BG damage is the same as PD and HD? Few studies on WD were done, especially in Chinese characters. The present study proposed that WD with the BG damage influences the process of Chinese writing through the analysis of the Chinese agraphia battery (CAB) and a functional neuroimaging examination of PET-CT. The present study is to analyze roles of the BG in Chinese writing and to explore its neuropsychological mechanism, by investigating features of agaphia of WD with the BG damage and the data of functional imaging of Chinese writing.ObjectThe present study is to investigate features of agaphia of WD with the BG damage, to investigate the data of functional imaging of Chinese writing, to analyze roles of the BG in Chinese writing and to explore its neuropsychological mechanism.MaterialWe studied sixty patients with WD with brain damage and seven male patients joined the study of functional imaging. All patients were Chinese speaking, 23.68±7.23 years old, educated in 9.57±2.75 years and both right handedness, included forty four male and sixteen female. All patients accepted treatment above six months (dietary therapy, penicillamine, zinc). Only individuals with no history of psychiatric or neurological disease other than WD, as well as no agnosia, apraxia, neglect, depression and anxiety, no history of alcohol or drug abuse were included. Methods1. The Chinese agraphia battery (CAB) was used to identify agraphia in sixty patients with WD. According to agraphia quotient (AgQ) scores, all patients were divided into normal writing group and agraphia group and their types of agraphia were identified. Data were analyzed with statistical package for social sciences 13.0 (SPSS13.0).2. Seven male patients were divided into two groups through language evaluation which were normal writing group and agraphia group. They were scanned by positron emission tomography (PET) respectively while performing two tasks: 1) pseudo-writing, 2) Chinese character writing (ie. names, color, animals). Data were analyzed with Statistical Parametric Mapping 2 (SPM2) for "Chinese character writing versus pseudo writing".Results1. Agraphia was identified in thirty-six cases (60%) and the patients had difficulty in positive writing, writing by picture, dictation, automatic writing and copying (in descending order of severity).2. Language agraphia and non-language agraphia were detected in twenty-five cases (41.7%) and fifteen (25%) respectively, and some cases were detected with both kinds of agraphia.3. Among patients with language agraphia, twenty cases have character formation disorder, eleven cases, wrong-writing characters and three cases, grammar disorder. Among patients with non-language agraphia, eight cases have micrographia, seven cases, tremor agraphia and two cases, reiterative agraphia.4. Compared with pseudo-writing, patients in normal writing group showed greater activation of the bilateral lateral globus pallidus and the right putamen, whereas patients in agraphia group showed greater activation of the right ventral lateral nucleus, the claustrum, the left putamen and the lateral globus pallidus. Conclusions1. Agraphia is a common symptom in Wilson's disease with brain damage. Language agraphia is more common than non-language agraphia, especially character formation disorder.2. Chinese writing of patients with Wilson' disease involve in the bilateral subcortical structure. The right basal ganglia plays more important role.3. Activated areas in the bilateral basal ganglia of patients with agraphia are different with patients with normal writing. The right thalamus plays a compensatory role when patients with agraphia are writing.