Dissertation
Dissertation > Medicine, health > Clinical > Diagnostics > Diagnostic Imaging > Magnetic resonance imaging

An fMRI Study of Encoding and Retrieval of Chinese Charaters and Object Pictures

Author WangHaiBao
Tutor YuYongQiang;WangKai
School Anhui Medical University,
Course Medical Imaging and Nuclear Medicine
Keywords Chinese characters fMRI episodic memory encoding retrieval neural network
CLC R445.2
Type Master's thesis
Year 2003
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Backgrounds and Objective Memory is an important function of human brain and made up of four types of processes: encoding, consolidation, storage and retrieval. With the variation of materials and levels of encoding/retrieval, there existed differences in mechanisms of neural network (NN) and the related functional regions of brain. At present, study of the brain function utilizing alphabetic languages such as English and Italian internationally, especially in research of memory, achieved an abundant fruit, and put forward a series of theoretical hypotheses. Tulving (1995) and Squire (1992) had suggested the model of multiple memory systems (MMS). Latterly Tulving , Kapur and their colleagues after reviewing a variety of the published investigations on neuroimaging, and found that in terms of episodic memory encoding and retrieval, the left prefrontal lobe is more responsible for encoding than the right, while the right prefrontal cortex is more involved in episodic memory retrieval. Therefore they had brought forward the hypotheses of the hemispheric encoding/retrieval asymmetry (HERA) model which mechanism is unknown yet and should be explored further. Chinese characters, referred as a kind of linguistic character, may be similar to other characters such as English, but there existed difference because the written Chinese as a basic writing unit has a square configuration, and more than 70 percent of which are hieroglyph and map into morphemes (meaning) rather than phonemes (minimalsound units) in the spoken language. Accordingly there may be some its owncharacters for the written Chinese episodic memory encoding and retrieval, however study in this field is rather less home and abroad at present . Inthis subject, on the basis of blood oxygenation-level dependent functional MRI (BOLD-fMRI), the examination was performed in normal volunteer to acquire the functional neuroanatomy mapping and study the mechanisms of episodic memory of the Chinese characters and object pictures, the mechanisms and the neurobiological basis of human memory encoding and retrieval were probed further. Another purpose is to provide an experimental paradigms of neuroimaging for clinical research and application as well. Materials and Methods 10 subjects (5males, Sfemales) involved in this study with an age range of 18-33 years (mean, 23years). They were all healthy, young, right-handed with normal vision. Two kinds of materials were used as follows: 66 high frequency Chinese characters (double-character concrete real-semantic nouns) and 66 object pictures. Trials were divided into two groups: stimulative group, and control group, and experimental processing consisted of two stages: encoding (living/no living judgment) and retrieval (old/new recognition). In the magnetic field, subjects were instructed to finish tasks according to requirement, and fMRI was performed to scan throughout brain simultaneously. High speed BOLD-EPI sequence was adopted, and the founctional imaging was made up of two phases: image collection and fMRI data acquisition, then the fMRI data and statistical analysis were performed using AFNI software package and Origin 6.0 statistical software. The activated brain mappings, the curves of the signal intensity time course, the stereotactic coordinate localization were acquired, and the relative Student’ s t-test were performed.Results The activated brain regions related to the Chinese characters encoding involved bilateral dorsolateral prefrontal gyrus (BA9/46), anterior cingulate gyrus, right lateral inferior prefrontal (BA45), and left fusiform gyrus (BA37), then Chinese characters retrieval activated left extrastriate cortex (BA19/18) and left parietal cortex (precuneus, BA7) besides thoseregions activated above in encoding. The object picture encoding involved bilateral fusiform (BA37), anterior cingulate gyrus , right anteroinferior prefrontal cortex (BA45/47), bilateral dorsolateral prefrontal cortex (BA9/46) and left extrastriate cortex; Whereas picture retrieval activated the right extratriate

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