FMRI Studies On Face And Object Recognition In Human Anisometropic Amblyopia And Chinese Characters Recognition In Health People

Objective:1. To observe and study the cerebral areas that participates in processing Chinese characters with blood–oxygen-level-dependent(BOLD)functional magnetic resonance imaging (fMRI) techniques. To investigate the validity of the stimuli about Chinese character forms in the functional localization of cerebral areas that response to Chinese characters recognition; to localize these cerebral areas and make a preliminary quantitive analysis of the properties of the BOLD responses.2. Amblyopia constitutes one of the leading causes of vision loss in children generally. Amblyopia is defined as reduced visions in one eye-sometimes both eyes- caused by abnormal input during the formative stages of the visual system. The main cause of amblyopia is the result of competition between each eye's afferent inputs into the visual cortex during the formative stages of the visual system. The face and object recognition is one of the most important function in the life of human being. The objective of this study also: (1) To investigate the cerebral areas that response to face recognition; (2) to localize these cerebral areas and make a preliminary quantitive analysis on their BOLD responses properties, hopefully provided a feasible instruction to the treatment of amblyopia.Materials and Methods:In this study, the magnetic resonance imaging system of 1.5T SIEMENS was used to scan and obtained images and the data. BOLD-fMRI technology and block design were adopted, and the visual stimulations were presented with SA-8800 system. The program was edited with E-prime software.In the block design of the study about Chinese characters, the trial consisted of 6 blocks and each block lasted 32 s. There were 16 character s during every stimulus time, and every character was visually presented for 1s. The stimulation words were grouped into three types: true words, pseudo-words, and no-words. The study of face and object recognition consisted of 4 blocks and each block lasted 30 s. During the stimulation time, the subjects were asked to maintain fixate on the center of the screen and identify which type of the three the Chinese characters belong to or recognize the familiar face ever seen.Ten normal volunteers (19 to 25 years old, four males, visual acuity not less than 1.0) participated in the Chinese character study after giving their informed consent; all the subjects were strongly right-handed and were native Chinese speakers. Subjects included 10 amblyopic patients (6-19yrs.) and 11 normal (18-22yrs). Normal subjects had normal visual acuity in each eye; all the subjects were strongly right-handed. Fully informed, signed consent was obtained from each subject before participation.A turbo spin echo (TSE) sequence was used during anatomic image scans. The first 4 volumes were"dummies"which were scanned before stimulus presentation to allow the MRI signal to reach steady state. Echo planar imaging (EPI) sequences were used during functional scans. 3D anatomical image of each subject was obtained using a three dimensional magnetization prepared rapid acquisition gradient echo (3D MPRAGE) sequence after the functional measurements, providing high-resolution images of the entire brain. The data were analyzed by AFNI to generate brain activation maps.Results:The stimuli of Chinese true-word activated left super and middle frontal gyrus , inferior frontal gyrus(Broca's area) ,left precentral gyrus(BA6),left superior parietal lobule and inferior parietal lobule, and bilateral occipital gyrus. As well as ,the left fusiform gyrus(BA37), right inferior frontal gyrus, bilateral superior and inferior temporal gyrus, and bilateral cingulated gyrus. The volume of the activation in left hemisphere of Chinese true-word processing center was larger than that of right hemisphere.Visual cortex,ventri-temporal cortex and the latter parts of parietal lobe were activated in the face and object recognition in all subjects. The accurate positions in the fusiform areas for face and object recognition is different slightly. In the experimental group, the extent of the activation areas in occipital cortex, ventri-temporal cortex and the latter parietal lobe obviously reducedConclusions:The cortex areas correspond to the Chinese characters form and object (including the furniture, tools and buildings); face recognition can be localized accurately with the BOLD-fMRI techniques. The results confirmed that fMRI techniques is a feasible and non-invasive imaging method for studying language processing in human brain. The dominant hemisphere of processing languages is in the left. Amblyopia was more detrimental for face recognition compared to recognition of buildings and objects.In amblyopic patients, the cortex activation area stimulated with the lazy eye is much less than that with the sound eye. The cortex deficit in the areas processing face recognition is obvious, but the functional deficit of areas for the object processing is not significant. The extent and the intensity of the activation are significantly increased after refraction correction. This further conforms that the refraction correction is useful for improving the visual acuity and its recovery.