FMRI Studies On Human Cortical Response To Color Vision Stimuli And Visual Coherent Motion In Anisometropic Amblyopia

Objectives1. To investigate the feasibility of random dot kinematograms used as the stimuli for the functional mapping of cerebral cortex associated with visual coherent motion processing. And to measure the blood oxygenation level dependent responses of the cerebral visual cortex processing visual coherent motion at three different coherence levels.2. Functional localization of the cortical areas that process specifically the color signals and to measure the blood oxygenation level dependent response properties at three different temporal frequencies.3. To explore the properties of the cortical response to visual coherent motion and reveal the possible neural mechanism of cortical deficit of visual motion perception in anisometropic amblyopia so that we can diagnosis and treat it earlier and specifically.Subjects and Methods1. 12 health right-handed volunteers have participated the fMRI studies and passively viewed the stimuli of random dot kinematograms at the coherence levels of 5%,20%,80% respectively. The stimuli were designed and presented by blocked model. All scanning were performed on a SIEMENS Magnetom Sonata 1.5T scanner. The whole brain data of T1WI images,functional images and 3D structural images were acquired. All data were downloaded from the MRI scanner for off-line analysis. AFNI (free software) and SPSS13.0 were used. Activation maps were obtained after data preprocessing and statistical inference. And also, the ROI analysis was done.2. fMRI data were collected on 8 health right-handed volunteers. The fMRI tasks were passively viewing the isoluminant red-green panel at the temporal frequencies of 1Hz,4Hz and 15Hz respectively. These stimuli were designed and presented by blocked model. All scanning was performed on a SIEMENS Magnetom Sonata 1.5T scanner. The whole brain fMRI data of T1WI images,functional images and 3D structural images were collected. All data were downloaded from the MRI scanner for the further off-line analysis. Free software AFNI and SPSS13.0 were used. Activation maps and the ROI analyses were obtained after data preprocessing and statistical inference.3. Six anisometropic amblyopes were recruited and participated in the fMRI research. The stimuli of random dot kinematograms at coherence level 5% were presented by blocked model. All scanning was performed on a SIEMENS Magnetom Sonata 1.5T scanner. The whole brain data of T1WI images,functional images and 3D structural images were acquired. All data were downloaded from the MRI scanner then analyzed off-line. Free software AFNI and SPSS13.0 were used. Activation map was obtained after data preprocessing and statistical inference. Finally, the ROI analysis was done.Results1. Significant activation mappings were observed in the left and right temporo-parieto-occipital cortex, in the area corresponding to hMT+. The central points of the hMT+ activation areas on the left and right hemisphere according to the Talairach coordinate were(:42.9,66.0,3.5),(-42.5,63.5,3.8)respectively. Area hMT+ activation volume was obtained through ROI analysis.2. The bilateral fusiform gyrus activation were observed, located in the ventral occipitotemporal cortex and on the lateral aspect of the collateral sulcus (human V4 area), The central points of the human V4 activation areas on the left and right hemisphere according to the Talairach coordinate were obtained at three different temporal frequencies.3. Unilateral or bilateral hMT+ activation was observed by stimulated the amblyopic eye before and after refractive correction and the fellow eye respectively. The activation volume of hMT+area stimulated through the amblyopia eye before and after refractive correction was much less than that through the fellow eye significantly. But, the difference between the activation volumes of hMT+area stimulated through the amblyopia eye before an after refractive correction was not statistically significant.Conclusions1. Cerebral visual area that processes visual coherent motion signal can be activated significantly by random dot kinematograms and the precise functional mapping of the cortex area processing visual coherent motion signal with BOLD-fMRI techniques; area hMT+ activation volume decrease when coherence level increases can be observed. It's mechanism needs further investigation.2. Isoluminant red-green panel can activate the human V4 efficiently, which is the functional center for processing color signals. Human V4 is sensitive to low temporal frequency stimuli but relatively not sensitive to high temporal frequency stimuli.3. The activation volume of hMT+area when stimulated through the amblyopia eye before or after refractive correction is much less than that through the fellow eye significantly, it suggests that there is a possible cortical deficit for processing the motion visual information.