Study On The Perception Of Visual Motion In Children With Anisometropic Amblyopia Using Functional MRI

Object To detect the pathogenetic mechanism of motion-sensitive cortical deficit in response to motion stimuli in children with anisometropic amblyopia using blood oxygenation level dependent-functional magnetic resonance imaging(BOLD-fMRI). And to analyze the correlation between the decreased cortial activation and visual acuity.Methods BOLD-fMRI technique on 1.5T SIMENS SONATA MRI and block design task conditions were used.The fMRI data were processed with the software of AFNI and Matlab.The experimental stimuli were provieded by neuropsychological software "Presention".The visual stimulus was consisted of stationary vertical sinusoidal gratings which was leftward or rightward at a spatial frequence of 5 cycles per degree (cpd) and moved at 4°/sec.The contrast was 50%, and reduced near the edge of the circle to eliminate sharp edges. The baseline stimulus was a white cross-line at the center of the screen with gray background.Subjects included 20 anisometropic amblyopes and 25 normal subjects.Mydriatic optometry was made before the experiment. Children with system disease or other eye disease were excluded.The functional image data were acquired with a echo-planar imaging (EPI) sequence. Anatomical reference images were collected using a three-dimensional T1-Weight FSPGR imaging sequence. All data obtained were processed and analyzed with the software of AFNI,Matlab and SPM5. The data processing included timing correction,motion correction and three-dimensional smooth. Time-signal intensity curves and functional images could be obtained.After Talairach coordinating function images, the analysis included:①Paired t-tests of cortex activation area was performed in the normal controls with left eye stimulation,right eye stimulation with software SPM5.②Group effects anylysis of cortex activation area was performed between the amblyopic eye (control's left eyes) and the fellow eyes (control's right eyes) in anisometropic amblyopes and normal subjects.③Two-sample t-tests were used to perform intergroup contrast between the amblyopic eyes, the fellow eyes of the anisometropic amblyopia and controls.④Line-correlation were used to perform correlation between the decreased cortical activation and visual acuity. Results①Middle temporal area (MT),middle temporal lobe,inferior temporal lobe and middle occipital lobe (Brodmann area 37,19) were the most obvious activation areas in the normal controls with monocular stimulation; Brodmann area 17,18 were activated including lingual gyrus,cuneus and precuneus,et al;②The dominant cerebral hemisphere of visual cortex activation was right side in the normal controls with monocular stimulation;③In contrast to the normal controls,the spatial extent and intensity of the amblyopic eye in anisometropic amblyopia was obviously decreased in the visual cortex of MT,Brodmann areal9,37,17,18, the mainly decreased areas were middle temporal gyrus,middle occipital gyrus and lingual gyrus; the increased activation area was frontal gyrus;④The fellow eye mainly decreased in the visual cortex of Brodmann area 37,18,19(middle temporal gyrus,cuneus and lingual gyrus);⑤The spatial extent and intensity of the visual cortex activation in the cortex of MT,Brodmann areal9,18(middle temporal gyrus and cuneus) was obviously decreased in the amblyopic eye than in the fellow eye, with middle frontal gyrus increased obviously;⑥There is no linear correlation between the function lesion of cortical activation and visual acuity.Conclusion①Activation in motion-sensitive cortical areas was MT locating at the juncture of Brodmann area37,39 and 19;occipital lobe and frontal lobe were also involved in the delivering of visual motion signa;②The spatial extent and intensity of the visual cortex activation in the visual cortex of Middle temporal area (MT),middle temporal lobe,inferior temporal lobe and middle occipital lobe (Brodmann area 37,19) were decreased in the amblyopic eye in anisometropic amblyopia than in normal controls;the fellow eye was also abnormal;③More visual cortex area was involved when stimulating the amblyopic eye;④There is no linear correlation between the function lesion of cortical activation and visual acuity;⑤Horizontal moving grating includes the light and visual motion stimuli;BOLD-fMRI can be used to study the pathogenetic mechanism of amblyopia.