A Study On Saccades Of Children With Learning Disabilities

Eye movements are very important in obtaining exact visual information and providing a behavioural measure of sensorimotor processing and higher cognitive functions of the brain. Researches on eye movement have provided an alternative index of high level cognitive functions. Saccadic paradigms now supplement the traditional methods of cognitive research. The study of eye movements is a popular approach in neurology and psychiatry, especially in schizophrenia research. Eye movement is crucial to humans in allowing them to aim the foveae at objects of interest. Eye movement is important for humans to acquire accurate vision. Saccadic eye movement is used to rapidly adjust the visual axis between the foveae and an object in order to aim, the foveae of both eyes at an object of interest. Saccadic eye movements (saccades) are used to rapidly acquire a given target, which can be done either reflexively or under voluntary control. Saccades have two types: voluntary control of saccades and reflexive saccades. voluntary control of saccades contains anti-saccades and memory-guided saccades.In experiment one, we examined the differences of eye movements between learning disabilities and normal children in pro-saccade task that didn't need will. We discussed the reflexive saccades of Children with learning disabilities. In pro-saccade task, the results suggested that there were no significant differences in the mean percentages of excluding errors, saccadic reaction time, peak velocity of 8°saccade ,The mean percentages of express saccades and saccade gains between the children of learning disabilities and normal. There were no significant differences between grades. The children with learning disabilities performed normal in reflexive saccades. The brain stem and cerebellum related to reflexive saccades are normal.In experiment two, we examined the differences of eye movements between learning disabilities and normal children in anti-saccade task that needed will. We discussed the inhibitory ability in learning disabilities and the neural mechanism related to inhibitory control. The results suggested that the learning disabilities showed significantly higher percentages of errors than the controls, namely, learning disabilities had more saccades to target, not to opposite direction. They had difficulties in inhibiting reflexive saccades and the inhibitory control abilities were poor. The voluntary control of saccades in learning disabilities developed slower and didn't along with their aging. In learning disabilities, there were significant differences in saccade gains between three and six groups. The group six had lower saccade gains than group three. But in normal children, there were no significant differences between three and six. It means that compared to normal children learning disabilities in saccade accuracy developed slower, but they can catch up with normal children. The learning disabilities performed normal in saccade velocity. In sum, the learning disabilities had difficulties in anti-saccade task, developed slower.In experiment three, we examined the differences of spatial working memory abilities and their characteristic of aging between learning disabilities and normal children in memory-guided saccade task. The results suggested that in memory-guided saccade task, the learning disabilities were longer than normal children in saccadic reaction time. Compare to normal children, saccadic reaction time in learning disabilities didn't down along with their aging. In normal children, the three grade children had higher percentage of errors than the six grades, it means that the three grade children had poor inhibitory control abilities than the six. But along with their aging, the percentage of errors was lower and the inhibitory control abilities improved. In the learning disabilities, there were no significant differences between three and six, this means their inhibitory control abilities were not improving with their aging. There were no significant differences between learning disabilities and normal in the percentage of sequence error, this means that their ability in remembering the sequence of target was equal. There were no significant differences between learning disabilities and normal in accuracy and velocity of saccade. In a word, the learning disabilities may have deficits in spatial working memory. To sum up, that the voluntary control of saccadic eye movements of learning disabilities showed abnormal is related to their attention deficits. Compared to normal children, the voluntary control of saccadic eye movements in learning disabilities not only had a lower level, but also developed slower. The brain structure of the learning disabilities is abnormal and it is relate to the abnormity of their eye movements. Their FEF, PF, SEF, DLPFC, frontostriatal and frontoparietal networks may have deficits.