D.Phil. / Efficient ocular saccadics with a clear visual memory are essential functions in reading fluently. A child needs to sequence the eyes in a controlled jump called a saccade in order to form a picture in the mind of what is being read. The child is therefore primarily aware of a story rather than individual words. This sequential visual input of the written text contributes to efficient reading skills. The letter sequencing therapy used in this research is designed to improve the ocular saccadics and also to simultaneously develop an efficient visual memory. This improves the reading skills and creates good comprehension. The above exercise program illustrated that visual therapy, in general, done not only as a physical exercise but by improving the visual memory, will integrate very quickly into a child's perceptual development. Visual therapy can therefore improve the learning skills in an effective and efficient manner. The development of learning skills can be expanded to benefit children that have poor reading skills as a result of cultural deprivation. Until recently, due to apartheid and cultural differences at the pre school level disadvantaged children were deprived of the same standard of education as advantaged children. This research compared the average visual skills in reading of educationally advantaged children to educationally disadvantaged children. This illustrated the gap created by apartheid, differences in culture and preschool stimulation in the two levels of education. 167 children with no particular learning or visual problems were randomly selected from a group of pupils at an average middle class educationally advantaged white school and an average middle class disadvantaged black school. 100 of the children came from two standard 2 and two standard 3 classes of the educationally advantaged school while 67 of the children came from one standard 2 and one standard 3 class of the educationally disadvantaged school. All the children were evaluated before the therapy program began with respect to ocular fixations, ocular regressions, reading rate, directional attack, span of recognition and relative efficiency. All the children were given letter sequencing therapy under supervision of the class teacher. Strict controls were applied.

Many studies have found evidence of abnormal eye movement control in Parkinson's disease. Deficits in the inhibition of unintended saccades and slowed initiation of intentional saccades have been reported in some, but not all, investigations. Also over recent years the presence of cognitive impairment in a proportion of patients with Parkinson's disease has been highlighted. Efficient use of working memory resources is thought to be involved in the performance of tasks in both domains. With a comprehensive selection of saccadic and neuropsychological tasks, the current study investigated whether aspects of abnormal oculomotor control are associated with impairment of cognitive functions. Nineteen Parkinson's disease patients and eighteen healthy age matched control subjects performed six eye movement tasks and completed a neuropsychological test battery assessing five different aspects of cognitive functioning. Deficits were found in both the oculomotor and the cognitive domain in the group of patients. As a group, the patients made more reflexive errors in antisaccade tasks, more inhibition errors in a delayed response task, and were slower to initiate intentional saccades. The three measures of abnormal oculomotor control were not consistently associated with cognitive impairments or with each other. Longer latencies of correct antisaccades and increased number of errors in a delayed response task were associated with lower scores in different cognitive tests. Reflexive errors in the antisaccade task were not associated with cognitive deficits, but with the tendency to produce very fast visually triggered responses. The results suggest that, at least in Parkinson's disease, different neural mechanisms may be involved in specific aspects of abnormal oculomotor control.

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When a moving dot, which is tracked by the eyes and enclosed in a moving framework, suddenly stops while the enclosing framework continues its motion, the dot is seen to describe a curved path. This illusion can be explained only by assuming that extra-retinal signals are taken into account in interpreting retinal information. The form of the illusion, and the fact that the phenomenal path cannot be explained on the basis of positional information alone, suggests that the perceived path is computed by integrating (instantaneous) velocity information over time. A vector addition model embodying a number of simplifying assumptions is found to qualitatively fit the experimental data. A number of follow-up studies are suggested.

Twelve spatial-cueing experiments examined stimulus-driven and goal-driven control of visual attention orienting under multiple-cue conditions. Spatial cueing involves presenting a cue at a potential target location before a target appears in a display, and measuring the cue's effect on responses to the target stimulus. Under certain conditions, a cue that appears abruptly in a display (direct cue) can speed responses to a target appearing at the previously cued location relative to other uncued locations (called the cue effect). The experiments in this dissertation used a new multiple-cue procedure to decouple the effects of stimulus-driven and goal-driven processes on the control of attention. This technique involved simultaneously presenting a red direct cue (Unique Cue) that was highly predictive of the target location along with multiple grey direct cues (Standard Cues) that were not predictive of the target location. The basic finding was that while cue effects occurred at all cued locations, they were significantly larger at the Unique-Cue location. This finding was interpreted as evidence for stimulus-driven cue effects at all cued locations with additional goal-driven cue effects at the Unique-Cue location. Further experiments showed that Standard-Cue effects could occur independently at multiple locations, that they seemed to involve a sensory-based interaction between the cues and the target, and that they were mediated by a limitedcapacity tracking mechanism. In addition, Unique-Cue effects were found to be the product of goal-driven operations, to interact with Standard-Cue effects, and to involve inhibited processing at unattended locations. These results were explained in terms of a filter-based model of attention control that assigns priority to potential attention-shift destinations. According to this model, stimulus-driven and goal-driven factors generate signals (activity distributions) that drive a filter to open an attention channel at the highest priority location by suppressing the signals at other locations. The final experiments confirmed the central assumptions of this model by providing evidence that the prioritydestination process was sufficient to produce cue effects independent of attention, and that attending to a location involved a suppression of processing at unattended locations. The implications of this model for the larger visual attention literature were also discussed.

The present study tested the hypothesis that distractor-based facilitation of visual search occurs because familiar distractors are processed and rejected in groups. We recorded participants’ eye movements during a visual search task to determine if familiar distractors were associated with an increased average distance between fixations and distractors. The study provided convergent evidence of a strong relation between search efficiency and distractor familiarity, wherein the distance between fixations and distractors increases with the efficiency of search. Further examination of eye movements suggested that the grouping of familiar distractors resulted in an efficient scanning of the search display by increasing the area of the display effectively processed during each fixation and therefore reducing the need to fixate individual distractors.

Background: The 22q11.2 deletion syndrome (22q11.2 DS) causes a wide variety of symptoms, but the central nervous system (CNS) dysfunction is the one most likely to affect the day-to-day life of those affected by this genetic disorder. In addition to affecting the educational needs of children with 22q11.2 DS, the neurological deficits in childhood and adolescence could be related to future psychosis and schizophrenia, which can affect 30% of these patients. Thus, the development of screening tools for CNS dysfunction could help identify children who are most at risk for developing later psychosis, allowing them to receive additional care. As saccadic eye movement behaviours reflect the integrity of multiple brain structures, a battery of oculomotor tasks could help identify neurological deficits. This study sought to test the hypothesis that children with 22q11.2 DS would have deficits in oculomotor performance compared to typically developing children. Methods: A cohort of 16 children with 22q11.2 DS, and 32 age- and sex-matched controls completed prosaccade, antisaccade, delayed memory-guided sequential (DMS) and predictive eye movement tasks. Results: Compared to controls, children with 22q11.2 DS exhibited increased direction errors in the antisaccade task, increased timing errors in the DMS task, as well as decreased predictive and increased regular saccades in the predictive task. The group of children with 22q11.2 DS also exhibited an increase in saccade amplitude in the prosaccade, antisaccade and predictive tasks, increased error in saccade trajectory in the prosaccade, antisaccade and DMS tasks and decreased saccade velocity in the predictive saccade tasks. Conclusion: This study showed that performance in the eye movement tasks could be used to assess injury to the frontostriatal circuitry and cerebellum in children with 22q11.2 DS. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2011-04-29 15:16:39.848