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This research consisted of three individual studies, examining intra- and inter-modal haptic and visual processing in able learners and reading disabled children spanning the elementary school grades. / Performance was measured in terms of: accuracy scores, haptic exploration scores, and exploration times. Higher scores were obtained on the intra-modal visual condition than on any of the conditions involving a haptic component. Increasing the exploration times for haptic stimuli did not significantly improve performance on tasks involving a haptic component. / Performance scores of poor readers were depressed on all tasks, suggesting a general deficit in sensory processing rather than an inter-sensory processing deficit. Poor readers further employed less sophisticated haptic exploration strategies than able readers, suggesting use of less efficient task strategies.

In this thesis, we present a strongly coupled data fusion architecture within a Bayesian framework for modeling the bi-directional influences between the scene and object classification mechanisms. A number of psychophysical studies provide experimental evidence that the object and the scene perception mechanisms are not functionally separate in the human visual system. Object recognition facilitates the recognition of the scene background and also knowledge of the scene context facilitates the recognition of the individual objects in the scene. The evidence indicating a bi-directional exchange between the two processes has motivated us to build a computational model where object and scene classification proceed in an interdependent manner, while no hierarchical relationship is imposed between the two processes. We propose a strongly coupled data fusion model for implementing the feedback relationship between the scene and object classification processes. We present novel schemes for modifying the Bayesian solutions for the scene and object classification tasks which allow data fusion between the two modules based on the constraining of the priors or the likelihoods. We have implemented and tested the two proposed models using a database of natural images created for this purpose. The Receiver Operator Curves (ROC) depicting the scene classification performance of the likelihood coupling and the prior coupling models show that scene classification performance improves significantly in both models as a result of the strong coupling of the scene and object modules. / ROC curves depicting the scene classification performance of the two models also show that the likelihood coupling model achieves a higher detection rate compared to the prior coupling model. We have also computed the average rise times of the models' outputs as a measure of comparing the speed of the two models. The results show that the likelihood coupling model outputs have a shorter rise time. Based on these experimental findings one can conclude that imposing constraints on the likelihood models provides better solutions to the scene classification problems compared to imposing constraints on the prior models. / We have also proposed an attentional feature modulation scheme, which consists of tuning the input image responses to the bank of Gabor filters based on the scene class probabilities estimated by the model and the energy profiles of the Gabor filters for different scene categories. Experimental results based on combining the attentional feature tuning scheme with the likelihood coupling and the prior coupling methods show a significant improvement in the scene classification performances of both models.

This thesis explores the visual functions of the right anterior temporal cortex of the human brain. In Part 1, 92 patients with unilateral temporal- or frontal-lobe excisions and 35 normal control subjects were tested under two experimental conditions (global, local) of a reaction-time task, employing hierarchically structured letters or designs as stimuli. In both versions, the right temporal-lobe group was less affected than other groups by interference from the global aspect of the stimulus. These findings support the hypothesis that the right temporal lobe contributes to global visual processing. In Part 2, the ability to learn a cue-system for discriminating between two targets against a background of visually similar items was examined in 107 patients with unilateral temporal- or frontal-lobe excisions and 37 control subjects, using three versions of a visual-cue learning task. With letters and nonsense syllables, all groups took longer to complete the task when the background information was changed after three learning trials. With abstract designs, only patients with right temporal-lobe lesions failed to show this interference effect after three learning trials, but did so after six. Hence, it is argued that the right temporal lobe plays a role in visual pattern-discrimination learning.

Obstetric brachial plexus palsy, a traumatic birth palsy, results in the paralysis of the upper limb/s. The birth injury is treated at the Brachial Plexus Clinic at King Edward VIII th Hospital, where the Candidate forms part of the Rehabilitation Team. In keeping with worldwide trends, the focus of treatment was on rehabilitation of the upper limb/s. During the course of treatment of these patients, it was observed that the performance of these children varied from excellent to poor. This observation, has not been recorded previously, hence a Research study was initiated to invesitigate this aspect of performance. The study comprised thirty children, between the ages of four and seventeen, whose paralysis was assessed in the conventional pattern. In addition, the visual perceptual abilities of these children were assessed in a variety of batteries, catering for the wide age range. These were: Developmental Test of Visual Motor Integration (1989), Motor Free Perception Test (1972), Developmental Test of Visual Perception (2nd edition), Test of Visual Perceptual Skills - Upper and Lower levels ( Gardner), Jordan's Left-Right Reversal Test (1974), Clinical (Ayres) and General Observations. Although traditionally viewed as a physical disorder, the results of the study indicate that children with obstetric brachial plexus injury present with a significant incidence of below average performance, against the normal population, on most of the assessment batteries. No significant relationship could be established between the severity of the lesion and visual perceptual abilities, owing to the disproportionate numbers of children amongst the different lesions. Further research is required to support and consolidate the findings of this study. It is also recommended that Occupational therapists screen for visual perceptual deficits in such injuries, thus facilitating holistic patient management. / Thesis (M.O.T.)-Unversity of Durban-Westville, 1998.

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