M.A. (Psychology) / The goal of the present study was to determine whether there exist any differences in cognitive skills between left-handed dyslexic boys and righthanded dyslexic boys with left hemisphere speech representation. The comparison was made in terms of their verbal and visuo-spatial skills. The motivation for this study resulted from a hypothesis that was formulated by Geschwind and Behan (1982). The hypothesis states that there exists a difference in functional hemispheric asymmetry between left-handed and righthanded dyslexic boys with left hemispheric language representation. By virtue of their explanation of dyslexia in terms of a prenatal hyper secretion of the hormone called testosterone, Geschwind and Behan state that left-handed dyslexic boys will perform better than right-handed dyslexic boys on visuospatial tasks. An empirical study was performed in order to compare the verbal and visuospatial skills of left-handed and right-handed dyslexic boys. Twenty-six lefthanded and 26 right-handed dyslexic boys served as the experimental subjects. All the subjects had left hemispheric language representation. The selection of the experimental subjects was done by means of the dichotic listening technique as well as with the Harris test of lateral dominance. The nine subtests of the Senior South African Individual Scale-Revised served as measuring-instrument. The first five subscales represented the verbal cognitive skills. The visuo-spatial skills were measured with subtests six to nine. The data were statistically analysed by means of Hotelling's T2-test and Student's t-tests. The results indicated that there were no statistically significant differences between left-handed and right-handed dyslexic boys with left hemispheric language representation in terms of any of the verbal and visuo-spatial subtests. The relationship between hand preference, functional hemispheric asymmetry and dyslexia is elucidated by the present study which rejects the GeschwindBehan hypothesis that there exists a difference in functional hemispheric asymmetry between left-handed and right-handed dyslexic boys. A previous study (Hugdahl et aI., 1989) accepted this hypothesis. Further research is thus necessary in order to determine the validity of the Geschwind-Behan hypothesis.

No description available.

No description available.

No / The right hemisphere has often been viewed as having a dominant role in the processing of emotional information. Other evidence indicates that both hemispheres process emotional information but their involvement is valence specific, with the right hemisphere dealing with negative emotions and the left hemisphere preferentially processing positive emotions. This has been found under both restricted (Reuter-Lorenz & Davidson, 1981) and free viewing conditions (Jansari, Tranel, & Adolphs, 2000). It remains unclear whether the valence-specific laterality effect is also sex specific or is influenced by the handedness of participants. To explore this issue we repeated Jansari et al.'s free-viewing laterality task with 78 participants. We found a valence-specific laterality effect in women but not men, with women discriminating negative emotional expressions more accurately when the face was presented on the left-hand side and discriminating positive emotions more accurately when those faces were presented on the right-hand side. These results indicate that under free viewing conditions women are more lateralised for the processing of facial emotion than are men. Handedness did not affect the lateralised processing of facial emotion. Finally, participants demonstrated a response bias on control trials, where facial emotion did not differ between the faces. Participants selected the left-hand side more frequently when they believed the expression was negative and the right-hand side more frequently when they believed the expression was positive. This response bias can cause a spurious valence-specific laterality effect which might have contributed to the conflicting findings within the literature.

Recent research on the neuropsychology of emotion and pain has indicated that emotion and pain are complex processes that may substantially influence each other. Disorders of negative emotion and pain are known to co-occur (Delgado, 2004); however, it is not clear whether negative emotional conditions lead to pain or whether increased pain experiences lead to negative emotion. Further, certain negative emotions, such as hostility or anger, may produce differential effects on the experience of pain, such that they may lead to an increase in pain or a decrease in pain. An increase or decrease in pain perception may lead to altered behavioral, cognitive, and neuropsychological effects in high hostility. In order to more clearly examine the aforementioned relationships, the current experiment examined auditory emotion perception before and after cold pressor pain in high and low hostile men. Additionally, quantitative electroencephalography (QEEG) was used to measure changes in cerebral activation as a result of auditory emotion perception and cold pressor pain. Results indicated that identification of emotion post-cold pressor differed as a function of hostility level and ear. The high hostile group increased identification of stimuli at the right ear after cold pressor exposure, while the low hostile group increased identification of stimuli at the left ear after cold pressor exposure. Primary QEEG findings indicated increased left temporal activation after cold pressor exposure and increased reactivity to cold pressor pain in the high hostile group. Low hostile men had a bilateral increase in high beta magnitude at the temporal lobes and a bilateral increase in delta magnitude at the frontal lobes after the cold pressor. Results suggest decreased cerebral laterality and left hemisphere activation for emotional and pain processing in high hostile men. / Ph. D.

There is clear evidence that the autonomic nervous system (ANS) is lateralized at both the peripheral as well as the central levels of the nervous system. Both the vagus and the sympathetic ganglia asymmetrically innervate the sino-atrial node and the myocardium of the heart. This lateralization has also been observed in afferent as well as efferent projections to nuclei in the brainstem, hypothalamus, and amygdala. Where laterality has not been as clear is in regions of the frontal lobe dedicated to the regulation of autonomic nervous system responses. This study addressed that issue via the implementation of lateralized autonomic response-evoking tasks. With the use of cardiovascular and electrodermal measures, the present study indexed autonomic responses to lateralized stimuli. This study also explored the role of lateralization within sex as well as in relation to reported gender identity. The findings lend support to the right hemisphere as serving a dominant role in regulating sympathetic nervous system activity, while lending less conclusive support for lateralization of parasympathetic nervous system regulation. Men demonstrated greater lateralization for sympathetic nervous system responses across several different metrics of autonomic indices. The exploration of gender variables in relation to lateralization of autonomic responses was generally not supported. / Master of Science

The issue of the laterality of control during unimanual and bimanual coordination was addressed in this thesis. Two tasks were used throughout: a repetitive discrete response task (finger tapping) and a continuous task (circle-drawing). Different mechanisms have been implicated in the temporal control of repetitive discrete movements and continuous movements. The tasks also differ in the degree of spatiotemporal coordination required which might have important implications in the question of laterality of control. The first section of the thesis examined between-hand differences in the dynamics of performance during unimanual and bimanual coordination. During tapping, the dominant hand was faster and less temporally variable than the nondominant hand. During circle drawing the dominant hand was faster, more accurate, less temporally and spatially variable, and produced smoother trajectories than the nondominant hand. During bimanual coordination, several of these asymmetries were attenuated: the rate of movement of the two hands became equivalent (the hands became temporally coupled), the asymmetry in temporal variability during tapping was reduced, and the asymmetry in trajectory smoothness during circle drawing was reduced. The second section of the thesis examined the effects of disrupting motor processes with transcranial magnetic stimulation (TMS) over the left or right primary motor cortex (M1) on the ongoing performance of the hands. In the first study, TMS over left or right M1 during unimanual tapping caused large disruptions to tapping with the contralateral hand but had little effect on the ipsilateral hand. In contrast, for a subset of trials during bimanual tapping, two lateralized effects of stimulation were seen: the effect of TMS on the contralateral hand was greater after stimulation over left M1 than after stimulation over right M1, and prolonged changes in inter-tap interval were observed in the left hand regardless of the side of stimulation. In the second study, TMS over left M1 during circle drawing decreased the accuracy of drawing with both the contralateral and ipsilateral hand, whereas TMS over right M1 decreased accuracy of drawing only with the contralateral hand. This lateralized effect was not limited to the bimanual case, but was also apparent during unimanual drawing. The final chapter addressed issues in bimanual motor control after unilateral stroke. Performance of the affected limb was examined during unimanual and bimanual coordination in a group of stroke patients with varying levels of impairment. The results indicated an improvement in the performance of the affected limb for some patients with mild to moderate, but not severe upper limb motor deficits during bimanual movement. The improvements were limited to the patients who showed evidence of temporal coupling between the hands. These findings support the hypothesis that the dominant motor cortex has a role in the control of both hands during bimanual coordination. In addition, the dominant hemisphere appears to play a role in controlling both hands during unimanual movements which require a greater degree of spatiotemporal coordination. The final study suggests that temporal coupling between the limbs is crucial for the facilitation of performance of the affected limb during bimanual coordination, which has both theoretical and practical implications.

Reflective eye movementa as a function of cognitive nodes were studied in English speaking and Spanish bilingual populations (N=20). A total of 40 questions were asked with the initial, lateral eye movement recorded. Questions consisted of 20 verbal-mathematical type intended to elicit right-eye movement and 20 spatial questions intended to elicit left-eye movement. A significant difference in responses was found dependent on the type of questions asked (F=114.3421,p<.001). No significant differences were obtained between the two groups.

This thesis deals with the laterality and the ways of diagnosis at children. It is divided into three parts - theoretical, practical and appendixes. The theoretical part deals with laterality, methods of diagnostic and methodology of work with left-handed pupil at the beginning of the school attendance. The aim of research in the practical part of the thesis was to find information about working with left-handed pupils between the students of primary teaching and teachers in practise. The appendixes of this thesis include the questionnaires used for the practical part of the thesis and worksheets for pupils to relax their hand while writing.

published_or_final_version / abstract / toc / Linguistics / Master / Master of Philosophy