No description available.

No description available.

No description available.

No description available.

Much of the research on differential hemispheric activation as a function of age or the presence of depression suggests that a relative decrease in left hemisphere activation is associated with depression, while a decrease of right hemisphere activation is associated with age. Recent research, however, has demonstrated the role of the right hemisphere in maintaining general behavioral arousal. Pilot data suggest that elderly people experience behavioral over-arousal when presented with stressful or novel environmental stimuli. Equally interesting is the finding in a single-case study that ambient light and noise have a differential effect on behavior presumed to be representative of the left and the right cerebral hemispheres. The left hemisphere appears to be more responsive to ambient light level, with the right hemisphere being more responsive to ambient noise level. The present study sought to provide further support of selective hemispheric activation to bright light, and to examine the relationships among hemi-activation, age and depression by using behavioral measures of lateral anterior (finger tapping rate) and posterior (dichotic listening) cortical functioning. Two identical experiments were employed to evaluate old and young, and depressed and non-depressed sUbjects. Direct evidence of right herni-aging effects on laterality was not significant in the first experiment, but data suggested the possibility of a ceiling effect for behavioral arousal in the older group which was not seen in younger subjects. The second experiment yielded no significant results between depressed and non-depressed groups. Hypotheses of under and over arousal in subjects are proposed to explain findings. Possible implications for treatment and recommendations for further research are proposed. / Ph. D.

Classical Stroop stimuli and newly developed face/word Stroop analog stimuli were used to investigate hemispheric interactions in Stroop interference effects (SEs) and corresponding event-related potentials (ERPs). Lateralized stimuli were presented unilaterally and bilaterally as congruent or incongruent color strip-word or face-word pairs (to invoke right hemisphere (RH) and left hemisphere (LH) specialization, respectively, in the latter case). The common finding for such tasks is that responses for the congruent condition are faster and more accurate than for the incongruent condition (i.e., the SE). A primary prediction is that the SE will be maximized when both the distractor and target components, or distractor alone, are presented to the specialized hemisphere (i.e., LH for words and RH for faces). A total of 88 right-handed University of North Texas students participated in one of four experiments. Participants manually responded to one component of the stimuli (i.e., color, face, or word), while ignoring the other. Behaviorally, participants showed a robust SE across all experiments, especially for the face/word task with word targets. Findings from the face/word Stroop analog tasks also indicated that SEs were produced by selective attention to either faces or words, implicating a role for top-down (controlled) processes. Hemispheric asymmetries were observed only for bilateral presentations of the face/word Stroop analog stimuli and did not differ for word versus face targets. The results suggest that the LH is less susceptible to interference from the RH than vice versa. Electrophysiologically, anterior N1 and P1, posterior P1 and N1, N2, and P3 components were identified. A SE was found for P3 amplitudes, but not latencies, across all four experiments such that the congruent condition generated greater amplitudes than the incongruent condition, suggesting that the P3 is an index of task difficulty. Surprisingly, SEs were also observed for the early ERP components, albeit embedded in higher order interactions. Taken together, the ERP evidence suggests that there is no single locus of the SE, and instead, the SE appears to be distributed over several stages of information processing.

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Abstract not available

The nature of the human brain has preoccupied philosophers and scientists for centuries. As early as the 4th Century BCE, Greek philosophers speculated that the anatomically distinct hemispheres of the brain implied specialisation of function. It was not until the "splitbrain" operations of the 1950s, however, that the precise specialisation of each hemisphere could be demonstrated. The right hemisphere apparently assumed responsibility for spacial, holistic processes, while the left hemisphere processed analytical, sequential tasks. During that same decade, educational psychologists observed two markedly different ways in which individuals perceive and relate to the world. It was later observed that these "cognitive styles" seemed directly related to the bi-polar functions of the right and left hemispheres of the brain. This implied a genetic basis for cognitive style. Subsequent research suggested that cognitive style is to a considerable extent a result of the environment of socialisation, and therefore, different cultures would demonstrate different cognitive styles. Such cultural differences in learning expectations might have serious implications for both teachers and learners in the field of export education. The literature review in this study identified physical, environmental, and experiential factors which appear to influence cognitive style. This information formed the basis of the biographical section of a questionnaire which elicited the learning style preferences of pre-tertiary students from Australia (native speakers), Indonesia and Japan. The study posed the negative hypothesis: There are no significant differences in patterns of cognitive styles between cultures. The results of the field study contradicted the negative hypothesis, identifying significant differences in patterns of cognitive styles between the three cultural groups.

Thesis (M.Communication pathology)-Universiteit van Pretoria, 2001.