No description available.

There are currently many statements about the effects of hemispheric specialization of the brain upon children's cognitive processing and therefore, upon content or modes of instruction. Before educators can accept or even test these statements, it is important to devise easy-to-use measures of hemispheric functioning and to study their relationship to established measures of achievement and linguistic and cognitive development. Current research in brain functioning has indicated that conjugate-lateral eye movement direction (the direction in which a person looks while thinking) can be a sensitive indicator of which cerebral hemisphere is initially activated. The central purpose of this investigation was to analyze the effects of the stimulus characteristics of reflective questions of verbal and spatial nature on the conjugate-lateral eye movement (CLEM) behavior of right-handed children from fourth, fifth, and sixth grades. A major objective was to determine whether data on children’s CLEM responses would better support a model of characteristic individual differences or a model of differentiation by question type. The testing instrument devised for this purpose was the Reflective Questions Test (RQT) which included both Verbal and Spatial subtests. In an experimenter-facing-subject paradigm with a sample of 60 (30 boys, 30 girls), conjugate-lateral eye movement was found to be easily observable and question type was found to influence the direction of eye movement, thus supporting a differentiation by question type model. Verbal questions elicited significantly more rightward CLEMs than spatial questions and spatial questions elicited significantly more leftward CLEMs than verbal questions fn the sample studied. No significant sex differences were found. These results seem to be consistent with the neuropsychological theory that once hemispheric specialization has occurred with normal right-handed children, the left hemisphere mediates language functions and the right hemisphere mediates spatial functions. Examining the number of directionally appropriate CLEM responses, a two-way analysis of variance (verbal and spatial question type by grade level) yielded no main or interaction effects. The results suggest that although children in grades four, five, and six tended to gaze in different directions while responding to verbal than while responding to spatial questions, the rate of responses appropriate to the question (gazing in the direction predicted) was no greater for verbal than for spatial questions. Further, the means for question types were almost identical across grade levels for CLEM responses to verbal and to spatial questions, supporting a no-change model of neuropsychological function, which contends that within the later childhood years, hemispheric specialization is well developed. The Reflective Questions Test was found to have high inter-rater reliability (.94) and temporal stability (.78). These results indicate that the RQT produced reliable and stable results for the sample studied and support the appropriateness of the RQT for future refinement and use in educational research of this type. Correlations of the RQT with other measures of linguistic and cognitive development, and educational ability were found to be nonsignificant. These results suggest that hemispheric activation as indexed by the RQT at this age range may be largely independent of measures traditionally associated with school performance. The results of this investigation have provided normative data on normal right-handed children, thereby providing a comparative basis for future research with children of the same age from other populations such as the learning disabled. / Ed. D.

M.A. / The study aims to determine whether statistically significant differences exist between boys with attention deficit hyperactivity disorder (ADHD) and boys without ADHD with regard to hemispheric language lateralization and the laterality of various modalities (handedness, eyedness and footedness). According to the literature, a possible connection exists between abnormal lateralization patterns and various developmental disorders (Corballis, 1983; Geschwind & Behan, 1982; Hiscock, 1988, McFarland, 1981; Turkewitz, 1988). Lateralization in the current study refers to hemispheric language specialisation, hand dominance, foot dominance and eye dominance. In most people these functions are lateralized to the one side of the body by the age of seven (Kalat, 1995; Kolb & Whishaw, 1996). They typically manifest a dominant left hemisphere for language and a right-sided dominance for handedness, footedness and eyedness. The result is a dominant left hemisphere, due to the left side of the brain controlling the right side of the body. Some children however manifest insufficient or poor lateralization of these functions. For purposes of this study, it would imply that the functions of language specialisation, handedness, footedness and eyedness are not all lateralized to one side of the body. A possible connection between this poor or insufficient lateralization and ADHD might exist. According to the DSM IV (1997) the essential feature of ADHD is a persistent pattern of inattention and/or hyperactivity/impulsivity that is more frequent and severe than is typically observed in individuals at a comparable level of development. Some of these symptoms causing impairment must have been present before age seven, although many individuals are only diagnosed after the symptoms have been present for a number of years. Impairment resulting from the symptoms should be present in at least two settings, for example, at school and at home. Clear evidence must exist of interference with developmentally appropriate social, academic, or occupational functioning. An empirical study was conducted in order to compare the hemispheric language specialisation, handedness, eyedness and footedness of the various subjects. The subjects consisted of 20 ADHD boys (8 -12 years) who met the criteria of the DSM IV and 20 Non-ADHD boys (8-12 years) without any learning problems. Various interference variables were controlled in the selection of the subjects (see section 5.2.3) Kimura's dichotic listening technique was used to measure hemispheric language specialisation and the Harris-test for Lateral Dominance was used to measure handedness, eyedness and footedness. Wilks's lambda, Pearson's chi-quadrant and Student's t-tests were used during statistical analysis of data. Results indicated statistically significant differences between ADHD boys and non-ADHD boys with regard to hemispheric language specialisation, handedness and footedness. Overall, the results indicated that the ADHD boys are not as strongly lateralized as the non-ADHD boys. The non-ADHD boys showed a stronger left hemispheric language specialisation, right hand dominance and right foot dominance. No statistical differences were recorded with regard to eyedness. The current study provides possible theoretical support for the theory that a connection exists between poor or insufficient lateralization patterns and children with ADHD. However, the study only focused on white boys between the ages of 8-12 years. Further studies involving different age groups, cultures and gender are recommended.

This study examined the effectiveness of Mind Mapping (a diagram of the structure of ideas in an associative manner, using graphics, color and key words) as a note-taking device in a training course in a large, high-tech corporation, as compared to traditional note-taking. The population for this study consisted of personnel employed by a major high-tech firm, that had voluntarily registered for a Mind Mapping training class. The effect of Mind Mapping was measured by the pre-test and post-test of the control and experimental groups.

Large scale functional brain networks, defined by synchronized spontaneous oscillations between spatially distinct anatomical regions, are essential to brain function and have been implicated in disease states, cognitive capacity, and many sensing and motor processes. In this work, we sever the corpus callosum in the rodent model to determine if structural connectivity (specifically the primary interhemispheric pathway) organizes and influences bilateral functional connectivity and brain-wide spatiotemporal dynamic activity patterns. Prior to the callosotomy work, resting state brain networks were evaluated using blood oxygen level dependent (BOLD) and cerebral blood volume (CBV) magnetic resonance imaging contrast mechanisms, and revealed that BOLD and CBV provide highly similar spatial maps of functional connectivity; however, the amplitude of BOLD connectivity was generally stronger. The effects of extended anesthetic durations on functional connectivity were also evaluated revealing extended isoflurane anesthetic periods prior to the switch to dexmedetomidine attenuates functional activity for a longer duration as compared to a shorter isoflurane paradigm. We also observed a secondary significant evolution of functional metrics occurring during long durations of dexmedetomidine use under the currently accepted and refined dexmedetomidine sedation paradigm. Taking these previous findings into account, we moved forward with the callosotomy study. Functional network integrity was evaluated in sham and full callosotomy groups using BOLD and electrophysiology. Functional connectivity analysis indicated a similar significant reduction in bilateral connectivity in the full callosotomy group as compared to the sham group across both recording modalities. Spatiotemporal dynamic analysis revealed bilaterally symmetric propagating waves of activity in the sham data, but none were present in the full callosotomy data; however, the emergence of unilateral spatiotemporal patterns became prominent following the callosotomy. This finding suggests that the corpus callosum could be largely responsible for maintaining bilateral network integrity, but non-bilaterally symmetric propagating waves occur in the absence of the corpus callosum, suggesting a possible subcortical driver of the dynamic cascading event. This work represents a robust finding indicating the corpus callosum's influence on maintaining integrity in bilateral functional networks.

No description available.

Alors que les hypothèses de valence et de dominance hémisphérique droite ont longtemps été utilisées afin d’expliquer les résultats de recherches portant sur le traitement émotionnel de stimuli verbaux et non-verbaux, la littérature sur le traitement de mots émotionnels est généralement en désaccord avec ces deux hypothèses et semble converger vers celle du décours temporel. Cette dernière hypothèse stipule que le décours temporal lors du traitement de certains aspects du système sémantique est plus lent pour l’hémisphère droit que pour l’hémisphère gauche. L’objectif de cette thèse est d’examiner la façon dont les mots émotionnels sont traités par les hémisphères cérébraux chez des individus jeunes et âgés. À cet effet, la première étude a pour objectif d’évaluer l’hypothèse du décours temporel en examinant les patrons d’activations relatif au traitement de mots émotionnels par les hémisphères gauche et droit en utilisant un paradigme d’amorçage sémantique et une tâche d’évaluation. En accord avec l’hypothèse du décours temporel, les résultats obtenus pour les hommes montrent que l’amorçage débute plus tôt dans l’hémisphère gauche et plus tard dans l’hémisphère droit. Par contre, les résultats obtenus pour les femmes sont plutôt en accord avec l’hypothèse de valence, car les mots à valence positive sont principalement amorcés dans l’hémisphère gauche, alors que les mots à valence négative sont principalement amorcés dans l’hémisphère droit. Puisque les femmes sont considérées plus « émotives » que les hommes, les résultats ainsi obtenus peuvent être la conséquence des effets de la tâche, qui exige une décision explicite au sujet de la cible. La deuxième étude a pour objectif d’examiner la possibilité que la préservation avec l’âge de l’habileté à traiter des mots émotionnels s’exprime par un phénomène compensatoire d’activations bilatérales fréquemment observées chez des individus âgés et maintenant un haut niveau de performance, ce qui est également connu sous le terme de phénomène HAROLD (Hemispheric Asymmetry Reduction in OLDer adults). En comparant les patrons d’amorçages de mots émotionnels auprès de jeunes adultes et d’adultes âgés performants à des niveaux élevés sur le plan comportemental, les résultats révèlent que l’amorçage se manifeste unilatéralement chez les jeunes participants et bilatéralement chez les participants âgés. Par ailleurs, l’amorçage se produit chez les participants âgés avec un léger délai, ce qui peut résulter d’une augmentation des seuils sensoriels chez les participants âgés, qui nécessiteraient alors davantage de temps pour encoder les stimuli et entamer l’activation à travers le réseau sémantique. Ainsi, la performance équivalente au niveau de la précision retrouvée chez les deux groupes de participants et l’amorçage bilatéral observé chez les participants âgés sont en accord avec l’hypothèse de compensation du phénomène HAROLD. / While the right hemisphere and valence hypotheses have long been used to explain the results of research on emotional nonverbal and verbal stimuli processing, the literature on emotional word processing is highly inconsistent with both hypotheses, but appear to converge with the time course hypothesis. The time course hypothesis holds that in the processing of some parts of the semantic system the time course of activation is slower in the right hemisphere compared to the left hemisphere. The goal of this thesis was to find insight into the ways in which words with emotional words are processed in the cerebral hemispheres in young and older individuals. To this end, the first study investigated the time course hypothesis looking at the activation pattern of emotional words in the left and right hemispheres, using the priming paradigm and an evaluation task. Consistent with the time course hypothesis, the results in males revealed an early and later priming in the left and right hemispheres, respectively. The results for females, however, were consistent with the valence hypothesis, since positive and negative words were optimally primed in the left and right hemispheres, respectively. As females are considered more emotional than males, their results may be due to the nature of the task, which required an explicit decision concerning the target. The second study looked at the possibility that the preservation with age of the ability to process emotional words would follow the compensatory role of bilateral activation in high performing older individuals known as the HAROLD phenomenon (Hemispheric Asymmetry Reduction in OLDer adults). Comparing the pattern of emotional word priming in a group of equally high performing older and younger, it was shown that while priming occurred unilaterally in young participants, the pattern of priming in older participants appeared to be bilateral. The occurrence of priming in older adults occurred with a tiny delay, though, that may be due to an increase in sensory thresholds that causes older adults to need more time to encode stimuli and start activation through the semantic network. Thus, the bilateral pattern of priming and the equivalent level of performance in older adults provide behavioral evidence supporting the compensatory role of the HAROLD phenomenon.

A large body of research has depicted relative arousal of the left and right cerebral hemispheres as related to utilization of particular defensive coping styles, level of anxiety, and perceptual styles. The right and left hemispheres are also presented in the literature as differing in visual-spatial and verbal-auditory short term memory abilities. The present research studied 127 right handed undergraduates' relative performance on forward spatial and digits memory spans in relation to hemispheric lateralization and other perceptual and personality variables hypothesized in the literature to be related to hemispheric arousal. It was hypothesized that the forward spatial and digit memory spans would display asymmetrical sensitivity to hemispheric arousal. That is, in a series of successive factor analyses, a hemispheric balance factor, a trait anxiety factor, and a short term memory factor would emerge. The three factors were hypothesized to be unrelated to each other. During an initial group pretesting, subjects were given pencil and paper measures of handedness, trait anxiety, and several defensive coping styles. During a second individual testing, subjects were administered measures of short term memory, field independence, and a computerized presentation of geometric designs which measured the subjects ability to detect differences which occurred at either the global or analytic level (Navon task). The factor analyses revealed only the hypothesized trait anxiety factor. The hypothesized short term memory and hemispheric balance of arousal factors did not emerge. Instead, a. defensive coping style factor and separate verbal—auditory and visual-spatial short term memory factors emerged. Several methodological difficulties of the present study which possibly contributed to the failure of the two hypothesized factors to emerge were discussed. Several additional findings, including sex differences in hemispheric lateralization, were presented. Also, signal detection analysis revealed a pattern such that trait anxious subjects were biased toward over-reporting differences on the Navon task. Implications for further research were presented.

Alors que les hypothèses de valence et de dominance hémisphérique droite ont longtemps été utilisées afin d’expliquer les résultats de recherches portant sur le traitement émotionnel de stimuli verbaux et non-verbaux, la littérature sur le traitement de mots émotionnels est généralement en désaccord avec ces deux hypothèses et semble converger vers celle du décours temporel. Cette dernière hypothèse stipule que le décours temporal lors du traitement de certains aspects du système sémantique est plus lent pour l’hémisphère droit que pour l’hémisphère gauche. L’objectif de cette thèse est d’examiner la façon dont les mots émotionnels sont traités par les hémisphères cérébraux chez des individus jeunes et âgés. À cet effet, la première étude a pour objectif d’évaluer l’hypothèse du décours temporel en examinant les patrons d’activations relatif au traitement de mots émotionnels par les hémisphères gauche et droit en utilisant un paradigme d’amorçage sémantique et une tâche d’évaluation. En accord avec l’hypothèse du décours temporel, les résultats obtenus pour les hommes montrent que l’amorçage débute plus tôt dans l’hémisphère gauche et plus tard dans l’hémisphère droit. Par contre, les résultats obtenus pour les femmes sont plutôt en accord avec l’hypothèse de valence, car les mots à valence positive sont principalement amorcés dans l’hémisphère gauche, alors que les mots à valence négative sont principalement amorcés dans l’hémisphère droit. Puisque les femmes sont considérées plus « émotives » que les hommes, les résultats ainsi obtenus peuvent être la conséquence des effets de la tâche, qui exige une décision explicite au sujet de la cible. La deuxième étude a pour objectif d’examiner la possibilité que la préservation avec l’âge de l’habileté à traiter des mots émotionnels s’exprime par un phénomène compensatoire d’activations bilatérales fréquemment observées chez des individus âgés et maintenant un haut niveau de performance, ce qui est également connu sous le terme de phénomène HAROLD (Hemispheric Asymmetry Reduction in OLDer adults). En comparant les patrons d’amorçages de mots émotionnels auprès de jeunes adultes et d’adultes âgés performants à des niveaux élevés sur le plan comportemental, les résultats révèlent que l’amorçage se manifeste unilatéralement chez les jeunes participants et bilatéralement chez les participants âgés. Par ailleurs, l’amorçage se produit chez les participants âgés avec un léger délai, ce qui peut résulter d’une augmentation des seuils sensoriels chez les participants âgés, qui nécessiteraient alors davantage de temps pour encoder les stimuli et entamer l’activation à travers le réseau sémantique. Ainsi, la performance équivalente au niveau de la précision retrouvée chez les deux groupes de participants et l’amorçage bilatéral observé chez les participants âgés sont en accord avec l’hypothèse de compensation du phénomène HAROLD. / While the right hemisphere and valence hypotheses have long been used to explain the results of research on emotional nonverbal and verbal stimuli processing, the literature on emotional word processing is highly inconsistent with both hypotheses, but appear to converge with the time course hypothesis. The time course hypothesis holds that in the processing of some parts of the semantic system the time course of activation is slower in the right hemisphere compared to the left hemisphere. The goal of this thesis was to find insight into the ways in which words with emotional words are processed in the cerebral hemispheres in young and older individuals. To this end, the first study investigated the time course hypothesis looking at the activation pattern of emotional words in the left and right hemispheres, using the priming paradigm and an evaluation task. Consistent with the time course hypothesis, the results in males revealed an early and later priming in the left and right hemispheres, respectively. The results for females, however, were consistent with the valence hypothesis, since positive and negative words were optimally primed in the left and right hemispheres, respectively. As females are considered more emotional than males, their results may be due to the nature of the task, which required an explicit decision concerning the target. The second study looked at the possibility that the preservation with age of the ability to process emotional words would follow the compensatory role of bilateral activation in high performing older individuals known as the HAROLD phenomenon (Hemispheric Asymmetry Reduction in OLDer adults). Comparing the pattern of emotional word priming in a group of equally high performing older and younger, it was shown that while priming occurred unilaterally in young participants, the pattern of priming in older participants appeared to be bilateral. The occurrence of priming in older adults occurred with a tiny delay, though, that may be due to an increase in sensory thresholds that causes older adults to need more time to encode stimuli and start activation through the semantic network. Thus, the bilateral pattern of priming and the equivalent level of performance in older adults provide behavioral evidence supporting the compensatory role of the HAROLD phenomenon.