Les resultats de plusieurs etudes appuient la notion d'une relation potentielle entre le sommeil paradoxal (SP) et le traitement de l'information. La presente recherche avait pour but d'examiner de plus pres cette relation en etudiant l'activite interhemispherique (EEG) en SP durant un apprentissage intensif de langue second. Huit etudiants droitiers unilingues anglophones, 5 femmes et 3 hommes (moyenne d'age = 24 ans), inscrits dans un cours d'immersion en francais d'une duree de six semaines, ont dormi en laboratoire pendant neuf nuits: 3 nuits avant le debut du cours, 2 nuits apres le cours. Nous avons mesure l'activite interhemispherique en SP a partir de deux sites: parieto-temporal (W1 et W2) ainsi que frontal (F3 et F4). En guise de comparaison, l'activite cerebrale a l'eveil a egalement ete enregistree pendant une serie de taches cognitives; soit la relaxation avec les yeux ouverts et fermes, l'ecoute de trois pieces musicales (classique, paroles francaises et paroles anglaises), et lors de la lecture d'un texte francais et anglais. Des analyses de la variance (ANOVAs) a mesures repetees ont revele des tendances lineaires significatives () au niveau du site parieto-temporal en SP pour les 7 frequences suivantes: delta, theta, alpha, beta, beta 1, beta 2, et totale. Cex memes analyses avec les donnees du site frontal ont decele des tendances lineaires significatives ($) dans deux frequences; theta et alpha. Il ressort de l'examen des resultats que la dominance de l'hemisphere gauche, apparente au debut du cours, s'est dirigee davantage vers une symetrie interhemispherique a mesure que le cours se deroulait. Des analyses identiques a partir des donnees enregistrees a l'eveil n'ont pas decele les tendances consistantes observees en SP. Ces donnees offrent donc un appui supplementaire au lien apparent entre le SP et le traitement de l'information, et suggerent que le sommeil serait une periode privilegiee pour mesurer le traitement hemispherique d'une langue seconde. Des analyses plus approfondies en utilisant des donnees provenant des autres stades de sommeil, nous permettrons de conclure si ce phenomene est reserve exclusivement au SP.

The Spontaneously Diabetic Wistar B.B. Rat (SDR) is considered to be a genetically determined animal model of human Type-1 diabetes. The overall objective of this thesis was to elucidate the behavioral and neurochemical profile of the SDR. This objective was attained using various pharmacological, behavioral and neurochemical approaches. The course of the changes was followed sequentially, at discretely defined time frames (0-2, 2-8 and 8-12 months duration of diabetes), to explore and characterize the contended dysfunctions. Overall, it was found that the insulin treated SDR exhibited a significantly attenuated locomotor and rearing response to the systemically administered dopamine agonists d-amphetamine and amfonelic acid. In the case of d-amphetamine, it was found that the attenuated response was robust and chronic as it persisted across all three time frames. The attenuated response of the insulin treated SDR to amfonelic acid demonstrated that the behavioral deficit could also be elicited by a dopamine agonist with a different mechanism of action from d-amphetamine. In a nonpharmacological experiment, it was found that the insulin treated SDR manifested a significantly attenuated nocturnal locomotor and rearing response, particularly to transitional photoperiodic cues. This deficit in responding was chronic and robust as it was observed across all three time frames. The possible neurochemical substrates of the aforementioned effects were investigated. A post-mortem neurochemical analysis of the region specific basal levels of CNS catecholamines and metabolites, in the insulin maintained and deprived SDR, was undertaken. There were no significant differences between the insulin maintained SDR and non-diabetic littermates or genetically distinct controls. The cessation of insulin administration to the SDR for four consecutive days resulted in significant increases in the levels of norepinephrine in the cortex and hypothalamus, dopamine in the hippocampus, and homovanillic acid in the striatum. The neurochemical response of the insulin treated SDR was assessed following a pharmacological challenge. The SDR was exposed to a single dose of (1.0 mg/kg, i.p.) amfonelic acid. The SDR exhibited a significantly greater reduction in the post-mortem levels of dopamine in the striatum, midbrain, and olfactory bulbs as well as striatal norepinephrine. The behavioral effects elicited by d-amphetamine and amfonelic acid are believed to be dopamine mediated. Thus, it was hypothesized that one source of the observed neurochemical and behavioral deficits may be related to an impairment of dopaminergic neurotransmission. Therefore, the concomitant measurement of spontaneous nocturnal locomotor activity and levels of interstitial dopamine from the ventral striatum was measured using in vivo microdialysis. No significant differences between the insulin treated SDR and controls were found. The SDR did exhibit significantly lower levels of locomotor activity. In a different vein, the behavioral response of the insulin treated SDR was assessed following exposure to environments varying in degree of novelty. It was found that the SDR exhibited a heightened behavioral response to novelty-stress. The insulin maintained SDR manifested a greater aversion to the anxiogenic regions of the open field and elevated plus maze whilst being treated with chlordiazepoxide. The anxiolytic effects of this drug were significantly attenuated in the SDR when compared to controls. In essence, it would appear that the SDR when treated with insulin and unchallenged by: (1) withdrawal of insulin treatment, (2) pharmacological stimulation or, (3) environmental stimulation, is able to maintain relatively stable baseline levels of brain catecholamines and behavior. (Abstract shortened by UMI.)

Children with Attention Deficit Hyperactivity Disorder (ADHD) have been reported to have electroencephalographic (EEG) abnormalities in the form of increased levels of theta band activity and lower than normal levels of beta band activity. The purpose of the present study was to determine if these abnormalities can also be observed in adults with ADHD. There were 32 control subjects, 25 subjects with ADHD of the primarily hyperactive type (ADHDhy), and 17 subjects with ADHD of the primarily inattentive type (ADHDpi). For the purposes of analysis, the ADHDhy and ADHDpi groups were combined to form a CLINICAL group. The subjects were right handed males and females between the ages of 20 and 50 years of age. During the study, EEG activity was recorded from 19 electrode sites while subjects sat with their eyes open and eyes closed, and while they performed a variety of tasks including: the Tests of Variability of Attention (TOVA), a reading task, a mental rotation task, a selective attention task, and a listening task. The results of the discriminant function analyses produced functions that correctly classified an average of 60 out of 74 of the control and ADHD subjects during the TOVA, listening, and selective attention tasks (p < .0005). An ANOVA of inter-hemispheric activity revealed that only the ADHDpi group were significantly different from the control group with more right than left hemispheric activity in the delta band during the mental rotation task (p < .006). A paired t-test analysis of inter-hemispheric activity showed that both the ADHDhy and ADHDpi groups had different percentage levels of right and left hemispheric activity (p < .005) during the performance of the eyes closed, T.O.V.A., mental rotation, and reading tasks; there were no significant differences in the control group in any of these comparisons. A MANOVA of regional (frontal, central, posterior, left temporal, and right temporal) activity revealed statistically significant differences in the theta/beta ratio during the eyes closed condition for the ADHDhy group with a higher ratio in the frontal region and right temporal area (p < .006). The results suggest that the differences between normal and ADHD children continues into adulthood but that the magnitude of the differences is reduced. A dysfunction in EEG activity caused by a maturational lag is supported by the results of this study. Based on the results of the analyses, recommendations are made as to which frequency bands and electrode sites should be targeted for use in neurotherapy.

This study provides evidence suggesting that male Young Offenders (YOs) (n = 40) can be significantly discriminated from male Non-Young Offenders (NYOs) (n = 40) on the basis of various neuropsychological measures of executive functioning. More specifically, YOs had lower factor scores than NYOs on measures reflecting higher order cognitive functioning ($r\sp2$ =.17), verbal fluency ($r\sp-$ =.07), cognitive flexibility ($r\sp2$ =.05), and spatial/perceptual functioning ($r\sp2$ =.04). A linear discriminant function ($r\sp2$ =.33) provided an overall classification hit rate of 73.75%. Factor scores of Property offenders derived from demographic variables were moderately correlated (r = $-$.48) with higher order cognitive factor scores, suggesting that greater cognitive deficits are associated with a poorer socialization outcome, more frequent and versatile criminal activity, and a greater dependence on alcohol and drugs. No significant correlations were noted for Violent or Sexual offenders, suggesting these type of offenders did not display any cognitive deficits per se. Based on these findings, a neuropsychologically evidence-based developmental hypothesis of criminality is proposed.

This thesis examined changes in the brain's responses ("evoked potentials") during the transition from consciousness to unconsciousness. A negative wave, "N1", peaking at about 100 ms is affected by the subject's extent of attention/consciousness. Unfortunately, this same peak is also affected by manipulation of the physical parameters of the stimulus. The extent to which a component is affected by a physical or psychological parameter is often difficult to determine in the awake and alert subject. There are two principal reasons for this. Manipulation of the physical stimulus may inadvertently cause a change in the psychological state of the subject. Thus, subjects will attend to louder stimuli even if not asked to do so. Manipulation of the subject's level of attention also poses a dilemma. The change in the level of attention is always relative, not absolute. When subjects are asked to ignore stimuli, they are not able to do so. The sleep period provides a convenient means to resolve this dilemma. It is the period of time during which subjects are least attentive to, and thus least conscious of, their external environment. It can therefore be used to provide a baseline-near absolute level of attentiveness. Three experiments were run. In the first experiment, tones were presented to subjects at a rapid 600 ms interstimulus interval, during sleep onset (the transition period from Wakefulness through to Stage 2 of sleep). Subjects were not required to respond to the stimuli. In Experiment 2 stimuli were presented at a relatively slow rate (every 1000 msi. Again, subjects were not required to make an overt response. In Experiment 3 spatial resolution was enhanced by recording from 29 scalp electrode sites. Topographic changes to the P1-N1-P2 evoked potential complex during sleep onset were investigated. In addition, several novel methodological changes were implemented in this final study. Stimuli were presented in an oddball paradigm. Rare "target" tones were randomly presented within a train of frequently occurring standard stimuli. Subjects were required to press a hand held button whenever they detected a target stimulus. A radical interpretation of the present data is that a late negative wave, "N1", is entirely endogenous in nature. N1 may reflect the extent of the subject's conscious awareness of the external stimulus. As such, the N1 component of the auditory evoked potential provides a convenient and easy means to monitor the level of attention/consciousness in a number of applied settings. (Abstract shortened by UMI.)

This study was designed to gain a better understanding of the phenomenon of athletic excellence with regard to the mental aspects. The information was derived from the interviews with nine highly successful Japanese athletes. A thorough analysis of their experiences, feelings, and insights uncovered various mental factors underlying their athletic success. Content analyses of the interview data resulted in the identification of six main topic areas: (1) growth and development of exceptional athletes, (2) athletes' views on their sports and lives, (3) mental approaches to daily practice, (4) mental approaches to competitions, (5) psychological enhancement strategies, and (6) mental elements essential to athletic success. Based on the interview findings in these six main topic areas, a conceptual model of the mental path to athletic excellence was proposed from a holistic viewpoint. This model integrates five main components: personal qualities of the athlete, personal histories, mental strategies, nurturing experiences, and environmental variables.

Paired pulse stimulation is used to estimate the refractory period of the directly stimulated substrate of intracranial self stimulation. When the delay between the conditioning (C) pulse and the test (T) pulse is shorter than the refractory period, the T pulse elicits very little behaviour. The T pulse is ineffective because the substrate has not had time to recover from refractoriness. Conversely, when the C-T delay is longer than the refractory period, one would expect the T pulse to be fully effective. In practice, however, T pulses often fall 20% short of full effectiveness. This anomalous shortfall has received scant attention. The present study documented this anomaly, and tested a theory about its cause. Experiment 1 tested at very long C-T delays and at closely spaced C-T delays. It was found that T pulses always became fully effective, but often only at C-T delays of 30 ms. Experiment 2 determined that the shortfall is not an undersampling or scaling artifact. T pulse effectiveness was calculated using standard 0.1 log$\sb $ unit gradations, and then again with 0.05 log$\sb $ unit gradations, the finest practical scaling. The fine scaling had no effect on the shortfall. T pulse effectiveness is usually estimated with six replications per C-T delay. This limits statistical power, and estimates are necessarily approximate. Experiment 3 used an automated testing apparatus to generate very large numbers of replications: as many as 120 per C-T delay. The resulting effectiveness curves are extremely precise. They show that effectiveness usually rises to 80% within 5 ms. Effectiveness stays near that level until 25 ms. Then it gradually rises to 100% at 35 ms. Effectiveness remains steady near 100% until at least 50 ms, the longest C-T interval that was tested. Experiment 4 tested the theory that the shortfall is caused by a relative refractory period, a subnormal period, or a supernormal period by using T pulse currents that were 40% larger than the C pulse currents. Large T pulses eliminate relative refractory, subnormal, and supernormal effects, but they did not eliminate the shortfall. It follows that the shortfall is not caused by any of these factors.

The purpose of the study was to evaluate motor and sensory components of trunk control in individuals with unilateral cerebral stroke and to identify differences in response between right and left sided lesions. Eighteen subjects, who were unstable in standing or unable to stand were tested. There were 9 subjects with right hemiplegia and 9 subjects with left hemiplegia for the motor testing and 8 subjects in each group for the sensory testing. Subjects were tested on a motorized seat that could be tilted approximately 15$\sp\circ$ to either side at a controlled velocity. The motor response was tested by tilting the seat to each side and recording the response to maintain the upright position. Both the trunk movement relative to the starting position and the end position of the trunk relative to the vertical were calculated. The sensory response was tested by tilting the seat to the side and asking the subject to indicate when the seat felt level as it returned slowly to the horizontal. Clinical data was collected on motor function and sensation of the leg, lateral trunk strength, lateral pelvic alignment, neglect, spatial deficits and apraxia. (Abstract shortened by UMI.)

A control group of normal readers and three subtypes of learning disability (LD) were compared in their visual event-related potentials (ERPs) to primed and unprimed words. The LD subtypes are characterized by deficient performance on tests of arithmetic skill (Group A), reading and spelling skills (Group RS), or both (Group RSA). The primed words were preceded by pictures or spoken words having a related meaning, while unprimed words were preceded by pictures or spoken words having a non-associated meaning. For normal readers, N400 amplitude was greater to unprimed words than to words primed by pictures and spoken words. For Group A, parietal N400 was reduced by spoken word primes, but not by picture primes. For Group RS and Group RSA, neither picture nor spoken word primes reduced N400 amplitude. These groups were differentiated by the amplitude of parietal N400. The normal readers displayed a greater left than right hemisphere frontal N400 amplitude to unprimed words. This asymmetry was absent in the ERPs of all the LD subtypes. The pattern of ERP results supports an LD typology that characterizes subtypes on the basis of difficulty with arithmetic or reading and spelling, or with a combination of both. The hemispheric asymmetry results suggest that left hemisphere dominance is associated with skilled reading.

Abstract not available.