The present series of experiments was designed to assess the utility of a discrimination procedure for measuring the affective properties of rewarding brain-stimulation. If the rewarding and discriminative stimulus properties of electrical brain stimulation were related, they may share a common substrate and be affected similarly by the same pharmacological manipulations. In Experiment 1, a discrimination procedure was developed to measure the cue properties of EBS delivered to the ventral tegmental area (VTA). Rats with VTA electrodes were trained to obtain food pellets by making a discriminated operant response on one of two levers following pulses of high intensity stimulation, or on the alternate lever after low intensity pulses. Following training, the rats were given tests in which generalized responding to intermediate intensities was measured. These tests were repeated either with conditions kept constant, or with the absolute intensities of the cues delivered within a sesion increased or decreased relative to baseline. The tests with higher or lower intensity ranges were intended to mimic the conditions that might prevail if the perceived intensities of the EBS were modified by drugs. The results of this experiment indicated that generalization gradients remained stable across three tests with conditions kept constant. When higher or lower current ranges were delivered, the discriminated responses were appropriately biased towards one lever or the other, resulting in lateral shifts in the generalization gradients. These results verified that the discrimination procedure provided a stable measure of the EBS stimulus properties, and that this measure was sensitive to changes in the intensities of the cues. In Experiment 2, tests for EBS generalization and self-stimulation (ICSS) were given after injections of vehicle, d-amphetamine (1.0 mg/kg and 2.0 mg/kg) and haloperidol (.075 mg/kg and .10 mg/kg). The results indicated that these doses of amphetamine and haloperidol did not affect the EBS generalization. However, during ICSS sessions, 2.0 mg/kg amphetamine decreased threshold and increased rates for ICSS whereas .10 mg/kg haloperidol resulted in an increase in threshold. These results suggest a dissociation of the stimulus properties of EBS from the DA reward substrate. In Experiment 3, the rats were tested for generalization after injections of physostigmine (.25 mg/kg and .50 mg/kg), scopolamine (.10 mg/kg and .25 mg/kg) and vehicle. Only the high dose of physostigmine (.50 mg/kg) produced significant differences in responding in this experiment. After injection of this drug, lower intensity stimuli elicited responding on the lever appropriate for the high current intensity, indicating a possible augmentation of the stimulus property of a fixed intensity of brain stimulation. The results of this study indicate that the cue properties of VTA brain-stimulation are dissociable from EBS reward related to the activation of DA neurons. However, evidence is provided which suggests that cholinergic neurons may be involved in the mediation of the EBS cues. In as much as cholinergic neurons are also involved in the rewarding effects of VTA brain-stimulation, these results may indicate a relationship between the cue properties of VTA EBS and an acetylcholine reward system. / Arts, Faculty of / Psychology, Department of / Graduate

M.A. (Psychology) / The Post Traumatic Amnesic Syndrome, which follows a mild closed head injury, seems to be a common occurrence in the field of neuropsychology. The syndrome is primarily characterised by a transient memory loss of daily events, normally commencing within days after the injury. The symptoms include absent-mindedness, an inability to remember names, dates, numbers and faces, commands and orders given at work. Due to the relatively uncomplicated nature of a mild closed head injury, the syndrome is often overlooked and underestimated in terms of its intensity and psychological damage. Patients are sent home after a brief observation period and medical staff are of the opinion that the patients will recover successfully, without experiencing much psychological or cognitive strain. It is usually thought that the syndrome does not last for more than three to four months. The aim of the research was to determine the nature of the experience of not being able to remember daily events, as part of the post traumatic amnesic syndrome. The influence of the syndrome on the patients' support persons was also investigated

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Atypical functional organization in the brains of adult male dyslexics was investigated through the divided visual field (DVF) paradigm. By intentional manipulation, equal levels of overall performance between groups were obtained, which made clearer interpretation of the results possible. Both dyslexic and control subjects appeared to have left hemisphere specialization for nonsense words. Dyslexics exhibited no asymmetry for face recognition indicating bilateral representation of this function in their brains, while control subjects exhibited the expected left visual field advantage. The results are considered both as group means and as frequency data. The results provide modest support tor the hypothesis that dyslexics have atypical functional organization. / Thesis / Master of Arts (MA)

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published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Biochemistry / Master / Master of Science

The elderly are a rapidly growing population in the United States and have the highest rate of TBI-related hospitalization. Across all levels of severity, elderly persons have uniformly poorer outcomes including quality of life, community integration, disability, and mortality, but there is a significant lack of published research regarding communication outcome in the elderly population. The likelihood that speech-language pathologists (SLPs) will clinically treat elderly clients with TBI is great; understanding the effects that age of injury has on communication may inform clinicians’ abilities to accurately and efficiently assess, diagnose, and treat the elderly. The present study examined the relationship between age of onset of injury and severity of communication deficits following traumatic brain injury (TBI); the study included a review of published research and a survey of SLP estimates of severity of impairment. Limitations of the study and directions for further research are discussed. / text