Arterial desaturation in fit athletes, during exercise at an intensity greater than or equal to 90% of VO₂ max has been reported by a number of authors yet the etiology of these changes remain obscure. Inadequate pulmonary ventilation due to a blunted respiratory drive, or lung mechanics has been implicated as a factor in the etiology of this phenomenon. It was the purpose of this experiment to investigate the relationship between arterial desaturation and ventilatory response to hypoxia (HVR). Twelve healthy male subjects ( age = 23.8 ± 3.6 yrs., height = 181.6 ±₋₁ 5.6 cms., Weight = 73.7 ± 6.2 kg., VO₂ max = 63.2 ± 2.2 ml .kg . -1 2 .min⁻¹) performed a five minute exercise test on a treadmill at 100% of VO₂ max. Arterial samples for pH, PCO₂, PO₂, and SaO₂ were withdrawn via an indwelling arterial cannula at rest and every 15s throughout the exercise test. The blood gas samples were analyzed with an Instrument Laboratories 1306 blood gas analyzer. Ventilation and VO₂ were measured by a Beckman metabolic measurement cart. On a separate occasion the ventilatory response to hypoxia (HVR) was determined by recording VE as progressive hypoxia was induced by adding N₂ to a mixing chamber. SaO₂ was measured using a Hewlett-Packard ear oximeter; to maintain isocapnia small ammounts of CO₂ were added to the open circuit system. ANOVA for repeated measured was used to evaluate changes in blood gases, ventilation, and VO₂. Simple linear regression and multiple linear regression was used to evaluate the relationship between the changes in SaO₂ and HVR and the descriptive variables. Subjects showed a significant decline in arterial saturation and PO₂ over the course of the test (p < 0.01,and p < 0.01). Four subjects (Mild) exhibited modest decreases in SaO₂ to (94.6 ± 1.9%), three (Moderate) showed an intermediate response (SaO₂ 91.6 ± 0.1%) and five (Marked) demonstrated a marked decrease in arterial saturation (SaO₂ = 90.0 + 1.2%). The differences in PO₂ and SaO₂ between Mild and Marked groups were significant ( p < 0.05, and p < 0.01); there were no significant differences between groups in VE, VO₂, pH or PCO . There was no significant correlation between the lowest SaO₂ reached and HVR, or any of the descriptive variables. Nine subjects did not reach maximal VE (as determined by the VO₂ max test) on the exercise test, two subjects 2 exhibited similar ventilation, and the remaining subject exceeded maximal VE, but fell into the Mild group with respect to desaturation. Oxygen uptake exceeded that recorded for the VO₂ max determination for four of the five subjects in the Marked group; the remaining subjects demonstrated lower or similar values. It was concluded that arterial desaturation was not related to blunted hypoxic drive. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

Recent studies have indicated stronger mood dependent memory (MDM) effects when subjects generate both the to-be-remembered events and the cues used in their retrieval, and when subjects who experience similar moods are compared to subjects who report a change in both pleasure and arousal, rather than others who report a change in pleasure alone. The first study was undertaken to experimentally evaluate the relationship between mood change and memory performance. Specifically, four mood manipulations were developed to compare memory performance in subjects assigned to no mood change, change in pleasure, change in arousal, or change in both pleasure and arousal. Subjects generated autobiographical events in response to neutral nouns, and were tested for free recall and recognition of these events two days later. Results demonstrated greater memory disruption after change in both pleasure and arousal than after change in pleasure alone. However, one-dimensional change in arousal led to as much memory disruption as did change in both dimensions. Separate ANOVAs compared each mood in combination with each other mood and indicated that MDM was more strongly supported in some combinations than others. Further, the pattern in free recall was different from the pattern in recognition indicating that MDM effects may vary interactively across moods and tasks. The second study was undertaken to validate prior research by employing subjects who experience large, but naturally occurring, changes in mood. Patients with rapid-cycling Bipolar Disorder performed a variety of tasks during study sessions and were tested for implicit and explicit memory during test sessions. Significant MDM effects were supported in free recall of autobiographical events and inkblot recognition, but not in implicit category production of autobiographical event probes, picture fragment completion, explicit nor implicit memory for letter associates. Results validate MDM as a real world phenomenon that impacts on explicit memory performance in subjects whose moods are not manipulated. Discussion centers on prospects for future studies that consider a wider range of manipulated moods and tasks, theories of emotion, and other clinical groups in the investigation of MDM. / Arts, Faculty of / Psychology, Department of / Graduate

Nine male Physical Education students were selected to test the hypothesis that addition of CO₂ to the inspired air during recovery will cause significant increases in ventilation above control conditions and that recovery from submaximal exercise will be enhanced by the addition of 2.78% or 5.80% CO₂ to room air. The exercise was administered for six minutes at a workload predetermined to elicit 75% of his maximal oxygen uptake. The dependent variables (heart rate, ventilation, oxygen uptake, and carbon dioxide elimination) were subjected to a one way analysis of variance and significant F ratios evaluated using Dunnett's Test. Ventilation is increased significantly (p<.05) above control values with the addition of 5.80% CO₂ to room air during recovery however, there is no significant increase in oxygen uptake. The addition of 2.78% CO₂ to room air during recovery does not significantly (p>.05) increase ventilation; there is however a significant (p<.05) increase in oxygen uptake in the first 30 seconds of recovery. Neither treatment effect causes significant changes in heart rate. The addition of 5.80% CO₂ to the inspired air significantly (p<.05) reduces carbon dioxide elimination. In 4 subjects, the effect produced a carbon dioxide uptake at certain time intervals. The addition of 2.78% CO₂ to the inspired air caused a significant (p<.05) reduction of carbon dioxide elimination in the first minute of recovery. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

M.Sc. (Botany) / Please refer to full text to view abstract

Language has been the subject of academic fascination for centuries, and the ability to communicate abstract notions through speech and writing allows humans to interact in ways that would not otherwise be possible. While the mechanisms of language processing have been studied extensively with behavioral and noninvasive neuroimaging methods, much about how the brain encodes language remains unknown. In this dissertation, I describe experiments using intracranial neurophysiology in humans to interrogate the mechanisms of language perception at high spatiotemporal resolution. First, I explore the neural mechanisms of visual word recognition in a large human intracranial dataset. By analyzing population sensitivity to a hierarchy of word features, I create a high-resolution map of stimulus encoding during single-word reading that reveals the early influence of lexical features in lingual and fusiform gyri followed by a cascade of lexical, orthographic, and semantic information in temporal and frontal lobes. Along with clustering analyses that show stimulus encoding in anatomically distributed populations, these results demonstrate that feed-forward, feed-back, and distributed processing mechanisms underlie visual word recognition. Second, I describe the development of an artificial language task designed to characterize the neural mechanisms of auditory word segmentation. The task is designed in three phases to probe how the brain tracks distributional regularity and the neural mechanisms of word segmentation with and without lexical access. Taken together, this work expands our understanding of the neural mechanisms of language processing using human intracranial neurophysiology.

In the clinical evaluation and management of speech disorders, a speech-language pathologist may observe disturbances in a client's motor abilities that suggest possible neurological dysfunction. One possible disturbance is in oral diadochokinesis (DIO), an individual's ability to start and stop the movement of the articulators rapidly and execute repetitive, alternating, sequential movements typically associated with speech articulation. It is often recommended that a speech-language pathologist test DIO speed and compare the performance to available norms. There is, however, a lack of normative DIO data spanning all ages of adulthood. The purpose of this study was to develop preliminary normative data on the speed of oral diadochokinesis used in articulation of syllables and oral movements by adults. The investigation sought to answer the question: What are the mean rates of oral diadochokinetic syllable productions and selected oral movements for each decade of adulthood?

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