The Distal-less (Dll) gene has an ancient evolutionary origin. Chordates have retained duplicated Dll genes; vertebrates have six distinct paralogues (Dlx1 through Dlx6 in mammals) arranged in three cis-linked pairs that are co-expressed. Dlx genes are expressed in a conserved nested pattern that defines a proximal-distal axis in the pharyngeal arch tissue of vertebrates. Dlx5-/- and Dlx6-/- mouse neonates have similar phenotypic variations in the lower jaw and inner ear bones, with the Dlx6-/- phenotype being a less perturbed version of the Dlx5-/- phenotype. Conversely, Dlx5/6-/- double mutants have a homeotic transformation of the lower jaw into a second set of maxillary structures. The combination of expression patterns and null phenotypes has led to the proposal of a “Dlx code” that patterns the craniofacial tissue. However, the nature of this code, whether individual Dlx transcription factors supply unique functions, or whether they make a quantitative contribution to a more generic and shared Dlx function, is not well understood. One prediction of a quantitative model for Dlx function in the pharyngeal arches is the functional equivalency of the proteins encoded by divergent cis-linked Dlx paralogues. To address this aspect of the model, three core functions of Dlx5 and Dlx6 were compared quantitatively: suppression of cell growth, transcription activity and DNA binding affinity. In most respects both proteins behaved very similarly.

Investigating the Neural Correlates of Crossmodal Facilitation as a Result of Attentional Cueing: An Event-Related fMRI Study. Degree of Masters of Science, 2008 Zainab Fatima Institute of Medical Science, University of Toronto ABSTRACT Attentional cueing modulated neural processes differently depending on input modality. I used event-related fMRI to investigate how auditory and visual cues affected reaction times to auditory and visual targets. Behavioural results showed that responses were faster when: cues appeared first compared to targets and cues were auditory versus visual. The first result was supported by an increase in BOLD percent signal change in sensory cortices upon cue but not target presentation. Task-related activation patterns showed that the auditory cue activated auditory and visual cortices while the visual cue activated the visual cortices and the fronto-polar cortex. Next, I computed brain-behaviour correlations for both cue types which revealed that the auditory cue recruited medial visual areas and a fronto-parietal attentional network to mediate behaviour while the visual cue engaged a posterior network composed of lateral visual areas and subcortical structures. The results suggest that crossmodal facilitation occurs via independent neural pathways depending on cue modality.

It is often difficult for people to understand speech when there are other ongoing conversations in the background. This dissertation investigates how different background maskers interfere with our ability to comprehend speech and the reasons why older listeners have more difficulties than younger listeners in these tasks. An ecologically valid approach was applied: instead of words or short sentences, participants were presented with two fairly lengthy lectures simultaneously, and their task was to listen to the target lecture, and ignore the competing one. Afterwards, they answered questions regarding the target lecture. Experiment 1 found that both normal-hearing and hearing-impaired older adults performed poorer than younger adults when everyone was tested in identical listening situations. However, when the listening situation was individually adjusted to compensate for age-related differences in the ability to recognize individual words in noise, age-related difference in comprehension disappeared. Experiment 2 compared the masking effects of a single-talker competing lecture to a babble of 12 voices, and the signal-to-noise ratio (SNR) was manipulated so that the masker was either of similar volume as the target, or much louder. The results showed that the competing speech was much more distracting than babble. Moreover, increasing the masker level negatively affected speech comprehension only when the masker was babble; when it was a single-talker lecture, the performance plateaued as the SNR decreased from -2 to -12 dB. Experiment 3 compared the effects of semantic content and acoustic similarity on speech comprehension by comparing a normal speech masker with a time-reversed one (to examine the effect of semantic content) and a normal speech masker with an 8-band vocoded speech (to examine the effect of acoustic similarity). The results showed that both semantic content and acoustic similarity contributed to informational masking, but the latter seemed to play a bigger role than the former. Together, the results indicated that older adults’ speech comprehension difficulties with maskers were mainly due to declines in their hearing capacities rather than their cognitive functions. The acoustic similarity between the target and competing speech may be the main reason for informational masking, with semantic interference playing a secondary role.

Children with alcohol-related neurodevelopmental disorder or attention deficit/hyperactivity disorder differ on neuropsychological tasks and measures of eye movement control. M.Sc. Thesis, Queen’s University, Kingston, Ontario, Canada, January 2010. Background: Alcohol-related neurodevelopmental disorder (ARND) accounts for the majority of diagnoses associated with prenatal alcohol exposure. Unfortunately, ARND frequently poses a significant clinical challenge as these patients lack the visible physical characteristics associated with alcohol teratogenicity. Moreover, the cognitive and behavioural disabilities are complex and overlap with those of attention deficit/hyperactivity disorder (ADHD). Furthermore, co-morbid ADHD is prevalent in children with prenatal alcohol exposure. While early and accurate diagnosis provides the best prognosis for those affected, there is a lack of tools for differential diagnosis between these two disorders. The goal of this study was to test the hypothesis that children with ARND exhibit different performance from children with ADHD on computer-based neuropsychological tests and eye movement tasks. Methods: Our study group was composed of 42 children with ARND and 31 children with ADHD aged 8-15 years, male and female. Children completed four tasks selected from the Cambridge Neuropsychological Test Automated Battery (CANTAB®) that provided measures of attention, planning, strategy and spatial working memory. Subjects also performed pro- and anti-saccade tasks, and eye movements were recorded using a mobile eye-tracking system. Results: Children with ARND demonstrated elevated decision times on a visual matching test of attention and longer response times on a task of spatial working memory, although the two groups had similar errors scores. Also, compared to children with ADHD, children with ARND had greater anticipatory errors in both the pro- and anti-saccade tasks. Conclusion: This study demonstrates that there are measurable differences in executive function and eye movement control between children with ARND or ADHD. Greater deficits in visuospatial processing in ARND may underlie these differences. These findings demonstrate that the neurobehavioural phenotypes of children with ARND or ADHD have distinct features, which may be accounted for by differences in the patterns of brain injury underlying these two disorders. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2010-01-15 15:15:47.738

Two Paleoproterozoic basins, the western Thelon Basin, and the Otish Basin, Canada, were investigated using basin analysis to evaluate critical factors for the formation of unconformity-related uranium deposits. The results serve to guide ongoing exploration at two under-studied uranium prospects in each basin, and help predict whether or not these basins have the potential to host high-grade uranium deposits in other locations. Sequence stratigraphy, in combination with mineral paragenesis indicates that unmetamorphosed basinal sandstones overlying the Boomerang Lake prospect, western Thelon Basin, were compacted and occluded by kaolinite and muscovite during diagenesis, and became diagenetic aquicludes that were unable to effectively conduct uranium-bearing basinal brines. Based on the high δ18O values of basinal and basement-influenced fluids, and the preservation of pre-Thelon-Basin 40Ar/39Ar dates of poorly-crystalline phyllosilicates in the basement rocks, hydrothermal alteration and uranium mineralization must have occurred at low water/rock ratios. This produced uneconomic amounts of U-bearing phosphate that was misidentified as uraninite in a previous report. A significant uranium deposit is unprobable based on the lack of unsupported radiogenic Pb near the prospect. However, intersections of thick, stratigraphically-higher diagenetic aquifers, which are marked by abundant dickite, and structurally-reactivated basement rocks on a different exploration trend remain the most prospective locations for a uranium deposit in the area. At the Camie River prospect, Otish Basin, diagenesis of basinal sediments in thick diagenetic aquifers was associated with fluids that were isotopically similar to seawater-derived basinal brines. The 1721 ±20 Ma Pb/Pb date obtained for Camie River uraninite coincides with intrusions of the Otish Gabbro, which triggered basinal fluid flow in diagenetic aquifers and uranium mineralization throughout the basin. The effects of late hydrothermal, metamorphic, and meteoric fluid events are restricted to fractures and faults. These zones also preferentially host radiogenic Pb and pathfinder elements that dispersed from the prospect, which can be utilized to vector towards additional deposits. The unconformity-type deposit model can be extended to basins as old as 2.0 Ga, as the Otish Basin demonstrates that atmospheric oxygen contents were high enough at this time to allow the evolution of U-leaching oxidizing basinal brines. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2011-01-29 15:45:53.651

No description available.

No description available.

No description available.

No description available.

Dissertation submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, 2010. / Background: Professional orchestral string musicians are exposed to many physical and psychological stressors due to demands placed on them from playing their instruments. The prevalence of performance-related musculoskeletal disorders (PRMD’s) in this highly skilled group of individuals has been investigated internationally, consistently showing a high injury rate. There is however, a paucity of literature documenting the prevalence of musculoskeletal injuries in South African professional orchestral string players. It is hypothesized that South African trained orchestral string musicians may be at a greater risk for PRMD development due to the unique training and performance environments encountered in this country. Objectives: This study aimed to determine the demographic and injury profile; prevalence rate of current injury and risk factors for musculoskeletal injury in South African professional orchestral string musicians. Method: The study utilized a self administered quantitative questionnaire distributed to all string players in the three professional orchestras in South African in a semi-supervised fashion. SPSS version 15.0 (SPSS Inc., Chicago, Illinois, USA) was used to analyze the data. A p value < 0.05 was considered as statistically significant. iv v Results: There were 27 respondents, with the average participant being a Caucasian, right handed, non-smoking female, 37.11 years of age, 1.5631 meters tall, with a weight of 62.96 kilograms (BMI = 25.768) who exercised regularly (primarily in the gym). A bachelors degree in Music was the most commonly awarded qualification, obtained between the years 2000 and 2009, from a University outside of the Republic of South Africa. The prevalence of PRMD’s in the sample was 63% (n = 17), with a 95% confidence interval of 42.4% to 80.6%.In this study there was a high rate of injury (6.53 PRMD’s per player over a 12 month period), equating to 111 reported injuries in a population of 27 string players. The upper back (defined as the area between the shoulder blades) was the most commonly injured part of the body (77.8%, n = 21), followed by the upper extremity, mainly the shoulder (70.4%, n = 19). No statistically significant relationships were found in determining and confirming expected risk factors in the string players. Conclusion: Professional orchestral string musicians in South Africa suffer from a high rate of injury which is comparable to international studies of the same nature