Cortical and autonomic modulation of attentional control /

Whereas the role of the anterior cingulate cortex (ACC) in cognitive control has received considerable attention, much less work has been done on the role of the ACC in autonomic regulation. Its connections through the vagus nerve to the sinoatrial node of the heart are thought to exert modulatory control over cardiovascular arousal. Therefore, ACC is not only responsible for the implementation of cognitive control, but also for the dynamic regulation of cardiovascular activity that characterizes healthy heart rate and adaptive behaviour. However, cognitive control and autonomic regulation are rarely examined together. Moreover, those studies that have examined the role of phasic vagal cardiac control in conjunction with cognitive performance have produced mixed results, finding relations for specific age groups and types of tasks but not consistently. So, while autonomic regulatory control appears to support effective cognitive performance under some conditions, it is not presently clear just what factors contribute to these relations. The goal of the present study was, therefore, to examine the relations between autonomic arousal, neural responsivity, and cognitive performance in the context of a task that required ACC support. Participants completed a primary inhibitory control task with a working memory load embedded. Pre-test cardiovascular measures were obtained, and ontask ERPs associated with response control (N2/P3) and error-related processes (ERN/Pe) were analyzed. Results indicated that response inhibition was unrelated to phasic vagal cardiac control, as indexed by respiratory sinus arrhythmia (RSA). However, higher resting RSA was associated with larger ERN ampUtude for the highest working memory load condition. This finding suggests that those individuals with greater autonomic regulatory control exhibited more robust ACC error-related responses on the most challenging task condition. On the other hand, exploratory analyses with rate pressure product (RPP), a measure of sympathetic arousal, indicated that higher pre-test RPP (i.e., more sympathetic influence) was associated with more errors on "catch" NoGo trials, i.e., NoGo trials that simultaneously followed other NoGo trials, and consequently, reqviired enhanced response control. Higher pre-test RPP was also associated with smaller amplitude ERNs for all three working memory loads and smaller ampUtude P3s for the low and medium working memory load conditions. Thus, higher pretest sympathetic arousal was associated with poorer performance on more demanding "catch" NoGo trials and less robust ACC-related electrocortical responses. The findings firom the present study highlight tiie interdependence of electrocortical and cardiovascular processes. While higher pre-test parasympathetic control seemed to relate to more robust ACC error-related responses, higher pre-test sympathetic arousal resulted in poorer inhibitory control performance and smaller ACC-generated electrocortical responses. Furthermore, these results provide a base from which to explore the relation between ACC and neuro/cardiac responses in older adults who may display greater variance due to the vulnerabihty of these systems to the normal aging process.

The capillary supply of human skeletal muscle in health and disease

BACKGROUND: Capillaries function to provide a surface area for nutrient and waste exchange with cells. The capillary supply of skeletal muscle is highly organized, and therefore, represents an excellent choice to study factors regulating diffusion. Muscle is comprised of three specific fibre types, each with specific contractile and metabolic characteristics, which influence the capillary supply of a given muscle; in addition, both environmental and genetic factors influence the capillary supply, including aging, physical training, and various disease processes. OBJECTIVE: The present study was undertaken to develop and assess the functionality of a data base, from which virtual experiments can be conducted on the capillary supply of human muscle, and the adaptations of the capillary bed in muscle to various perturbations. METHODS: To create the database, an extensive search of the literature was conducted using various search engines, and the three key words - "capillary, muscle, and human". This search yielded 169 papers from which the data for the 46 variables on the capillary supply and fibre characteristics of muscle were extracted for inclusion in the database. A series of statistical analyses (ANOVA) were done on the capillary database to examine differences in skeletal muscle capillarization and fibre characteristics between young and old individuals, between healthy and diseased individuals, and between untrained, endurance trained, endurance welltrained, and resistance trained individuals, using SAS. RESULTS: There was a significantly higher capillarization in the young compared to the old individuals, in the healthy compared to the diseased individuals, and in the endurance-trained and endurance well-trained compared to the untrained individuals. CONCLUSIONS: The results of this study support the conclusion that the capillary supply of skeletal muscle is closely regulated by factors aimed at optimizing oxygen and nutrient supply and/or waste removal in response to changes in muscle mass and/or metabolic activity.

Aging policy: a case study of co-ordination in Canadian governments

ABSTRACT Canada is an aging society. The number of people aged sixty-five and over is rising, while the number of people under twenty is declining. These two concurrent changes in the age structure have produced a sh~ft in the demographic composition of Canada which is commonly referred to as the aging phenomenon. Regardless of whether or not the number of people under twenty continues to decline, the number of elderly in Canada will almost double over the next twenty years. This rapidly growing elderly clientele will doubtless have an impact on Canadian governments. Federal, provincial and municipal governments are presently providing a variety of programs that have a special bearing on the aged and most senior citizens are beneficiaries of one or more of these programs. The ramifications of a rapidly growing elderly clientele are obvious. In order to cope with the impact of a significant increase in the number of elderly persons, the development and implementation of aging policy must be co-ordinated at each level of government and between and among levels of government. If aging policy is not co-ordinated, the results are likely to be: inappropriate policy decisions; duplication and overlap; and, ineffective and irresponsive services. No one benefits from these results. The need for co-ordination is apparent. The purpose of this thesis is to examine existing governmental efforts to co-ordinate policy in the field of aging. These efforts are examined by focusing on interactions directed at co-ordination between and among major actors in aging policy. A framework is used to structure the description and analysis of these interactions. The variables of formalisation and intensity and the concept of power are instrumental in analysing interactions for co-ordination. The underlying intent of this thesis is to discover some of the main gaps in existing governmental efforts to co~ordinate aging policy. Gaps are, in fact, discovered. Several explanations for the existence of gaps in interactions for co-ordination are discussed. A major hypothesis involving a relationship between a bureaucratic form of organisation and interactions for coordination is suggested. Finally, three recommendations for improving co-ordination in aging policy are offered.

Vitamin D status and latent tuberculosis infection : a preliminary study in a group of healthy Mexican agricultural workers

Vitamin D metabolites are important in the regulation of bone and calcium homeostasis, but also have a more ubiquitous role in the regulation of cell differentiation and immune function. Severely low circulating 25-dihydroxyvitamin D [25(OH)D] concentrations have been associated with the onset of active tuberculosis (TB) in immigrant populations, although the association with latent TB infection (LTBI) has not received much attention. A previous study identified the prevalence of LTBI among a sample of Mexican migrant workers enrolled in Canada's Seasonal Agricultural Workers Program (SA WP) in the Niagara Region of Ontario. The aim of the present study was to determine the vitamin D status of the same sample, and identify if a relationship existed with LTBI. Studies of vitamin D deficiency and active TB are most commonly carried out among immigrant populations to non-endemic regions, in which reactivation of LTBI has occurred. Currently, there is limited knowledge of the association between vitamin D deficiency and LTBI. Entry into Canada ensured that these individuals did not have active TB, and L TBI status was established previously by an interferon-gamma release assay (IGRA) (QuantiFERON-TB Gold In-Tube®, Cellestis Ltd., Australia). Awareness of vitamin D status may enable individuals at risk of deficiency to improve their nutritional health, and those with LTBI to be aware of this risk factor for disease. Prevalence of vitamin D insufficiency among the Mexican migrant workers was determined from serum samples collected in the summer of 2007 as part of the cross sectional LTBI study. Samples were measured for concentrations of the main circulating vitamin D metabolite, 25(OH)D, with a widely used 1251 250HD RIA (DiaSorin Inc.®, Stillwater, MN), and were categorized as deficient «37.5 nmoI/L), insufficient (>37.5 nmollL, < 80 nmol/L) or sufficient (2::80 nmoI/L). Fisher's exact tests and t tests were used to determine if vitamin D status (sufficiency or insufficiency) or 25(OH)D concentrations significantly differed by sex or age categories. Predictors of vitamin D insufficiency and 25(OH)D concentrations were taken from questionnaires carried out during the previous study, and analyzed in the present study using multiple regression prediction models. Fisher's exact test and t test was used to determine if vitamin D status or 25(OH)D concentration differed by LTBI status. Strength of the relationship between interferongamma (IFN-y) concentration (released by peripheral T cells in response to TB antigens) and 25(OH)D concentration was analyzed using a Spearman correlation. Out of 87 participants included in the study (78% male; mean age 38 years), 14 were identified as LTBI positive but none had any signs or symptoms of TB reactivation. Only 30% of the participants were vitamin D sufficient, whereas 68% were insufficient and 2% were deficient. Significant independent predictors of lower 25(OH)D concentrations were sex, number of years enrolled in the SA WP and length of stay in Canada. No significant differences were found between 25(OH)D concentrations and LTBI status. There was a significant moderate correlation between IFN-y and 25(OH)D concentrations ofLTBI-positive individuals. The majority of participants presented with Vitamin D insufficiency but none were severely deficient, indicating that 25(OH)D concentrations do not decrease dramatically in populations who temporarily reside in Canada but go back to their countries of origin during the Canadian winter. This study did not find a statistical relationship between low levels of vitamin D and LTBI which suggests that in the presence of overall good health, lower than ideal levels of 2S(OH)D, may still be exerting a protective immunological effect against LTBI reactivation. The challenge remains to determine a critical 2S(OH)D concentration at which reactivation is more likely to occur.

The Structural and Functional Changes of Blood Vessels during Aging

The vascular adventitia is recognized as a dynamic mediator of vascular structure and function, yet its role in aging is not understood. The purpose of this thesis was to examine the age-related changes of the vascular adventitia and determine the underlying mediators responsible. Male Sprague-Dawley rats were aged to 15, 30, 50 and 80 weeks before being anesthetised and euthanized by exsanguination. Thoracic aortas, mesenteric and pudental arteries were isolated, formalin fixed, and embedded in paraffin then sectioned at 5μm. Vessels were examined by microscopy and protein expression was determined by indirect immunofluorescence. The thickness of the adventitia increased dramatically with age. Immunofluorescence revealed a robust expression of endothelin system proteins in the adventitia. Additionally, extracellular matrix proteins collagen and fibronectin, and the proliferation marker Ki67 showed strong adventitial origin. The changes observed in the vascular adventitia with aging clearly demonstrate an important role in the process of vascular aging.

Electrocortical indices of cognitive control in working memory : exploring the effects of proactive interference, cognitive load, and aging

Cognitive control involves the ability to flexibly adjust cognitive processing in order to resist interference and promote goal-directed behaviour. Although frontal cortex is considered to be broadly involved in cognitive control, the mechanisms by which frontal brain areas implement control functions are unclear. Furthermore, aging is associated with reductions in the ability to implement control functions and questions remain as to whether unique cortical responses serve a compensatory role in maintaining maximal performance in later years. Described here are three studies in which electrophysiological data were recorded while participants performed modified versions of the standard Sternberg task. The goal was to determine how top-down control is implemented in younger adults and altered in aging. In study I, the effects of frequent stimulus repetition on the interference-related N450 were investigated in a Sternberg task with a small stimulus set (requiring extensive stimulus resampling) and a task with a large stimulus set (requiring no stimulus resampling).The data indicated that constant stimulus res amp ling required by employing small stimulus sets can undercut the effect of proactive interference on the N450. In study 2, younger and older adults were tested in a standard version of the Sternberg task to determine whether the unique frontal positivity, previously shown to predict memory impairment in older adults during a proactive interference task, would be associated with the improved performance when memory recognition could be aided by unambiguous stimulus familiarity. Here, results indicated that the frontal positivity was associated with poorer memory performance, replicating the effect observed in a more cognitively demanding task, and showing that stimulus familiarity does not mediate compensatory cortical activations in older adults. Although the frontal positivity could be interpreted to reflect maladaptive cortical activation, it may also reflect attempts at compensation that fail to fully ameliorate agerelated decline. Furthermore, the frontal positivity may be the result of older adults' reliance on late occurring, controlled processing in contrast to younger adults' ability to identify stimuli at very early stages of processing. In the final study, working memory load was manipulated in the proactive interference Sternberg task in order to investigate whether the N450 reflects simple interference detection, with little need for cognitive resources, or an active conflict resolution mechanism that requires executive resources to implement. Independent component analysis was used to isolate the effect of interference revealing that the canonical N450 was based on two dissociable cognitive control mechanisms: a left frontal negativity that reflects active interference resolution, , but requires executive resources to implement, and a right frontal negativity that reflects global response inhibition that can be relied on when executive resources are minimal but at the cost of a slowed response. Collectively, these studies advance understanding of the factors that influence younger and older adults' ability to satisfy goal-directed behavioural requirements in the face of interference and the effects of age-related cognitive decline.

The structural and functional changes of blood vessels during aging

The vascular adventitia is recognized as a dynamic mediator of vascular structure and function, yet its role in aging is not understood. The purpose of this thesis was to examine the age-related changes of the vascular adventitia and determine the underlying mediators responsible. Male Sprague-Dawley rats were aged to 15,30,50 and 80 weeks before being anesthetised and euthanized by exsanguination. Thoracic aortas, mesenteric and pudental arteries were isolated, formalin fixed, and embedded in paraffin then sectioned at 51lm. Vessels were examined by microscopy and protein expression was determined by indirect immunofluorescence. The thickness of the adventitia increased dramatically with age. Immunofluorescence revealed a robust expression of endothelin system proteins in the adventitia. Additionally, extracellular matrix proteins collagen and fibronectin, and the proliferation marker Ki67 showed strong adventitial origin. The changes observed in the vascular adventitia with aging clearly demonstrate an important role in the process of vascular aging.

Empowering Nursing Leaders to Facilitate Healthy Work Environments: First Steps

The purpose of this project was to examine the literature for perspectives on healthy work environments (HWE). HWEs have been identified as important factors in the nursing profession to enhance recruitment, retention, job satisfaction, and accountability. This paper identifies that the front line manager is an essential role within organizations, and directly impacts work environments. Within this paper it has been pointed out that professional organizations have provided some general recommendations for improving work environments which include increasing nurses’ accountability and teamwork, providing opportunities for shared decision making, having supportive leadership, providing recognition, educational support, and adequate staffing. However, enacting them all can be difficult due to front line manager capacity, the impending nursing shortage, organizational resources and barriers. Based on the literature, conclusions have been drawn and recommendations for future research have been identified. HWE strategies have been developed with implementation plans for my practice area.

Autonomic and Electrophysiological Correlates of Cognitive Control in Aging

This thesis tested a model of neurovisceral integration (Thayer & Lane, 2001) wherein parasympathetic autonomic regulation is considered to play a central role in cognitive control. We asked whether respiratory sinus arrhythmia (RSA), a parasympathetic index, and cardiac workload (rate pressure product, RPP) would influence cognition and whether this would change with age. Cognitive control was measured behaviourally and electrophysiologically through the error-related negativity (ERN) and error positivity (Pe). The ERN and Pe are thought to be generated by the anterior cingulate cortex (ACC), a region involved in regulating cognitive and autonomic control and susceptible to age-related change. In Study 1, older and younger adults completed a working memory Go/NoGo task. Although RSA did not relate to performance, higher pre-task RPP was associated with poorer NoGo performance among older adults. Relations between ERN/Pe and accuracy were indirect and more evident in younger adults. Thus, Study 1 supported the link between cognition and autonomic activity, specifically, cardiac workload in older adults. In Study 2, we included younger adults and manipulated a Stroop task to clarify conditions under which associations between RSA and performance will likely emerge. We varied task parameters to allow for proactive versus reactive strategies, and motivation was increased via financial incentive. Pre-task RSA predicted accuracy when response contingencies required maintenance of a specific item in memory. Thus, RSA was most relevant when performance required proactive control, a metabolically costly strategy that would presumably be more reliant on autonomic flexibility. In Study 3, we included older adults and examined RSA and proactive control in an additive factors framework. We maintained the incentive and measured fitness. Higher pre-task RSA among older adults was associated with greater accuracy when proactive control was needed most. Conversely, performance of young women was consistently associated with fitness. Relations between ERN/Pe and accuracy were modest; however, isolating ACC activity via independent component analysis allowed for more associations with accuracy to emerge in younger adults. Thus, performance in both groups appeared to be differentially dependent on RSA and ACC activation. Altogether, these data are consistent with a neurovisceral integration model in the context of cognitive control.