Des évidences suggèrent que l’entraînement golfique améliore l’acuité proprioceptive et la stabilité posturale. Cependant, la proprioception du membre supérieur des golfeurs experts n’a jamais été évaluée. De plus, aucune étude ne s’est intéressée à la demande attentionnelle de la performance motrice des golfeurs élites. Nous avons comparé la performance de golfeurs élites à celle de non-athlètes sédentaires dans deux tâches motrices effectuées sans vision : une tâche d’atteintes manuelles vers des cibles proprioceptives situées dans l’espace tridimensionnel et une tâche de limites de la stabilité posturale dynamique. Ces tâches étaient effectuées isolément (tâche simple) ou simultanément à une tâche cognitive attentionnelle de soustraction mathématique (tâche double). La précision et la variabilité des atteintes manuelles étaient mesurées à l’aide d’un système d’analyse de mouvement. Les limites de la stabilité posturale étaient quantifiées à partir des déplacements des centres de pression obtenus à l’aide d’une plateforme de force. Nos résultats démontrent que les atteintes manuelles des golfeurs élites sont moins variables que ceux des sujets témoins uniquement dans la condition de tâche double. La performance cognitive des golfeurs est également meilleure que celles des sujets témoins en condition de tâche double. Par ailleurs, les limites médio-latérales de la stabilité posturale des golfeurs élites sont plus grandes que les non-athlètes et mobilisent, en moyenne, moins de ressources attentionnelles. Ensemble, ces résultats suggèrent que l’entraînement golfique augmente l’efficacité de contrôle proprioceptif des mouvements de bras et de la stabilité posturale et diminue les exigences attentionnelles de la performance motrice. / Evidence suggests that golf training improves proprioceptive acuity and postural stability. However, proprioceptive sensitivity at the upper limb has never been investigated in expert golfers. Furthermore, no previous study assessed the attentional demand of motor performance in elite golfers. We compared the performance of elite golfers to sedentary non-athletes in two motor tasks performed without vision: a task involving reaching movements to proprioceptive targets located in three-dimensional space and a dynamic postural stability limit task. These tasks were performed alone (single-task) and simultaneously to a cognitive-attentional subtraction task (dual-task). The accuracy and variability of reaching movements were measured using a motion analysis system. The limits of postural stability were quantified from center of pressure displacements recorded with a force platform. Our results demonstrated that reaching movements of elite golfers were less variable than those of control subjects only in the dual task condition. As well, the cognitive performance of elite golfers was better than those of non-athletes in the dual task condition. Moreover, the medio-lateral stability limits of elite golfers were larger than those of non-athletes and, on average, mobilized less attentional resources. Together, these results suggest that golf training increases the efficiency of the proprioceptive control of arm movements and postural stability and decreases the attentional demand of motor performance.

Previous research suggests that individuals with difficulty upregulating positive affect exhibit below-chance accuracy when identifying positive words presented outside of awareness, an effect termed subchance perception of positive information (SPPI). Previous findings also suggest that state orientation may underlie the relationship between clinical symptoms such as anxiety and anhedonia and SPPI. The current study addressed methodological limitations of previous research and tested hypotheses that state oriented individuals exhibit SPPI and that state orientation underlies the relationship between clinical symptoms and accuracy in identifying briefly-presented positive words. Results did not support hypotheses. The null findings in this study suggest that the relationship between action orientation and subchance perception of positive information may be less robust than preliminary findings suggested. Findings yielded from exploratory analyses suggested that future studies should include participants with greater symptom severity in order to have sufficient power to detect relationships between positive word accuracy and clinical symptoms.

Background: Evidence indicates that an external focus (EF) of attention on the intended effect of one’s movement results in better motor performance and motor control than an internal focus (IF) on one’s own body. Despite this, an IF is predominantly encouraged through instructions and feedback provided by clinicians during sports and rehabilitation from injuries such as anterior cruciate ligament (ACL) injury. Aim: The aim of this pilot study was to investigate the influence of EF and IF on motor control and performance on a bilateral leg extension and flexion task. The secondary aim was to investigate potential differences in the outcomes between a control group and a group with ACL reconstruction (ACLR). Method: Fourteen controls and four individuals with ACLR performed a bilateral leg extension and flexion task with instructions that encouraged either an IF, EF or neutral focus (NF) of attention. The instructions encouraged participants to either keep the individual tubes located on the footplates under the soles of the feet (EF) or the feet themselves (IF) level with each other. A three-dimensional motion capture system was used to record kinematics. Motor control was assessed based on the movement smoothness according to the knee angular velocity profile and performance was assessed based on the absolute mean deviation of the tubes/footplates from parallel. Results: For the control group, IF instructions resulted in significantly better motor control than EF instructions for left knee movement smoothness (p=0.02) and NF instructions resulted in significantly better motor control than EF on a majority of dependent variables. Conclusion: For our task, EF instructions did not result in better outcomes compared to IF instructions which might be explained because the task was proprioceptive demanding with less involvement of the vision. The reason for better motor control with NF instructions compared to EF instructions might be because of differences in angular velocity and instructions between conditions.

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The visual processing of a stimulus is facilitated by attention when it is at an attended location compared to an unattended location. However, whether attentional selection operates on the basis of visual features (e.g., color) independently of spatial locations is less clear. Six experiments were designed to examine how color information as well as location information affected attentional selection. In Experiment 1, the color of the targets and the spatial distance between them were both manipulated. Stimuli were found to be grouped based on color similarity. Additionally, the evidence suggested direct selection on the basis of color groups, rather than selection that was mediated by location. By varying the probabilities of target location and color, Experiments 2, 3 and 4 demonstrated that the use of color in perceptual grouping and in biasing the priority of selection is not automatic, but is modulated by task demands. Experiments 5 and 6 further investigated the relationship between using color and using location as the selection basis under exogenous and endogenous orienting. The results suggest that the precise nature of the interaction between color and location varies according to the mode of attentional control. Collectively, these experiments contribute to an understanding of how different types of information are used in selection and suggest a greater degree of flexibility of attentional control than previously expected. The flexibility is likely to be determined by a number of factors, including task demands and the nature of attentional control.

This dissertation aims to understand how attention can be used to improve sensory integration for postural control. Decades of research have been done using visual manipulations to study how healthy and clinical populations resolve multisensory (vision, vestibular, and somatosensory) mismatches to maintain postural stability. Postural control is a complex motor skill that requires accurate integration of multiple senses to maintain body alignment and orientation with respect to the environment. Age-related decline in visual, vestibular, and somatosensory acuity increases the risk for falls, and these sensory declines can be identified by assessing sensory reweighting. Sensory reweighting is the process in which the nervous redistributes the reliance, or "weight," on the sensory inputs to achieve postural stability. While the literature on sensory manipulation on postural control and fall risk has uncovered a wealth of knowledge on sensory reweighting for balance, it has neglected to identify how sensory reweighting can be improved. At the same time, motor learning literature has demonstrated the importance of focus attention during balance training to improve postural control. However, rudimentary analyses such as duration of balance and sway variability in this literature have limited deeper examination of the underlying neural mechanisms affected by focus of attention. This dissertation aims to bridge the gap between the two works of literature by implementing sensory manipulation techniques on posture using the latest technologies in virtual reality (VR) head-mount display (HMD) with motion capture and electroencephalography (EEG) recordings to study how different focuses of attention help resolve multisensory conflicts. In aim one, forty-two healthy adults participated in the study that used VR manipulation to induce a multisensory conflict. Participants were tasked to maintain upright stability on a rocker board while given different instructions on where to focus their attention. Instructions included focusing on keeping the rocker board leveled (external focus), focusing on keeping feet leveled to each other (internal focus), and focusing on staying as still as possible (control). This study revealed an immediate improvement in postural stability when instructed with external focus compared to control. This improvement was also associated with a significant decrease in visual weighting. Additionally, this aim revealed an immediate change in cortical activity within the frontal and occipital regions of the brain as identified by EEG recordings when participants are instructed to use external focus and internal focus. In aim two, twenty-eight healthy adults participated in the crossover study that demonstrated order effects when multiple instructions of attentional focus were given to the same participant for postural stability and visual reweighting. This study showed that the effects of external focus on postural stability and visual reweighting are greater when external focus is used before internal focus. However, the effects of external focus were nullified when used after using internal focus. Furthermore, the order of the instructions may have corresponded with a recency bias regarding how the participant perceived the effectiveness depending on when they received the attentional focus instruction. Guided by the findings from aims one and two, aim three recruited twenty-seven older adults to participate in a single-session balance training using repeated exposure to VR manipulation that challenged their balance on a rocker board. The older adults were randomized into one of the three groups: external focus, internal focus, and control group. The external focus group did not demonstrate an immediate reduction in visual weighting as found in aim 1. However, the external focus group did demonstrate better immediate postural stability when compared to the internal focus groups. Both external and internal focus groups revealed a significant improvement in visual weighting and postural stability across training blocks, suggesting a potential role of attentional focus on postural control adaption to repeated VR exposure. This dissertation was one of the first studies to investigate how the attentional focus impacts sensory reweighting and postural control in young and older adults using VR HMD. This project also established a VR experimental paradigm that can be used to study the focus of attention and the resolution of multisensory mismatch. With the increased use of VR for balance training and rehabilitation, this project is at the forefront of utilizing VR HMD technology to expose underlying sensory mechanisms for postural control. Results from this study can guide future rehabilitation and balance training interventions by identifying how attention should be directed during training. / Public Health

Deciding to use lethal force with a firearm is a critical decision that has major implications within society. In order to investigate racial bias in shooting decisions, the current dissertation uses the First-Person Shooter Task (FPST). Previous literature has shown that shooting decisions in this task are made faster and more often towards Black targets when compared to White targets. The relationship between this shooting bias and individual differences in cognitive ability is explored. The FPST was presented in three different conditions, each with trial proportions that varied in level of stereotype congruency (i.e., trials that are congruent with racial stereotypes). A Baseline condition presented an even distribution of Black Armed, Black Unarmed, White Armed, and White unarmed targets. A Mostly Congruent condition presented most (80%) of the Black targets as armed and most (80%) of the White targets as unarmed. A Mostly Incongruent condition presented most of the Black targets as unarmed and the White targets as mostly armed. Working memory, theoretically represented as a system of three separate components, was related to shooting behavior in these FPST conditions. The attentional control component of working memory was shown to be more related to shooting bias when compared to the capacity-related components, especially in the Mostly Incongruent condition (where most trials required making shooting decisions that go against racial stereotype). Study 2 used Confirmatory Factor Analysis to test whether attentional control ability was separate from proactive and reactive control strategy usage. Results showed that the attentional control ability was independent from which attentional control strategy was used. Finally, relating attentional control ability and attentional control strategies to shooting behavior, results showed that people with high attentional control and high proactive control usage were more likely to correctly adjust their expectations of threat in the Mostly Incongruent condition when compared to people with lower ability. People with low attentional control and high proactive control usage were more likely to adjust their expectations of threat based on racial stereotypes. Overall, these findings provide new insight into how cognitive ability interacts with shooting decisions in order to produce racial shooting bias.

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