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Concussion is a life-altering injury that can affect people of all ages. Event-related potentials (ERPs) extracted from electroencephalography (EEG) have proven sensitive to concussion-induced cognitive deficits. The MMN, P3a, P3b, and N2b are some ERP components of interest, assessing automatic attention, attentional resource allocation, working memory, and inhibitory executive function, respectively. These ERPs can assess some common symptoms associated with concussion at a level that cannot be attained using self-report. A reduced amplitude and potentially delayed latency of the P3a and P3b is a well-replicated result in concussion research. Furthermore, recent research suggests that an alteration in amplitude of earlier peaks such as the N2b and MMN might represent an irreversible change in cognitive processing that tends to occur in the chronic stages of concussion. Many of these studies have focused on athletes, however little research has evaluated the cognitive effects of sustaining numerous blows to the head that do not result in a clinical diagnosis of concussion, as is the case for many athletes in contact sports. These blows are often referred to as subconcussive impacts. The present study examined the cognitive and neurophysiological effects of subconcussive impacts on collegiate contact-sport athletes and compared them to noncontact athletes. The athletes completed questionnaires to evaluate their health and athletic history, as well as estimates of exposure to subconcussive impacts such as position and playing time, prior to participating in three paradigms meant to assess various cognitive processes during an EEG recording. Across two experiments we demonstrated that subconcussive impacts within a season of play can result in alterations in neurophysiological markers of cognitive health. Our findings also reveal that continued involvement in contact sports can have serious implications in one’s automatic attention, resource allocation, and working memory as demonstrated by reduced ERP amplitudes in contact as compared to non-contact athletes. / Thesis / Master of Science (MSc) / A concussion is a devastating injury that can greatly affect how an individual functions in their day-to-day life. Concussions are often discussed in the context of contact sports because of these athletes’ exposure to repeated head impacts. That said, another cause for concern is the effects of head impacts that do not result in a concussion per se – these are known as subconcussive impacts. A brain imaging technique known as electroencephalography (EEG) involves recording brain activity from sensors on the head. Conducting this recording while individuals perform tasks known to evaluate brain function offers an opportunity to assess symptoms rather than relying on a patient’s own, subjective report of their experiences. The present study investigated the use of EEG in evaluating the effects of subconcussive impacts in collegiate athletes and found that repeated head impacts can reduce cognitive health, even if they do not result in a diagnosis of concussion.

The current set of studies adds to the growing body of literature of self-perceptions in atypical populations. Previous research has demonstrated that, despite significant functional problems in multiple domains, children with ADHD unexpectedly provide overly-positive reports of their own competence in comparison to actual performance on objective measures. Study 1 empirically examined the self-perceptions of adolescents with Attention-Deficit/Hyperactivity Disorder (ADHD) using performance on individual, specific, concrete tasks as the basis for participants’ ratings of competence. Participants completed a verbal and mathematic task and were asked how well they thought they did prior to completing the tasks (pre-prediction rating). After they completed each task they were asked how well they thought they did (current post-performance) and how well they thought they would do in the future (future post-performance). For the purpose of the study, self-perceptions can be described as the difference between perceived performance and actual performance. These difference scores were used in analyses. Results suggested that adolescents with ADHD tend to have more positively-biased self-perceptions than typically developing (TD) adolescents. The current study also examined the role that IQ and executive functioning have on self-perceptions; however, no significant relationships were found. Using the same methodology, Study 2 examined the self-perceptions of adolescents with Autism Spectrum Disorders (ASD). By examining a population with similar cognitive deficits as individuals with ADHD, the current study aimed to determine whether these positively-biased self-perceptions are specific to ADHD or if it is a phenomenon related to more general difficulties or dysfunction. Results suggested that adolescents with ASD also tended to have more positively-biased self-perceptions than TD adolescents. In adolescents with ASD, lower IQ and greater executive functioning deficits tended to be related to more positively-biased self-perceptions. Limitations of this research are discussed. Future investigation is needed to systematically examine other possible mechanisms that may be contributing to these biased self-perceptions. / Thesis (Master, Psychology) -- Queen's University, 2013-09-30 15:24:30.91

Hypohydration and fasting are used as means to achieve body mass loss and Ramadan fasting is practised by millions of Muslims as a religious custom. Although both hypohydration and fasting have been studied extensively, the effect of hypohydration and Ramadan style fasting on many aspects of human performance is still unclear. In Chapter 3, the effect of exercise-induced hypohydration on muscle performance was evaluated. The protocol was developed to eliminate masking and exacerbating factors such as changes in muscle glycogen storage, muscle temperature, fatigue and fluid distribution change and acid base status. Muscle strength and endurance decreased due to hypohydration equivalent to 2% of body mass. This suggests that hydration status itself can affect adversely athletes' performance. In Chapter 4, the effect of one day (11 h) of Ramadan style fasting on some aspects of exercise performance during the day was investigated. Participants were tested three times throughout the day: at 7:00 am, 12:00 noon and 7:00 pm. 11 h of Ramadan style fasting decreased body mass by 2.1%. No change was found in exercise performance measurements. The results of this study suggest that this short period of fasting has no measurable effects on performance and/or that any effects are compensated by the circadian rhythm throughout the day. However, most athletes use more intense fasting or several consecutive days of fasting to achieve their weight reduction goal. In Chapter 5, the effect of Ramadan fasting (one month long intermittent fasting) on some aspects of exercise performance of athletes (weight category and non-weight category sports) and recreationally active individuals was studied. Participants were tested before, during (after the first week and in the last week) and after the month of Ramadan. Ramadan style living (involving a change in timing of food intake and sleep pattern) affects most of the anthropometric and physical performance parameters of the athletes and of the recreationally active subjects, with no difference in the pattern of change between groups. Almost all of the differences were recovered a week after the end of fasting. Chapter 6 contains the results of three studies focused on the effects of fasting on cognitive function (study A- breakfast elimination; study B- one day (11 h) of Ramadan style fasting; and study C- one month of Ramadan fasting). Results of these studies make a logical conclusion that fasting has a detrimental effect on memory, reaction time and accuracy of responses. The pattern of the effects showed differences that may be related to various participants' characteristics (age group, gender) and the nature of intervention. In summary, Ramadan style fasting may affect performance of some mental and physical tasks in some, but perhaps not in all individuals.

Hypoglycaemia is a very common side-effect of insulin therapy for diabetes and directly affects cognitive function. It can be identified by the onset of symptoms and by blood glucose monitoring. Impaired awareness of hypoglycaemia is an acquired syndrome in people with insulin-treated diabetes. The definitions, frequency, causes, treatment and prevention of clinical hypoglycaemia and the effects on, and moderators of, cognitive function will be discussed. Two studies have examined the effects of hypoglycaemia on tests of particular cognitive domains in subjects with and without type 1 diabetes. Three further studies have examined the frequency of hypoglycaemia in people with and without impaired awareness, the prevalence of impaired awareness of hypoglycaemia (IAH) and have compared methods of assessing awareness of hypoglycaemia. In study 1 the effect of acute hypoglycaemia on psychomotor function was examined in healthy volunteers (n =20) and adults with type 1 diabetes (n=16). Although acute hypoglycaemia caused significant impairment of several psychomotor functions in nondiabetic adults, a lower magnitude of impairment was observed in those with type 1 diabetes. The potential mechanisms behind this are discussed. In study 2 the effect of acute hypoglycaemia on a simple two-choice reaction time test, which has a model with validated performance parameters, was examined in 14 nondiabetic volunteers. Application of the validated model to the results of this task revealed that hypoglycaemia affected central processing and was not related to the amount of evidence required to make a decision or to peripheral and motor processes. This study is the first to use this method to dissect the effects of hypoglycaemia on cognition and enhances understanding of the mechanism underlying neuroglycopenia in adults. In Study 3 the methods of evaluating awareness of hypoglycaemia were compared in people with type 1 diabetes. Good concordance in clinical characteristics and frequency of biochemical hypoglycaemia was observed between the methods described by Gold et al and Clarke et al but not with a Danish method. In study 4 continuous glucose monitoring (CGM) and home blood glucose monitoring were performed prospectively for 12 months in people with and without IAH. Those with IAH had a 1.6-fold higher incidence of biochemical hypoglycaemia as demonstrated by blood glucose monitoring, but CGM did not identify patients with IAH. In study 5 the prevalence of IAH in a large clinic population with type 1 diabetes was estimated and compared with earlier assessments. The overall prevalence was 20%.

The present study was conducted to clarify and expand knowledge of cognitive functioning in chronic schizophrenia patients (N=21) as compared to a bipolar group (N=20) and a normal group (N=20).

A well-developed body of literature has established the deleterious effects of chronic stress on children’s cognitive development. However, there has been almost no research examining the impact of acutely stressful experiences on children’s cognitive performance. This is surprising given evidence in adults that acute stress alters cognition and plausible links between stress system reactivity and cognitive function. Extending such temporally precise acute stress research to the childhood age range may be valuable for identifying new ways to support children’s function across contexts and elucidating how repetitive stress leads to pervasive alterations in cognitive development. The first chapter reviews the theorized links between acute stress and subsequent cognitive vulnerability as well as the possible role of biological stress systems (i.e. autonomic nervous system, ANS; Hypothalamic Pituitary Adrenal Axis, HPA) in supporting cognitive function. The second chapter serves to validate an in-laboratory stressor paradigm (modified from previous research) as effective at inducing biological reactivity across HPA and ANS systems. Validating this ‘matching task’ was important given the challenges of eliciting stress system reactivity in the early childhood age range. In the third chapter, the relevance of stress system reactivity to children’s concurrent performance on a cognitively challenging matching task was examined. This study was conducted to establish profiles of HPA and ANS (parasympathetic, PNS, and sympathetic, SNS, branches) associated with adaptive cognitive function, under stress. Results indicated that indices of both HPA and PNS reactivity were predictive of cognitive performance, with different results by gender. Finally, we examined the extent to which acute stress (versus control) altered children’s subsequent selective attention and inhibitory control performance. Largely consistent with the adult literature employing Go/No-Go tasks, stress-exposed children experienced selective attention impairment, but no inhibitory control change. Amongst stress-exposed children, higher maternal stress predicted selective attention impairment, which highlights the relevance of early caregiving to children’s stress regulatory ability. In contrary to hypotheses, this effect was not mediated by HPA or ANS reactivity. The final chapter concludes with a discussion of broad implications, limitations, and future directions for acute stress research in early childhood. / 10000-01-01

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