The use of P3b as an indicator of neurophysiologic change from subconcussive impacts in football players

There is a growing appreciation in research that subconcussive impacts may affect cognitive functioning. Canadian University football players (n=45) were separated into three groups based on their position/skill (small skilled, big skilled and big unskilled). An impact measuring device (GForceTracker) was used to record the number of impacts that each player experienced in a season. Player groups were separated into two levels of impact exposure: low and high. Players completed baseline, midseason, postseason, and follow-up neurophysiological tests (four months later) to measure P3b amplitude in response to a visual oddball paradigm, and high versus low impact subgroups for each player group were compared. Small skilled and big skilled players showed significant decreases in P3b amplitudes at midseason and postseason, reflecting decreased attentional resources allocated to the task. No skill group exhibited a significant change from baseline at follow-up, illustrating that in-season cognitive function deficits appear to recover in the offseason

Improving Learning Performance by Applying Economic Knowledge

Digital information economies require information goods producers to learn how to position themselves within a potentially vast product space. Further, the topography of this space is often nonstationary, due to the interactive dynamics of multiple producers changing their position as they try to learn the distribution of consumer preferences and other features of the problem's economic structure. This presents a producer or its agent with a difficult learning problem: how to locate profitable niches in a very large space. In this paper, we present a model of an information goods duopoly and show that, under complete information, producers would prefer not to compete, instead acting as local monopolists and targeting separate niches in the consumer population. However, when producers have no information about the problem they are solving, it can be quite difficult for them to converge on this solution. We show how a modest amount of economic knowledge about the problem can make it much easier, either by reducing the search space, starting in a useful area of the space, or introducing a gradient. These experiments support the hypothesis that a producer using some knowledge of a problem's (economic) structure can outperform a producer that is performing a naive, knowledge-free form of learning.

The Impact of Impacts: Repetitive Head Impact Exposure in Canadian University Football Players

Due to the physical nature of the game and repeated head impacts between players each play, the sport of football has one of the highest incidence rates of concussion. With nearly two million participants, this incidence rate translates to a reserved estimate of 100,000 concussions per year due to the contact nature of the sport. Injury thresholds have proven difficult to establish, so American football concussion research has shifted focus to measuring the accumulation of repetitive head impacts. As there are numerous rule differences between Canadian and American football, head impact exposure may present differently for Canadian players. Accordingly, the objective of this thesis was to investigate the effect of cumulative head impacts on Canadian university football players. This was achieved through three research projects using helmet-mounted sensors to monitor head impacts experienced by football players in practices and games, and measuring brain function via saccadic eye movements. Results illustrated that there were no differences in linear and rotational accelerations between striking and struck players during a collision. However, head impacts that occurred during kickoff plays experienced linear head accelerations that were double in magnitude and rotational head accelerations that were triple in magnitude than other special teams, offensive, and defensive plays (Chapter 2). Furthermore, the accumulation of head impacts significantly increased football players’ saccade latencies, which persisted over two successive seasons (Chapter 3). The total number of head impacts experienced during their career was significantly affected by a player’s position, and not their seniority (Chapter 4). In conclusion, this thesis identified football plays that resulted in high magnitude head accelerations, quantified the effect of individual head impacts on brain function using saccade latencies, and characterized career head impact exposure for football players. These results provide evidence that football head impact exposure needs to be reduced for the health of the players. Coaches and league administrators can use evidence-based research to employ strategies to reduce the number of head impacts to the sport of football

P17. P3b event-related potentials show changes in varsity football players due to accumulated sub-concussive head impacts

BACKGROUND: Concussion has been a focus in football at all levels of participation. However, there is a growing appreciation that repetitive sub-concussive impacts may have more significant effects on overall neurological health than the isolated diagnosed concussions that have been the focus of recent research. The purpose of this study was to evaluate the relationship between the number of head impacts that players experience throughout the season and their P300 evoked potential. METHODS: Canadian university football players (n=45) were separated into three groups based on player mass and position/skill (small-skilled, big-skilled and big-unskilled). Groups were separated into low and high levels of impact exposure based on the total number of head impacts experienced in-season. Players completed baseline, midseason, postseason, and follow-up neurophysiological tests to measure P300 evoked potentials. Statistically significant differences between high versus low impact subgroups for each player group were assessed using independent-samples t-tests. RESULTS: Small-skilled and big-skilled players showed statistically significant decreases in P300 amplitude at midseason and postseason for high impact players compared to low impact players. Follow-up measures revealed that all groups were not significantly different compared to baseline measures. DISCUSSION & CONCLUSION: Players that experience a large number of head impacts in varsity football demonstrate significant decreases in specific EEG measures of cognitive function and information processing. INTERDISCIPLINARY REFLECTION: The combination of biomechanical head impact exposure with neurophysiological outcomes yields insight into the processes behind head impacts and their effects on the human brain

Optimal proposal distributions and adaptive MCMC

Abstract. We review recent work concerning optimal proposal scalings for Metropolis-Hastings MCMC algorithms, and adaptive MCMC algorithms for trying to improve the algorithm on the fly. 1. Introduction. The Metropolis-Hastings algorithm (Metropolis et al., 1953; Hastings, 1970) requires choice of proposal distributions, and it is well-known that some proposals work much better than others. Determining which proposal is best for a particular target distribution is both very important and very difficult. Often this problem is attacked in an ad hoc manne

Cardiorespiratory fitness and preserved medial temporal lobe volume in Alzheimer's Disease

This is not the final published version.Exercise and cardiorespiratory (CR) fitness may moderate age-related regional brain changes in nondemented older adults (ND). The relationship of fitness to Alzheimer's disease (AD) related brain change is understudied, particularly in the hippocampus which is disproportionately affected in early AD. The role of apolipoprotein E4 (apoE4) genotype in modulating this relationship is also unknown. Nondemented (n=56) and early-stage AD subjects (n=61) over age 65 had MRI and CR fitness assessments. Voxel-based morphometry (VBM) techniques were utilized to identify AD-related atrophy. We analyzed the relationship of CR fitness with white and gray matter within groups, assessed fitness-related brain volume change in areas most affected by AD-related atrophy, and then analyzed differential fitness-brain relationships between apoE4 carriers. Atrophy was present in the medial temporal, temporal, and parietal cortices in subjects with mild AD. There was a significant positive correlation of CR fitness with parietal and medial temporal volume in AD subjects. ND subjects did not have a significant relationship between brain volume and CR fitness in the global or SVC analyses. There was not a significant interaction for fitness × apoE4 genotype in either group. In early-stage AD, cardiorespiratory fitness is associated with regional brain volumes in the medial temporal and parietal cortices suggesting that maintaining cardiorespiratory fitness may modify AD-related brain atrophy

Tibialis anterior muscles in mdx mice are highly susceptible to contraction-induced injury

Skeletal muscles of patients with Duchenne muscular dystrophy (DMD) and mdx mice lack dystrophin and are more susceptible to contraction-induced injury than control muscles. Our purpose was to develop an assay based on the high susceptibility to injury of limb muscles in mdx mice for use in evaluating therapeutic interventions. The assay involved two stretches of maximally activated tibialis anterior (TA) muscles in situ . Stretches of 40% strain relative to muscle fiber length were initiated from the plateau of isometric contractions. The magnitude of damage was assessed one minute later by the deficit in isometric force. At all ages (2–19 months), force deficits were four- to seven-fold higher for muscles in mdx compared with control mice. For control muscles, force deficits were unrelated to age, whereas force deficits increased dramatically for muscles in mdx mice after 8 months of age. The increase in susceptibility to injury of muscles from older mdx mice did not parallel similar adverse effects on muscle mass or force production. The in situ stretch protocol of TA muscles provides a valuable assay for investigations of the mechanisms of injury in dystrophic muscle and to test therapeutic interventions for reversing DMD.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43148/1/10974_2004_Article_390575.pd

Adult Comorbidity Evaluation 27 score as a predictor of survival in endometrial cancer patients

BACKGROUND The incidence of endometrial cancer increases with age and is associated with medical comorbidities such as obesity and diabetes. While a few cohort studies of less than 500 patients showed an association between comorbidity and survival in endometrial cancer patients, the degree of association needs to be better described. The Adult Comorbidity Evaluation 27 (ACE-27) is a validated comorbidity instrument that provides a score (0–3) based on the number and severity of medical comorbidities. OBJECTIVE This study was performed to explore the association between medical comorbidities and survival of endometrial cancer patients. STUDY DESIGN Patients diagnosed with endometrial cancer from 2000–2012 were identified from the prospectively maintained Siteman Cancer Center tumor registry. Patients undergoing primary surgical treatment for endometrioid, serous and clear cell endometrial carcinoma were included. Patients primarily treated with radiation, chemotherapy or hormone therapy were excluded. Patients with uterine sarcomas or neuroendocrine tumors were excluded. Patients with missing ACE-27 scores were also excluded from analysis. Information including patient demographics, ACE-27 score, tumor characteristics, adjuvant treatment and survival data were extracted from the database. The association of ACE-27 and overall as well as recurrence-free survival was explored in a multivariable Cox regression analysis after controlling for variables found to be significantly associated with survival in univariable analysis. RESULTS A total of 2073 patients with a median age of 61 years (range 20–94) at diagnosis were identified. ACE-27 score was 0, 1, 2 and 3 in 22%, 38%, 28% and 12% of patients, respectively. Stage distribution was I (73%), II (5%), III (15%) and IV (7%) and grade distribution was 1 (52%), 2 (23%) and 3 (25%). Most patients had endometrioid histology (87%) followed by serous (11%) and clear cell (3%). The median OS for the entire cohort was 54 months [95% confidence interval (CI) 3, 154 months] and median PFS was 50 months [95% CI 2, 154 months]., On univariable analysis, age, race, marital status, stage, grade, histology and treatment type were significantly associated with overall survival and recurrence-free survival. After adjusting for these covariates, patients with ACE-27 score of 2 had a 52% higher risk of death [95% CI 1.16, 2.00] and patients with ACE-27 score of 3 had a 2.35-fold increased risk of death [95% CI 1.73, 3.21] compared to patients with an ACE-27 score of 0. Similarly, patients with ACE-27 score of 2 had a 38% higher risk of recurrence [95% CI 1.07, 1.78] and patients with ACE-27 score of 3 had a 2.05-fold increased risk of recurrence [95% CI 1.53, 2.75] compared to patients with an ACE-27 score of 0. We found no interaction between ACE-27 score and age, stage or treatment type. CONCLUSIONS Our findings demonstrate the importance of comorbidities in estimating the prognosis of endometrial cancer patients, even after adjusting for age and known tumor-specific prognostic factors like stage, grade, histology and adjuvant treatment

Force and power output of fast and slow skeletal muscles from mdx mice 6-28 months old

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66165/1/j.1469-7793.2001.00591.x.pd