Cumulative Head Research Articles

Higher head accelerations observed in female athletes than in male athletes across age

ObjectiveTo compare linear and rotational acceleration across age and gender in controlled purposeful soccer heading.DesignProspective study.SettingBiomechanics laboratory.ParticipantsOne-hundred soccer players (42 male, 58 female, 17.1±3.5 years, 168.5±20.3 cm, 61.5±13.7 kg) classified as collegiate, high school (HS), or youth (12–14 years) male (MS) or female (FS) soccer players.Exclusionary criteriahistory of neurologic disorder, cervical spine injury, or head injury in the past 6 months.InterventionsWe implemented a unique soccer heading paradigm that allows for precise control of head impact magnitude, direction, and frequency to model repetitive head impacts in sport. This model consists of controlled soccer heading (12 headers at 11.2 m/s from a JUGS machine) while measuring linear and rotational accelerations using a triaxial accelerometer and gyroscope affixed to the back of the head. Linear accelerations were transformed to the head center-of-gravity using 3D motion capture data and standard rigid body dynamics equations.Outcome measuresLinear and rotational accelerations at the head center-of-gravity.Main results[Average±Standard Deviation (95% Confidence Interval)] Collegiate [42.4±11.5 g (36.8–47.9); 3.35±0.87 krad/s2(2.9–3.8)], HS [38.5±13.1 g (32.2–44.8); 3.16±1.01 krad/s2(2.7–3.7)], and youth [40.5±14.9 g(33.1–47.9); 3.20±1.24 krad/s2(2.6–3.8)] FS produced higher linear and rotational accelerations than both the collegiate [26.1±9.5 g(21.7–30.6); 2.13±1.07 krad/s2(1.6–2.6)] (linear: p<0.001, p?= 0.012, p=0.002; rotational: p=0.002, p=0.015, p=0.011, respectively) and HS [26.7±5.9 g(23.2–30.1); 2.18±0.40 krad/s2(2.0–2.4)] (linear: p=0.002, p=0.045, p?= 0.012; rotational: p=0.011, p=0.052, p=0.040, respectively) MS.ConclusionsCollegiate and HS FS have higher head accelerations than their male counterparts, but at the youth level, there are no differences across gender. These data suggest that FS may be exposed to greater cumulative head accelerations from repeated heading of a soccer ball over a career than MS.Competing interestsNone.

Reliability of the Head Impact Exposure Estimate in Former Professional Football Athletes

PURPOSE: The long-term neurological effects of exposure to repetitive subconcussive impacts, such as those occurring in American football, are poorly understood. Recent studies have suggested that greater exposure to subconcussive impacts is associated with worse health outcomes in former high school, collegiate, and professional football players. Helmet accelerometer research has shown the magnitude, location, and frequency of impacts sustained by American football players varies widely and are dependent on many factors, including position, practice structure, playing time, and career duration. Thus, estimating cumulative head impact exposure across a player’s career using these factors may prove useful in studying their long-term effects. Previously, our research center developed the head impact exposure estimate (HIEE), a structured interview covering game and practice contact hours over the course of an athlete’s playing career. However, the test-retest reliability of the HIEE is unknown. METHODS: We examined the test-retest reliability of the HIEE in 11 retired professional football athletes (mean age: 64.7 +/- 3.13y). The HIEE was administered by two raters over two occasions with a mean period of separation of 4.4 +/- 0.42y. Intra-class correlation coefficients, ICC(2,1), were used to quantify agreement between HIEE assessments. We calculated ICC(2,1) values for the overall HIEE, as well as the two subcomponents of practice- and game-weighted contact hours. P-values were determined for the test of ICC=0 and 95% confidence intervals were calculated. RESULTS: The mean HIEE at assessment 1 was 3423.76 +/- 1406.02hrs while at assessment 2, the mean was 2627.68 +/- 819.56hrs (t10=1.75, P=0.11). The overall ICC(2,1) for the HIEE was 0.124 (P = 0.33; 95% CI: -0.36, 0.62). The ICC(2,1) for weighted practice contact hours was 0.111 (P = 0.36; 95% CI: -0.44, 0.63) and for weighted game contact hours was 0.330 (P=0.01; 95% CI: -0.11, 0.75). CONCLUSIONS: Overall, the head impact exposure estimate had poor reliability. The subcomponent of game contact hours was more reliable than practice contact hours. The reported number of contact practices per week appears to be the major factor reducing reliability. A more explicit definition of a “contact practice” may improve reliability.

Individual Impact Magnitude vs. Cumulative Magnitude for Estimating Concussion Odds.

Helmeted impact devices have allowed researchers to investigate the biomechanics of head impacts in vivo. While increased impact magnitude has been associated with greater concussion risk, a definitive concussive threshold has not been established. It is likely that concussion risk is not determined by a single impact itself, but a host of predisposing factors. These factors may include genetics, fatigue, and/or prior head impact exposure. The objective of the current paper is to investigate the association between cumulative head impact magnitude and concussion risk. It is hypothesized that increased cumulative magnitudes will be associated with greater concussion risk. This retrospective analysis included participants that were recruited from regional high-schools in Illinois and Michigan from 2007 to 2014 as part of an ongoing study on concussion biomechanics. Across seven seasons, 185 high school football athletes were instrumented with the Head Impact Telemetry system. Out of 185 athletes, 31 (17%) sustained a concussion, with two athletes sustaining two concussions over the study period, yielding 33 concussive events. The system recorded 78,204 impacts for all concussed players. Linear acceleration, rotational acceleration, and head impact telemetry severity profile (HITsp) magnitudes were summed within five timeframes: the day of injury, three days prior to injury, seven days prior to injury, 30days prior to injury, and prior in-season exposure. Logistic regressions were modeled to explain concussive events based on the singular linear acceleration, rotational acceleration, and HITsp event along with the calculated summations over time. Linear acceleration, rotational acceleration, and HITsp all produced significant models estimating concussion (p<0.05). The strongest estimators of a concussive impact were the linear acceleration (OR=1.040, p<0.05), rotational acceleration (OR=1.001, p<0.05), and HITsp (OR=1.003, p<0.05) for the singular impact rather than any of the cumulative magnitude calculations. Moreover, no cumulative count measure was significant for linear or rotational acceleration. Results from this investigation support the growing literature indicating cumulative magnitude is not related to concussion likelihood. Cumulative magnitude is a simplistic measure of the total exposure sustained by a player over a given period. However, this measure is limited as it assumes the brain is a static structure unable to undergo self-repair. Future research should consider how biological recovery between impacts may influence concussion risk.

Correlation of Head Impacts to Change in Balance Error Scoring System Scores in Division I Men's Lacrosse Players.

Background:Investigation into the effect of cumulative subconcussive head impacts has yielded various results in the literature, with many supporting a link to neurological deficits. Little research has been conducted on men’s lacrosse and associated balance deficits from head impacts.Hypotheses:(1) Athletes will commit more errors on the postseason Balance Error Scoring System (BESS) test. (2) There will be a positive correlation to change in BESS scores and head impact exposure data.Study Design:Prospective longitudinal study.Level of Evidence:Level 3.Methods:Thirty-four Division I men’s lacrosse players (age, 19.59 ± 1.42 years) wore helmets instrumented with a sensor to collect head impact exposure data over the course of a competitive season. Players completed a BESS test at the start and end of the competitive season.Results:The number of errors from pre- to postseason increased during the double-leg stance on foam (P < 0.001), tandem stance on foam (P = 0.009), total number of errors on a firm surface (P = 0.042), and total number of errors on a foam surface (P = 0.007). There were significant correlations only between the total errors on a foam surface and linear acceleration (P = 0.038, r = 0.36), head injury criteria (P = 0.024, r = 0.39), and Gadd Severity Index scores (P = 0.031, r = 0.37).Conclusion:Changes in the total number of errors on a foam surface may be considered a sensitive measure to detect balance deficits associated with cumulative subconcussive head impacts sustained over the course of 1 lacrosse season, as measured by average linear acceleration, head injury criteria, and Gadd Severity Index scores. If there is microtrauma to the vestibular system due to repetitive subconcussive impacts, only an assessment that highly stresses the vestibular system may be able to detect these changes.Clinical Relevance:Cumulative subconcussive impacts may result in neurocognitive dysfunction, including balance deficits, which are associated with an increased risk for injury. The development of a strategy to reduce total number of head impacts may curb the associated sequelae. Incorporation of a modified BESS test, firm surface only, may not be recommended as it may not detect changes due to repetitive impacts over the course of a competitive season.

The effect of repetitive subconcussive collisions on brain integrity in collegiate football players over a single football season: A multi-modal neuroimaging study.

The cumulative effect of repetitive subconcussive collisions on the structural and functional integrity of the brain remains largely unknown. Athletes in collision sports, like football, experience a large number of impacts across a single season of play. The majority of these impacts, however, are generally overlooked, and their long-term consequences remain poorly understood. This study sought to examine the effects of repetitive collisions across a single competitive season in NCAA Football Bowl Subdivision athletes using advanced neuroimaging approaches. Players were evaluated before and after the season using multiple MRI sequences, including T1-weighted imaging, diffusion tensor imaging (DTI), arterial spin labeling (ASL), resting-state functional MRI (rs-fMRI), and susceptibility weighted imaging (SWI). While no significant differences were found between pre- and post-season for DTI metrics or cortical volumes, seed-based analysis of rs-fMRI revealed significant (p < 0.05) changes in functional connections to right isthmus of the cingulate cortex (ICC), left ICC, and left hippocampus. ASL data revealed significant (p < 0.05) increases in global cerebral blood flow (CBF), with a specific regional increase in right postcentral gyrus. SWI data revealed that 44% of the players exhibited outlier rates (p < 0.05) of regional decreases in SWI signal. Of key interest, athletes in whom changes in rs-fMRI, CBF and SWI were observed were more likely to have experienced high G impacts on a daily basis. These findings are indicative of potential pathophysiological changes in brain integrity arising from only a single season of participation in the NCAA Football Bowl Subdivision, even in the absence of clinical symptoms or a diagnosis of concussion. Whether these changes reflect compensatory adaptation to cumulative head impacts or more lasting alteration of brain integrity remains to be further explored.

Repetitive head impact exposure and later-life plasma total tau in former National Football League players

IntroductionBlood protein analysis of total tau (t-tau) may be a practical screening biomarker for chronic traumatic encephalopathy (CTE), a neurodegenerative tauopathy associated with repetitive head impact (RHI) exposure. We examined plasma t-tau in symptomatic former National Football League (NFL) players compared with controls and the relationship between RHI exposure and later-life plasma t-tau. MethodsNinety-six former NFL players (age 40–69) and 25 same-age controls underwent blood draw to determine plasma t-tau levels. The cumulative head impact index (CHII) quantified RHI exposure. Subjects completed measures of clinical function. ResultsA higher CHII predicted greater plasma t-tau in the former NFL players (P = .0137). No group differences in plasma t-tau emerged, but a concentration ≥3.56 pg/mL was 100% specific to former NFL players. Plasma t-tau did not predict clinical function. DiscussionGreater RHI exposure predicted higher later-life plasma t-tau concentrations, and further study on plasma t-tau as a candidate screening biomarker for CTE is warranted.

Validation and calibration of HeadCount, a self-report measure for quantifying heading exposure in soccer players

ABSTRACTThe long-term effects of repetitive head impacts due to heading are an area of increasing concern, and exposure must be accurately measured; however, the validity of self-report of cumulative soccer heading is not known. In order to validate HeadCount, a 2-week recall questionnaire, the number of player-reported headers was compared to the number of headers observed by trained raters for a men’s and a women’s collegiate soccer teams during an entire season of competitive play using Spearman’s correlations and intraclass correlation coefficients (ICCs), and calibrated using a generalized estimating equation. The average Spearman’s rho was 0.85 for men and 0.79 for women. The average ICC was 0.75 in men and 0.38 in women. The calibration analysis demonstrated that men tend to report heading accurately while women tend to overestimate. HeadCount is a valid instrument for tracking heading behaviour, but may have to be calibrated in women.

Does Game Participation Impact Cognition and Symptoms in Elite Football Players?

To measure neurocognitive functioning in college and professional football players after game participation. Retrospective, cross-sectional cohort design. Ninety-four male university and professional football players. All participants completed Immediate Postconcussion Assessment and Cognitive Testing (ImPACT) testing at baseline, and either at postconcussion (group 1) or postgame (group 2) participation. Results from the 5 ImPACT composite scores (Verbal Memory, Visual Memory, Visual Motor Speed, Reaction Time and Impulse Control) and Total Symptom Score. Repeated-measures analysis of variance demonstrated a significant main effect for time (improvements) in 3 of 5 domains for the postconcussion group, but no improvements in the postgame group. The postconcussion group presented with significantly improved results on 4 of 5 ImPACT domains compared with the postgame group at the follow-up time interval. Participation in a football game with potential cumulative head contacts did not yield increased symptoms or cognitive impairment. However, the absence of improvement in cognitive functioning in noninjured football players, which was found in those players who were returned to play after an injury, may suggest that there is a measureable impact as a result of playing football.

Development of a head impact monitoring "Intelligent Mouthguard".

The authors present the development and laboratory system-level testing of an impact monitoring "Intelligent Mouthguard" intended to help with identification of potentially concussive head impacts and cumulative head impact dosage. The goal of Intelligent Mouthguard is to provide an indicator of potential concussion risk, and help caregiver identify athletes needing sideline concussion protocol testing. Intelligent Mouthguard may also help identify individuals who are at higher risk based on historical dosage. Intelligent Mouthguard integrates inertial sensors to provide 3-degree of freedom linear and rotational kinematics. The electronics are fully integrated into a custom mouthguard that couples tightly to the upper teeth. The combination of tight coupling and highly accurate sensor data means the Intelligent Mouthguard meets the National Football League (NFL) Level I validity specification based on laboratory system-level test data presented in this study.

Cumulative Head Impact Exposure Predicts Later-Life Depression, Apathy, Executive Dysfunction, and Cognitive Impairment in Former High School and College Football Players.

The term "repetitive head impacts" (RHI) refers to the cumulative exposure to concussive and subconcussive events. Although RHI are believed to increase risk for later-life neurological consequences (including chronic traumatic encephalopathy), quantitative analysis of this relationship has not yet been examined because of the lack of validated tools to quantify lifetime RHI exposure. The objectives of this study were: 1) to develop a metric to quantify cumulative RHI exposure from football, which we term the "cumulative head impact index" (CHII); 2) to use the CHII to examine the association between RHI exposure and long-term clinical outcomes; and 3) to evaluate its predictive properties relative to other exposure metrics (i.e., duration of play, age of first exposure, concussion history). Participants included 93 former high school and collegiate football players who completed objective cognitive and self-reported behavioral/mood tests as part of a larger ongoing longitudinal study. Using established cutoff scores, we transformed continuous outcomes into dichotomous variables (normal vs. impaired). The CHII was computed for each participant and derived from a combination of self-reported athletic history (i.e., number of seasons, position[s], levels played), and impact frequencies reported in helmet accelerometer studies. A bivariate probit, instrumental variable model revealed a threshold dose-response relationship between the CHII and risk for later-life cognitive impairment (p < 0.0001), self-reported executive dysfunction (p < 0.0001), depression (p < 0.0001), apathy (p = 0.0161), and behavioral dysregulation (p < 0.0001). Ultimately, the CHII demonstrated greater predictive validity than other individual exposure metrics.

Abnormalities in Diffusional Kurtosis Metrics Related to Head Impact Exposure in a Season of High School Varsity Football.

The purpose of this study was to determine whether the effects of cumulative head impacts during a season of high school football produce changes in diffusional kurtosis imaging (DKI) metrics in the absence of clinically diagnosed concussion. Subjects were recruited from a high school football team and were outfitted with the Head Impact Telemetry System (HITS) during all practices and games. Biomechanical head impact exposure metrics were calculated, including: total impacts, summed acceleration, and Risk Weighted Cumulative Exposure (RWE). Twenty-four players completed pre- and post-season magnetic resonance imaging, including DKI; players who experienced clinical concussion were excluded. Fourteen subjects completed pre- and post-season Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT). DKI-derived metrics included mean kurtosis (MK), axial kurtosis (K axial), and radial kurtosis (K radial), and white matter modeling (WMM) parameters included axonal water fraction, tortuosity of the extra-axonal space, extra-axonal diffusivity (De axial and radial), and intra-axonal diffusivity (Da). These metrics were used to determine the total number of abnormal voxels, defined as 2 standard deviations above or below the group mean. Linear regression analysis revealed a statistically significant relationship between RWE combined probability (RWECP) and MK. Secondary analysis of other DKI-derived and WMM metrics demonstrated statistically significant linear relationships with RWECP after covariate adjustment. These results were compared with the results of DTI-derived metrics from the same imaging sessions in this exact same cohort. Several of the DKI-derived scalars (Da, MK, K axial, and K radial) explained more variance, compared with RWECP, suggesting that DKI may be more sensitive to subconcussive head impacts. No significant relationships between DKI-derived metrics and ImPACT measures were found. It is important to note that the pathological implications of these metrics are not well understood. In summary, we demonstrate a single season of high school football can produce DKI measurable changes in the absence of clinically diagnosed concussion.

Long-term Effects Of Adolescent Concussion History On Cognition

Following concussion, persistent changes in cognition in an elite athlete population is thought to occur. However, it is unclear if concussion history affects cognitive performance in a non-elite athlete population. PURPOSE: To assess the long-term effects of concussion history on cognitive performance in a non-elite athlete population. METHODS: Participants (N=84) were divided into three age groups (18-29 years, n=45; 40-49 years, n=19; 60-69 years, n=20) and two concussion history groups (control, n=54; concussion history, n=30) based on self-report. Following consent, each participant was instructed complete a computerized clinical battery assessing multiple cognitive domains. The cognitive battery consists of four test modules: detection (simple reaction time), identification (choice reaction time), one card learning (working memory), and one back speed/accuracy (attention and working memory). The cognitive battery provides five output scores: processing speed, attention, learning, working memory speed, and working memory accuracy. Two-factor (Age x Group) multivariate ANOVA, post hoc comparisons when indicated, and Cohen’s d effect sizes were calculated to compare within age and between groups. RESULTS: There were no significant (p’s > 0.05) main effects for age group or concussion history group, nor an age by concussion history interaction on the five outcome measures. CONCLUSION: These data do not support a relationship between prior concussion history and long-term cognitive declines in non-elite athletes. These results may differ from previous findings in an elite-athlete population due to differences in cumulative sub-concussive head trauma exposure between the two populations. Future research should employ a more sensitive cognitive test battery capable of detecting more subtle cognitive impairment.

Cognitive Function as Related to Cumulative Head Impact Exposure in Football: Effects of Position

Repetitive sub‐clinical head impacts are linked to progressive cognitive decline and chronic traumatic encephalopathy (CTE) diagnoses in professional contact‐sport athletes post mortem. There exists a gap however in understanding when this long‐term damage occurs, and specifically in determining the career stage when signs of injury can be first detected or even the influence of a single season of play. In 2014, our group used a 12‐test online cognitive battery (www.cambridgebrainsciences.com) to study the cognitive function of a population of 35 male varsity football athletes in both the pre‐ and post‐season. In comparison to controls, the athletes showed decreased scores in the pre‐season with no pre‐ to post‐season differences. Additionally, athletes’ concussion histories were not correlated with any cognitive measure.Given the positional variation in head impact exposure profiles and CTE diagnoses in football, the objective of the current study is to determine the influence of player position, and thus head impact exposure profile, on cognitive function over the course of a single season as well as the athletes’ careers up until this point. Participants consisted of an overlapping sample of athletes from the same football team for the 2014 and 2015 athletic seasons. Cognitive function was determined using cognitive battery scores and reaction times of players in both the pre‐ and post‐ season. Preliminary results, both aggregated and stratified by position demonstrate there was no difference between pre‐ and post‐season battery scores or reaction times. In accordance with our previous results, this suggests that a single season of head impact exposure does not cause significant cognitive decline. However, when considering all data as a representation of career‐long exposure, results suggest that wide receivers have the fastest reaction times on cognitive tests and consistently outperform their defensive linemen counterparts in terms of battery score. Defensive linemen also demonstrate the most variable reaction times. Previous studies analysing impact magnitude and frequency suggest that defensive linemen sustain significantly more low force hits while the wide receivers endure fewer hits but of high collision forces. Additionally, studies assessing the frequency of CTE diagnosis by position suggest fewer diagnoses in former wide receivers than in defensive linemen. Collectively, these results align well with previously published biomechanical and clinical literature and suggest that there is a continuum of cognitive function impairments across positions and head impact exposure profiles. Better characterization of the relationship between sport‐and position‐specific head impact exposure profiles and cognitive function may help guide participation, coaching strategies, and safe play decisions in sport.Support or Funding InformationResearch supported by CERC funding awarded to AMO

Collegiate women's soccer players suffer greater cumulative head impacts than their high school counterparts

Soccer is the source of the highest concussion rates among female athletes and is associated with neurological deficits at many levels of play. Despite its importance to our understanding of head trauma in female athletes, little is known about the number and magnitude of head impacts experienced by female soccer players. Head impacts experienced by high school and collegiate athletes were quantified using xPatch sensors (X2 Biosystems) affixed behind the right ear of each player.The average peak translational acceleration (PTA) sustained by players at the high school level was significantly lower than that of the collegiate players, but the average peak angular accelerations (PAA) were not significantly different. Given that the collegiate players took many more impacts throughout the season, their mean cumulative exposure to translational (cPTA) and angular accelerations (cPAA) were significantly higher than those of the high school players. Additional research is required to determine whether the differences in cumulative exposure are responsible for the elevated risk of concussion in collegiate soccer players or if there are additional risk factors.

Estimating Contact Exposure in Football Using the Head Impact Exposure Estimate.

Over the past decade, there has been significant debate regarding the effect of cumulative subconcussive head impacts on short and long-term neurological impairment. This debate remains unresolved, because valid epidemiological estimates of athletes' total contact exposure are lacking. We present a measure to estimate the total hours of contact exposure in football over the majority of an athlete's lifespan. Through a structured oral interview, former football players provided information related to primary position played and participation in games and practice contacts during the pre-season, regular season, and post-season of each year of their high school, college, and professional football careers. Spring football for college was also included. We calculated contact exposure estimates for 64 former football players (n = 32 college football only, n = 32 professional and college football). The head impact exposure estimate (HIEE) discriminated between individuals who stopped after college football, and individuals who played professional football (p < 0.001). The HIEE measure was independent of concussion history (p = 0.82). Estimating total hours of contact exposure may allow for the detection of differences between individuals with variation in subconcussive impacts, regardless of concussion history. This measure is valuable for the surveillance of subconcussive impacts and their associated potential negative effects.

The Effects of Clinical, and Sub‐Clinical mTBI on Cognitive Function in Varsity Athletes

Emerging research suggests that head trauma, causing clinical (medically diagnosed, ie. concussion), or sub‐clinical minor Traumatic Brain Injury (mTBI) is cumulative and correlates negatively with cognitive function. Given the high prevalence of head trauma in contact athletics, better understanding the relationship between contact‐athletic activity, mTBI, and independent aspects of cognitive function is imperative.Sixty‐eight varsity football athletes were recruited to examine how cumulative head trauma and self‐reported mTBI affect cognitive function. Participants completed a 12‐test online cognitive battery (www2.cbstrials.com) at time points prior to, bi‐weekly throughout, and after the season. With each cognitive test, participants also completed a personal history questionnaire to assess their ongoing athletic activity and mTBI status. Through assessing three distinct aspects of cognitive function (verbal ability, short‐term memory, and reasoning ability) via the cognitive battery in a longitudinal fashion, we will comprehensively examine the effects of contact athletic participation on independent aspects of cognitive function. Results look to better characterize the relationship between mTBI and cognitive function as well as inform sport decisions made by athletes, recreationalists and athletic governance councils to guide participation and safe play decisions.

Head Motion Parameters in fMRI Differ Between Patients with Mild Cognitive Impairment and Alzheimer Disease Versus Elderly Control Subjects

Motion artifacts are a well-known and frequent limitation during neuroimaging workup of cognitive decline. While head motion typically deteriorates image quality, we test the hypothesis that head motion differs systematically between healthy controls (HC), amnestic mild cognitive impairment (aMCI) and Alzheimer disease (AD) and consequently might contain diagnostic information. This prospective study was approved by the local ethics committee and includes 28 HC (age 71.0±6.9years, 18 females), 15 aMCI (age 67.7±10.9years, 9 females) and 20 AD (age 73.4±6.8years, 10 females). Functional magnetic resonance imaging (fMRI) at 3T included a 9min echo-planar imaging sequence with 180 repetitions. Cumulative average head rotation and translation was estimated based on standard fMRI preprocessing and compared between groups using receiver operating characteristic statistics. Global cumulative head rotation discriminated aMCI from controls [p<0.01, area under curve (AUC) 0.74] and AD from controls (p<0.01, AUC 0.73). The ratio of rotation z versus y discriminated AD from controls (p<0.05, AUC 0.71) and AD from aMCI (p<0.05, AUC of 0.75). Head motion systematically differs between aMCI/AD and controls. Since motion is not random but convoluted with diagnosis, the higher amount of motion in aMCI and AD as compared to controls might be a potential confounding factor for fMRI group comparisons. Additionally, head motion not only deteriorates image quality, yet also contains useful discriminatory information and is available for free as a "side product" of fMRI data preprocessing.

링레이저 자이로 기반 관성항법장치와 위성항법장치의 강결합 방식 시스템 구현

This paper explores a real-time system implementation to couple tightly StrapDown Inertial Navigation System(SDINS) and Global Positioning System(GPS) mounted on the aircraft. When implementing the SDINS/GPS coupled system in real-time processor, we have to deliberate SDINS`s unique characteristics based on the ring laser gyro, and besides, lever-arm, measurements, and error compensation method. The novel modeling method is applied to system the misalignment error term of gyro to estimate the cumulative heading attitude errors while the aircraft banking to turn repeatedly. Captive Flight Test results show that the proposed modeling strategy has good performance.

Estimation of destruction of missile with cumulative head during contact with chosen type of rod armour

Estimation of destruction of missile with cumulative head during contact with chosen type of rod armour

A Proposed Method to Reduce Underreporting of Brain Injury in Sports

The topic of brain injury and concussion in helmeted sports, including football, has received significant media attention in recent months, particularly with respect to the potential long-term negative consequences of repeated impacts to the head. Initiatives to reduce brain injuries in helmeted spo