Spike sorting using hidden markov models

In this paper, hidden Markov models (HMM) is studied for spike sorting. We notice that HMM state sequences have capability to represent spikes precisely and concisely. We build a HMM for spikes, where HMM states respect spike significant shape variations. Four shape variations are introduced: silence, going up, going down and peak. They constitute every spike with an underlying probabilistic dependence that is modelled by HMM. Based on this representation, spikes sorting becomes a classification problem of compact HMM state sequences. In addition, we enhance the method by defining HMM on extracted Cepstrum features, which improves the accuracy of spike sorting. Simulation results demonstrate the effectiveness of the proposed method as well as the efficiency.

Two tests of approach-iron golf skill and their ability to predict tournament performance

The aim of this study was to investigate the convergent and predictive validity of two skill tests that examine the ability of golfers to hit accurate approach-iron shots. Twenty-four high-level golfers (handicap = 2.6 ± 1.7) performed the Nine-Ball Skills Test (assesses the ability to shape/control ball trajectory with high accuracy) and the Approach-Iron Skill Test (assesses the ability to hit straight shots from varying distances with high accuracy). Participants then completed at least eight rounds of tournament golf over the following 90 days and reported an indicator of approach-iron accuracy (per cent error index). A moderate correlation (r = 0.50, P < 0.05) was noted between scores for both tests. Generalised estimating equations, using two covariates (lie of the ball and distance to hole), were used to determine model fit and the amount of variance explained for tournament per cent error index. Results showed that the Approach-Iron Skill Test was the slightly stronger predictor of on-course per cent error index. With both test scores considered together, a minimal amount of additional variance was explained. These findings suggest that either of the tests used individually or combined may be used to predict tournament approach iron performance in high-level golfers.

Development and measurement properties of a putting skill test for high-level golf

Despite a recent increase in the amount of research investigating performance in golf, a comprehensive putting skill test has not been reported in the peer-reviewed literature. In this study, the Golf Australia Putting Test (GAPT) was developed and a series of measurement properties were assessed. Elite (n = 18) and high-level amateur (HLA; n = 22) participants completed six single putts from various areas on six concentric circles (circle radii = 0.9, 1.5, 3.0, 4.6, 6.1 and 7.6 m). Using a scoring system that rewarded participants for holing putts from longer distances, the maximum score from a single round of the test (i.e. 36 putts) was 27 points. After two rounds of the test were completed by all players, a subsample of participants (elite, n = 15; HLA, n = 7) had their putting performance recorded during tournament play for a period of 90 days to assess criterion (predictive) validity of the test. The reliability, sensitivity and discriminative validity of the GAPT were also assessed. Better agreement between Rounds 1 and 2 scores was noted in the elite group, whilst reliability values were similar for both groups. Further, the GAPT scores were shown to predict players from the elite and high-ability groups with a low classification error. An equation for predicting on-course performance from GAPT scores was also developed. Findings from this study indicate that the GAPT is a valid and reliable tool for high-level players and the GAPT may be used for player evaluation in the field.

Reliability of the pictorial scale of perceived movement skill competence in 2 diverse samples of young children

The purpose was to determine the reliability of an instrument designed to assess young children's perceived movement skill competence in two diverse samples.

Associations between young children's perceived and actual ball skill competence and physical activity

Objectives: The relationship between actual and perceived object control competence (ball skills) and the contribution to young children’s physical activity is not known.
Design: Cross sectional study.
Methods: The Test Gross Motor Development-2 assessed actual object control competence and a modified version of the Pictorial Scale of Perceived Competence and Social Acceptance for Young Children assessed perceived object control competence. Moderate- to vigorous-intensity physical activity was measured via accelerometry. Three mixed regression models were performed: (i) object control competence as the predictor and the outcome as perceived object control, (ii) perceived object control competence as the predictor and the outcome moderate to vigorous physical activity and (iii) actual object control as the predictor and the outcome moderate to vigorous physical activity. Models adjusted for school clustering, monitor wear time, sex and age. Interactions between respective predictor variables and sex were performed if warranted. A total of 102 children (56% boys, 44% girls) aged 4–8 years (M 6.3, SD 0.92) completed assessments.
Results: Girls had lower perceived and actual object control competence and were less active than boys. Actual object control competence was positively associated with perceived object control competence (B = 0.11, t(96) = 2.25, p < 0.001, p = 0.027) and this relationship did not differ by sex (p = 0.449); however, neither actual (p = 0.092) nor perceived object control competence (p = 0.827) were associated with moderate to vigorous physical activity.
Discussion: Young children’s perceived ball skill abilities appear to relate to actual competence; however, these measures were not associated with physical activity. In older children, object control skill is associated with physical activity so targeting young children’s object control skills is an intervention priority.

Face validity and reliability of a pictorial instrument for assessing fundamental movement skill perceived competence in young children

To determine reliability and face validity of an instrument to assess young children's perceived fundamental movement skill competence.

Spike sorting using locality preserving projection with gap statistics and landmark-based spectral clustering

Understanding neural functions requires knowledge from analysing electrophysiological data. The process of assigning spikes of a multichannel signal into clusters, called spike sorting, is one of the important problems in such analysis. There have been various automated spike sorting techniques with both advantages and disadvantages regarding accuracy and computational costs. Therefore, developing spike sorting methods that are highly accurate and computationally inexpensive is always a challenge in the biomedical engineering practice.

Associations between skill perceptions and young children's actual fundamental movement skills

-Given that children with low movement skill competence engage in less physical activity, it is important to understand how children's perceptions relate to actual movement competence. This study examined relationships between (i) children's self-perception and objective assessments of their movement skills (object control and locomotor) and (ii) parents' perceptions of the children's movement skills and objective assessment. Children's skill perceptions were assessed using the Pictorial Scale of Perceived Movement Skill Competence for Young Children. Parent perceptions of their child's skills were assessed using a modified version of this instrument. The Test of Gross Motor Development-2nd edition assessed children's skills objectively. Participants were 136 Australian children (51% boys; M = 6.5 yr., SD = 1.1) and 133 parents. Regression analyses (by sex) examined the relationship between perceptions and children's scores for actual skilled performance. Boys' perceptions were associated with their actual object control ability. Parents accurately perceived boys' object control ability and girls' locomotor ability, but not the reverse. This suggests interventions aiming to improve children's movement skills could target parents and be designed to teach parents how to recognize good and poor skill performance in their children.

Influence of price discounts and skill-building strategies on purchase and consumption of healthy food and beverages: outcomes of the Supermarket Healthy Eating for Life randomized controlled trial

BACKGROUND: Fiscal strategies are increasingly considered upstream nutrition promotion measures. However, few trials have investigated the effectiveness or cost effectiveness of pricing manipulations on diet in real-world settings. OBJECTIVE: We assessed the effects on fruit, vegetable, and beverage purchasing and consumption of a 20% price-reduction intervention, a tailored skills-based behavior-change intervention, and a combined intervention compared with a control condition. DESIGN: The Supermarket Healthy Eating for Life trial was a randomized controlled trial conducted over 3 mo [baseline (time 1) to postintervention (time 2) with a 6-mo follow-up (time 3)]. Female primary household shoppers in Melbourne, Australia, were randomly assigned to a 1) skill-building (n = 160), 2) price-reduction (n = 161), 3) combined skill-building and price-reduction (n = 160), or 4) control (n = 161) group. Supermarket transaction data and surveys were used to measure the following study outcomes: fruit, vegetable, and beverage purchases and self-reported fruit and vegetable consumption at each time point. RESULTS: At 3 mo (time 2), price reduction-alone participants purchased more total vegetables and frozen vegetables than did controls. Price reduction-alone and price reduction-plus-skill-building participants purchased more fruit than did controls. Relative to controls, in the price-reduction group, total vegetable consumption increased by 233 g/wk (3.1 servings or 15% more than at baseline), and fruit purchases increased by 364 g/wk (2.4 servings; 35% more than at baseline). Increases were not maintained 6 mo postintervention (time 3). Price reduction-alone participants showed a tendency for a slight increase in fruit consumption at time 2 (P = 0.09) that was maintained at time 3 (P = 0.014). No intervention improved purchases of bottled water or low-calorie beverages. CONCLUSIONS: A 20% price reduction in fruit and vegetables resulted in increased purchasing per household of 35% for fruit and 15% for vegetables over the price-reduction period. These findings show that price modifications can directly increase produce purchases. The Supermarket Healthy Eating for Life trial was registered at Current Controlled Trials Registration as ISRCTN39432901.

Does playing a sports active video game improve young children's ball skill competence?

OBJECTIVES: Actual and perceived object control (commonly ball) skill proficiency is associated with higher physical activity in children and adolescents. Active video games (AVGs) encourage whole body movement to control/play the electronic gaming system and therefore provide an opportunity for screen time to become more active. The purpose of this study was to determine whether playing sports AVGs has a positive influence on young children's actual and perceived object control skills. DESIGN: Two group pre/post experimental design study. METHODS: Thirty-six children aged 6-10 years old from one school were randomly allocated to a control or intervention condition. The Test of Gross Motor Development-3 assessed object control skill. The Pictorial Scale of Perceived Competence for Young Children assessed perceived object control skill. The intervention consisted of 6×50min lunchtime AVG sessions on the Xbox Kinect. Two to three sport games were chosen for participants to play each session. General linear models with either perceived object control or actual object control skill as the outcome variables were conducted. Each base model adjusted for intervention status and pre-score of the respective outcome variable. Additional models adjusted for potential confounding variables (sex of child and game at home). RESULTS: No significant differences between the control and intervention groups were observed for both outcomes. CONCLUSIONS: This study found that playing the Xbox Kinect does not significantly influence children's perceived or actual object control skills, suggesting that the utility of the Xbox Kinect for developing perceived and actual object control skill competence is questionable.

How important is young children's actual and perceived movement skill competence to their physical activity?

OBJECTIVES: To determine the associations between young children's actual and perceived object control and locomotor skills and physical activity and whether associations differ by sex. DESIGN: Cross sectional study. METHODS: A total of 136 children consented. Children had actual skill (Test of Gross Motor Development-2), perceived skill (Pictorial Scale of Perceived Movement Skill Competence for Young Children), and moderate- to vigorous-intensity physical activity (MVPA) (accelerometers) assessed. Independent t-tests assessed sex differences. A regression (with MVPA as the outcome) was performed with all predictor variables (i.e. Actual Object Control, Actual Locomotor, Perceived Object Control, and Perceived Locomotor). Model 2 also adjusted for age, sex, accelerometer wear time and whether the child was from an English speaking background. Interaction terms between the respective actual or perceived skill factor and sex were added to assess sex differences. RESULTS: Analyses were conducted on 109 children (59 boys, 50 girls; mean age=6.5 years, SD=1.0). Boys had higher actual and perceived object control skill and were more active by an average of 19min per day. There were no sex differences in locomotor skills. There were no associations between skill factors and MVPA, except for girls, where locomotor skill was a significant predictor of MVPA (B=3.66, p=0.016). CONCLUSIONS: Actual rather than perceived skill competence was more important to MVPA in this sample. Locomotor skill competence may be more important than object control skill competence for girls as they may engage in types of physical activity that do not require object control mastery.