Attention, memory, and self-efficacy differences between ADHD and aging individuals

Attention and memory abilities decline with age. Although a similar pattern of attentional and memory decrement has been observed in individuals with Attention Deficit Hyperactivity Disorder (ADHD), these two populations have never been directly compared. The present study examined performance on attention, self-efficacy (SE), and memory tasks by ADHD young adults and non-ADHD younger and older adults. ADHD adults displayed lower attentional SE than both non-ADHD younger and older adults, but performed comparably to older adults on an attention task on which non-ADHD younger adults outperformed both groups. ADHD adults and older adults had lower memory SE than non-AD HD younger adults, but ADHD and non-AD HD younger adults both performed better than older adults on a category cued-recall task. These results suggest that the attentional deficits that characterize both a clinical population and an aging population have similar features. Future directions for research comparing clinical and aging populations on tests of cognitive function are addressed

Doctor of Philosophy

dissertationDiffusion tensor MRI (DT-MRI or DTI) has been proven useful for characterizing biological tissue microstructure, with the majority of DTI studies having been performed previously in the brain. Other studies have shown that changes in DTI parameters are detectable in the presence of cardiac pathology, recovery, and development, and provide insight into the microstructural mechanisms of these processes. However, the technical challenges of implementing cardiac DTI in vivo, including prohibitive scan times inherent to DTI and measuring small-scale diffusion in the beating heart, have limited its widespread usage. This research aims to address these technical challenges by: (1) formulating a model-based reconstruction algorithm to accurately estimate DTI parameters directly from fewer MRI measurements and (2) designing novel diffusion encoding MRI pulse sequences that compensate for the higher-order motion of the beating heart. The model-based reconstruction method was tested on undersampled DTI data and its performance was compared against other state-of-the-art reconstruction algorithms. Model-based reconstruction was shown to produce DTI parameter maps with less blurring and noise and to estimate global DTI parameters more accurately than alternative methods. Through numerical simulations and experimental demonstrations in live rats, higher-order motion compensated diffusion-encoding was shown to successfully eliminate signal loss due to motion, which in turn produced data of sufficient quality to accurately estimate DTI parameters, such as fiber helix angle. Ultimately, the model-based reconstruction and higher-order motion compensation methods were combined to characterize changes in the cardiac microstructure in a rat model with inducible arterial hypertension in order to demonstrate the ability of cardiac DTI to detect pathological changes in living myocardium

Measuring mathematical resilience : an application of the construct of resilience to the study of mathematics

To meet the challenge of accelerating demands for quantitative literacy in the work force, improvements are needed in mathematics education. Student skill must be increased at all ability levels while also reducing the achievement gap across gender, racial and ethnic groups to increase their participation in advanced mathematics coursework and representation in mathematics related careers (National Mathematics Advisory Panel, 2008). Research has shown that affective traits such as motivation and attitude are linked to increased likelihood of taking advanced mathematics courses (Ma, 2006) and are significant predictors of improved cognitive activity and achievement (Buff, Reusser, Rakoczy,& Pauli, 2011; Ethington & Wolfe, 1986). In addition, males generally score more favorably than females on affective variables related to mathematics achievement and persistence (McGraw, Lubienski, & Strutchens, 2006; Sherman & Fennema, 1977; Wilkins and Ma, 2003). Although psychological resilience has been researched extensively (Luthar, Cicchetti, & Becker, 2000; Luthar, 2007) the study of mathematical resilience, defined as a positive adaptive stance to mathematics which allows students to continue learning despite adversity, represents a new approach (Johnston-Wilder & Lee, 2010; Rivera & Waxman, 2011). Math anxiety looks at maladaptive response to learning mathematics and is well-studied (Hembree, 1990; Richardson & Suinn, 1977; Tobias, 1978). In contrast, resilience incorporates factors associated with optimal functioning. Although mathematical resilience has been identified as important for success (Johnston-Wilder & Lee, 2010; Rivera & Waxman, 2011), little consensus exists around its definition and no measures of resilience have been rigorously developed and/or validated. Rivera & Waxman (2011) identified the use of teacher nomination of resilient students as a limitation of their study, further motivating development of an instrument. This presentation will report on efforts to develop and validate an instrument measuring mathematical resilience. Ultimately, the measure will aid in developing and testing models that gauge the role of mathematical resilience in student achievement and persistence in advanced coursework. These models can be used to develop interventions to improve mathematical resilience, achievement, and quantitative literacy (Johnston-Wilder & Lee, 2010)

Androgen action via testicular arteriole smooth muscle cells is important for leydig cell function, vasomotion and testicular fluid dynamics

Regulation of blood flow through the testicular microvasculature by vasomotion is thought to be important for normal testis function as it regulates interstitial fluid (IF) dynamics which is an important intra-testicular transport medium. Androgens control vasomotion, but how they exert these effects remains unclear. One possibility is by signalling via androgen receptors (AR) expressed in testicular arteriole smooth muscle cells. To investigate this and determine the overall importance of this mechanism in testis function, we generated a blood vessel smooth muscle cell-specific AR knockout mouse (SMARKO). Gross reproductive development was normal in SMARKO mice but testis weight was reduced in adulthood compared to control littermates; this reduction was not due to any changes in germ cell volume or to deficits in testosterone, LH or FSH concentrations and did not cause infertility. However, seminiferous tubule lumen volume was reduced in adult SMARKO males while interstitial volume was increased, perhaps indicating altered fluid dynamics; this was associated with compensated Leydig cell failure. Vasomotion was impaired in adult SMARKO males, though overall testis blood flow was normal and there was an increase in the overall blood vessel volume per testis in adult SMARKOs. In conclusion, these results indicate that ablating arteriole smooth muscle AR does not grossly alter spermatogenesis or affect male fertility but does subtly impair Leydig cell function and testicular fluid exchange, possibly by locally regulating microvascular blood flow within the testis

A Catalogue of RR Lyrae Stars from the Northern Sky Variability Survey

A search for RR Lyrae stars has been conducted in the publicly available data of the Northern Sky Variability Survey (NSVS). Candidates have been selected by the statistical properties of their variation; the standard deviation, skewness and kurtosis with appropriate limits determined from a sample 314 known RRab and RRc stars listed in the GCVS. From the period analysis and light curve shape of over 3000 candidates 785 RR Lyrae have been identified of which 188 are previously unknown. The light curves were examined for the Blazhko effect and several new stars showing this were found. Six double-mode RR Lyrae stars were also found of which two are new discoveries. Some previously known variables have been reclassified as RR Lyrae stars and similarly some RR Lyrae stars have been found to be other types of variable, or not variable at all.Comment: Accepted for publication in MNRAS. Tables 1 and 2 are available here in full, but not in the printed editio

The long-line graph of a combinatorial geometry. II. Geometries representable over two fields of different characteristics

AbstractLet q be a power of a prime and let s be zero or a prime not dividing q. Then the number of points in a combinatorial geometry (or simple matroid) of rank n which is representable over GF(q) and a field of characteristic s is at most (qν − qν−1)(2n+1)−n, where ν = 2q−1 − 1

Decision-Making on the Full Information Secretary Problem

The secretary problem is a recreational mathematics problem, suited to laboratory experimentation, that nevertheless is representative of a class of real world sequential decision-making tasks. In the ‘full information’ version, an observer is presented with a sequence of values from a known distribution, and is required to choose the maximum value. The difficulties are that a value can only be chosen at the time it is presented, that the last value in the sequence is a forced choice if none is chosen earlier, and that any value that is not the maximum is scored as completely wrong. We report a study of human performance on full information secretary problems with 10, 20 and 50 values in the sequence, and considers three different heuristics as models of human decision-making. It is found that some people achieve near-optimal levels of accuracy, but that there are individual differences in human performance. A quantitative evaluation of the three heuristics, using the Minimum Description Length criterion, shows inter-individual differences, but intra-individual consistency, in the use of the heuristics. In particular, people seem to use the heuristics that involve choosing a value when it exceeds an internal threshold, but differ in how they set thresholds. On the basis of these findings, a more general threshold-based family of heuristic models is developed.Michael D. Lee, Tess A. O'Connor and Matthew B. Wels

More-or-less elicitation (MOLE): Testing a heuristic elicitation method

The document attached has been archived with permission from the copyright holder.Elicitation of people’s knowledge is a central methodological challenge for psychology, with important impacts in many technical disciplines and industrial settings. The need to convert an expert’s beliefs into a useable format is of particular importance when judgments and decisions are made under uncertainty. Simply asking a person for their best estimate or to estimate a range is subject to many biases – e.g., overconfidence – and methods for eliciting information that avoid these effects are required. This paper presents a heuristic-based elicitation method, More-Or-Less Elicitation (MOLE) which, rather than requiring people make absolute judgments, asks them to make repeated relative judgments. MOLE uses these, along with confidence statements, to construct probability distributions (pdfs) representing a person’s beliefs. We evaluate MOLE by comparing these subjective pdfs with ranges elicited using traditional methods. The central finding is that use of MOLE greatly improves the accuracy and precision of elicited ranges, thereby reducing overconfidence. The benefits of this and other possible heuristic-based methods of elicitation are discussed.Matthew B. Welsh, Michael D. Lee and Steve H. Beg