Can Motivation Normalize Working Memory and Task Persistence in Children with Attention-Deficit/Hyperactivity Disorder? The Effects of Money and Computer-Gaming

Visual-spatial Working Memory (WM) is the most impaired executive function in children with Attention-Deficit/Hyperactivity Disorder (ADHD). Some suggest that deficits in executive functioning are caused by motivational deficits. However, there are no studies that investigate the effects of motivation on the visual-spatial WM of children with- and without ADHD. Studies examining this in executive functions other than WM, show inconsistent results. These inconsistencies may be related to differences in the reinforcement used. The effects of different reinforcers on WM performance were investigated in 30 children with ADHD and 31 non-ADHD controls. A visual-spatial WM task was administered in four reinforcement conditions: Feedback-only, 1 euro, 10 euros, and a computer-game version of the task. In the Feedback-only condition, children with ADHD performed worse on the WM measure than controls. Although incentives significantly improved the WM performance of children with ADHD, even the strongest incentives (10 euros and Gaming) were unable to normalize their performance. Feedback-only provided sufficient reinforcement for controls to reach optimal performance, while children with ADHD required extra reinforcement. Only children with ADHD showed a decrease in performance over time. Importantly, the strongest incentives (10 euros and Gaming) normalized persistence of performance in these children, whereas 1 euro had no such effect. Both executive and motivational deficits give rise to visual-spatial WM deficits in ADHD. Problems with task-persistence in ADHD result from motivational deficits. In ADHD-reinforcement studies and clinical practice (e.g., assessment), reinforcement intensity can be a confounding factor and should be taken into account. Gaming can be a cost-effective way to maximize performance in ADHD

Testing assumptions for endophenotype studies in ADHD: Reliability and validity of tasks in a general population sample

BACKGROUND: Advances in both genetic and cognitive-experimental studies on attention deficit hyperactivity disorder (ADHD) have opened new opportunities for cognitive endophenotype research. In such genetic designs the focus is on individual differences in characteristics, associated with ADHD, that can be measured reliably over time. Genetic studies that take a 'quantitative trait loci' approach hypothesise that multiple susceptibility genes contribute to a continuous dimension of ADHD symptoms. As an important initial step, we aimed to investigate the underlying assumptions that (1) key cognitive-experimental tasks indicate adequate test-retest reliability and (2) ADHD symptom scores in a general population sample are associated with performance on these tasks. METHODS: Forty-nine children were assessed on a go/no-go task and a reaction time task (the 'fast task') that included manipulations with event rate and incentives. The children were assessed twice, with a test-retest interval of two weeks. RESULTS: The majority of the task variables demonstrated moderate-to-good test-retest reliability. The correlations between teacher ratings of ADHD symptoms and key task variables were .4–.6: ADHD symptoms were associated with poor performance (especially high reaction time variability) in a slow baseline condition, whereas there was low or no association in conditions with a faster event rate or incentives. In contrast, no clear pattern of findings emerged based on parent ratings of ADHD symptoms. CONCLUSION: The data support the usefulness of the go/no-go and fast tasks for genetic studies, which require reliable and valid indices of individual differences. The overall pattern of associations between teacher ratings of ADHD symptoms and task variables is consistent with effects of event rate and incentives on performance, as predicted by the model of activation and arousal regulation. The lack of a clear pattern of findings with parent ratings of ADHD symptoms warrants further study

Shared and Disorder-Specific Event-Related Brain Oscillatory Markers of Attentional Dysfunction in ADHD and Bipolar Disorder.

Attention-deficit/hyperactivity disorder (ADHD) and bipolar disorder (BD) often present with overlapping symptoms and cognitive impairments, such as increased fluctuations in attentional performance measured by increased reaction-time variability (RTV). We previously provided initial evidence of shared and distinct event-related potential (ERP) impairments in ADHD and BD in a direct electrophysiological comparison, but no study to date has compared neural mechanisms underlying attentional impairments with finer-grained brain oscillatory markers. Here, we aimed to compare the neural underpinnings of impaired attentional processes in ADHD and BD, by examining event-related brain oscillations during a reaction-time task under slow-unrewarded baseline and fast-incentive conditions. We measured cognitive performance, ERPs and brain-oscillatory modulations of power and phase variability in 20 women with ADHD, 20 women with BD (currently euthymic) and 20 control women. Compared to controls, both ADHD and BD groups showed increased RTV in the baseline condition and increased RTV, theta phase variability and lower contingent negative variation in the fast-incentive condition. Unlike controls, neither clinical group showed an improvement from the slow-unrewarded baseline to the fast-incentive condition in attentional P3 amplitude or alpha power suppression. Most impairments did not differ between the disorders, as only an adjustment in beta suppression between conditions (lower in the ADHD group) distinguished between the clinical groups. These findings suggest shared impairments in women with ADHD and BD in cognitive and neural variability, preparatory activity and inability to adjust attention allocation and activation. These overlapping impairments may represent shared neurobiological mechanisms of attentional dysfunction in ADHD and BD, and potentially underlie common symptoms in both disorders.We thank all who made this research possible: The National Adult ADHD Clinic at the South London and Maudsley Hospital, Dr Helen Costello, Prof Sophia Frangou, Prof Anne Farmer, Jessica Deadman, Hannah Collyer, Sarah-Jane Gregori, and all participants who contributed their time to the study. Dr Giorgia Michelini was supported by a 1+3 PhD studentship awarded by the MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London (G9817803). This project was supported by an Economic and Social Research Council studentship to Dr Viryanaga Kitsune (ES/100971X/1). Dr Giorgia Michelini and Prof Philip Asherson are supported by generous grants from the National Institute for Health Research Biomedical Research Centre for Mental Health at King’s College London, Institute of Psychiatry, Psychology and Neuroscience and South London and Maudsley National Health Service (NHS) Foundation Trust. The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication

Magnetoelektryczne silniki prądu stałego z proszkowymi obwodami magnetycznymi

Producers of electric machines permanently struggle to offer machines with better performance and operational parameters with simultaneous reduction of manufacturing costs. In case of transducers with magnetic circuits, application of powder magnetic materials offers wide opportunities for cost-effectiveness production and good operational parameters. The studies reported herein deal with a commutator-type DC motor where a conventional magnetic circuit was replaced with a one that was made by compaction of magnetic powders with an appropriate binder. The paper shows the measurements of DC motors with prepared powder magnetic circuits and traditional magnetic circuits.Rozwój nowych generacji materiałów magnetycznych pozwala na rozwój nowych urządzeń z obwodami magnetycznymi. Opracowanie technologii wytwarzania proszkowych materiałów magnetycznych umożliwia zmianę konstrukcji i technologii wytwarzania urządzeń z obwodami magnetycznymi. Ostatnie lata przyniosły rozwój proszkowych materiałów magnetycznie miękkich i magnetycznie twardych. W obecnie produkowanych maszynach elektrycznych, magnetycznie miękka część obwodu magnetycznego wykonywana jest z blach elektrotechnicznych, zaś jako źródło wzbudzenia stosowane są najczęściej magnesy ferrytowe. Blachy elektrotechniczne charakteryzują się bardzo dobrymi właściwościami magnetycznymi, ale ich wadą jest wysoka cena. W przypadku magnesów ferrytowych ich zaletą jest niska cena, ale wadą słabe właściwości magnetyczne. Proszkowe materiały magnetyczne mogą umożliwić poprawę parametrów eksploatacyjnych urządzeń z obwodami magnetycznymi a jednocześnie pozwolić na obniżenie kosztów ich produkcji. Celem prowadzonych badań jest sprawdzenie możliwości stosowania proszkowych obwodów magnetycznych w produkowanych silnikach elektrycznych prądu stałego z magnesami trwałymi. Przeprowadzono próby zastąpienia tradycyjnego obwodu magnetycznego proszkowym obwodem magnetycznym w silniku prądu stałego typu PRMO 30-5D produkowanym przez fabrykę Mikroma S. A. Badania symulacyjne pokazały, że możliwe jest zastąpienie produkowanego obwodu magnetycznego tego silnika proszkowym obwodem magnetycznym. Obwód magnetyczny wirnika został wykonany z proszku żelaza spajanego tworzywem - dielektromagnetyku, zaś magnesy wzbudzenia z proszku z szybko chłodzonej taśmy Nd-Fe-B spajanej tworzywem - dielektromagnesu (tab. 1). Wykonano modele silników z proszkowymi obwodami magnetycznymi (tab. 2). Przeprowadzono badania wykonanych modeli silników. Na rysunku 1. przedstawiono charakterystyki ruchowe silników. W tabelach 3-5 pokazano wybrane parametry badanych silników, natomiast charakterystyki sterowania na rysunku 2. Przeprowadzone badania pokazały, że stosowanie proszkowych obwodów magnetycznych w maszynach prądu stałego jest możliwe i celowe. Stosowanie tego typu obwodów magnetycznych pozwala na sterowanie parametrami eksploatacyjnymi silników

Temperature and torque measurements of switched reluctance actuator with composite or laminated magnetic cores

Soft magnetic composite (SMC) materials made of iron powder are more frequently used in construction of electric actuators and motors because of their advantages with respect to Fe–Si electric steel sheets and because they have almost no powder loss. The study deals with measurements of temperature and torque of a low-power rotary switched reluctance actuator, with reference to a commercial actuator and a prototype actuator characterized by stator and rotor cores made of soft magnetic composite materials. Further power loss analysis was also conducted. To assess the actuators, magnetization characteristics and iron loss vs. magnetic flux density at a given frequency were measured according to IEC standards. Results show that the actuator made of soft magnetic composites exhibits higher efficiency and a lower temperature rise of stator and windings in comparison with the commercial actuator