Differences In Response Speed Research Articles

Structures, Submodule Topologies and Control Strategies for Modular Multilevel Converter

Global energy demand is rapidly increasing, and the limitations and disadvantages of traditional energy sources are becoming more evident. Traditional energy sources are finite, and their sustainability is facing significant challenges. Compared to traditional multi-level converters, modular multi-level converters (MMC) adopt a modular design that divides the entire converter system into several independent sub-modules, each responsible for converting specific voltage levels. This article provides an overview of the theoretical aspects, topology structures, basic operation principles, and output characteristics of multi-level converters. This paper reviews the characteristics and application ranges of different topology structures, highlighting the differences in response speed, output quality, and control complexity. This paper also discusses the advantages and limitations of multi-level converters in various application scenarios. Explored the application of multi-level converters in wind power grid integration and electric vehicle charging systems, emphasizing their energy-saving and environmentally friendly features. In conclusion, this paper emphasizes the critical role of multi-level converters in power systems and future energy applications, stressing the importance of their reliability and promising future developments.

Active disturbance rejection coordinated control for integrated solar combined cycle system considering system inertia difference

The integrated solar combined cycle system (ISCC) primarily consists of solar thermal power generation equipment and gas turbines. This system effectively mitigates the inherent randomness associated with power generation due to weather conditions while simultaneously providing electric and heat loads. However, due to the difference in response speed of various power generation equipment, it is difficult to respond quickly as the strength of illumination and electricity-heat load demand change, seriously affecting the system's stability operation. This paper proposes an active disturbance rejection control (ADRC) method for the ISCC system considering the different response speeds of generation equipment. Firstly, the mathematical model of the ISCC system is established, in which the system's response speed is improved through the inertial power compensation method. Then, the ADRC method is used to reduce the disturbance caused by uncertain factors, such as solar radiation intensity and load demand change, to ensure the balance between electric and thermal power supply and demand. Finally, based on the measured weather data from National Renewable Energy Laboratory (NREL), the proposed method's performance is evaluated, compared with the hybrid H2/H∞ control method and the auto-coupling proportional integral differential (ACPID) control method. Comparison results show that the ADRC method has better control effectiveness and dynamic response performance, powerfully shortens the system stability time, and reduces overshoot.

Working your CoRe: Further Development of a Mobile Cognitive Assessment Application (P3-3.008)

<h3>Objective:</h3> Assess the suitability of a new version of the CoRe (Cognitive Reaction) test in people with MS (pwMS). <h3>Background:</h3> The UK MS Register(UKMSR) team have previously developed an iPad-based application [Middleton et al 2020] suitable for rapid cognitive assessment in pwMS. The CoRe test was shown to be an adequate proxy for the paper Symbol Digit Modality Test in UK MS Clinics. We have iterated the test, allowing deployment on personal phones and tablets for home-based assessment of cognition. <h3>Design/Methods:</h3> Utilising the existing CoRe test codebase we developed a variant for devices other than iPads. We added additional symbol sets (Emoji and Pictograms) to the existing ‘Classic’ symbols that were generated randomly for pwMS. We removed the ‘next’ symbol from the interface. This version has given to healthy participants and pwMS. <h3>Results:</h3> The initial version was tested in 14 controls and we aim to recruit 1000 pwMS. After one day of release 21 pwMS have returned data. Demographics included 5 men and 16 women, average age 51.9 years and average disease length 22.2 years. People performed similarly to the previous version whether it be on phone or iPad and answered the Emoji symbols faster (0.018). <h3>Conclusions:</h3> The CoRe Version 2 from initial data appears to perform as well as Version 1. There are differences in speed of response depending on the symbol sets chosen. The test appears suitable for use by clinical teams. <b>Disclosure:</b> The institution of Mr. Middleton has received research support from MS Society. Miss Lamptey has nothing to disclose. Jeff Rodgers has nothing to disclose. Elaine Craig has nothing to disclose. Katherine Tuite-Dalton has nothing to disclose. Dr. Nicholas has nothing to disclose.

Visible to Mid-Infrared Photodetector Based on Black Phosphorous-MoS2 Van Der Waals Heterojunction

Van der Waals heterostructures of black phosphorous(BP) and Molybdenum Disulfide(MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) is designed and evaluated for photodetection application from visible to mid-infrared wavelength up to 4.5 μm. The device possesses a low dark current less than 0.1 μA for short wavelength light. For visible and near infrared radiation, the contribution of heat and photo energy to current enhancement is analyzed. Dark current drift by joule heat and laser heat absorbed is observed in short waveband. The difference in response speed is believed to be a result of the competition of BP and MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> photocurrent. Gate tunable response time and on-off ratio makes the device versatile in potential application. For mid infrared radiation, BP-MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> heterojunction with a dedicated thickness tailoring of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> exhibits similar negative response as an intrinsic BP. The normalized detectivity is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${D}^*$</tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2.02 \times {10}^8\ Jones$</tex-math></inline-formula> for the 4.5 μm mid-infrared radiation. Elaborate reduction of the noise is conducted to get the time resolvable photo-response. A low bias is necessary for a time resolved photocurrent, reducing the flicker noise to an acceptable level.

Research on planning optimization of integrated energy system based on the differential features of hybrid energy storage system

At present, it is very important to build the new power system with new energy as the mainstay. Some Regional Integrated Energy Systems (RIES) have installed renewable energy generation equipments with wind turbines and photovoltaics as the main power supply facilities. Due to the volatility in the wind turbine, photovoltaic output power and the customer's electricity load, there is energy waste in the RIES. In order to enhance the economic and renewable energy consumption rate of the park where the RIES is applied, an integrated energy system(IES) planning optimization model is constructed，which considers the mixed storage differentiation characteristics. The model expands the hybrid energy storage system(HESS) on the basis of the original RIES. A two-stage decomposition model combining wavelet packet decomposition method and power decomposition method based on discrete Fourier transform is established, in which the difference between power generation of renewable energy and customer load is decomposed. Depending with the difference in response speed of energy storage devices, the power of different frequencies is moderated. With the comprehensive energy system economy as the goal, the genetic algorithm based on elitist preservation strategy is adopted to optimize the planning model and verify the correctness of the model through simulation. The results show an improvement of 8.23 % and 23.79 % in economy and renewable energy consumption rate compared to the RIES before the HESS expansion.

Smart DIPSS for Dynamic Stability Enchancement on Multi-Machine Power System

Disruption of the electric power system always results in instability. These disturbances can be in the form of network breaks (transients) or load changes (dynamic). Changes in load that occur suddenly and periodically cannot be responded well by the generator so that it can affect the dynamic stability of the system. This causes the occurrence of frequency oscillations in the generator. A poor response can cause frequency oscillations for a long period. This will result in a reduction in the available power transfer power. In a multi-machine power system, all the machines work in synchrony, so the generator must operate at the same frequency. Therefore, disturbances that arise will have a direct impact on changes in electrical power. In addition, changes in electrical power will have an impact on mechanical power. The difference in response speed between a fast electrical power response and a slower mechanical power response will result in instability. As a result of these differences, the system oscillates. The addition of the excitation circuit gain is less able to stabilize the system. To solve the problem, additional signal changes are required. The additional signal is generated by the Dual Input Power System Stabilizer (DIPSS) setting using the Ant Colony Optimization (ACO) method. Disruption of the electric power system always results in instability. These disturbances can be in the form of network breaks (transients) or load changes (dynamic). Changes in load that occur suddenly and periodically cannot be responded well by the generator so that it can affect the dynamic stability of the system. This causes the occurrence of frequency oscillations in the generator. A poor response can cause frequency oscillations for a long period. This will result in a reduction in the available power transfer power. In a multi-machine power system, all the machines work in synchrony, so the generator must operate at the same frequency. Therefore, disturbances that arise will have a direct impact on changes in electrical power. In addition, changes in electrical power will have an impact on mechanical power. The difference in response speed between a fast electrical power response and a slower mechanical power response will result in instability. As a result of these differences, the system oscillates. The addition of the excitation circuit gain is less able to stabilize the system. To solve the problem, additional signal changes are required. The additional signal is generated by the Dual Input Power System Stabilizer (DIPSS) setting using the Ant Colony Optimization (ACO) method.

Coordination control for Integrated Solar Combined Cycle thermoelectric coupling

Improving the utilization of solar energy and promoting the development of integrated energy systems, solar thermal power generation systems are researched and widely used. In the integrated solar combined cycle thermoelectric system, traditional power generation equipment as an auxiliary energy source mitigates fluctuations because of solar energy’s intermittent nature and uncertainty. However, because of the difference in response speed of different power generation equipment, it leads to imbalance of supply and demand power, which affects the smooth operation of the system. This paper proposes a novel coordination control method for integrated solar combined cycle thermoelectric coupling system. To solve the different energy response speed mismatches problem, an inertial power compensation scheme is proposed based on the established solar energy cogeneration system model, and the dynamic performance and robustness of the system are improved. In this paper, the intelligent optimization algorithm is used to optimize the parameters to improve the control precision of the controller. Finally, the paper carries out multi-scenario simulation with the 50MW solar thermal power generation and the 50MW gas turbine to verify the effectiveness and stability of the proposed coordination control method.

Serial Reaction Time Task Performance in Older Adults with Neuropsychologically Defined Mild Cognitive Impairment

Studies have found that individuals with mild cognitive impairment (MCI) exhibit a range of deficits outside the realm of primary explicit memory, yet the role of response speed and implicit learning in older adults with MCI have not been established. The current study aims to explore and document response speed and implicit learning in older adults with neuropsychologically defined MCI using a simple serial reaction (SRT) task. In addition, the study aims to explore the feasibility of a novel utilization of the simple cognitive task using machine learning procedures as a proof of concept. Participants were 22 cognitively healthy older adults and 20 older adults with MCI confirmed through comprehensive neuropsychological evaluation. Two-sample t-test, multivariate regression, and mixed-effect models were used to investigate group difference in response speed and implicit learning on the SRT task. We also explored the potential utility of SRT feature analysis through random forest classification. With demographic variables controlled, the MCI group showed overall slower reaction time and higher error rate compared to the cognitively healthy volunteers. Both groups showed significant simple motor learning and implicit learning. The learning patterns were not statistically different between the two groups. Random forest classification achieved overall accuracy of 80.9%. Individuals with MCI demonstrated slower reaction time and higher error rate compared to cognitively healthy volunteers but demonstrated largely preserved motor learning and implicit sequence learning. Preliminary results from random forest classification using features from SRT performance supported further research in this area.

The temporal structure of the inner retina at a single glance

The retina decomposes visual stimuli into parallel channels that encode different features of the visual environment. Central to this computation is the synaptic processing in a dense layer of neuropil, the so-called inner plexiform layer (IPL). Here, different types of bipolar cells stratifying at distinct depths relay the excitatory feedforward drive from photoreceptors to amacrine and ganglion cells. Current experimental techniques for studying processing in the IPL do not allow imaging the entire IPL simultaneously in the intact tissue. Here, we extend a two-photon microscope with an electrically tunable lens allowing us to obtain optical vertical slices of the IPL, which provide a complete picture of the response diversity of bipolar cells at a “single glance”. The nature of these axial recordings additionally allowed us to isolate and investigate batch effects, i.e. inter-experimental variations resulting in systematic differences in response speed. As a proof of principle, we developed a simple model that disentangles biological from experimental causes of variability and allowed us to recover the characteristic gradient of response speeds across the IPL with higher precision than before. Our new framework will make it possible to study the computations performed in the central synaptic layer of the retina more efficiently.

Does cultural background predict the spatial distribution of attention?

The current study aimed to explore cultural differences in the covert spatial distribution of attention. In particular, we tested whether those born in an East Asian country adopted a different distribution of attention compared to individuals born in a Western country. Previous work suggests that Western individuals tend to distribute attention narrowly and that East Asian individuals distribute attention broadly. However, these studies have used indirect methods to infer spatial attention scale. In particular, they have not measured changes in attention across space, nor have they controlled for differences eye movements patterns, which can differ across cultures. To address this, in the current study, we used an inhibition of return (IOR) paradigm which directly measured changes in attention across space, while controlling for eye movements. The use of the IOR task was a significant advancement, as it allowed for a highly sensitive measure of attention distribution compared to past research. Critically, using this new measure, we failed to observe a cultural difference in the distribution of covert spatial attention. Instead, individuals from East Asian countries and Western countries adopted a similar attention spread. However, we did observe a cultural difference in response speed, whereby Western participants were relatively faster to detect targets in the IOR task. This relationship persisted, even after controlling for individual variation in attention slope, indicating that factors other than attention distribution might account for cultural differences in response speed. Therefore, this study provides robust, converging evidence that group differences in covert spatial attentional distribution do not necessarily drive cultural variation in response speed.

Ribosomal DNA as DAMPs Signal for MCF7 Cancer Cells

Introduction: The cell free ribosomal DNA (cf-rDNA) is accrued in the total pool of cell free DNA (cfDNA) in some non-cancer diseases and demonstrates DAMPs characteristics. The major research questions: (1) How does cell free rDNA content change in breast cancer; (2) What type of response in the MCF7 breast cancer cells is caused by cf-rDNA; and (3) What type of DNA sensors (TLR9 or AIM2) is stimulated in MCF7 in response to the action of cf-rDNA?Materials and Methods: CfDNA and gDNA were isolated from the blood plasma and the cells derived from 38 breast cancer patients and 20 healthy female controls. The rDNA content in DNA was determined using non-radioactive quantitative hybridization. In order to explore the rDNA influence on MCF7 breast cancer cells, the model constructs (GC-DNAs) were applied: pBR322-rDNA plasmid (rDNA inset 5836 bp long) and pBR322 vector. ROS generation, DNA damage, cell cycle, expression of TLR9, AIM2, NF-kB, STAT3, and RNA for 44 genes affecting the cancer cell viability were evaluated. The methods used: RT-qPCR, fluorescent microscopy, immunoassay, flow cytometry, and siRNA technology.Results: The ratio R = cf-rDNA/g-rDNA for the cases was higher than for the controls (median 3.4 vs. 0.8, p < 10−8). In MCF7, GC-DNAs induce a ROS burst, DNA damage response, and augmentation of NF-kB and STAT3 activity. The number of the apoptotic cells decreases, while the number of cells with an instable genome (G2/M– arrest, micronuclei) increase. Expression of anti-apoptotic genes (BCL2, BCL2A1, BCL2L1, BIRC3, MDM2) is elevated, while expression of pro-apoptotic genes (BAX, BID, BAD, PMAIP1, BBC3) is lowered. The cells response for pBR322-rDNA is much more intense and develops much faster, than response for pBR322, and is realized through activation of TLR9- MyD88 - NF-kB- signaling. This difference in response speed is owing to the heightened oxidability of pBR322-rDNA and better ability to penetrate the cell. Induction of TLR9 expression in MCF7 is followed by blocking AIM2 expression.Conclusion: (1) Ribosomal DNA accumulates in cfDNA of breast cancer patients; (2) Cell free rDNA induce DNA damage response and stimulates cells survival, including cells with an instable genome; (3) Cell free rDNA triggers TLR9- MyD88- NF-kB- signaling, with significantly repressing the expression of AIM2.

Cognitive and White-Matter Compartment Models Reveal Selective Relations between Corticospinal Tract Microstructure and Simple Reaction Time.

The speed of motor reaction to an external stimulus varies substantially between individuals and is slowed in aging. However, the neuroanatomical origins of interindividual variability in reaction time (RT) remain unclear. Here, we combined a cognitive model of RT and a biophysical compartment model of diffusion-weighted MRI (DWI) to characterize the relationship between RT and microstructure of the corticospinal tract (CST) and the optic radiation (OR), the primary motor output and visual input pathways associated with visual-motor responses. We fitted an accumulator model of RT to 46 female human participants' behavioral performance in a simple reaction time task. The non-decision time parameter (Ter) derived from the model was used to account for the latencies of stimulus encoding and action initiation. From multi-shell DWI data, we quantified tissue microstructure of the CST and OR with the neurite orientation dispersion and density imaging (NODDI) model as well as the conventional diffusion tensor imaging model. Using novel skeletonization and segmentation approaches, we showed that DWI-based microstructure metrics varied substantially along CST and OR. The Ter of individual participants was negatively correlated with the NODDI measure of the neurite density in the bilateral superior CST. Further, we found no significant correlation between the microstructural measures and mean RT. Thus, our findings suggest a link between interindividual differences in sensorimotor speed and selective microstructural properties in white-matter tracts.SIGNIFICANCE STATEMENT How does our brain structure contribute to our speed to react? Here, we provided anatomically specific evidence that interindividual differences in response speed is associated with white-matter microstructure. Using a cognitive model of reaction time (RT), we estimated the non-decision time, as an index of the latencies of stimulus encoding and action initiation, during a simple reaction time task. Using an advanced microstructural model for diffusion MRI, we estimated the tissue properties and their variations along the corticospinal tract and optic radiation. We found significant location-specific correlations between the microstructural measures and the model-derived parameter of non-decision time but not mean RT. These results highlight the neuroanatomical signature of interindividual variability in response speed along the sensorimotor pathways.

Differences in Speed of Response of Depressive Symptom Dimensions in Older Persons During Electroconvulsive Therapy.

Electroconvulsive therapy (ECT) is an important and effective treatment for depression. However, research on course trajectories of depressive symptoms during ECT is limited. Insight into putative differences in speed of response of depressive symptom dimensions may enable clinicians to optimally inform patients and their relatives. Therefore, we aim to examine course trajectories of depressive symptom dimensions in depressed older persons during ECT. Data were derived from the Mood Disorders in Elderly treated with Electro Convulsive Therapy study, including 110 persons, aged 55 years or more, with a current diagnosis of major depressive disorder and referred for ECT. Exploratory factor analysis was used to identify symptom dimensions, using the 10 depression items of the Montgomery-Åsberg Depression Rating Scale (MADRS). Differences in course trajectories of symptom dimension during 2 weeks were examined by multilevel analyses. Three symptom dimensions were identified: a "mood," "melancholic," and "suicidal" dimension. Mood showed a significantly greater severity decline as compared with melancholic and suicidal at the 1-week follow-up. At the 2-week follow-up, both mood and melancholic demonstrated a significantly greater decline as compared with suicidal. However, because scores on the suicidality item of the Montgomery-Asberg Depression Rating Scale were already lower at baseline compared with the other items, a floor effect cannot be ruled out. All symptom dimensions of depression showed a rapid response to ECT. Our findings did not support the general assumption that suicidal symptoms may be the first to improve. However, a floor effect on the suicidality item cannot be ruled out.

The influence of blood phenylalanine levels on neurocognitive function in adult PKU patients.

It is well known that hyperphenylalaninemia caused by phenylketonuria (PKU) negatively influences cognitive performance. Several tests have been used to study these functions. Until now, no universal, optimal tool has been developed for detecting PKU-caused brain dysfunctions. Using computerized neuropsychological tests during daily routine would be helpful for screening subclinical brain deficits in adult PKU patients. In a monocentric, cross-sectional study, adult patients with PKU (n = 46; median age = 29.5years; female/male ratio = 21/25) were tested with the computerized Cambridge Cognition (CANTAB) test measuring neurocognitive functions. Patients were divided into two groups: The "on diet" group included patients whose blood Phe-level was under 600μmol/l (n = 20), and the "loose diet" group included patients whose blood Phe-level was above 600μmol/l (n = 26) at the examination time. The results of the PKU-affected individuals were compared with a healthy control group (n = 31; median age = 25years; female/male ratio = 11/20). Compared with the control group, PKU patients had significantly worse test results in memory, problem-solving skills, and strategy. However, there were no significant differences in response speed or initial thinking time. There was no correlation between the blood Phe-level, tyrosine (Tyr)-level or Phe/Tyr ratio and the different cognitive test results. There were no significant differences in test results between the two PKU subgroups. Several cognitive functions measured by CANTAB are negatively influenced by hyperphenylalaninemia in adult PKU patients. However, response speed and initial thinking time were not impaired as seriously as other functions. Patients with lower Phe-levels failed to achieve better test results than patients whose Phe-levels were notably elevated.

Verbal and spatial working memory among drug-using HIV-infected men and women.

Working memory (WM) is a critical component of many neurocognitive functions. The literature has demonstrated consistently that WM impairment is more frequent and severe among substance-dependent individuals (SDIs) infected with HIV compared with uninfected SDIs; however, the SDIs who participated in these previous studies were primarily male. There are few published data on WM performance among HIV+ women with or without substance use disorders, and essentially no direct comparisons of WM performance between HIV+ men and women, regardless of substance use. We investigated potential sex and serostatus effects on WM among a sample of 360 SDIs (114 with HIV; 66% female) verified abstinent from alcohol and drugs of abuse at testing and generally comparable on substance use and comorbid characteristics. Participants were tested with the n-back task, a well-established WM measure that is sensitive to HIV-associated cognitive impairment. HIV+ men and women performed spatial and verbal versions of the n-back significantly less accurately compared with HIV- participants. Women showed slower response times compared with men on both versions, regardless of HIV serostatus. Individuals dependent on cocaine showed faster RTs compared with non-dependent users, but this effect was not apparent among opioid- or alcohol-dependent groups. Findings on n-back accuracy are consistent with our previous proposal that WM impairment represents a signature deficit among HIV+ SDIs; however, WM impairment appears less common among HIV+ women without a substance use history. The pattern of sex differences in response speed but serostatus effects on response accuracy is comparable to a recent report by our group of sex differences in learning speed but serostatus effects on delayed recall.

Comparison of electro-optical switching between polymer-stabilised cubic and amorphous blue phases

We prepared polymer-stabilised cubic and amorphous blue phase liquid crystals consisting of the same materials at different UV-curing temperatures using photopolymerisation. Then we investigated the effects of polymer stabilisation on their physical properties. The UV-curing temperature does not affect phase stabilisation of the polymer-stabilised amorphous BPIII (PS-BPIII). Temperatures of the PS-BPIII were found to be extended to more than 50 K. However, a critical temperature exists in the polymer stabilisation process for the PS-cubic BP. Although no substantial difference in response speed was found between the polymer-stabilised cubic and amorphous structures, larger hysteresis and higher residual birefringence were observed in the PS-cubic BP than in the PS-BPIII. Amorphous BPIII with an amorphous network of disclination lines has no critical temperature for the polymer stabilisation and realises a high-performance display.

Individual differences in response speed and accuracy are associated to specific brain activities of two interacting systems.

The study investigates the neurocognitive stages involved in the speed-accuracy trade-off (SAT). Contrary to previous approach, we did not manipulate speed and accuracy instructions: participants were required to be fast and accurate in a go/no-go task, and we selected post-hoc the groups based on the subjects’ spontaneous behavioral tendency. Based on the reaction times, we selected the fast and slow groups (Speed-groups), and based on the percentage of false alarms, we selected the accurate and inaccurate groups (Accuracy-groups). The two Speed-groups were accuracy-matched, and the two Accuracy-groups were speed-matched. High density electroencephalographic (EEG) and stimulus-locked analyses allowed us to observe group differences both before and after the stimulus onset. Long before the stimulus appearance, the two Speed-groups showed different amplitude of the Bereitschaftspotential (BP), reflecting the activity of the supplementary motor area (SMA); by contrast, the two Accuracy-groups showed different amplitude of the prefrontal negativity (pN), reflecting the activity of the right prefrontal cortex (rPFC). In addition, the post-stimulus event-related potential (ERP) components showed differences between groups: the P1 component was larger in accurate than inaccurate group; the N1 and N2 components were larger in the fast than slow group; the P3 component started earlier and was larger in the fast than slow group. The go minus no-go subtractive wave enhancing go-related processing revealed a differential prefrontal positivity (dpP) that peaked at about 330 ms; the latency and the amplitude of this peak were associated with the speed of the decision process and the efficiency of the stimulus-response mapping, respectively. Overall, data are consistent with the view that speed and accuracy are processed by two interacting but separate neurocognitive systems, with different features in both the anticipation and the response execution phases.

Cognitive function during low-intensity walking: a test of the treadmill workstation.

The purpose of this study was to examine the effects of walking at self-selected speed on an active workstation on cognitive performance. Sixty-six participants (n = 27 males, 39 females; mean age = 21.06 ± 1.6 years) completed a treadmill-desk walking and a seated control condition, separated by 48 hours. During each condition, participants completed computerized versions of the Stroop test, a modified flanker task, and a test of reading comprehension. No significant differences in response speed or accuracy were found between walking and sitting conditions for any the cognitive tests. These findings reveal that performance on cognitive tasks, including executive control processes, are not impaired by walking on an active workstation. Implementing active workstations into offices and classrooms may help to decrease sedentariness without impairing task performance.

Timing matters: Age-related changes in episodic retrieval control as revealed by event-related potentials

The retrieval of information from episodic memory involves the engagement of pre-retrieval control processes that facilitate the recovery of task-relevant information. The development of these processes was investigated here by comparing neural correlates of retrieval orientation between 13–14-year-old adolescents and young adults. In each age group, event-related potentials (ERPs) elicited by new test pictures were contrasted across two recognition memory tasks (specific vs. general retrieval tasks), which were designed to place greater demands on the recovery of perceptual information associated with each picture in the specific than in the general task. Memory accuracy was higher in the general than in the specific task but did not differ between age groups. In adults, new item ERPs at anterior sites were more positive going in the specific than in the general task from 400 to 1200ms. In adolescents, the onset latency of this effect was delayed by 300ms relative to adults, even though no age differences in response speed were obtained in either task. The magnitude of the ERP new item effect in adults correlated with response accuracy, consistent with the view that pre-retrieval processes facilitate the recovery of task-relevant information. For adolescents, this relationship was only obtained for a subset of participants with early onsetting ERP effects, supporting the claim that the influence of pre-retrieval processes depends upon their temporal onset. Together, the findings suggest age-related changes in the efficiency of using control processes to facilitate successful retrieval while highlighting the role of onset latency in mediating these changes.

Maternal Thyroxine and Fetal Brain Development: The Latest Chapter, a Look Back, and Considerations for the Future

Defining the relationship between maternal hypothyroxinemia during early pregnancy (free T4 [FT4] 10th centile) and offspring neurocognitive development is an ongoing challenge to those exploring the biology of maternal-fetal interactions in search of opportunities for improving neurocognitive function. Although not yielding a definitive characterization of this relationship, the report by Finken et al (1) in this issue of the JCEM represents an important step forward. Studies of this type are labor-intensive and require a considerable investment of time and organizational skill. The authors enrolled a large cohort of women during early pregnancy, collected baseline demographics, performed thyroid testing, and then monitored outcome as part of the Amsterdam Born Children and their Development (ABCD) study. When offspring of those women reached the age of 5 years, the investigators measured various aspects of neurocognitive function via a computerized assessment program. Application of a computerized measurement tool in this context allowed all responses to be determined objectively. Several features of this study add confidence to its conclusions: 1) the study was community-based; 2) TSH, FT4, and thyroperoxidase (TPO) antibody measurements were performed early in pregnancy; 3) children were tested at an age when results are reliable; 4) numbers of children tested were sufficient to detect important differences; 5) testing was blinded and carried out by trained investigators in a school setting; 6) the computerized assessment tool provided objective performance measurements; and 7) the ABCD study collected extensive demographics and biophysical data that were available for use in regression analyses. Computerized assessment consisted of 4 tasks. The 175 children of hypothyroxinemic mothers performed significantly less well only on the first task (baseline speed, a simple reaction time test that required minimal cognitive effort). The other 3 tasks measured visuomotor coordination, inherent response inhibition, and response flexibility. On these latter 3 tasks, children of hypothyroxinemic mothers did not perform differently from the remaining children. For the first task, however, their mean response speed was 41.3 milliseconds slower than that of 1584 children whose mothers’ FT4 levels were above the 10th centile. Each child performed this task 32 times with each hand, allowing the standard deviation of response speed to be measured as well. This was also significantly greater, indicating more instability in performing the task repeatedly. The difference in response speed remained significant after adjustment for multiple variables. Furthermore, the slowing of response speed was more pronounced when limited to children of mothers with FT4 levels fifth centile. Finally, mean reaction time was even longer among 44 children of mothers whose FT4 measurements were 10th centile and whose TSH measurements were 90th centile. Given that children of hypothyroxinemic mothers performed the other 3 tasks satisfactorily, the longer term developmental implications are unclear, although documentation of the slower response speed was convincing. In addition to reporting neurocognitive data, this study highlights maternal characteristics that segregate at the population level with low FT4. The higher mean body mass index among hypothyroxinemic women, for example, has been documented in several other studies (2–6),