Optimization of α-Hydroxyketone and Pyrazine Syntheses Employing Preliminary Reactions of Glucose and Buffer Solutions

Summary An array of pyrazines have been synthesized using sugars derived from tobacco cellulose (CDS), ammonium hydroxide, and hydrolyzed tobacco F1 protein as a source of free amino acids (isolated amino acids from F1 hydrolysate, from filtered F1 hydrolysate and from non-filtered F1 hydrolysate). All reactions were performed at 120 °C for 60 min using a 40-mL Parr reaction vessel. Results showed that the addition of hydrolyzed F1 protein as free amino acid source increased the number of pyrazines with branched alkyl chains (for example, 2-butyl-3-methyl pyrazine) compared to when no amino acids were added. However, using isolated amino acids from hydrolyzed F1 protein versus just hydrolyzed F1 protein (filtered or not filtered) did not make a difference in yield or type of branched pyrazines. When non-filtered hydrolyzed F1 protein was used, the solution was much more viscous and contained suspended solid material when compared to the use of filtered hydrolyzed F1 protein. Addition of threonine (THR) to the reaction mixture did not increase the yield of pyrazines but did slightly shift the distribution of pyrazines toward those with three and four carbons attached. Similar but not identical arrays of pyrazines were obtained when somewhat resembling reaction conditions were applied on a larger reaction scale (~1.5 L). A significant 50%-decrease in pyrazine yield was observed when the reaction temperature was reduced from 120 to 100 °C. No noticeable difference in the array of pyrazines from these two reactions was observed. In the majority of cases, the presence of free amino acids resulted in an increase in pyrazine yield coupled with a change in the qualitative array of pyrazines. These results clearly illustrate that sugar prepared from tobacco cellulose (glucose) can be used just like high fructose corn syrup to prepare flavor compounds via Amadori and Maillard reactions. The evidence highlights that hydrolyzed amino acids from F1 tobacco protein can be used via Maillard reactions to produce complementary arrays of pyrazine flavor compounds.

Effects of Stimulant Medication, Incentives, and Event Rate on Reaction Time Variability in Children With ADHD

Attention deficit hyperactivity disorder (ADHD) shows a strong phenotypic and genetic association with reaction time (RT) variability, considered to reflect lapses in attention. Yet we know little about whether this aetiological pathway is shared with other affected cognitive processes in ADHD, such as lower IQs or the generally slower responses (mean RTs). We aimed to address the question of whether a shared set of genes exist that influence RT variability, mean RT, IQ and ADHD symptom scores, or whether there is evidence of separate aetiological pathways. Multivariate structural equation modelling on cognitive tasks data (providing RT data), IQ and ADHD ratings by parents and teachers collected on general population sample of 1314 twins, at ages 7-10 years. Multivariate structural equation models indicated that the shared genetic influences underlying both ADHD symptom scores and RT variability are also shared with those underlying mean RT, with both types of RT data largely indexing the same underlying liability. By contrast, the shared genetic influences on ADHD symptom scores and RT variability (or mean RT) are largely independent of the genetic influences that ADHD symptom scores share with IQ. The finding of unique aetiological pathways between IQ and RT data, but shared components between mean RT, RT variability and ADHD symptom scores, illustrates key influences in the genetic architecture of the cognitive and energetic processes that underlie the behavioural symptoms of ADHD. In addition, the multivariate genetic model fitting findings provide valuable information for future molecular genetic analyses.

A new approach to the epoxidation of natural rubber through a sonochemical method

Encoding of stimulus identity, memory, and reward expectation in monkey perirhinal cortex during delayed conditioning

BackgroundCognitive theories of attention-deficit/hyperactivity disorder (ADHD) propose that high within-subject fluctuations of cognitive performance in ADHD, particularly reaction time (RT) variability (RTV), may reflect arousal dysregulation. However, direct evidence of arousal dysregulation and how it may account for fluctuating RTs in ADHD is limited. We used skin conductance (SC) as a measure of peripheral arousal and aimed to investigate its phenotypic and familial association with RTV in a large sample of ADHD and control sibling pairs. MethodsAdolescents and young adults (N = 292), consisting of 73 participants with ADHD and their 75 siblings, and 72 controls and their 72 siblings, completed the baseline (slow, unrewarded) and fast-incentive conditions of a RT task, while SC was simultaneously recorded. ResultsA significant group-by-condition interaction emerged for SC level (SCL). Participants with ADHD had decreased SCL, compared with controls, in the baseline condition but not the fast-incentive condition. Baseline SCL was negatively associated with RTV, and multivariate model fitting demonstrated that the covariance of SCL with RTV, and of SCL with ADHD, was mostly explained by shared familial effects. ConclusionsADHD is associated with decreased, but modifiable, tonic peripheral arousal. A shared familial cause underlies the relationship between arousal and RTV and between arousal and ADHD. Given the malleability of SCL, if our findings are replicated, it warrants further exploration as a potential treatment target for ADHD.

Hydrothermal synthesis of mono-dispersed quartz powders

Reaction time (RT) variability is one of the strongest findings to emerge in cognitive-experimental research of attention deficit hyperactivity disorder (ADHD). We set out to confirm the association between ADHD and slow and variable RTs and investigate the degree to which RT performance improves under fast event rate and incentives. Using a group familial correlation approach, we tested the hypothesis that there are shared familial effects on RT performance and ADHD. A total of 144 ADHD combined-type probands, 125 siblings of the ADHD probands and 60 control participants, ages 6-18, performed a four-choice RT task with baseline and fast-incentive conditions. ADHD was associated with slow and variable RTs, and with greater improvement in speed and RT variability from baseline to fast-incentive condition. RT performance showed shared familial influences with ADHD. Under the assumption that the familial effects represent genetic influences, the proportion of the phenotypic correlation due to shared familial influences was estimated as 60-70%. The data are inconsistent with models that consider RT variability as reflecting a stable cognitive deficit in ADHD, but instead emphasize the extent to which energetic or motivational factors can have a greater effect on RT performance in ADHD. The findings support the role of RT variability as an endophenotype mediating the link between genes and ADHD.

Daytime sleepiness is associated with impaired attention processes, including slower and more variable reaction time. Although results are mixed, recent research has started to show the positive association between insomnia severity, greater daytime sleepiness and impaired simple attention processes. In this study, we aimed to determine whether performance on an attention task influences self-reported sleepiness of individuals across the sleep disturbance spectrum. Participants (N=50) included individuals across the insomnia spectrum from good sleepers to patients with insomnia disorder. Insomnia severity was assessed using the Insomnia Severity Index. Simple attention was assessed using a computerized Psychomotor Vigilance Test (PC-PVT) administered in the morning. Participants’ rated their sleepiness on a scale from 1 (not sleepy) to 10 (extremely sleepy) before and after they completed the PVT. Spearman’s correlation coefficient was used to assess associations between insomnia severity, sleepiness, and PVT performance. Multiple regression was used to determine whether mean or trial-to-trial variability in reaction time predicted post-PVT sleepiness, adjusting for pre-PVT sleepiness and Insomnia Severity Index score. Greater trial-to-trial variability in PVT reaction time predicted greater post-PVT sleepiness after adjusting for pre-PVT sleepiness and insomnia severity, t=2.9, p=0.005. Insomnia symptom severity was associated with greater sleepiness at pre- and post-PVT, rs (50)=0.41, p=0.003 for both. After adjusting for pre-PVT sleepiness, insomnia severity was not a significant predictor of post-PVT sleepiness. Average PVT reaction time was not associated with sleepiness. Participants with greater inconsistency in simple attention performance reported greater sleepiness than they had reported 10 minutes previously. Trial-to-trial variability in reaction time performance may have raised participants’ awareness of their sleepiness. Alternatively, participants with inconsistent performance may have altered their self-report to match their performance. Although insomnia symptom severity was associated with sleepiness it did not make participants more prone to biased sleepiness reports based on performance on the PVT. N/A

Reaction time (RT) and RT variability are core components of cognitive performance that can be captured through brief and easy-to-administer tasks of simple RT and choice RT. The current study aims to describe age-related differences in cognitive performance, toward better characterizing normative performance across the lifespan. We examined mean and variability of response times on a simple RT and choice RT tasks in a large and diverse web-based sample (10,060 visitors to TestMyBrain.org). We also examined lifespan-related differences in response time variability using multiple different approaches (raw variability, mean scaled variability, and mean residualized variability). These analyses revealed significant heterogeneity in the patterns of age-related differences in performance, across metrics and within different estimates of the same metric. Based on segmented regression analysis, age of peak performance differed significantly across metrics, with young adults having the best performance based on measures of median RT, middle age adults at peak on certain measures of RT variability (standard deviation and coefficient of variability), and older adults showing the best performance based on accuracy and mean-corrected RT variability. Our results indicate that no single measure of cognitive performance and performance variability produces the same findings with respect to age related change, with further work needed to establish the validity of particular metrics for different applications.

Reaction time variability in ADHD: A meta-analytic review of 319 studies

Aliphatic unsegmented polyurethanes (PUs) have garnered relatively limited attention in the literature, despite their valuable properties such as UV resistance and biocompatibility, making them suitable for biomedical applications. This study focuses on synthesizing poly(ester-urethanes) (PEUs) using 1,6-hexamethylene diisocyanate and the macrodiol α,ω-hydroxy telechelic poly(ε-caprolactone) (HOPCLOH). To optimize the synthesis, a statistical experimental design approach was employed, a methodology not commonly utilized in polymer science. The influence of reaction temperature, time, reagent concentrations, and solvent type on the resulting PEUs was investigated. Characterization techniques included FT-IR, 1H NMR, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), optical microscopy, and mechanical testing. The results demonstrated that all factors significantly impacted the number-average molecular weight (Mn) as determined by GPC. Furthermore, the statistical design revealed crucial interaction effects between factors, such as a dependence between reaction time and temperature. For example, a fixed reaction time of 1 h, with the temperature varying from 50 °C to 61 °C, did not significantly alter Mn. Better reaction conditions yielded high Mn (average: 162,000 g/mol), desirable mechanical properties (elongation at break > 1000%), low levels of unreacted HOPCLOH in the PEU films (OH/ESTER response = 0.0008), and reduced crystallinity (ΔHm = 11 J/g) in the soft segment, as observed by DSC and optical microscopy. In contrast, suboptimal conditions resulted in low Mn, brittle materials with unmeasurable mechanical properties, high crystallinity, and significant amounts of residual HOPCLOH. The best experimental conditions were 61 °C, 0.176 molal, 8 h, and chloroform as the solvent (ε = 4.8).

To investigate whether intraindividual variability (IIV) in reaction time (RT) over monthly administered cognitive tasks is increased in cognitively unimpaired older adults who are at risk for cognitive decline, and whether this is independent of mean RT performance. N = 109 cognitively unimpaired individuals (age 77.4 ± 5.0, 61.5% female, Mini-Mental State Examination 29.1 ± 1.3) from the Harvard Aging Brain Study completed the self-administered Computerized Cognitive Composite (C3) monthly at home for up to 1 year (12.7 ± 3.2 C3 assessments). Baseline C3 assessment coincided with routine in-clinic visits, including amyloid and tau positron emission tomography imaging and standardized cognitive testing, with cognitive testing repeated annually (1.6 ± 1.2 years follow-up). The C3 includes two simple RT tasks and two complex RT tasks. IIV estimates were derived by computing intraindividual standard deviations on residual RT scores after regressing out age and session order effects. Cross-sectional associations of IIV with cognition (global cognition, memory, executive functions [EF], processing speed) and amyloid and tau burden were examined using linear regression analyses correcting for demographics and mean RT. The association between IIV and cognitive decline was assessed using linear mixed models correcting for demographic factors, mean RT, and amyloid burden. After adjusting for mean RT, increased IIV on complex RT tasks was independently associated with worse EF performance (β = -0.10, 95% CI [-.16, -0.03], p = .004), greater inferior-temporal tau deposition (β = 0.18, 95% CI [0.02, 0.34], p = .024), and faster cognitive decline in those with elevated amyloid (β = -0.62, 95% CI [-1.18, -0.06], p = .033). Increased variability in monthly RT may reflect subtle EF deficits and provide unique information about short-term cognitive decline in preclinical Alzheimer's disease. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Purpose: Many reports have indicated that patients with temporal lobe epilepsy display a variety of cognitive impairments. The delay of reaction time is one of these impairments. However, it has been suggested that most of the tests used to measure cognitive function, such as reaction time, are influenced by motor speed. To clarify this ques‐ tion, we measured reaction times and carried out a Finger Tapping Test (FTT) in patients and controls, and differences in reaction time between these groups were analyzed after the motor speed component was removed. To avoid the influence of difference in stimulation and test difficulty, we measured 3 different reaction times. In addition, we investigated relationships between performance on these tasks and clinical characteristics to clarify factors related to these impairments. Methods: The subjects were 21 patients with temporal lobe epilepsy (mean age 31.8 years: mean duration of illness 14.5 years) and 11 normal controls (mean age 31.2years). All patients had received AEDs. All subjects were examined by auditory simple reaction time, visual simple reaction time, visual choice reaction time, and FTT. Student's t test was applied to each variable across the 2 groups. Analysis of covariance was then applied, by which the variance in reaction times between the 2 groups that could be attributed to the most simple measure of motor speed (FTT) was factored out. Spearman's correlation analysis was applied to investigate relationships between performance on these tasks and clinical characteristics Resulrs: Performance on all 3 reaction times, including auditory simple reaction time (p<0.05), visual simple reaction time (p<O.O1), and visual choice reaction time (p<0.05), were longer in patients than controls. FTT yielded a significant (p<O.O1) inter‐group difference. When the variance in reaction times attributable to a simple measure of motor speed were factored out, differences in performance on visual simple reaction time (F=5.51, p<0.05) and in performance on visual choice reaction time (F=3.88, p<O.I) persisted. There was a significant positive correlation between performance on the FTT and seizure frequency (rs=O.48, p<0.05), as well as dosage of AEDs (rs= 0.65, p<O.Ol). Conclusions: Our results suggest that the delayed reaction time in patients with temporal lobe epilepsy was not only due to reduction of motor speed but also due to impairment of other cognitive processes. It is generally accepted that many patients have some kind of cognitive impairments and many factors such as seizure, epileptic discharge, AEDs, and others may influence cognitive function. In present study it is indicated that delayed reaction time is due to several cognitive processes. Impairments of motor speed may have a relation to seizure frequency and dosage of AEDs. Several prior reports have indicated that some AEDs affect motor function. Our findings may reflect such a relationship.

Executive function, particularly behavioral inhibition, has been implicated as a core deficit specific to Attention-Deficit/Hyperactivity Disorder (ADHD) whereas rapid naming has been implicated as a core deficit specific to reading disabilities (RD). Females may be less impaired in executive function although adolescent females with ADHD have yet to be studied. Neuropsychological profiles of four adolescent groups aged 13-16 with equal female representation were investigated: 35 ADHD, 12 RD, 24 ADHD+RD, and 37 normal controls. A semi-structured interview (K-SADS-PL), the Conners Rating Scales and the Ontario Child Health Study Scales were used to diagnose ADHD. RD was defined as a standard score below 90 on at least one of the following: Reading or Spelling of the WRAT3 or Word Attack or Word Identification of the WRMT-R. The WISC-III, Rapid Automatized Naming, Stroop and Stop tasks were used as measures of cognitive and executive function. The two ADHD groups (ADHD, ADHD+RD) showed deficits in processing speed, naming of objects, poor behavioral inhibition and greater variability in reaction times whereas the two RD groups (RD, RD+ADHD) showed verbal working memory deficits and slower verbal retrieval speed. Only the comorbid group was slower with naming of numbers and colors and had slower reaction times. Regression analyses indicated that incongruent color naming (Stroop) and variability in go reaction time were the best predictors of hyperactive/impulsive ADHD symptoms whereas variability in go reaction time and processing speed were the best predictors of inattentive ADHD symptoms. Speed of letter naming and verbal working memory accounted for the most variability in composite achievement scores. No gender differences were found on any of the cognitive tests. This study challenges the importance of behavioral inhibition deficits in ADHD and that naming deficits are specific to RD. Further investigation into cognitive deficits in these groups is required.