Fast Responding Research Articles

Age differences in strategic behavior during a computation-based skill acquisition task.

The authors evaluated mechanistic and metacognitive accounts of age differences in strategy transitions during skill acquisition. Old and young participants were trained on a task involving a shift from performing a novel arithmetic algorithm to responding via associative recognition of equation-solution pairings. The strategy shift was manipulated by task instructions that either (a) equally focused on speed and accuracy, (b) encouraged retrieval use as a method toward fast responding, or (c) offered monetary incentives for fast retrieval-based performance. Monetary incentives produced a more rapid shift to retrieval relative to standard instructions; older adults showed a greater incentives effect on retrieval use than younger adults. Monetary incentives encouraged retrieval use and response time improvements despite accuracy costs (a speed-accuracy tradeoff). The pattern of results suggested a role of metacognitive and volitional factors in retrieval shift, indicating that an associative learning deficit cannot fully account for older adults' delayed strategy shift.

Commentaires sur la neuroéconomie

Comments on Neuroeconomics. Neuroeconomics is examined critically using data on the response times of subjects who were asked to express their preferences in the context of the Allais Paradox. Different patterns of choice are found among the fast and slow responders. This suggests that we try to identify types of economic agents by the time they take to make their choices. Nevertheless, it is argued that it is far from clear if and how neuroeconomics will change economics.

COMMENTS ON NEUROECONOMICS

Neuroeconomics is examined critically using data on the response times of subjects who were asked to express their preferences in the context of the Allais Paradox. Different patterns of choice are found among the fast and slow responders. This suggests that we try to identify types of economic agents by the time they take to make their choices. Nevertheless, it is argued that it is far from clear if and how neuroeconomics will change economics.

Nanometal-Decorated Exfoliated Graphite Nanoplatelet Based Glucose Biosensors with High Sensitivity and Fast Response

We report the novel fabrication of a highly sensitive, selective, fast responding, and affordable amperometric glucose biosensor using exfoliated graphite nanoplatelets (xGnPs) decorated with Pt and Pd nanoparticles. Nafion was used to solubilize metal-decorated graphite nanoplatelets, and a simple cast method with high content organic solvent (85 wt %) was used to prepare the biosensors. The addition of precious metal nanoparticles such as platinum (Pt) and palladium (Pd) to xGnP increased the electroactive area of the electrode and substantially decreased the overpotential in the detection of hydrogen peroxide. The Pt-xGnP glucose biosensor had a sensitivity of 61.5+/-0.6 microA/(mM x cm(2)) and gave a linear response up to 20 mM. The response time and detection limit (S/N=3) were determined to be 2 s and 1 microM, respectively. Therefore, this novel glucose biosensor based on the Pt nanoparticle coated xGnP is among the best reported to date in both sensing performance and production cost. In addition, the effects of metal nanoparticle loading and the particle size on the biosensor performance were systematically investigated.

Brain correlates of early auditory processing are attenuated by expectations for time and pitch

The present study investigated how auditory processing is modulated by expectations for time and pitch by analyzing reaction times and event-related potentials (ERPs). In two experiments, tone sequences were presented to the participants, who had to discriminate whether the last tone of the sequence contained a short gap or was continuous (Experiment 1: go/nogo, Experiment 2: choice reaction). Expectations were induced by varying the temporal and pitch regularity of the sequence. Results were consistent across both experiments. Expectations for both time and pitch were associated with faster responding. Both temporal and pitch expectations led to an attenuation of the auditory N1, thus indicating a modulation of early, perceptual processing by temporal and pitch expectations. Effects of temporal expectations were also evident in a P300-like deflection, suggesting that temporal expectations also affect decision- or response-related processing stages.

Immune regulatory cells: circulating biomarker factories in cardiovascular disease

TLRs (Toll-like receptors) are the first line of defence of the innate immune system. These receptors recognize not only exogenous but also endogenous ligands that are expressed following arterial injury and atherosclerotic disease. Expression of TLR2 and TLR4 is observed in macrophages and different vascular cells and is increased in atherosclerotic disease. It is suggested that TLR expression and functional responsiveness following ligation could serve as biomarkers for atherosclerotic disease progression. Recently published research papers support the concept that the TLRs are fast responders upon arterial injury. In the present issue of Clinical Science, Ishikawa and co-workers provide new evidence emerges that points to the potential prognostic properties of the TLRs.

Differential Expression of Interleukin-4 (IL-4) and IL-4δ2 mRNA, but Not Transforming Growth Factor Beta (TGF-β), TGF-βRII, Foxp3, Gamma Interferon, T-bet, or GATA-3 mRNA, in Patients with Fast and Slow Responses to Antituberculosis Treatment

This study investigated interleukin-4 (IL-4), IL-4 delta 2, transforming growth factor beta (TGF-beta), TGF-beta RII, Foxp3, GATA-3, T-bet, and gamma interferon (IFN-gamma) transcription in peripheral blood samples of adult pulmonary tuberculosis patients prior to and after 1 week of therapy. Twenty patients with positive results for sputum culture for Mycobacterium tuberculosis were enrolled and treated with directly observed short-course antituberculosis chemotherapy. Early treatment response was assessed. At the end of the intensive phase of treatment (month 2), 12 patients remained sputum culture positive (slow responders) and 8 converted to a negative culture (fast responders). Only the expression levels of IL-4 (4-fold decrease) and IL-4 delta 2 (32-fold increase) changed significantly during the first week of therapy in the 20 patients. No baseline differences were present between the responder groups, but fast responders had significantly higher IL-4 transcripts than slow responders at week 1. Fast responders showed a 19-fold upregulation and slow responders a 47-fold upregulation of IL-4 delta 2 at week 1. Only slow responders also showed a significant decrease in IL-4 expression at week 1. There were no significant differences in expression of TGF-beta, TGF-beta RII, Foxp3, IFN-gamma, and GATA-3 between the groups. These data show that differential IL-4-related gene expression in the early stage of antituberculosis treatment accompanies differential treatment responses and may hold promise as a marker for treatment effect.

Immune parameters as markers of tuberculosis extent of disease and early prediction of anti-tuberculosis chemotherapy response

This study investigates how the extent of pre-treatment radiological disease and early anti-tuberculous treatment response affect levels of selected circulating host immune markers. Twenty HIV-uninfected tuberculosis patients with BACTEC culture positivity for Mycobacterium tuberculosis at diagnosis and treated with directly observed short course anti-tuberculosis chemotherapy and 13 healthy community controls were enrolled. Serum samples were collected throughout treatment. After the intensive phase of treatment, 12 patients remained sputum culture-positive (slow responders) and eight patients were culture negative (fast responders). C-reactive protein (CRP), soluble intercellular adhesion molecule-1 (sICAM-1), soluble urokinase plasminogen activator receptor (suPAR), soluble lymphocyte activation gene-3 (sLAG-3), granzyme B, soluble tumour necrosis factor receptor one and two (sTNFR I and sTNFR II) and soluble death receptor 5 (sDR5) concentrations were measured. High levels of CRP at diagnosis were found to be associated (p</=0.05) with the presence of multiple cavities on chest x-rays and high levels of suPAR and sICAM-1 at diagnosis were associated (p</=0.05) with the extent of alveolar disease. Also significant were the associations between the level of granzyme B (p</=0.01) and LAG-3 (p</=0.05) at diagnosis, and the size of the cavities. The combination of diagnosis and week one measurements of selected serological markers in mathematical models was able to identify the fast responders with up to 87.5% accuracy and the slow responders with up to 83.3% accuracy These preliminary results suggest that predictive models for differential early treatment responses using combinations of host markers hold promise.

Prediction of virologic response in difficult-to-treat chronic hepatitis C patients during high-dose interferon induction therapy

Objective. To determine (i) whether early viral kinetics or other markers during a modified treatment regimen are predictors of treatment outcome and (ii) whether fast responders can be treated for 24 weeks, without compromising the sustained virologic response (SVR) rate. Material and methods. One hundred “difficult-to-treat” chronic hepatitis C patients (46 previous non-responders/relapsers (any genotype), 54 treatment-naive patients genotypes 1 and 4) were treated with triple antiviral induction therapy: amantadine hydrochloride and ribavirin, combined with 6 weeks interferon alfa-2b induction (weeks 1–2: 18 MU/day, weeks 3–4: 9 MU/day, weeks 5–6: 6 MU/day), thereafter combined with weekly peginterferon alfa-2b. Fast responders (≥3 log10 HCV RNA decline at week 4) were randomized to 24 or 48 weeks. Slow responders (<3 log10 HCV RNA decline at week 4) were treated for 48 weeks. Treatment was stopped in patients with detectable HCV RNA at week 24. Results. Thirty-six patients achieved SVR: 28 of 60 fast responders (47%) versus 8 of 32 slow responders (25%, p<0.05). Relapse rates among fast responders treated for 24 or 48 weeks were 27% and 20%, respectively (p=NS). SVR in fast responders was independent of baseline HCV RNA ≥ or <600,000 IU/mL. All treatment-naive patients with HCV RNA <5 IU/mL at week 1 or 2 achieved SVR; all treatment-naive patients with HCV RNA ≥5 IU/mL at week 16 became non-SVR. In previous non-responders/relapsers, the predictive value for SVR was 83% if HCV RNA was <5 IU/mL at week 2; all previous non-responders/relapsers with HCV RNA ≥5 IU/mL at week 8 became non-SVR. Conclusions. With high-dose interferon induction, SVR and non-SVR can be predicted reliably within 16 weeks. Fast responders can be treated for 24 weeks, and SVR is independent of baseline viral load in fast responders.

Fast responders have blinders on: ERP correlates of response inhibition in competition

Recent studies have demonstrated that individuals acting in a social context form shared representations, resulting in incorporating another person's action plan into their own. The present study investigated the extent to which shared representations are formed in a competitive task. Specifically, it was tested whether in competition the process of response inhibition is affected by explicit knowledge of another's task. Event-related potential (ERP) correlates of response inhibition were measured while pairs of participants competed with each other on a speeded go/no-go task. Participants were instructed to always try to respond faster than their direct competitor. No-go stimuli requiring an inhibitory response of the other person as well (compatible action) or no-go stimuli to which the other person should respond (incompatible action) were directly compared. Behavioral performance measures and response inhibition, as reflected in the no-go P3, were decreased on incompatible actions compared to compatible ones. Interestingly, both the behavioral and the ERP effects were caused by the slow responding and thus unsuccessful competitors. These findings indicate that shared representations are formed in competitive tasks, but differently for successful and unsuccessful competitors. Only the slow responders are impeded by incompatible actions. The present study therefore demonstrates that the formation of shared representations is not a fully automatic process. People can differ in the extent to which they incorporate the other's action plan into their own and this may be closely related to successful performance in competitive action.

Energy equalizing routing for fast data gathering in wireless sensor networks

Energy saving and fast responding of data gathering are two crucial factors for the performance of wireless sensor networks. A dynamic tree based energy equalizing routing scheme (DTEER) was proposed to make an effort to gather data along with low energy consumption and low time delay. DTEER introduces a dynamic multi-hop route selecting scheme based on weight-value and height-value to form a dynamic tree and a mechanism similar to token passing to elect the root of the tree. DTEER can simply and rapidly organize all the nodes with low overhead and is robust enough to the topology changes. When compared with power-efficient gathering in sensor information systems (PEGASIS) and the hybrid, energy- efficient, distributed clustering approach (HEED), the simulation results show that DTEER achieves its intention of consuming less energy, equalizing the energy consumption of all the nodes, alleviating the data gathering delay, as well as extending the network lifetime perfectly.

Functional Anatomy of Humor: Positive Affect and Chronic Mental Illness

Functional Anatomy of Humor: Positive Affect and Chronic Mental Illness

Categorical perception of colour in the left and right visual field is verbally mediated: Evidence from Korean

In this study we demonstrate that Korean (but not English) speakers show Categorical perception (CP) on a visual search task for a boundary between two Korean colour categories that is not marked in English. These effects were observed regardless of whether target items were presented to the left or right visual field. Because this boundary is unique to Korean, these results are not consistent with a suggestion made by Drivonikou [Drivonikou, G. V., Kay, P., Regier, T., Ivry, R. B., Gilbert, A. L., Franklin, A. et al. (2007) Further evidence that Whorfian effects are stronger in the right visual field than in the left. Proceedings of the National Academy of Sciences 104, 1097–1102] that CP effects in the left visual field provide evidence for the existence of a set of universal colour categories. Dividing Korean participants into fast and slow responders demonstrated that fast responders show CP only in the right visual field while slow responders show CP in both visual fields. We argue that this finding is consistent with the view that CP in both visual fields is verbally mediated by the left hemisphere language system.

Application of PID controller to 2D differential geometric guidance problem

This paper presents the application of the proportional-integral-derivative (PID) controller to the flight control system (FCS) for two-dimensional (2D) differential geometric (DG) guidance and control problem. In particular, the performance of the designed FCS is investigated. To this end, the commanded angle-of-attack is firstly developed in the time domain using the classical DG formulations. Then, the classical PID controller is introduced to develop a FCS so as to form the 2D DG guidance and control system, and the PID controller parameters are determined by the Ziegler-Nichols method as well as the Routh-Hurwitz stability algorithm to guarantee the convergence of the system error. The results demonstrate that the designed controller yields a fast responding system, and the resulting DG guidance and control system is viable and effective in a realistic missile defense engagement.

Impact of Early Viral Kinetics on T-Cell Reactivity during Antiviral Therapy in Chronic Hepatitis B

The patterns of hepatitis B viral dynamics during different antiviral therapies and the associated changes in HBV-specific T-cell reactivity are not well defined. We investigated the impact of early viral load decline on virus-specific T-cell reactivity in 30 hepatitis B e antigen (HBeAg)-positive patients with chronic hepatitis B randomized to monotherapy with adefovir dipivoxil (ADV) or in combination with emtricitabine (ADV/FTC). Viral kinetics were analysed by mathematical modelling. T-cell reactivity to HBV core and/or surface antigens and natural killer T cell frequency were tested longitudinally, baseline to week 48, using EliSPOT assays and/or flow cytometry. Mathematical modelling of early HBV kinetics identified two subsets of patients: 11 fast responders (undetectable viraemia by week 12; eight on ADV/FTC three on ADV) and 19 slow responders who remained viremic (six on ADV/FTC 13 on ADV). The rate of infected hepatocyte loss was higher in fast than in slow responders (P = 0.0007), and correlated inversely with pre-treatment levels of intrahepatic covalently closed circular HBV DNA. The frequency of HBV core-specific CD4+ T-cells increased significantly only in fast responders, peaking between week 16 and 24, while the HBV surface-specific CD4+ T-cells increased in both subsets. These changes in CD4+ T-cell reactivity were transient however, and no increase in HBV-specific CD8+ T-cells was observed. By week 48, HBeAg seroconversion occurred only in 3/30 (10%) patients. Early viraemia clearance facilitates recovery of virus-specific CD4+ T-cell reactivity, but appears insufficient to establish clinically relevant antiviral immunity.

The Neural Consequences of Semantic Richness

Some concepts have richer semantic representations than others. That is, when considering the meaning of concepts, subjects generate more information (more features, more associates) for some concepts than for others. This variability in semantic richness influences responses in speeded tasks that involve semantic processing, such as lexical decision and semantic categorization tasks. It has been suggested that concepts with richer semantic representations build stronger attractors in semantic space, allowing faster settling of activation patterns and thus faster responding. Using event-related functional magnetic resonance imaging, we examined the neural activation associated with semantic richness by contrasting activation for words with high and low numbers of associates in a semantic categorization task. Results were consistent with faster semantic settling for words with richer representations: Words with a low number of semantic associates produced more activation than words with a high number of semantic associates in a number of regions, including left inferior frontal and inferior temporal gyri.

Moderation of Older Adults' Retrieval Reluctance Through Task Instructions and Monetary Incentives

Previous research using a noun-pair lookup task indicates that older adults delay strategy shift from visual scanning to memory retrieval despite adequate learning, and that this "retrieval reluctance" is related to subjective choice factors. Age differences in spontaneous response criteria, with older adults valuing accuracy and young adults valuing speed, might account for this phenomenon. The present experiment manipulates instructions and reward contingencies to test the flexibility of response criteria and strategy preferences. Task instructions conditions equally focused on speed and accuracy, encouraged retrieval use as a method toward fast responding, or offered monetary incentives for fast retrieval-based performance. Results indicate that older adults in the incentives condition shifted to retrieval earlier than those without incentives, bolstering the argument that reliance on retrieval is volitional.

Cost, Benefit, Tonic, Phasic

The role of dopamine in decision making has received much attention from both the experimental and computational communities. However, because reinforcement learning models concentrate on discrete action selection and on phasic dopamine signals, they are silent as to how animals decide upon the rate of their actions, and they fail to account for the prominent effects of dopamine on response rates. We suggest an extension to reinforcement learning models in which response rates are optimally determined by balancing the tradeoff between the cost of fast responding and the benefit of rapid reward acquisition. The resulting behavior conforms well with numerous characteristics of free-operant responding. More importantly, this framework highlights a role for a tonic signal corresponding to the net rate of rewards, in determining the optimal rate of responding. We hypothesize that this critical quantity is conveyed by tonic levels of dopamine, explaining why dopaminergic manipulations exert a global affect on response rates. We further suggest that the effects of motivation on instrumental rates of responding are mediated through its influence on the net reward rate, implying a tight coupling between motivational states and tonic dopamine. The relationships between phasic and tonic dopamine signaling, and between directing and energizing effects of motivation, as well as the implications for motivational control of habitual and goal-directed instrumental action selection, are discussed.

Heligmosomoides polygyrus: Decreased apoptosis in fast responder FVB mice during infection

Primary infection with Heligmosomoides polygyrus in some strains of mice is chronic although fast responder mouse strains eliminate the parasite in a short period of time. The reason for the differences is unknown. In this study apoptosis, proliferation, IL-2 and IL-6 production of mesenteric lymph node (MLN) and spleen cells in vitro from fast (FVB) and slow (C57Bl/6) responder mice were compared during H. polygyrus infection. FVB cells showed decreased apoptosis, more proliferation and more cytokine production than cells from C57Bl/6 mice during infection. At the beginning of infection in C57Bl/6 mice the apoptosis of CD4 + but not CD8 + cells significantly increased in MLN and spleen cell cultures. Apoptosis, when the first immune signal is given by infective larvae, might play an important role in the modulation of the response in slow responder mice.

Differential effects of modafinil and methylphenidate on stop-signal reaction time task performance in the rat, and interactions with the dopamine receptor antagonist cis-flupenthixol

The stop-signal reaction time (SSRT) task measures inhibition of a response that has already been initiated, i.e. the ability to stop. 'Impulsive' human subjects, e.g. with attention deficit and hyperactivity disorder (ADHD), have longer SSRTs. Both SSRT and go-trial reaction time (GoRT) may be sensitive to drugs such as d-amphetamine, methylphenidate and modafinil, both in normal subjects and those with ADHD. To investigate the effects of modafinil (3, 10, 30 and 100 mg/kg) and methylphenidate (0.3, 1.0 and 3.0 mg/kg) on SSRT task performance in the rat. To investigate the possible contribution of dopamine receptors in the action of these drugs using the mixed D1/D2 dopamine receptor antagonist cis-flupenthixol. Modafinil significantly decreased SSRT with little effect on GoRT but only in rats with slow baseline SSRTs. Fast SSRTs were not changed by modafinil. Methylphenidate decreased GoRTs of all rats. However, methylphenidate had baseline-dependent effects on SSRT, decreasing SSRT in slow responders but increasing SSRT in fast responders. Cis-flupenthixol (0.01, 0.04 and 0.125 mg/kg) had no effects on SSRT but increased GoRT at higher doses. At the lowest dose (0.01 mg/kg), cis-flupenthixol failed to disrupt the SSRT-decreasing effects of either modafinil or methylphenidate, whereas at 0.04 mg/kg, the cis-flupenthixol-dependent increase in GoRT was antagonised by methylphenidate but not by modafinil. This evidence supports a hypothesis that stop and go processes are under control of distinct neurochemical mechanisms.