Response Time Curves Research Articles

P‐175: Quantitative Analysis of LCD Motion Ghosting Based on Visual Perception Model

In order to analyze the motion ghosting phenomenon on liqu id crystal displays (LCDs), a motion block artifact simulation model based on response time (RT) curves is established usin g human visual perception theory. By calculating the brightn ess integral, the presence and degree of the Rebound pheno menon are quantified. Furthermore, based on the quantified changes in RT curves at different frames, the mechanism of Rebound generation is analyzed and improvement measures a re proposed.

Reward-predicting distractor orientations support contextual cueing: Persistent effects in homogeneous distractor contexts

Recent work on contextual cueing has shown that reward can facilitate context learning, e.g., when salient but task-irrelevant context features signal reward magnitude. Whether task-relevant context features yield a similar facilitating effect is unclear. Also, emergence and persistence of context learning for contexts associated with different reward magnitudes remains unclear. The present study investigated whether reward increases the speed with which context learning emerges, resulting in an earlier but asymptotically similar contextual cueing effect, or whether reward persistently increases context learning, visible as a larger contextual cueing effect on an asymptotical level. Reward was associated to the predominant orientation of the L-distractors, and the number of context repetitions was increased considerably. Results showed contextual cueing, i.e., faster responses and fewer fixations in repeated compared to novel contexts for all reward magnitudes. Moreover, a high reward led to a more pronounced contextual cueing effect. We developed a model-based approach to explicitly assess the non-linear decline and asymptotic level of the response time curves and to quantify how they were altered by reward. A hierarchical Bayesian parameter estimation revealed that reward decreased the asymptotic level of the repeated contexts’ response times. Our results therefore show that reward leads to a persistent advantage in contextual cueing rather than to earlier but asymptotically similar context learning.

A critical reexamination of doing arithmetic nonconsciously.

A recent study claimed to have obtained evidence that participants can solve invisible multistep arithmetic equations (Sklar et al., 2012). The authors used a priming paradigm in which reaction times to targets congruent with the equation's solution were responded to faster compared with incongruent ones. We critically reanalyzed the data set of Sklar et al. and show that the claims being made in the article are not fully supported by the alternative analyses that we applied. A Bayesian reanalysis of the data accounting for the random variability of the target stimuli in addition to the subjects shows that the evidence for priming effects is less strong than initially claimed. That is, although Bayes factors revealed evidence for the presence of a priming effect, it was generally weak. Second, the claim that unconscious arithmetic occurs for subtraction but not for addition is not supported when the critical interaction is tested. Third, the data do not show well-established features of numerosity priming as derived from V-shaped response time curves for prime-target distances. Fourth, we show that it is impossible to classify reaction times as resulting from congruent or incongruent prime-target relationships, which should be expected if their results imply that participants genuinely solve the equations on each trial. We conclude that the claims being made in the original article are not fully supported by the analyses that we apply. Together with a recent failure to replicate the original results and a critique of the analysis based on regression to the mean, we argue that the current evidence for unconscious arithmetic is inconclusive. We argue that strong claims require strong evidence and stress that cumulative research strategies are needed to provide such evidence.

Interplay between order-parameter and system parameter dynamics: considerations on perceptual-cognitive-behavioral mode-mode transitions exhibiting positive and negative hysteresis and on response times.

A mathematical model is presented for the emergence of perceptual-cognitive-behavioral modes in psychophysical experiments in which participants are confronted with two alternatives. The model is based on the theory of self-organization and, in particular, the order parameter concept such that the emergence of a mode is conceptualized as an instability leading to the emergence of an appropriately defined order parameter. The order parameter model is merged with a second model that describes adaptation in terms of a system parameter dynamics. It is shown that the two-component model predicts hysteretic mode-mode transitions when control parameters are increased or decreased beyond critical values. The two-component model can account for both positive and negative hysteresis effects due to the interaction between order parameter and system parameter dynamics. Moreover, the model-based analysis reveals that response time curves look rather flat when response times are relatively decoupled from the mode-mode transition phenomenon. In general, response time curves exhibit a peaked close to the mode-mode transition point. In this context, the possibility is discussed that such peaked response time curves belong to the class of critical phenomena of self-organizing systems. In order to illustrate the relevance of peaked response time curves for future research and research reported in the past, results from a perceptual judgment experiment are reported, in which participants judged their ability to stand on a tilted slope for various angles of inclination. Response time curves were found that exhibited a peak around the mode-mode-transition points between "yes" and "no" responses.

The Elastic Dynamic Analysis of Crawler Crane Boom System

According to mechanical characteristics of space truss structure, the dynamic characteristics of boom system of crawler crane in derricking condition are simulated based on positional FEM. FEM simplified analytical method is established basing on engineering algorithm, only a few units and small amount of calculation are needed when using variable cross-section beam to simulate boom integral structure. The dynamic response time curves of boom system in derricking conditions are obtained, and compared with the existing literature. This further confirms the simplified model is feasible in theory and easy to realize in engineering, it also shows that positional FEM is feasible in dynamic analysis of complex structure.

Characterization and Development of the Ideal Pedal Force, Pedal Travel, and Response Time in the Brake System for the Translation of the Voice of the Customer to Engineering Specifications

It is a well-known fact that braking is one of the most important factors in customer satisfaction and a key factor in the voice of the customer (VOC). The VOC has to be translated into engineering specifications in due course and various methods have been developed. Current engineering specifications utilize only a few discrete points on the pedal force (PF), pedal travel (PT), and response time (RT) curves owing to the multi-dimensional nature of these curves, and thus may not represent the entire curves well. Principal component analysis (PCA) is applied in order to analyse the entire shapes of the three curves and to identify the underlying variation modes. Then, buyer satisfaction scores from a mail survey are regressed on the variation modes. Finally, the ideal shapes of the PF, PT, and RT curves are developed for the sport segment, the coupé and sedan segment, and the truck segment to aid new brake system and vehicle design. Translating the VOC from marketing research into engineering specifications is a critical step and PCA is a valuable tool for this translation.

A functional magnetic resonance imaging study of human brain in pain-related areas induced by electrical stimulation with different intensities

Pain-related studies have mainly been performed through traditional methods, which lack the rigorous analysis of anatomical locations. Functional magnetic resonance imaging (fMRI) is a noninvasive method detecting neural activity, and has the ability to precisely locate related activations in vivo. Moreover, few studies have used painful stimulation of changed intensity to investigate relevant functioning nuclei in the human brain. This study mainly focused on the pain-related activations induced by electrical stimulation with different intensities using fMRI. Furthermore, the electrophysiological characteristics of different pain-susceptible-neurons were analyzed to construct the pain modulatory network, which was corresponding to painful stimulus of changed intensity. Twelve volunteers underwent functional scanning receiving different electrical stimulation. The data were collected and analyzed to generate the corresponding functional activation maps and response time curves related to pain. The common activations were mainly located in several specific regions, including the secondary somatosensory cortex (SII), insula, anterior cingulate cortex (ACC), thalamus, and other cerebral regions. Moreover, innocuous electrical stimulation primarily activated the lateral portions of SII and thalamus, as well as the posterior insula, anterior ACC, whereas noxious electrical stimulation primarily activated the medial portions of SII and thalamus, as well as the anterior insula, the posterior ACC, with larger extensions and greater intensities. Several specified cerebral regions displayed different response patterns during electrical stimulation by means of fMRI, which implied that the corresponding pain-susceptible-neurons might process specific aspects of pain. Elucidation of functions on pain-related regions will help to understand the delicate pain modulation of human brain.

Influence of Ethanol and Gender on Methylphenidate Pharmacokinetics and Pharmacodynamics

This study explores the hypotheses that: (1) ethanol will interact with dl-Methylphenidate (MPH) to enantioselectively elevate plasma d-MPH, and primarily yield l-ethylphenidate as a transesterification metabolite; (2) women will exhibit lower relative bioavailability of MPH than men; and (3) sex-dependent differences in subjective effects will exist. dl-MPH HCl (0.3 mg/kg) was administered orally 30 min before ethanol, 30 min after ethanol (0.6 gm/kg), or without ethanol, in a randomized, normal subject three-way crossover study of 10 men and 10 women. Pharmacokinetic parameters were compared. Subjective effects were recorded using visual analog scales. One subject was a novel poor MPH metabolizer whose data were analyzed separately. Ethanol after or before MPH significantly (P<0.0001) elevated the geometric mean for the maximum d-MPH plasma concentration (C(max) (+/-SD)) from 15.3 (3.37) ng/ml to 21.5 (6.81) and 21.4 (4.86), respectively, and raised the corresponding geometric mean for the area under the concentration-time curve values from 82.9 (21.7) ng ml/h to 105.2 (23.5) and 102.9 (19.2). l-MPH was present in plasma only at 1-3% of the concentration of d-MPH, except in the poor metabolizer where l-MPH exceeded that of d-MPH. The metabolite l-ethylphenidate frequently exceeded 1 ng/ml in plasma, whereas d-ethylphenidate was detected only in low pg/ml concentrations. Women reported a significantly greater stimulant effect than men when questioned "Do you feel any drug effect?" (P<0.05), in spite of lower mean plasma d-MPH area under the response-time curves in women. Ethanol elevates plasma d-MPH C(max) and area under the concentration-time curve by approximately 40% and 25%, respectively. If the poor metabolizer of MPH proves to be a distinct phenotype, determining the genetic mechanism may be of value for individualizing drug therapy. The more pronounced stimulant effects experienced by women have sex-based abuse liability implications.

Mechanistic model of acute autoinhibitory feedback action after administration of SSRIs in rats: Application to escitalopram-induced effects on brain serotonin levels

This study presents the development and evaluation of a feedback turnover model that mimics drug-induced effects on brain extracellular levels of serotonin (5-HT) after acute administration of the selective serotonin reuptake inhibitor (SSRI) escitalopram ( S-citalopram) in rats. The extracellular 5-HT output in the hippocampus was continuously monitored by intracerebral microdialysis in conjunction with serial arterial blood sampling for evaluation of escitalopram pharmacokinetics. 5-HT levels were significantly increased following administration of 2.5, 5 and 10 mg/kg of escitalopram and the 5-HT levels gradually declined to its baseline value within 360 min. However, at 5 and 10 mg/kg, the response–time curves were almost identical. This might be explained by activation of serotonergic autoreceptors exerting negative feedback, leading to a reduced release of new 5-HT into the synapse. The dynamics of escitalopram-evoked changes of 5-HT response was characterized by a turnover model, which included an inhibitory feedback moderator component. Thus, the response acted linearly on the production of the moderator, which acted inversely on the production of response. The plasma kinetics served as input to an inhibitory function acting on the loss of response. Simultaneous fitting of the model after three constant rate infusions demonstrated the flexibility of the system. The efficacy ( I max) and potency (IC 50) of inhibition of reuptake were 0.9 ± 0.03 and 4.4 ± 1.4 ng/ml, respectively, corresponding to an EC 50 of escitalopram about 30 ng/ml. In conclusion, the model lends itself to ‘what–if’ predictions at different drug exposure scenarios, and has potential for extrapolation of the pharmacodynamics of SSRIs in man.

Efficient approximation of response time densities and quantiles in stochastic models

Response time densities and quantiles are important performance and quality of service metrics, but their analytical derivation is, in general, very expensive. This paper presents a technique for determining approximate response time densities in Markov and semi-Markov stochastic models that requires two orders of magnitude less computation than exact Laplace transform-based techniques. The method computes the first four moments of the desired response time and then makes use of Generalised Lambda Distributions to obtain an approximation of the corresponding density. Numerical results show good agreement over a range of response time curves, particularly for those that are unimodal.

Modelling and experimental study of the transient behaviour of plant tissue sensors in sensing dopamine

A chemical sensor is a device for measuring low concentrations of chemical solutes in a solution. Four different plant tissue sensors were used to measure the concentration of dopamine in aqueous solution. A mathematical model describing their transient characteristics was developed and experimentally verified. The rate parameters of the sensing process were determined by combining the present transient-state model with the analytical solution of a previously reported steady-state model. This combined approach simplified significantly the numerical solution of the transient-state model from a five to a two unknown parameters problem. A total of 285 transient response-time curves containing 34,911 data points were obtained experimentally with four different tissue powder dopamine sensors over a wide range of operating conditions. One hundred and ninety of them containing 18,573 data points were used for the numerical regression analysis and evaluation of the rate parameters. The remaining 95 sets were compared with the results predicted by the model using the regressed rate parameters. Good correlation and prediction were obtained confirming the adequacy of the model in describing the transient behavior of the biosensors and also the effectiveness of the combined models approach in the computation. The results facilitate the optimum design and fabrication of such sensors.

Modelling and experimental study of the transient behaviour of plant tissue sensors in sensing dopamine

A chemical sensor is a device for measuring low concentrations of chemical solutes in a solution. Four different plant tissue sensors were used to measure the concentration of dopamine in aqueous solution. A mathematical model describing their transient characteristics was developed and experimentally verified. The rate parameters of the sensing process were determined by combining the present transient-state model with the analytical solution of a previously reported steady-state model. This combined approach simplified significantly the numerical solution of the transient-state model from a five to a two unknown parameters problem. A total of 285 transient response-time curves containing 34,911 data points were obtained experimentally with four different tissue powder dopamine sensors over a wide range of operating conditions. One hundred and ninety of them containing 18,573 data points were used for the numerical regression analysis and evaluation of the rate parameters. The remaining 95 sets were compared with the results predicted by the model using the regressed rate parameters. Good correlation and prediction were obtained confirming the adequacy of the model in describing the transient behavior of the biosensors and also the effectiveness of the combined models approach in the computation. The results facilitate the optimum design and fabrication of such sensors.

The effects of remoxipride and chlorpromazine on eye movements and psychomotor performance in healthy volunteers

Fifteen healthy male volunteers received single doses of 100 mg immediate release remoxipride (IR), 150 mg controlled release remoxipride (CR), 50 mg chlorpromazine (CPZ), 2 mg lorazepam (LZ), and placebo in a randomised, five-period cross-over study. Both saccadic (SEM) and smooth pursuit eye movements (SPEM) as well as a battery of psychomotor performance tests were assessed at 1.5-h intervals over 9 h following drug administration. The areas under the response-time curves and the maximum effect during the study period were analysed by analysis of variance. The most consistent impairments were produced by LZ. The neuroleptics caused impairments to SEM, and tended to impair critical flicker fusion, continuous attention and both paced and unpaced versions of the digit-symbol substitution test as well as subjective measures of sedation. Only LZ impaired SPEM. Neither paced nor unpaced psychomotor tests distinguished between neuroleptics and benzodiazepines. The low therapeutic doses of IR and CR produced similar impairments to a sub-therapeutic dose of CPZ. Selectivity of pharmacological action does not appear to predict selectivity of effect on psychomotor function.

Modeling alphabetic retrieval: Rejoinder to Klahr (1994).

In D. Klahr's (1994) reply to J. Scharroo, E. Leeuwenberg, P. F. M. Stalmeier, and P. G. Vos (1994), he ignored the basic critique on the hierarchy in D. Klahr, W. G. Chase, and E. Lovelace's (1983) model of alphabetic retrieval. In this rejoinder, I discuss the modeling of alphabetic retrieval and the shape of response time (RT) curves with respect to the strong and weak tests and the alphabetic position effect. From discussion of these 2 points, it should be clear why D. Klahr (1994) did not deal with the main objections raised in J. Scharroo et al. (1994): (a) D. Klahr et al.'s (1983) RT curves did not show the predicted sawtooth shape and (b) there was no reason to assume an additional level (Level 1) in modeling alphabetic retrieval

Performance of solid-membrane cation-selective electrodes for flow-injection potentiometry

The dynamic behaviour of solid-membrane Ag, Cu, Pb and Cd ion-selective electrodes (ISEs) as detectors in a flow-injection potentiometric system is described. The predominant role of the dynamic response-time characteristics of the sensors on the potentiometric signal is emphasized. When the value of the dynamic response time τ is smaller than the contact time Δ t of the injected primary ion solution zone with the electrode surface, a transient signal is detected and thus τ dramatically affects the linear working range, the electrode response slope and the detection limit. The selectivity properties of the sensors are also dependent on the contact time and usually the potentiometric selectivity coefficients increase with increasing Δ t. In each case, the optimal physical parameters of the flow manifold can be chosen beforehand from the dynamic response-time curves recorded with a given electrode.

Response Time Curves of Neutral Carrier Membrane Electrode of Tubular Shape

Abstract A tubular flow-through electrode system for measuring the response time curves under the step change of concentration using an ammonium ion-selective poly(vinyl chloride) membrane electrode was described. The response time data are analyzed by the curve fitting method using two theoretical equations, which are an exponential type equation based on an assumption of the film diffusion and a square root type one based on that of the diffusion within the membrane, and a semiempirical equation of hyperbolic type. A method of curve fitting in which the equilibrium potential is regarded as an unknown parameter was described in detail. The initial part of the response time curves, where the potential change is large, was fitted by the exponential type equation, while the following part close to the equilibrium potential was fitted by the square root type one. The semiempirical equation could also be fitted to the wide range of the curves. The dependence of the time constant of the exponential type equation upon the flow rate of sample solution is examined; the results firmly supports both the film diffusion as a determining process for the initial part of the curve and the reliability of the present experimental system.

RESPONSE TIME CURVES OF AMMONIUM ION-SELECTIVE ELECTRODE OF TUBULAR SHAPE

In order to reproducibly measure response time curves of a poly (vinyl chloride) matrix membrane ammonium ion-selective electrode, an experimental setup composed of a tubular flow-through electrode was constructed. The data were analyzed by the curve fitting method using two theoretical equations, that based on the assumption of the film diffusion and that of the diffusion within the membrane.

Response time curves of ion-selective electrodes

Response time curves of ion-selective electrodes

Evidence for Variable Digoxin Absorption as Estimated by Pharmacological Response Intensities

A dose-effect curve constructed from ventricular rate slowing and oral maintenance doses for digoxin provided evidence for assuming that occupation theory correctly describes drug-receptor site interaction. From the tenets of occupation theory, response intensities were linearly related to biophasic drug levels and provided the input for bi- and triexponential least-squares fits for an intravenously administered 1.2-mg dose of digoxin to patients hospitalized with auricular fibrillation. A biexponential fit best described biophasic drug levels when the biophase was represented by a peripheral compartment. Intravenous biexponential equation parameters were utilized to perform an absorption analysis following oral dosing of 1.2mg of digoxin to the same patients. From calculations of fractional amounts unabsorbed with time, significant absorption of digoxin was found to be occurring through 24hr at progressively decreasing but noticeably variable rates; absorption was calculated to be 98.7% complete by 120hr. Absorption rates were most rapid over the first 5hr but quite variable thereafter. Oscillations in the intravenous and oral response-time curves, observed between 3 and 12hr following dosing, likewise produced fluctuations in mathematically derived biophasic drug levels, fractional amounts unabsorbed, and absorption rates for the oral dose, suggesting enterohepatic cycling of digoxin to be more significant than previously thought.

Kinetics of pharmacologic response I. Proposed relationships between response and drug concentration in the intact animal and man

An equation is proposed that may often be used to relate the intensity of a pharmacologic response to the concentration of drug in the body fluids of the intact animal or man. Concentrations which are substituted into the equation will usually be those predicted from a mathematical model which has been elaborated from observed drug concentrations. Hypothetical examples of response-time curves are shown. The one compartment open model system is examined extensively, and some interesting relationships of the integral of response to variables are shown. The limitations of estimating rate constants of elimination from plots of duration of response against the logarithm of the dose are indicated. Use of the equation to explain observed data is discussed.