Duration discrimination: A diffusion decision modeling approach.

The human ability to discriminate the duration of two subsequently presented stimuli is often studied with tasks that involve a comparison between a standard stimulus (with fixed duration) and comparison stimuli (with varying durations). The performance in such tasks is influenced by the presentation order of these successively presented stimuli. The so-called Type A effect refers to the impact of presentation order on the point of subjective equality. The Type B effect describes effects of presentation order on the just-noticeable-difference. Cognitive models that account for these context effects assume that participants' duration estimation is influenced by the history of previously encountered stimuli. For example, the internal reference model assumes that the magnitude of a "typical" stimulus is represented by an internal reference. This internal reference evolves throughout an experiment and is updated on every trial. Different recent models have in common that they describe how the internal reference is computed but are agnostic to the decision process itself. In this study, we develop a new model that incorporates the mechanisms of perceptual discrimination models into a diffusion model. The diffusion model focuses on the dynamics of the decision process itself and accounts for choice and response times based on a set of latent cognitive variables. We show that our model accurately predicts the accuracy and response time distribution in a classical duration discrimination task. Further, model parameters were sensitive to the Type A and B effect. The proposed model opens up new opportunities for studying human discrimination performance (e.g., individual differences).

Parámetros para la evaluación visual e instrumental del color dental en estudios in-vitro. Revisión de la literatura / Parameters for visual and instrumental assessment of tooth colour in in-vitro studies. Literature review

Objetivo: establecer los parámetros para la evaluación visual e instrumental del color dental en estudios in-vitro a partir de la literatura científca publicada entre 2015 y 2021. Métodos: se realizó la búsqueda en las bases de datos: PubMed, Web of Science, Science Direct, Scopus, Scielo y Lilacs; también en el motor de búsqueda Google Académico y las bibliotecas de las editoriales Wiley y Springer. Las palabras clave utilizadas fueron tooth, color, in-vitro, color perception, shade matching, thresholds, appearance, surrounding, "CIELAB" y "CIEDE2000". Teniendo en cuenta los criterios de elegibilidad, se seleccionaron los estudios de acuerdo al título, resumen y texto completo. Resultados: la búsqueda arrojó un total de 37 publicaciones que se agruparon en tres tópicos: 1. toma de color visual: condiciones ambientales, observadores y nivelación; 2. toma de color instrumental: instrumentos; y 3. procesamiento de datos: cálculo de la diferencia de color y umbrales de perceptibilidad (PT) y aceptabilidad (AT). Conclusiones: los aspectos más importantes en la evaluación visual son la iluminación, el ambiente para registro (sitio, entorno y fondo alrededor de la muestra), las condiciones geométricas de visualización, los observadores y el uso de guías. En la evaluación instrumental es relevante elegir el aparato apropiado de acuerdo con su precisión y reproducibilidad, como los espectroradiómetros y los espectrofotómetros de uso clínico. Se presenta el procesamiento de datos para establecer las variaciones de cada coordenada, las diferencias de color (ΔE): CIELAB y CIEDE2000, los umbrales y los lineamientos.

Objective: To establish the parameters for the visual and instrumental evaluation of tooth color in in-vitro studies based on the scientifc literature published between 2015 and 2021. Methods: The search was carried out in the databases of PubMed, Web of Science, Science Direct, Scopus, Scielo, Lilacs; search engine Google Scholar and publishers' library of Wiley and Scielo, using the keywords "tooth", "color", "in vitro", "color perception", "shade matching", "thresholds", "appearance", "surrounding", "CIELAB", and "CIEDE2000". The literature was selected according to the title, abstract and full text taking into the eligibility criteria. Results: It yielded a total of 37 publications, which were grouped into three topics: 1. visual color acquisition: environmental conditions for color acquisition, observers and levelling. 2. instrumental color sampling: instruments. 3. Data processing: Calculation of color diference and perception thresholds (PT) and acceptability thresholds (AT). Conclusions: The most important aspects in the visual assessment are lighting, the environment for color registration (site, environment and background around the sample), the geometric conditions of visualization, the observers and the use of guides. Regarding the instrumental assessment of color, the appropriate devices must be chosen according to its precision and reproducibility, being the spectrophotometers and spectroradiometers the most precise ones. It is presented how the data processing is carried out to establish the variations of each coordinate, the color diferences (ΔE): CIELAB and CIEDE2000, thresholds and guidelines.

Assessment of the difference limens for frequency, monosyllable articulation and word intelligibility by distantly-presented bone-conducted ultrasound.

Ultrasound can be clearly perceived by bone-conduction, and this "bone-conducted ultrasound (BCU)" can transmit speech information by using amplitude modulation (AM). Further, BCU can be perceived not only on the head but also on the distal parts of the body like the neck, trunk and arms. This "distantly-presented BCU" can be applied to the novel interface that can transmit sound information selectively to specific users who touches the vibrator. However, the ability to transmit sound information of distantly-presented BCU is unclear. First, to assess frequency discrimination ability, difference limens for frequency (DLFs) of the distantly-presented AM-BCU were measured with/without a low-pass masking noise that masked the self-demodulated components generated by the nonlinearity of biological tissues. DLFs comparable to that of air-conducted sounds were observed, whereas DLFs significantly increased above 1 kHz under the masking condition. These results suggest that practical frequency discrimination ability can be obtained even when BCUs were presented to distal body parts. Additionally, it is indicated that the demodulated components may contribute to transmitting frequency information above 1 kHz. Second, monosyllable articulation and word intelligibility tests were conducted in Japanese. The intelligibility and articulation at the neck were 55% and 38% respectively, whereas they decreased as the stimulus placement gets farther from the head. The results suggest the distantly-presented BCU device can be applied to transmission of speech information.

Feasibility of objective assessment of difference limen for intensity using acoustic change complex in children with central auditory processing disorder.

INTRODUCTION: Acoustic change complex (ACC) shows brain's ability to discriminate between acoustic features in an ongoing stimulus. It is this nature of ACC that has generated interest in studying the usefulness of ACC as an objective tool for evaluating difference limens for various stimulus parameters. The present study therefore aimed at investigating the utility of ACC as an objective measure of difference limen for intensity (DLI) in normal hearing children with and without (C)APD. METHODS: Fifteen children with (C)APD and 15 normal hearing children in whom (C)APD was ruled out (comparison group) in the age range of 8-12 years underwent ACC for 6 intensity differences (+1, +3, +4, +5, +10 & +20 dB) and a standard stimulus using a 1000 Hz stimulus. RESULTS: Behavioral DLI (DLIb) as well as DLI found using ACC (DLIo) were both significantly larger in children with (C)APD than the comparison group (p < 0.05). Further, there was a significantly strong positive correlation between DLIb and DLIo (p < 0.001]. CONCLUSION: Outcome of the study provides evidence for the clinical use of ACC as an objective tool for examining DLI in children with (C)APD.

Robot-assisted assessment of wrist proprioception: does wrist proprioceptive acuity follow Weber's law?

Proprioception is essential for planning and controlling limb posture and movement. In our recent work, we introduced a standardized robot-aided method for measuring proprioceptive discrimination thresholds at the wrist to obtain reliable and accurate measures of proprioceptive acuity. Weber's law defines discrimination thresholds as a constant ratio between the just noticeable difference and the reference or standard stimulus. Reporting Weber's fractions thus provides the possibility of comparing results with the reports of others collected worldwide. This work aims to determine that Weber's Law holds for proprioceptive discrimination thresholds and to provide Weber's fraction for wrist joint proprioception. To this end, eight healthy subjects experienced two passive wrist movements of different amplitude and verbally indicated which was larger. An adaptive psychophysical procedure established the amplitude of the largest stimulus according to participants' responses. This comparison stimulus was then compared to a standard stimulus amplitude of 10°, 20°, 30° or 40°. The discrimination thresholds for each standard stimulus were established at the 75% correct response level. The obtained thresholds followed Weber's Law indicating that larger amplitudes were associated with higher discrimination thresholds. Based on a linear regression function the overall Weber's fraction, defined as the slope of the line, was computed to be 0.09. This result expands the present limited knowledge on wrist proprioception showing that its proprioceptive acuity follows Weber's law.

Quantitative Assessment of Root Canal Roughness with Calcium-Based Hypochlorite Irrigants by 3D CLSM

Chemical solutions play important roles in endodontic treatment and promote ultrastructural changes in dentin surface. The aim of this study was to quantify root canal roughness at different concentrations of calcium hypochlorite (Ca(OCl)2) and sodium hypochlorite (NaOCl) by confocal laser scanning microscopy (CLSM). Fifty-two human mandibular premolars were sectioned and randomly organized into thirteen groups (n=8): saline (control); 1%, 2.5% and 5% NaOCl; 1%, 2.5% and 5% Ca(OCl)2; the hypochlorite groups were further divided into with or without EDTA. The chlorine concentrations of the different solutions were measured by iodine titration (%). The superficial roughness (Sa) was quantified by CLSM. Ca(OCl)2 presented substantial decrease in chlorine concentration that differed from the package indication, but without compromising the dentin ultrastructure changes. There were no significant differences in dentin roughness between Ca(OCl)2 or NaOCl at all studied concentrations. The combination with EDTA provided similar roughness values among the solutions (p>0.05). The 5% Ca(OCl)2 and NaOCl solutions significantly increased dentin roughness and did not differ from the EDTA association (p>0.05). Ca(OCl)2 promoted similar dentin roughness as the NaOCl at the same concentrations and combined with EDTA. It may be concluded that Ca(OCl)2 modified the root canal dentin roughness similarly to NaOCl, at the same concentrations and EDTA combinations used in this study. Ca(OCl)2 and NaOCl, both at 5%, significantly altered dentin roughness, overcoming EDTA association, thus Ca(OCl)2 concentrations ranging from 1% to 2.5% may be suitable solutions for root canal irrigation protocols.

Soluções químicas são fundamentais para o tratamento endodôntico; entretanto, promovem alterações ultraestruturais na superfície dentinária. O objetivo deste estudo foi quantificar a rugosidade da dentina radicular com diferentes concentrações de hipoclorito de cálcio (Ca(OCl)2) e hipoclorito de sódio (NaOCl) utilizando microscopia confocal à laser (CLSM). Foram utilizados 52 premolares humanos inferiores e aleatoriamente divididos em treze grupos (n=8): Soro fisiológico (controle); NaOCl a 1%, 2,5% and 5%; Ca(OCl)2 a 1%, 2,5% and 5%; os grupos de hipoclorito foram subdivididos pela associação ou não ao ácido etilenodiaminotetracético (EDTA). A concentração de cloro ativo foi avaliada para diferentes soluções utilizando titulação iodométrica (%). A rugosidade superficial (Sa) foi quantificada por CLSM. Ca(OCl)2 apresentou perda substancial de cloro ativo e que foi distinta da condição descrita pelo fabricante, sem entretanto comprometer as alterações no substrato dentinário. Não houve diferenças significantes na rugosidade dentinária produzida pelos Ca(OCl)2 e NaOCl em todas as concentrações estudadas e associação com EDTA. A associação ao EDTA produziu rugosidade semelhante entre as soluções (p>0.05). O Ca(OCl)2 e NaOCl na concentração de 5% aumentaram significativamente a rugosidade dentinária e não apresentaram diferenças dos valores obtidos com a associação de EDTA (p>0.05). O Ca(OCl)2 alterou a rugosidade da dentina radicular de forma semelhante ao NaOCl, nas concentrações e associações utilizadas neste estudo. Como a concentração de 5% de Ca(OCl)2 e NaOCl, apresentou maior rugosidade dentinária, independente da associação ao EDTA, pode-se concluir que Ca(OCl)2 nas concentrações de 1% e 2,5% pode ser considerado uma solução adequada para a irrigação de canais radiculares.

Tracking of nociceptive thresholds using adaptive psychophysical methods.

Psychophysical thresholds reflect the state of the underlying nociceptive mechanisms. For example, noxious events can activate endogenous analgesic mechanisms that increase the nociceptive threshold. Therefore, tracking thresholds over time facilitates the investigation of the dynamics of these underlying mechanisms. Threshold tracking techniques should use efficient methods for stimulus selection and threshold estimation. This study compares, in simulation and in human psychophysical experiments, the performance of different combinations of adaptive stimulus selection procedures and threshold estimation methods. Monte Carlo simulations were first performed to compare the bias and precision of threshold estimates produced by three different stimulus selection procedures (simple staircase, random staircase, and minimum entropy procedure) and two estimation methods (logistic regression and Bayesian estimation). Logistic regression and Bayesian estimations resulted in similar precision only when the prior probability distributions (PDs) were chosen appropriately. The minimum entropy and simple staircase procedures achieved the highest precision, while the random staircase procedure was the least sensitive to different procedure-specific settings. Next, the simple staircase and random staircase procedures, in combination with logistic regression, were compared in a human subject study (n = 30). Electrocutaneous stimulation was used to track the nociceptive perception threshold before, during, and after a cold pressor task, which served as the conditioning stimulus. With both procedures, habituation was detected, as well as changes induced by the conditioning stimulus. However, the random staircase procedure achieved a higher precision. We recommend using the random staircase over the simple staircase procedure, in combination with logistic regression, for nonstationary threshold tracking experiments.

Assessment of adequate safety margin using single coupling interval-upper limit of vulnerability test.

PURPOSE: Upper limit of vulnerability (ULV) testing using T-wave scanning shocks at multiple coupling intervals correlates well with defibrillation threshold (DFT), but remains underutilized in clinical practice. We measured DFT and ULV at a single coupling interval (SCI), with the aim to identify adequate safety margin at a coupling interval that correlates best with DFT. METHODS: Consecutive patients undergoing implantable cardioverter defibrillator implantation underwent simultaneous SCI-ULV and DFT assessment. Following a drive train of 400 ms, a T-wave-coupled shock was delivered. To minimize shocks, patients were randomized to programmed shock at 20 ms before peak (Group I), at peak (Group II), or 20 ms after peak (Group III) of T wave. An initial T-wave test shock at 9 J was followed by ±2 J shocks, until SCI-ULV was ascertained. Device rescue shocks were programmed at test shock +2 J and +4 J shocks followed by external rescue shock. RESULTS: There were 200 patients: 66 patients in Group I, 67 patients each in Groups II and III; mean age was 68.9 ± 12.4 years; 75% of patients men, 66% with ischemic heart disease and mean ejection fraction of 27.1 ± 7.1%. Overall, the mean number of ventricular fibrillation induction was 1.39 ± 0.8, mean SCI-ULV energy was 7.97 ± 3.39 J, and mean DFT was 8.68 ± 3.19 J. The correlation between SCI-ULV and DFT improved from Group I to Group III and was best in Group III (r(2) = 0.689). There were no major adverse events. CONCLUSIONS: SCI-ULV measured 20 ms after the peak of the T wave correlates well with DFT for assessment of adequate safety margin.

[Assessment of mesopic and contrast vision for driving licences: which cut-off values, which methods are appropriate?]. / Untersuchung des Dämmerungs- und Kontrastsehens nach Fahrerlaubnisverordnung: Welche Grenzwerte, welche Verfahren sind geeignet?

BACKGROUND: Hitherto recommendations and thresholds for contrast tests are available for mesopic but not for photopic methods. While mesopic tests are widespread in ophthalmology, in occupational medicine photopic contrast tests are often used. With regard to the attachment 6 of the German Fahrerlaubnisverordnung (FeV) which is relevant since July 2011 we tested the specificity and sensitivity as well as the test-retest reliability of available test devices and defined cut-off values. METHODS: We examined patients with medium opacities, healthy volunteers and a sample of employees. Optovist EU, Binoptometer 4P and Pelli-Robson charts with standardised illumination were applied for contrast sensitivity testing. All these methods were compared to the Mesotest II as gold standard. We followed the recommendations of the German Qualitätssicherungs-Kommission der Deutschen Ophthalmologischen Gesellschaft (DOG) for contrast vision testing and definition of cut-off values. RESULTS: 64 patients with cataract (age 42-70 years, median 62 years), 50 pilots (age 40-69 years, median 53.5 years) and 109 employees of a transportation company (age 40-59 years, median 50 years) were included in the trial. All contrast sensitivity tests showed a good sensitivity and specificity (AUC 0.86 to 0.99). For Optovist EU and Binoptometer 4P a threshold of 15 % Weber contrast is recommended for examinations according to FeV. The test-retest reliability was high in all methods with highly significant Pearson correlation coefficients of 0.77 to 0.94 and a repeatability coefficient between 0.08 und 0.4. The standard distance of 1 m common for the Pelli-Robson chart cannot be recommended for FeV examinations, while the results at 3 m distance are comparable to those of the other contrast vision tests. The preliminary cut-off for the Pelli-Robson chart at 3 m distance is 1.65. CONCLUSIONS: Cut-off values for the lawful assessment of applicants are now available. Both Binoptometer 4P and Optovist EU proved to be appropriate and - as expected due to comparable technical properties - the same cut-off can be recommended. At 1 m distance the Pelli-Robson chart is not sensitive enough. Because the new distance of 3 m for the Pelli-Robson chart was investigated in 55 cataract patients and 10 pilots in this trial, a confirmatory trial for this distance is planned.

Estimating discrimination performance in two-alternative forced choice tasks: routines for MATLAB and R.

Ulrich and Vorberg (Attention, Perception, & Psychophysics 71: 1219-1227, 2009) introduced a novel approach for estimating discrimination performance in two-alternative forced choice (2AFC) tasks. This approach avoids pitfalls that are inherent when the order of the standard and the comparison is neglected in estimating the difference limen (DL), as in traditional approaches. The present article provides MATLAB and R routines that implement this novel procedure for estimating DLs. These routines also allow to account for processing failures such as lapses or finger errors and can be applied to experimental designs in which the standard and comparison differ only along the task-relevant dimension, as well as to designs in which the stimuli differ in more than one dimension. In addition, Monte Carlo simulations were conducted to check the quality of our routines.

Stability analysis of some delay differential inequalities with small time delays and its applications.

In this paper, we discuss the asymptotic stability of the trajectories governed by the scalar delay differential inequalities: D⁺x(t)≤-a(t)x(t)+b(t)sup(0≤s≤τ)x(t-s). Here, the requirements on a(t) and b(t) are more relaxed than those in previous works. For example, a(t), b(t), and a(t)-b(t) are not necessarily nonnegative. We prove that when τ is small, the asymptotic stability of x(t) can be obtained if the time average of a(t)-b(t) on some fixed length T is lower bounded by some positive δ. And we explicitly give the upper bound of τ. We also give two applications of the theoretical results. First, we consider self synchronization in Hopfield networks with time varying connections. Then we investigate consensus in networks with time varying topologies and arbitrary coupling weights. In both applications, we extend some of our previous works where time delays are not considered. At last, two numerical examples with simulations are provided to illustrate the effectiveness of the theoretical results.

Decision criteria in dual discrimination tasks estimated using external-noise methods.

According to classical signal detection theory (SDT), in simple detection or discrimination tasks, observers use a decision parameter based on their noisy internal response to set a boundary between "yes" and "no" responses. Experimental paradigms where performance is limited by internal noise cannot be used to provide an unambiguous measure of the decision criterion and its variability. Here, unidimensional external noise is used to estimate a criterion and its variability in stimulus space. Within this paradigm, the criterion is defined as the stimulus value separating the two response alternatives. This paradigm allows the assessment of interactions between criteria assigned to different targets in dual tasks. Previous studies suggested that observers' criteria interacted or even collapsed to one (hence, nonoptimal) criterion. An alternative interpretation of those results is that observers equated their false alarm (FA) rates. The external-noise method enables the confrontation of the two hypotheses. It is shown that the variability of observers' criterion in stimulus space is about 1.6 times their measured sensory threshold, suggesting that the presence of external noise increases decision uncertainty. Observers' stimulus criterion settings are close to SDT predictions in single tasks, but not in dual tasks where the two criteria tend to "attract" each other. Observers maintain distinct FA rates even when SDT predicts equal rates. Observers trained in psychophysics or provided with basic notions of SDT exemplified with the present experimental design manage to better separate their criteria in some conditions.

Toxicokinetics/toxicodynamics with damage feedback improves risk assessment for tilapia and freshwater clam exposed to arsenic.

It has been proposed that irreversible responses of organisms exposed to contaminants are due to a systems-level feedback. Here we tested this hypothesis by reanalyzing the published data on toxicokinetics and survival probability based on a systems-level threshold damage model (TDM) incorporating with a positive damage feedback to explore the steady-state response and dynamic behavior of damage for tilapia and freshwater clam exposed to waterborne arsenic (As). We found that ultrasensitivity appeared in As-tilapia and freshwater clam systems with Hill coefficient n ≥ 4, indicating that the positive damage feedback mechanism has been triggered. We confirmed that damage can trigger a positive feedback loop that together with As stressor increases irreversibility. This study also showed that TDM with positive feedback gave a much better predictability than that of TDM at As concentrations ranging from 100 to 500 mg l(-1) for freshwater clam, whereas for tilapia, two models had nearly same performance on predictability. We suggested that mortality-time profile derived Hill coefficient could be used as a new risk indicator to assess the survival probability for species exposed to waterborne metals. We anticipated that the proposed toxicokinetics/toxicodynamics with a positive damage feedback may facilitate our understanding and manipulation of complex mechanisms of metal susceptibility among species and improve current risk assessment strategies.

Subthalamic nucleus stimulation reverses mediofrontal influence over decision threshold.

It takes effort and time to tame one's impulses. Although medial prefrontal cortex (mPFC) is broadly implicated in effortful control over behavior, the subthalamic nucleus (STN) is specifically thought to contribute by acting as a brake on cortico-striatal function during decision conflict, buying time until the right decision can be made. Using the drift diffusion model of decision making, we found that trial-to-trial increases in mPFC activity (EEG theta power, 4-8 Hz) were related to an increased threshold for evidence accumulation (decision threshold) as a function of conflict. Deep brain stimulation of the STN in individuals with Parkinson's disease reversed this relationship, resulting in impulsive choice. In addition, intracranial recordings of the STN area revealed increased activity (2.5-5 Hz) during these same high-conflict decisions. Activity in these slow frequency bands may reflect a neural substrate for cortico-basal ganglia communication regulating decision processes.

The minimally important difference (MID) for patient-reported outcomes including pain, fatigue, sleep and the health assessment questionnaire disability index (HAQ-DI) in primary Sjögren's syndrome.

OBJECTIVES: We wanted to determine the MID for the HAQ, pain, fatigue, sleep and global VAS (0-100mm) in Sjögren's syndrome (SS) using a patient-reported overall health status anchor. METHODS: Patients with a diagnosis of primary Sjögren's syndrome (pSS) who had answered a standardised questionnaire at two consecutive visits including an overall health status question: 'How would you describe your overall status since your last visit: much better, better, the same, worse, much worse?' were included. The MID was calculated as the mean change between visits for those who rated their disease as better or worse. Scales on VAS were from 0 (best) to 100 (worst). RESULTS: Forty patients met the inclusion criteria (97% female, mean age 58 years, mean disease duration 10 years). The mean baseline HAQ was 0.68. Ten rated their status as better and 14 as worse than the previous visit. MID estimates for improvemenT/worsening (SD) respectively were: -7.4 (27.8) / 20.7 (20.0) for pain VAS, -6.2 (28.3) / 15.2 (21.8) for fatigue VAS, -24.0 (24.0) / 15.2 (28.0) for sleep VAS, -0.18 (0.23) / 0.14 (0.30) for HAQ and -23.1 (21.6) / 16.4 (20.9) for global VAS. Spearman's rho correlation coefficients for the patient-reported outcomes were 0.38 (pain VAS), 0.54 (fatigue VAS), 0.55 (sleep VAS), 0.39 (HAQ), and 0.57 (global VAS), p<0.05. CONCLUSIONS: The MID for pain and fatigue are greater for worsening than improvement. A small change in the HAQ is detected as a change in status by the patient. This knowledge may aid those who treat SS and in designing intervention studies.

Threshold curves for transcranial magnetic stimulation to improve reliability of motor pathway status assessment.

OBJECTIVE: To provide a new protocol for a simple determination of resting motor threshold (MT) and assessment of excitation-inhibition balance in motor cortex and pathways. METHODS: Navigated TMS was used to map cortical representation area of the FDI muscle bilaterally in ten healthy subjects. Reference MTs were determined using a threshold hunting paradigm. Subsequently, a novel stimulation protocol was applied which included 70 stimuli (7 intensities, sub- and suprathreshold). The "MT-curve" was constructed by computing the MTs with several threshold amplitudes with the novel protocol. The measurements were repeated. Sensitivity of the MT-curve to stimulus location was also tested. RESULTS: The reference MTs agreed with those determined with the novel protocol (R=0.96-0.99, p<0.001). Based on coefficient of repeatability derived from non-parametric one-way ANOVA, the repeatability was good (ρ(AO)=0.929, p<0.05). Generally, the mean difference between the repeated MT-curves was <3% of the maximum stimulator output. Coil movement 10mm medially from the optimal stimulus location increased that difference to >7%. CONCLUSIONS: The MTs derived using the MT-curve protocol concurred with the reference MTs. The MT-curve is highly reproducible and sensitive to the exact cortical location of stimulation. SIGNIFICANCE: The MT-curves provide a simple way to assess motor pathway status using a single stimulation train. This may be useful in the follow-up and monitoring of motor pathway recovery e.g. from stroke or trauma.

Assessment of changes in the oral tactile function of the soft tissues by implant placement in the anterior maxilla: a prospective study.

The aim of the present study was to assess the somatosensory function in the peri-implant soft tissues in the anterior jaw bone by means of two psychophysical tests. Light-touch sensation (LTS) and two-point discrimination (2PD) were performed before, and at planned intervals until 18 months after the placement of one or two implants in the anterior maxilla. The same tests were used on the contralateral control sites. The psychophysical threshold was determined by performing the staircase method. The mean values and standard deviation of LTS and 2PD, pooled over the four sessions at each test area, were calculated. Despite a large intersubject variation in both the LTS and 2PD, significantly high intra-individual correlations were found (P < 0.005). For LTS, the thresholds were not significantly affected over time (P > 0.05) on both implant and control sites. The 2PD increased significantly after surgery and maintained the higher discriminatory sense for 1 year (P-value 0.005). The control sites remained stable over time. However, no correlation was revealed between LTS and 2PD perception (Pearson correlation test). In this prospective study, no major differences between the different sites and testing sessions were reported; except for the 2PD thresholds which were lowered after implant surgery. These findings suggest that the regenerated nerves may be responsible for the increased 2PD sensitivity in the peri-implant soft tissue. The unchanged LTS thresholds did not allow confirming this hypothesis.

Pattern recognition in correlated and uncorrelated noise.

This study examined how correlated, or filtered, noise affected efficiency for recognizing two types of signal patterns, Gabor patches and three-dimensional objects. In general, compared with the ideal observer, human observers were most efficient at performing tasks in low-pass noise, followed by white noise; they were least efficient in high-pass noise. Simulations demonstrated that contrast-dependent internal noise was likely to have limited human performance in the high-pass conditions for both signal types. Classification images showed that observers were likely adopting different strategies in the presence of low-pass versus white noise. However, efficiencies were underpredicted by the linear classification images and asymmetries were present in the classification subimages, indicating the influence of nonlinear processes. Response consistency analyses indicated that lower contrast-dependent internal noise contributed somewhat to higher efficiencies in low-pass noise for Gabor patches but not objects. Taken together, the results of these experiments suggest a complex interaction among signals, external noise spectra, and internal noise in determining efficiency in correlated and uncorrelated noise.

The behavioral economics of choice and interval timing.

The authors propose a simple behavioral economic model (BEM) describing how reinforcement and interval timing interact. The model assumes a Weber-law-compliant logarithmic representation of time. Associated with each represented time value are the payoffs that have been obtained for each possible response. At a given real time, the response with the highest payoff is emitted. The model accounts for a wide range of data from procedures such as simple bisection, metacognition in animals, economic effects in free-operant psychophysical procedures, and paradoxical choice in double-bisection procedures. Although it assumes logarithmic time representation, it can also account for data from the time-left procedure usually cited in support of linear time representation. It encounters some difficulties in complex free-operant choice procedures, such as concurrent mixed fixed-interval schedules as well as some of the data on double bisection, which may involve additional processes. Overall, BEM provides a theoretical framework for understanding how reinforcement and interval timing work together to determine choice between temporally differentiated reinforcers.