Clinical Characteristics and Outcomes Associated With Distinct Hemodynamic Patterns in End-stage Liver Disease: A Retrospective Cohort Analysis.

Introduction: Despite advances in the diagnosis and therapeutics strategies for pulmonary hypertension (PH) in patients with end-stage liver disease (ESLD), the impact of hemodynamic patterns among ESLD patients identified through right heart catheterization (RHC) on clinical outcomes remains poorly understood. Methods: This single-center retrospective cohort study identified patients diagnosed with ESLD who underwent RHC from August 2018 to June 2023. Demographic and clinical data, including comorbidities, transthoracic echocardiography, and RHC findings, were obtained. Our outcomes of interest were all-cause mortality and the chance of receiving orthotopic liver transplantation (OLT) within a year after RHC. Kaplan-Meier with log-rank test was employed to generate survival curves. Results: We identified 415 ESLD patients with the RHC results. The median (IQR) age was 59 years (52-66), and 62% were male. Caucasians accounted for 43%, followed by African Americans (30%). Up to 89% had a diagnosis of portal hypertension. Median MELD-Na score was 30 (19-36). The etiology of ESLD was mainly from alcohol use (55%). Patients were classified based on RHC results as pre-capillary PH (19%), post-capillary PH (28%), and non-PH (53%) groups. Overall, one-year mortality post-RHC was 22%, with no significant difference in mortality regardless of hemodynamic group. However, the pre-capillary PH group was less likely to receive OLT compared to other groups (P < 0.001). Conclusion: We observed no difference in all-cause mortality among hemodynamic groups. However, pre-capillary PH group were less likely to undergo OLT compared to others. Further investigations are necessary to determine how this should be addressed in clinical practice.

Association of arteriovenous fistulae with precapillary pulmonary hypertension - A single center retrospective analysis of invasive hemodynamic parameters.

BACKGROUND: Pulmonary hypertension (pH) is a well-known complication among patients with chronic kidney disease (CKD). Arteriovenous fistulae (AVF) have been associated with pH mainly by increasing cardiac output. However, the burden of precapillary pH in individuals with CKD and an AVF is unclear. OBJECTIVES: To better and more fully understand the mechanism and development of precapillary pH in patients with AVF, as well as the consequences of precapillary pH in these patients. METHODS: This was a large retrospective study of patients with CKD stage 4 or 5 who underwent right heart catheterization (RHC) from 2018 to 2023. The data were stratified according to the presence of AVF. To determine if AVF was independently associated with precapillary pH, we used a multivariable logistic regression analysis adjusting for demographics and potential comorbidities associated with precapillary pH, including diagnosis of chronic lung disease, obstructive sleep apnea, connective tissue disease, history of venous thromboembolism, chronic anemia, and heart failure. RESULTS: Of 651 patients with CKD4 or CKD5, 145 (22 %) had AVF and 506 (78 %) did not have AVF. Within the AVF group, the median age was 64 years (IQR 54-71), and they were predominantly males (61 %, n = 88) and African American (77 %, n = 111). A total of 31 % (n = 45) had evidence of precapillary pH, 30 % (n = 43) of combined pH, and 14 % (n = 20) of isolated postcapillary pH. Compared to the non-AVF group, precapillary pH was more likely in the AVF group (31% vs 17 %, p < 0.0001). On multivariable analysis, AVF was independently associated with precapillary pH (OR 2.47, CI 1.56-3.89; p < 0.0001). The median time from dialysis initiation to RHC date (and precapillary pH diagnosis) was 6 years (IQR 3-8). CONCLUSION: Based on RHC findings, almost one-third of patients with CKD and AVF had precapillary pH. The presence of AVF was independently associated with precapillary pH.

Association of mildly elevated pulmonary vascular resistance with major cardiovascular events in pulmonary hypertension and chronic kidney disease: A retrospective cohort analysis.

Pulmonary hypertension (PH) is associated with adverse outcomes in chronic kidney disease (CKD) patients. Our study suggests mildly elevated pulmonary vascular resistance ( > 2 to ≤ 3) is independently associated with major adverse cardiovascular events at 1-year follow-up. Early diagnosis of precapillary PH in CKD patients can potentially improve clinical outcomes.

Modulating perceptual learning indexed by the face inversion effect: Simulating the application of transcranial direct current stimulation using the MKM model.

We report here two large studies investigating the effects of an established transcranial direct current stimulation (tDCS) procedure on perceptual learning as indexed by the face inversion effect. Experiments 1a and 1b (n = 128) examined the harmful generalization from Thatcherized faces to normal faces by directly comparing the size of the inversion effect for normal faces when presented intermixed with Thatcherized faces (Experiment 1a) versus that obtained when normal faces were presented intermixed with checkerboards (Experiment 1b). The results from the sham/control tDCS groups provide the first direct evidence in the literature showing how Thatcherized faces generalize onto normal ones producing a reduced inversion effect compared to when normal faces are presented with stimuli (e.g., checkerboards) that do not generalize significantly to normal faces. In the anodal tDCS groups, this effect was reversed, with a larger inversion effect recorded for normal faces in Experiment 1a versus that found in Experiment 1b. Further analyses within each experiment confirmed that the anodal tDCS procedure can enhance the inversion effect for normal faces in circumstances where harmful generalization would otherwise be produced by the Thatcherized faces (Experiment 1a). We also demonstrated our standard reduction in the inversion effect for normal faces consequent on the application of tDCS when presented intermixed with stimuli that do not generalize onto them. We interpret our results in terms of simulations using the MKM model of perceptual and associative learning. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

PEP Does Not Dispense with but Implements Task-Set Reconfiguration. Can It Handle Phenomena More Diagnostic of Endogenous Control?

Invited commentary on Schmidt, Liefooghe, and De Houwer (2020) An episodic model of task switching effects: erasing the homunculus from memory. Journal of Cognition.

Behavioral flexibility: A review, a model, and some exploratory tests.

This paper aimed to explore and clarify the concept of behavioral flexibility. A selective literature review explored how the concept of behavioral flexibility has been used in ways that range from acknowledging the fact that animals' behavior is not always bounded by instinctual constraints, to describing the variation between species in their capacity for innovative foraging, a capacity that has repeatedly been linked to having a brain larger than would be predicted from body size. This wide range of usages of a single term has led to some conceptual confusion. We sought to find a more precise meaning for behavioral flexibility by representing it within a simple formal model of problem solving. The key to our model is to distinguish between an animal's state of knowledge about the world and its observable behavior, using a construct of response strength to represent that underlying knowledge. We modelled behavioral flexibility as a parameter in the function that transforms response strengths into observable response probabilities. We tested this model in simulations based on some recent experimental work on animal problem solving. Initial results showed that parametric manipulation can mimic some of the behavioral effects that have been attributed to flexibility.

Measuring response inhibition with a continuous inhibitory-control task.

Inhibitory control enables subjects to quickly react to unexpected changes in external demands. In humans, this kind of behavioral flexibility is often used as an indicator of an individual's executive functions, and more and more research has emerged to investigate this link in nonhuman animals as well. Here we explored the value of a recently developed continuous inhibitory-control task in assessing inhibitory-control capacities in animals. Pigeons completed a response-inhibition task that required them to adjust their movement in space in pursuit of a reward across changing target locations. Inhibition was measured in terms of movement trajectory (path taken toward the correct location for trials in which the target location did and did not change) and velocity (both before and after correcting the trajectory toward the changed location). Although the observed velocities did not follow any of our predictions in a clear way, the pigeons' movement trajectories did prove to be a good indicator of inhibitory control, showing that pigeons, though limited in their capacities relative to the sophisticated control strategies expressed by humans, are capable of exerting some forms of inhibitory control. These results strengthen the role of this paradigm as a valuable tool for evaluating inhibitory-control abilities across the animal kingdom.

Instructed and Acquired Contingencies in Response-Inhibition Tasks.

Inhibitory control can be triggered directly via the retrieval of previously acquired stimulus-stop associations from memory. However, a recent study suggests that this item-specific stop learning may be mediated via expectancies of the contingencies in play (Best, Lawrence, Logan, McLaren, & Verbruggen, 2016). This could indicate that stimulus-stop learning also induces strategic proactive changes in performance. We further tested this hypothesis in the present study. In addition to measuring expectancies following task completion, we introduced a between-subjects expectancy manipulation in which one group of participants were informed about the stimulus-stop contingencies and another group did not receive any information about the stimulus-stop contingencies. Moreover, we combined this instruction manipulation with a distractor manipulation that was previously used to examine strategic proactive adjustments. We found that the stop-associated items slowed responding in both conditions. Furthermore, participants in both conditions generated expectancies following task completion that were consistent with the stimulus-stop contingencies. The distractor manipulation was ineffective. However, we found differences in the relationship between the expectancy ratings and task performance: in the instructed condition, the expectancies reliably correlated with the response slowing for the stop-associated items, whereas in the uninstructed condition we found no reliable correlation. These differences between the correlations were reliable, and our conclusions were further supported by Bayesian analyses. We conclude that stimulus-stop associations that are acquired either via task instructions or via task practice have similar effects on behaviour but could differ in how they elicit response slowing.

Pigeons' performance in a tracking change-signal procedure is consistent with the independent horse-race model.

In many cognitive tasks where humans are thought to rely on executive functioning, pigeons' behavior can be explained by associative processes. A key form of executive functioning is inhibiting prepotent responses, often investigated in humans by means of "Stop-Signal" or "Change-Signal" procedures. In these procedures, execution of a well-practiced ("Go") response to a stimulus is occasionally interrupted by a signal to withhold or alter the practiced response. Performance in such tasks is usually described by the "independent horse horse-race model." This model assumes that the processes that cause the Go and inhibitory responses occur independently; the process that finishes first determines the response observed. We further tested this model by training pigeons to track the circular movement of a colored patch around a touchscreen by pecking it; the spot occasionally deviated from its normal path (the Change signal). The pigeons had to inhibit the habitual movement of their heads to land a peck on the spot in its unexpected position. The key predictions of the independent horse-race model were confirmed in the pigeons' latency data. Thus, the independent race model can also successfully describe Stop-change performance of subjects that do not rely on executive control. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Revisiting peak shift on an artificial dimension: Effects of stimulus variability on generalisation.

One of Mackintosh's many contributions to the comparative psychology of associative learning was in developing the distinction between the mental processes responsible for learning about features and learning about relations. His research on discrimination learning and generalisation served to highlight differences and commonalities in learning mechanisms across species and paradigms. In one such example, Wills and Mackintosh trained both pigeons and humans to discriminate between two categories of complex patterns comprising overlapping sets of abstract visual features. They demonstrated that pigeons and humans produced similar "peak-shifted" generalisation gradients when the proportion of shared features was systemically varied across a set of transfer stimuli, providing support for an elemental feature-based analysis of discrimination and generalisation. Here, we report a series of experiments inspired by this work, investigating the processes involved in post-discrimination generalisation in human category learning. We investigate how post-discrimination generalisation is affected by variability in the spatial arrangement and probability of occurrence of the visual features and develop an associative learning model that builds on Mackintosh's theoretical approach to elemental associative learning.

The Urology Applicant: An Analysis of Contemporary Urology Residency Candidates.

OBJECTIVE: To better understand today's urology applicant. METHODS: All 2016 Urology Residency Match applicants to the study-participating institutions were provided a survey via email inquiring about their paths to urology, their career aspirations, how they evaluate a training program, and how they perceive residency programs evaluate them. RESULTS: Of a possible 468 applicants registered for the match, 346 applicants completed the survey. Only 8.7% had a mandatory urology rotation, yet 58.4% believed that a mandatory urology rotation would influence their career decision. Most applicants (62.1%) spent more than 8 weeks on urology rotations, and 79.2% completed 2 or more away rotations. Applicants were attracted to urology by the diversity of procedures, prior exposure to the field, and the mix of medicine and surgery, with mean importance scores of 4.70, 4.52, and 4.45 of 5, respectively. Female applicants were more likely to be interested in pediatric urology, trauma or reconstructive urology, and female pelvic medicine and reconstructive surgery. Significant differences in survey results were noted when applicants were separated by gender. Three-fourths of respondents (75.7%) applied to more than 50 residency programs. Applicants ranked operative experience, interactions with current residents, and relationships between faculty and residents as the most important criteria when evaluating training programs. Of the subspecialties, 62.1% of applicants expressed most interest in urologic oncology. At this stage in their career, a significant majority (83.5%) expressed interest in becoming academic faculty. CONCLUSION: This study provides new information that facilitates a more comprehensive understanding of today's urology applicants.

Pigeons in control of their actions: Learning and performance in stop-signal and change-signal tasks.

In human participants, 2 paradigms commonly assumed to measure the executive-control processes involved in response inhibition are the stop-signal and change-signal tasks. There is, however, also considerable evidence that performance in these tasks can be mediated by associative processes. To assess which components of inhibitory response control might be associative, we developed analogues of these tasks for pigeons. We trained pigeons to peck quickly at 1 of 2 keys of different colors to obtain a food reward. On some trials, the rewarded key was replaced (after a varying interval) by a signal of a different color. For some birds, this was a change signal: pecking the signal had no effect, but pecking the usually unrewarded alternative key led to a reward, so the response had to be changed. For other birds, the change in color was a stop signal: pecking the alternative key remained ineffective, but pecking the signal now led to a timeout instead of the usual reward, so responses had to be withheld. Pigeons succeeded in both tasks, but performance declined with increasing signal delay. The details of performance in both tasks were consistent with the independent horse-race model of inhibitory control often applied to studies of human participants. This outcome further suggests that stop-signal tasks of the kind used here might not necessarily be suitable for assessing top-down executive-control processes in humans. (PsycINFO Database Record

Winning and losing: Effects on impulsive action.

In the present study, we examined the effect of wins and losses on impulsive action in gambling (Experiments 1-3) and nongambling tasks (Experiments 4-5). In each experiment, subjects performed a simple task in which they had to win points. On each trial, they had to choose between a gamble and a nongamble. The gamble was always associated with a higher amount but a lower probability of winning than the nongamble. After subjects indicated their choice (i.e., gamble or not), feedback was presented. They had to press a key to start the next trial. Experiments 1-3 showed that, compared to the nongambling baseline, subjects were faster to initiate the next trial after a gambled loss, indicating that losses can induce impulsive actions. In Experiments 4 and 5, subjects alternated between the gambling task and a neutral decision-making task in which they could not win or lose points. Subjects were faster in the neutral decision-making task if they had just lost in the gambling task, suggesting that losses have a general effect on action. Our results challenge the dominant idea that humans become more cautious after suboptimal outcomes. Instead, they indicate that losses in the context of potential rewards are emotional events that increase impulsivity. (PsycINFO Database Record

Evidence for multiple processes contributing to the Perruchet effect: Response priming and associative learning.

The Perruchet effect constitutes a robust demonstration that it is possible to dissociate conditioned responding and expectancy in a random partial reinforcement design across a variety of human associative learning paradigms. This dissociation has been interpreted as providing evidence for multiple processes supporting learning, with expectancy driven by cognitive processes that lead to a Gambler's fallacy, and the pattern of conditioned responding (CRs) the result of an associative learning process. An alternative explanation is that the pattern of CRs is the result of exposure to the unconditioned stimulus (US). In 3 human eyeblink conditioning experiments we examined these competing explanations of the Perruchet effect by employing a differential conditioning design and varying the degree to which the 2 conditioned stimuli (CS) were discriminable. Across all of these experiments there was evidence for a component of the CRs being strongly influenced by recent reinforcement, in a way that was not demonstrably influenced by manipulations of CS discriminability, which suggests a response priming mechanism contributes to the Perruchet effect. However, the complete pattern of results and an analysis of the results from previously published studies are also consistent with there being an associative contribution to the effect. (PsycINFO Database Record

Task-switching in pigeons: Associative learning or executive control?

Human performance in task-switching paradigms is seen as a hallmark of executive-control processes: switching between tasks induces switch costs (such that performance when changing from Task A to Task B is worse than on trials where the task repeats), which is generally attributed to executive control suppressing one task-set and activating the other. However, even in cases where task-sets are not employed, as well as in computational modeling of task switching, switch costs can still be found. This observation has led to the hypothesis that associative-learning processes might be responsible for all or part of the switch costs in task-switching paradigms. To test which cognitive processes contribute to the presence of task-switch costs, pigeons performed two different tasks on the same set of stimuli in rapid alternation. The pigeons showed no sign of switch costs, even though performance on Trial N was influenced by Trial N - 1, showing that they were sensitive to sequential effects. Using Pearce's (1987) model for stimulus generalization, we conclude that they learned the task associatively-in particular, a form of Pavlovian-conditioned approach was involved-and that this was responsible for the lack of any detectable switch costs. Pearce's model also allows us to make interferences about the common occurrence of switch costs in the absence of task-sets in human participants and in computational models, in that they are likely due to instrumental learning and the establishment of an equivalence between cues signaling the same task.

The Face Inversion Effect: Roles of First- and Second-Order Configural Information.

The face inversion effect (FIE) is a reduction in recognition performance for inverted faces compared with upright faces. Several studies have proposed that a type of configural information, called second-order relational information, becomes more important with increasing expertise and gives rise to the FIE. However, recently it has been demonstrated that it is possible to obtain an FIE with facial features presented in isolation, showing that configural information is not necessary for this effect to occur. In this article we test whether there is a role for configural information in producing the FIE and whether second- or first-order relational information is particularly important. In Experiment 1, we investigated the role of configural information and local feature orientation by using a new type of "Thatcherizing" transformation on our set of faces, aiming to disrupt second-order and local feature orientation information but keeping all first-order properties unaltered. The results showed a significant reduction in the FIE for these "new" Thatcherized faces, but it did not entirely disappear. Experiment 2 confirmed the FIE for new Thatcherized faces, and Experiment 3 establishes that both local feature orientation and first-order relational information have a role in determining the FIE.

Limits of Executive Control: Sequential Effects in Predictable Environments.

Cognitive-control theories attribute action control to executive processes that modulate behavior on the basis of expectancy or task rules. In the current study, we examined corticospinal excitability and behavioral performance in a go/no-go task. Go and no-go trials were presented in runs of five, and go and no-go runs alternated predictably. At the beginning of each trial, subjects indicated whether they expected a go trial or a no-go trial. Analyses revealed that subjects immediately adjusted their expectancy ratings when a new run started. However, motor excitability was primarily associated with the properties of the previous trial, rather than the predicted properties of the current trial. We also observed a large latency cost at the beginning of a go run (i.e., reaction times were longer for the first trial in a go run than for the second trial). These findings indicate that actions in predictable environments are substantially influenced by previous events, even if this influence conflicts with conscious expectancies about upcoming events.

A stimulus-location effect in contingency-governed, but not rule-based, discrimination learning.

We tested pigeons' acquisition of a conditional discrimination task between colored grating stimuli that included choosing 1 of 2 response keys, which either appeared as white keys to the left and right of the discriminative stimulus, or were replicas of the stimulus. Pigeons failed to acquire the discrimination when the response keys were white disks but succeeded when directly responding to a replica of the stimulus. These results highlight how conditioning processes shape learning in pigeons: The results can be accounted for by supposing that, when pigeons were allowed to respond directly toward the stimulus, learning was guided by classical conditioning, but that responding to white keys demanded instrumental learning, which impaired task acquisition for pigeons. In contrast, humans completing the same paradigm showed no differential learning success depending on whether figure or position indicated the correct key. However, only participants who could state the underlying discrimination rule acquired the task, which implies that human performance in this situation relied on the deduction and application of task rules instead of associative processes.

Should I stop or should I go? The role of associations and expectancies.

Following exposure to consistent stimulus-stop mappings, response inhibition can become automatized with practice. What is learned is less clear, even though this has important theoretical and practical implications. A recent analysis indicates that stimuli can become associated with a stop signal or with a stop goal. Furthermore, expectancy may play an important role. Previous studies that have used stop or no-go signals to manipulate stimulus-stop learning cannot distinguish between stimulus-signal and stimulus-goal associations, and expectancy has not been measured properly. In the present study, participants performed a task that combined features of the go/no-go task and the stop-signal task in which the stop-signal rule changed at the beginning of each block. The go and stop signals were superimposed over 40 task-irrelevant images. Our results show that participants can learn direct associations between images and the stop goal without mediation via the stop signal. Exposure to the image-stop associations influenced task performance during training, and expectancies measured following task completion or measured within the task. But, despite this, we found an effect of stimulus-stop learning on test performance only when the task increased the task-relevance of the images. This could indicate that the influence of stimulus-stop learning on go performance is strongly influenced by attention to both task-relevant and task-irrelevant stimulus features. More generally, our findings suggest a strong interplay between automatic and controlled processes.