Dopamine Alters the Effect of Brain Stimulation on Decision-Making.

Noninvasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS), show promise in treating a range of psychiatric and neurologic conditions. However, optimization of such applications requires a better understanding of how tDCS alters cognition and behavior. Existing evidence implicates dopamine in tDCS alterations of brain activity and plasticity; however, there is as yet no causal evidence for a role of dopamine in tDCS effects on cognition and behavior. Here, in a preregistered, double-blinded study, we examined how pharmacologically manipulating dopamine altered the effect of tDCS on the speed-accuracy trade-off, which taps ubiquitous strategic operations. Cathodal tDCS was delivered over the left prefrontal cortex and the superior medial frontal cortex before participants (N = 62, 24 males, 38 females) completed a dot-motion task, making judgments on the direction of a field of moving dots under instructions to emphasize speed, accuracy, or both. We leveraged computational modeling to uncover how our interventions altered latent decisional processes driving the speed-accuracy trade-off. We show that dopamine in combination with tDCS (but not tDCS alone nor dopamine alone) not only impaired decision accuracy but also impaired discriminability, which suggests that these manipulations altered the encoding or representation of discriminative evidence. This is, to the best of our knowledge, the first direct evidence implicating dopamine in the way tDCS affects cognition and behavior.SIGNIFICANCE STATEMENT tDCS can improve cognitive and behavioral impairments in clinical conditions; however, a better understanding of its mechanisms is required to optimize future clinical applications. Here, using a pharmacological approach to manipulate brain dopamine levels in healthy adults, we demonstrate a role for dopamine in the effects of tDCS in the speed-accuracy trade-off, a strategic cognitive process ubiquitous in many contexts. In doing so, we provide direct evidence implicating dopamine in the way tDCS affects cognition and behavior.

Individual Differences in Decision Strategy Relate to Neurochemical Excitability and Cortical Thickness.

The speed-accuracy trade-off (SAT), whereby faster decisions increase the likelihood of an error, reflects a cognitive strategy humans must engage in during the performance of almost all daily tasks. To date, computational modeling has implicated the latent decision variable of response caution (thresholds), the amount of evidence required for a decision to be made, in the SAT. Previous imaging has associated frontal regions, notably the left prefrontal cortex and the presupplementary motor area (pre-SMA), with the setting of such caution levels. In addition, causal brain stimulation studies, using transcranial direct current stimulation (tDCS), have indicated that while both of these regions are involved in the SAT, their role appears to be dissociable. tDCS efficacy to impact decision-making processes has previously been linked with neurochemical concentrations and cortical thickness of stimulated regions. However, to date, it is unknown whether these neurophysiological measures predict individual differences in the SAT, and brain stimulation effects on the SAT. Using ultra-high field (7T) imaging, here we report that instruction-based adjustments in caution are associated with both neurochemical excitability (the balance between GABA+ and glutamate) and cortical thickness across a range of frontal regions in both sexes. In addition, cortical thickness, but not neurochemical concentrations, was associated with the efficacy of left prefrontal and superior medial frontal cortex (SMFC) stimulation to modulate performance. Overall, our findings elucidate key neurophysiological predictors, frontal neural excitation, of individual differences in latent psychological processes and the efficacy of stimulation to modulate these.SIGNIFICANCE STATEMENT The speed-accuracy trade-off (SAT), faster decisions increase the likelihood of an error, reflects a cognitive strategy humans must engage in during most daily tasks. The SAT is often investigated by explicitly instructing participants to prioritize speed or accuracy when responding to stimuli. Using ultra-high field (7T) magnetic resonance imaging (MRI), we found that individual differences in the extent to which participants adjust their decision strategies with instruction related to neurochemical excitability (ratio of GABA+ to glutamate) and cortical thickness in the frontal cortex. Moreover, brain stimulation to the left prefrontal cortex and the superior medial frontal cortex (SMFC) modulated performance, with the efficacy specifically related to cortical thickness. This work sheds new light on the neurophysiological basis of decision strategies and brain stimulation.

The impact of cognitive resource constraints on goal prioritization.

Many decisions we face daily entail deliberation about how to coordinate resources shared between multiple, competing goals. When time permits, people appear to approach these goal prioritization problems by analytically considering all goal-relevant information to arrive at a prioritization decision. However, it is not yet clear if this normative strategy extends to situations characterized by resource constraints such as when deliberation time is scarce or cognitive load is high. We evaluated the questions of how limited deliberation time and cognitive load affect goal prioritization decisions across a series of experiments using a gamified experimental task, which required participants to make a series of interdependent goal prioritization decisions. We fit several candidate models to experimental data to identify decision strategy adaptations at the individual subject-level. Results indicated that participants tended to opt for a simple heuristic strategy when cognitive resources were constrained rather than making a general tradeoff between speed and accuracy (e.g., the type of tradeoff that would be predicted by evidence accumulation models). The most common heuristic strategy involved disproportionately weighing information about goal deadlines compared to other goal-relevant information such as the goal's difficulty and the goal's subjective value.

Using mixture modeling to examine differences in perceptual decision-making as a function of the time and method of participant recruitment.

We examine whether perceptual decision-making differs as a function of the time in the academic term and whether the participant is an undergraduate participating for course credit, a paid in-person participant, or a paid online participant recruited via Amazon Mechanical Turk. We use a mixture modeling approach within an evidence accumulation framework that separates stimulus-driven responses from contaminant responses, allowing us to distinguish between performance when a participant is engaged in the task and the consistency in this task focus. We first report a survey showing cognitive psychologists expect performance and response caution to be lower among undergraduate participants recruited at the end of the academic term compared to those recruited near the start, and highest among paid in-person participants. The findings from two experiments using common paradigms revealed very little evidence of time-of-semester effects among course credit participants on accuracy, response time, efficiency of information processing (when engaged in the task), caution, and non-decision time, or consistency in task focus. However, paid in-person participants did tend to be more accurate than the other two groups. Groups showed similar effects of speed/accuracy emphasis on response caution and of discrimination difficulty on information processing efficiency, but the effect of speed/accuracy emphasis on information processing efficiency was less consistent among groups. We conclude that online crowdsourcing platforms can provide quality perceptual decision-making data, but recommend that mixture modeling be used to adequately account for data generated by processes other than the psychological phenomena under investigation.

Information Processing Under Reward Versus Under Punishment.

Much is known about the effects of reward and punishment on behavior, yet little research has considered how these incentives influence the information-processing dynamics that underlie decision making. We fitted the linear ballistic accumulator to data from a perceptual-judgment task to examine the impacts of reward- and punishment-based incentives on three distinct components of information processing: the quality of the information processed, the quantity of that information, and the decision threshold. The threat of punishment lowered the average quality and quantity of information processed, compared with the prospect of reward or no performance incentive at all. The threat of punishment also induced less cautious decision making by lowering people's decision thresholds relative to the prospect of reward. These findings suggest that information-processing dynamics are determined not only by objective properties of the decision environment but also by the higher order goals of the system.

Using Situation Awareness and Workload to Predict Performance in Submarine Track Management: A Multilevel Approach.

OBJECTIVE: Examine the extent to which subjective workload and situation awareness (SA) can predict variance in performance at the between- and within-person levels of analysis in a simulated submarine track management task. BACKGROUND: SA and workload are crucial constructs in human factors that are conceptualized as states that change within individuals over time. Thus, a change in an individual's subjective workload or SA over the course of performing a task should be predictive of their subsequent performance (within-person effects). However, there is little empirical evidence for this. METHOD: Participants monitored displays to track the behaviors of contacts in relationship to their own ship (Ownship) and landmarks. The Situational Awareness Global Assessment Technique measured SA, and the Air Traffic Workload Input Technique measured subjective workload. RESULTS: When a participant's subjective workload rating increased, their subsequent performance decreased, but there was no evidence for within-person effects of SA on performance. We replicated prior between-person level effects of SA; participants with higher SA performed better than those with lower SA. CONCLUSION: Change in an individual's subjective workload rating (but not SA) was predictive of their subsequent performance. Because an increase in SA should increase the extent to which operators hold the knowledge required to perform subsequent tasks, further research is required to examine SA effects on performance at the within-person level. APPLICATION: Adapting automation is more likely to produce optimal outcomes if based on measurement of operator states that predict future task performance, such as workload.

When, not if: the inescapability of an uncertain climate future.

Climate change projections necessarily involve uncertainty. Analysis of the physics and mathematics of the climate system reveals that greater uncertainty about future temperature increases is nearly always associated with greater expected damages from climate change. In contrast to those normative constraints, uncertainty is frequently cited in public discourse as a reason to delay mitigative action. This failure to understand the actual implications of uncertainty may incur notable future costs. It is therefore important to communicate uncertainty in a way that improves people's understanding of climate change risks. We examined whether responses to projections were influenced by whether the projection emphasized uncertainty in the outcome or in its time of arrival. We presented participants with statements and graphs indicating projected increases in temperature, sea levels, ocean acidification and a decrease in arctic sea ice. In the uncertain-outcome condition, statements reported the upper and lower confidence bounds of the projected outcome at a fixed time point. In the uncertain time-of-arrival condition, statements reported the upper and lower confidence bounds of the projected time of arrival for a fixed outcome. Results suggested that people perceived the threat as more serious and were more likely to encourage mitigative action in the time-uncertain condition than in the outcome-uncertain condition. This finding has implications for effectively communicating the climate change risks to policy-makers and the general public.

Uncertainty as knowledge.

This issue of Philosophical Transactions examines the relationship between scientific uncertainty about climate change and knowledge. Uncertainty is an inherent feature of the climate system. Considerable effort has therefore been devoted to understanding how to effectively respond to a changing, yet uncertain climate. Politicians and the public often appeal to uncertainty as an argument to delay mitigative action. We argue that the appropriate response to uncertainty is exactly the opposite: uncertainty provides an impetus to be concerned about climate change, because greater uncertainty increases the risks associated with climate change. We therefore suggest that uncertainty can be a source of actionable knowledge. We survey the papers in this issue, which address the relationship between uncertainty and knowledge from physical, economic and social perspectives. We also summarize the pervasive psychological effects of uncertainty, some of which may militate against a meaningful response to climate change, and we provide pointers to how those difficulties may be ameliorated.

The dynamics of competition and decision-making.

We examine the underlying cognitive mechanisms that govern how competitions play out over time. We used cognitive modeling to examine the dynamic effects of time remaining and relative performance (whether the person is winning or losing) on effort and strategy. In this experiment, participants completed a competitive decision-making task with varying time limits and starting scores, in a repeated-measures design. Participants were tasked with scoring more points than their computerized opponent during a certain time frame, gaining and losing points for correct and incorrect decisions, respectively. The results showed that as the competition deadline approached and as participants drew ahead of their opponent within a competition, they increased effort and became more cautious. Furthermore, the effect of relative score on effort and caution changed over the course of a competition as the deadline approached. These results highlight the importance of considering dynamics when working to understand how competitions unfold as well as the underlying cognitive mechanisms that give rise to the dynamic behavior.

A Pilot Study Using a Standardized Trauma Assessment Tool After Tactical Combat Casualty Care Course: A Comparison of the United States and Ghana.

INTRODUCTION: Assessment, monitoring, and evaluation have been a required part of Global Health Engagement but difficult to accomplish. The current assessment, monitoring, and evaluation frameworks require implementation at the start of the project and are not designed to use for already existing programs. Tactical Combat Casualty Care (TCCC) is a standardized course now offered in 89 countries, but there has not been a standardized method of evaluating the quality across programs. Ghana's TCCC program began in March 2022 and provides a platform for development of a new method of evaluation globally. METHODS: In this study, a standardized trauma scenario was performed by two groups of students, one who completed a TCCC Medical Provider course in Fort Detrick, MD and one who completed the course in Accra, Ghana. The students were scored using a standardized Trauma Assessment Score Sheet and the scores compared across the two groups. RESULTS: The mean Trauma Assessment Score was 58.5% in the United States and 58.3% in Ghana, with no statistically significant difference between the two groups (P-value of .97). When regressed for confounding variables such as years of experience and deployment, the two groups still had no statistically significant difference (P-value of .783). DISCUSSION: The two groups achieved similar mean scores despite significantly different testing environments and experience levels. Written post-test scores did not correlate well due to multiple confounding factors and appear to be a less accurate representation of student understanding and application than the Trauma Assessment Score. CONCLUSION: This study demonstrates use of a standardized scenario with graded checklist to compare between international programs. This can be used to and expanded to compare programs and support quality assurance and medical interoperability.

A systematic investigation into the reliability of inter-temporal choice model parameters.

Decades of work have been dedicated to developing and testing models that characterize how people make inter-temporal choices. Although parameter estimates from these models are often interpreted as indices of latent components of the choice process, little work has been done to examine their reliability. This is problematic because estimation error can bias conclusions that are drawn from these parameter estimates. We examine the reliability of parameter estimates from 11 prominent models of inter-temporal choice by (a) fitting each model to data from three previous experiments with designs representative of those typically used to study inter-temporal choice, (b) examining the consistency of parameters estimated for the same person based on different choice sets, and (c) conducting a parameter recovery analysis. We find generally low correlations between parameters estimated for the same person from the different choice sets. Moreover, parameter recovery varies considerably between models and the experimental designs upon which parameter estimates are based. We conclude that many parameter estimates reported in previous research are likely unreliable and provide recommendations on how to enhance the reliability of inter-temporal choice models for measurement purposes.

Using cognitive modeling to examine the effects of competition on strategy and effort in races and tournaments.

We investigated the effects of two types of competition, races and tournaments (as well as an individual challenge and a do-your-best condition), on two different aspects of performance: effort and strategy. In our experiment, 100 undergraduate participants completed a simple cognitive task under four experimental conditions (in a repeated-measures design) based on different types of competitions and challenges. We used the Linear Ballistic Accumulator to quantify the effects of competition on strategy and effort. The results reveal that competition produced changes in strategy rather than effort, and that trait competitiveness had minimal impact on how people responded to competition. This suggests individuals are more likely to adjust their strategy in competitions, and the uncertainty created by different competition types influences the direction of these strategy adjustments.

Interruptions in healthcare: Modeling dynamic processes and effects at a team level.

Interruptions are associated with increases in medical errors amongst healthcare professionals, yet interventions to reduce interruptions have not been widely successful. While interruptions can be problematic for the interruptee, they may be necessary for the interrupter to maintain patient safety. To understand the emergent effects of interruptions within a dynamic environment, we develop a computational model that describes how nurses make decisions about interruptions and the effects those decisions have at a team level. Simulations reveal the dynamic interplay between urgency, task importance, the cost of being interrupted and team efficiency, depending on the consequences of clinical or procedural error, and shed light on the ways that the risks from interruptions can be better managed.

The causal role of the prefrontal and superior medial frontal cortices in the incidental manipulation of decision strategies.

A key strategic decision one must make in virtually every task context concerns the speed accuracy trade-off (SAT). Experimentally, this ubiquitous phenomenon, whereby response speed and task accuracy are inversely related, is typically studied by explicitly instructing participants to adjust their strategy: by either focusing on speed, or on accuracy. Computational modelling has been applied to deconvolve the latent decision processes involved in the SAT, with considerable evidence suggesting that response caution (the amount of evidence needed for a decision to be reached) is a key variable in the setting of SAT strategy. Neuroimaging has implicated the prefrontal cortex, the pre-supplementary motor area (preSMA), and the striatum in the setting of response caution. In addition, brain stimulation has provided causal evidence for the involvement of the left prefrontal cortex and superior medial frontal cortex (SMFC, which includes the preSMA) in adjustments of response caution following explicit instructions, although stimulation of the two regions has dissociable effects. Here, in a double-blind and preregistered study we investigated the role of these two regions using an incidental manipulation of SAT strategy - via stimulus signal variability - which has previously been shown to influence decision confidence. We again found tDCS applied to both regions modulated response caution, and there was a dissociation: stimulating prefrontal cortex increased, and stimulating SMFC decreased, response caution. These findings provide further support for key, but dissociable, roles of these brain regions in decision strategies whether they are implemented explicitly or incidentally.

Changes in affect during the pursuit of performance goals.

The aim of this article is to examine how affect changes when people are pursuing performance goals. We do this using the circumplex model of affect, in which a person's current affective state is represented as a point on a plane defined by the latent dimensions of pleasure and activation. We test competing hypotheses regarding the direction of changes within this 2-dimensional space. The first set of hypotheses are derived from Carver and Scheier's (1998) theory of self-regulation, which predicts that changes in the prospects of goal attainment should produce changes along axes offset 45° from the pleasure and activation dimensions. The second set of hypotheses are derived from the concept of core affect (Russell, 2003), which predicts that changes in the prospects of goal attainment should produce changes in pleasure, while changes in task demands should produce changes in activation. Two studies are reported in which participants provided ratings of momentary affect during goal pursuit. We developed a latent change model to estimate the direction and magnitude of changes in affect attributable to changes in the prospects of goal attainment and task demand. The results are more consistent with the hypotheses derived from the core affect account than with the hypotheses derived from the Carver and Scheier account. Theoretical and practical implications are discussed, with a focus on prospects for the development of an integrative theory, which accounts for both the motivational and affective components of goal pursuit. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Evaluation of Gender Disparity in Tactical Combat Casualty Care.

INTRODUCTION: Women comprise nearly 19% of the U.S. military and now serve in almost all operational roles, increasing their risk of combat trauma and injuries.3 Data from the Joint Trauma Registry during Operation Enduring Freedom shows that battle-injured females had a higher case fatality rate at 36% compared to their male counterparts at 17%.1 The Tactical Combat Casualty Care curriculum is used to prepare battlefield medics to provide immediate care to wounded service members, but fails to address differences in the care of female versus male casualties. The students, who are presented with life-threatening injuries in simulated trauma scenarios, may be slower to assess, identify, and treat injuries in female patients as compared with male patients. MATERIALS AND METHODS: This observational program analysis was reviewed by the Uniformed Services University Human Research Protections Program and approved for execution as an exempt protocol under the provision of 32 CFR 219.104(d)(1). The study assessed the performance of male and female Mexican military personnel during a Tactical Combat Casualty Care course, using standardized trauma scenarios. Anatomically, correct male and female manikins were used to compare response time for different gender patients presenting with the same injuries. RESULTS: There was a statistically significant increase in time required to complete an initial blood sweep, identify a gunshot wound to the chest, and call for medical evacuation when treating a female patient compared to a male patient. CONCLUSIONS: A lack of female representation in trauma training may have contributed to the higher case fatality rate of female soldiers compared to male soldiers during Operation Enduring Freedom. Female live actors and Gender Retrofit Kits can augment trauma casualty assessment and treatment training scenarios and better prepare our forces to respond to life-threatening emergencies.

Sustainable Tactical Combat Casualty Care Implementation in Ghana: A Model for Future Development.

INTRODUCTION: Department of Defense policy for Global Health Engagement (GHE) activities prioritizes interoperability and sustainability within security cooperation, yet these elements, along with monitoring and evaluation, are not well reported. MATERIALS AND METHODS: In this case study reviewing 1 year after the implementation of a Tactical Combat Casualty Care (TCCC) program in Ghana, the Ghana Armed Forces (GAF) has conducted five independent TCCC Medical Provider Tier courses and four All Service Member Tier courses. They have certified 240 students, 21 instructors, and appointed 2 affiliate faculty members with the National Association of Emergency Medical Technicians (NAEMT). Ghana is one of the only four active NAEMT-certified TCCC training sites in Africa. The principles that allowed for this achievement could serve as a 'best practice' model for GHE. RESULTS: Principally, the GAF took ownership of the program from the onset. The program also had an extensive preparatory phase 0 before initiating phase 1 on the ground training, which included establishing leadership and a medical modeling and simulation center pre-engagement. The triple partnership achieved between the U.S. DoD's African Peacekeeping Rapid Response Partnership, the GAF, and the NAEMT, a civilian certifying organization, allowed the sustainment of the TCCC program. African Peacekeeping Rapid Response Partnership also built on experience from other programs to develop a multifaceted model. Persisting challenges to the current program and future GHEs include continued funding and equipment, the associated issues with rapid expansion, and monitoring and evaluation, which all pose barriers to continued sustainment. CONCLUSION: The year sustainment of the GAF TCCC training program provides hope as a model for future DoD GHEs to attain sustainable development and points to the possibility of long-term programs with meaningful outcomes.

Effectiveness of isopropyl myristate/cyclomethicone D5 solution of removing cuticular hydrocarbons from human head lice (Pediculus humanus capitis).

BACKGROUND: In the treatment of human head lice infestation, healthcare providers are increasingly concerned about lice becoming resistant to existing pesticide treatments. Traditional pesticides, used to control these pests, have a neurological mechanism of action. This publication describes a topical solution with a non-traditional mechanism of action, based on physical disruption of the wax layer that covers the cuticle of the louse exoskeleton. This topical solution has been shown clinically to cure 82% of patients with only a 10-minute treatment time, repeated once after 7 days. All insects, including human head lice, have a wax-covered exoskeleton. This wax, composed of hydrocarbons, provides the insect with protection against water loss and is therefore critical to its survival. When the protective wax is disrupted, water loss becomes uncontrollable and irreversible, leading to dehydration and death. A specific pattern of hydrocarbons has been found in all of the head louse cuticular wax studied. Iso-octane effectively removes these hydrocarbons from human head lice's cuticular wax. METHODS: A method of head louse cuticle wax extraction and analysis by gas chromatography was developed. Human head lice (Pediculus humanus capitis) were collected from infested patients and subjected to any of three extraction solvents comprising either the test product or one of two solvents introduced as controls. A gas chromatograph equipped with a flame ionization detector (GC/FID) was used to determine the presence of hydrocarbons in the three head lice extracts. RESULTS: In the study reported herein, the test product isopropyl myristate/cyclomethicone D5 (IPM/D5) was shown to perform comparably with iso-octane, effectively extracting the target hydrocarbons from the cuticular wax that coats the human head louse exoskeleton. CONCLUSIONS: Disruption of the integrity of the insect cuticle by removal of specific hydrocarbons found in the cuticular wax appears to offer a mechanism for killing lice without the likelihood of encountering genetic resistance.

tDCS augments decision-making efficiency in an intensity dependent manner: A training study.

The application of transcranial direct current stimulation (tDCS) to the prefrontal cortex has the potential to improve performance more than cognitive training alone. Such stimulation-induced performance enhancements can generalize beyond trained tasks, leading to benefits for untrained tasks/processes. We have shown evidence that stimulation intensity has non-linear effects on augmenting cognitive training outcomes. However, it is currently unclear how stimulation intensity augments cognitive processing to impact training and transfer effects. Here, we applied decision-making modelling via the linear ballistic accumulator framework to understand what aspects of cognitive processes underlying speeded single-/dual-task decision-making performance change with tDCS intensity. One hundred and twenty-three participants were split into four groups: sham, 0.7 mA, 1.0 mA and 2.0 mA stimulation intensities. Participants completed four training sessions whilst tDCS was delivered. The 0.7 mA & 1.0 mA intensities provided the greatest benefit for performance (increased decision-making efficiency as measured by drift rates) on the trained task - more than sham or 2.0 mA stimulation. The latent decision components integrated both accuracy and reaction times to estimate performance more broadly. We see an inverted u-shaped function of stimulation intensity and cognitive performance in the trained-on task, where either no stimulation or too much stimulation is sub-optimal for performance. By contrast, 1.0 mA and 2.0 mA intensities led to increased drift rates in an untrained (transfer) single task. In sum, tDCS intensity non-linearly modulates cognitive processes related to decision-making efficiency.