Successful voluntary recruitment of cognitive control under acute stress

Prospective reward in dual task induces a bias towards action at the cost of less accurate Task 2 performance

In dual tasks, with a visual-manual choice reaction time task in Task 1 and a go/no-go task in Task 2, not responding to Task 2 can have adverse effects on Task 1 performance, as demonstrated by no-go backward crosstalk effects (no-go BCE). Here, the response inhibition required to not respond to Task 2 spills over and slows response execution in Task 1. Over three experiments, we investigated whether the prospect of reward, which is a potent cognitive control modulator, influences no-go BCE. In Experiment 1, reward for fast and accurate responses in both tasks was modulated as a within-subject factor, and in Experiments 2 and 3, as a between-subject factor. The results revealed three major insights. In all three experiments, reward led to faster Task 1 and Task 2 performance. Second, despite this speeding, the no-go BCE was not modulated by reward. Finally, the reward led to more errors in Task 2 no-go trials. These results reveal a reward-induced bias for action, suggesting better preparedness to respond and, consequently, larger commission errors in Task 2 no-go trials. The absence of a reward-based modulation of the no-go BCE indicates that the reward-induced bias for action does not necessarily translate into larger response inhibition. These findings point towards the complex interactions between reward and inhibitory control and shed light on the potentials and limitations of reward-based modulation of dual-task interference.

The affective consequences of response inhibition determine no-go-based crosstalk effects in dual tasks

Backward crosstalk effects (BCEs) are observed in dual-task studies when characteristics of Task 2 influence Task 1 performance. When Task 2 is a go/no-go task, responses in Task 1 are slower when Task 2 is a no-go as compared with a go trial. This no-go BCE has been argued to be due to response inhibition spilling over from Task 2 to Task 1. Growing evidence shows that response inhibition elicits negative affect leading to affective devaluation of associated stimuli. We tested for a functional role of the negative affective consequence of response inhibition in the no-go BCE by investigating its interaction with affective processing in Task 1. In four experiments, Task 1 was a valence categorisation task, and Task 2 a go/no-go task. In all experiments, the no-go BCE strongly depended on affective processing in Task 1. While this modulation could be attributed to an affective (mis)match between stimulus features in both tasks in Experiments 1 and 2, Experiments 3 and 4 provided evidence for an affective (mis)match between stimulus valence in Task 1 and affective consequences of Task 2 response inhibition. The results are discussed in the context of current theories of no-go BCEs in dual tasks.

No effects of acute stress on monetary delay discounting: A systematic literature review and meta-analysis

Many everyday decisions, including those concerning our health, finances and the environment, involve choosing between a smaller but imminent reward (e.g., €20 now) and a later but larger reward (e.g., €40 in a month). The extent to which an individual prefers smaller imminent rewards over larger delayed rewards can be measured using delay discounting tasks. Acute stress induces a cascade of biological and psychological responses with potential consequences for how individuals think about the future, process rewards, and make decisions, all of which can impact delay discounting. Several studies have shown that individuals focus more on imminent rewards under stress. These findings have been used to explain why individuals make detrimental choices under acute stress. Yet, the evidence linking acute stress to delay discounting is equivocal. To address this uncertainty, we conducted a meta-analysis of 11 studies (14 effects) to systematically quantify the effects of acute stress on monetary delay discounting. Overall, we find no effect of acute stress on delay discounting, compared to control conditions (SMD = -0.18, 95% CI [-0.57, 0.20], p = 0.32). We also find that neither the gender/sex of the participants, the type of stressor (e.g., physical vs. psychosocial) nor whether monetary decisions were hypothetical or incentivized (i.e. monetary decisions were actually paid out) moderated the impact of acute stress on monetary delay discounting. We argue that establishing the effects of acute stress on the separate processes involved in delay discounting, such as reward valuation and prospection, will help to resolve the inconsistencies in the field.

The effect of chronic academic stress on intentional forgetting

This study investigated whether chronic academic stress could affect the directed forgetting (DF) process. Both the stress group (undergoing preparation for a major academic examination) and the control group performed a DF task. A forgetting cue was presented after a to-be-forgotten (TBF) word, whereas no cue appeared after a to-be-remembered (TBR) item in the study phase. An old/new recognition test was used in the test phase. The results showed that (1) the stress group showed a higher level of self-reported stress, state anxiety, negative affect, and decreased cortisol awakening response (CAR) compared with the control group, suggesting a higher level of stress for the stress group. (2) Both groups showed superior recognition performance of TBR than TBF items, suggesting a DF effect. (3) The stress group showed inferior recognition performance of TBF items and an enhanced DF effect compared with the control group. These results demonstrated that the intentional memory control process might be enhanced under chronic academic stress.

Acute stress impacts reaction times in older but not in young adults in a flanker task

Acute psychosocial stress effects on inhibition have been investigated in young adults, but little is known about these effects in older adults. The present study investigated effects of the Trier Social Stress Test on cognitive inhibition (i.e., ability to ignore distracting information) using a cross-over (stress vs. control) design in healthy young (N = 50; 18-30 years; Mage = 23.06) versus older adults (N = 50; 65-84 years; Mage = 71.12). Cognitive inhibition was measured by a letter flanker task and psychophysiological measures (cortisol, heart rate, subjective stress) validated the stress induction. The results showed that while stress impaired overall accuracy across age groups and sessions, stress (vs. control) made older adults' faster in session 1 and slower in session 2. Given that session 2 effects were likely confounded by practice effects, these results suggest that acute psychosocial stress improved older adults' RTs on a novel flanker task but impaired RTs on a practiced flanker task. That is, the interaction between stress and learning effects might negatively affect response execution when testing older adults on flanker tasks. If confirmed by future research, these results might have important implications especially in settings where repeated cognitive testing is performed under acute stress.

Left dorsolateral prefrontal cortex activation can accelerate stress recovery: A repetitive transcranial stimulation study

In this study, a single high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) session was applied over the left dorsolateral prefrontal cortex (DLPFC) after a moderate-to-intense stressor to investigate whether left DLPFC stimulation could regulate cortisol concentration after stress induction. Participants were randomly divided into three groups (stress-TMS, stress, and placebo-stress). Stress was induced in both the stress-TMS and stress groups using the Trier Social Stress Test (TSST). The placebo-stress group received a placebo TSST. In the stress-TMS group, a single HF-rTMS session was applied over the left DLPFC after TSST. Cortisol was measured across the different groups, and each group's responses to the stress-related questionnaire were recorded. After TSST, both the stress-TMS and stress groups reported increased self-reported stress, state anxiety, negative affect, and cortisol concentration compared with the placebo-stress group, indicating that TSST successfully induced a stress response. Compared with the stress group, the stress-TMS group exhibited reduced cortisol levels at 0, 15, 30, and 45 min after HF-rTMS. These results suggest that left DLPFC stimulation after stress induction might accelerate the stress recovery.

The Insidious Influence of Stress: An Integrated Model of Stress, Executive Control, and Psychopathology

Although exposure to acute stress undoubtedly contributes to psychopathology, most individuals do not develop psychopathology following stress exposure. To explain this, biological, emotional, and cognitive responses to stress have been implicated, but individual differences in executive control (i.e., top-down control of cognition and behavior) measured in response to stress has only recently emerged as a potential factor contributing to psychopathology. In this review, we introduce a model-the integrated model of stress, executive control, and psychopathology-positing how the impairing effects of acute stress on executive control can contribute to psychopathology. We link to research on biological, emotional, and cognitive processes, all of which can be impacted by executive control, to propose a framework for how poorer executive control under conditions of acute stress can contribute to psychopathology. This integrated model is intended to further our understanding of who is more susceptible to the negative consequences of stress.

The effect of transcutaneous auricular vagus nerve stimulation (taVNS) on cognitive control in multitasking

Current research in brain stimulation suggests transcutaneous auricular vagus nerve stimulation (taVNS) as a promising tool to modulate cognitive functions in healthy populations, such as attention, memory, and executive functions. Empirical evidence in single-task contexts, suggests that taVNS promotes holistic task processing, which strengthens the integration of multiple stimulus features in task processing. However, it is unclear how taVNS might affect performance in multitasking, where the integration of multiple stimuli leads to an overlap in stimulus response translation processes, increasing the risk of between-task interference (crosstalk). In a single-blinded, sham-controlled, within-subject design, participants underwent taVNS while performing a dual task. To assess the effects of taVNS, behavioral (reaction times), physiological (heart rate variability, salivary alpha-amylase), and subjective psychological variables (e.g., arousal) were recorded over three cognitive test blocks. Our results revealed no overall significant effect of taVNS on physiological and subjective psychological variables. However, the results showed a significant increase in between-task interference under taVNS in the first test block, but not in the subsequent test blocks. Our findings therefore suggest that taVNS increased integrative processing of both tasks early during active stimulation.

Modulation of the executive control network by anodal tDCS over the left dorsolateral prefrontal cortex improves task shielding in dual tasking

Task shielding is an important executive control demand in dual-task performance enabling the segregation of stimulus-response translation processes in each task to minimize between-task interference. Although neuroimaging studies have shown activity in left dorsolateral prefrontal cortex (dlPFC) during various multitasking performances, the specific role of dlPFC in task shielding, and whether non-invasive brain stimulation (NIBS) may facilitate task shielding remains unclear. We therefore applied a single-blind, crossover sham-controlled design in which 34 participants performed a dual-task experiment with either anodal transcranial direct current stimulation (atDCS, 1 mA, 20 min) or sham tDCS (1 mA, 30 s) over left dlPFC. Task shielding was assessed by the backward-crosstalk effect, indicating the extent of between-task interference in dual tasks. Between-task interference was largest at high temporal overlap between tasks, i.e., at short stimulus onset asynchrony (SOA). Most importantly, in these conditions of highest multitasking demands, atDCS compared to sham stimulation significantly reduced between-task interference in error rates. These findings extend previous neuroimaging evidence and support modulation of successful task shielding through a conventional tDCS setup with anodal electrode over the left dlPFC. Moreover, our results demonstrate that NIBS can improve shielding of the prioritized task processing, especially in conditions of highest vulnerability to between-task interference.

Hedonic Consumption in Times of Stress: Reaping the Emotional Benefits Without the Self-Regulatory Cost

Hedonic consumption is pleasant but can interfere with the capacity to self-regulate. In stressful moments, when self-regulation is arguably still important, individuals often indulge in hedonic consumption. In two experiments, we investigate whether hedonic consumption negatively affects self-regulation under moderately stressful conditions and whether selecting hedonic consumption under moderately stressful conditions is driven by high or low self-control. In both studies, participants were randomly exposed to a mental arithmetic task that was either completed under time pressure with performance feedback (moderate stress) or without time pressure and without feedback (no stress). Experiment 1 assigned participants to a hedonic (vs. neutral) consumption task and then measured impulse control via a color-word Stroop task. Experiment 2 measured self-control as a second independent variable and recorded hedonic (vs. neutral) consumption. The results show that moderate stress buffered the negative effect that hedonic consumption has on self-regulation under no stress conditions and that high rather than low self-control predicts hedonic over neutral consumption under stress. These findings indicate that hedonic consumption in response to moderate stress may be a strategic choice to reap the pleasure benefit of hedonic consumption while the costs to self-regulation are low.

Does older adults' cognition particularly suffer from stress? A systematic review of acute stress effects on cognition in older age

This literature review provides the first comprehensive qualitative and quantitative systematic synthesis of acute laboratory stress effects on older adults' cognition by specifying the direction and magnitude of those effects both overall and for different cognitive processes separately. A systematic literature search was performed, and effect sizes estimated whenever possible. We found meta-analytical evidence that stress has negative effects on older adults' verbal fluency (g_adj = -0.53, 95 % CI [-2.70, 1.63]), null-to-negative effects on episodic memory (g_adj = -0.26, 95 % CI [-0.44, -0.08]), null effects on executive functions (g_adj = 0.07, 95 % CI [-0.31, 0.46]), and enhancing effects on working memory (g_adj = 0.16, 95 % CI [-0.01, 0.33]). Relating these findings to those in young adults, notable differences emerged for some cognitive functions, such as opposing effects on working memory between age groups. Our review further reveals that stress effects on older adults' memory retention, associative memory, prospective memory, interference control or cognitive flexibility are heavily understudied. We provide a conceptual and methodological framework for future studies in older adults.

No reduction of between-task interference in a dual-task with a repeating sequence of SOAs

A frequent observation in dual-tasking is that spatially or conceptually (in)compatible Task 2 response features can interfere with responses in Task 1 (backward crosstalk effect; BCE). Such between-task interference is, at least to some degree, under strategic control. It has been shown that the size of the BCE can be modulated by instructions, contextual regularities, recent experience of conflict, and motivational factors. Especially large temporal task overlap (i.e., short stimulus onset asynchrony, SOA) represents a condition of potentially high levels of between-task interference. Accordingly, Fischer and Dreisbach (2015) showed that specific stimuli, associated with mostly short SOAs, were able to reduce the size of the BCE. In the present study, we investigated whether a regular sequence of SOAs can also be used for contextual regulation of the BCE. In a dual-task with spatially (in)compatible hand- and foot-responses, we implemented a repeating sequence of three SOAs. If participants learned this sequence and used it for task shielding, the BCE should decrease over time in the sequence blocks, but should increase in a subsequent random block. However, this prediction was not supported in two experiments (N = 32 each). Instead, the size of the BCE was constant across all blocks (BFs₁₀ < 1 for the respective interactions). This is an important result, as it points at the necessity to discover the appropriate conditions allowing implicit SOA sequence learning and to further investigate whether or how the resulting implicit sequence knowledge can serve shielding against between-task interference.

Two types of between-task conflict trigger respective processing adjustments within one dual-task

In dual tasking, two different kinds of between-task conflict occur. Because in both cases, Task 2 characteristics affect Task 1 performance, they are commonly referred to as backward crosstalk effects (BCE): One with a conflict at the response selection stage when Task 1 and Task 2 have dimensional overlap (the compatibility-based BCE) and one with a conflict at the motor execution stage when response inhibition resulting from a Task 2 no-go-trial interferes with simultaneous response execution in Task 1 (the no-go BCE). Recent research suggests that these BCEs differ not only in their underlying cognitive processes, but also in how cognitive control is regulated. Here, we investigated whether both can be produced in a single dual-task set up and whether they trigger their respective processing adjustments (i.e., a sequential modulation). In three experiments, participants categorized numbers as smaller or larger than 5 in Task 1. In Experiments 1 and 2, numbers were responded to irrespective of numerical size (go-response) as Task 2. Further, dimensional overlap was provided by (non)corresponding size information in both stimuli, which was strengthened in Experiment 2 by presenting S1 and S2 in the same/different color in compatible/incompatible trials, respectively. In Experiment 3, participants were required to perform a number-size categorization also in Task 2, establishing strong dimensional overlap by activating the same or different response categories in both tasks. In all three experiments, the number 5 served as the no-go stimulus in Task 2 to induce a no-go BCE on Task 1. By and large, our results show that both types of between-task conflicts not only occur within the same type of BCE, but they also trigger their respective sequential modulation.

The discrepant effect of acute stress on cognitive inhibition and response inhibition

This study aimed to investigate how acute stress impinges on individual's cognitive inhibition and response inhibition abilities. Electroencephalography was adopted when 35 healthy adult females performing the No Go Flanker task before and after the Trier Social Stress Test. Both inhibition processes evoked N2 and P3 components, but only the response inhibition evoked the late positive potential (LPP), indicating the response inhibition needed continuous cognitive effort to inhibit the prepotent response. The N2 and the P3 amplitudes were decreased, while the LPP amplitudes were increased under acute stress. These results suggested that acute stress caused the detrimental effect by occupying cognitive resources. Contrastingly, individuals actively regulated and made more efforts to counteract the detrimental effect of acute stress on response inhibition. Thus, acute stress impaired cognitive inhibition but did not affect response inhibition.

Subjective stress and proactive and reactive cognitive control strategies

Acute stress likely impacts cognitive control. Little is known, however, about the effects that acute stress may have on specific cognitive control strategies. The goal of this research was to investigate the effects of acute stress on proactive and reactive control strategies. Participants completed the Trier Social Stress Test or control tasks. Use of proactive and reactive control strategies was measured with the AX-Continuous Performance Test. The Trier Social Stress Test was effective at producing subjective, cortisol, and heart rate stress responses, but there was no significant effect of stress on use of proactive or reactive control strategies in between-group analyses. However, higher subjective stress responses during performance of the AX-Continuous Performance Test were associated with less frequent use of a proactive control strategy and more frequent use of a reactive control strategy within the stress group.

Social exclusion modulates dual mechanisms of cognitive control: Evidence from ERPs

Many studies have investigated how social exclusion influences cognitive control but reported inconsistent findings. Based on the dual mechanisms of control framework, this study investigated how social exclusion influences proactive and reactive modes of control (Experiment 1) and the underlying mechanisms (Experiment 2). The Cyberball game was used to manipulate social exclusion. Eighty-six female participants (about 40 for each experiment) performed cognitive control tasks while event-related potentials were recorded. In Experiment 1, an AX Continuous Performance Task (AX-CPT) was adopted to differentiate between proactive and reactive control. Results showed that social exclusion weakened proactive control but enhanced reactive control, as reflected by the weaker proactive control indicators (i.e., P3b and CNV), but strengthened reactive control indicators (accuracy and N2) in excluded individuals. More importantly, in Experiment 2, through varying in whether task cues were available before or after target onset in a cued-flanker task, we further manipulated the possibility of engaging proactive control, and found the weakened proactive control could be attributed to both impaired cognitive ability and lowered motivation to engage proactive control in excluded individuals. Together, these results provide insight on how social exclusion influences cognitive control and suggest promising implications for designing effective interventions to relieve the negative impact of social exclusion.

Mindfulness Training, Implicit Bias, and Force Response Decision-making

OBJECTIVE

The goal of this study was to assess the preliminary efficacy of a Mindfulness-Based Training (Mindfulness-based Resilience Training; MBRT) in improving weapon identification among Law Enforcement Officers (LEOs).

METHODS

Participants (N = 61) were randomly assigned to either MBRT or a no-intervention control group (NIC). A self-report questionnaire assessing mindfulness and a computerized measure assessing implicit stereotype reliance were administered at baseline, post-training, and three months following intervention completion. We also collected information about meditation practice outside of the training for LEOs in the MBRT group.

RESULTS

Inferential analyses yielded improvements in mindfulness in the MBRT group compared to NIC. Analyses did not provide evidence for implicit stereotype reliance at baseline and therefore did not yield a significant impact of MBRT versus NIC on implicit stereotype reliance, ps > .05; however, participants across both conditions exerted more control when responding to Black male targets compared to White male targets, F(1,74) = 3.98, p = .05, 95% CI [-.05, -.01], d = .36.

CONCLUSIONS

Our results do not provide evidence for the impact of MBRT on weapon identification, but do suggest that LEOs exerted more effort when responding to images of Black males compared to White males. We discuss recommendations for future clinical trials assessing implicit stereotype reliance, viz., that researchers utilize measures more sensitive to a wider range of LEO samples and with higher ecological validity, and we discuss potential reasons why our results do not align with past research.

Evaluation and Classification of Physical and Psychological Stress in Firefighters using Heart Rate Variability

Stress detection has a huge potential for disease prevention and management, and to improve the quality of life of people. Also, work safety can be improved if stress is timely and reliably detected. The availability of low-cost consumer wearable devices that monitor vital-signs, gives access to stress detection schemes. Heart rate variability (HRV), a stress-related vital-sign, was derived from wearable device data to reliably determine stress-levels. In order to build and train a deployable stress-detector, we collected labeled HRV data in controlled environments, where subjects were exposed to physical, psychological and combined stress. We then applied machine learning to separate and identify the different stress types and understand the relationship with HRV data. The resulting C5 decision tree model is capable of identifying the stress type with 88% accuracy, in a 1-minute time window. For the first time physical and psychological stress can be distinguished with a 1-minute time resolution from smoke-divers, firefighters, who enter high-risk environments to rescue people, and experience intense physical and psychological stress. To improve our model, we created an integrated system to acquire expert labels in real-time from firefighters during their training in a Rescue Maze. A next goal is to transfer the algorithms into generic systems for monitoring and coaching high-risk professionals to improve their stress resilience during training and reduce their risk in the field.

Embodied cognition in multitasking: increased hand-specific task shielding when stimuli are presented near the hand

The proximity of hand position alters the processing of visual stimuli. Stimuli presented close (proximal) to hands receive an enhanced allocation of visual attention compared to stimuli presented far (distal) from hands. In the present dual-task study we studied the consequences of this preferential processing when the stimulus for Task 1 (S1) and the stimulus for Task 2 (S2) were presented together and were assigned to specific response hands (R1 and R2) located proximal (at the monitor) versus distal (in the lap) to the stimuli. In two experiments, we tested whether stimulus-hand proximity affected the extent of between-task interference (i.e., influence of additional Task 2 processing on primary Task 1 processing). In Experiment 1, results showed that stimulus-hand proximity reduced the amount of between-task interference compared to the distal stimulus-hand condition. Extending these findings, in Experiment 2 a further reduction of between-task interference was obtained when a single hand was located at the monitor instead of two hands. These results are inconsistent with the assumption of a generally increased attentional processing benefit for multiple stimuli within hand space. Instead, these findings speak for a hand-specific processing benefit that supports more separate processing of two tasks. Together these findings demonstrate that stimulus-hand proximity affects the quality of multiple task performance, which is discussed in the context of both, basic and applied cognitive research.

Shielding and relaxation in multitasking: Prospect of reward counteracts relaxation of task shielding in multitasking

Performing two similar tasks at the same time requires the shielding of the prioritized Task 1 from interference of additional Task 2 processing (between-task interference). In the present study we tested how motivational factors such as prospect of reward might drive shifts between increased proactive control, enabling task shielding, and reduced proactive control resulting in relaxed task shielding. In Experiment 1 an instruction-induced prioritization of Task 1 over Task 2 resulted in initially reduced between-task interference. With increasing time on task, however, between-task interference continuously increased, presumably because participants engaged less in proactive control resulting in reduced task shielding. In Experiment 2 the prospect of reward activated proactive control as indicated by reduced between-task interference in the Reward than in the No reward condition. In Experiment 3, we directly compared the performance of a Reward and a No reward group in a between-subject design. Whereas between-task interference again continuously increased over time in the No reward group, indicating a relaxed mode of task shielding, the Reward group displayed constant small between-task interference over time, suggesting maintained high levels of task shielding. Together these findings speak in favor of an impressive flexibility in regulating cognitive control engagement in multitasking situations. This not only shows the capacity for optimization of multitasking performance by motivational incentives but also further supports assumptions of the strategic nature of assumed processing limitations (bottlenecks) in dual-task performance.