The role of prefrontal cortex in resolving distractor interference

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.

Domain-Specific Cognitive Impairment Reflects Prefrontal Dysfunction in Aged Common Marmosets

Age-related cognitive impairment is not expressed uniformly across cognitive domains. Cognitive functions that rely on brain areas that undergo substantial neuroanatomical changes with age often show age-related impairment, whereas those that rely on brain areas with minimal age-related change typically do not. The common marmoset has grown in popularity as a model for neuroscience research, but robust cognitive phenotyping, particularly as a function of age and across multiple cognitive domains, is lacking. This presents a major limitation for the development and evaluation of the marmoset as a model of cognitive aging and leaves open the question of whether they exhibit age-related cognitive impairment that is restricted to some cognitive domains, as in humans. In this study, we characterized stimulus-reward association learning and cognitive flexibility in young adults to geriatric marmosets using a Simple Discrimination task and a Serial Reversal task, respectively. We found that aged marmosets show transient impairment in learning-to-learn but have conserved ability to form stimulus-reward associations. Furthermore, aged marmosets have impaired cognitive flexibility driven by susceptibility to proactive interference. As these impairments are in domains critically dependent on the prefrontal cortex, our findings support prefrontal cortical dysfunction as a prominent feature of neurocognitive aging. This work positions the marmoset as a key model for understanding the neural underpinnings of cognitive aging.

Domain-specific cognitive impairment reflects prefrontal dysfunction in aged common marmosets

Age-related cognitive impairment is not expressed uniformly across cognitive domains. Cognitive functions that rely on brain areas that undergo substantial neuroanatomical changes with age often show age-related impairment, while those that rely on brain areas with minimal age-related change typically do not. The common marmoset has grown in popularity as a model for neuroscience research, but robust cognitive phenotyping, particularly as a function of age and across multiple cognitive domains, is lacking. This presents a major limitation for the development and evaluation of the marmoset as a model of cognitive aging, and leaves open the question of whether they exhibit age-related cognitive impairment that is restricted to some cognitive domains, as in humans. In this study, we characterized stimulus-reward association learning and cognitive flexibility in young adults to geriatric marmosets using a Simple Discrimination and a Serial Reversal task, respectively. We found that aged marmosets show transient impairment in "learning-to-learn" but have conserved ability to form stimulus-reward associations. Furthermore, aged marmosets have impaired cognitive flexibility driven by susceptibility to proactive interference. Since these impairments are in domains critically dependent on the prefrontal cortex, our findings support prefrontal cortical dysfunction as a prominent feature of neurocognitive aging. This work positions the marmoset as a key model for understanding the neural underpinnings of cognitive aging.

Significance Statement

Aging is the greatest risk factor for neurodegenerative disease development, and understanding why is critical for the development of effective therapeutics. The common marmoset, a short-lived non-human primate with neuroanatomical similarity to humans, has gained traction for neuroscientific investigations. However, the lack of robust cognitive phenotyping, particularly as a function of age and across multiple cognitive domains limits their validity as a model for age-related cognitive impairment. We demonstrate that aging marmosets, like humans, have impairment that is specific to cognitive domains reliant on brain areas that undergo substantial neuroanatomical changes with age. This work validates the marmoset as a key model for understanding region-specific vulnerability to the aging process.

Interhemispheric Connectivity Supports Load-Dependent Working Memory Maintenance for Complex Visual Stimuli

Abstract Introduction: One manipulation used to study the neural basis of working memory (WM) is to vary the information load at encoding, then measure activity and connectivity during maintenance in the delay period. A hallmark finding is increased delay activity and connectivity between frontoparietal brain regions with increased load. Most WM studies, however, employ simple stimuli during encoding and unfilled intervals during the delay. In this study, we asked how delay period activity and connectivity change during low and high load maintenance of complex stimuli. Methods: Twenty-two participants completed a modified Sternberg WM task with two or five naturalistic scenes as stimuli during scalp electroencephalography (EEG). On each trial, the delay was filled with phase-scrambled scenes to provide a visual perceptual control with similar color and spatial frequency as presented during encoding. Functional connectivity during the delay was assessed by the phase-locking value (PLV). Results: Results showed reduced theta/alpha delay activity amplitude during high compared with low WM load across frontal, central, and parietal sources. A network with higher connectivity during low load consisted of increased PLV between (1) left frontal and right posterior temporal sources in the theta/alpha bands, (2) right anterior temporal and left central sources in the alpha and lower beta bands, and (3) left anterior temporal and posterior temporal sources in the theta, alpha, and lower beta bands. Discussion: The findings suggest a role for interhemispheric connectivity during WM maintenance of complex stimuli with load modulation when limited attentional resources are essential for filtering. Impact statement The patterns of brain connectivity subserving working memory (WM) have largely been investigated to date using simple stimuli, including letters, digits, and shapes and during unfilled WM delay intervals. Fewer studies describe functional connectivity changes during the maintenance of more naturalistic stimuli in the presence of distractors. In the present study, we employed a scene-based WM task during electroencephalography in healthy humans and found that during low-load WM maintenance with distractors increased interhemispheric connectivity in frontotemporal networks. These findings suggest a role for increased interhemispheric connectivity during maintenance of complex stimuli when attentional resources are essential for filtering.

OUP accepted manuscript

Working memory (WM) allows goal-relevant information to be encoded and maintained in mind, even when the contents of WM are incongruent with the immediate environment. While regions of heteromodal cortex are important for WM, the neural mechanisms that relate to individual differences in the encoding and maintenance of goal-relevant information remain unclear. Here, we used behavioral correlates of two large-scale heteromodal networks at rest, the default mode (DMN) and frontoparietal (FPN) networks, to understand their contributions to distinct features of WM. We assessed each individual’s ability to resist distracting information during the encoding and maintenance phases of a visuospatial WM task. Individuals with stronger connectivity of DMN with medial visual and retrosplenial cortex were less affected by encoding distraction. Conversely, weaker connectivity of both DMN and FPN with visual regions was associated with better WM performance when target information was no longer in the environment and distractors were presented in the maintenance phase. Our study suggests that stronger coupling between heteromodal cortex and visual–spatial regions supports WM encoding by reducing the influence of concurrently presented distractors, while weaker visual coupling is associated with better maintenance of goal-relevant information because it relates to the capacity to ignore task-irrelevant changes in the environment.

Neural basis of distractor resistance during visual working memory maintenance

Visual working memory representations must be protected from the intervening irrelevant visual input. While it is well known that interference resistance is most challenging when distractors match the prioritised mnemonic information, its neural mechanisms remain poorly understood. Here, we identify two top-down attentional control processes that have opposing effects on distractor resistance. We reveal an early selection negativity in the EEG responses to matching as compared to non-matching distractors, the magnitude of which is negatively associated with behavioural distractor resistance. Additionally, matching distractors lead to reduced post-stimulus alpha power as well as increased fMRI responses in the object-selective visual cortical areas and the inferior frontal gyrus. However, the congruency effect found on the post-stimulus periodic alpha power and the inferior frontal gyrus fMRI responses show a positive association with distractor resistance. These findings suggest that distractor interference is enhanced by proactive memory content-guided selection processes and diminished by reactive allocation of top-down attentional resources to protect memorandum representations within visual cortical areas retaining the most selective mnemonic code.

The Alerting and Orienting Systems of Attention Are Modified by Cannabis Dependence

Attention allows us to select relevant information from the background. Although several studies have described that cannabis use induces deleterious effects on attention, it remains unclear if cannabis dependence affects the attention network systems differently.

OBJECTIVES

To evaluate whether customary consumption of cannabis or cannabis dependence impacts the alerting, orienting, and executive control systems in young adults; to find out whether it is related to tobacco or alcohol dependence and if cannabis use characteristics are associated with the attention network systems.

METHOD

One-hundred and fifty-four healthy adults and 102 cannabis users performed the Attention Network Test (ANT) to evaluate the alerting, orienting, and executive control systems.

RESULTS

Cannabis use enhanced the alerting system but decreased the orienting system. Moreover, those effects seem to be associated with cannabis dependence. Out of all the cannabis-using variables, only the age of onset of cannabis use significantly predicted the efficiency of the orienting and executive control systems.

CONCLUSION

Cannabis dependence favors tonic alertness but reduces selective attention ability; earlier use of cannabis worsens the efficiency of selective attention and resolution of conflicts.

Distraction in Visual Working Memory: Resistance is Not Futile

Over half a century of research focused on understanding how working memory is capacity constrained has overshadowed the fact that it is also remarkably resistant to interference. Protecting goal-relevant information from distraction is a cornerstone of cognitive function that involves a multifaceted collection of control processes and storage mechanisms. Here, we discuss recent advances in cognitive psychology and neuroscience that have produced new insights into the nature of visual working memory and its ability to resist distraction. We propose that distraction resistance should be an explicit component in any model of working memory and that understanding its behavioral and neural correlates is essential for building a comprehensive understanding of real-world memory function.

Neural Basis of Scale Errors in Young Children

In this study, we examined whether 2-and 3-year-old children exhibited activation in the dorsolateral and ventrolateral prefrontal regions while engaging in a tool-based scale error task as measured by near-infrared spectroscopy. Results revealed no significant differences in the prefrontal activation between children who produced scale errors and those who did not. However, we found significant activations of the prefrontal region during scale error sessions compared to free play sessions. Our results do not deny that the activation of prefrontal regions may, at least in part, be associated with children's scale error.

Distraction biases working memory for faces

Working memory persists in the face of distraction, yet not without consequence. Previous research has shown that memory for low-level visual features is systematically influenced by the maintenance or presentation of a similar distractor stimulus. Responses are frequently biased in stimulus space towards a perceptual distractor, though this has yet to be determined for high-level stimuli. We investigated whether these influences are shared for complex visual stimuli such as faces. To quantify response accuracies for these stimuli, we used a delayed-estimation task with a computer-generated "face space" consisting of 80 faces that varied continuously as a function of age and sex. In a set of three experiments, we found that responses for a target face held in working memory were biased towards a distractor face presented during the maintenance period. The amount of response bias did not vary as a function of distance between target and distractor. Our data suggest that, similar to low-level visual features, high-level face representations in working memory are biased by the processing of related but task-irrelevant information.

Dynamic adjustments in working memory in the face of affective interference

Cognitive control, which allows for the selection and monitoring of goal-relevant behavior, is dynamically upregulated on the basis of moment-to-moment cognitive demands. One route by which these demands are registered by cognitive control systems is via the detection of response conflict. Yet working memory (WM) demands may similarly signal dynamic adjustments in cognitive control. In a delayed-recognition WM task, Jha and Kiyonaga (Journal of Experimental Psychology: Learning, Memory, & Cognition, 36(4), 1036-1042, 2010) demonstrated dynamic adjustments in cognitive control via manipulations of mnemonic load and delay-spanning cognitive interference. In the present study, we aimed to extend prior work by investigating whether affective interference may similarly upregulate cognitive control. In Experiment 1, participants (N = 89) completed a delayed-recognition WM task in which mnemonic load (memory load of one vs. two items) and delay-spanning affective interference (neutral vs. negative distractors) were manipulated in a factorial design. Consistent with Jha and Kiyonaga, the present results revealed that mnemonic load led to dynamic adjustments in cognitive control, as reflected by greater performance on trials preceded by high than by low load. In addition, we observed that affective interference could trigger dynamic adjustments in cognitive control, as evinced by higher performance on trials preceded by negative than by neutral distractors. These findings were subsequently confirmed in Experiment 2, which was a pre-registered replication study (N = 100). Thus, these results suggest that in addition to dynamic adjustments as a function of mnemonic load, affective interference, similar to cognitive interference (Jha & Kiyonaga Journal of Experimental Psychology: Learning, Memory, & Cognition, 36(4), 1036-1042, 2010), may trigger dynamic adjustments in cognitive control during a WM task.

Does mindfulness training help working memory 'work' better?

There has been a proliferation of mindfulness training (MT) programs offered across a multitude of settings, including military, business, sports, education, and medicine. As such, ascertaining training effectiveness and determining best practices for program delivery are of the utmost importance. MT is often introduced to promote an array of desired effects from better mood, better leadership and management skills, to improved workplace or academic performance. Despite the diversity of factors motivating adoption of MTs, it can be argued from a cognitive training perspective that there should be uniformity in the core cognitive processes strengthened via repeated and systematic engagement in MT exercises. Herein, we explore the hypothesis that MT promotes salutary changes in the brain's working memory (WM) system. We review prior research and highlight aspects of MT programs that may be critical for achieving beneficial WM effects. Further, we suggest that given the centrality of WM in core processes such as emotion regulation, problem solving, and learning, MT programs capable of achieving WM benefits may be best positioned to promote other desired outcomes (e.g. reductions in negative mood). For these reasons, we recommend that more studies include WM metrics in their evaluation of MT programs.

Impaired Cognitive Flexibility After Neonatal Perirhinal Lesions in Rhesus Macaques

Previous research indicated that monkeys with neonatal perirhinal lesions (Neo-PRh) were impaired on working memory (WM) tasks that generated proactive interference, but performed normally on WM tasks devoid of interference (Weiss et al., 2016). This finding suggested that the early lesions disrupted cognitive processes important for resolving proactive interference, such as behavioral inhibition and cognitive flexibility. To distinguish between these possibilities, the same Neo-PRh monkeys and their controls were tested using the Intradimensional/Extradimensional attentional set-shifting task (Roberts et al., 1988; Dias et al., 1997). Neo-PRh monkeys completed the Simple and Compound Discrimination stages, the Intradimensional Shift stage, and all Reversal stages comparably to controls, but made significantly more errors on the Extradimensional Shift stage of the task. These data indicate that impaired cognitive flexibility was the likely source of increased perseverative errors made by Neo-PRh monkeys when performing WM tasks, rather than impaired behavioral inhibition, and imply that the perirhinal cortex and its interactions with the PFC may play a unique and critical role in the development of attentional set shifting abilities.

Ignoring versus updating in working memory reveal differential roles of attention and feature binding

Ignoring distracting information and updating current contents are essential components of working memory (WM). Yet, although both require controlling irrelevant information, it is unclear whether they have the same effects on recall and produce the same level of misbinding errors (incorrectly joining the features of different memoranda). Moreover, the likelihood of misbinding may be affected by the feature similarity between the items already encoded into memory and the information that has to be filtered out (ignored) or updated into memory. Here, we investigate these questions. Participants were sequentially presented with two pairs of arrows. The first pair of arrows always had to be encoded into memory, but the second pair either had to be ignored (ignore condition) or allowed to displace the previously encoded items (update condition). To investigate the effect of similarity on recall, we also varied, in a factorial manner, whether the items that had to be ignored or updated were presented in the same or different colours and/or same or different spatial locations to the original memoranda. By applying a computational model, we were able to quantify the levels of misbinding. Ignoring, but not updating, increased overall recall error as well as misbinding rates, even when accounting for the retention period. This indicates that not all manipulations of attention in WM are equal in terms of their effects on recall and misbinding. Misbinding rates in the ignore condition were affected by the colour and spatial congruence of relevant and irrelevant information to a greater extent than in the update condition. This finding suggests that attentional templates are used to evaluate relevant and irrelevant information in different ways during ignoring and updating. Together, the results suggest that differences between the two functions might occur due to higher levels of attentional compartmentalisation - or protection - during updating compared to ignoring.

Distress tolerance among substance users is associated with functional connectivity between prefrontal regions during a distress tolerance task

Distress tolerance (DT), defined as the ability to persist in goal directed behavior while experiencing affective distress, is implicated in the development and maintenance of substance use disorders. While theory and evidence indicate that cortico-limbic neural dysfunction may account for deficits in goal directed behavior while experiencing distress, the neurobiological mechanisms of DT have yet to be examined. We modified a computerized DT task for use in functional magnetic resonance imaging (fMRI), the Paced Auditory Serial Addition Task (PASAT-M), and examined the neural correlates and functional connectivity of DT among a cohort of substance users (n = 21; regular cocaine and nicotine users) and healthy controls (n = 25). In response to distress during the PASAT-M, we found greater activation in a priori cortico-limbic network ROIs, namely the right insula, anterior cingulate cortex (ACC), bilateral medial frontal gyrus (MFG), right inferior frontal gyrus (IFG) and right ventromedial prefrontal cortex (vmPFC) significantly predicted higher DT among substance users, but not healthy controls. In addition, greater task-specific functional connectivity during distress between the right MFG and bilateral vmPFC/sgACC was associated with higher DT among substance users, but not healthy controls. The observed positive relationship between DT and neural activation in cortico-limbic structures, as well as functional connectivity between the rMFG and vmPFC/sgACC, is in line with theory and research suggesting the importance of these structures for persisting in goal directed behavior while experiencing affective distress.

Neural Representation of Working Memory Content Is Modulated by Visual Attentional Demand

Recent theories assert that visual working memory (WM) relies on the same attentional resources and sensory substrates as visual attention to external stimuli. Behavioral studies have observed competitive tradeoffs between internal (i.e., WM) and external (i.e., visual) attentional demands, and neuroimaging studies have revealed representations of WM content as distributed patterns of activity within the same cortical regions engaged by perception of that content. Although a key function of WM is to protect memoranda from competing input, it remains unknown how neural representations of WM content are impacted by incoming sensory stimuli and concurrent attentional demands. Here, we investigated how neural evidence for WM information is affected when attention is occupied by visual search-at varying levels of difficulty-during the delay interval of a WM match-to-sample task. Behavioral and fMRI analyses suggested that WM maintenance was impacted by the difficulty of a concurrent visual task. Critically, multivariate classification analyses of category-specific ventral visual areas revealed a reduction in decodable WM-related information when attention was diverted to a visual search task, especially when the search was more difficult. This study suggests that the amount of available attention during WM maintenance influences the detection of sensory WM representations.

Tracking the effect of emotional distraction in working memory brain networks: Evidence from an MEG study

The active maintenance of information in visual working memory (WM) is known to rely on the sustained activity over functional networks including frontal, parietal, occipital, and temporal cortices. Previous studies have described interference-based disturbances in the functional coupling between prefrontal and posterior cortices, and that such disturbances can be restored for a successful WM performance after the presentation of the interfering stimulus. However, very few studies have applied functional connectivity measures to the analysis of the brain dynamics involved in overriding emotional distraction, and all of them have limited their analysis to the particular connections between the amygdala and prefrontal cortex. In this study, we used magnetoencephalography (MEG) to characterize the mutual information-based functional connectivity dynamics among regions of interest located over the prefrontal, the parietal, the temporal, and the occipital cortex. Our results show that the detection of emotional distraction at early latencies (50-150 ms) induces a reduction of functional connectivity involving parietal and temporal cortices that are part of the frontoposterior WM network, while functional coupling among prefrontal areas and between them and posterior cortices is strengthened during the detection of emotional distractors. Later in the processing of the distractor (250-350 and 360-460 ms), the frontoposterior coupling is reestablished for a successful performance, while the orbitofrontal and ventrolateral prefrontal cortex become strongly connected to posterior cortices as a mechanism to cope with emotional distractors.

Distractor-resistant Short-Term Memory Is Supported by Transient Changes in Neural Stimulus Representations

Goal-directed behavior in a complex world requires the maintenance of goal-relevant information despite multiple sources of distraction. However, the brain mechanisms underlying distractor-resistant working or short-term memory (STM) are not fully understood. Although early single-unit recordings in monkeys and fMRI studies in humans pointed to an involvement of lateral prefrontal cortices, more recent studies highlighted the importance of posterior cortices for the active maintenance of visual information also in the presence of distraction. Here, we used a delayed match-to-sample task and multivariate searchlight analyses of fMRI data to investigate STM maintenance across three extended delay phases. Participants maintained two samples (either faces or houses) across an unfilled pre-distractor delay, a distractor-filled delay, and an unfilled post-distractor delay. STM contents (faces vs. houses) could be decoded above-chance in all three delay phases from occipital, temporal, and posterior parietal areas. Classifiers trained to distinguish face versus house maintenance successfully generalized from pre- to post-distractor delays and vice versa, but not to the distractor delay period. Furthermore, classifier performance in all delay phases was correlated with behavioral performance in house, but not face, trials. Our results demonstrate the involvement of distributed posterior, but not lateral prefrontal, cortices in active maintenance during and after distraction. They also show that the neural code underlying STM maintenance is transiently changed in the presence of distractors and reinstated after distraction. The correlation with behavior suggests that active STM maintenance is particularly relevant in house trials, whereas face trials might rely more strongly on contributions from long-term memory.

Proactive, but Not Reactive, Distractor Filtering Relies on Local Modulation of Alpha Oscillatory Activity

Filter mechanisms that prevent irrelevant information from consuming the limited storage capacity of visual STM are critical for goal-directed behavior. Alpha oscillatory activity has been related to proactive filtering of anticipated distraction. Yet, distraction in everyday life is not always anticipated, necessitating rapid, reactive filtering mechanisms. Currently, the oscillatory mechanisms underlying reactive distractor filtering remain unclear. In the current EEG study, we investigated whether reactive filtering of distractors also relies on alpha-band oscillatory mechanisms and explored possible contributions by oscillations in other frequency bands. To this end, participants performed a lateralized change detection task in which a varying and unpredicted number of distractors were presented both in the relevant hemifield, among targets, and in the irrelevant hemifield. Results showed that, whereas proactive distractor filtering was accompanied by lateralization of alpha-band activity over posterior scalp regions, reactive distractor filtering was not associated with modulations of oscillatory power in any frequency band. Yet, behavioral and post hoc ERP analyses clearly showed that participants selectively encoded relevant information. On the basis of these results, we conclude that reactive distractor filtering may not be realized through local modulation of alpha-band oscillatory activity.

The Representational Basis of Working Memory

Working memory refers to a system involved in the online maintenance and manipulation of information in the absence of external input. Due to the importance of working memory in higher-level cognition, a wealth of neuroscience studies has investigated its neural basis. These studies have often led to conflicting viewpoints regarding the importance of the prefrontal cortex (PFC) and posterior sensory cortices. Here, we review evidence for each position. We suggest that the relative contributions of the PFC and sensory cortices to working memory can be understood with respect to processing demands. We argue that procedures that minimize processing demands lead to increased importance of sensory representations, while procedures that permit transformational processing lead to representational abstraction that relies on the PFC. We suggest that abstract PFC representations support top-down control over posterior representations while also providing bottom-up inputs into higher-level cognitive processing. Although a number of contemporary studies have studied working memory while using procedures that minimize the role of the PFC, we argue that consideration of the PFC is critical for our understanding of working memory and higher-level cognition more generally.

Brain Activation Patterns Associated with the Effects of Emotional Distracters during Working Memory Maintenance in Patients with Generalized Anxiety Disorder

Few studies have assessed the neural mechanisms of the effects of emotion on cognition in generalized anxiety disorder (GAD) patients. In this functional MRI (fMRI), we investigated the effects of emotional interference on working memory (WM) maintenance in GAD patients. Fifteen patients with GAD participated in this study. Event-related fMRI data were obtained while the participants performed a WM task (face recognition) with neutral and anxiety-provoking distracters. The GAD patients showed impaired performance in WM task during emotional distracters and showed greater activation on brain regions such as DLPFC, VLPFC, amygdala, hippocampus which are responsible for the active maintenance of goal relevant information in WM and emotional processing. Although our results are not conclusive, our finding cautiously suggests the cognitive-affective interaction in GAD patients which shown interfering effect of emotional distracters on WM maintenance.

Low cognitive load strengthens distractor interference while high load attenuates when cognitive load and distractor possess similar visual characteristics

Studies on visual cognitive load have reported inconsistent effects of distractor interference when distractors have visual characteristic that are similar to the cognitive load. Some studies have shown that the cognitive load enhances distractor interference, while others reported an attenuating effect. We attribute these inconsistencies to the amount of cognitive load that a person is required to maintain. Lower amounts of cognitive load increase distractor interference by orienting attention toward visually similar distractors. Higher amounts of cognitive load attenuate distractor interference by depleting attentional resources needed to process distractors. In the present study, cognitive load consisted of faces (Experiments 1-3) or scenes (Experiment 2). Participants performed a selective attention task in which they ignored face distractors while judging a color of a target dot presented nearby, under differing amounts of load. Across these experiments distractor interference was greater in the low-load condition and smaller in the high-load condition when the content of the cognitive load had similar visual characteristic to the distractors. We also found that when a series of judgments needed to be made, the effect was apparent for the first trial but not for the second. We further tested an involvement of working memory capacity (WMC) in the load effect (Experiment 3). Interestingly, both high and low WMC groups received an equivalent effect of the cognitive load in the first distractor, suggesting these effects are fairly automatic.

Visual short-term memory load modulates the early attention and perception of task-irrelevant emotional faces

The ability to focus on task-relevant information, while suppressing distraction, is critical for human cognition and behavior. Using a delayed-match-to-sample (DMS) task, we investigated the effects of emotional face distractors (positive, negative, and neutral faces) on early and late phases of visual short-term memory (VSTM) maintenance intervals, using low and high VSTM loads. Behavioral results showed decreased accuracy and delayed reaction times (RTs) for high vs. low VSTM load. Event-related potentials (ERPs) showed enhanced frontal N1 and occipital P1 amplitudes for negative faces vs. neutral or positive faces, implying rapid attentional alerting effects and early perceptual processing of negative distractors. However, high VSTM load appeared to inhibit face processing in general, showing decreased N1 amplitudes and delayed P1 latencies. An inverse correlation between the N1 activation difference (high-load minus low-load) and RT costs (high-load minus low-load) was found at left frontal areas when viewing negative distractors, suggesting that the greater the inhibition the lower the RT cost for negative faces. Emotional interference effect was not found in the late VSTM-related parietal P300, frontal positive slow wave (PSW) and occipital negative slow wave (NSW) components. In general, our findings suggest that the VSTM load modulates the early attention and perception of emotional distractors.

Stochastic Dynamics Underlying Cognitive Stability and Flexibility

Cognitive stability and flexibility are core functions in the successful pursuit of behavioral goals. While there is evidence for a common frontoparietal network underlying both functions and for a key role of dopamine in the modulation of flexible versus stable behavior, the exact neurocomputational mechanisms underlying those executive functions and their adaptation to environmental demands are still unclear. In this work we study the neurocomputational mechanisms underlying cue based task switching (flexibility) and distractor inhibition (stability) in a paradigm specifically designed to probe both functions. We develop a physiologically plausible, explicit model of neural networks that maintain the currently active task rule in working memory and implement the decision process. We simplify the four-choice decision network to a nonlinear drift-diffusion process that we canonically derive from a generic winner-take-all network model. By fitting our model to the behavioral data of individual subjects, we can reproduce their full behavior in terms of decisions and reaction time distributions in baseline as well as distractor inhibition and switch conditions. Furthermore, we predict the individual hemodynamic response timecourse of the rule-representing network and localize it to a frontoparietal network including the inferior frontal junction area and the intraparietal sulcus, using functional magnetic resonance imaging. This refines the understanding of task-switch-related frontoparietal brain activity as reflecting attractor-like working memory representations of task rules. Finally, we estimate the subject-specific stability of the rule-representing attractor states in terms of the minimal action associated with a transition between different rule states in the phase-space of the fitted models. This stability measure correlates with switching-specific thalamocorticostriatal activation, i.e., with a system associated with flexible working memory updating and dopaminergic modulation of cognitive flexibility. These results show that stochastic dynamical systems can implement the basic computations underlying cognitive stability and flexibility and explain neurobiological bases of individual differences.

In this work we develop a neurophysiologically inspired dynamical model that is capable of solving a complex behavioral task testing cognitive stability and flexibility. We can individually fit the behavior of each of 20 human subjects that conducted this stability-flexibility task during functional magnetic resonance imaging (fMRI). The physiological nature of our model allows us to estimate the energy consumption of the rule-representing module, which we use to predict the hemodynamic fMRI response. Through this model-based prediction, we localize the rule module to a frontoparietal network known to be required for cognitive stability and flexibility. In this way we both validate our model, which is based on noisy attractor dynamics, and specify the computational role of a cortical network that is well-established in human neuroimaging research. Additionally, we quantify the individual stability of the rule-representing states and relate this stability to individual differences in energy consumption during task switching versus distractor inhibition. Hereby we show that the activation of a thalamocorticostriatal network involved in the dopaminergic modulation of cognitive stability is modulated by the model-derived stability of the frontoparietal rule-representing network. Altogether, we show that noisy dynamic systems are likely to implement the basic computations underlying cognitive stability and flexibility.

Early detection and late cognitive control of emotional distraction by the prefrontal cortex

Unpleasant emotional distraction can impair the retention of non-emotional information in working memory (WM). Research links the prefrontal cortex with the successful control of such biologically relevant distractors, although the temporal changes in this brain mechanism remain unexplored. We use magnetoencephalography to investigate the temporal dynamics of the cognitive control of both unpleasant and pleasant distraction, in the millisecond (ms) scale. Behavioral results demonstrate that pleasant events do not affect WM maintenance more than neutral ones. Neuroimaging results show that prefrontal cortices are recruited for the rapid detection of emotional distraction, at early latencies of the processing (70-130 ms). Later in the processing (360-450 ms), the dorsolateral, the medial and the orbital sections of the prefrontal cortex mediate the effective control of emotional distraction. In accordance with the behavioral performance, pleasant distractors do not require higher prefrontal activity than neutral ones. These findings extend our knowledge about the brain mechanisms of coping with emotional distraction in WM. In particular, they show for the first time that overriding the attentional capture triggered by emotional distractors, while maintaining task-relevant elements in mind, is based on the early detection of such linked-to-survival information and on its later cognitive control by the prefrontal cortex.

Dopaminergic modulation of distracter-resistance and prefrontal delay period signal

Dopamine has long been implicated in the online maintenance of information across short delays. Specifically, dopamine has been proposed to modulate the strength of working memory representations in the face of intervening distracters. This hypothesis has not been tested in humans. We fill this gap using pharmacological neuroimaging. Healthy young subjects were scanned after intake of the dopamine receptor agonist bromocriptine or placebo (in a within-subject, counterbalanced, and double-blind design). During scanning, subjects performed a delayed match-to-sample task with face stimuli. A face or scene distracter was presented during the delay period (between the cue and the probe). Bromocriptine altered distracter-resistance, such that it impaired performance after face relative to scene distraction. Individual differences in the drug effect on distracter-resistance correlated negatively with drug effects on delay period signal in the prefrontal cortex, as well as on functional connectivity between the prefrontal cortex and the fusiform face area. These results provide evidence for the hypothesis that dopaminergic modulation of the prefrontal cortex alters resistance of working memory representations to distraction. Moreover, we show that the effects of dopamine on the distracter-resistance of these representations are accompanied by modulation of the functional strength of connections between the prefrontal cortex and stimulus-specific posterior cortex.

Evidence for working memory storage operations in perceptual cortex

Isolating the short-term storage component of working memory (WM) from the myriad of associated executive processes has been an enduring challenge. Recent efforts have identified patterns of activity in visual regions that contain information about items being held in WM. However, it remains unclear (1) whether these representations withstand intervening sensory input and (2) how communication between multimodal association cortex and the unimodal perceptual regions supporting WM representations is involved in WM storage. We present evidence that the features of a face held in WM are stored within face-processing regions, that these representations persist across subsequent sensory input, and that information about the match between sensory input and a memory representation is relayed forward from perceptual to prefrontal regions. Participants were presented with a series of probe faces and indicated whether each probe matched a target face held in WM. We parametrically varied the feature similarity between the probe and target faces. Activity within face-processing regions scaled linearly with the degree of feature similarity between the probe face and the features of the target face, suggesting that the features of the target face were stored in these regions. Furthermore, directed connectivity measures revealed that the direction of information flow that was optimal for performance was from sensory regions that stored the features of the target face to dorsal prefrontal regions, supporting the notion that sensory input is compared to representations stored within perceptual regions and is subsequently relayed forward. Together, these findings indicate that WM storage operations are carried out within perceptual cortex.

Impaired response inhibition in the rat 5 choice continuous performance task during protracted abstinence from chronic alcohol consumption

Impaired cognitive processing is a hallmark of addiction. In particular, deficits in inhibitory control can propel continued drug use despite adverse consequences. Clinical evidence shows that detoxified alcoholics exhibit poor inhibitory control in the Continuous Performance Task (CPT) and related tests of motor impulsivity. Animal models may provide important insight into the neural mechanisms underlying this consequence of chronic alcohol exposure though pre-clinical investigations of behavioral inhibition during alcohol abstinence are sparse. The present study employed the rat 5 Choice-Continuous Performance Task (5C-CPT), a novel pre-clinical variant of the CPT, to evaluate attentional capacity and impulse control over the course of protracted abstinence from chronic intermittent alcohol consumption. In tests conducted with familiar 5C-CPT conditions EtOH-exposed rats exhibited impaired attentional capacity during the first hours of abstinence and impaired behavioral restraint (increased false alarms) during the first 5d of abstinence that dissipated thereafter. Subsequent tests employing visual distractors that increase the cognitive load of the task revealed significant increases in impulsive action (premature responses) at 3 and 5 weeks of abstinence, and the emergence of impaired behavioral restraint (increased false alarms) at 7 weeks of abstinence. Collectively, these findings demonstrate the emergence of increased impulsive action in alcohol-dependent rats during protracted alcohol abstinence and suggest the 5C-CPT with visual distractors may provide a viable behavioral platform for characterizing the neurobiological substrates underlying impaired behavioral inhibition resulting from chronic intermittent alcohol exposure.

The neural bases of distracter-resistant working memory

A major difference between humans and other animals is our capacity to maintain information in working memory (WM) while performing secondary tasks, which enables sustained, complex cognition. A common assumption is that the lateral prefrontal cortex (PFC) is critical for WM performance in the presence of distracters, but direct evidence is scarce. We assessed the relationship between fMRI activity and WM performance within subjects, with performance matched across distracter and no-distracter conditions. Activity in the ventrolateral PFC during WM encoding and maintenance positively predicted performance in both conditions, whereas activity in the presupplementary motor area (pre-SMA) predicted performance only under distraction. Other parts of the dorsolateral and ventrolateral PFCs predicted performance only in the no-distracter condition. These findings challenge a lateral-PFC-centered view of distracter resistance, and suggest that the lateral PFC supports a type of WM representation that is efficient for dealing with task-irrelevant input but is, nonetheless, easily disrupted by dual-task demands.

Distributed and dynamic storage of working memory stimulus information in extrastriate cortex

The predominant neurobiological model of working memory (WM) posits that stimulus information is stored via stable, elevated activity within highly selective neurons. On the basis of this model, which we refer to as the canonical model, the storage of stimulus information is largely associated with lateral PFC (lPFC). A growing number of studies describe results that cannot be fully explained by the canonical model, suggesting that it is in need of revision. In this study, we directly tested key elements of the canonical model. We analyzed fMRI data collected as participants performed a task requiring WM for faces and scenes. Multivariate decoding procedures identified patterns of activity containing information about the items maintained in WM (faces, scenes, or both). Although information about WM items was identified in extrastriate visual cortex (EC) and lPFC, only EC exhibited a pattern of results consistent with a sensory representation. Information in both regions persisted even in the absence of elevated activity, suggesting that elevated population activity may not represent the storage of information in WM. Additionally, we observed that WM information was distributed across EC neural populations that exhibited a broad range of selectivity for the WM items rather than restricted to highly selective EC populations. Finally, we determined that activity patterns coding for WM information were not stable, but instead varied over the course of a trial, indicating that the neural code for WM information is dynamic rather than static. Together, these findings challenge the canonical model of WM.

The impact of task relevance and degree of distraction on stimulus processing

Background

The impact of task relevance on event-related potential amplitudes of early visual processing was previously demonstrated. Study designs, however, differ greatly, not allowing simultaneous investigation of how both degree of distraction and task relevance influence processing variations. In our study, we combined different features of previous tasks. We used a modified 1-back task in which task relevant and task irrelevant stimuli were alternately presented. The task irrelevant stimuli could be from the same or from a different category as the task relevant stimuli, thereby producing high and low distracting task irrelevant stimuli. In addition, the paradigm comprised a passive viewing condition. Thus, our paradigm enabled us to compare the processing of task relevant stimuli, task irrelevant stimuli with differing degrees of distraction, and passively viewed stimuli. EEG data from twenty participants was collected and mean P100 and N170 amplitudes were analyzed. Furthermore, a potential connection of stimulus processing and symptoms of attention deficit hyperactivity disorder (ADHD) was investigated.

Results

Our results show a modulation of peak N170 amplitudes by task relevance. N170 amplitudes to task relevant stimuli were significantly higher than to high distracting task irrelevant or passively viewed stimuli. In addition, amplitudes to low distracting task irrelevant stimuli were significantly higher than to high distracting stimuli. N170 amplitudes to passively viewed stimuli were not significantly different from either kind of task irrelevant stimuli. Participants with more symptoms of hyperactivity and impulsivity showed decreased N170 amplitudes across all task conditions. On a behavioral level, lower N170 enhancement efficiency was significantly correlated with false alarm responses.

Conclusions

Our results point to a processing enhancement of task relevant stimuli. Unlike P100 amplitudes, N170 amplitudes were strongly influenced by enhancement and enhancement efficiency seemed to have direct behavioral consequences. These findings have potential implications for models of clinical disorders affecting selective attention, especially ADHD.

Negative emotional distraction on neural circuits for working memory in patients with posttraumatic stress disorder

OBJECTIVE

To study the neural mechanism for the impact of negative emotional distraction on working memory in patients with posttraumatic stress disorder (PTSD) resulting from exposure to motor vehicle accidents.

METHODS

Twenty PTSD patients and 20 healthy subjects were recruited. Event-related functional magnetic resonance imaging (fMRI) was used to investigate the effects of negative and neutral distractors on a delayed-response working memory task. All experiments were performed on a 3.0T MRI scanner, and the functional imaging data were analyzed using SPM8 software.

RESULTS

The PTSD group showed poorer performance than the control group when the negative distractors were presented during the delay phase of working memory. The functional imaging indicated that, in the presence of negative relative to neutral distractors, the PTSD group showed higher activation in the emotion processing regions, including amygdala, precuneus and fusiform gyrus, but lower activation in the inferior frontal cortex, insula and left supramarginal gyrus than the control group.

CONCLUSION

Based on the results that activation in the PTSD patients in the presence of negative distractors increased in the emotion-related brain regions but decreased in the working memory-related brain regions, we may conclude that the neural basis of working memory is impaired by negative emotion in PTSD patients.

Trait anxiety and the neural efficiency of manipulation in working memory

The present study investigates the effects of trait anxiety on the neural efficiency of working memory component functions (manipulation vs. maintenance) in the absence of threat-related stimuli. For the manipulation of affectively neutral verbal information held in working memory, high- and low-anxious individuals (N = 46) did not differ in their behavioral performance, yet trait anxiety was positively related to the neural effort expended on task processing, as measured by BOLD signal changes in fMRI. Higher levels of anxiety were associated with stronger activation in two regions implicated in the goal-directed control of attention—that is, right dorsolateral prefrontal cortex (DLPFC) and left inferior frontal sulcus—and with stronger deactivation in a region assigned to the brain’s default-mode network—that is, rostral–ventral anterior cingulate cortex. Furthermore, anxiety was associated with a stronger functional coupling of right DLPFC with ventrolateral prefrontal cortex. We interpret our findings as reflecting reduced processing efficiency in high-anxious individuals and point out the need to consider measures of functional integration in addition to measures of regional activation strength when investigating individual differences in neural efficiency. With respect to the functions of working memory, we conclude that anxiety specifically impairs the processing efficiency of (control-demanding) manipulation processes (as opposed to mere maintenance). Notably, this study contributes to an accumulating body of evidence showing that anxiety also affects cognitive processing in the absence of threat-related stimuli.

Correspondence between stimulus encoding- and maintenance-related neural processes underlies successful working memory

The ability to actively maintain information in working memory (WM) is vital for goal-directed behavior, but the mechanisms underlying this process remain elusive. We hypothesized that successful WM relies upon a correspondence between the neural processes associated with stimulus encoding and the neural processes associated with maintenance. Using functional magnetic resonance imaging, we identified regional activity and inter-regional connectivity during stimulus encoding and the maintenance of those stimuli when they were no longer present. We compared correspondence in these neural processes across encoding and maintenance epochs with WM performance. Critically, greater correspondence between encoding and maintenance in 1) regional activity in the lateral prefrontal cortex (PFC) and 2) connectivity between lateral PFC and extrastriate cortex was associated with increased performance. These findings suggest that the conservation of neural processes across encoding and maintenance supports the integrity of representations in WM.

Prefrontal cortical mechanisms underlying individual differences in cognitive flexibility and stability

The pFC is critical for cognitive flexibility (i.e., our ability to flexibly adjust behavior to changing environmental demands), but also for cognitive stability (i.e., our ability to follow behavioral plans in the face of distraction). Behavioral research suggests that individuals differ in their cognitive flexibility and stability, and neurocomputational theories of working memory relate this variability to the concept of attractor stability in recurrently connected neural networks. We introduce a novel task paradigm to simultaneously assess flexible switching between task rules (cognitive flexibility) and task performance in the presence of irrelevant distractors (cognitive stability) and to furthermore assess the individual "spontaneous switching rate" in response to ambiguous stimuli to quantify the individual dispositional cognitive flexibility in a theoretically motivated way (i.e., as a proxy for attractor stability). Using fMRI in healthy human participants, a common network consisting of parietal and frontal areas was found for task switching and distractor inhibition. More flexible persons showed reduced activation and reduced functional coupling in frontal areas, including the inferior frontal junction, during task switching. Most importantly, the individual spontaneous switching rate antagonistically affected the functional coupling between inferior frontal junction and the superior frontal gyrus during task switching and distractor inhibition, respectively, indicating that individual differences in cognitive flexibility and stability are indeed related to a common prefrontal neural mechanism. We suggest that the concept of attractor stability of prefrontal working memory networks is a meaningful model for individual differences in cognitive stability versus flexibility.

Goal-directed behavior under emotional distraction is preserved by enhanced task-specific activation

Despite the distracting effects of emotional stimuli on concurrent task performance, humans are able to uphold goal-directed behavior. Here, we investigated the hypothesis that this effect is due to the enhanced recruitment of task-specific neural resources. In a two-step functional magnetic resonance imaging study, we first localized those areas involved in mental arithmetics by contrasting arithmetic problems with a number detection task. The resulting activation maps were then used as masks in a second experiment that compared the effects of neutral and emotional distracter images on mental arithmetics. We found increased response times in the emotional distracter condition, accompanied by enhanced activation in task-specific areas, including superior parietal cortex, dorsolateral and dorsomedial prefrontal cortex. This activation increase correlated with larger behavioral impairment through emotional distraction. Similar error rates in both conditions indicate that cognitive task performance is preserved through enhanced recruitment of task-specific neural resources when emotional distracter stimuli are present.

Measurement of constructs using self-report and behavioral lab tasks: is there overlap in nomothetic span and construct representation for impulsivity?

There has been little empirical evidence examining the overlap in nomothetic span for self-report measures and construct representation for behavioral lab tasks in most psychological constructs. Using the personality trait of impulsivity as an example, the authors completed a meta-analysis of 27 published research studies examining the relationship between these methods. In general, although there is a statistically significant relationship between multidimensional self-report and lab task impulsivity (r = 0.097), practically, the relationship is small. Examining relationships among unidimensional impulsivity self-report and lab task conceptualizations indicated very little overlap in self-report and behavioral lab task constructs. Significant relationships were found between lack of perseverance and prepotent response inhibition (r = 0.099); between lack of planning and prepotent response inhibition (r = 0.106), delay response (r = 0.134), and distortions in elapsed time (r = 0.104); between negative urgency and prepotent response inhibition (r = 0.106); and between sensation seeking and delay response (r = 0.131). Researchers should take care to specify which particular unidimensional constructs are operationalized with not only impulsivity, but with all traits. If self-report and lab task conceptualizations measure disparate aspects of impulsivity, we, as a field, should not expect large conceptual overlap between these methods.

Methylphenidate does not improve interference control during a working memory task in young patients with attention-deficit hyperactivity disorder

Patients with attention-deficit/hyperactivity disorder (ADHD) show deficits in working memory (WM) which may be related to prefrontal dysfunction. Methylphenidate (MPH) can restore WM deficits in ADHD by enhancing prefrontal activity. At the same time, changes in striatal activation could cause ADHD patients to be more interference-sensitive during working memory tasks. However, it is unclear whether MPH reduces WM distractibility in ADHD. In this fMRI study, 12 ADHD patients and 12 healthy controls participated on two separate days in a delayed-match-to-sample test. During the delay interval, a distractor stimulus was presented in half of the trials. Children and adolescents with ADHD received MPH only on one of the two sessions. Behavioral data analyses revealed that MPH normalized WM in ADHD. However, MPH did not improve WM performance when a distractor was presented during the delay interval. Functional images showed that MPH enhanced prefrontal activity during the delay in ADHD patients when no distractor was present. If the delay was interrupted by a distractor, only healthy controls showed activation of the caudate. In patients with ADHD, however, in line with behavioral data, MPH did not enhance caudate activity. In healthy youth, caudate activity is involved in interference control allowing the successful maintenance of information in working memory even in the presence of distraction. Our findings suggest that interference control, linked to caudate activity, is not adequately enhanced by MPH in ADHD.

Dual tasking and working memory in alcoholism: relation to frontocerebellar circuitry

Controversy exists regarding the role of cerebellar systems in cognition and whether working memory compromise commonly marking alcoholism can be explained by compromise of nodes of corticocerebellar circuitry. We tested 17 alcoholics and 31 age-matched controls with dual-task, working memory paradigms. Interference tasks competed with verbal and spatial working memory tasks using low (three item) or high (six item) memory loads. Participants also underwent structural MRI to obtain volumes of nodes of the frontocerebellar system. On the verbal working memory task, both groups performed equally. On the spatial working memory with the high-load task, the alcoholic group was disproportionately more affected by the arithmetic distractor than were controls. In alcoholics, volumes of the left thalamus and left cerebellar Crus I volumes were more robust predictors of performance in the spatial working memory task with the arithmetic distractor than the left frontal superior cortex. In controls, volumes of the right middle frontal gyrus and right cerebellar Crus I were independent predictors over the left cerebellar Crus I, left thalamus, right superior parietal cortex, or left middle frontal gyrus of spatial working memory performance with tracking interference. The brain-behavior correlations suggest that alcoholics and controls relied on the integrity of certain nodes of corticocerebellar systems to perform these verbal and spatial working memory tasks, but that the specific pattern of relationships differed by group. The resulting brain structure-function patterns provide correlational support that components of this corticocerebellar system not typically related to normal performance in dual-task conditions may be available to augment otherwise dampened performance by alcoholics.

Age differences in prefontal recruitment during verbal working memory maintenance depend on memory load

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies have revealed age-related under-activation, where older adults show less regional brain activation compared to younger adults, as well as age-related over-activation, where older adults show greater activation compared to younger adults. These differences have been found across multiple task domains, including verbal working memory (WM). Curiously, both under-activation and over-activation of dorsolateral prefrontal cortex (DLPFC) have been found for older adults in verbal WM tasks. Here, we use event-related fMRI to test the hypothesis that age-related differences in activation depend on memory load (the number of items that must be maintained). Our predictions about the recruitment of prefrontal executive processes are based on the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH; Reuter-Lorenz and Cappell, 2008). According to this hypothesis, more neural resources are engaged by older brains to accomplish computational goals completed with fewer resources by younger brains. Therefore, seniors are more likely than young adults to show over-activations at lower memory loads, and under-activations at higher memory loads. Consistent with these predictions, in right DLPFC, we observed age-related over-activation with lower memory loads despite equivalent performance accuracy across age groups. In contrast, with the highest memory load, older adults were significantly less accurate and showed less DLPFC activation compared to their younger counterparts. These results are considered in relation to previous reports of activation-performance relations using similar tasks, and are found to support the viability of CRUNCH as an account of age-related compensation and its potential costs.

Emotional priming effects during Stroop task performance

The ability to make decisions within an emotional context requires a balance between two functionally integrated neural systems that primarily support executive control and affective processing. Several studies have demonstrated effects of emotional interference presented during an ongoing cognitive task, but it is unclear how activating the emotional circuitry prior to a cognitive task may enhance or disrupt the executive system. In this study we used fMRI to examine the effects of emotional priming on executive processing during a number Stroop task. Our results indicated that during trials with less executive requirements, there was a greater aversive emotional attenuation effect in a network of regions including the ventrolateral prefrontal cortex (vlPFC), insula and cingulate gyrus. This attenuation effect was counteracted during trials with increased executive demand, suggesting that while pre-activation of the emotional system may lead to an automatic attenuation of activity in multiple regions, requirements for executive function may override the aversive emotional attenuation effect. Furthermore, this override effect was found to be associated with faster reaction times during executive processing. These findings demonstrate that activity in the vlPFC, cingulate and insula is dynamically adjusted in order to optimize performance, and illustrate the importance of the timing of each system's engagement in determining how competing cognitive and emotional information is processed.

Mechanisms of working memory disruption by external interference

The negative impact of external interference on working memory (WM) performance is well documented; yet, the mechanisms underlying this disruption are not sufficiently understood. In this study, electroencephalogram and functional magnetic resonance imaging (fMRI) data were recorded in separate experiments that each introduced different types of visual interference during a period of WM maintenance: distraction (irrelevant stimuli) and interruption (stimuli that required attention). The data converged to reveal that regardless of the type of interference, the magnitude of processing interfering stimuli in the visual cortex (as rapidly as 100 ms) predicted subsequent WM recognition accuracy for stored items. fMRI connectivity analyses suggested that in the presence of distraction, encoded items were maintained throughout the delay period via connectivity between the middle frontal gyrus and visual association cortex, whereas memoranda were not maintained when subjects were interrupted but rather reactivated in the postinterruption period. These results elucidate the mechanisms of external interference on WM performance and highlight similarities and differences of distraction and multitasking.