Examining a supramodal network for conflict processing: a systematic review and novel functional magnetic resonance imaging data for related visual and auditory stroop tasks

Prospective, randomized, controlled trial of parathyroidectomy versus observation in patients with "asymptomatic" primary hyperparathyroidism

BACKGROUND

Disruptions in cognitive function have been described in the constellation of symptoms associated with "asymptomatic" primary hyperparathyroidism (PHPT). The aim of this study was to determine the impact of parathyroidectomy (PTX) on brain function and sleep in "asymptomatic" PHPT patients.

METHODS

We conducted a prospective, randomized trial comparing immediate PTX with observation in patients with asymptomatic PHPT. We performed functional magnetic resonance imaging (fMRI) of the brain, sleep assessment, and validated neuropsychological battery at baseline, 6 weeks, and 6 months. Wilcoxon rank-sum and Pearson and Spearman correlations were used.

RESULTS

A total of 18 patients were randomized. Subjective sleepiness correlated with worse performance on executive function tests during fMRI at 6 weeks (Pearson, -0.473; P = .047) and 6 months (Pearson, -0.673; P = .002). Total sleep time correlated with PTH levels at both 6 weeks (Pearson, 0.518; P = .048) and 6 months (Pearson, 0.567; P = .018). At 6 weeks, hypersomnolence as measured subjectively was decreased in the PTX group, but increased in those observed (-2.56 vs 2.22; P = .03)

CONCLUSION

This prospective, randomized trial for asymptomatic PHPT patients demonstrated an association of sleep with brain function. Sleep seemed to be an indicator of brain activation in the anterior cingulate gyrus and precentral cortex. Subjective sleepiness was associated with executive function. The results of this pilot study suggest that decreased serum PTH levels correlate with improved sleep and that PTX decreases sleepiness in patients with asymptomatic PHPT.

Is moderate substance use associated with altered executive functioning in a population-based sample of young adults?

BACKGROUND

Substance use (SU) has been linked with impaired cognitive functioning. Evidence comes mainly from clinical studies or studies examining heavy users. Though, the majority of users are not involved in heavy use. This study investigates the association between moderate use and cognition in a population-based sample.

METHODS

A total of 284 young adults with ecstasy, cannabis or alcohol use and a control group were sampled from the EDSP database for participation in the Munich Assessment of Young Adults (MAYA) study. Subjects completed a comprehensive battery of neuropsychological tests (executive functions, working memory and impulsivity). Multiple linear regression models were conducted to examine the relationship between use and cognitive performance.

RESULTS

Increased ecstasy consumption was associated with increased error-proneness (Stroop task, CANTAB ID/ED-shift, spatial working memory). More frequent cannabis use and more extensive alcohol consumption were associated with a higher degree of impulsiveness.

CONCLUSIONS

Based on mild to moderate SU, little indication of differences in executive functioning was found. For ecstasy use, an increased error-proneness was revealed. The subtle differences in relatively young individuals warrant further investigation in prospective long-term studies to identify subjects at risk, and to examine effects of prolonged patterns of use on executive functioning.

Activation of the caudal anterior cingulate cortex due to task-related interference in an auditory Stroop paradigm

Successful information processing requires the focusing of attention on a certain stimulus property and the simultaneous suppression of irrelevant information. The Stroop task is a useful paradigm to study such attentional top-down control in the presence of interference. Here, we investigated the neural correlates of an auditory Stroop task using fMRI. Subjects focused either on tone pitch (relatively high or low; phonetic task) or on the meaning of a spoken word (high/low/good; semantic task), while ignoring the other stimulus feature. We differentiated between task-related (phonetic incongruent vs. semantic incongruent) and sensory-level interference (phonetic incongruent vs. phonetic congruent). Task-related interference activated similar regions as in visual Stroop tasks, including the anterior cingulate cortex (ACC) and the presupplementary motor-area (pre-SMA). More specifically, we observed that the very caudal/posterior part of the ACC was activated and not the dorsal/anterior region. Because identical stimuli but different task demands are compared in this contrast, it reflects conflict at a relatively high processing level. A more conventional contrast between incongruent and congruent phonetic trials was associated with a different cluster in the pre-SMA/ACC which was observed in a large number of previous studies. Finally, functional connectivity analysis revealed that activity within the regions activated in the phonetic incongruent vs. semantic incongruent contrast was more strongly interrelated during semantically vs. phonetically incongruent trials. Taken together, we found (besides activation of regions well-known from visual Stroop tasks) activation of the very caudal and posterior part of the ACC due to task-related interference in an auditory Stroop task.

The development of performance-monitoring function in the posterior medial frontal cortex

BACKGROUND

Despite its critical role in performance-monitoring, the development of posterior medial prefrontal cortex (pMFC) in goal-directed behaviors remains poorly understood. Performance monitoring depends on distinct, but related functions that may differentially activate the pMFC, such as monitoring response conflict and detecting errors. Developmental differences in conflict- and error-related activations, coupled with age-related changes in behavioral performance, may confound attempts to map the maturation of pMFC functions. To characterize the development of pMFC-based performance monitoring functions, we segregated interference and error-processing, while statistically controlling for performance.

METHODS

Twenty-one adults and 23 youth performed an event-related version of the Multi-Source Interference Task during functional magnetic resonance imaging (fMRI). Linear modeling of interference and error contrast estimates derived from the pMFC were regressed on age, while covarying for performance.

RESULTS

Interference- and error-processing were associated with robust activation of the pMFC in both youth and adults. Among youth, interference- and error-related activation of the pMFC increased with age, independent of performance. Greater accuracy associated with greater pMFC activity during error commission in both groups.

DISCUSSION

Increasing pMFC response to interference and errors occurs with age, likely contributing to the improvement of performance monitoring capacity during development.

Attention moderates the processing of inhibitory information in primary psychopathy

Primary psychopathic individuals are less apt to reevaluate or change their behavior in response to stimuli outside of their current focus of attention. According to the response modulation hypothesis, this tendency reflects a lack of responsivity to important peripheral information and undermines adaptive self-regulation. To evaluate this hypothesis, the authors administered a response competition (flanker-type) task and manipulated focus of visual attention. They predicted that psychopathic individuals would display significantly less interference to response incongruent information than nonpsychopathic participants when attention was cued to the target location but display normal interference when there was no prepotent focus of attention. The results confirmed this hypothesis and are consistent with the contention that attention moderates psychopathic individuals' responsivity to inhibitory cues. Implications of this attentional anomaly for psychopathic traits and behavior are discussed.

Why gamblers fail to win: a review of cognitive and neuroimaging findings in pathological gambling

The purpose of this review is to gain more insight in the neuropathology of pathological gambling (PG) and problem gambling, and to discuss challenges in this research area. Results from the reviewed PG studies show that PG is more than just an impulse control disorder. PG seems to fit very well with recent theoretical models of addiction, which stress the involvement of the ventral tegmental-orbito frontal cortex. Differentiating types of PG on game preferences (slot machines vs. casino games) seems to be useful because different PG groups show divergent results, suggesting different neurobiological pathways to PG. A framework for future studies is suggested, indicating the need for hypothesis driven pharmacological and functional imaging studies in PG and integration of knowledge from different research areas to further elucidate the neurobiological underpinnings of this disorder.

Conflict-induced behavioural adjustment: a clue to the executive functions of the prefrontal cortex

The behavioural adjustment that follows the experience of conflict has been extensively studied in humans, leading to influential models of executive-control adjustment. Recent studies have revealed striking similarities in conflict-induced behavioural adjustment between humans and monkeys, indicating that monkeys can provide a model to study the underlying neural substrates and mechanisms of such behaviour. These studies have advanced our knowledge about the role of different prefrontal brain regions, including the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (DLPFC), in executive-control adjustment and suggest a pivotal role for the DLPFC in the dynamic tuning of executive control and, consequently, in behavioural adaptation to changing environments.

Priming and backward influences in the human brain: processing interactions during the stroop interference effect

This study investigated neural processing interactions during Stroop interference by varying the temporal separation of relevant and irrelevant features of congruent, neutral, and incongruent colored-bar/color-word stimulus components. High-density event-related potentials (ERPs) and behavioral performance were measured as participants reported the bar color as quickly as possible, while ignoring the color words. The task-irrelevant color words could appear at 1 of 5 stimulus onset asynchronies (SOAs) relative to the task-relevant bar-color occurrence: -200 or -100 ms before, +100 or +200 ms after, or simultaneously. Incongruent relative to congruent presentations elicited slower reaction times and higher error rates (with neutral in between), and ERP difference waves containing both an early, negative-polarity, central-parietal deflection, and a later, more left-sided, positive-polarity component. These congruency-related differences interacted with SOA, showing the greatest behavioral and electrophysiological effects when irrelevant stimulus information preceded the task-relevant target and reduced effects when the irrelevant information followed the relevant target. We interpret these data as reflecting 2 separate processes: 1) a 'priming influence' that enhances the magnitude of conflict-related facilitation and conflict-related interference when a task-relevant target is preceded by an irrelevant distractor; and 2) a reduced 'backward influence' of stimulus conflict when the irrelevant distractor information follows the task-relevant target.

A critical role for the right fronto-insular cortex in switching between central-executive and default-mode networks

Cognitively demanding tasks that evoke activation in the brain's central-executive network (CEN) have been consistently shown to evoke decreased activation (deactivation) in the default-mode network (DMN). The neural mechanisms underlying this switch between activation and deactivation of large-scale brain networks remain completely unknown. Here, we use functional magnetic resonance imaging (fMRI) to investigate the mechanisms underlying switching of brain networks in three different experiments. We first examined this switching process in an auditory event segmentation task. We observed significant activation of the CEN and deactivation of the DMN, along with activation of a third network comprising the right fronto-insular cortex (rFIC) and anterior cingulate cortex (ACC), when participants perceived salient auditory event boundaries. Using chronometric techniques and Granger causality analysis, we show that the rFIC-ACC network, and the rFIC, in particular, plays a critical and causal role in switching between the CEN and the DMN. We replicated this causal connectivity pattern in two additional experiments: (i) a visual attention "oddball" task and (ii) a task-free resting state. These results indicate that the rFIC is likely to play a major role in switching between distinct brain networks across task paradigms and stimulus modalities. Our findings have important implications for a unified view of network mechanisms underlying both exogenous and endogenous cognitive control.