Transient activation of inferior prefrontal cortex during cognitive set shifting

Proteomic association with age-dependent sex differences in Wisconsin Card Sorting Test performance in healthy Thai subjects

Sex differences in cognitive function exist, but they are not stable and undergo dynamic change during the lifespan. However, our understanding of how sex-related neural information transmission evolves with age is still in its infancy. This study utilized the Wisconsin Card Sorting Test (WCST) and the label-free proteomics method with bioinformatic analysis to investigate the molecular mechanisms underlying age-related sex differences in cognitive performance in 199 healthy Thai subjects (aged 20-70 years), as well as explore the sex-dependent protein complexes for predicting cognitive aging. The results showed that males outperformed females in two of the five WCST sub-scores: %Corrects and %Errors. Sex differences in these scores were related to aging, becoming noticeable in those over 60. At the molecular level, differently expressed individual proteins and protein complexes between both sexes are associated with the potential N-methyl-D-aspartate type glutamate receptor (NMDAR)-mediated excitotoxicity, with the NMDAR complex being enriched exclusively in elderly female samples. These findings provided a preliminary indication that healthy Thai females might be more susceptible to such neurotoxicity, as evidenced by their cognitive performance. NMDAR protein complex enrichment in serum could be proposed as a potential indication for predicting cognitive aging in healthy Thai females.

An fNIRS Study of Applicability of the Unity-Diversity Model of Executive Functions in Preschoolers

Executive function (EF) includes a set of higher-order abilities that control one's actions and thoughts consciously and has a protracted developmental trajectory that parallels the maturation of the frontal lobes, which develop speedily over the preschool period. To fully understand the development of EF in preschoolers, this study examined the relationship among the three domains of executive function (cognitive shifting, inhibitory control, and working memory) to test the applicability of the unity-diversity model in preschoolers using both behavioral and fNIRS approaches. Altogether, 58 Chinese preschoolers (34 boys, 24 girls, M_age = 5.86 years, SD = 0.53, age range = 4.83-6.67 years) were administered the Dimensional Card Change Sort (DCCS), go/no-go, and missing scan task. Their brain activations in the prefrontal cortex during the tasks were examined using fNIRS. First, the behavioral results indicated that the missing scan task scores (working memory) correlated with the DCCS (cognitive shifting) and go/no-go tasks (inhibitory control). However, the latter two did not correlate with each other. Second, the fNIRS results demonstrated that the prefrontal activations during the working memory task correlated with those in the same regions during the cognitive shifting and inhibitory control tasks. However, the latter two still did not correlate. The behavioral and neuroimaging evidence jointly indicates that the unity-diversity model of EF does apply to Chinese preschoolers.

Repetitive transcranial magnetic stimulation decreased effortful frontal activity for shifting in patients with major depressive disorder

Patients with major depressive disorder (MDD) exhibit several clinical symptoms including difficulties in flexible thinking. Flexible thinking mainly relies on a cognitive ability called shifting; however, the mechanisms underlying shifting in patients with MDD have not yet been clarified. Therefore, we conducted a preliminary intervention study to clarify the association between depression and shifting ability. We examined the hemodynamic responses in the frontal regions during the shifting task using functional near-infrared spectroscopy (fNIRS) in 21 patients with MDD who were treated using high-frequency repetitive transcranial magnetic stimulation (rTMS). Behavioral performance on the shifting task did not change between pre- and posttreatments, whereas patients who responded well to rTMS treatment showed a significant decrease in hemodynamic responses posttreatment. On the other hand, the poor responders did not show significant changes in the hemodynamic responses between pre- and posttreatments. These results suggest that the good responders were successfully remedied with rTMS treatment and did not need effortful activity in frontal regions for shifting, which made their brain activity more efficient.

Reorganization of prefrontal network in stroke patients with dyskinesias: evidence from resting-state functional near-infrared spectroscopy

Stroke usually causes multiple functional disability. To develop novel rehabilitation strategies, it is quite necessary to improve the understanding of post-stroke brain plasticity. Here, we use functional near-infrared spectroscopy to investigate the prefrontal cortex (PFC) network reorganization in stroke patients with dyskinesias. The PFC hemodynamic signals in the resting state from 16 stroke patients and 10 healthy subjects are collected and analyzed with the graph theory. The PFC networks for both groups show small-world attributes. The stroke patients have larger clustering coefficient and transitivity and smaller global efficiency and small-worldness than healthy subjects. Based on the selected network features, the established support vector machine model classifies the two groups of subjects with an accuracy rate of 88.5%. Besides, the clustering coefficient and local efficiency negatively correlate with patients' motor function. This study suggests that the PFC of stroke patients with dyskinesias undergoes specific network reorganization.

Exploring behavioural and cognitive dysexecutive syndrome in patients with focal prefrontal cortex damage

This study's objectives were to characterize the frequency and profile of behavioral and cognitive dysexecutive syndromes in patients with focal prefrontal cortex damage and how these syndromes overlap. We also examined the contribution of the prefrontal brain regions to these syndromes. Therefore, thirty patients with prefrontal cortex damage and thirty control subjects were compared on their performances using the GREFEX battery assessing the dysexecutive syndromes. The results showed that combined behavioral and cognitive dysexecutive syndrome was observed in 53.33%, while pure cognitive dysexecutive syndrome was observed in 20% and behavioral in 26.67%. Also, almost all behavioral and cognitive dysexecutive disorders discriminated frontal patients from controls. Moreover, correlations and regression analyses between task scores in both domains of dysexecutive syndromes showed that the spectrum of behavioral disorders was differentially associated with cognitive impairment of initiation, inhibition, generation, deduction, coordination, flexibility and the planning process. Furthermore, the patterns of cognitive and behavioral dysexecutive syndrome were both predictors of impairment in daily living activities and loss of autonomy. Finally, frontal regions contributing to different dysexecutive syndromes assessed by MRI voxel lesion symptom analysis indicate several overlapping regions centered on the ventromedial and dorsomedial prefrontal cortex for both domains of dysexecutive syndrome. This study concludes that damage to the frontal structures may lead to a diverse set of changes in both cognitive and behavioral domains which both contribute to loss of autonomy. The association of the ventromedial and dorsomedial prefrontal regions to both domains of dysexecutive syndrome suggests a higher integrative role of these regions in processing cognition and behavior.

Relationship between motor learning and gambling propensity in Parkinson's disease

INTRODUCTION

The basal ganglia and related dopaminergic cortical areas are important neural systems underlying motor learning and are also implicated in impulse control disorders (ICDs). Motor learning impairments and ICDs are frequently observed in Parkinson's disease (PD). Nevertheless, the relationship between motor learning ability and ICDs has not been elucidated.

METHODS

We examined the relationship between motor learning ability and gambling propensity, a possible symptom for prodromal ICDs, in PD patients. Fifty-nine PD patients without clinical ICDs and 43 normal controls (NC) were administered a visuomotor rotation perturbation task and the Iowa Gambling Task (IGT) to evaluate motor learning ability and gambling propensity, respectively. Participants also performed additional cognitive assessments and underwent brain perfusion SPECT imaging.

RESULTS

Better motor learning ability was significantly correlated with lower IGT scores, i.e., higher gambling propensity, in PD patients but not in NC. The higher scores on assessments reflecting prefrontal lobe function and well-preserved blood perfusion in prefrontal areas were correlated with lower IGT scores along with better motor learning ability.

CONCLUSIONS

Our findings suggest that better motor learning ability and higher gambling propensity are based on better prefrontal functions, which are in accordance with the theory that the prefrontal cortex is one of the common essential regions for both motor learning and ICDs.

A Predictive Processing Account of Card Sorting: Fast Proactive and Reactive Frontoparietal Cortical Dynamics during Inference and Learning of Perceptual Categories

For decades, a common assumption in cognitive neuroscience has been that prefrontal executive control is mainly engaged during target detection [Posner, M. I., & Petersen, S. E. The attention system of the human brain. Annual Review of Neuroscience, 13, 25-42, 1990]. More recently, predictive processing theories of frontal function under the Bayesian brain hypothesis emphasize a key role of proactive control for anticipatory action selection (i.e., planning as active inference). Here, we review evidence of fast and widespread EEG and magnetoencephalographic fronto-temporo-parietal cortical activations elicited by feedback cues and target cards in the Wisconsin Card Sorting Test. This evidence is best interpreted when considering negative and positive feedback as predictive cues (i.e., sensory outcomes) for proactively updating beliefs about unknown perceptual categories. Such predictive cues inform posterior beliefs about high-level hidden categories governing subsequent response selection at target onset. Quite remarkably, these new views concur with Don Stuss' early findings concerning two broad classes of P300 cortical responses evoked by feedback cues and target cards in a computerized Wisconsin Card Sorting Test analogue. Stuss' discussion of those P300 responses-in terms of the resolution of uncertainty about response (policy) selection as well as the participants' expectancies for future perceptual or motor activities and their timing-was prescient of current predictive processing and active (Bayesian) inference theories. From these new premises, a domain-general frontoparietal cortical network is rapidly engaged during two temporarily distinct stages of inference and learning of perceptual categories that underwrite goal-directed card sorting behavior, and they each engage prefrontal executive functions in fundamentally distinct ways.

An fMRI study of age-associated changes in basic visual discrimination

Clinical neuropsychology lacks tests of basic visuoperceptual and spatial skills that have well-controlled administration and sophisticated measurement methods. Items from the Visual Assessment Battery (VAB), a simultaneous match-to-sample task, assessed visual discrimination in 40 healthy adults aged 51-91 during fMRI. The tasks were designed to isolate discrimination of either location, shape, or velocity, and they each had three levels of difficulty. The Location task uniquely activated the dorsal visual processing stream, the Shape task the ventral stream, and the Velocity task an area encompassing V5. Greater age was associated with greater neural recruitment, particularly in frontal areas. Behaviorally, greater age was associated with prolonged response times, but not reduced accuracy. Increased difficulty was associated with slower responses and reduced accuracy, regardless of age. Results validated the specialization of brain regions for spatial, perceptual, and movement discriminations and the use of the VAB to assess functioning localized to these regions. Visual discrimination ability does not change dramatically with age, but like many cognitive processes, performance slows. Anterior neural recruitment during visual discrimination increases with age.

The Role of Primate Prefrontal Cortex in Bias and Shift Between Visual Dimensions

Imaging and neural activity recording studies have shown activation in the primate prefrontal cortex when shifting attention between visual dimensions is necessary to achieve goals. A fundamental unanswered question is whether representations of these dimensions emerge from top-down attentional processes mediated by prefrontal regions or from bottom-up processes within visual cortical regions. We hypothesized a causative link between prefrontal cortical regions and dimension-based behavior. In large cohorts of humans and macaque monkeys, performing the same attention shifting task, we found that both species successfully shifted between visual dimensions, but both species also showed a significant behavioral advantage/bias to a particular dimension; however, these biases were in opposite directions in humans (bias to color) versus monkeys (bias to shape). Monkeys' bias remained after selective bilateral lesions within the anterior cingulate cortex (ACC), frontopolar cortex, dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex (OFC), or superior, lateral prefrontal cortex. However, lesions within certain regions (ACC, DLPFC, or OFC) impaired monkeys' ability to shift between these dimensions. We conclude that goal-directed processing of a particular dimension for the executive control of behavior depends on the integrity of prefrontal cortex; however, representation of competing dimensions and bias toward them does not depend on top-down prefrontal-mediated processes.

Shared cognitive mechanisms of hypnotizability with executive functioning and information salience

In recent years, evidence linked hypnotizability to the executive control and information salience networks, brain structures that play a role in cognitive conflict resolution and perseveration (insisting on applying a previously learned logical rule on a new set). Despite the growing body of neuroimaging evidence, the cognitive phenotype of hypnotizability is not well understood. We hypothesized that higher hypnotizability would correspond to lower perseveration and set-shifting. Seventy-two healthy adults were tested for hypnotizability and executive functions (perseveration and set-shifting). Multiple regression analyses were performed to test the relationship between hypnotizability and perseveration and set-shifting. Higher hypnotizability was associated with lower perseveration after accounting for age and education. Hypnotizability significantly predicted perseveration but not set-shifting. Our results indicate an inverse relationship between trait hypnotizability and perseveration, an executive function that utilizes regions of both the executive control and the salience systems. This suggests that hypnotizability may share a common cognitive mechanism with error evaluation and implementation of logical rules.

Dimensional bias and adaptive adjustments in inhibitory control of monkeys

Humans and macaque monkeys, performing a Wisconsin Card Sorting Test (WCST), show a significant behavioral bias to a particular sensory dimension (e.g. color or shape); however, lesions in prefrontal cortical regions do not abolish the dimensional biases in monkeys and, therefore, it has been proposed that these biases emerge in earlier stages of visual information processing. It remains unclear whether such dimensional biases are unique to the WCST, in which attention-shifting between dimensions are required, or affect other aspects of executive functions such as 'response inhibition' and 'error-induced behavioral adjustments'. To address this question, we trained six monkeys (Macaca mulatta) to perform a stop-signal task in which they had to inhibit their response when an instruction for inhibition was given by changing the color or shape of a visual stimulus. Stop Signal Reaction Time (SSRT) is an index of inhibitory processes. In all monkeys, SSRT was significantly shorter, and the probability of a successful inhibition was significantly higher, when a change in the shape dimension acted as the stop-cue. Humans show a response slowing following a failure in response inhibition and also adapt a proactive slowing after facing demands for response inhibition. We found such adaptive behavioral adjustments, with the same pattern, in monkeys' behavior; however, the dimensional bias did not modulate them. Our findings, showing dimensional bias in monkey, with the same pattern, in two different executive control tasks support the hypothesis that the bias to shape dimension emerges in early stages of visual information processing.

Acute Exercise-Induced Set Shifting Benefits in Healthy Adults and Its Moderators: A Systematic Review and Meta-Analysis

Background: Positive effects of acute exercise on cognitive performances in general inspired research that investigated the effects of acute exercise on specific cognitive subdomains. Many existing studies examined beneficial effects of acute exercise on subsequent set shifting performance in healthy adults. Set shifting, a subdomain of executive function, is the ability to switch between different cognitive sets. The results of existing studies are inconsistent. Therefore, a meta-analysis was conducted that pooled available effect sizes. Additionally, moderator analyses were carried out to identify covariates that determine the magnitude of exercise-induced set shifting benefits.

Methods: Medline, PsycINFO, and SPORTDiscus were searched for eligible studies. Hedges' g corrected standardized mean difference values were used for analyses. Random-effects weights were applied to pool effects. Potential moderation of the effect of acute exercise on subsequent set shifting performance by exercise intensity, type of exercise, participants' age, and type of control group were examined.

Results: Twenty-two studies (N = 1,900) were included into analysis. All aggregated effect sizes ranged from small to moderate. Overall, a small significant beneficial effect was revealed (g = −0.32, 95 % CI −0.45 to −0.18). Heterogeneity of included effect sizes was moderate and significant (T² = 0.0715, I² = 46.4%, (p < 0.0016). Moderator analyses revealed a larger average effect in older adults than for studies examining younger adults (−0.42 vs. −0.29). Light exercise (−0.51) led to larger effects than moderate (−0.24) or vigorous exercise (−0.29). Studies testing acute exercise against active control groups showed a noticeably smaller average effect (−0.13) than studies that used passive (−0.38) or cognitive engaging control groups (−0.34). Interestingly, application of resistance or aerobic exercise led to no different average effect sizes (−0.30 vs. −0.32). However, none of the tested covariates reached statistical significance.

Conclusion: Acute exercise improves subsequent set shifting performance. However, effect sizes are small, making the relevance for everyday life questionable. The results indicate that older adults benefit more from acute exercise than younger adults do. Light intensity exercise seems most effective while the type of exercise does not seem to influence the magnitude of effects. Research designs with active control groups show the smallest average effect, raising concerns about placebo effects.

PROSPERO registration number: CRD42019138799

Cross-Hemispheric Complementary Prefrontal Mechanisms during Task Switching under Perceptual Uncertainty

Flexible adaptation to changing environments is a representative executive control function implicated in the frontoparietal network that requires appropriate extraction of goal-relevant information through perception of the external environment. It remains unclear, however, how the flexibility is achieved under situations where goal-relevant information is uncertain. To address this issue, the current study examined neural mechanisms for task switching in which task-relevant information involved perceptual uncertainty. Twenty-eight human participants of both sexes alternated behavioral tasks in which they judged motion direction or color of visually presented colored dot stimuli that moved randomly. Task switching was associated with frontoparietal regions in the left hemisphere, and perception of ambiguous stimuli involved contralateral homologous frontoparietal regions. On the other hand, in stimulus-modality-dependent occipitotemporal regions, task coding information was increased during task switching. Effective connectivity analysis revealed that the frontal regions signaled toward the modality-dependent occipitotemporal regions when a relevant stimulus was more ambiguous, whereas the occipitotemporal regions signaled toward the frontal regions when the stimulus was more distinctive. These results suggest that complementary prefrontal mechanisms in the left and right hemispheres help to achieve a behavioral goal when the external environment involves perceptual uncertainty.SIGNIFICANCE STATEMENT In our daily life, environmental information to achieve a goal is not always certain, but we make judgments in such situations, and change our behavior accordingly. This study examined how the flexibility of behavior is achieved in a situation where goal-relevant information involves perceptual uncertainty. fMRI revealed that the lateral prefrontal cortex (PFC) in the left hemisphere is associated with behavioral flexibility, and the perception of ambiguous stimuli involves the PFC in the right hemisphere. These bilateral PFC signaled to stimulus-modality-dependent occipitotemporal regions, depending on perceptual uncertainty and the task to be performed. These top-down signals supplement task coding in the occipitotemporal regions, and highlight interhemispheric prefrontal mechanisms involved in executive control and perceptual decision-making.

Serial-multiple mediation of enjoyment and intention on the relationship between creativity and physical activity

The purpose of the present study was to examine a serial-multiple mediation of physical activity (PA) enjoyment and PA intention in the relationship between creativity and PA level (i.e., moderate-to-vigorous PA). A total of 298 undergraduate and graduate students completed a self-reported questionnaire evaluating creativity, PA enjoyment, PA intention, and PA level. Data analysis was conducted using descriptive statistics, Pearson correlation coefficient, ordinary least-squares regression analysis, and bootstrap methodology. Based on the research findings, both PA enjoyment (β = 0.06; 95% CI [0.003, 0.12]) and PA intention (β = 0.08; 95% CI [0.03, 0.13]) were found to be a mediator of the relationship between creativity and PA level, respectively. Moreover, the serial-multiple mediation of PA enjoyment and PA intention in the relationship between creativity and PA level was statistically significant (β = 0.02; 95% CI [0.01, 0.04]). These findings underscore the importance of shaping both cognitive and affective functions for PA promotion and provide additional support for a neurocognitive affect-related model in the PA domain. In order to guide best practices for PA promotion programs aimed at positively influencing cognition and affect, future PA interventions should develop evidence-based strategies that routinely evaluate cognitive as well as affective responses to PA.

Reliable change in neuropsychological test scores is associated with brain atrophy in older adults

The reliable change index (RCI) is a commonly used method for interpreting change in neuropsychological test scores over time. However, the RCI is a psychometric method that, to date, has not been validated against neuroanatomical changes. Longitudinal neuroimaging and neuropsychological data from baseline and one-year follow-up visits were retrieved from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. The RCI was used to identify participants showing reliable decline on memory (ADNI-Mem; N = 450) and executive functioning (ADNI-EF; N = 456) factor scores. For each factor score, two groups (reliable change vs. no reliable change) were matched on potential baseline confounding variables. Longitudinal neuroanatomical data were analysed using tensor-based morphometry. Analysis revealed that reliable change on ADNI-Mem was associated with atrophy in the medial temporal cortex, limbic cortex, temporal lobe and some regions of the parietal lobe. Similar atrophy patterns were found for reliable change on ADNI-EF, except that atrophy extended to the frontal lobe and the atrophy was more extensive and of higher magnitude. The current study not only validates clinical usage of the RCI with neuroanatomical evidence of associated underlying brain change but also suggests patterns of likely brain atrophy when reliable cognitive decline is detected.

Measuring Cognitive Flexibility with the Flexible Item Selection Task: From fMRI Adaptation to Individual Connectome Mapping

Cognitive flexibility, the ability to appropriately adjust behavior in a changing environment, has been challenging to operationalize and validate in cognitive neuroscience studies. Here, we investigate neural activation and directed functional connectivity underlying cognitive flexibility using an fMRI-adapted version of the Flexible Item Selection Task (FIST) in adults (n = 32, ages 19-46 years). The fMRI-adapted FIST was reliable, showed comparable performance to the computer-based version of the task, and produced robust activation in frontoparietal, anterior cingulate, insular, and subcortical regions. During flexibility trials, participants directly engaged the left inferior frontal junction, which influenced activity in other cortical and subcortical regions. The strength of intrinsic functional connectivity between select brain regions was related to individual differences in performance on the FIST, but there was also significant individual variability in functional network topography supporting cognitive flexibility. Taken together, these results suggest that the FIST is a valid measure of cognitive flexibility, which relies on computations within a broad corticosubcortical network driven by inferior frontal junction engagement.

"Placebo by Proxy" and "Nocebo by Proxy" in Children: A Review of Parents' Role in Treatment Outcomes

The "placebo (effect) by proxy" (PbP) concept, introduced by Grelotti and Kaptchuk (1), describes a positive effect of a patient's treatment on persons in their surrounding such as family members or healthcare providers, who feel better because the patient is being treated. The PbP effect is a complex dynamic phenomenon which attempts to explain a change in treatment outcome arising from an interaction between a patient and an effect from proxies such as parents, caregivers, physicians or even the media. By extension the effect of the proxy can also have a negative or adverse effect whereby a proxy feels worse when a patient is treated, giving rise to the possibility of a "nocebo (effect) by proxy" (NbP), and by extension can influence a patient's treatment response. While this has yet to be systematically investigated, such an effect could occur when a proxy observes that a treatment is ineffective or is perceived as causing adverse effects leading the patient to experience side effects. In this narrative review, we take these definitions one step further to include the impact of PbP/NbP as they transform to affect the treatment outcome for the patient or child being treated, not just the people surrounding the individual being treated. Following a systematic search of literature on the subject using the Journal of Interdisciplinary Placebo Studies (JIPS) database (https://jips.online) and PubMed (NCBI) resulted in very few relevant studies, especially in children. The effect of PbP per se has been studied in parents and their children for temper tantrums, acupuncture for postoperative symptoms, as well as for neuroprotection in very preterm-born infants. This paper will review the PbP/NbP concepts, show evidence for its presence in children's treatment outcome and introduce clinical implications. We will also offer suggestions for future research to further our understanding of the role of the proxy in promoting or distracting from treatment benefit in children. Increasing an appreciation of the PbP and NbP phenomena and the role of the proxy in children's treatment should improve research study design and ultimately harness them to improve clinical child healthcare.

Beyond consensus: Embracing heterogeneity in curated neuroimaging meta-analysis

Coordinate-based meta-analysis can provide important insights into mind-brain relationships. A popular approach for curated small-scale meta-analysis is activation likelihood estimation (ALE), which identifies brain regions consistently activated across a selected set of experiments, such as within a functional domain or mental disorder. ALE can also be utilized in meta-analytic co-activation modeling (MACM) to identify brain regions consistently co-activated with a seed region. Therefore, ALE aims to find consensus across experiments, treating heterogeneity across experiments as noise. However, heterogeneity within an ALE analysis of a functional domain might indicate the presence of functional sub-domains. Similarly, heterogeneity within a MACM analysis might indicate the involvement of a seed region in multiple co-activation patterns that are dependent on task contexts. Here, we demonstrate the use of the author-topic model to automatically determine if heterogeneities within ALE-type meta-analyses can be robustly explained by a small number of latent patterns. In the first application, the author-topic modeling of experiments involving self-generated thought (N = 179) revealed cognitive components fractionating the default network. In the second application, the author-topic model revealed that the left inferior frontal junction (IFJ) participated in multiple task-dependent co-activation patterns (N = 323). Furthermore, the author-topic model estimates compared favorably with spatial independent component analysis in both simulation and real data. Overall, the results suggest that the author-topic model is a flexible tool for exploring heterogeneity in ALE-type meta-analyses that might arise from functional sub-domains, mental disorder subtypes or task-dependent co-activation patterns. Code for this study is publicly available (https://github.com/ThomasYeoLab/CBIG/tree/master/stable_projects/meta-analysis/Ngo2019_AuthorTopic).

Cognitive Inflexibility Predicts Extremist Attitudes

Research into the roots of ideological extremism has traditionally focused on the social, economic, and demographic factors that make people vulnerable to adopting hostile attitudes toward outgroups. However, there is insufficient empirical work on individual differences in implicit cognition and information processing styles that amplify an individual’s susceptibility to endorsing violence to protect an ideological cause or group. Here we present original evidence that objectively assessed cognitive inflexibility predicts extremist attitudes, including a willingness to harm others, and sacrifice one’s life for the group. Across two samples (N = 1,047) from the United Kingdom and United States, structural equation models demonstrated that cognitive inflexibility predicted endorsement of violence to protect the national ingroup, which in turn predicted a willingness to die for the group. These statistical models accounted for an average of 31.4% of the variance in willingness to die for the group, after accounting for demographic variables. Furthermore, cognitive inflexibility was related to greater confidence in the decision to sacrifice one’s life in an ingroup trolley problem scenario. Analysis of participants’ performance on the cognitive tasks revealed that cognitive rigidity – distinctly from other aspects of cognition – was specifically implicated as a cognitive antecedent of extremist attitudes. Implications for the study of radicalization and identity fusion through a neurocognitive lens are discussed.

The Relationship between Mismatch Negativity and the COMTVal108/158Met Genotype in Schizophrenia

Mismatch negativity (MMN) is a component of auditory event-related potentials that reflects automatic change detection in the brain, showing qualities of endophenotypes in schizophrenia. MMN deficiency is one of the robust findings in patients, and it reflects both cognitive and functional decline. Catechol-o-methyltransferase (COMT) is a key enzyme involved in regulating dopamine transmission within the prefrontal cortex. A preliminary study suggested that the COMTVal108/158Met genotype (rs4680) is related to cognitive function in schizophrenia. Both the COMTVal108/158Met genotype and MMN are related to cognitive function, but no studies have reported on the relationship between MMN and the COMTVal108/158Met genotype in schizophrenia. This study therefore examined the relationship between COMTVal108/158Met genotype and MMN. The duration of MMN was measured, and the COMTVal108/158Met polymorphism was detected by polymerase chain reaction-restriction fragment length polymorphism in 49 Japanese schizophrenia patients (Val/Val, n = 21; Met carriers, n = 28). Amplitude and latency of MMN were compared between Val/Val and Met carriers.

Age-related decline in cognitive flexibility in female chimpanzees

Data on cognitive aging in chimpanzees are extremely sparse, yet can provide an invaluable phylogenetic perspective, especially because Alzheimer disease (AD)-like neuropathology has recently been described in the oldest chimpanzee brains. This finding underscores the importance of data on cognitive aging in this fellow hominin, our closest biological relative. We tested 30 female chimpanzees, 12-56 years old, on a computerized analog of the Wisconsin Card Sort test. This test assesses cognitive flexibility, which is severely impaired in normal aging and AD. Subjects selected stimuli according to color or shape; the rewarded dimension (i.e., color or shape) switched without warning and the chimpanzee had to adapt her responses accordingly. We found that increasing age was associated with an increased number of perseverative errors and an increased number of trials to reach criterion in each switching dimension. The number of aborted trials was similar across age groups. These data show that similar to humans, chimpanzees show a clear age-related decline in cognitive flexibility that is already observed at middle age.

Abnormalities in gray matter microstructure in young adults with 22q11.2 deletion syndrome

BACKGROUND

22q11.2 Deletion Syndrome (22q11DS) is a genetic, neurodevelopmental disorder characterized by a chromosomal deletion and a distinct cognitive profile. Although abnormalities in the macrostructure of the cortex have been identified in individuals with 22q11DS, it is not known if there are additional microstructural changes in gray matter regions in this syndrome, and/or if such microstructural changes are associated with cognitive functioning.

METHODS

This study employed a novel diffusion MRI measure, the Heterogeneity of Fractional Anisotropy (HFA), to examine variability in the microstructural organization of the cortex in healthy young adults (N = 30) and those with 22q11DS (N = 56). Diffusion MRI, structural MRI, clinical and cognitive data were acquired.

RESULTS

Compared to controls, individuals with 22q11DS evinced increased HFA in cortical association (p = .003, d = 0.86) and paralimbic (p < .0001, d = 1.2) brain areas, whereas no significant differences were found between the two groups in primary cortical brain areas. Additionally, increased HFA of the right paralimbic area was associated with poorer performance on tests of response inhibition, i.e., the Stroop Test (rho = -0.37 p = .005) and the Gordon Diagnostic System Vigilance Commission (rho = -0.41 p = .002) in the 22q11DS group. No significant correlations were found between HFA and cognitive abilities in the healthy control group.

CONCLUSIONS

These findings suggest that cortical microstructural disorganization may be a neural correlate of response inhibition in individuals with 22q11DS. Given that the migration pattern of neural crest cells is disrupted at the time of early brain development in 22q11DS, we hypothesize that these neural alterations may be neurodevelopmental in origin, and reflect cortical dysfunction associated with cognitive deficits.

Functional dissociation of the inferior frontal junction from the dorsal attention network in top-down attentional control

The posterior lateral prefrontal cortex-specifically, the inferior frontal junction (IFJ)-is thought to exert a key role in the control of attention. However, the precise nature of that role remains elusive. During the voluntary deployment and maintenance of visuospatial attention, the IFJ is typically coactivated with a core dorsal network consisting of the frontal eye field and superior parietal cortex. During stimulus-driven attention, IFJ instead couples with a ventrolateral network, suggesting that IFJ plays a role in attention distinct from the dorsal network. Because IFJ rapidly switches activation patterns to accommodate conditions of goal-directed and stimulus-driven attention (Asplund CL, Todd JJ, Snyder AP, Marois R. Nat Neurosci 13: 507-512, 2010), we hypothesized that IFJ's primary role is to dynamically reconfigure attention rather than to maintain attention under steady-state conditions. This hypothesis predicts that in a goal-directed visuospatial cuing paradigm IFJ would transiently deploy attention toward the cued location, whereas the dorsal attention network would maintain attentional weights during the delay between cue and target presentation. Here we tested this hypothesis with functional magnetic resonance imaging while subjects were engaged in a Posner cuing task with variable cue-target delays. Both IFJ and dorsal network regions were involved in transient processes, but sustained activity was far more evident in the dorsal network than in IFJ. These results support the account that IFJ primarily acts to shift attention whereas the dorsal network is the main locus for the maintenance of stable attentional states. NEW & NOTEWORTHY Goal-directed visuospatial attention is controlled by a dorsal fronto-parietal network and lateral prefrontal cortex. However, the relative roles of these regions in goal-directed attention are unknown. Here we present evidence for their dissociable roles in the transient reconfiguration and sustained maintenance of attentional settings: while maintenance of attentional settings is confined to the dorsal network, the configuration of these settings at the beginning of an attentional episode is a function of lateral prefrontal cortex.

Executive Functions Brain System: An Activation Likelihood Estimation Meta-analytic Study

Background and objective

To characterize commonalities and differences between two executive functions: reasoning and inhibitory control.

Methods

A total of 5,974 participants in 346 fMRI experiments of inhibition or reasoning were selected. First level analysis consisted of Analysis of Likelihood Estimation (ALE) studies performed in two pooled data groups: (a) brain areas involved in reasoning and (b) brain areas involved in inhibition. Second level analysis consisted of two contrasts: (i) brain areas involved in reasoning but not in inhibition and (ii) brain areas involved in inhibition but not in reasoning. Lateralization Indexes were calculated.

Results

Four brain areas appear as the most critical: the dorsolateral aspect of the frontal lobes, the superior parietal lobules, the mesial aspect of the premotor area (supplementary motor area), and some subcortical areas, particularly the putamen and the thalamus. ALE contrasts showed significant differentiation of the networks, with the reasoning > inhibition-contrast showing a predominantly leftward participation, and the inhibition > reasoning-contrast, a clear right advantage.

Conclusion

Executive functions are mediated by sizable brain areas including not only cortical, but also involving subcortical areas in both hemispheres. The strength of activation shows dissociation between the hemispheres for inhibition (rightward) and reasoning (leftward) functions.

Bilateral Transcranial Magnetic Stimulation on DLPFC Changes Resting State Networks and Cognitive Function in Patients With Bipolar Depression

Introduction: Bipolar patients have abnormalities in cognitive functions and emotional processing. Two resting state networks (RSNs), the default mode network (DMN) and the sensorimotor network (SMN), play a decisive role in these two functions. Dorsolateral prefrontal cortex (DLPFC) is one of the main areas in the central executive network (CEN), which is linked to the activities of each of the two networks. Studies have found DLPFC abnormalities in both hemispheres of patients with bipolar depression. We hypothesized that the bilateral repetitive transcranial magnetic stimulation (rTMS) of DLPFC would produce changes in the activity of both the SMN and DMN as well as relevant cognitive function in patients with bipolar depression that responded to treatment.

Methods: 20 patients with bipolar depression underwent 10 sessions of 1 Hz rTMS on right DLPFC with subsequent 10 Hz rTMS on left DLPFC. Changes in electroencephalography resting networks between pre and post rTMS were evaluated utilizing low-resolution electromagnetic tomography (eLORETA). Depression symptom was assessed using the Beck Depression Inventory (BDI-II) and cognitive function was assessed by Verbal Fluency Test (VFT), Rey Auditory Verbal Learning Test (RAVLT), Stroop Test, and Wisconsin Card Sorting Test (WCST).

Results: Responders to rTMS showed significantly lower DMN activity at baseline and a significant decrease in SMN connectivity after treatment. Non-responders did not significantly differ from the control group at the baseline and they showed higher activity in the SMN, visual network, and visual perception network compared to control group following treatment. Bilateral rTMS resulted in significant changes in the executive functions, verbal memory, and depression symptoms. No significant changes were observed in selective attention and verbal fluency.

Conclusion: Bilateral stimulation of DLPFC, as the main node of CEN, results in changes in the activity of the SMN and consequently improves verbal memory and executive functions in patients with bipolar depression.

Relationships between executive function, working memory, and decision-making on the Iowa Gambling Task: Evidence from ventromedial patients, dorsolateral patients, and normal subjects

The results of previous studies are inconsistent in regard to the relationship between the Iowa Gambling Task (IGT), working-memory (WM), and executive tasks, and whether these cognitive processes could be considered as mechanisms underlying a decision-making deficit. Moreover, the relationship between the IGT and executive measures is examined based on a limited number of executive tasks, within different populations showing diffuse damage. In addition, there are fewer studies carried out within control participants, with those studies also being inconclusive. It is also suggested that the association of the IGT performance with executive tasks depends on whether the IGT was running under ambiguity or under risk. In this work, all of these issues are studied. Results showed that both patients with ventromedial (VMPFC, N = 10) and dorsolateral (DLPFC, N = 10) prefrontal cortex lesions are significantly impaired on almost all executive tasks, WM tasks, and the IGT. Furthermore, when the IGT is run under risk, there are significant correlations between executive measures and the IGT for the DLPFC patients and the control participants (N = 34) but not the VMPFC patients. No correlation was found between WM tasks and the IGT for both frontal subgroups and control participants. These findings suggested that the mechanisms underlying the IGT deficit differ according to the lesion locations.

Lateral prefrontal cortex lesion impairs regulation of internally and externally directed attention

Our capacity to flexibly shift between internally and externally directed attention is crucial for successful performance of activities in our daily lives. Neuroimaging studies have implicated the lateral prefrontal cortex (LPFC) in both internally directed processes, including autobiographical memory retrieval and future planning, and externally directed processes, including cognitive control and selective attention. However, the causal involvement of the LPFC in regulating internally directed attention states is unknown. The current study recorded scalp EEG from patients with LPFC lesions and healthy controls as they performed an attention task that instructed them to direct their attention either to the external environment or their internal milieu. We compared frontocentral midline theta and posterior alpha between externally and internally directed attention states. While healthy controls showed increased theta power during externally directed attention and increased alpha power during internally directed attention, LPFC patients revealed no differences between the two attention states in either electrophysiological measure in the analyzed time windows. These findings provide evidence that damage to the LPFC leads to dysregulation of both types of attention, establishing the important role of LPFC in supporting sustained periods of internally and externally directed attention.

Neural substrates of purely endogenous, self-regulatory control of attention

Stimulus-driven orienting of attention toward a novel, salient stimulus is a highly adaptive behavior. In an opposing vein, it is also crucial to endogenously redirect attention to other stimuli of behavioral significance if the attended stimulus was evaluated to be unimportant. This stimulus-driven orienting and subsequent reorienting of attention are known to be mediated by similar neural substrates. However, this might be because reorienting was triggered by a sensory transition exogenously capturing attention, such as an abrupt onset of a new stimulus. Here, we used fMRI to measure the human brain’s activity when attention captured by a salient distractor is endogenously reoriented toward the concurrent main task, without any exogenous shifting of attention. As results, the transient activity of the anterior insula (AI) signaled such endogenous reorienting, predicting behavioral performance. This finding points to the central role of the AI in purely endogenous, self-regulatory control of attention.

Fast Neural Dynamics of Proactive Cognitive Control in a Task-Switching Analogue of the Wisconsin Card Sorting Test

One common assumption has been that prefrontal executive control is mostly required for target detection (Posner and Petersen in Ann Rev Neurosci 13:25-42, 1990). Alternatively, cognitive control has also been related to anticipatory updating of task-set (contextual) information, a view that highlights proactive control processes. Frontoparietal cortical networks contribute to both proactive control and reactive target detection, although their fast dynamics are still largely unexplored. To examine this, we analyzed rapid magnetoencephalographic (MEG) source activations elicited by task cues and target cards in a task-cueing analogue of the Wisconsin Card Sorting Test. A single-task (color sorting) condition with equivalent perceptual and motor demands was used as a control. Our results revealed fast, transient and largely switch-specific MEG activations across frontoparietal and cingulo-opercular regions in anticipation of target cards, including (1) early (100-200 ms) cue-locked MEG signals at visual, temporo-parietal and prefrontal cortices of the right hemisphere (i.e., calcarine sulcus, precuneus, inferior frontal gyrus, anterior insula and supramarginal gyrus); and (2) later cue-locked MEG signals at the right anterior and posterior insula (200-300 ms) and the left temporo-parietal junction (300-500 ms). In all cases larger MEG signal intensity was observed in switch relative to repeat cueing conditions. Finally, behavioral restart costs and test scores of working memory capacity (forward digit span) correlated with cue-locked MEG activations at key nodes of the frontoparietal network. Together, our findings suggest that proactive cognitive control of task rule updating can be fast and transiently implemented within less than a second and in anticipation of target detection.

Collaborative roles of Temporoparietal Junction and Dorsolateral Prefrontal Cortex in Different Types of Behavioural Flexibility

Behavioural flexibility is essential for everyday life. This involves shifting attention between different perspectives. Previous studies suggest that flexibility is mainly subserved by the dorsolateral prefrontal cortex (DLPFC). However, although rarely emphasized, the temporoparietal junction (TPJ) is frequently recruited during flexible behaviour. A crucial question is whether TPJ plays a role in different types of flexibility, compared to its limited role in perceptual flexibility. We hypothesized that TPJ activity during diverse flexibility tasks plays a common role in stimulus-driven attention-shifting, thereby contributing to different types of flexibility, and thus the collaboration between DLPFC and TPJ might serve as a more appropriate mechanism than DLPFC alone. We used fMRI to measure DLPFC/TPJ activity recruited during moral flexibility, and examined its effect on other domains of flexibility (economic/perceptual). Here, we show the additional, yet crucial role of TPJ: a combined DLPFC/TPJ activity predicted flexibility, regardless of domain. Different types of flexibility might rely on more basic attention-shifting, which highlights the behavioural significance of alternatives.

Normal aging and Parkinson's disease are associated with the functional decline of distinct frontal-striatal circuits

Impaired ability to shift attention between stimuli (i.e. shifting attentional ‘set’) is a well-established part of the dysexecutive syndrome in Parkinson's Disease (PD), nevertheless cognitive and neural bases of this deficit remain unclear. In this study, an fMRI-optimised variant of a classic paradigm for assessing attentional control (Hampshire and Owen 2006) was used to contrast activity in dissociable executive circuits in early-stage PD patients and controls. The results demonstrated that the neural basis of the executive performance impairments in PD is accompanied by hypoactivation within the striatum, anterior cingulate cortex (vACC), and inferior frontal sulcus (IFS) regions. By contrast, in aging it is associated with hypoactivation of the anterior insula/inferior frontal operculum (AI/FO) and the pre-supplementary motor area (preSMA). Between group behavioural differences were also observed; whereas normally aging individuals exhibited routine-problem solving deficits, PD patients demonstrated more global task learning deficits. These findings concur with recent research demonstrating model-based reinforcement learning deficits in PD and provide evidence that the AI/FO and IFS circuits are differentially impacted by PD and normal aging.

Cognitive persistence: Development and validation of a novel measure from the Wisconsin Card Sorting Test

The Wisconsin Card Sorting Test (WCST) has long been used as a neuropsychological assessment of executive function abilities, in particular, cognitive flexibility or "set-shifting". Recent advances in scoring the task have helped to isolate specific WCST performance metrics that index set-shifting abilities and have improved our understanding of how prefrontal and parietal cortex contribute to set-shifting. We present evidence that the ability to overcome task difficulty to achieve a goal, or "cognitive persistence", is another important prefrontal function that is characterized by the WCST and that can be differentiated from efficient set-shifting. This novel measure of cognitive persistence was developed using the WCST-64 in an adult lifespan sample of 230 participants. The measure was validated using individual variation in cingulo-opercular cortex function in a sub-sample of older adults who had completed a challenging speech recognition in noise fMRI task. Specifically, older adults with higher cognitive persistence were more likely to demonstrate word recognition benefit from cingulo-opercular activity. The WCST-derived cognitive persistence measure can be used to disentangle neural processes involved in set-shifting from those involved in persistence.

Dorsal Anterior Cingulate, Medial Superior Frontal Cortex, and Anterior Insula Show Performance Reporting-Related Late Task Control Signals

The cingulo-opercular network (including the dorsal anterior cingulate and bilateral anterior insula) shows 3 distinct task-control signals across a wide variety of tasks, including trial-related signals that appear to come online at or near the end of the trial. Previous work suggests that there are separable responses in this network for errors and ambiguity, implicating multiple types of processing units within these regions. Using a unique paradigm, we directly show that these separable responses withhold activity to the end of the trial, in the service of reporting performance back into the task set. Participants performed a slow reveal task where images were presented behind a black mask which was gradually degraded, and they pressed a button when they could recognize the object that was being revealed. A behavioral pilot was used to identify ambiguous stimuli. We found interactive effects of accuracy and ambiguity, which suggests that these regions are computing and utilizing information, at one time, about both types of performance indices. Importantly, we showed a relationship between cingulo-opercular activity and behavioral performance, suggesting a role for these regions in performance reporting, per se. We discuss these results in the context of task control.

Theta-alpha EEG phase distributions in the frontal area for dissociation of visual and auditory working memory

Working memory (WM) is known to be associated with synchronization of the theta and alpha bands observed in electroencephalograms (EEGs). Although frontal-posterior global theta synchronization appears in modality-specific WM, local theta synchronization in frontal regions has been found in modality-independent WM. How frontal theta oscillations separately synchronize with task-relevant sensory brain areas remains an open question. Here, we focused on theta-alpha phase relationships in frontal areas using EEG, and then verified their functional roles with mathematical models. EEG data showed that the relationship between theta (6 Hz) and alpha (12 Hz) phases in the frontal areas was about 1:2 during both auditory and visual WM, and that the phase distributions between auditory and visual WM were different. Next, we used the differences in phase distributions to construct FitzHugh-Nagumo type mathematical models. The results replicated the modality-specific branching by orthogonally of the trigonometric functions for theta and alpha oscillations. Furthermore, mathematical and experimental results were consistent with regards to the phase relationships and amplitudes observed in frontal and sensory areas. These results indicate the important role that different phase distributions of theta and alpha oscillations have in modality-specific dissociation in the brain.

Are There Executive Dysfunction Subtypes Within ADHD?

OBJECTIVE

Children with ADHD have heterogeneous behavioral and neuropsychological profiles. The aim of this study was to examine the possible utility of executive function (EF) subtypes within ADHD.

METHOD

Participants were 357 children aged 6 through 13 with a diagnosis of ADHD. Children completed a brief laboratory battery measuring EF, including response inhibition, response variability, speed, and set-shifting. Children also completed standardized intelligence and achievement testing.

RESULTS

Two-way cluster analysis of EF profiles of children with ADHD produced a three-cluster solution, labeled poor inhibitory control, poor set-shifting/speed, and intact task performance. Clusters significantly differed in measures of intelligence, academic achievement, and other disruptive behavior and anxiety/mood symptoms.

CONCLUSION

These findings further support the idea that children with ADHD have heterogeneous EF profiles and suggest that the theory of ADHD should consider these individual differences in EF profiles within the ADHD diagnostic category.

Differential Contributions of Ventral and Dorsal Striatum to Early and Late Phases of Cognitive Set Reconfiguration

Flexible decision-making, a defining feature of human cognition, is typically thought of as a canonical pFC function. Recent work suggests that the striatum may participate as well; however, its role in this process is not well understood. We recorded activity of neurons in both the ventral (VS) and dorsal (DS) striatum while rhesus macaques performed a version of the Wisconsin Card Sorting Test, a classic test of flexibility. Our version of the task involved a trial-and-error phase before monkeys could identify the correct rule on each block. We observed changes in firing rate in both regions when monkeys switched rules. Specifically, VS neurons demonstrated switch-related activity early in the trial-and-error period when the rule needed to be updated, and a portion of these neurons signaled information about the switch context (i.e., whether the switch was intradimensional or extradimensional). Neurons in both VS and DS demonstrated switch-related activity at the end of the trial-and-error period, immediately before the rule was fully established and maintained, but these signals did not carry any information about switch context. We also observed associative learning signals (i.e., specific responses to options associated with rewards in the presentation period before choice) that followed the same pattern as switch signals (early in VS, later in DS). Taken together, these results endorse the idea that the striatum participates directly in cognitive set reconfiguration and suggest that single neurons in the striatum may contribute to a functional handoff from the VS to the DS during reconfiguration processes.

Plasticity of the Primate Prefrontal Cortex

Cortical plasticity refers to flexible and long-lasting changes in neuronal circuitry and information processing, which is caused by learning and experience. Although cortical plasticity can be observed in every cortex of the brain, the plasticity of the prefrontal cortex (PFC) is particularly important because the PFC is involved in various cognitive functions, and its plasticity could lead to adaptive changes in the use of other brain regions. Cortical plasticity occurs at several levels, from functional molecules to the organization of large areas of the brain. Here, the authors focus mainly on the development and remodeling of the functional and structural organization of the primate PFC. They discuss how the columnar modules of the PFC develop in the immature brain, how these modules form a “cognitive field” that is responsible for a specific cognitive function, how the cognitive field could be reorganized by training in the mature brain, and how monoaminergic systems contribute to these various levels of plasticity. They suggest that monoaminergic systems, especially the dopaminergic system, are involved in various levels of cortical plasticity, such as behavioral learning and learning-dependent cortical remodeling, thereby contributing to the reorganization of the cognitive field in the primate PFC. NEUROSCIENTIST 13(3):229—240, 2007.

Impact of anxiety on prefrontal cortex encoding of cognitive flexibility

Anxiety often is studied as a stand-alone construct in laboratory models. But in the context of coping with real-life anxiety, its negative impacts extend beyond aversive feelings and involve disruptions in ongoing goal-directed behaviors and cognitive functioning. Critical examples of cognitive constructs affected by anxiety are cognitive flexibility and decision making. In particular, anxiety impedes the ability to shift flexibly between strategies in response to changes in task demands, as well as the ability to maintain a strategy in the presence of distractors. The brain region most critically involved in behavioral flexibility is the prefrontal cortex (PFC), but little is known about how anxiety impacts PFC encoding of internal and external events that are critical for flexible behavior. Here we review animal and human neurophysiological and neuroimaging studies implicating PFC neural processing in anxiety-induced deficits in cognitive flexibility. We then suggest experimental and analytical approaches for future studies to gain a better mechanistic understanding of impaired cognitive inflexibility in anxiety and related disorders.

Demystifying cognitive flexibility: Implications for clinical and developmental neuroscience

Cognitive flexibility, the readiness with which one can selectively switch between mental processes to generate appropriate behavioral responses, develops in a protracted manner and is compromised in several prevalent neurodevelopmental disorders. It is unclear whether cognitive flexibility arises from neural substrates distinct from the executive control network (ECN) or from the interplay of nodes within this and other networks. Here we review neuroimaging studies of cognitive flexibility, focusing on set shifting and task switching. We propose that more consistent operationalization and study of cognitive flexibility is required in clinical and developmental neuroscience. We suggest that an important avenue for future research is the characterization of the relationship between neural flexibility and cognitive flexibility in typical and atypical development.

Neural Mechanisms of Credit Assignment in a Multicue Environment

In complex environments, many potential cues can guide a decision or be assigned responsibility for the outcome of the decision. We know little, however, about how humans and animals select relevant information sources that should guide behavior. We show that subjects solve this relevance selection and credit assignment problem by selecting one cue and its association with a particular outcome as the main focus of a hypothesis. To do this, we examined learning while using a task design that allowed us to estimate the focus of each subject's hypotheses on a trial-by-trial basis. When a prediction is confirmed by the outcome, then credit for the outcome is assigned to that cue rather than an alternative. Activity in medial frontal cortex is associated with the assignment of credit to the cue that is the main focus of the hypothesis. However, when the outcome disconfirms a prediction, the focus shifts between cues, and the credit for the outcome is assigned to an alternative cue. This process of reselection for credit assignment to an alternative cue is associated with lateral orbitofrontal cortex.

SIGNIFICANCE STATEMENT

Learners should infer which features of environments are predictive of significant events, such as rewards. This "credit assignment" problem is particularly challenging when any of several cues might be predictive. We show that human subjects solve the credit assignment problem by implicitly "hypothesizing" which cue is relevant for predicting subsequent outcomes, and then credit is assigned according to this hypothesis. This process is associated with a distinctive pattern of activity in a part of medial frontal cortex. By contrast, when unexpected outcomes occur, hypotheses are redirected toward alternative cues, and this process is associated with activity in lateral orbitofrontal cortex.

Functional connectivity at rest is sensitive to individual differences in executive function: A network analysis

Graph theory provides a means to understand the nature of network characteristics and connectivity between specific brain regions. Here it was used to investigate whether the network characteristics of the brain at rest are associated with three dimensions thought to underlie individual differences in executive function (EF)-common EF, shifting-specific EF, and updating-specific EF (Miyake and Friedman [2012]). To do so, both an a priori analysis focused mainly on select frontoparietal regions previously linked to individual differences in EF as well as a whole-brain analysis were performed. The findings indicated that individual differences in each of the three dimensions of EF were associated with specific patterns of resting-state connectivity both in a priori and other brain regions. More specifically, higher common EF was associated with greater integrative (i.e., more hublike) connectivity of cuneus and supplementary motor area but less integrative function of lateral frontal nodes and left temporal lobe nodes. Higher shifting-specific EF was associated with more hublike motor-related nodes and cingulo-opercular nodes. Higher updating-specific EF was associated with less hublike lateral and medial frontoparietal nodes. In general, these results suggested that higher ability in each of these three dimensions of EF was not solely characterized by the connectivity characteristics of frontoparietal regions. The pattern was complicated in that higher EF was associated with the connectivity profile of nodes outside of the traditional frontoparietal network, as well as with less hublike or centrality characteristics of some nodes within the frontoparietal network. Hum Brain Mapp 37:2959-2975, 2016. © 2016 Wiley Periodicals, Inc.

Cognitive Deficits Correlate with White Matter Deterioration in Spinocerebellar Ataxia Type 2

OBJECTIVES

The aim of this study was to explore the relationship between cognitive and white matter deterioration in a group of participants with spinocerebellar ataxia type 2 (SCA2).

METHODS

Fourteen genetically confirmed participants with SCA2 and 14 aged-matched controls participated in the study. Diffusion tensor imaging tract-based spatial statistics were performed to analyze structural white matter integrity. Significant group differences in the mean diffusivity were correlated with SCA2 cognitive deficits.

RESULTS

Our analysis revealed higher mean diffusivity in the SCA2 group in cerebellar white matter, medial lemniscus, and middle cerebellar peduncle, among other regions. Cognitive scores correlated with white matter mean diffusivity in the parahippocampal area, inferior frontal and supramarginal gyri and the stria terminalis.

CONCLUSIONS

Our findings show significant correlations between white matter microstructural damage in key areas affected in SCA2 and cognitive deficits. These findings result in a more comprehensive understanding of the effect of the neurodegenerative process in people with SCA2.

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.

Improving executive function using transcranial infrared laser stimulation

Transcranial infrared laser stimulation is a new non-invasive form of low-level light therapy that may have a wide range of neuropsychological applications. It entails using low-power and high-energy-density infrared light from lasers to increase metabolic energy. Preclinical work showed that this intervention can increase cortical metabolic energy, thereby improving frontal cortex-based memory function in rats. Barrett and Gonzalez-Lima (2013, Neuroscience, 230, 13) discovered that transcranial laser stimulation can enhance sustained attention and short-term memory in humans. We extend this line of work to executive function. Specifically, we ask whether transcranial laser stimulation enhances performance in the Wisconsin Card Sorting Task that is considered the gold standard of executive function and is compromised in normal ageing and a number of neuropsychological disorders. We used a laser of a specific wavelength (1,064 nm) that photostimulates cytochrome oxidase - the enzyme catalysing oxygen consumption for metabolic energy production. Increased cytochrome oxidase activity is considered the primary mechanism of action of this intervention. Participants who received laser treatment made fewer errors and showed improved set-shifting ability relative to placebo controls. These results suggest that transcranial laser stimulation improves executive function and may have exciting potential for treating or preventing deficits resulting from neuropsychological disorders or normal ageing.

Theta, mental flexibility, and post-traumatic stress disorder: connecting in the parietal cortex

Post-traumatic stress disorder (PTSD) is a mental health injury characterised by re-experiencing, avoidance, numbing and hyperarousal. Whilst the aetiology of the disorder is relatively well understood, there is debate about the prevalence of cognitive sequelae that manifest in PTSD. In particular, there are conflicting reports about deficits in executive function and mental flexibility. Even less is known about the neural changes that underlie such deficits. Here, we used magnetoencephalography to study differences in functional connectivity during a mental flexibility task in combat-related PTSD (all males, mean age = 37.4, n = 18) versus a military control (all males, mean age = 33.05, n = 19) group. We observed large-scale increases in theta connectivity in the PTSD group compared to controls. The PTSD group performance was compromised in the more attentionally-demanding task and this was characterised by 'late-stage' theta hyperconnectivity, concentrated in network connections involving right parietal cortex. Furthermore, we observed significant correlations with the connectivity strength in this region with a number of cognitive-behavioural outcomes, including measures of attention, depression and anxiety. These findings suggest atypical coordination of neural synchronisation in large scale networks contributes to deficits in mental flexibility for PTSD populations in timed, attentionally-demanding tasks, and this propensity toward network hyperconnectivity may play a more general role in the cognitive sequelae evident in this disorder.