The role of prefrontal cortex and posterior parietal cortex in task switching

Dissociating the neural substrates for inhibition and shifting in domain-general cognitive control

Inhibition and shifting are two key components of domain-general cognitive control. Numerous studies have investigated the neural substrates of both components, but it is still unclear whether the relevant brain regions are specifically involved in one specific component or commonly engaged in both components. Here, we addressed this question by using functional magnetic resonance imaging and a modified saccade paradigm that was effective to disentangle inhibition and shifting in one experiment. The results showed that both the middle frontal gyrus and left parietal lobe were involved in both components but the middle frontal gyrus was more active for the inhibition while the inferior parietal lobe was more active for the shifting processing. The outcome suggests that, although both regions are engaged in inhibition and shifting, each plays a dominant role in one component. These findings provide a further insight into the neural dissociation in inhibition and shifting, as well as a better explanation on the framework of unity and diversity from a neuropsychological viewpoint.

Beta and Theta Oscillations Differentially Support Free Versus Forced Control over Multiple-Target Search

Many important situations require human observers to simultaneously search for more than one object. Despite a long history of research into visual search, the behavioral and neural mechanisms associated with multiple-target search are poorly understood. Here we test the novel theory that the efficiency of looking for multiple targets critically depends on the mode of cognitive control the environment affords to the observer. We used an innovative combination of electroencephalogram (EEG) and eye tracking while participants searched for two targets, within two different contexts: either both targets were present in the search display and observers were free to prioritize either one of them, thus enabling proactive control over selection; or only one of the two targets would be present in each search display, which requires reactive control to reconfigure selection when the wrong target has been prioritized. During proactive control, both univariate and multivariate signals of beta-band (15-35 Hz) power suppression before display onset predicted switches between target selections. This signal originated over midfrontal and sensorimotor regions and has previously been associated with endogenous state changes. In contrast, imposed target selections requiring reactive control elicited prefrontal power enhancements in the delta/theta band (2-8 Hz), but only after display onset. This signal predicted individual differences in associated oculomotor switch costs, reflecting reactive reconfiguration of target selection. The results provide compelling evidence that multiple target representations are differentially prioritized during visual search, and for the first time reveal distinct neural mechanisms underlying proactive and reactive control over multiple-target search.SIGNIFICANCE STATEMENT Searching for more than one object in complex visual scenes can be detrimental for search performance. Although perhaps annoying in daily life, this can have severe consequences in professional settings such as medical and security screening. Previous research has not yet resolved whether multiple-target search involves changing priorities in what people attend to, and how such changes are controlled. We approached these questions by concurrently measuring cortical activity and eye movements using EEG and eye tracking while observers searched for multiple possible targets. Our findings provide the first unequivocal support for the existence of two modes of control during multiple-target search, which are expressed in qualitatively distinct time-frequency signatures of the EEG both before and after visual selection.

The strength of alpha and gamma oscillations predicts behavioral switch costs

Cognitive flexibility is often examined using task-switch paradigms, whereby individuals either switch between tasks or repeat the same task on successive trials. The behavioral costs of switching in terms of accuracy and reaction time are well-known, but the oscillatory dynamics underlying such costs are poorly understood. Herein, we examined 25 healthy adults who performed a task-switching paradigm during magnetoencephalography (MEG). All MEG data were transformed into the time-frequency domain and significant oscillatory responses were imaged separately per condition (i.e., switch, repeat) using a beamformer. To determine the impact of task-switching on the neural dynamics, the resulting images were examined using paired-samples t-tests. Whole-brain correlations were also computed using the switch-related difference images (switch - repeat) and the switch-related behavioral data (i.e., switch costs). Our key results indicated stronger decreases in alpha and beta activity, and greater increases in gamma activity in nodes of the cingulo-opercular and fronto-parietal networks during switch relative to repeat trials. In addition, behavioral switch costs were positively correlated with switch-related differences in right frontal and inferior parietal alpha activity, and negatively correlated with switch effects in anterior cingulate and right temporoparietal gamma activity. In other words, participants who had a greater decrease in alpha or increase in gamma in these respective regions had smaller behavioral switch costs, which suggests that these oscillations are critical to supporting cognitive flexibility. In sum, we provide novel data linking switch effects and gamma oscillations, and employed a whole-brain approach to directly link switch-related oscillatory differences with switch-related performance differences.

Anti-saccades predict cognitive functions in older adults and patients with Parkinson's disease

A major component of cognitive control is the ability to act flexibly in the environment by either behaving automatically or inhibiting an automatic behaviour. The interleaved pro/anti-saccade task measures cognitive control because the task relies on one's abilities to switch flexibly between pro and anti-saccades, and inhibit automatic saccades during anti-saccade trials. Decline in cognitive control occurs during aging or neurological illnesses such as Parkinson's disease (PD), and indicates decline in other cognitive abilities, such as memory. However, little is known about the relationship between cognitive control and other cognitive processes. Here we investigated whether anti-saccade performance can predict decision-making, visual memory, and pop-out and serial visual search performance. We tested 34 younger adults, 22 older adults, and 20 PD patients on four tasks: an interleaved pro/anti-saccade, a spatial visual memory, a decision-making and two types of visual search (pop-out and serial) tasks. Anti-saccade performance was a good predictor of decision-making and visual memory abilities for both older adults and PD patients, while it predicted visual search performance to a larger extent in PD patients. Our results thus demonstrate the suitability of the interleaved pro/anti-saccade task as a cognitive marker of cognitive control in aging and PD populations.

Functional MRI in Macaque Monkeys during Task Switching

Nonhuman primates have proven to be a valuable animal model for exploring neuronal mechanisms of cognitive control. One important aspect of executive control is the ability to switch from one task to another, and task-switching paradigms have often been used in human volunteers to uncover the underlying neuronal processes. To date, however, no study has investigated task-switching paradigms in nonhuman primates during functional magnetic resonance imaging (fMRI). We trained two rhesus macaques to switch between arm movement, eye movement, and passive fixation tasks during fMRI. Similar to results obtained in human volunteers, task switching elicits increased fMRI activations in prefrontal cortex, anterior cingulate cortex, orbitofrontal cortex, and caudate nucleus. Our results indicate that the macaque monkey is a reliable model with which to investigate higher-order cognitive functioning such as task switching. As such, these results can pave the way for a detailed investigation of the neural basis of complex human behavior.SIGNIFICANCE STATEMENT Task switching is an important aspect of cognitive control, and task-switching paradigms have often been used to investigate higher-order executive functioning in human volunteers. We used a task-switching paradigm in the nonhuman primate during fMRI and found increased activation mainly in prefrontal areas (46, 45, frontal eye field, and anterior cingulate), in orbitofrontal area 12, and in the caudate nucleus. These data fit surprisingly well with previous human imaging data, proving that the monkey is an excellent model to study task switching with high spatiotemporal resolution tools that are currently not applicable in humans. As such, our results pave the way for a detailed interrogation of regions performing similar executive functions in humans and monkeys.

Modulation of acute effects of delta-9-tetrahydrocannabinol on psychotomimetic effects, cognition and brain function by previous cannabis exposure

Cannabis use has been associated with psychosis and cognitive dysfunction. Some evidence suggests that the acute behavioral and neurocognitive effects of the main active ingredient in cannabis, (-)-trans-Δ9-tetrahydrocannabinol (∆9-THC), might be modulated by previous cannabis exposure. However, this has not been investigated either using a control group of non-users, or following abstinence in modest cannabis users, who represent the majority of recreational users. Twenty-four healthy men participated in a double-blind, randomized, placebo-controlled, repeated-measures, within-subject, ∆9-THC challenge study. Compared to non-users (N=12; <5 lifetime cannabis joints smoked), abstinent modest cannabis users (N=12; 24.5±9 lifetime cannabis joints smoked) showed worse performance and stronger right hemispheric activation during cognitive processing, independent of the acute challenge (all P≤0.047). Acute ∆9-THC administration produced transient anxiety and psychotomimetic symptoms (all P≤0.02), the latter being greater in non-users compared to users (P=0.040). Non-users under placebo (control group) activated specific brain areas to perform the tasks, while deactivating others. An opposite pattern was found under acute (∆9-THC challenge in non-users) as well as residual (cannabis users under placebo) effect of ∆9-THC. Under ∆9-THC, cannabis users showed brain activity patterns intermediate between those in non-users under placebo (control group), and non-users under ∆9-THC (acute effect) and cannabis users under placebo (residual effect). In non-users, the more severe the ∆9-THC-induced psychotomimetic symptoms and cognitive impairments, the more pronounced was the neurophysiological alteration (all P≤0.036). Previous modest cannabis use blunts the acute behavioral and neurophysiological effects of ∆9-THC, which are more marked in people who have never used cannabis.

Task set induces dynamic reallocation of resources in visual short-term memory

Successful interaction with the environment requires the ability to flexibly allocate resources to different locations in the visual field. Recent evidence suggests that visual short-term memory (VSTM) resources are distributed asymmetrically across the visual field based upon task demands. Here, we propose that context, rather than the stimulus itself, determines asymmetrical distribution of VSTM resources. To test whether context modulates the reallocation of resources to the right visual field, task set, defined by memory-load, was manipulated to influence visual short-term memory performance. Performance was measured for single-feature objects embedded within predominantly single- or two-feature memory blocks. Therefore, context was varied to determine whether task set directly predicts changes in visual field biases. In accord with the dynamic reallocation of resources hypothesis, task set, rather than aspects of the physical stimulus, drove improvements in performance in the right- visual field. Our results show, for the first time, that preparation for upcoming memory demands directly determines how resources are allocated across the visual field.

Effects of Naming Language and Switch Predictability on Switch Costs in Bilingual Language Production

Switch costs are defined as the phenomenon that bilinguals have worse performance in switch trials relative to non-switch trials. Bilinguals' naming language and switch predictability have been found to influence the magnitude of switch costs. However, how these two factors modulate switch costs in different phases (i.e., lemma activation and language selection) during language production remains unclear. Most previous studies using the language switching paradigm did not dissociate lemma activation from language selection, because the language cue was either presented simultaneously with or prior to a stimulus. Therefore, here we modified the language switching paradigm by presenting a digit stimulus prior to a visual cue. This allowed us to dissociate lemma activation from language selection, and thus we were able to investigate the mechanisms underlying the effects of naming language and switch predictability on switch costs during the two different phases in language production. Unbalanced Indonesian-Chinese bilinguals were required to name digits in either their L1 (Indonesian) or L2 (Chinese), and their reaction times and electrophysiological responses were recorded. The behavioral results showed the effects of switch predictability on switch costs, with responses in switch trials being slower than those in non-switch trials in the low switch predictability condition, while there was no significant difference in response times between switch trials and non-switch trials in the high switch predictability condition. The event-related potential results showed that neither naming language nor switch predictability affected switch costs during the lemma activation phase, but both did so during the language selection phase, particularly at the language task schema competition stage. The results imply that naming language and switch predictability affect switch costs mainly during the language task schema competition stage.

Contrasting effects of pre-training on acquisition of operant and radial arm maze tasks in rats

Performing multiple tasks either simultaneously, in rapid alternation or in succession, is routine in daily life. Further, testing rodents in a battery of tests is common both in drug discovery and behavioral phenotyping research. However, learning of new tasks can be influenced by prior experience(s). There has been some research on 'switching cost' involved in the transition from one behavior to another. However, there has been no specific assessment of the effect of learning an operant paradigm on performance in a spatial memory task and vice versa. Accordingly, we evaluated task switching between two forms of learning paradigms, operant conditioning and radial arm maze (RAM) tasks. In experiment 1, rats were trained for operant conditioning with food reward followed by a partially baited RAM task. In experiment 2, rats were trained first on a RAM task followed by operant learning. Pre-training on the operant task, impaired the acquisition of the RAM. On the contrary, pre-training on the RAM enhanced operant performance. Our study reveals significant effects of the test order on task-switching in rats. This knowledge can be useful when framing test sequences in test batteries for drug discovery research and screening genetically modified mice.

Only-child and non-only-child exhibit differences in creativity and agreeableness: evidence from behavioral and anatomical structural studies

Different family composition and size inevitably make only-children different from non-only-children. Previous studies have focused on the differences in behaviors, such as cognitive function and personality traits, between the only-child and the non-only-child. However, there are few studies that have focused on the topic of whether different family environments influence children's brain structural development and whether behavior differentially has its neural basis between only-child and non-only-child status. Thus, in the present study, we investigated the differences in cognition (e.g., intelligence and creativity) and personality and the anatomical structural differences of gray matter volume (GMV) using voxel-based morphometry (VBM) between only-children and non-only-children. The behavioral results revealed that only-children exhibited higher flexibility scores (a dimension of creativity) and lower agreeableness scores (a dimension of personality traits) than non-only-children. Most importantly, the GMV results revealed that there were significant differences in the GMV between only-children and non-only-children that occurred mainly in the brain regions of the supramarginal gyrus, which was positively correlated with flexibility scores; the medial prefrontal cortex (mPFC), which was positively correlated with agreeableness scores; and the parahippocampal gyrus. These findings may suggest that family environment (i.e., only-child vs. non-only-child), may play important roles in the development of the behavior and brain structure of individuals.

On pacing trials while scanning brain hemodynamics: The case of the SNARC effect

Experimental designs used to describe psychological effects on overt human behavior are seldom suited to localize their corresponding neural substrates based on the analysis of stimulus-evoked brain hemodynamic responses. This is because stimuli in behavioral studies are usually separated by intertrial intervals (ITIs) in the order of 1 second or so following a behavioral response, which is notoriously too brief a time to detect a corresponding hemodynamic response. In fact, a solution commonly adopted in neuroimaging studies is to prolong the ITI up to several seconds. In doing so, the consequences of ITI variations between behavioral and neuroimaging design variants are either benignly neglected or explicitly assumed to be negligible. Here, we provide a systematic investigation of the consequence of manipulating ITI in a design optimized to study a well-established and highly replicable psychological phenomenon-the spatial numerical association of response codes (SNARC). The present exploration encompassed standard estimates of the SNARC effect (i.e., on reaction times and accuracy), estimates of ITI effects on the emotional state of participants before and after performing the SNARC task, as well as the degree of perceived task difficulty. The results showed that, in striking contrast to the common wisdom about the nil role of ITI, the substantial number of parametric differences observed between the two ITI conditions suggests that ITI plays a critical role in shaping the meaning of hemodynamic correlate of a psychological, at least the SNARC, effect.

Binge drinking differentially affects cortical and subcortical microstructure

Young adult binge drinkers represent a model for endophenotypic risk factors for alcohol misuse and early exposure to repeated binge cycles. Chronic or harmful alcohol use leads to neurochemical, structural and morphological neuroplastic changes, particularly in regions associated with reward processing and motivation. We investigated neural microstructure in 28 binge drinkers compared with 38 matched healthy controls. We used a recently developed diffusion magnetic resonance imaging acquisition and analysis, which uses three‐compartment modelling (of intracellular, extracellular and cerebrospinal fluid) to determine brain tissue microstructure features including neurite density and orientation dispersion index (ODI). Binge drinkers had reduced ODI, a proxy of neurite complexity, in frontal cortical grey matter and increased ODI in parietal grey matter. Neurite density was higher in cortical white matter in adjacent regions of lower ODI in binge drinkers. Furthermore, binge drinkers had higher ventral striatal grey matter ODI that was positively correlated with binge score. Healthy volunteers showed no such relationships. We demonstrate disturbed dendritic complexity of higher‐order prefrontal and parietal regions, along with higher dendritic complexity of a subcortical region known to mediate reward‐related motivation. The findings illustrate novel microstructural abnormalities that may reflect an infnce of alcohol bingeing on critical neurodevelopmental processes in an at‐risk young adult group.

A Combination of Essential Fatty Acids, Panax Ginseng Extract, and Green Tea Catechins Modifies Brain fMRI Signals in Healthy Older Adults

OBJECTIVES

To assess the effects of a combination of omega 3 essential fatty acids, green tea catechins, and ginsenosides on cognition and brain functioning in healthy older adults.

DESIGN

Double-blind, placebo-controlled, crossover design randomized controlled trial with 26-day intervention phases and a 30-day washout period.

SETTING

The Institute for Dementia Research and Prevention at the Pennington Biomedical Research Center.

PARTICIPANTS

Ten independently-living, cognitively-healthy older adults (mean age: 67.3 + 2.01 years).

INTERVENTION

Daily consumption of an investigational product (trade name "Cerbella TM") consisting of an emulsified liquid combination of standardized fish oil, panax ginseng extract, and green tea catechins in a flavored base of lecithin phospholipids optimized to maximize bioavailability of the active ingredients.

MEASUREMENTS

Before and after supplementation with the investigational product or placebo, participants completed cognitive tests including the Mini Mental State Exam (MMSE), Stroop test, Digit Symbol Substitution Test (DSST), and Immediate and Delayed Recall tests, as well as functional magnetic resonance imaging (fMRI) during a standard cognitive task switching paradigm.

RESULTS

Performance on the MMSE, Stroop test, and DSST increased significantly over one month of supplementation with the investigational product (one-sample t tests, p<.05) although differences between these changes and corresponding changes during supplementation with placebo were not significant (two-sample t tests, p>.05). During supplementation with the investigational product, brain activation during task performance increased significantly more than during supplementation with placebo in brain regions known to be activated by this task (anterior and posterior cingulate cortex). Functional connectivity during task execution between task regions (middle frontal gyrus and anterior cingulate cortex) increased significantly during supplementation with the investigational product, relative to placebo. Functional connectivity during rest between task regions (precentral gyrus and middle frontal gyrus) and default mode network regions (medial frontal gyrus and precuneus) decreased during supplementation with the investigational product relative to placebo, suggesting greater segregation of task and rest related brain activity.

CONCLUSION

One-month supplementation with a combination of omega 3 essential fatty acids, green tea catechins, and ginsenosides was associated with suggestive changes in cognitive functioning as well as modification of brain activation and brain functional connectivity in cognitively healthy older adults.

The influence of short-term language-switching training on the plasticity of the cognitive control mechanism in bilingual word production

This study examined the effect of short-term language-switching training on the cognitive control mechanism in bilingual word production. In two experiments, two groups of relatively proficient but unbalanced Chinese–English bilinguals performed a cued picture-naming task, in which they switched between their two languages. On two consecutive days, the participants took part in four sessions. The same procedure was employed on 2 days in Experiment 1, whereas the cue-language mapping was reversed on Day 2 in Experiment 2. In both experiments, picture naming in the dominant language (L1, Chinese) was slower than that in the weaker second language (L2, English) in all sessions. In addition, the reversed language dominance effect was enhanced with training, suggesting that training proactively increases the amount of inhibition of the dominant L1 at the global level. Furthermore, switching costs in the L1 were reduced with training in Experiment 1, but not in Experiment 2. These results indicate that language-switching training improves the efficiency of reactively exerting inhibitory control over the dominant L1 at the local level. However, when a cue matches with different target languages, the effect of training is absent at the local level. These findings reveal the plasticity and complexity of the cognitive control mechanism as a function of bilingual experience, particularly in language switching.

When global rule reversal meets local task switching: The neural mechanisms of coordinated behavioral adaptation to instructed multi-level demand changes

Cognitive flexibility is essential to cope with changing task demands and often it is necessary to adapt to combined changes in a coordinated manner. The present fMRI study examined how the brain implements such multi-level adaptation processes. Specifically, on a "local," hierarchically lower level, switching between two tasks was required across trials while the rules of each task remained unchanged for blocks of trials. On a "global" level regarding blocks of twelve trials, the task rules could reverse or remain the same. The current task was cued at the start of each trial while the current task rules were instructed before the start of a new block. We found that partly overlapping and partly segregated neural networks play different roles when coping with the combination of global rule reversal and local task switching. The fronto-parietal control network (FPN) supported the encoding of reversed rules at the time of explicit rule instruction. The same regions subsequently supported local task switching processes during actual implementation trials, irrespective of rule reversal condition. By contrast, a cortico-striatal network (CSN) including supplementary motor area and putamen was increasingly engaged across implementation trials and more so for rule reversal than for nonreversal blocks, irrespective of task switching condition. Together, these findings suggest that the brain accomplishes the coordinated adaptation to multi-level demand changes by distributing processing resources either across time (FPN for reversed rule encoding and later for task switching) or across regions (CSN for reversed rule implementation and FPN for concurrent task switching).

White matter integrity between left basal ganglia and left prefrontal cortex is compromised in gambling disorder

Pathological gambling (PG) is a behavioral addiction characterized by an inability to stop gambling despite the negative consequences, which may be mediated by cognitive flexibility deficits. Indeed, impaired cognitive flexibility has previously been linked to PG and also to reduced integrity of white matter connections between the basal ganglia and the prefrontal cortex. It remains unclear, however, how white matter integrity problems relate to cognitive inflexibility seen in PG. We used a cognitive switch paradigm during functional magnetic resonance imaging in pathological gamblers (PGs; n = 26) and healthy controls (HCs; n = 26). Cognitive flexibility performance was measured behaviorally by accuracy and reaction time on the switch task, while brain activity was measured in terms of blood oxygen level-dependent responses. We also used diffusion tensor imaging on a subset of data (PGs = 21; HCs = 21) in combination with tract-based spatial statistics and probabilistic fiber tracking to assess white matter integrity between the basal ganglia and the dorsolateral prefrontal cortex. Although there were no significant group differences in either task performance, related neural activity or tract-based spatial statistics, PGs did show decreased white matter integrity between the left basal ganglia and prefrontal cortex. Our results complement and expand similar findings from a previous study in alcohol-dependent patients. Although we found no association between white matter integrity and task performance here, decreased white matter connections may contribute to a diminished ability to recruit prefrontal networks needed for regulating behavior in PG. Hence, our findings could resonate an underlying risk factor for PG, and we speculate that these findings may extend to addiction in general.

Dynamic Trial-by-Trial Recoding of Task-Set Representations in the Frontoparietal Cortex Mediates Behavioral Flexibility

Cognitive flexibility forms the core of the extraordinary ability of humans to adapt, but the precise neural mechanisms underlying our ability to nimbly shift between task sets remain poorly understood. Recent functional magnetic resonance imaging (fMRI) studies employing multivoxel pattern analysis (MVPA) have shown that a currently relevant task set can be decoded from activity patterns in the frontoparietal cortex, but whether these regions support the dynamic transformation of task sets from trial to trial is not clear. Here, we combined a cued task-switching protocol with human (both sexes) fMRI, and harnessed representational similarity analysis (RSA) to facilitate a novel assessment of trial-by-trial changes in neural task-set representations. We first used MVPA to define task-sensitive frontoparietal and visual regions and found that neural task-set representations on switch trials are less stably encoded than on repeat trials. We then exploited RSA to show that the neural representational pattern dissimilarity across consecutive trials is greater for switch trials than for repeat trials, and that the degree of this pattern dissimilarity predicts behavior. Moreover, the overall neural pattern of representational dissimilarities followed from the assumption that repeating sets, compared with switching sets, results in stronger neural task representations. Finally, when moving from cue to target phase within a trial, pattern dissimilarities tracked the transformation from previous-trial task representations to the currently relevant set. These results provide neural evidence for the longstanding assumptions of an effortful task-set reconfiguration process hampered by task-set inertia, and they demonstrate that frontoparietal and stimulus processing regions support "dynamic adaptive coding," flexibly representing changing task sets in a trial-by-trial fashion.SIGNIFICANCE STATEMENT Humans can fluently switch between different tasks, reflecting an ability to dynamically configure "task sets," rule representations that link stimuli to appropriate responses. Recent studies show that neural signals in frontal and parietal brain regions can tell us which of two tasks a person is currently performing. However, it is not known whether these regions are also involved in dynamically reconfiguring task-set representations when switching between tasks. Here we measured human brain activity during task switching and tracked the similarity of neural task-set representations from trial to trial. We show that frontal and parietal brain regions flexibly recode changing task sets in a trial-by-trial fashion, and that task-set similarity over consecutive trials predicts behavior.

Neural correlates for task switching in the macaque superior colliculus

Successful task switching requires a network of brain areas to select, maintain, implement, and execute the appropriate task. Although frontoparietal brain areas are thought to play a critical role in task switching by selecting and encoding task rules and exerting top-down control, how brain areas closer to the execution of tasks participate in task switching is unclear. The superior colliculus (SC) integrates information from various brain areas to generate saccades and is likely influenced by task switching. Here, we investigated switch costs in nonhuman primates and their neural correlates in the activity of SC saccade-related neurons in monkeys performing cued, randomly interleaved pro- and anti-saccade trials. We predicted that behavioral switch costs would be associated with differential modulations of SC activity in trials on which the task was switched vs. repeated, with activity on the current trial resembling that associated with the task set of the previous trial when a switch occurred. We observed both error rate and reaction time switch costs and changes in the discharge rate and timing of activity in SC neurons between switch and repeat trials. These changes were present later in the task only after fixation on the cue stimuli but before saccade onset. These results further establish switch costs in macaque monkeys and suggest that SC activity is modulated by task-switching processes in a manner inconsistent with the concept of task set inertia.NEW & NOTEWORTHY Task-switching behavior and superior colliculus (SC) activity were investigated in nonhuman primates performing randomly interleaved pro- and anti-saccade tasks. Here, we report error rate and reaction time switch costs in macaque monkeys and associated differences in stimulus-related activity of saccade-related neurons in the SC. These results provide a neural correlate for task switching and suggest that the SC is modulated by task-switching processes and may reflect the completion of task set reconfiguration.

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.

Switch-Independent Task Representations in Frontal and Parietal Cortex

Alternating between two tasks is effortful and impairs performance. Previous fMRI studies have found increased activity in frontoparietal cortex when task switching is required. One possibility is that the additional control demands for switch trials are met by strengthening task representations in the human brain. Alternatively, on switch trials, the residual representation of the previous task might impede the buildup of a neural task representation. This would predict weaker task representations on switch trials, thus also explaining the performance costs. To test this, male and female participants were cued to perform one of two similar tasks, with the task being repeated or switched between successive trials. Multivoxel pattern analysis was used to test which regions encode the tasks and whether this encoding differs between switch and repeat trials. As expected, we found information about task representations in frontal and parietal cortex, but there was no difference in the decoding accuracy of task-related information between switch and repeat trials. Using cross-classification, we found that the frontoparietal cortex encodes tasks using a generalizable spatial pattern in switch and repeat trials. Therefore, task representations in frontal and parietal cortex are largely switch independent. We found no evidence that neural information about task representations in these regions can explain behavioral costs usually associated with task switching.SIGNIFICANCE STATEMENT Alternating between two tasks is effortful and slows down performance. One possible explanation is that the representations in the human brain need time to build up and are thus weaker on switch trials, explaining performance costs. Alternatively, task representations might even be enhanced to overcome the previous task. Here, we used a combination of fMRI and a brain classifier to test whether the additional control demands under switching conditions lead to an increased or decreased strength of task representations in frontoparietal brain regions. We found that task representations are not modulated significantly by switching processes and generalize across switching conditions. Therefore, task representations in the human brain cannot account for the performance costs associated with alternating between tasks.

Reward Draws the Eye, Uncertainty Holds the Eye: Associative Learning Modulates Distractor Interference in Visual Search

Stimuli in our sensory environment differ with respect to their physical salience but moreover may acquire motivational salience by association with reward. If we repeatedly observed that reward is available in the context of a particular cue but absent in the context of another cue the former typically attracts more attention than the latter. However, we also may encounter cues uncorrelated with reward. A cue with 50% reward contingency may induce an average reward expectancy but at the same time induces high reward uncertainty. In the current experiment we examined how both values, reward expectancy and uncertainty, affected overt attention. Two different colors were established as predictive cues for low reward and high reward respectively. A third color was followed by high reward on 50% of the trials and thus induced uncertainty. Colors then were introduced as distractors during search for a shape target, and we examined the relative potential of the color distractors to capture and hold the first fixation. We observed that capture frequency corresponded to reward expectancy while capture duration corresponded to uncertainty. The results may suggest that within trial reward expectancy is represented at an earlier time window than uncertainty.

Executive functioning in relapsing-remitting multiple sclerosis patients without cognitive impairment: A task-switching protocol

Background:

Cognitive dysfunction affects 40%–65% of multiple sclerosis (MS) patients, most often affecting information processing speed and working memory, mediated by the pre-frontal cortex (PFC).

Objective:

Our study aimed to investigate PFC functioning through a task-switching protocol in relapsing-remitting multiple sclerosis (RRMS) patients without cognitive impairment.

Methods:

A total of 24 RRMS patients and 25 controls were enrolled. Two different tasks were performed in rapid and random succession, so that the task was either changed from one trial to the next one (switch trials) or repeated (repetition trials). Switch trials are usually slower than repetitions, causing a so-called switch cost (SC).

Results:

Patients had worse performance than controls only in the switch trials, as indicated by increased SC and reaction times. Moreover, patients showed a reduced ability to reconfigure the task-set for the execution of a new task and to disengage from the previous one.

Conclusion:

Our results showed a primary deficit in executive control processes involved in the task-switching performance in RRMS patients without cognitive impairment. This deficit may depend on the functional impairment of the PFC, which is essential to adjust behaviour rapidly and flexibly in response to environmental changes, representing one of the most sophisticated human abilities.

Are individuals with higher psychopathic traits better learners at lying? Behavioural and neural evidence

High psychopathy is characterized by untruthfulness and manipulativeness. However, existing evidence on higher propensity or capacity to lie among non-incarcerated high-psychopathic individuals is equivocal. Of particular importance, no research has investigated whether greater psychopathic tendency is associated with better 'trainability' of lying. An understanding of whether the neurobehavioral processes of lying are modifiable through practice offers significant theoretical and practical implications. By employing a longitudinal design involving university students with varying degrees of psychopathic traits, we successfully demonstrate that the performance speed of lying about face familiarity significantly improved following two sessions of practice, which occurred only among those with higher, but not lower, levels of psychopathic traits. Furthermore, this behavioural improvement associated with higher psychopathic tendency was predicted by a reduction in lying-related neural signals and by functional connectivity changes in the frontoparietal and cerebellum networks. Our findings provide novel and pivotal evidence suggesting that psychopathic traits are the key modulating factors of the plasticity of both behavioural and neural processes underpinning lying. These findings broadly support conceptualization of high-functioning individuals with higher psychopathic traits as having preserved, or arguably superior, functioning in neural networks implicated in cognitive executive processing, but deficiencies in affective neural processes, from a neuroplasticity perspective.

A Biologically Plausible Action Selection System for Cognitive Architectures: Implications of Basal Ganglia Anatomy for Learning and Decision-Making Models

Several attempts have been made previously to provide a biological grounding for cognitive architectures by relating their components to the computations of specific brain circuits. Often, the architecture's action selection system is identified with the basal ganglia. However, this identification overlooks one of the most important features of the basal ganglia-the existence of a direct and an indirect pathway that compete against each other. This characteristic has important consequences in decision-making tasks, which are brought to light by Parkinson's disease as well as genetic differences in dopamine receptors. This paper shows that a standard model of action selection in a cognitive architecture (ACT-R) cannot replicate any of these findings, details an alternative solution that reconciles action selection in the architecture with the physiology of the basal ganglia, and extends the domain of application of cognitive architectures. The implication of this solution for other architectures and existing models are discussed.

Frontal assessment battery and frontal atrophy in amyotrophic lateral sclerosis

OBJECTIVES

To determine the potential utility of the frontal assessment battery (FAB) in assessing cognitive impairments in amyotrophic lateral sclerosis (ALS), we investigated the association between the FAB score and regional gray matter volume, and ascertained whether the regional brain alterations related to cognitive impairments occur in relatively mild stage of ALS.

MATERIALS AND METHODS

Twenty-four ALS patients with a Mini-Mental State Examination score of >23, a normal score on the Self-Rating Depression Scale, little or no disturbance in speech and handling utensils on the ALS Functional Rating Scale (ALSFRS), and normal measures on respiratory tests (respiratory function test and arterial blood gas analysis), and two age-matched normal control groups (one for FAB assessment and the other for brain morphometry) underwent FAB testing and structural magnetic resonance imaging. We applied voxel-based morphometry to investigate the relationship between the FAB score and regional brain alteration, and assessed the relationship between the altered regional brain volume and ALSFRS or respiratory tests.

RESULTS

Frontal assessment battery scores were significantly lower in ALS patients than in normal controls. Volume reduction in the right orbitofrontal gyrus in ALS was correlated with a lower FAB score. There was no correlation between the right orbitofrontal gyrus volume and ALSFRS or respiratory tests.

CONCLUSIONS

The results suggest that the FAB is an adequate tool for detecting cognitive impairments related to frontal lobe pathology in the relatively mild stage of ALS, independent of physical dysfunctions.

Theta and high-beta networks for feedback processing: a simultaneous EEG-fMRI study in healthy male subjects

The reward system is important in assessing outcomes to guide behavior. To achieve these purposes, its core components interact with several brain areas involved in cognitive and emotional processing. A key mechanism suggested to subserve these interactions is oscillatory activity, with a prominent role of theta and high-beta oscillations. The present study used single-trial coupling of simultaneously recorded electroencephalography and functional magnetic resonance imaging data to investigate networks associated with oscillatory responses to feedback during a two-choice gambling task in healthy male participants (n=19). Differential associations of theta and high-beta oscillations with non-overlapping brain networks were observed: Increase of high-beta power in response to positive feedback was associated with activations in a largely subcortical network encompassing core areas of the reward network. In contrast, theta-band power increase upon loss was associated with activations in a frontoparietal network that included the anterior cingulate cortex. Trait impulsivity correlated significantly with activations in areas of the theta-associated network. Our results suggest that positive and negative feedback is processed by separate brain networks associated with different cognitive functions. Communication within these networks is mediated by oscillations of different frequency, possibly reflecting different modes of dopaminergic signaling.

Spontaneous eye blink rate (EBR) predicts poor performance in high-stakes situations

Although the existence of 'choking under pressure' is well-supported by research, its biological underpinnings are less clear. In this research, we examined two individual difference variables that may predict whether people are likely to perform poorly in high-incentive conditions: baseline eye blink rate (EBR; reflecting dopamine system functioning) and baseline anterior hemispheric asymmetry (an indicator of goal-directed vs. stimulus driven processing). Participants conducted a switch task under control vs. incentive conditions. People low in EBR were generally capable of improving their performance when incentives were at stake, whereas people high in EBR were not. Hemispheric asymmetry did not predict performance. These findings are consistent with the idea that suboptimal performance in high-stakes conditions may stem from the neuromodulatory effects of dopamine.

Shifting of attentional set is inadequate in severe burnout: Evidence from an event-related potential study

Individuals with prolonged occupational stress often report difficulties in concentration. Work tasks often require the ability to switch back and forth between different contexts. Here, we studied the association between job burnout and task switching by recording event-related potentials (ERPs) time-locked to stimulus onset during a task with simultaneous cue-target presentation and unpredictable switches in the task. Participants were currently working people with severe, mild, or no burnout symptoms. In all groups, task performance was substantially slower immediately after task switch than during task repetition. However, the error rates were higher in the severe burnout group than in the mild burnout and control groups. Electrophysiological data revealed an increased parietal P3 response for the switch trials relative to repetition trials. Notably, the response was smaller in amplitude in the severe burnout group than in the other groups. The results suggest that severe burnout is associated with inadequate processing when rapid shifting of attention between tasks is required resulting in less accurate performance.

Does Interhemispheric Competition Mediate Motion-Induced Blindness? A Transcranial Magnetic Stimulation Study

Motion-induced blindness (MIB) is a phenomenon, perhaps related to perceptual rivalry, where stationary targets disappear and reappear in a cyclic mode when viewed against a background (mask) of coherent, apparent 3-D motion. Since MIB has recently been shown to share similar temporal properties with binocular rivalry, we probed the appearance–disappearance cycle of MIB using unilateral, single-pulse transcranial magnetic stimulation (TMS)—a manipulation that has previously been shown to influence binocular rivalry. Effects were seen for both hemispheres when the timing of TMS was determined prospectively on the basis of a given subject's appearance–disappearance cycle, so that it occurred on average around 300 ms before the time of perceptual switch. Magnetic stimulation of either hemisphere shortened the time to switch from appearance to disappearance and vice versa. However, TMS of left posterior parietal cortex more selectively shortened the disappearance time of the targets if delivered in phase with the disappearance cycle, but lengthened it if TMS was delivered in the appearance phase after the perceptual switch. Opposite effects were seen in the right hemisphere, although less marked than the left-hemisphere effects. As well as sharing temporal characteristics with binocular rivalry, MIB therefore seems to share a similar underlying mechanism of interhemispheric modulation. Interhemispheric switching may thus provide a common temporal framework for uniting the diverse, multilevel phenomena of perceptual rivalry.

Aging Affects Dopaminergic Neural Mechanisms of Cognitive Flexibility

Aging is accompanied by profound changes in the brain's dopamine system that affect cognitive function. Evidence of powerful individual differences in cognitive aging has sharpened focus on identifying biological factors underlying relative preservation versus vulnerability to decline. Dopamine represents a key target in these efforts. Alterations of dopamine receptors and dopamine synthesis are seen in aging, with receptors generally showing reduction and synthesis demonstrating increases. Using the PET tracer 6-[¹⁸F]fluoro-l-m-tyrosine, we found strong support for upregulated striatal dopamine synthesis capacity in healthy older adult humans free of amyloid pathology, relative to young people. We next used fMRI to define the functional impact of elevated synthesis capacity on cognitive flexibility, a core component of executive function. We found clear evidence in young adults that low levels of synthesis capacity were suboptimal, associated with diminished cognitive flexibility and altered frontoparietal activation relative to young adults with highest synthesis values. Critically, these relationships between dopamine, performance, and activation were transformed in older adults with higher synthesis capacity. Variability in synthesis capacity was related to intrinsic frontoparietal functional connectivity across groups, suggesting that striatal dopamine synthesis influences the tuning of networks underlying cognitive flexibility. Together, these findings define striatal dopamine's association with cognitive flexibility and its neural underpinnings in young adults, and reveal the alteration in dopamine-related neural processes in aging.

SIGNIFICANCE STATEMENT

Few studies have combined measurement of brain dopamine with examination of the neural basis of cognition in youth and aging to delineate the underlying mechanisms of these associations. Combining in vivo PET imaging of dopamine synthesis capacity, fMRI, and a sensitive measure of cognitive flexibility, we reveal three core findings. First, we find evidence supporting older adults' capacity to upregulate dopamine synthesis. Second, we define relationships between dopamine, cognition, and frontoparietal activity in young adults indicating high levels of synthesis capacity are optimal. Third, we demonstrate alteration of these relationships in older adults, suggesting neurochemical modulation of cognitive flexibility changes with age.

A neural mechanism of cognitive control for resolving conflict between abstract task rules

Conflict between multiple sensory stimuli or potential motor responses is thought to be resolved via bias signals from prefrontal cortex (PFC). However, population codes in the PFC also represent abstract information, such as task rules. How is conflict between active abstract representations resolved? We used functional neuroimaging to investigate the mechanism responsible for resolving conflict between abstract representations of task rules. Participants performed two different tasks based on a cue. We manipulated the degree of conflict at the task-rule level by training participants to associate the color and shape dimensions of the cue with either the same task rule (congruent cues) or different ones (incongruent cues). Phonological and semantic tasks were used in which performance depended on learned, abstract representations of information, rather than sensory features of the target stimulus or on any habituated stimulus-response associations. In addition, these tasks activate distinct regions that allowed us to measure magnitude of conflict between tasks. We found that incongruent cues were associated with increased activity in several cognitive control areas, including the inferior frontal gyrus, inferior parietal lobule, insula, and subcortical regions. Conflict between abstract representations appears to be resolved by rule-specific activity in the inferior frontal gyrus that is correlated with enhanced activity related to the relevant information. Furthermore, multi-voxel pattern analysis of the activity in the inferior frontal gyrus was shown to carry information about both the currently relevant rule (semantic/phonological) and the currently relevant cue context (color/shape). Similar to models of attentional selection of conflicting sensory or motor representations, the current findings indicate part of the frontal cortex provides a bias signal, representing task rules, that enhances task-relevant information. However, the frontal cortex can also be the target of these bias signals in order to enhance abstract representations that are independent of particular stimuli or motor responses.

Symbolic and Sub-Symbolic Representations in Computational Models of Human Cognition

The debate over symbolic versus sub-symbolic representations of human cognition has been continuing for thirty years, with little indication of a resolution. The argument is this: Does the human cognitive system use symbols as a representation of knowledge, and does it process symbols and their respective constituents? Or does the human cognitive system use a distributed representation of knowledge, and is it somehow capable of processing this distributed representation of knowledge in a complex and meaningful way? This paper argues for an integrated symbolic and sub-symbolic approach to the representation of cognition. The lines of reasoning used as evidence to bolster this argument for an integrated approach are the cognitive architecture the Adaptive Character of Thought-Rational (ACT-R), and biology, where it is argued that symbolic and sub-symbolic representations of cognition are part of an intellectual continuum, with sub-symbolic representations at the low end and symbolic representations at the higher end.

Functional brain and age-related changes associated with congruency in task switching

Alternating between completing two simple tasks, as opposed to completing only one task, has been shown to produce costs to performance and changes to neural patterns of activity, effects which are augmented in old age. Cognitive conflict may arise from factors other than switching tasks, however. Sensorimotor congruency (whether stimulus-response mappings are the same or different for the two tasks) has been shown to behaviorally moderate switch costs in older, but not younger adults. In the current study, we used fMRI to investigate the neurobiological mechanisms of response-conflict congruency effects within a task switching paradigm in older (N=75) and younger (N=62) adults. Behaviorally, incongruency moderated age-related differences in switch costs. Neurally, switch costs were associated with greater activation in the dorsal attention network for older relative to younger adults. We also found that older adults recruited an additional set of brain areas in the ventral attention network to a greater extent than did younger adults to resolve congruency-related response-conflict. These results suggest both a network and an age-based dissociation between congruency and switch costs in task switching.

Planning my actions to accommodate yours: joint action development during early childhood

The planning and adjusting of one's actions in relation to an action partner is fundamental to smooth joint action. During their first years of life, children gradually become more engaged in joint actions. Here, we investigated whether and at what age children take their partner into account in their action plans to accommodate the other's actions. We focused on children's proactive planning (without prior experience) and flexible adjustment of action plans over time. In a behavioural study, we tested 96 children from four age groups (2½, 3, 3½ and 5 years) in a joint cup-stacking task. Children passed cups to their partner who had only one hand available (alternating over time) to build a tower. Children's response choices were assessed (i.e. passing the cup on the free or occupied side to their partner). The study yielded two major findings. At all ages, children proactively planned their actions in a way that accommodated their partner's actions. However, only by 3½ years did children start to flexibly integrate their partner into their action plans. Even at age 5, children only showed minimal adjustments to their action partner. Candidate processes underlying these developmental changes (e.g. inhibitory control, cognitive flexibility, perspective taking) are discussed.

The hierarchical organization of the lateral prefrontal cortex

Higher-level cognition depends on the lateral prefrontal cortex (LPFC), but its functional organization has remained elusive. An influential proposal is that the LPFC is organized hierarchically whereby progressively rostral areas of the LPFC process/represent increasingly abstract information facilitating efficient and flexible cognition. However, support for this theory has been limited. Here, human fMRI data revealed rostral/caudal gradients of abstraction in the LPFC. Dynamic causal modeling revealed asymmetrical LPFC interactions indicative of hierarchical processing. Contrary to dominant assumptions, the relative strength of efferent versus afferent connections positioned mid LPFC as the apex of the hierarchy. Furthermore, cognitive demands induced connectivity modulations towards mid LPFC consistent with a role in integrating information for control operations. Moreover, the strengths of these dynamics were related to trait-measured higher-level cognitive ability. Collectively, these results suggest that the LPFC is hierarchically organized with the mid LPFC positioned to synthesize abstract and concrete information to control behavior.

DOI:http://dx.doi.org/10.7554/eLife.12112.001

Part of the brain called the lateral prefrontal cortex has a critical role in many of the processes seen as hallmarks of human cognition, such as reasoning, planning and problem-solving. Individuals with damage to the lateral prefrontal cortex are disorganized and easily distracted, and may show behaviors that are inappropriate for their context. However, the involvement of the lateral prefrontal cortex in such a wide range of processes makes it difficult to study. This in turn presents a significant roadblock to a full understanding of cognition and human intelligence.

Of particular interest is whether the lateral prefrontal cortex has a hierarchical organization wherein a region coordinates the roles of other regions, much like the chief executive of a company. Therefore, Nee and D’Esposito set out to map how the lateral prefrontal cortex is organized, and how its different regions communicate with each other to support complex cognition.

Brain imaging revealed that the rear (posterior) part of the lateral prefrontal cortex processes an individual’s current situation, while the front (anterior) prepares for future situations. Areas in the middle process both types of information. These central areas appear to be highly influential as they have stronger connections to the anterior and posterior regions than vice versa.

In cognitively demanding situations, the middle areas receive input from both anterior regions (potentially about future needs) and posterior regions (potentially about current needs). By combining the two sets of information, the middle areas can select behaviors that take into account both present circumstances and longer-term goals. With this strategic overview, the middle areas of the lateral prefrontal cortex are well positioned to play the part of the brain’s chief executive.

Future experiments should test whether the interactions observed between the different regions of the lateral prefrontal cortex are essential for complex planning and thinking. Additional work in animals would improve our understanding of the mechanisms underlying these interactions. Finally, studying how these interactions are altered in disorders such as schizophrenia, where the lateral prefrontal cortex shows abnormal activity, might pave the way for more effective treatments.

DOI:http://dx.doi.org/10.7554/eLife.12112.002

Central as well as Peripheral Attentional Bottlenecks in Dual-Task Performance Activate Lateral Prefrontal Cortices

Human information processing suffers from severe limitations in parallel processing. In particular, when required to respond to two stimuli in rapid succession, processing bottlenecks may appear at central and peripheral stages of task processing. Importantly, it has been suggested that executive functions are needed to resolve the interference arising at such bottlenecks. The aims of the present study were to test whether central attentional limitations (i.e., bottleneck at the decisional response selection stage) as well as peripheral limitations (i.e., bottleneck at response initiation) both demand executive functions located in the lateral prefrontal cortex. For this, we re-analyzed two previous studies, in which a total of 33 participants performed a dual-task according to the paradigm of the psychological refractory period (PRP) during functional magnetic resonance imaging (fMRI). In one study (N = 17), the PRP task consisted of two two-choice response tasks known to suffer from a central bottleneck (CB group). In the other study (N = 16), the PRP task consisted of two simple-response tasks known to suffer from a peripheral bottleneck (PB group). Both groups showed considerable dual-task costs in form of slowing of the second response in the dual-task (PRP effect). Imaging results are based on the subtraction of both single-tasks from the dual-task within each group. In the CB group, the bilateral middle frontal gyri and inferior frontal gyri were activated. Higher activation in these areas was associated with lower dual-task costs. In the PB group, the right middle frontal and inferior frontal gyrus (IFG) were activated. Here, higher activation was associated with higher dual-task costs. In conclusion we suggest that central and peripheral bottlenecks both demand executive functions located in lateral prefrontal cortices (LPFC). Differences between the CB and PB groups with respect to the exact prefrontal areas activated and the correlational patterns suggest that the executive functions resolving interference at least partially differ between the groups.

The Neural Basis of Postural Instability Gait Disorder Subtype of Parkinson's Disease: A PET and fMRI Study

AIMS

The aim of this study is to further uncover the neural basis of postural instability gait disorder (PIGD) subtype of Parkinson's disease.

METHODS

With F-18 fluorodeoxyglucose PET (FDG-PET), brain glucose metabolism of patients with PIGD (n = 15) was compared with healthy controls (n = 17) and tremor-dominant (TD) patients (n = 15), and the correlation between metabolism and PIGD symptoms was also assessed. Within PIGD symptom-correlated hypometabolic areas, the relationship of functional connectivity (FC) with motor and cognitive symptoms was examined by using functional MRI.

RESULTS

Compared with controls, patients with PIGD displayed a distributed pattern of brain hypometabolism including striatal, frontal, and parietal areas. Relative to the pattern of TD patients, the pattern of patients with PIGD had additional metabolic decreases in caudate and inferior parietal lobule (IPL, Brodmann area [BA] 40). In PIGD group, the metabolic reductions in IPL (BA 40), middle frontal gyrus (MFG, BA 9) and fusiform gyrus (FG, BA 20) were associated with severe PIGD symptoms. Regions showing such correlation were chosen for further seed-based FC analysis. Decreased FC within the prefrontal-parietal network (between the MFG and IPL) was associated with severe PIGD symptoms.

CONCLUSION

The involvement of the caudate, FG, and prefrontal-parietal network may be associated with the prominent gait impairments of PIGD subtype. Our findings expand the pathophysiological knowledge of PIGD subtype and provide valuable information for potential neuromodulation therapies alleviating gait disorders.

Change is good: Inter-trial switching of target category improves attentional selection in time

Limitations in the rate at which our attention can sample rapidly presented visual events are reflected in the attentional blink (AB), the inability to successfully report the second of two target stimuli embedded among distractors when separated by a temporal interval of approximately 300 ms. In two experiments we tested for predictions of two accounts of AB that ascribe the phenomenon to a temporary loss of attentional control or to an overzealous application of attentional control over the input filter. Manipulating the control load during the rapid serial presentation of visual events by means of a cued attentional switching procedure, we found an AB improvement when the target category was switched from the previous trial compared to when it was repeated from the previous trial. Findings appear inconsistent with the temporary loss of control account of the AB and support the hypothesis that AB results from an over-investment of attentional control.

The interaction of perceived control and Gambler's fallacy in risky decision making: An fMRI study

Limited recent evidence implicates the anterior/posterior cingulate (ACC/PCC) and lateral prefrontal networks as the neural substrates of risky decision-making biases such as illusions of control (IoC) and gambler's fallacy (GF). However, investigation is lacking on the dynamic interactive effect of those biases during decision making. Employing a card-guessing game that independently manipulates trial-by-trial perceived control and gamble outcome among 29 healthy female participants, we observed both IoC- and GF-type behaviors, as well as an interactive effect of previous control and previous outcome, with GF-type behaviors only following computer-selected, but not self-selected, outcomes. Imaging results implicated the ACC and left dorsolateral prefrontal cortex (DLPFC) in agency processing, and the cerebellum and right DLPFC in previous outcome processing, in accordance with past literature. Critically, the right inferior parietal lobule (IPL) exhibited significant betting-related activities to the interaction of previous control and previous outcome, showing more positive signals to previous computer-selected winning versus losing outcomes but the reverse pattern following self-selected outcomes, as well as responding to the interactive effect of control and outcome during feedback. Associations were also found between participants' behavioral sensitivity to the interactive effect of previous control and previous outcome, and right IPL signals, as well as its functional connectivity with neural networks implicated in agency and previous outcome processing. We propose that the right IPL provides the neural substrate for the interaction of perceived control and GF, through coordinating activities in the anterior and posterior cingulate cortices and working conjunctively with lateral PFC and other parietal networks.

The Monitoring and Control of Task Sequences in Human and Non-Human Primates

Our ability to plan and execute a series of tasks leading to a desired goal requires remarkable coordination between sensory, motor, and decision-related systems. Prefrontal cortex (PFC) is thought to play a central role in this coordination, especially when actions must be assembled extemporaneously and cannot be programmed as a rote series of movements. A central component of this flexible behavior is the moment-by-moment allocation of working memory and attention. The ubiquity of sequence planning in our everyday lives belies the neural complexity that supports this capacity, and little is known about how frontal cortical regions orchestrate the monitoring and control of sequential behaviors. For example, it remains unclear if and how sensory cortical areas, which provide essential driving inputs for behavior, are modulated by the frontal cortex during these tasks. Here, we review what is known about moment-to-moment monitoring as it relates to visually guided, rule-driven behaviors that change over time. We highlight recent human work that shows how the rostrolateral prefrontal cortex (RLPFC) participates in monitoring during task sequences. Neurophysiological data from monkeys suggests that monitoring may be accomplished by neurons that respond to items within the sequence and may in turn influence the tuning properties of neurons in posterior sensory areas. Understanding the interplay between proceduralized or habitual acts and supervised control of sequences is key to our understanding of sequential task execution. A crucial bridge will be the use of experimental protocols that allow for the examination of the functional homology between monkeys and humans. We illustrate how task sequences may be parceled into components and examined experimentally, thereby opening future avenues of investigation into the neural basis of sequential monitoring and control.

Speed-accuracy strategy regulations in prefrontal tumor patients

The ability to flexibly switch between fast and accurate decisions is crucial in everyday life. Recent neuroimaging evidence suggested that left lateral prefrontal cortex plays a role in switching from a quick response strategy to an accurate one. However, the causal role of the left prefrontal cortex in this particular, non-verbal, strategy switch has never been demonstrated. To fill this gap, we administered a perceptual decision-making task to neuro-oncological prefrontal patients, in which the requirement to be quick or accurate changed randomly on a trial-by-trial basis. To directly assess hemispheric asymmetries in speed-accuracy regulation, patients were tested a few days before and a few days after surgical excision of a brain tumor involving either the left (N=13) or the right (N=12) lateral frontal brain region. A group of age- and education-matched healthy controls was also recruited. To gain more insight on the component processes implied in the task, performance data (accuracy and speed) were not only analyzed separately but also submitted to a diffusion model analysis. The main findings indicated that the left prefrontal patients were impaired in appropriately adopting stricter response criteria in speed-to-accuracy switching trials with respect to healthy controls and right prefrontal patients, who were not impaired in this condition. This study demonstrates that the prefrontal cortex in the left hemisphere is necessary for flexible behavioral regulations, in particular when setting stricter response criteria is required in order to successfully switch from a speedy strategy to an accurate one.

Task-switching Cost and Intrinsic Functional Connectivity in the Human Brain: Toward Understanding Individual Differences in Cognitive Flexibility

The human ability to flexibly alternate between tasks (i.e., task-switching) represents a critical component of cognitive control. Many functional magnetic resonance imaging (fMRI) studies have explored the neural basis of the task-switching. However, no study to date has examined how individual differences in intrinsic functional architecture of the human brain are related to that of the task-switching. In the present study, we took 11 task-switching relevant areas from a meta-analysis study as the regions of interests (ROIs) and estimated their intrinsic functional connectivity (iFC) with the whole brain. This procedure was repeated for 32 healthy adults based upon their fMRI scans during resting-state (rfMRI) to investigate the correlations between switching cost and the iFC strength across these participants. This analysis found that switch cost was negatively correlated with a set of iFC involved ROIs including left inferior frontal junction, bilateral superior posterior parietal cortex, left precuneus, bilateral inferior parietal lobule, right middle frontal gyrus and bilateral middle occipital gyrus. These connectivity profiles represent an intrinsic functional architecture of task-switching where the left inferior frontal junction plays a hub role in this brain-behavior association. These findings are highly reproducible in another validation independent sample and provide a novel perspective for understanding the neural basis of individual differences in task-switching behaviors reflected in the intrinsic architecture of the human brain.

Ventral and dorsal streams for choosing word order during sentence production

Proficient language use requires speakers to vary word order and choose between different ways of expressing the same meaning. Prior statistical associations between individual verbs and different word orders are known to influence speakers' choices, but the underlying neural mechanisms are unknown. Here we show that distinct neural pathways are used for verbs with different statistical associations. We manipulated statistical experience by training participants in a language containing novel verbs and two alternative word orders (agent-before-patient, AP; patient-before-agent, PA). Some verbs appeared exclusively in AP, others exclusively in PA, and yet others in both orders. Subsequently, we used sparse sampling neuroimaging to examine the neural substrates as participants generated new sentences in the scanner. Behaviorally, participants showed an overall preference for AP order, but also increased PA order for verbs experienced in that order, reflecting statistical learning. Functional activation and connectivity analyses revealed distinct networks underlying the increased PA production. Verbs experienced in both orders during training preferentially recruited a ventral stream, indicating the use of conceptual processing for mapping meaning to word order. In contrast, verbs experienced solely in PA order recruited dorsal pathways, indicating the use of selective attention and sensorimotor integration for choosing words in the right order. These results show that the brain tracks the structural associations of individual verbs and that the same structural output may be achieved via ventral or dorsal streams, depending on the type of regularities in the input.