Neural correlates of speeded as compared with delayed responses in a stop signal task: an indirect analog of risk taking and association with an anxiety trait

The causal role of the subthalamic nucleus in the inhibitory network

The neural network mediating successful response inhibition mainly includes right hemisphere activation of the pre-supplementary motor area, inferior frontal gyrus (IFG), subthalamic nucleus (STN), and caudate nucleus. However, the causal role of these regions in the inhibitory network is undefined. Five patients with Parkinson's disease were assessed prior to and after therapeutic thermal ablation of the right STN in two separate functional magnetic resonance imaging (fMRI) sessions while performing a stop-signal task. Initiation times were faster but motor inhibition with the left hand (contralateral to the lesion) was significantly impaired as evident in prolonged stop-signal reaction times. Reduced inhibition after right subthalamotomy was associated (during successful inhibition) with the recruitment of basal ganglia regions outside the established inhibitory network. They included the putamen and caudate together with the anterior cingulate cortex and IFG of the left hemisphere. Subsequent network connectivity analysis (with the seed over the nonlesioned left STN) revealed a new inhibitory network after right subthalamotomies. Our results highlight the causal role of the right STN in the neural network for motor inhibition and the possible basal ganglia mechanisms for compensation upon losing a key node of the inhibition network.

Comprehensive assessment of memory function, inhibitory control, neural activity, and cortisol levels in late pregnancy

A considerable proportion of women subjectively perceive a detriment to their cognitive capacity during pregnancy, with decreased memory functions being the most frequently self-reported concerns. However, objective investigation of these perceived cognitive deficits has yielded inconsistent results. This study focused on memory functions during late pregnancy using multiple tasks designed to assess various memory indices, for example, working memory, learning rate, immediate recall, proactive and retroactive interference, delayed recall, retrieval efficiency, visuospatial constructional ability, recognition, and executive function. Additionally, sustained attention and inhibitory control were examined using a combined recognition stop-signal task. Electrophysiological brain activity during this task was recorded using a 128-channel electroencephalographic-event-related potential system. Salivary cortisol levels were assessed both prior to and following the experimental session. In contrast to the widely held belief, results demonstrated that women in late pregnancy did not exhibit a decline in their performance across the various memory tests. In terms of accuracy, there was not a single task in which poorer performance was found for pregnant women. The quality of memory performance was comparable, and in some cases even superior, among women in the pregnancy group. On the stop-signal task, pregnant women exhibited significantly better performance, and their electrophysiological data revealed greater centrally distributed P300 amplitude to "stop" signs, which may signify an enhanced neural efficiency in the domains of inhibitory executive control. Endocrine results revealed that pregnant women exhibited significantly lower levels of salivary cortisol, suggesting an attenuation of hypothalamic-pituitary-adrenocortical axis activity, which may contribute to the optimization of fetal development and growth.

Quantifying the effects of practicing a semantic task according to subclinical schizotypy

The learning ability of individuals within the schizophrenia spectrum is crucial for their psychosocial rehabilitation. When selecting a treatment, it is thus essential to consider the impact of medications on practice effects, an important type of learning ability. To achieve this end goal, a pre-treatment test has to be developed and tested in healthy participants first. This is the aim of the current work, which takes advantage of the schizotypal traits present in these participants to preliminary assess the test's validity for use among patients. In this study, 47 healthy participants completed the Schizotypal Personality Questionnaire (SPQ) and performed a semantic categorization task twice, with a 1.5-hour gap between sessions. Practice was found to reduce reaction times (RTs) in both low- and high-SPQ scorers. Additionally, practice decreased the amplitudes of the N400 event-related brain potentials elicited by semantically matching words in low SPQ scorers only, which shows the sensitivity of the task to schizotypy. Across the two sessions, both RTs and N400 amplitudes had good test-retest reliability. This task could thus be a valuable tool. Ongoing studies are currently evaluating the impact of fully deceptive placebos and of real antipsychotic medications on these practice effects. This round of research should subsequently assist psychiatrists in making informed decisions about selecting the most suitable medication for the psychosocial rehabilitation of a patient.

Examining impulsivity and risky decision making among school youth in balloon analogue risk task

BACKGROUND

Impulsivity trait as a risk factor which typically displayed in risk decision among school youth. This study aims to examine behavioral and cognitive problems of risky decision among Chinese young people aged 15-25 years. The balloon analogue risk task (BART) and event-related potential (ERP) were combine used to explore the neural mechanism of risky decision process whether infected by impulsivity trait.

METHODS

A total of 31 subjects were included, including 16 experimental subjects with risk behavior (RS), and 15 health control subjects with non-risk behavior (HC). BART were used to measure risk-taking propensity and ERP were to record in real time. RS vs. HC were compared to explain the relationship between impulsivity and risky decision.

RESULTS

Behavioral data in BART task shown that the RS subjects tended to make risky decisions. ERP results illustrate that P300 in RS subjects is more significant positive-going than HC that means dysfunction of cognitive control, and FRN in RS subjects is more negative-going than HC in negative feedback condition, which means individual with high impulsive would be more sensitive to unexpected outcome.

CONCLUSIONS

Impulsiveness is a risk factor for school adolescent, because RS subjects performed more risky decision than control group, the evidence indicate that individual with high impulsiveness would lead to be less sensitive to harmful consequences and more inclination to immediate rewards. Therefore, the inclination of risk taking can be powerfully informed by different levels of impulsiveness.

There are More than Two Sides to Antisocial Behavior: The Inextricable Link between Hemispheric Specialization and Environment

Human functions and traits are linked to cerebral networks serving different emotional and cognitive control systems, some of which rely on hemispheric specialization and integration to promote adaptive goal-directed behavior. Among the neural systems discussed in this context are those underlying pro- and antisocial behaviors. The diverse functions and traits governing our social behavior have been associated with lateralized neural activity. However, as with other complex behaviors, specific hemispheric roles are difficult to elucidate. This is due largely to environmental and contextual influences, which interact with neural substrates in the development and expression of pro and antisocial functions. This paper will discuss the reciprocal ties between environmental factors and hemispheric functioning in the context of social behavior. Rather than an exhaustive review, the paper will attempt to familiarize readers with the prominent literature and primary questions to encourage further research and in-depth discussion in this field.

Error and post-error processing in children with attention-deficit/hyperactivity disorder: An electrical neuroimaging study

OBJECTIVE

Inaccurate and inconsistent response styles in attention-deficit/hyperactivity disorder (ADHD) have been observed in a wide variety of cognitive tasks, in line with regulatory deficit models of ADHD. Event-related potential (ERP) studies of error processing have provided evidence for these models, but are limited in specificity. We aimed to improve the isolation, localization and identification of error (self-monitoring and adaptive control) and post-error (implementation of cognitive control) processing in ADHD.

METHODS

ERPs were obtained for 46 ADHD and 51 typically developing (TD) children using the stop-signal task. Response-locked error (Ne and Pe) and stimulus-locked post-error (N2) components were compared between groups. Ne/Pe were corrected for preceding stimulus overlap and group differences were localized.

RESULTS

Ne was intact, while Pe amplitude was markedly reduced in children with ADHD (ηp² = 0.14). Pe differences were localized in the dorsal posterior/midcingulate (BA31/24) cortex. While the TD group showed increased N2 amplitude in post-error trials (ηp² = 0.24), localized in the left ventrolateral prefrontal cortex (VLPFC) and angular gyrus, the ADHD group did not.

CONCLUSIONS

Self-regulation deficits in ADHD are associated with later stages of error processing and subsequent implementation of cognitive control.

SIGNIFICANCE

We contribute to the literature by further specifying error processing deficits in ADHD.

Impaired automatic but intact volitional inhibition in primary tic disorders

The defining character of tics is that they can be transiently suppressed by volitional effort of will, and at a behavioural level this has led to the concept that tics result from a failure of inhibition. However, this logic conflates the mechanism responsible for the production of tics with that used in suppressing them. Volitional inhibition of motor output could be increased to prevent the tic from reaching the threshold for expression, although this has been extensively investigated with conflicting results. Alternatively, automatic inhibition could prevent the initial excitation of the striatal tic focus-a hypothesis we have previously introduced. To reconcile these competing hypotheses, we examined different types of motor inhibition in a group of 19 patients with primary tic disorders and 15 healthy volunteers. We probed proactive and reactive inhibition using the conditional stop-signal task, and applied transcranial magnetic stimulation to the motor cortex, to assess movement preparation and execution. We assessed automatic motor inhibition with the masked priming task. We found that volitional movement preparation, execution and inhibition (proactive and reactive) were not impaired in tic disorders. We speculate that these mechanisms are recruited during volitional tic suppression, and that they prevent expression of the tic by inhibiting the nascent excitation released by the tic generator. In contrast, automatic inhibition was abnormal/impaired in patients with tic disorders. In the masked priming task, positive and negative compatibility effects were found for healthy controls, whereas patients with tics exhibited strong positive compatibility effects, but no negative compatibility effect indicative of impaired automatic inhibition. Patients also made more errors on the masked priming task than healthy control subjects and the types of errors were consistent with impaired automatic inhibition. Errors associated with impaired automatic inhibition were positively correlated with tic severity. We conclude that voluntary movement preparation/generation and volitional inhibition are normal in tic disorders, whereas automatic inhibition is impaired-a deficit that correlated with tic severity and thus may constitute a potential mechanism by which tics are generated.

Threat bias and resting state functional connectivity of the amygdala and bed nucleus stria terminalis

BACKGROUND

Previous research has distinguished the activations of the amygdala and bed nucleus of stria terminalis (BNST) during threat-related contingencies. However, how intrinsic connectivities of the amygdala and BNST relate to threat bias remains unclear. Here, we investigated how resting state functional connectivity (rsFC) of the amygdala and BNST in healthy controls (HC) and patients with anxiety-related disorders (PAD) associate with threat bias in a dot-probe task.

METHODS

Imaging and behavioral data of 30 PAD and 83 HC were obtained from the Nathan Kline Institute - Rockland sample and processed according to published routines. All imaging results were evaluated at voxel p < 0.001 and cluster p < 0.05, FWE corrected in SPM.

RESULTS

PAD and HC did not show differences in whole brain rsFC with either the amygdala or BNST. In linear regressions threat bias was positively correlated with amygdala-thalamus/anterior cingulate cortex (ACC) rsFC in HC but not PAD, and with BNST-caudate rsFC in PAD but not HC. Slope tests confirmed group differences in the correlations between threat bias and amygdala-thalamus/ACC as well as BNST-caudate rsFC.

LIMITATIONS

As only half of the patients included were diagnosed with comorbid anxiety, the current findings need to be considered with the clinical heterogeneity and require replication in populations specifically with anxiety disorders.

CONCLUSIONS

Together, these results suggest amygdala and BNST connectivities as new neural markers of anxiety disorders. Whereas amygdala-thalamus/ACC rsFC support adaptive regulation of threat response in the HC, BNST-caudate rsFC may reflect maladaptive neural processes that are dominated by anticipatory anxiety.

Cognitive, neural and endocrine functioning during late pregnancy: An Event-Related Potentials study

This study investigated cognitive, neural and endocrine function during late pregnancy. One of the first to examine brain ERPs in pregnant women, the study is unique in its focus on response inhibition function. In the study, cognitive function was evaluated by a digit-symbol coding test, an arithmetic ability test, and a visual stop-signal task which places enhanced demands on impulse control and response inhibition, considered a hallmark of executive function. Brain activity was measured by scalp-recorded Event-Related Potentials (ERPs) during the stop-signal task. HPA axis reactivity was assessed by measuring salivary cortisol levels before and after experimental sessions. Test performance, ERPs and cortisol reactivity were compared across groups of 23 women in their third trimester of pregnancy and 22 non-pregnant controls. Pregnant women scored lower than the control group on the digit-symbol coding test. On the stop-signal task, both groups had similar error rates, but pregnant women had longer response times to Go trials. On the Stop condition of the task in which a response must be inhibited, pregnant women demonstrated significantly better performance. At the electrophysiological level, in response to Go stimuli pregnant women exhibited greater amplitude of P2 than controls. In response to Stop-signals, pregnant women had lesser amplitudes of P1 and N2 and greater amplitude of P3. Cortisol reactivity to the test session was significantly more pronounced in non-pregnant women with significant correlations found between cortisol reactivity and behavioral responses. The results suggest that response patterns of women in late pregnancy are less impulsive and more cautious and controlled.

Gain-loss situation modulates neural responses to self-other decision making under risk

Although self-other behavioral differences in decision making under risk have been observed in some contexts, little is known about the neural mechanisms underlying such differences. Using functional magnetic resonance imaging (fMRI) and the cups task, in which participants choose between risky and sure options for themselves and others in gain and loss situations, we found that people were more risk-taking when making decisions for themselves than for others in loss situations but were equally risk-averse in gain situations. Significantly stronger activations were observed in the dorsomedial prefrontal cortex (dmPFC) and anterior insula (AI) when making decisions for the self than for others in loss situations but not in gain situations. Furthermore, the activation in the dmPFC was stronger when people made sure choices for others than for themselves in gain situations but not when they made risky choices, and was both stronger when people made sure and risky choices for themselves than for others in loss situations. These findings suggest that gain-loss situation modulates self-other differences in decision making under risk, and people are highly likely to differentiate the self from others when making decisions in loss situations.

Alcohol Expectancy and Cerebral Responses to Cue-Elicited Craving in Adult Nondependent Drinkers

BACKGROUND

Positive alcohol expectancy (AE) contributes to excessive drinking. Many imaging studies have examined cerebral responses to alcohol cues and how these regional processes related to problem drinking. However, it remains unclear how AE relates to cue response and whether AE mediates the relationship between cue response and problem drinking.

METHODS

A total of 61 nondependent drinkers were assessed with the Alcohol Expectancy Questionnaire and Alcohol Use Disorder Identification Test and underwent functional magnetic resonance imaging while exposed to alcohol and neutral cues. Imaging data were processed and analyzed with published routines, and mediation analyses were conducted to examine the interrelationships among global positive score of the Alcohol Expectancy Questionnaire, Alcohol Use Disorder Identification Test score, and regional responses to alcohol versus neutral cues.

RESULTS

Alcohol as compared with neutral cues engaged the occipital, retrosplenial, and medial orbitofrontal cortex as well as the left caudate head and red nucleus. The bilateral thalamus showed a significant correlation in cue response and in left superior frontal cortical connectivity with global positive score in a linear regression. Mediation analyses showed that global positive score completely mediated the relationship between thalamic cue activity as well as superior frontal cortical connectivity and Alcohol Use Disorder Identification Test score. The alternative models that AE contributed to problem drinking and, in turn, thalamic cue activity and connectivity were not supported.

CONCLUSIONS

The findings suggest an important role of the thalamic responses to alcohol cues in contributing to AE and at-risk drinking in nondependent drinkers. AEs may reflect a top-down modulation of the thalamic processing of alcohol cues, influencing the pattern of alcohol use.

Response inhibition and fronto-striatal-thalamic circuit dysfunction in cocaine addiction

BACKGROUND

Many studies have investigated how cognitive control may be compromised in cocaine addiction. Here, we extend this literature by employing spatial Independent Component Analysis (ICA) to describe circuit dysfunction in relation to impairment in response inhibition in cocaine addiction.

METHODS

Fifty-five cocaine-dependent (CD) and 55 age- and sex-matched non-drug-using healthy control individuals (HC) participated in the study. Task-relatedness of 40 independent components (ICs) was assessed using multiple regression analyses of component time courses with the modeled time courses of hemodynamic activity convolved with go success (GS), stop success (SS) and stop error (SE). This procedure produced beta-weights that represented the degree to which each IC was temporally associated with, or 'engaged', by each task event.

RESULTS

Behaviorally, CD participants showed prolonged stop signal reaction times (SSRTs) as compared to HC participants (p < 0.01). ICA identified two networks that showed differences in engagement related to SS between CD and HC (p < 0.05, FDR-corrected). The activity of the fronto-striatal-thalamic network was negatively correlated with SSRTs in HC but not in CD, suggesting a specific role of this network in mediating deficits of response inhibition in CD individuals. In contrast, the engagement of the fronto-parietal-temporal network did not relate to SSRTs, was similarly less engaged for both SS and SE trials, and may reflect attentional dysfunction in cocaine addiction.

CONCLUSIONS

This study highlights the utility of ICA in identifying neural circuitry engagement related to SST performance and suggests that specific networks may represent important targets in remedying executive-control impairment in cocaine addiction.

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.

Motor Preparation Disrupts Proactive Control in the Stop Signal Task

In a study of the stop signal task (SST) we employed Bayesian modeling to compute the estimated likelihood of stop signal or P(Stop) trial by trial and identified regional processes of conflict anticipation and response slowing. A higher P(Stop) is associated with prolonged go trial reaction time (goRT)-a form of sequential effect-and reflects proactive control of motor response. However, some individuals do not demonstrate a sequential effect despite similar go and stop success (SS) rates. We posited that motor preparation may disrupt proactive control more in certain individuals than others. Specifically, the time interval between trial and go signal onset-the fore-period (FP)-varies across trials and a longer FP is associated with a higher level of motor preparation and shorter goRT. Greater motor preparatory activities may disrupt proactive control. To test this hypothesis, we compared brain activations and Granger causal connectivities of 81 adults who demonstrated a sequential effect (SEQ) and 35 who did not (nSEQ). SEQ and nSEQ did not differ in regional activations to conflict anticipation, motor preparation, goRT slowing or goRT speeding. In contrast, SEQ and nSEQ demonstrated different patterns of Granger causal connectivities. P(Stop) and FP activations shared reciprocal influence in SEQ but FP activities Granger caused P(Stop) activities unidirectionally in nSEQ, and FP activities Granger caused goRT speeding activities in nSEQ but not SEQ. These findings support the hypothesis that motor preparation disrupts proactive control in nSEQ and provide direct neural evidence for interactive go and stop processes.

The Right Superior Frontal Gyrus and Individual Variation in Proactive Control of Impulsive Response

A hallmark of cognitive control is the ability to rein in impulsive responses. Previously, we used a Bayesian model to describe trial-by-trial likelihood of the stop signal or p(Stop) and related regional activations to p(Stop) to response slowing in a stop signal task. Here, we characterized the regional processes of conflict anticipation in association with intersubject variation in impulse control in 114 young adults. We computed the stop signal reaction time (SSRT) and a measure of motor urgency, indexed by the reaction time (RT) difference between go and stop error trials or "GoRT - SERT," where GoRT is the go trial RT and SERT is the stop error RT. Motor urgency and SSRT were positively correlated across subjects. A linear regression identified regional activations to p(Stop), each in correlation with SSRT and motor urgency. We hypothesized that shared neural activities mediate the correlation between motor urgency and SSRT in proactive control of impulsivity. Activation of the ventromedial prefrontal cortex, posterior cingulate cortex and right superior frontal gyrus (SFG) during conflict anticipation correlated negatively with the SSRT. Activation of the right SFG also correlated negatively with GoRT - SERT. Therefore, activation of the right SFG was associated with more efficient response inhibition and less motor urgency. A mediation analysis showed that right SFG activation to conflict anticipation mediates the correlation between SSRT and motor urgency bidirectionally. The current results highlight a specific role of the right SFG in translating conflict anticipation to the control of impulsive response, which is consistent with earlier studies suggesting its function in action restraint.

SIGNIFICANCE STATEMENT

Individuals vary in impulse control. However, the neural bases underlying individual variation in proactive control of impulsive responses remain unknown. Here, in a large sample of young adults, we showed that activation of the right superior frontal gyrus (SFG) during conflict anticipation is positively correlated with the capacity of inhibitory control and negatively with motor urgency in the stop signal task. Importantly, activity of the right SFG mediates the counteracting processes of inhibitory control and motor urgency across subjects. The results support a unique role of the right SFG in individual variation in cognitive control.

Distinct neural processes support post-success and post-error slowing in the stop signal task

Executive control requires behavioral adaptation to environmental contingencies. In the stop signal task (SST), participants exhibit slower go trial reaction time (RT) following a stop trial, whether or not they successfully interrupt the motor response. In previous fMRI studies, we demonstrated activation of the right-hemispheric ventrolateral prefrontal cortex, in the area of inferior frontal gyrus, pars opercularis (IFGpo) and anterior insula (AI), during post-error slowing (PES). However, in similar analyses we were not able to identify regional activities during post-success slowing (PSS). Here, we revisited this issue in a larger sample of participants (n=100) each performing the SST for 40 min during fMRI. We replicated IFGpo/AI activation to PES (p≤0.05, FWE corrected). Further, PSS engages decreased activation in a number of cortical regions including the left inferior frontal cortex (IFC; p≤0.05, FWE corrected). We employed Granger causality mapping to identify areas that provide inputs each to the right IFGpo/AI and left IFC, and computed single-trial amplitude (STA) of stop trials of these input regions as well as the STA of post-stop trials of the right IFGpo/AI and left IFC. The STAs of the right inferior precentral sulcus and supplementary motor area (SMA) and right IFGpo/AI were positively correlated and the STAs of the left SMA and left IFC were positively correlated (slope>0, p's≤0.01, one-sample t test), linking regional responses during stop success and error trials to those during PSS and PES. These findings suggest distinct neural mechanisms to support PSS and PES.

Clinical anxiety promotes excessive response inhibition

BACKGROUND

Laboratory tasks to delineate anxiety disorder features are used to refine classification and inform our understanding of etiological mechanisms. The present study examines laboratory measures of response inhibition, specifically the inhibition of a pre-potent motor response, in clinical anxiety. Data on associations between anxiety and response inhibition remain inconsistent, perhaps because of dissociable effects of clinical anxiety and experimentally manipulated state anxiety. Few studies directly assess the independent and interacting effects of these two anxiety types (state v. disorder) on response inhibition. The current study accomplished this goal, by manipulating state anxiety in healthy and clinically anxious individuals while they complete a response inhibition task.

METHOD

The study employs the threat-of-shock paradigm, one of the best-established manipulations for robustly increasing state anxiety. Participants included 82 adults (41 healthy; 41 patients with an anxiety disorder). A go/nogo task with highly frequent go trials was administered during alternating periods of safety and shock threat. Signal detection theory was used to quantify response bias and signal-detection sensitivity.

RESULTS

There were independent effects of anxiety and clinical anxiety on response inhibition. In both groups, heightened anxiety facilitated response inhibition, leading to reduced nogo commission errors. Compared with the healthy group, clinical anxiety was associated with excessive response inhibition and increased go omission errors in both the safe and threat conditions.

CONCLUSIONS

Response inhibition and its impact on go omission errors appear to be a promising behavioral marker of clinical anxiety. These results have implications for a dimensional view of clinical anxiety.

Motivational context for response inhibition influences proactive involvement of attention

Motoric inhibition is ingrained in human cognition and implicated in pervasive neurological diseases and disorders. The present electroencephalographic (EEG) study investigated proactive motivational adjustments in attention during response inhibition. We compared go-trial data from a stop-signal task, in which infrequently presented stop-signals required response cancellation without extrinsic incentives (“standard-stop”), to data where a monetary reward was posted on some stop-signals (“rewarded-stop”). A novel EEG analysis was used to directly model the covariation between response time and the attention-related N1 component. A positive relationship between response time and N1 amplitudes was found in the standard-stop context, but not in the rewarded-stop context. Simultaneously, average go-trial N1 amplitudes were larger in the rewarded-stop context. This suggests that down-regulation of go-signal-directed attention is dynamically adjusted in the standard-stop trials, but is overridden by a more generalized increase in attention in reward-motivated trials. Further, a diffusion process model indicated that behavior between contexts was the result of partially opposing evidence accumulation processes. Together these analyses suggest that response inhibition relies on dynamic and flexible proactive adjustments of low-level processes and that contextual changes can alter their interplay. This could prove to have ramifications for clinical disorders involving deficient response inhibition and impulsivity.

Strategic down-regulation of attentional resources as a mechanism of proactive response inhibition

Efficiently avoiding inappropriate actions in a changing environment is central to cognitive control. One mechanism contributing to this ability is the deliberate slowing down of responses in contexts where full response cancellation might occasionally be required, referred to as proactive response inhibition. The present electroencephalographic (EEG) study investigated the role of attentional processes in proactive response inhibition in humans. To this end, we compared data from a standard stop-signal task, in which stop signals required response cancellation ('stop-relevant'), to data where possible stop signals were task-irrelevant ('stop-irrelevant'). Behavioral data clearly indicated the presence of proactive slowing in the standard stop-signal task. A novel single-trial analysis was used to directly model the relationship between response time and the EEG data of the go-trials in both contexts within a multilevel linear models framework. We found a relationship between response time and amplitude of the attention-related N1 component in stop-relevant blocks, a characteristic that was fully absent in stop-irrelevant blocks. Specifically, N1 amplitudes were lower the slower the response time, suggesting that attentional resources were being strategically down-regulated to control response speed. Drift diffusion modeling of the behavioral data indicated that multiple parameters differed across the two contexts, likely suggesting the contribution from independent brain mechanisms to proactive slowing. Hence, the attentional mechanism of proactive response control we report here might coexist with known mechanisms that are more directly tied to motoric response inhibition. As such, our study opens up new research avenues also concerning clinical conditions that feature deficits in proactive response inhibition.

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.

Individual variation in the neural processes of motor decisions in the stop signal task: the influence of novelty seeking and harm avoidance personality traits

Personality traits contribute to variation in human behavior, including the propensity to take risk. Extant work targeted risk-taking processes with an explicit manipulation of reward, but it remains unclear whether personality traits influence simple decisions such as speeded versus delayed responses during cognitive control. We explored this issue in an fMRI study of the stop signal task, in which participants varied in response time trial by trial, speeding up and risking a stop error or slowing down to avoid errors. Regional brain activations to speeded versus delayed motor responses (risk-taking) were correlated to novelty seeking (NS), harm avoidance (HA) and reward dependence (RD), with age and gender as covariates, in a whole brain regression. At a corrected threshold, the results showed a positive correlation between NS and risk-taking responses in the dorsomedial prefrontal, bilateral orbitofrontal, and frontopolar cortex, and between HA and risk-taking responses in the parahippocampal gyrus and putamen. No regional activations varied with RD. These findings demonstrate that personality traits influence the neural processes of executive control beyond behavioral tasks that involve explicit monetary reward. The results also speak broadly to the importance of characterizing inter-subject variation in studies of cognition and brain functions.

Association of Drinking Problems and Duration of Alcohol Use to Inhibitory Control in Nondependent Young Adult Social Drinkers

BACKGROUND

Deficits in inhibitory control have been widely implicated in alcohol misuse. However, the literature does not readily distinguish the effects of drinking problems and chronic alcohol use. Here, we examined how years of drinking and the Alcohol Use Disorders Identification Test (AUDIT) score each influences the cerebral responses to inhibitory control in nondependent drinkers.

METHODS

Fifty-seven adult drinkers and 57 age- and gender-matched nondrinkers participated in one 40-minute functional magnetic resonance imaging scan of the stop signal task. Data were preprocessed and modeled using SPM8. In a regression model, we contrasted stop and go success trials for individuals and examined activities of response inhibition each in link with the AUDIT score and years of alcohol use in group analyses. We specified the effects of duration of use by contrasting regional activations of drinkers and age-related changes in nondrinkers. In mediation analyses, we investigated how regional activities mediate the relationship between drinking problems and response inhibition.

RESULTS

Higher AUDIT score but not years of drinking was positively correlated with prolonged stop signal reaction time (SSRT) and diminished responses in the cerebellum, thalamus, frontal and parietal regions, independent of years of alcohol use. Further, activity of the thalamus, anterior cingulate cortex, and presupplementary motor area significantly mediates the association, bidirectionally, between the AUDIT score and SSRT. The duration of alcohol use was associated with decreased activation in the right inferior frontal gyrus extending to superior temporal gyrus, which was not observed for age-related changes in nondrinkers.

CONCLUSIONS

The results distinguished the association of drinking problems and years of alcohol use to inhibitory control in young adult nondependent drinkers. These new findings extend the imaging literature of alcohol misuse and may have implications for treatment to prevent the escalation from social to dependent drinking. More research is needed to confirm age-independent neural correlates of years of alcohol use.

Anticipating conflict: Neural correlates of a Bayesian belief and its motor consequence

Previous studies have examined the neural correlates of proactive control using a variety of behavioral paradigms; however, the neural network relating the control process to its behavioral consequence remains unclear. Here, we applied a dynamic Bayesian model to a large fMRI data set of the stop signal task to address this issue. By estimating the probability of the stop signal - p(Stop) - trial by trial, we showed that higher p(Stop) is associated with prolonged go trial reaction time (RT), indicating proactive control of motor response. In modeling fMRI signals at trial and target onsets, we distinguished activities of proactive control, prediction error, and RT slowing. We showed that the anterior pre-supplementary motor area (pre-SMA) responds specifically to increased stop signal likelihood, and its activity is correlated with activations of the posterior pre-SMA and bilateral anterior insula during prolonged response times. This directional link is also supported by Granger causality analysis. Furthermore, proactive control, prediction error, and time-on-task are each mapped to distinct areas in the medial prefrontal cortex. Together, these findings dissect regional functions of the medial prefrontal cortex in cognitive control and provide system level evidence associating conflict anticipation with its motor consequence.

Independent component analysis of functional networks for response inhibition: Inter-subject variation in stop signal reaction time

Cognitive control is a critical executive function. Many studies have combined general linear modeling and the stop signal task (SST) to delineate the component processes of cognitive control. For instance, by contrasting stop success (SS) and stop error (SE) trials in the SST, investigators examined regional responses to stop signal inhibition. In contrast to this parameterized approach, independent component analysis (ICA) elucidates brain networks subserving cognitive control. In our earlier work of 59 adults performing the SST during fMRI, we characterized six independent components (ICs). However, none of these ICs correlated with stop signal performance, raising questions about their behavioral validity. Here, in a larger sample (n = 100), we identified and explored 23 ICs for correlation with the stop signal reaction time (SSRT), a measure of the efficiency of response inhibition. At a corrected threshold (P < 0.0005), a paracentral lobule-midcingulate network and a left inferior parietal-supplementary motor-somatomotor network showed a positive correlation between SE beta weight and SSRT. In contrast, a midline cerebellum-thalamus-pallidum network showed a negative correlation between SE beta weight and SSRT. These findings suggest that motor preparation and execution prolongs the SSRT, likely via an interaction between the go and stop processes as suggested by the race model. Behaviorally, consistent with this hypothesis, the difference in G and SE reaction times is positively correlated with SSRT across subjects. These new results highlight the importance of cognitive motor regions in response inhibition and support the utility of ICA in uncovering functional networks for cognitive control in the SST.

Barratt Impulsivity and Neural Regulation of Physiological Arousal

Background

Theories of personality have posited an increased arousal response to external stimulation in impulsive individuals. However, there is a dearth of studies addressing the neural basis of this association.

Methods

We recorded skin conductance in 26 individuals who were assessed with Barratt Impulsivity Scale (BIS-11) and performed a stop signal task during functional magnetic resonance imaging. Imaging data were processed and modeled with Statistical Parametric Mapping. We used linear regressions to examine correlations between impulsivity and skin conductance response (SCR) to salient events, identify the neural substrates of arousal regulation, and examine the relationship between the regulatory mechanism and impulsivity.

Results

Across subjects, higher impulsivity is associated with greater SCR to stop trials. Activity of the ventromedial prefrontal cortex (vmPFC) negatively correlated to and Granger caused skin conductance time course. Furthermore, higher impulsivity is associated with a lesser strength of Granger causality of vmPFC activity on skin conductance, consistent with diminished control of physiological arousal to external stimulation. When men (n = 14) and women (n = 12) were examined separately, however, there was evidence suggesting association between impulsivity and vmPFC regulation of arousal only in women.

Conclusions

Together, these findings confirmed the link between Barratt impulsivity and heightened arousal to salient stimuli in both genders and suggested the neural bases of altered regulation of arousal in impulsive women. More research is needed to explore the neural processes of arousal regulation in impulsive individuals and in clinical conditions that implicate poor impulse control.

Conflict anticipation in alcohol dependence - A model-based fMRI study of stop signal task

Background

Our previous work characterized altered cerebral activations during cognitive control in individuals with alcohol dependence (AD). A hallmark of cognitive control is the ability to anticipate changes and adjust behavior accordingly. Here, we employed a Bayesian model to describe trial-by-trial anticipation of the stop signal and modeled fMRI signals of conflict anticipation in a stop signal task. Our goal is to characterize the neural correlates of conflict anticipation and its relationship to response inhibition and alcohol consumption in AD.

Methods

Twenty-four AD and 70 age and gender matched healthy control individuals (HC) participated in the study. fMRI data were pre-processed and modeled with SPM8. We modeled fMRI signals at trial onset with individual events parametrically modulated by estimated probability of the stop signal, p(Stop), and compared regional responses to conflict anticipation between AD and HC. To address the link to response inhibition, we regressed whole-brain responses to conflict anticipation against the stop signal reaction time (SSRT).

Results

Compared to HC (54/70), fewer AD (11/24) showed a significant sequential effect — a correlation between p(Stop) and RT during go trials — and the magnitude of sequential effect is diminished, suggesting a deficit in proactive control. Parametric analyses showed decreased learning rate and over-estimated prior mean of the stop signal in AD. In fMRI, both HC and AD responded to p(Stop) in bilateral inferior parietal cortex and anterior pre-supplementary motor area, although the magnitude of response increased in AD. In contrast, HC but not AD showed deactivation of the perigenual anterior cingulate cortex (pgACC). Furthermore, deactivation of the pgACC to increasing p(Stop) is positively correlated with the SSRT in HC but not AD. Recent alcohol consumption is correlated with increased activation of the thalamus and cerebellum in AD during conflict anticipation.

Conclusions

The current results highlight altered proactive control that may serve as an additional behavioral and neural marker of alcohol dependence.

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We addressed the neural correlates of conflict anticipation in AD and HC in an SST.

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AD showed greater activation in preSMA and less deactivation in pgACC.

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Deactivation in pgACC inversely correlated with SSRT in HC but not AD.

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Alcohol use is correlated with greater thalamic and cerebellar activations in AD.

Altered gray matter density and disrupted functional connectivity of the amygdala in adults with Internet gaming disorder

OBJECTIVES

The aim of this study was to evaluate the altered brain structure and functional connectivity (FC) among subjects with Internet gaming disorder (IGD).

METHODS

We recruited 30 males with IGD and 30 controls and evaluated their gray matter density (GMD) and FC using resting fMRI. The severities of IGD, gaming urge, and impulsivity were also assessed.

RESULTS

The results demonstrated that the subjects with IGD had a higher impulsivity and a greater severity of IGD. The subjects with IGD had a lower GMD over the bilateral amygdala than the controls. Further, the subjects with IGD had lower FC with the left amygdala over the left dorsolateral prefrontal lobe (DLPFC) and with the right amygdala over the left DLPFC and orbital frontal lobe (OFL). They also had higher FC with the bilateral amygdala over the contralateral insula than the controls. The FC between the left amygdala and DLPFC was negatively correlated with impulsivity. The FC of the right amygdala to the left DLPFC and orbital frontal lobe was also negatively correlated with impulsivity. Our results indicated that the altered GMD over the amygdala might represent vulnerability to IGD, such as impulsivity. Further analysis of the amygdala demonstrated impaired FC to the frontal lobe, which represents impulsivity.

CONCLUSION

The results of this study suggested that the amygdala plays a very influential role in the mechanism of IGD. Its detailed role should be further evaluated in future study and should be considered in the treatment of IGD.

Reward anticipation enhances brain activation during response inhibition

The chance to achieve a reward starts up the required neurobehavioral mechanisms to adapt our thoughts and actions in order to accomplish our objective. However, reward does not equally reinforce everybody but depends on interindividual motivational dispositions. Thus, immediate reward contingencies can modulate the cognitive process required for goal achievement, while individual differences in personality can affect this modulation. We aimed to test the interaction between inhibition-related brain response and motivational processing in a stop signal task by reward anticipation and whether individual differences in sensitivity to reward (SR) modulate such interaction. We analyzed the cognitive-motivational interaction between the brain pattern activation of the regions involved in correct and incorrect response inhibition and the association between such brain activations and SR scores. We also analyzed the behavioral effects of reward on both reaction times for the "go" trials before and after correct and incorrect inhibition in order to test error prediction performance and postinhibition adjustment. Our results show enhanced activation during response inhibition under reward contingencies in frontal, parietal, and subcortical areas. Moreover, activation of the right insula and the left putamen positively correlates with the SR scores. Finally, the possibility of reward outcome affects not only response inhibition performance (e.g., reducing stop signal reaction time), but also error prediction performance and postinhibition adjustment. Therefore, reward contingencies improve behavioral performance and enhance brain activation during response inhibition, and SR is related to brain activation. Our results suggest the conditions and factors that subserve cognitive control strategies in cognitive motivational interactions during response inhibition.

Gray matter volume correlates of global positive alcohol expectancy in non-dependent adult drinkers

Alcohol use and misuse is known to involve structural brain changes. Numerous imaging studies have examined changes in gray matter (GM) volumes in dependent drinkers, but there is little information on whether non-dependent drinking is associated with structural changes and whether these changes are related to psychological factors-such as alcohol expectancy-that influence drinking behavior. We used voxel-based morphometry (VBM) to examine whether the global positive scale of alcohol expectancy, as measured by the Alcohol Expectancy Questionnaire-3, is associated with specific structural markers and whether such markers are associated with drinking behavior in 113 adult non-dependent drinkers (66 women). Alcohol expectancy is positively correlated with GM volume of left precentral gyrus (PCG) in men and women combined and bilateral superior frontal gyri (SFG) in women, and negatively correlated with GM volume of the right ventral putamen in men. Furthermore, mediation analyses showed that the GM volume of PCG mediate the correlation of alcohol expectancy and the average number of drinks consumed per occasion and monthly total number of drinks in the past year. When recent drinking was directly accounted for in multiple regressions, GM volume of bilateral dorsolateral prefrontal cortices correlated positively with alcohol expectancy in the combined sample. To our knowledge, these results are the first to identify the structural brain correlates of alcohol expectancy and its mediation of drinking behaviors. These findings suggest that more studies are needed to investigate increased GM volume in the frontal cortices as a neural correlate of alcohol expectancy.

Event-related potentials for post-error and post-conflict slowing

In a reaction time task, people typically slow down following an error or conflict, each called post-error slowing (PES) and post-conflict slowing (PCS). Despite many studies of the cognitive mechanisms, the neural responses of PES and PCS continue to be debated. In this study, we combined high-density array EEG and a stop-signal task to examine event-related potentials of PES and PCS in sixteen young adult participants. The results showed that the amplitude of N2 is greater during PES but not PCS. In contrast, the peak latency of N2 is longer for PCS but not PES. Furthermore, error-positivity (Pe) but not error-related negativity (ERN) was greater in the stop error trials preceding PES than non-PES trials, suggesting that PES is related to participants' awareness of the error. Together, these findings extend earlier work of cognitive control by specifying the neural correlates of PES and PCS in the stop signal task.

Cognitive control in opioid dependence and methadone maintenance treatment

BACKGROUND

Substance misuse is associated with cognitive dysfunction. We used a stop signal task to examine deficits in cognitive control in individuals with opioid dependence (OD). We examined how response inhibition and post-error slowing are compromised and whether methadone maintenance treatment (MMT), abstinence duration, and psychiatric comorbidity are related to these measures in individuals with OD.

METHODS

Two-hundred-and-sixty-four men with OD who were incarcerated at a detention center and abstinent for up to 2 months (n = 108) or at a correctional facility and abstinent for approximately 6 months (n = 156), 65 OD men under MMT at a psychiatric clinic, and 64 age and education matched healthy control (HC) participants were assessed. We computed the stop signal reaction time (SSRT) to index the capacity of response inhibition and post-error slowing (PES) to represent error-related behavioral adjustment, as in our previous work. We examined group effects with analyses of variance and covariance analyses, followed by planned comparisons. Specifically, we compared OD and HC participants to examine the effects of opioid dependence and MMT and compared OD sub-groups to examine the effects of abstinence duration and psychiatric comorbidity.

RESULTS

The SSRT was significantly prolonged in OD but not MMT individuals, as compared to HC. The extent of post-error slowing diminished in OD and MMT, as compared to HC (trend; p = 0.061), and there was no difference between the OD and MMT groups. Individuals in longer abstinence were no less impaired in these measures. Furthermore, these results remained when psychiatric comorbidities including misuse of other substances were accounted for.

CONCLUSIONS

Methadone treatment appears to be associated with relatively intact cognitive control in opioid dependent individuals. MMT may facilitate public health by augmenting cognitive control and thereby mitigating risky behaviors in heroin addicts.

Error-related functional connectivity of the thalamus in cocaine dependence

Error processing is a critical component of cognitive control, an executive function that has been widely implicated in substance misuse. In previous studies we showed that error related activations of the thalamus predicted relapse to drug use in cocaine addicted individuals (Luo et al., 2013). Here, we investigated whether the error-related functional connectivity of the thalamus is altered in cocaine dependent patients (PCD, n = 54) as compared to demographically matched healthy individuals (HC, n = 54). The results of a generalized psychophysiological interaction analysis showed negative thalamic connectivity with the ventral medial prefrontal cortex (vmPFC), in the area of perigenual and subgenual anterior cingulate cortex, in HC but not PCD (p < 0.05, corrected, two-sample t test). This difference in functional connectivity was not observed for task-residual signals, suggesting that it is specific to task-related processes during cognitive control. Further, the thalamic-vmPFC connectivity is positively correlated with the amount of cocaine use in the prior month for female but not for male PCD. These findings add to recent literature and provide additional evidence for circuit-level biomarkers of cocaine dependence.

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Error-related thalamic-vmPFC connectivity is altered in cocaine misuse.

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This altered connectivity is associated with impaired self control.

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This deficit is associated with recent cocaine use in women but not men.

Cerebral gray matter volumes and low-frequency fluctuation of BOLD signals in cocaine dependence: duration of use and gender difference

BACKGROUND

Magnetic resonance imaging has provided a wealth of information on altered brain activations and structures in individuals addicted to cocaine. However, few studies have considered the influence of age and alcohol use on these changes.

METHODS

We examined gray matter volume with voxel based morphometry (VBM) and low frequency fluctuation (LFF) of BOLD signals as a measure of cerebral activity of 84 cocaine dependent (CD) and 86 healthy control (HC) subjects. We performed a covariance analysis to account for the effects of age and years of alcohol use.

RESULTS

Compared to HC, CD individuals showed decreased gray matter (GM) volumes in frontal and temporal cortices, middle/posterior cingulate cortex, and the cerebellum, at p<0.05, corrected for multiple comparisons. The GM volume of the bilateral superior frontal gyri (SFG) and cingulate cortices were negatively correlated with years of cocaine use, with women showing a steeper loss in the right SFG in association with duration of use. In contrast, the right ventral putamen showed increased GM volume in CD as compared to HC individuals. Compared to HC, CD individuals showed increased fractional amplitude of LFF (fALFF) in the thalamus, with no significant overlap with regions showing GM volume loss.

CONCLUSIONS

These results suggested that chronic cocaine use is associated with distinct changes in cerebral structure and activity that can be captured by GM volume and fALFF of BOLD signals.

Bayesian network models in brain functional connectivity analysis

Much effort has been made to better understand the complex integration of distinct parts of the human brain using functional magnetic resonance imaging (fMRI). Altered functional connectivity between brain regions is associated with many neurological and mental illnesses, such as Alzheimer and Parkinson diseases, addiction, and depression. In computational science, Bayesian networks (BN) have been used in a broad range of studies to model complex data set in the presence of uncertainty and when expert prior knowledge is needed. However, little is done to explore the use of BN in connectivity analysis of fMRI data. In this paper, we present an up-to-date literature review and methodological details of connectivity analyses using BN, while highlighting caveats in a real-world application. We present a BN model of fMRI dataset obtained from sixty healthy subjects performing the stop-signal task (SST), a paradigm widely used to investigate response inhibition. Connectivity results are validated with the extant literature including our previous studies. By exploring the link strength of the learned BN's and correlating them to behavioral performance measures, this novel use of BN in connectivity analysis provides new insights to the functional neural pathways underlying response inhibition.

Methylphenidate remediates error-preceding activation of the default mode brain regions in cocaine-addicted individuals

Many previous studies suggest the potential of psychostimulants in improving cognitive functioning. Our earlier pharmacological brain imaging study showed that intravenous methylphenidate (MPH) improves inhibitory control by altering cortico-striato-thalamic activations in cocaine-dependent (CD) individuals. Here we provide additional evidence for the effects of MPH in restoring cerebral activations during cognitive performance. Ten CD individuals performed a stop signal task (SST) during functional magnetic resonance imaging (fMRI) in two sessions, in which either MPH (0.5mg/kg body weight) or saline was administered intravenously. In the SST, a frequent go signal instructs participants to make a speeded response and a less frequent stop signal instructs them to withhold the response. Our previous work described increased activation of the precuneus/posterior cingulate cortex and ventromedial prefrontal cortex-regions of the default mode network (DMN)-before participants committed a stop error in healthy control but not CD individuals (Bednarski et al., 2011). The current results showed that, compared to saline, MPH restored error-preceding activations of DMN regions in CD individuals. The extent of the changes in precuneus activity was correlated with MPH-elicited increase in systolic blood pressure. These findings suggest that the influence of MPH on cerebral activations may extend beyond cognitive control and provide additional evidence warranting future studies to investigate the neural mechanisms and physiological markers of the efficacy of agonist therapy in cocaine dependence.

Neural bases of individual variation in decision time

People make decisions by evaluating existing evidence against a threshold or level of confidence. Individuals vary widely in response times even when they perform a simple task in the laboratory. We examine the neural bases of this individual variation by combining computational modeling and brain imaging of 64 healthy adults performing a stop signal task. Behavioral performance was modeled by an accumulator model that describes the process of information growth to reach a threshold to respond. In this model, go trial reaction time (goRT) is jointly determined by the information growth rate, threshold, and movement time (MT). In a linear regression of activations in successful go and all stop (Go+Stop) trials against goRT across participants, the insula, supplementary motor area (SMA), pre-SMA, thalamus including the subthalamic nucleus (STN), and caudate head respond to increasing goRT. Among these areas, the insula, SMA, and thalamus including the STN respond to a slower growth rate, the caudate head responds to an elevated threshold, and the pre-SMA responds to a longer MT. In the regression of Go+Stop trials against the stop signal reaction time (SSRT), the pre-SMA shows a negative correlation with SSRT. These results characterize the component processes of decision making and elucidate the neural bases of a critical aspect of inter-subject variation in human behavior. These findings also suggest that the pre-SMA may play a broader role in response selection and cognitive control rather than simply response inhibition in the stop signal task.

Ventromedial prefrontal cortex and the regulation of physiological arousal

Neuroimaging studies show a correlation between activity of the ventromedial prefrontal cortex (vmPFC) and skin conductance measurements. However, little is known whether this brain region plays a causal role in regulating physiological arousal. To address this question, we employed Granger causality analysis (GCA) to establish causality between cerebral blood oxygenation level-dependent and skin conductance signals in 24 healthy adults performing a cognitive task during functional magnetic resonance imaging. The results showed that activity of the vmPFC not only negatively correlated with skin conductance level (SCL) but also Granger caused SCL, thus establishing the direction of influence. Importantly, across participants, the strength of Granger causality was negatively correlated to phasic skin conductance responses elicited by external events during the behavioral task. In contrast, activity of the dorsal anterior cingulate cortex positively correlated with SCL but did not show a causal relationship in GCA. These new findings indicate that the vmPFC plays a causal role in regulating physiological arousal. Increased vmPFC activity leads to a decrease in skin conductance. The findings may also advance our understanding of dysfunctions of the vmPFC in mood and anxiety disorders that involve altered control of physiological arousal.

Changes in cerebral morphometry and amplitude of low-frequency fluctuations of BOLD signals during healthy aging: correlation with inhibitory control

Aging is known to be associated with changes in cerebral morphometry and in regional activations during resting or cognitive challenges. Here, we investigated the effects of age on cerebral gray matter (GM) volumes and fractional amplitude of low-frequency fluctuation (fALFF) of blood oxygenation level-dependent signals in 111 healthy adults, 18-72 years of age. GM volumes were computed using voxel-based morphometry as implemented in Statistical Parametric Mapping, and fALFF maps were computed for task-residuals as described in Zhang and Li (Neuroimage 49:1911-1918, 2010) for individual participants. Across participants, a simple regression against age was performed for GM volumes and fALFF, respectively, with quantity of recent alcohol use as a covariate. At cluster level p < 0.05, corrected for family-wise error of multiple comparisons, GM volumes declined with age in prefrontal/frontal regions, bilateral insula, and left inferior parietal lobule (IPL), suggesting structural vulnerability of these areas to aging. FALFF was negatively correlated with age in the supplementary motor area (SMA), pre-SMA, anterior cingulate cortex, bilateral dorsal lateral prefrontal cortex (DLPFC), right IPL, and posterior cingulate cortex, indicating that spontaneous neural activities in these areas during cognitive performance decrease with age. Notably, these age-related changes overlapped in the prefrontal/frontal regions including the pre-SMA, SMA, and DLPFC. Furthermore, GM volumes and fALFF of the pre-SMA/SMA were negatively correlated with the stop signal reaction time, in accord with our earlier work. Together, these results describe anatomical and functional changes in prefrontal/frontal regions and how these changes are associated with declining inhibitory control during aging.

Bayesian prediction and evaluation in the anterior cingulate cortex

The dorsal anterior cingulate cortex (dACC) has been implicated in a variety of cognitive control functions, among them the monitoring of conflict, error, and volatility, error anticipation, reward learning, and reward prediction errors. In this work, we used a Bayesian ideal observer model, which predicts trial-by-trial probabilistic expectation of stop trials and response errors in the stop-signal task, to differentiate these proposed functions quantitatively. We found that dACC hemodynamic response, as measured by functional magnetic resonance imaging, encodes both the absolute prediction error between stimulus expectation and outcome, and the signed prediction error related to response outcome. After accounting for these factors, dACC has no residual correlation with conflict or error likelihood in the stop-signal task. Consistent with recent monkey neural recording studies, and in contrast with other neuroimaging studies, our work demonstrates that dACC reports at least two different types of prediction errors, and beyond contexts that are limited to reward processing.

Error processing and gender-shared and -specific neural predictors of relapse in cocaine dependence

Deficits in cognitive control are implicated in cocaine dependence. Previously, combining functional magnetic resonance imaging and a stop signal task, we demonstrated altered cognitive control in cocaine-dependent individuals. However, the clinical implications of these cross-sectional findings and, in particular, whether the changes were associated with relapse to drug use, were not clear. In a prospective study, we recruited 97 treatment-seeking individuals with cocaine dependence to perform the stop signal task during functional magnetic resonance imaging and participate in follow-up assessments for 3 months, during which time cocaine use was evaluated with timeline follow back and ascertained by urine toxicology tests. Functional magnetic resonance imaging data were analysed using general linear models as implemented in Statistical Parametric Mapping 8, with the contrast 'stop error greater than stop success trials' to index error processing. Using voxelwise analysis with logistic and Cox regressions, we identified brain activations of error processing that predict relapse and time to relapse. In females, decreased error-related activations of the thalamus and dorsal anterior cingulate cortex predicted relapse and an earlier time to relapse. In males, decreased error-related activations of the dorsal anterior cingulate cortex and left insula predicted relapse and an earlier time to relapse. These regional activations were validated with data resampling and predicted relapse with an average area under the curve of 0.849 in receiver operating characteristic analyses. These findings provide direct evidence linking deficits in cognitive control to clinical outcome in a moderate-sized cohort of cocaine-dependent individuals. These results may provide a useful basis for future studies to examine how psychosocial factors interact with cognitive control to determine drug use and to evaluate the efficacy of pharmacological or behavioural treatment in remediating deficits of cognitive control in cocaine addicts.

Effects of androgen deprivation on brain function in prostate cancer patients - a prospective observational cohort analysis

Background

Despite a lack of consensus regarding effectiveness, androgen deprivation therapy (ADT) is a common treatment for non-metastatic, low-risk prostate cancer. To examine a particular clinical concern regarding the possible impact of ADT on cognition, the current study combined neuropsychological testing with functional magnetic resonance imaging (fMRI) to assess both brain activation during cognitive performance as well as the integrity of brain connectivity.

Methods

In a prospective observational cohort analysis of men with non-metastatic prostate cancer at a Veterans Affairs medical center, patients receiving ADT were compared with patients not receiving ADT at baseline and at 6 months. Assessments included fMRI, the N-back task (for working memory), the stop-signal task (for cognitive control), and a quality of life questionnaire.

Results

Among 36 patients enrolled (18 in each group), 30 completed study evaluations (15 in each group); 5 withdrew participation and 1 died. Results for the N-back task, stop-signal task, and quality of life were similar at 6 months vs. baseline in each group. In contrast, statistically significant associations were found between ADT use (vs. non use) and decreased medial prefrontal cortical activation during cognitive control, as well as decreased connectivity between the medial prefrontal cortex and other regions involved with cognitive control.

Conclusions

Although ADT for 6 months did not affect selected tests of cognitive function, brain activations during cognitive control and functional brain connectivity were impaired on fMRI. The long-term clinical implications of these changes are not known and warrant future study.

The influence of risky and conservative mental sets on cerebral activations of cognitive control

Mental set is known to influence cognitive functioning. Risk-seeking and risk-aversive mental sets alter cerebral responses to conflicting events. Here, building on our previous imaging work of the stop signal task, we introduced a "reward uncertainty" condition to elicit changes in participants' mental sets and examined how individual differences altered the neural responses to salient events. Approximately half of 27 adult participants - the Conservatives - became more risk-aversive in the "reward" as compared to the "standard" condition, by slowing down in go reaction time. We hypothesized that stop errors were more salient for these participants, as compared to the other subjects - the Riskys - who speeded up in go reaction time in the reward as compared to standard condition. With statistical parametric mapping, we showed greater activation of the retrosplenial cortex, somatosensory cortex, pre-supplementary motor area, and thalamus during stop error, in contrast to stop success trials, in the Conservatives as compared to Riskys. These results provided evidence that mental set influences cerebral activations during stop signal performance and extended the potential utility of the stop signal task in elucidating the contextual effects on cognitive control.

Decreased saliency processing as a neural measure of Barratt impulsivity in healthy adults

Cognitive control is necessary to navigating through an uncertain world. With the stop signal task (SST), we measure how cognitive control functions in a controlled environment. There has been conflicting evidence on whether trait impulsivity might reflect differences in cognitive control during the SST. While some studies find that trait impulsivity relates to measures of response inhibition, such as the stop signal reaction time (SSRT), other studies do not. Here, in 92 young adult participants (58 females; age 25 ± 4 years), we examined whether trait impulsivity, measured by the Barratt impulsivity scale (BIS-11), is associated with differences in performance and regional brain activations for the component processes of cognitive control during the SST. Across participants, trait impulsivity showed a trend-level correlation with SSRT (F(1.90)=3.18, p<.07; Pearson regression). In simple regressions, activation of the right anterior dorsal insula and middle frontal cortex (MFC) during stop as compared to go trials negatively correlated with motor and non-planning impulsivity score. Using the generalized form of psychophysiological interaction (gPPI), we showed that functional connectivity of the right insula and MFC with the left dorsolateral prefrontal cortex and bilateral visual areas were also negatively correlated with impulsivity. None of the other component processes of cognitive control, including response inhibition, error processing, post-error slowing, were significantly related to Barratt impulsivity. These results suggest that trait impulsivity as measured by BIS-11 may have distinct effects on saliency processing in adult individuals.

Task-related, low-frequency task-residual, and resting state activity in the default mode network brain regions

The hypothesis of a default mode network (DMN) of brain function is based on observations of task-independent decreases of brain activity during effort as participants are engaged in tasks in contrast to resting. On the other hand, studies also showed that DMN regions activate rather than deactivate in response to task-related events. Thus, does DMN "deactivate" during effort as compared to resting? We hypothesized that, with high-frequency event-related signals removed, the task-residual activities of the DMN would decrease as compared to resting. We addressed this hypothesis with two approaches. First, we examined DMN activities during resting, task residuals, and task conditions in the stop signal task using independent component analysis (ICA). Second, we compared the fractional amplitude of low-frequency fluctuation (fALFF) signals of DMN in resting, task residuals, and task data. In the results of ICA of 76 subjects, the precuneus and posterior cingulate cortex (PCC) showed increased activation during task as compared to resting and task residuals, indicating DMN responses to task events. Precuneus but not the PCC showed decreased activity during task residual as compared to resting. The latter finding was mirrored by fALFF, which is decreased in the precuneus during task residuals, as compared to resting and task. These results suggested that the low-frequency blood oxygen level-dependent signals of the precuneus may represent a useful index of effort during cognitive performance.

Cerebral correlates of skin conductance responses in a cognitive task

Changes in physiological arousal frequently accompany cognitive performance. Many studies sought to identify the neural correlates of heightened arousal as indexed by skin conductance responses (SCR). However, the observed regional activations may be confounded by task events. We addressed this issue by recording SCR in 25 adults performing a stop signal task (SST) during functional magnetic resonance imaging. We compared only go trials with high and low SCR in order to isolate the event-independent processes. Furthermore, we distinguished go trials that followed another go, a stop success, or a stop error trial to examine whether the neural activities are contingent on the local context in which changes in SCR occurred. The results showed that the supplementary motor area responded to increased SCR irrespective of the preceding trial. The dorsal anterior cingulate cortex increased activation to heightened arousal most significantly in response to stop errors. The medial prefrontal cortex increased activation to SCR following a stop error but decreased activation following a go or stop success trial. These new findings specify the regional activations that accompany changes in physiological arousal during the SST and support distinct processes for the changes that occur under different local contexts. In particular, the MPFC shows opposing responses by increasing activation to changes in arousal evoked by salient stimuli and decreasing activation to the control of arousal.

The effects of age on cerebral activations: internally versus externally driven processes

Numerous studies using functional magnetic resonance imaging (fMRI) have described increased or decreased regional brain activations in older as compared to younger adults. This seeming inconsistency may reflect differences in the psychological constructs examined across studies. We hypothesized that behavioral tasks/contrasts engaging internally and externally driven processes are each associated with age-related decreases and increases, respectively, in cerebral activations. We examined the fMRI data of 103 healthy adults, 18–72 years of age, performing a stop signal task (SST), in which a frequent “go” signal triggered a prepotent response and a less frequent “stop” signal prompted inhibition of this response. Greater internally driven processes lead to stop successes (SS) as compared to stop errors (SE), and to speeding up instead of slowing down in go trials. Conversely, externally driven processes contribute to SE trials, which resulted from habitual, unmonitored responses triggered by the go signal (as compared to SS trials), and involved perceptual and cognitive processes elicited by the stop signal (as compared to go trials). Consistent with our hypothesis, the results showed age-related decreases and increases in cerebral activations each during these respective internally and externally driven processes. These findings further elucidate the influence of age on cognitive functioning and provide an additional perspective to understand the imaging literature of aging.