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PubMed2005

Sustained neural activity associated with cognitive control during temporally extended decision making.

Decision making has both cognitive and affective components, but previous neuroimaging studies in this domain predominantly have focused on affect and reward. The current study examined a decision-making paradigm that placed strong demands on cognitive control processes by making reward payoffs contingent upon decision-making history. Payoffs were maximized by choosing the option that, paradoxically, was associated with a lower payoff on the immediate trial. Temporal integration requirements were manipulated by varying, across conditions, the window of previous trials over which the reward function was calculated. The cognitive demands of the task were hypothesized to engage neural systems responsible for integrating and actively maintaining actions and outcomes over time and the top-down biasing of response selection. Brain activation was monitored with functional magnetic resonance imaging (fMRI) using a mixed-blocked and event-related design to extract both transient and sustained neural responses. A network of brain regions commonly associated with cognitive control functions, including bilateral prefrontal cortex (PFC), bilateral parietal cortex, and medial frontal cortex, showed selectively sustained activation during the task. Increasing temporal integration demands led to a shift from transient to sustained activity in additional regions, including right hemisphere dorsolateral and frontopolar PFC. These results demonstrate the contribution of cognitive control mechanisms to temporally extended decision-making paradigms and highlight the benefits of decomposing activation responses into sustained and transient components.

Adult↗

PubMed2005

Is anterior cingulate cortex necessary for cognitive control?

Functional neuroimaging studies in normal humans suggest that dorsal anterior cingulate cortex (dACC) plays an important role in cognitive control. This brain area is reliably activated when tasks require the ongoing adjustment of the allocation of attention. The dACC has come to occupy a central role in theories of attention and cognitive control, which hold that dACC either monitors response conflict, signalling the need for adjustments in cognitive processes, or directly mediates such adjustments. However, functional imaging results cannot establish that a brain area is necessary for a particular cognitive process. This requires evidence from loss-of-function studies. Here we assessed cognitive control in four human subjects with damage to dACC and 12 age- and education-matched control subjects using several measures drawn from the functional imaging literature. All four subjects with dACC damage showed normal adjustments in performance following manipulation of response conflict in both Stroop and go-no go tasks. Furthermore, damage to the dACC did not impair the phenomenon of post-error slowing, nor alter the ability to adjust performance in response to explicit speed or accuracy instructions. Thus, cognitive control, as assessed by four different measures in two different tasks, appears to be intact in these subjects, arguing against a necessary role for dACC in this process.

Adult↗

PubMed2002

Fractionating the neural substrate of cognitive control processes.

Psychological and neurobiological theories of cognitive control must account for flexible, seemless transitions among cognitive operations. When subjects switch between tasks, they must both inhibit the previous task and re-engage in a different task. Inhibition of the disengaged task remains active for a period of time and has to be overcome when re-engaging in the same task. Here we used a task-switching paradigm that allows distinction of two control processes: overcoming the inhibition of a previously performed task when re-engaging it and restarting a sequence of tasks after a period of interruption. Behaviorally, these processes were reflected in the facts that: (i) switching to a recently performed task, that is thus unlikely to have fully recovered from inhibition, takes longer than switching to a task less recently performed and (ii) re-engaging in a sequence of tasks after a period of interruption transiently increases response time. Using event-related functional MRI, we found that these two behavioral effects were accompanied by a double dissociation: the right lateral prefrontal cortex was more activated when switching to a task recently performed compared to a task less recently performed, while the anterior cingulate cortex was recruited when a sequence of tasks was initiated. These results provide insights into the functional organization of the frontal lobe in humans and its role in distinct processes involved in cognitive control.

Adult↗

PubMed2002

The role of cognitive control in mediating the effect of stressful circumstances among Korean immigrants.

The study reported in this article investigated relationships among stressful circumstances, cognitive control (the individual's perception of control over life), and distress among Korean immigrants in the United States. Specifically, it was hypothesized that cognitive control mediated the effect of exposure to stressful circumstances on distress. A total of 159 Korean immigrants participated in the study. The result of the study provided strong support for the role of cognitive control in mediating the relationship between stressful circumstances and distress. The detrimental effect of exposure to stressful circumstances on distress was weakened by cognitive control. Implications for social work practice and future research are discussed.

Acculturation↗

PubMed2005

Cognitive control and semantics in schizophrenia: an integrated approach.

OBJECTIVE: The authors tested whether decisions about incongruencies in the representation and processing of semantic knowledge, thought to be related to cognitive control, are selectively impaired in schizophrenia. METHOD: Twenty-four patients with schizophrenia and 24 healthy comparison subjects determined the relative size of paired stimuli as they are in the real world. Stimuli were words or images. Real-world "distance" (size difference between stimuli) was manipulated within pairs, as was "congruency" between real-world and presentation size. RESULTS: Although patients were slower overall, both groups exhibited similar effects of "distance" and "congruency"; the task was easier when the real-world size difference between stimuli was greater and when stimuli were congruent in presentation and real-world size. CONCLUSIONS: Some aspects of the representation of semantic knowledge are preserved in schizophrenia, and patients use this information to control cognition in the same manner as healthy individuals.

Adult↗

PubMedDate not supplied

Altered brain activation during cognitive control in patients with moderate to severe traumatic brain injury.

BACKGROUND: Persistent deficits in cognitive control have been documented following traumatic brain injury (TBI) but are inconsistently related to the presence and location of focal lesions. OBJECTIVE: Functional magnetic resonance imaging (fMRI) was used to examine brain activation during a cognitive control task in patients with moderate to severe TBI or orthopedic injury (OI). METHODS: Fourteen TBI patients and 10 OI patients underwent fMRI at 3 months postinjury using a stimulus-response compatibility task in which response accuracy and reaction time were measured. Performance between the groups was equated by individually adjusting the amount of training. Groups did not differ in age, gender, or education. RESULTS: Brain activation during stimulus-response incompatibility was greater in TBI patients than in OI patients within the cingulate, medial frontal, middle frontal, and superior frontal gyri. However, the positive regression of activation with response accuracy during stimulus-response incompatibility indicated a stronger relationship for OI patients than the TBI group within the anterior cingulate gyrus, medial frontal, and parietal regions, as well as deep brain structures (eg, brainstem). The number of focal lesions within either the whole brain or within prefrontal areas was not related to brain activation, but there was a relationship between activation and TBI severity. CONCLUSIONS: These findings suggest that neural networks mediating cognitive control are altered after moderate to severe TBI, possibly as a result of diffuse axonal injury, and that the typical relationship of brain activation to performance is disrupted.

Adolescent↗

PubMed2005

Cognitive control mechanisms resolve conflict through cortical amplification of task-relevant information.

A prominent model of how the brain regulates attention proposes that the anterior cingulate cortex monitors the occurrence of conflict between incompatible response tendencies and signals this information to a cognitive control system in dorsolateral prefrontal cortex. Cognitive control is thought to resolve conflict through the attentional biasing of perceptual processing, emphasizing task-relevant stimulus information. It is not known, however, whether conflict resolution is mediated by amplifying neural representations of task-relevant information, inhibiting representations of task-irrelevant information, or both. Here we manipulated trial-by-trial levels of conflict and control during a Stroop task using face stimuli, while recording hemodynamic responses from human visual cortex specialized for face processing. We show that, in response to high conflict, cognitive control mechanisms enhance performance by transiently amplifying cortical responses to task-relevant information rather than by inhibiting responses to task-irrelevant information. These results implicate attentional target-feature amplification as the primary mechanism for conflict resolution through cognitive control.

Adult↗

PubMed2001

Context processing in older adults: evidence for a theory relating cognitive control to neurobiology in healthy aging.

A theory of cognitive aging is presented in which healthy older adults are hypothesized to suffer from disturbances in the processing of context that impair cognitive control function across multiple domains, including attention, inhibition, and working memory. These cognitive disturbances are postulated to be directly related to age-related decline in the function of the dopamine (DA) system in the prefrontal cortex (PFC). A connectionist computational model is described that implements specific mechanisms for the role of DA and PFC in context processing. The behavioral predictions of the model were tested in a large sample of older (N = 81) and young (N = 175) adults performing variants of a simple cognitive control task that placed differential demands on context processing. Older adults exhibited both performance decrements and, counterintuitively, performance improvements that are in close agreement with model predictions.

Adult↗

PubMed2004

Selection, integration, and conflict monitoring; assessing the nature and generality of prefrontal cognitive control mechanisms.

Prefrontal cortex (PFC) supports flexible behavior by mediating cognitive control, though the elemental forms of control supported by PFC remain a central debate. Dorsolateral PFC (DLPFC) is thought to guide response selection under conditions of response conflict or, alternatively, may refresh recently active representations within working memory. Lateral frontopolar cortex (FPC) may also adjudicate response conflict, though others propose that FPC supports higher order control processes such as subgoaling and integration. Anterior cingulate cortex (ACC) is hypothesized to upregulate response selection by detecting response conflict; it remains unclear whether ACC functions generalize beyond monitoring response conflict. The present fMRI experiment directly tested these competing theories regarding the functional roles of DLPFC, FPC, and ACC. Results reveal dissociable control processes in PFC, with mid-DLPFC selectively mediating resolution of response conflict and FPC further mediating subgoaling/integration. ACC demonstrated a broad sensitivity to control demands, suggesting a generalized role in modulating cognitive control.

Adolescent↗

PubMed2005

Intentional false responding shares neural substrates with response conflict and cognitive control.

The ability to deceive others is a high-level social and cognitive function. It has been suggested that response conflict and cognitive control increase during deceptive acts but this hypothesis has not been evaluated directly. Using fMRI, we tested this prediction for the execution of an intentional false response. Subjects were instructed to respond truthfully or falsely to a series of yes/no questions that were also varied in autobiographical and nonautobiographical content to further examine the influence of personal relevance when lying. We observed an interference effect (longer reaction times for false versus true responses) that was accompanied by increased activation within the anterior cingulate, caudate and thalamic nuclei, and dorsolateral prefrontal cortex (DLPFC), a circuit that has been implicated in response conflict and cognitive control. Behavioral and neural effects were more robust when falsifying autobiographical responses relative to nonautobiographical responses. Furthermore, a correlation between reaction time and left caudate activity supported the presence of increased response inhibition when falsifying responses. When presented with self-relevant (autobiographical) stimuli regardless of response condition, the mesial prefrontal and posterior cingulate cortices were recruited. Neural activity within these two regions and the anterior cingulate cortex (ACC) also showed correlations with self-report personality measures from the Psychopathic Personality Inventory (PPI). Overall, we conclude that the process of interference is inherent to the act of falsifying information and that the amount of conflict induced and cognitive control needed to successfully execute false responses is greater when dealing with personal information.

Adult↗

PubMed2005

Goal-directed memory: the role of cognitive control in older adults' emotional memory.

The present study revealed that older adults recruit cognitive control processes to strengthen positive and diminish negative information in memory. In Experiment 1, older adults engaged in more elaborative processing when retrieving positive memories than they did when retrieving negative memories. In Experiment 2, older adults who did well on tasks involving cognitive control were more likely than those doing poorly to favor positive pictures in memory. In Experiment 3, older adults who were distracted during memory encoding no longer favored positive over negative pictures in their later recall, revealing that older adults use cognitive resources to implement emotional goals during encoding. In contrast, younger adults showed no signs of using cognitive control to make their memories more positive, indicating that, for them, emotion regulation goals are not chronically activated.

Affect↗

PubMed1988

Cognitive control of eating.

Eating behaviour, unlike many other biological functions, is often subject to sophisticated cognitive regulation. One of the most widely practised forms of cognitive control over food intake is dieting, i.e. attempting to restrict intake as a means of weight regulation. In this paper the development of dieting will be discussed, followed by an evaluation of the impact of cognitive control on food intake regulation. Cross-sectional studies, comparing dieters with non-dieters, suggest that dieting is linked with a variety of disturbances of food intake control, and that it may even provoke paradoxical overeating. An experimental investigation of the link between cognitive control and paradoxical overeating will also be discussed, along with the implications of this work for the understanding and treatment of eating disorders.

Cognition↗

PubMed2003

Neural correlates of cognitive control and conflict detection in the Stroop and digit-location tasks.

In two experiments, event-related brain potentials were used to examine the neural correlates of cognitive control and conflict processing in the Stroop and digit-location tasks. The relevant dimension was cued on a trial-by-trial basis before stimulus onset. This method allows one to dissociate modulations of the event-related brain potentials (ERPs) associated with cognitive control from modulations of the ERPs associated with conflict processing that are temporally confounded in the standard Stroop task. Cognitive control was associated with a slow wave over the occipital-parietal region that differentiated goal-compatible from goal-incompatible responses in both the Stroop and digit-location tasks. Conflict processing was associated with a N450, in the Stroop task, and a conflict sustained potential (SP) in both tasks. The amplitude of the N450 was similar for color naming and word reading trials. The character of the conflict SP varied over the frontal and central-parietal regions. Over the left lateral frontal region the conflict SP was similar in amplitude across type of response in the Stroop and digit-location tasks. Over the right lateral frontal region the conflict SP was greater in amplitude for the less dominant stimulus dimension (i.e. color or digit). The findings of these experiments clearly demonstrate that different neural systems support cognitive control and conflict processing, with some degree of hemispheric specialization observed for conflict processing.

Adolescent↗

PubMed2006

Dopamine and cognitive control: the influence of spontaneous eyeblink rate, DRD4 exon III polymorphism and gender on flexibility in set-shifting.

Converging evidence suggests a modulatory role of dopamine in cognitive control. We investigated the influence of two correlates of dopaminergic activity, the spontaneous eyeblink rate and the DRD4 exon III polymorphism, and the potential impact of gender on flexibility in an attentional set-shifting paradigm. The objective of the study was to confirm previous findings of an association between high eyeblink rates and increased cognitive flexibility. These findings were replicated in 87 healthy volunteers this time using a continuous variable for eyeblink rates instead of a dichotomized variable. The interaction between eyeblink rate and DRD4 found in the previous study was lower and failed significance. Analysis of the collapsed sample of n=150 revealed a main effect of gender and an interaction of gender and eyeblink rate on cognitive control. The complete prediction model explained 26% of the total variance. These data suggest that (1) the eyeblink rate is a reliable predictor of dopamine-mediated flexibility of cognitive control and (2) it is useful to include gender as predictor in future studies of dopaminergic modulation of cognitive control.

Adolescent↗

PubMed2005

Involvement of the inferior frontal junction in cognitive control: meta-analyses of switching and Stroop studies.

There is growing evidence that a specific region in the posterior frontolateral cortex is involved intimately in cognitive control processes. This region, located in the vicinity of the junction of the inferior frontal sulcus and the inferior precentral sulcus, was termed the inferior frontal junction (IFJ). The IFJ was shown to be involved in the updating of task representations and to be activated commonly in a within-subject investigation of a task-switching paradigm, the Stroop task, and a verbal n-back task. Here, we investigate the involvement of the IFJ in cognitive control by employing a meta-analytic approach. Two quantitative meta-analyses of functional magnetic resonance imaging (fMRI) studies were conducted. One meta-analysis included frontal activations from task-switching, set-shifting, and stimulus-response (S-R) reversal studies, the other included frontal activations from color-word Stroop studies. Results showed highly significant clustering of activations in the IFJ in both analyses. These results provide strong evidence for the consistent involvement of the IFJ in both switching and Stroop paradigms. Furthermore, they support our concept of areal specialization in the frontolateral cortex, which posits that it is not only the middorsolateral part that plays an important role in cognitive control, but also the IFJ. Finally, our results demonstrate how quantitative meta-analyses can be used to test hypotheses about the involvement of specific brain regions in cognitive control.

Brain Mapping↗

PubMed1996

A computational approach to prefrontal cortex, cognitive control and schizophrenia: recent developments and current challenges.

In this chapter we consider the mechanisms involved in cognitive control-from both a computational and a neurobiological perspective- and how these might be impaired in schizophrenia. By 'control', we mean the ability of the cognitive system to flexibly adapt its behaviour to the demands of particular tasks, favouring the processing of task-relevant information over other sources of competing information, and mediating task-relevant behaviour over habitual, or otherwise prepotent responses. There is a large body of evidence to suggest that the prefrontal cortex (PFC) plays a critical role in cognitive control. In previous work, we have used a computational framework to understand and develop explicit models of this function of PFC, and its impairment in schizophrenia. This work has lead to the hypothesis that PFC houses a mechanism for representing and maintaining context information. We have demonstrated that this mechanism can account for the behavioural inhibition and active memory functions commonly ascribed to PFC, and for human performance in simple attention, language and memory tasks that draw upon these functions for cognitive control. Furthermore, we have used our models to simulate detailed patterns of cognitive deficit observed in schizophrenia, an illness associated with marked disturbances in cognitive control, and well established deficits of PFC. Here, we review results of recent empirical studies that test predictions made by our models regarding schizophrenic performance in tasks designed specifically to probe the processing of context. These results showed selective schizophrenic deficits in tasks conditions that placed the greatest demands on memory and inhibition, both of which we have argued rely on the processing of context. Furthermore, we observed predicted patterns of deterioration in first episode vs multi-episode patients. We also discuss recent developments in our computational work, that have led to refinements of the models that allow us to simulate more detailed aspects of task performance, such as reaction time data and manipulations of task parameters such as interstimulus delay. These refined models make several provocative new predictions, including conditions in which schizophrenics and control subjects are expected to show similar reaction time performance, and we provide preliminary data in support of these predictions. These successes notwithstanding, our theory of PFC function and its impairment in schizophrenia is still in an early stage of development. We conclude by presenting some of the challenges to the theory in its current form, and new directions that we have begun to take to meet these challenges. In particular, we focus on refinements concerning the mechanisms underlying active maintenance of representations within PFC, and the characteristics of these representations that allow them to support the flexibility of cognitive control exhibited by normal human behaviour. Taken in toto, we believe that this work illustrates the value of a computational approach for understanding the mechanisms responsible for cognitive control, at both the neural and psychological levels, and the specific manner in which they break down in schizophrenia.

Cognition↗

PubMed2004

Attention and cognitive control as emergent properties of information representation in working memory.

A hallmark of primate, and particularly human, behavior is cognitive control, the ability to integrate information from a multitude of sources and use that information to flexibly guide behavior in order to achieve an infinite number of goals. The neural mechanisms of cognitive control have yet to be fully elucidated, although the prefrontal cortex is known to play a critical role. Here, I review evidence suggesting that a unifying principle regarding the role of various portions of the prefrontal cortex in a wide range of cognitive tasks is the active maintenance in working memory of different types of currently relevant information-from specific stimulus features, to instructional cues, to motivational goals and contexts. I argue that the key to demonstrating the existence of this domain-dependent organization lies in a better understanding of the nature of the representation of this information and the ways in which this information itself controls cognition and behavior.

Attention↗

PubMed2006

Suppression of emotional and nonemotional content in memory: effects of repetition on cognitive control.

Two experiments utilized a think/no-think paradigm to examine whether cognitive control of memories differs depending on whether they contain information with negative or neutral emotional content. During a training phase, participants learned face-word pairs (Experiment 1) or face-picture pairs (Experiment 2). In a subsequent experimental phase, participants were shown faces and told to think of the items paired with some of the faces and to try not to think of the items paired with other faces. Finally, in a test phase, participants were again shown each face and asked to recall the item with which it had been paired previously. Results for both verbal (Experiment 1) and nonverbal (Experiment 2) items indicated that the facilitatory and inhibitory influences of cognitive control were larger for negative than neutral items.

Adult↗