The counting stroop: An interference task specialized for functional neuroimaging-validation study with functional MRI

Cholinergic agonism alters cognitive processing and enhances brain functional connectivity in patients with multiple sclerosis

The aim of this study is to define mechanisms underlying the pharmacological effects of brain cholinesterase inhibition on cognitive function in patients with multiple sclerosis (MS). Both a Stroop task and an N-back task were used to probe the changes in brain activity using functional magnetic resonance imaging (fMRI) in a single (investigator)-blind, crossover treatment design studying 15 patients with multiple sclerosis (12 relapsing remitting, 3 secondary progressive) taking rivastigmine (4.5 mg po bid) and domperidone (10 mg po qd) or domperidone alone. Administration of rivastigmine increased Stroop functional magnetic resonance imaging activation in the right inferior frontal gyrus for the Stroop task (P < 0.05, corrected). Incremental functional magnetic resonance imaging activation with progressively greater N-back task difficulty was enhanced by rivastigmine in prefrontal and parietal cortical regions (P < 0.01, ANOVA). Functional connectivity analysis of the N-back functional magnetic resonance imaging data based on correlations between pair-wise interregional activations showed increased connectivity between left to right prefrontal, anterior cingulate to left prefrontal and right parietal to right prefrontal regions with rivastigmine (P < 0.05, corrected). Although there were no statistically significant changes in the neuropsychological task performance with rivastigmine in this small study, 11 of 15 patients showed improvements, whereas only 4 of 15 patients showed decline in performance (P = 0.07). With regard to the previous data, these findings suggest different patterns of brain response to lower dose acute and higher dose chronic administration of rivastigmine in patients with multiple sclerosis. They showed that rivastigmine enhances the prefrontal function and alters the functional connectivity associated with cognition. We interpret this as evidence for greater efficiency of brain information transfer that should increase confidence in a potentially beneficial clinical therapeutic effect.

Brain and autonomic association accompanying stochastic decision-making

To examine the functional association between brain and autonomic activities accompanying decision-making, we simultaneously recorded regional cerebral blood flow using (15)O-water positron emission tomography and event-related brain potentials (ERPs) time-locked to feedback of reward and punishment, as well as cardiovascular parameters, during a stochastic decision-making task. We manipulated the uncertainty of outcomes in the task; specifically, we compared a condition with high predictability of reward/punishment (contingent-reward condition) and a condition with low predictability of reward/punishment (random-reward condition). The anterior cingulate cortex (ACC) was commonly activated in both conditions. Compared with the contingent-reward condition, the orbitofrontal and right dorsolateral prefrontal cortices and dorsal striatum were activated in the random-reward condition, where subjects had to continue to seek contingency between stimuli and reward/punishment. Activation of these brain regions correlated with a positive component of ERPs locked to feedback signals (feedback-related positivity), which showed an association with behavioral decision-making in the contingent-reward condition. Furthermore, cardiovascular responses were attenuated in the random-reward condition, where continuous attention and contingency monitoring were needed, and such attenuation of cardiovascular responses was mediated by vagal activity that was governed by the rostral ACC. These findings suggest that the prefrontal-striatal network provides a neural basis for decision-making and modulation over the peripheral autonomic activity accompanying decision-making.

Changes in performance monitoring during sensorimotor adaptation

Error detection and correction are essential components of motor skill learning. These processes have been well characterized in cognitive psychology using electroencephalography (EEG) to record an event-related potential (ERP) called error-related negativity (ERN). However, it is unclear whether this ERP component is sensitive to the magnitude of the error made in a sensorimotor adaptation task. In the present study, we tested the function of error-related activity in a visuomotor adaptation task. To examine whether error size is reflected in the ERP, two groups of participants adapted manual aiming movements to either a small (30 degrees) or large (45 degrees) rotation of the visual feedback display. Each participant's trials were sorted into large and small error trials using a median split to examine potential error magnitude waveform differences. We also examined these trial types at the early and late stages of adaptation. There were no group differences for the behavioral or neural measures; however, waveforms from large error trials were significantly different from small error trials. The waveforms also changed as a function of practice as early adaptation waveforms were larger than late adaptation waveforms. The observed ERP component reflected differences in error magnitude with the amount of activity corresponding to the size of the error. Movement monitoring potentials likely affected the frequency and time course of the waveform so that it did not resemble the typical ERN; however, error-related activity was still distinguishable. The present findings are discussed in terms of current theories of the ERN as well as skill acquisition.

The effect of acute tryptophan depletion on performance and the BOLD response during a Stroop task in healthy first-degree relatives of patients with unipolar depression

Previous research has shown that low central serotonin, induced by acute tryptophan depletion (ATD), results in depressed mood and impairs cognition in healthy volunteers with a predisposition for depression. It remains unknown whether ATD affects emotional processing via mood changes or directly. In the present study we investigated the interaction between vulnerability for depression and the effect of ATD on mood, cognition and the associated brain activation. In a previous functional MRI study, we tested the effect of ATD during a combined cognitive and emotional Stroop task in healthy women without a family history of depression (FH-). In this study, we present the data of an additional group of 12 healthy women with a positive family history of unipolar depression (FH+). The effect of ATD on mood and Stroop performance was different for the FH+ group as compared with the FH- group. Scores on the depression sub-scale of the Profile of Mood States (POMS) did not correlate with performance changes, but did correlate with the anterior cingulate cortex response during Stroop interference. This study showed that a family history of unipolar depression interacts with the effect of ATD.

Executive cognitive functions and impulsivity as correlates of risk taking and problem behavior in preadolescents

Initiation of drug use and other risky behavior in preadolescence is associated with poor developmental outcomes. In this research, we examine models that ascribe the trajectory to (a) weak executive cognitive function (ECF), (b) early manifestation of externalizing problems, or (c) heightened levels of trait impulsivity. We test the explanatory power of these factors in a structural equation model with a community sample of 387 preadolescents ages 10-12 years. Participants were tested with a computerized battery of tasks to assess three facets of ECF (working memory, cognitive control, and reward processing) as well as with an audio assisted computerized self-interview to obtain reports of impulsivity and risk behaviors (use of cigarettes and alcohol as well as engaging in fighting and gambling for money) and a self-administered questionnaire to assess externalizing and internalizing problems. The best fitting model explained both early risk taking and externalizing symptoms as the result of individual differences in impulsivity. Although no ECF was directly related to risk taking, working memory and one measure of reward processing performance (reversal learning) were inversely related to impulsivity. The results are discussed in regard to theories of early risk taking with particular focus on the potential relation between ECF and impulsive behavior tendencies and the implications for early intervention to prevent the dysfunctional trajectory associated with early risk behavior.

Quantitative MRI of the prefrontal cortex and executive function in patients with temporal lobe epilepsy

We investigated the relationship between prefrontal cortex (PFC) and hippocampal volume and executive functioning in patients with temporal lobe epilepsy (TLE). Prefrontal volume and hippocampal volume were studied using stereology in conjunction with point counting and voxel-based morphometry on MR images. Executive functioning was assessed using tests routinely incorporated into presurgical neuropsychological evaluation. Relative to 30 healthy controls, 43 patients (26 left, 17 right) with TLE had volume atrophy of the ipsilateral hippocampus and bilateral dorsal PFC. Performance on the working memory index of the Wechsler Memory Scale was positively correlated with the volume of all prefrontal regions, and the Controlled Oral Word Association Test with the left dorsal PFC, whole left PFC, and left hippocampus. Stroop Color-Word Interference performance was not related to volume of dorsal PFC. The "extratemporal neuropsychological profile" frequently observed in patients with TLE may be due to extended damage to brain regions remote from the epileptogenic focus. In particular, volume atrophy of the dorsal PFC may account for deficits in executive functioning.

Aberrant functional activation in school age children at-risk for mathematical disability: a functional imaging study of simple arithmetic skill

We used functional magnetic resonance imaging (fMRI) to explore the patterns of brain activation associated with different levels of performance in exact and approximate calculation tasks in well-defined cohorts of children with mathematical calculation difficulties (MD) and typically developing controls. Both groups of children activated the same network of brain regions; however, children in the MD group had significantly increased activation in parietal, frontal, and cingulate cortices during both calculation tasks. A majority of the differences occurred in anatomical brain regions associated with cognitive resources such as executive functioning and working memory that are known to support higher level arithmetic skill but are not specific to mathematical processing. We propose that these findings are evidence that children with MD use the same types of problem solving strategies as TD children, but their weak mathematical processing system causes them to employ a more developmentally immature and less efficient form of the strategies.

Neural correlates of the individual emotional Stroop in borderline personality disorder

OBJECTIVE

Emotional dysregulation is a key feature of borderline personality disorder (BPD) with altered inhibitory functions having suggested as being crucial. The anterior cingulate cortex and further prefrontal brain regions are crucial for response inhibition. The regulation of emotions is ensured via inhibitory control over the amygdala. The present study aimed to investigate neural correlates of response inhibition in BPD by using an emotional Stroop paradigm extending the task to word stimuli which were related to stressful life events.

METHODS

Twenty BPD patients and 20 healthy controls underwent functional magnetic resonance imaging (fMRI) while performing the individual emotional Stroop task. A block design was used with the following word type conditions: neutral words, general negative words, and individual negative words. The individual negative words were recruited from a prior interview conducted with each participant.

RESULTS

While BPD patients had overall slower reaction times in the Stroop task compared to healthy controls, there was no increased slowing with emotional interference. Controls exhibited significant fMRI blood oxygenation level-dependent signal increases in the anterior cingulate cortex as well as in frontal cortex contrasting generally negative vs. neutral and individual negative vs. neutral conditions, respectively. BPD patients did not show equivalent signal changes.

CONCLUSIONS

These results provide further evidence for a dysfunctional network of brain areas in BPD, including the ACC and frontal brain regions. These areas are crucial for the regulation of stress and emotions, the core problems of BPD patients.

Cortico-limbic response to personally challenging emotional stimuli after complete recovery from depression

People vulnerable to depression are at increased risk of relapse if they live in highly critical family environments. To explore this link, we used neuroimaging methods to examine cortico-limbic responding to personal criticisms in healthy participants and participants with known vulnerability to major depression. Healthy controls and fully recovered participants with a past history of major depression were scanned while they heard praising, critical, and neutral comments from their own mothers. Prior to scanning, the formerly depressed and the control participants were indistinguishable with respect to self-reported positive, negative, or anxious mood. They also reported similar mood changes after being praised or criticized. However, formerly depressed participants responded to criticism with greater activation in the amygdala and less activation in the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) than did controls. During praise and neutral commentary, amygdala activation was comparable in both groups, although lower levels of activation in the DLPFC and ACC still characterized formerly depressed participants. Vulnerability to depression may be associated with abnormalities in cortico-limbic activation that are independent of mood state and that remain even after full recovery. Criticism may be a risk factor for relapse because it activates the amygdala and perturbs the affective circuitry that underlies depression.

Dissociating early and late error signals in perceptual recognition

Decisions about object identity follow a period in which evidence is gathered and analyzed. Evidence can consist of both task-relevant external stimuli and internally generated goals and expectations. How the various pieces of information are gathered and filtered into meaningful evidence by the nervous system is largely unknown. Although object recognition is often highly efficient and accurate, errors are common. Errors may be related to faulty evidence gathering arising from early misinterpretations of incoming stimulus information. In addition, errors in task performance are known to elicit late corrective performance monitoring mechanisms that can optimize or otherwise adjust future behavior. In this study, we used functional magnetic resonance imaging (fMRI) in an extended trial paradigm of object recognition to study whether we could identify performance-based signal modulations prior to and following the moment of recognition. The rationale driving the current report is that early modulations in fMRI activity may reflect faulty evidence gathering, whereas late modulations may reflect the presence of performance monitoring mechanisms. We tested this possibility by comparing fMRI activity on correct and error trials in regions of interest (ROIs) that were selected a priori. We found pre- and postrecognition accuracy-dependent modulation in different sets of a priori ROIs, suggesting the presence of dissociable error signals.

Task-related dissociation in ERN amplitude as a function of obsessive-compulsive symptoms

Hyperactive cortico-striatal circuits including the anterior cingulate cortex (ACC) have been implicated to underlie obtrusive thoughts and repetitive behaviors in obsessive-compulsive disorder (OCD). Larger error-related negativities (ERNs) in OCD patients during simple flanker tasks have been proposed to reflect an amplified error signal in these hyperactive circuits. Such amplified error signals typically are associated with an adaptive change in response, yet in OCD these same repetitive responses persist to the point of distress and impairment. In contrast to this repetitive character of OC behavior, larger ERN amplitudes have been linked to better avoidance learning in reinforcement learning tasks. Study I thus investigated if OC symptomatology in non-patients predicted an enhanced ERN after suboptimal choices in a probabilistic learning task. Absent any behavioral differences, higher OC symptoms predicted smaller ERNs. Study II replicated this effect in an independent sample while also replicating findings of a larger ERN in a flanker task. There were no relevant behavioral differences in reinforcement learning or error monitoring as a function of symptom score. These findings implicate different, yet overlapping neural mechanisms underlying the negative deflection in the ERP following the execution of an erroneous motor response and the one following a suboptimal choice in a reinforcement learning paradigm. OC symptomatology may be dissociated in these neural systems, with hypoactivity in a system that enables learning to avoid maladaptive choices, and hyperactivity in another system that enables the same behavior to be repeated when it was assessed as not quite good enough the first time.

Cortico-limbic response to personally challenging emotional stimuli after complete recovery from depression

People vulnerable to depression are at increased risk of relapse if they live in highly critical family environments. To explore this link, we used neuroimaging methods to examine cortico-limbic responding to personal criticisms in healthy participants and participants with known vulnerability to major depression. Healthy controls and fully recovered participants with a past history of major depression were scanned while they heard praising, critical, and neutral comments from their own mothers. Prior to scanning, the formerly depressed and the control participants were indistinguishable with respect to self-reported positive, negative, or anxious mood. They also reported similar mood changes after being praised or criticized. However, formerly depressed participants responded to criticism with greater activation in the amygdala and less activation in the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) than did controls. During praise and neutral commentary, amygdala activation was comparable in both groups, although lower levels of activation in the DLPFC and ACC still characterized formerly depressed participants. Vulnerability to depression may be associated with abnormalities in cortico-limbic activation that are independent of mood state and that remain even after full recovery. Criticism may be a risk factor for relapse because it activates the amygdala and perturbs the affective circuitry that underlies depression.

Correlation between prepulse inhibition and cortical perfusion during an attentional test in schizophrenia. A pilot study

BACKGROUND

Processes underlying cortical hypoactivation in schizophrenia are poorly understood but some evidence suggests that a deficient sensory filtering is associated with the condition. This filtering deficit can be studied by using measures of prepulse inhibition (PPI) of the startle reflex.

OBJECTIVE

To evaluate the contribution of sensory filtering deficits to cortical hypoperfusion during an attention test in schizophrenia.

METHOD

Measurements of PPI of the startle reflex and perfusion during the performance of a Stroop test (assessed with single photon emission tomography) were obtained in 10 acutely treated schizophrenia patients (6 with recent onset, RO) and 16 control subjects. These measurements were compared between patients and controls and the correlation between PPI and perfusion was evaluated within each group, using Statistical Parametric Mapping.

RESULTS

In comparison with normal subjects, the patients exhibited lower PPI, although the difference was not statistically significant. Perfusion was significantly lower in the prefrontal and premotor regions of the patients. In the patient group, a statistically significant difference was observed between PPI and perfusion in the parietal, premotor, and cingulate regions. When the associations were analyzed in the RO patients alone, a positive correlation was also found between prefrontal perfusion and PPI, while anterior hippocampal perfusion was inversely related to PPI.

CONCLUSIONS

These results support the notion that deficient sensory-motor filtering is associated with decreased cortical task-related activation in schizophrenia.

Differences in Duration of Eye Fixation for Conditions in a Numerical Stroop-Effect Experiment

Durations of eye fixation were recorded for a numerical Stroop effect experiment. Participants (6 men, 19 women; M age = 22 yr.) reported the number of characters present in sequences of variable length (2 to 5 characters) while attempting to ignore the identity of the character. Three conditions were included: congruent (the number of characters and the numeral were matched, e.g., responding “two” to 22), incongruent (the number of characters and the numeral were mismatched, e.g., responding “two” to 55), and control (baseline of stimuli made up of “X”s, e.g., responding “two” to XX). Comparisons among the three conditions produced the longest response times and average durations of fixation for the incongruent condition. The shortest response times and average durations of fixation were obtained for the congruent condition.

An ERP investigation of the Stroop task: the role of the cingulate in attentional allocation and conflict resolution

The majority of studies support a role of the anterior cingulate cortex (ACC) in the attentional control necessary for conflict resolution in the Stroop task; however, the time course of activation and the neural substrates underlying the Stroop task remain contentious. We used high-density EEG to record visual-evoked potentials from 16 healthy subjects while performing a manual version of the traditional Stroop colour-word task. Difference waveforms for congruent-control and incongruent-control conditions were similar in amplitude and had a similar spatial distribution in the time window of 260-430 ms post stimulus onset. Source estimation indicated particularly middle cingulate involvement in congruent-control and incongruent-control difference waveforms. In contrast, the difference waveform for the incongruent-congruent contrast was observed later (in the time window of 370-480 ms), had a different spatial distribution, and source estimation indicated that the anterior cingulate underlies this difference waveform. As congruent-control and incongruent-control differences have a similar timeframe and cingulate source, we propose that this indicates early attentional allocation processes. That is, the identification of two sources of information (the word and the colour it is printed in) and the selective attention to one. The later peak in the incongruent-congruent difference wave, originating in anterior cingulate, likely reflects identification (and subsequent resolution) of conflict in the two sources of information.

Alexithymic trait and voluntary control in healthy adults

BACKGROUND

Alexithymia is a personality trait characterized by deficiency in understanding, processing, or describing emotions. Recent studies have revealed that alexithymia is associated with less activation of the anterior cingulate cortex, a brain region shown to play a role in cognitive and emotional processing. However, few studies have directly investigated the cognitive domain in relation to alexithymia to examine whether alexithymic trait is related to less efficient voluntary control.

METHODOLOGY/PRINCIPAL FINDINGS

We examined the relationship between alexithymic trait and voluntary control in a group of healthy volunteers. We used the 20-item Toronto Alexithymia Scale (TAS-20) to measure alexithymic trait. Additionally, we examined state and trait voluntary control using the revised Attention Network Test (ANT-R) and the Adult Temperament Questionnaire (ATQ), respectively. Alexithymic trait was positively correlated with the overall reaction time of the ANT-R, and negatively correlated with the Effortful Control factor of the ATQ.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that alexithymic trait is associated with less efficient voluntary control.

Towards a cognitive model of distraction by auditory novelty: the role of involuntary attention capture and semantic processing

Unexpected auditory stimuli are potent distractors, able to break through selective attention and disrupt performance in an unrelated visual task. This study examined the processing fate of novel sounds by examining the extent to which their semantic content is analyzed and whether the outcome of this processing can impact on subsequent behavior. This issue was investigated across five laboratory experiments in which participants categorized visual left and right arrows while instructed to ignore irrelevant sounds. The results showed that auditory novels that were incongruent with the visual target (e.g., word "left" presented before a right arrow) disrupted performance over and above congruent novels (semantic effect) while both types of novels delayed responses in the visual task compared to a standard sound (novelty effect). No semantic effect was observed for congruent and incongruent standards, suggesting that novelty detection is necessary for involuntary semantic processing to unravel. While the novelty effect augmented as the difference between novels and the standard increased, the semantic effect was immune to this variation. Furthermore, the novelty effect decreased across the task while the semantic effect did not. A general cognitive framework is proposed encompassing these new findings and previous work in an attempt to account for the behavioral impact of irrelevant auditory novels on primary task performance.

Conflict-related activity in the caudal anterior cingulate cortex in the absence of awareness

The caudal anterior cingulate cortex (cACC) is thought to be involved in performance monitoring, as conflict and error-related activity frequently co-localize in this area. Recent results suggest that these effects may be differentially modulated by awareness. To clarify the role of awareness in performance monitoring by the cACC, we used rapid event-related fMRI to examine the cACC activity while subjects performed a dual task: a delayed recognition task and a serial response task (SRT) with an implicit probabilistic learning rule (i.e. the stimulus location followed a probabilistic sequence of which the subjects were unaware). Task performance confirmed that the location sequence was learned implicitly. Even though we found no evidence of awareness for the presence of the sequence, imaging data revealed increased cACC activity during correct trials which violated the sequence (high-conflict), relative to trials when stimuli followed the sequence (low conflict). Errors made with awareness also activated the same brain region. These results suggest that the performance monitoring function of the cACC extends beyond detection of errors made with or without awareness, and involves detection of multiple responses even when they are outside of awareness.

Cognitive control mechanisms, emotion and memory: a neural perspective with implications for psychopathology

In this paper we provide a focused review of the literature examining neural mechanisms involved in cognitive control over memory processes that can influence, and in turn are influenced by, emotional processes. The review is divided into two parts, the first focusing on working memory and the second on long-term memory. With regard to working memory, we discuss the neural bases of (1) control mechanisms that can select against distracting emotional information, (2) mechanisms that can regulate emotional reactions or responses, (3) how mood state influences cognitive control, and (4) individual differences in control mechanisms. For long-term memory, we briefly review (1) the neural substrates of emotional memory, (2) the cognitive and neural mechanisms that are involved in controlling emotional memories and (3) how these systems are altered in post-traumatic stress disorder. Finally, we consider tentative generalizations that can be drawn from this relatively unexplored conjunction of research endeavors.

Fronto-cingulate effective connectivity in major depression: a study with fMRI and dynamic causal modeling

Functional imaging studies are indicating disrupted error monitoring and executive control in a fronto-cingulate network in major depression. However, univariate statistical analyses allow only for a limited assessment of directed neuronal interactions. Therefore, the present study used dynamic causal modeling (DCM) of a fronto-cingulate network to re-analyze the data from a preceding fMRI study in 16 drug-free patients with major depression and 16 healthy controls using the Stroop Color-Word Test (Wagner et al., 2006). In both groups, a significant reciprocal interregional connectivity was found in a cognitive control network including prefrontal cortex (PFC) and dorsal anterior cingulate cortex (ACC). With regard to intrinsic connections we detected a significant difference for dorsal to rostral ACC connectivity between depressive patients and controls in terms of higher connectivity in patients. Additionally, a task by group interaction was observed for the bilinear interaction signaling enhanced task-related input from the dorsal to rostral ACC in subjects with depression. This could be related to the inability of patients to down-regulate rostral ACC activation as observed in the previous univariate analysis. The correlation between interference scores and intrinsic connections from dorsal ACC to dorsolateral PFC (DLPFC) was significant for both groups together, but no significant group differences in correlations could be detected. Thus, the observed relationship between control functions of the dorsal ACC exerted over DLPFC and interference scores appears to be valid in both patients with depression and controls. The findings are consistent with current models of a differential involvement of the fronto-cingulate system in the pathophysiology of major depression.

Altered prefrontal function with aging: insights into age-associated performance decline

We examined the effects of aging on visuo-spatial attention. Participants performed a bi-field visual selective attention task consisting of infrequent target and task-irrelevant novel stimuli randomly embedded among repeated standards in either attended or unattended visual fields. Blood oxygenation level dependent (BOLD) responses to the different classes of stimuli were measured using functional magnetic resonance imaging. The older group had slower reaction times to targets, and committed more false alarms but had comparable detection accuracy to young controls. Attended target and novel stimuli activated comparable widely distributed attention networks, including anterior and posterior association cortex, in both groups. The older group had reduced spatial extent of activation in several regions, including prefrontal, basal ganglia, and visual processing areas. In particular, the anterior cingulate and superior frontal gyrus showed more restricted activation in older compared with young adults across all attentional conditions and stimulus categories. The spatial extent of activations correlated with task performance in both age groups, but the regional pattern of association between hemodynamic responses and behavior differed between the groups. Whereas the young subjects relied on posterior regions, the older subjects engaged frontal areas. The results indicate that aging alters the functioning of neural networks subserving visual attention, and that these changes are related to cognitive performance.

Functional brain abnormalities in psychiatric disorders: neural mechanisms to detect and resolve cognitive conflict and interference

In the present article, we review functional neuroimaging studies on interference processing and performance monitoring in three groups of psychiatric disorders, (1) mood disorders, (2) schizophrenia, and (3) obsessive-compulsive disorder (OCD). Ad (1) Behavioral performance measures suggest an impaired interference resolution capability in symptomatic bipolar disorder patients. A series of neuroimaging analyses found alterations in the ACC-DLPFC system in mood disorder (unipolar depressed and bipolar) patients, putatively reflective of an abnormal interplay of monitoring and executive neurocognitive functions. Other studies of euthymic bipolar patients showed relatively decreased interference-related activation in rostroventral PFC which conceivably underlies defective inhibitory control. Ad (2) Behavioral Stroop studies revealed a specific performance pattern of schizophrenia patients (normal RT interference but increased error interference and RT facilitation) suggestive of a deficit in ignoring irrelevant (word) information. Moreover, reduced/absent behavioral post-error and post-conflict adaptation effects suggest alterations in performance monitoring and/or adjustment capability in these patients. Neuroimaging findings converge to suggest a disorder-related abnormal neurophysiology in ACC which consistently showed conflict- and error-related hypoactivation that, however, appeared to be modulated by different factors. Moreover, studies suggest a specific deficit in context processing in schizophrenia, evidently related to activation reduction in DLPFC. Ad (3) Behavioral findings provide evidence for impaired interference resolution in OCD. Neuroimaging results consistently showed conflict- and error-related ACC hyperactivation which--conforming OCD pathogenesis models--can be conclusively interpreted as reflecting overactive performance monitoring. Taken together, interference resolution and performance monitoring appeared to be fruitful concepts in the investigation of neurocognitive deficits in psychiatric disorders.

Response inhibition and response selection: two sides of the same coin

Response inhibition refers to the suppression of actions that are inappropriate in a given context and that interfere with goal-driven behavior. Studies using a range of methodological approaches have implicated executive control processes mediated by frontal-subcortical circuits as being critical to response inhibition; however, localization within the frontal lobe has been inconsistent. In this review, we present evidence from behavioral, lesion, neuroimaging, electrophysiology, and neurological population studies. The findings lay the foundation for a construct in which response inhibition is akin to response selection, such that pre-SMA circuits are critical to selection of appropriate behavior, including both selecting to engage appropriate motor responses and selecting to withhold (inhibit) inappropriate motor responses. Recruitment of additional prefrontal and posterior cortical circuits, necessary to guide response selection, varies depending on the cognitive and behavioral demands of the task.

Response monitoring, repetitive behaviour and anterior cingulate abnormalities in autism spectrum disorders (ASD)

Autism spectrum disorders (ASD) are characterized by inflexible and repetitive behaviour. Response monitoring involves evaluating the consequences of behaviour and making adjustments to optimize outcomes. Deficiencies in this function, and abnormalities in the anterior cingulate cortex (ACC) on which it relies, have been reported as contributing factors to autistic disorders. We investigated whether ACC structure and function during response monitoring were associated with repetitive behaviour in ASD. We compared ACC activation to correct and erroneous antisaccades using rapid presentation event-related functional MRI in 14 control and ten ASD participants. Because response monitoring is the product of coordinated activity in ACC networks, we also examined the microstructural integrity of the white matter (WM) underlying this brain region using diffusion tensor imaging (DTI) measures of fractional anisotropy (FA) in 12 control and 12 adult ASD participants. ACC activation and FA were examined in relation to Autism Diagnostic Interview-Revised ratings of restricted and repetitive behaviour. Relative to controls, ASD participants: (i) made more antisaccade errors and responded more quickly on correct trials; (ii) showed reduced discrimination between error and correct responses in rostral ACC (rACC), which was primarily due to (iii) abnormally increased activation on correct trials and (iv) showed reduced FA in WM underlying ACC. Finally, in ASD (v) increased activation on correct trials and reduced FA in rACC WM were related to higher ratings of repetitive behaviour. These findings demonstrate functional and structural abnormalities of the ACC in ASD that may contribute to repetitive behaviour. rACC activity following errors is thought to reflect affective appraisal of the error. Thus, the hyperactive rACC response to correct trials can be interpreted as a misleading affective signal that something is awry, which may trigger repetitive attempts at correction. Another possible consequence of reduced affective discrimination between error and correct responses is that it might interfere with the reinforcement of responses that optimize outcomes. Furthermore, dysconnection of the ACC, as suggested by reduced FA, to regions involved in behavioural control might impair on-line modulations of response speed to optimize performance (i.e. speed-accuracy trade-off) and increase error likelihood. These findings suggest that in ASD, structural and functional abnormalities of the ACC compromise response monitoring and thereby contribute to behaviour that is rigid and repetitive rather than flexible and responsive to contingencies. Illuminating the mechanisms and clinical significance of abnormal response monitoring in ASD represents a fruitful avenue for further research.

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

Cognitive control over conflicting information has been studied extensively using tasks such as the color-word Stroop, flanker, and spatial conflict task. Neuroimaging studies typically identify a fronto-parietal network engaged in conflict processing, but numerous additional regions are also reported. Ascribing putative functional roles to these regions is problematic because some may have less to do with conflict processing per se, but could be engaged in specific processes related to the chosen stimulus modality, stimulus feature, or type of conflict task. In addition, some studies contrast activation on incongruent and congruent trials, even though a neutral baseline is needed to separate the effect of inhibition from that of facilitation. In the first part of this article, we report a systematic review of 34 neuroimaging publications, which reveals that conflict-related activity is reliably reported in the anterior cingulate cortex and bilaterally in the lateral prefrontal cortex, the anterior insula, and the parietal lobe. In the second part, we further explore these candidate "conflict" regions through a novel functional magnetic resonance imaging experiment, in which the same group of subjects perform related visual and auditory Stroop tasks. By carefully controlling for the same task (Stroop), the same to-be-ignored stimulus dimension (word meaning), and by separating out inhibitory processes from those of facilitation, we attempt to minimize the potential differences between the two tasks. The results provide converging evidence that the regions identified by the systematic review are reliably engaged in conflict processing. Despite carefully matching the Stroop tasks, some regions of differential activity remained, particularly in the parietal cortex. We discuss some of the task-specific processes which might account for this finding.

Atypical recruitment of medial prefrontal cortex in autism spectrum disorders: an fMRI study of two executive function tasks

Recent studies have suggested an uneven profile of executive dysfunction in autism spectrum disorders (ASD). For example, some authors have reported deficits on newly developed tests of executive function sensitive to rostral prefrontal function, despite spared, or even superior, performance on other tests. We investigated the performance of a group of high-functioning participants with ASD (N=15) and an age- and IQ-matched control group (N=18) on two executive function tests, whilst undergoing functional magnetic resonance imaging (fMRI). Behaviourally, there were no significant differences between the two groups. In a classical test of executive function (random response generation), BOLD signal differed between the groups in the cerebellum but not in the frontal lobes. However, on a new test of executive function (selection between stimulus-oriented and stimulus-independent thought), the ASD group exhibited significantly greater signal-change in medial rostral prefrontal cortex (especially Brodmann Area 10) in the comparison of stimulus-oriented versus stimulus-independent attention. In addition, the new test (but not the classical test) provided evidence for abnormal functional organisation of medial prefrontal cortex in ASD. These results underline the heterogeneity of different tests of executive function, and suggest that executive functioning in ASD is associated with task-specific functional change.

Neural basis of the emotional Stroop interference effect in major depression

BACKGROUND

A mood-congruent sensitivity towards negative stimuli has been associated with development and maintenance of major depressive disorder (MDD). The emotional Stroop task assesses interference effects arising from the conflict of emotional expressions consistent with disorder-specific self-schemata and cognitive colour-naming instructions. Functional neuroimaging studies of the emotional Stroop effect advocate a critical involvement of the anterior cingulate cortex (ACC) during these processes.

METHOD

Subjects were 17 medication-free individuals with unipolar MDD in an acute depressive episode (mean age 39 years), and 17 age-, gender- and IQ-matched healthy volunteers. In an emotional Stroop task, sad and neutral words were presented in various colours, and subjects were required to name the colour of words whilst undergoing functional magnetic resonance imaging (fMRI). Overt verbal responses were acquired with a clustered fMRI acquisition sequence.

RESULTS

Individuals with depression showed greater increases in response time from neutral to sad words relative to controls. fMRI data showed a significant engagement of left rostral ACC (BA 32) and right precuneus during sad words in patients relative to controls. Additionally, rostral ACC activation was positively correlated with latencies of negative words in MDD patients. Healthy controls did not have any regions of increased activation compared to MDD patients.

CONCLUSIONS

These findings provide evidence for a behavioural and neural emotional Stroop effect in MDD and highlight the importance of the ACC during monitoring of conflicting cognitive processes and mood-congruent processing in depression.

Decomposing interference during Stroop performance into different conflict factors: an event-related fMRI study

In the current event-related functional magnetic resonance imaging (fMRI) study, we sought to trace back Stroop-interference to circumscribed properties of task-irrelevant word information - response-incompatibility, semantic incongruency and task-reference - that we conceive as conflict factors. Thereby, we particularly wanted to disentangle intermingled contributions of semantic conflict and response conflict to the overall Stroop-interference effect. To delineate neural substrates of single factors, we referred to the logics of cognitive subtraction and cognitive conjunction. Moreover, in a second step, we conducted correlation analyses to determine the relationship between neural activations and behavioral interference costs (i.e., conflict-related reaction time (RT) slowing) so as to further elucidate the functional role of the respective brain regions in conflict processing. Response-incompatibility was associated with activation in the left premotor cortex which can be interpreted as indicating motor competition or conflict, i.e., the presence of competing response tendencies. Accordingly, this activation was positively correlated with behavioral conflict costs. Semantic incongruency exhibited specific activation in the anterior cingulate cortex (ACC), the bilateral insula, and thalamus as well as in left somatosensory cortex. As supported by the consistent negative correlation with behavioral conflict costs, these activations most probably reflect strengthened control efforts to overcome interference and to ensure adequate task performance. Finally, task-reference elicited activation in the left temporo-polar cortex (TPC) and the right medial superior as well as in left rostroventral prefrontal cortex (rvPFC, sub-threshold activation). As strongly supported by prior studies' findings, this neural activation pattern may underlie residual semantic processing of the task-irrelevant word information.

Processing of inconsistent emotional information: an fMRI study

Previous studies investigating the anterior cingulate cortex (ACC) have relied on a number of tasks which involved cognitive control and attentional demands. In this fMRI study, we tested the model that ACC functions as an attentional network in the processing of language. We employed a paradigm that requires the processing of concurrent linguistic information predicting that the cognitive costs imposed by competing trials would engender the activation of ACC. Subjects were confronted with sentences where the semantic content conflicted with the prosodic intonation (CONF condition) randomly interspaced with sentences which conveyed coherent discourse components (NOCONF condition). We observed the activation of the rostral ACC and the middle frontal gyrus when the NOCONF condition was subtracted from the CONF condition. Our findings provide evidence for the involvement of the rostral ACC in the processing of complex competing linguistic stimuli, supporting theories that claim its relevance as a part of the cortical attentional circuit. The processing of emotional prosody involved a bilateral network encompassing the superior and medial temporal cortices. This evidence confirms previous research investigating the neuronal network that supports the processing of emotional information.

Effects of olfactory stimulation with isovaleric acid on brain activation in informed and naïve conditions: A functional MRI study

OBJECTIVE

To investigate the differences in regions of brain activation in response to olfactory stimulation by functional magnetic resonance imaging in conditions of prior warning of an odor and without.

METHODS

Participants were 17 normal right-handed volunteers; 8 participants received prior warning of the odor (informed condition) and 9 participants were not pre-warned (naïve condition). The odorant used was isovaleric acid.

RESULTS

In the informed condition with prior warning, activation was observed in the putamen extending to the insula, amygdala, and inferior frontal gyrus, and there was instant reification of the odor, while in the naïve condition without prior warning, activation was observed in the anterior cingulate cortex, entorhinal cortex, putamen and inferior frontal gyrus, and recognition of the odor was difficult.

CONCLUSIONS

These results suggest that the condition prior to olfactory stimulation, i.e., with or without prior warning, can affect recognition and regions of brain activation in response to olfactory stimulation using isovaleric acid. Differences in recognition and regions of brain activation between both conditions could be associated with response latencies, or degree of attention, expectation and/or concentration.

Comparison of inhibitory functioning in mild Alzheimer's disease and frontotemporal dementia

Executive dysfunction is frequently reported in Alzheimer's disease (AD) and the frontal variant of frontotemporal dementia (FTD). More specifically, inhibitory dysfunction is observed early in AD and inhibitory deficits are also prominent in patients with FTD. However, few studies have simultaneously explored and compared inhibitory abilities in both degenerative diseases. Consequently, the aim of this study was to compare verbal and motor inhibitory processes in the initial stages of AD and the frontal variant of FTD. Stroop and Go/No-go tasks were administered. The results demonstrate that, on the Go/No-go task, AD and FTD patients do not produce more errors than control subjects. However, both groups are impaired on the Stroop task (mainly with regard to the error score) but do not differ from each other. These results indicate that AD and FTD patients do not present a general impairment of their inhibitory abilities. Moreover, these two kinds of dementia present similar quantitative and qualitative inhibitory impairments on the two tasks, although their patterns of structural and functional cerebral impairments are known to be different. The presence of similar inhibitory deficits despite very different patterns of brain damage is in agreement with the hypothesis that inhibitory dysfunction in the two groups of patients depends on a disconnection process between anterior and posterior cerebral areas, rather than on the presence of focal metabolism decreases in different regions.

Dissociable neural systems resolve conflict from emotional versus nonemotional distracters

The human brain protects the processing of task-relevant stimuli from interference ("conflict") by task-irrelevant stimuli via attentional biasing mechanisms. The lateral prefrontal cortex has been implicated in resolving conflict between competing stimuli by selectively enhancing task-relevant stimulus representations in sensory cortices. Conversely, recent data suggest that conflict from emotional distracters may be resolved by an alternative route, wherein the rostral anterior cingulate cortex inhibits amygdalar responsiveness to task-irrelevant emotional stimuli. Here we tested the proposal of 2 dissociable, distracter-specific conflict resolution mechanisms, by acquiring functional magnetic resonance imaging data during resolution of conflict from either nonemotional or emotional distracters. The results revealed 2 distinct circuits: a lateral prefrontal "cognitive control" system that resolved nonemotional conflict and was associated with enhanced processing of task-relevant stimuli in sensory cortices, and a rostral anterior cingulate "emotional control" system that resolved emotional conflict and was associated with decreased amygdalar responses to emotional distracters. By contrast, activations related to both emotional and nonemotional conflict monitoring were observed in a common region of the dorsal anterior cingulate. These data suggest that the neuroanatomical networks recruited to overcome conflict vary systematically with the nature of the conflict, but that they may share a common conflict-detection mechanism.

Imaging the changing role of feedback during learning in decision-making

Learning from the outcome of decisions can be expected not only to change future decisions, but also our reaction to future outcomes. Using functional magnetic resonance imaging we investigated the neural responses of healthy subjects to feedback about choice outcomes before and after learning a response strategy which led to correct choices only. The task was designed so that losses were unavoidable even when all the choices made were correct. Subjects showed a distinct pattern of learning starting with an initial exploratory phase in which hypotheses about the correct strategy were generated and tested, followed by a phase of rapid strategy acquisition before reaching a final phase of proficiency. Neural activation was more pronounced during feedback processing in the exploratory phase than in the proficiency phase in a distributed network encompassing prefrontal and parietal areas as well as the striatum. These areas are involved in working memory processes, the management of uncertainty and the establishment of stimulus-outcome contingencies. Reduced activation during feedback processing following learning was not only observed within subjects across learning phases, but also between subjects with different learning speeds. Thus, controlled and automatic processing are characterised by differing amounts of activation in identical task-relevant areas. Furthermore, whereas the same brain regions coded for gains and losses, the activation following gains changed to a larger extent with learning than following losses. This suggests that positive prediction errors are more sensitive to increased reward predictability than are negative prediction errors.

Neurocognitive correlates of problem behavior in environmentally at-risk adolescents

OBJECTIVE

This study prospectively examines the correlation between neurocognitive (NC) functioning and problem behavior in early adolescence.

METHODS

As part of a longitudinal study, African American urban youths of lower socioeconomic status, mean age 12.1 years (SD=1.2, n=111), were administered a battery of 16 NC tasks assessing eight NC systems (two tasks per system) including four systems primarily associated with frontal cortex and four primarily associated with nonfrontal cortex. The former systems included (1) executive cognitive functioning (ECF), (2) cognitive control, (3) working memory, and (4) reward processing. The latter systems included (5) receptive language, (6) spatial cognition, (7) visual cognition, and (8) memory. The Teacher's Report Form of the Achenbach System of Empirically Based Assessment was performed approximately at the same age that the NC assessments were performed. Bivariate correlations were calculated between the eight NC system composite scores and the externalizing scores.

RESULTS

Significant negative relationships were found between ECF and receptive language ability and externalizing behavior. Further analyses, using linear regression, showed that receptive language was more predictive of externalizing behavior than ECF.

CONCLUSION

Based on these results we conclude that (1) NC functioning, specifically in ECF and in receptive language systems, was associated with adolescent problem behavior and (2) receptive language was more strongly associated with problem behavior than ECF.

Learning effective brain connectivity with dynamic Bayesian networks

We propose to use dynamic Bayesian networks (DBN) to learn the structure of effective brain connectivity from functional MRI data in an exploratory manner. In our previous work, we used Bayesian networks (BN) to learn the functional structure of the brain (Zheng, X., Rajapakse, J.C., 2006. Learning functional structure from fMR images. NeuroImage 31 (4), 1601-1613). However, BN provides a single snapshot of effective connectivity of the entire experiment and therefore is unable to accurately capture the temporal characteristics of connectivity. Dynamic Bayesian networks (DBN) use a Markov chain to model fMRI time-series and thereby determine temporal relationships of interactions among brain regions. Experiments on synthetic fMRI data demonstrate that the performance of DBN is comparable to Granger causality mapping (GCM) in determining the structure of linearly connected networks. Dynamic Bayesian networks render more accurate and informative brain connectivity than earlier methods as connectivity is described in complete statistical sense and temporal characteristics of time-series are explicitly taken into account. The functional structures inferred on two real fMRI datasets are consistent with the previous literature and more accurate than those discovered by BN. Furthermore, we study the effects of hemodynamic noise, scanner noise, inter-scan interval, and the variability of hemodynamic parameters on the derived connectivity.

Common and Unique Neural Activations in Autobiographical, Episodic, and Semantic Retrieval

This study sought to explore the neural correlates that underlie autobiographical, episodic, and semantic memory. Autobiographical memory was defined as the conscious recollection of personally relevant events, episodic memory as the recall of stimuli presented in the laboratory, and semantic memory as the retrieval of factual information and general knowledge about the world. Our objective was to delineate common neural activations, reflecting a functional overlap, and unique neural activations, reflecting functional dissociation of these memory processes. We conducted an event-related functional magnetic resonance imaging study in which we utilized the same pictorial stimuli but manipulated retrieval demands to extract autobiographical, episodic, or semantic memories. The results show a functional overlap of the three types of memory retrieval in the inferior frontal gyrus, the middle frontal gyrus, the caudate nucleus, the thalamus, and the lingual gyrus. All memory conditions yielded activation of the left medial-temporal lobe; however, we found a functional dissociation within this region. The anterior and superior areas were active in episodic and semantic retrieval, whereas more posterior and inferior areas were active in autobiographical retrieval. Unique activations for each memory type were also delineated, including medial frontal increases for autobiographical, right middle frontal increases for episodic, and right inferior temporal increases for semantic retrieval. These findings suggest a common neural network underlying all declarative memory retrieval, as well as unique neural contributions reflecting the specific properties of retrieved memories.

Common regions of dorsal anterior cingulate and prefrontal-parietal cortices provide attentional control of distracters varying in emotionality and visibility

Top-down attentional control is necessary to ensure successful task performance in the presence of distracters. Lateral prefrontal cortex, parietal cortex and anterior cingulate cortex have been previously implicated in top-down attentional control. However, it is unclear whether these regions are engaged independent of distracter type or whether, as has been suggested for anterior cingulate cortex, different regions provide attentional control over emotional versus other forms of salient distracter. In the current task, subjects viewed targets that were preceded by distracters that varied in both emotionality and visibility. We found that behaviorally, the presence of preceding distracters significantly interfered with target judgment. At the neural level, increases in the emotional and visual saliency of distracters were both associated with increased activity in proximal regions of prefrontal, parietal and cingulate cortex. Moreover, a conjunction analysis indicated considerable overlap in the regions of prefrontal, parietal cortex and anterior cingulate cortex responding to distracters of increased emotionality and visibility.

Reduced microstructural integrity of the white matter underlying anterior cingulate cortex is associated with increased saccadic latency in schizophrenia

The anterior cingulate cortex (ACC) is a key component of a network that directs both spatial attention and saccadic eye movements, which are tightly linked. Diffusion tensor imaging (DTI) has demonstrated reduced microstructural integrity of the anterior cingulum bundle as indexed by fractional anisotropy (FA) in schizophrenia, but the functional significance of these abnormalities is unclear. Using DTI, we examined the white matter underlying anterior cingulate cortex in schizophrenia to determine whether reduced FA is associated with prolonged latencies of volitional saccades. Seventeen chronic, medicated schizophrenia outpatients and nineteen healthy controls had high-resolution DTI scans. FA maps were registered to structural scans and mapped across participants using a surface-based coordinate system. Cingulate white matter was divided into rostral and dorsal anterior regions and a posterior region. Patients showed reduced FA in cingulate white matter of the right hemisphere. Reduced FA in the white matter underlying anterior cingulate cortex, frontal eye field, and posterior parietal cortex of the right hemisphere was associated with longer saccadic latencies in schizophrenia, though given the relatively small sample size, these relations warrant replication. These findings demonstrate that in schizophrenia, increased latency of volitional saccades is associated with reduced microstructural integrity of the white matter underlying key cortical components of a right-hemisphere dominant network for visuospatial attention and ocular motor control. Moreover, they suggest that anterior cingulate white matter abnormalities contribute to slower performance of volitional saccades and to inter-individual variability of saccadic latency in chronic, medicated schizophrenia.

Heritability of anterior cingulate response to conflict: an fMRI study in female twins

Interference processing requires increased focus on relevant dimensions of environmental stimuli and selective allocation of attentional resources, in order to filter extraneous information and inhibit non-adaptive responses. This process is important in everyday life and is necessary for responding to novel and challenging situations. Dorsal anterior cingulate cortex (dACC) is involved in this process, and behavioral twin studies indicate that performance on interference processing tasks is highly heritable. However, the extent to which dACC activation related to such tasks is influenced by genetic factors has not been reported. In the current study, 10 pairs of monozygotic and 10 pairs of dizygotic female twins performed a validated interference processing task during fMRI. There were three main results: (1) increased dACC activation for incongruent (INC) minus congruent (CON) trials was observed; (2) dACC activation for INC minus CON trials was both moderately heritable and significantly correlated with the difference in reaction time (RT) between INC and CON trials; (3) RT for INC trials was moderately heritable. RT for CON trials and the latency difference between INC and CON trials were not influenced significantly by genetic factors. The current study provides the first functional imaging evidence that dACC activation during interference processing is significantly influenced by genes. These results suggest an endophenotype that may be applied to various psychiatric disorders that are both highly heritable and associated with altered dACC function.

Neurocognitive functioning in AD/HD, predominantly inattentive and combined subtypes

The Predominantly Inattentive (PI) and Combined (CB) subtypes of AD/HD differ in cognitive tempo, age of onset, gender ratio, and comorbidity, yet a differentiating endophenotype has not been identified. The aim of this study was to test rigorously diagnosed PI, CB, and typical children on measures selected for their potential to reveal hypothesized differences between the subtypes in specific neurocognitive systems (anterior vs. posterior attentional systems) and processes (arousal vs. activation). Thirty-four CB and 26 PI children meeting full DSM-IV criteria for subtype both in school and at home, without confounding reading disability or emotional disorder, were enrolled along with 20 typically developing children. Neurocognitive functions measured included attention, inhibitory control, working memory, learning, and executive functions. Tasks included the Stroop, Wisconsin Card Sorting Test, Continuous Performance Test (CPT). Buschke Selective Reminding Test, ad the Tower of London (TOL), as well as instruments developed by Posner and Sternberg, and tasks assessing the impact on reaction time of [corrected] varying preparatory intervals and stimulus/response complexity. After co-varying for IQ, subtypes differed primarily on measures of impulsivity during tests of vigilance (CPT) and executive function (TOL), with the CB group showing greater impulsivity than both other groups. In addition, the PI group showed worse performance than CB and control groups on the WISC-III Processing Speed Index. Whether analyzed with or without an IQ co-variate, there was no support in the data for hypothesized differences between subtypes in functioning of the anterior vs. posterior attentional systems, nor in involvement of arousal vs. activation processes. The results indicate that the PI and CB subtypes are best differentiated by ratings, observations and tests of cognitive tempo and behavioral impulsivity. Neuropsychological methods have yet to identify critical neuropsychological [corrected] substrates of these differences.

The Multi-Source Interference Task: an fMRI task that reliably activates the cingulo-frontal-parietal cognitive/attention network

In this protocol we describe how to perform the Multi-Source Interference Task (MSIT), a validated functional magnetic resonance imaging (fMRI) task that reliably and robustly activates the cingulo-frontal-parietal cognitive/attention network (CFP network) within individual subjects. The MSIT can be used to (i) identify the cognitive/attention network in normal volunteers and (ii) test its integrity in people with neuropsychiatric disorders. It is simple to perform, can be completed in less than 15 min and is not language specific, making it appropriate for children, adults and the elderly. Since its validation, over 100 adults have performed the task. The MSIT produces a robust and temporally stable reaction time interference effect (range 200-350 ms), and single runs of the MSIT have produced CFP network activation in approximately 95% of tested subjects. The robust, reliable and temporally stable neuroimaging and performance data make the MSIT a useful task with which to study normal human cognition and psychiatric pathophysiology.

Exploring the physiological effects of double-cone coil TMS over the medial frontal cortex on the anterior cingulate cortex: an H2(15)O PET study

Transcranial magnetic stimulation (TMS) using a double-cone coil over the medial frontal cortex has the potential to clarify the function of the anterior cingulate cortex (ACC) in cognition, emotion and mood disorders. Following demonstration of disruption of performance on psychological tasks closely linked to cingulate function using this TMS technique, the current study aimed to directly measure the regional distribution of physiological effects of stimulation in the brain with H2(15)O PET. Experiment 1 assessed the effect of increasing numbers of pulse trains of TMS on regional cerebral blood flow (rCBF). Experiment 2 assessed the capacity of medial frontal TMS to modulate brain activity associated with the Stroop task using medial parietal TMS as a control site of stimulation. SPM99 analyses, using the ACC as a region of interest, revealed clusters of increased rCBF during medial frontal TMS in Brodmann area 24 and reduced rCBF in more ventral ACC, the latter occurring in both experiments. In a whole-brain analysis, striking changes in rCBF were observed distal to the ACC following medial frontal TMS. Although TMS reliably affected Stroop task performance in early trials, there was no interaction between TMS and Stroop condition in rCBF. Our results suggest that medial frontal TMS using the double-cone coil can affect ACC activity. However, a number of more distal cortical areas were also affected in these experiments. These additional changes may reflect either 'downstream' effects of altered cingulate cortex activity or direct effects of the coil.

The role of the basal ganglia in bimanual coordination

The functional anatomical role of the basal ganglia in bimanual coordination is unknown. Utilizing functional MRI (fMRI) at 3 T, we analyzed brain activity during three different typing tasks. The first task consisted of typing with parallel finger movements (moving left to right with four fingers on both hands). The second task was mirror movements (moving little finger to index finger on both hands), and the third task compared a resting condition with right-handed unimanual typing (moving little finger to index finger). Task dependent BOLD activity in the supplementary motor area (SMA) and dorsolateral premotor areas was observed. In addition, activation patterns were present in the cerebellar vermis during bimanual coordination tasks, with greater activation in the parallel than in the mirror condition. Finally, we also identified activity in the putamen during the tasks described above. Interestingly, putaminal activity was greatest during the period of motor task initiation, and activity during this period was greatest in the parallel condition. Our results suggest a critical role of the basal ganglia in the neural control of bimanual coordination.

Controlling emotional expression: behavioral and neural correlates of nonimitative emotional responses

Emotional facial expressions can engender similar expressions in others. However, adaptive social and motivational behavior can require individuals to suppress, conceal, or override prepotent imitative responses. We predicted, in line with a theory of "emotion contagion," that when viewing a facial expression, expressing a different emotion would manifest as behavioral conflict and interference. We employed facial electromyography (EMG) and functional magnetic resonance imaging (fMRI) to investigate brain activity related to this emotion expression interference (EEI) effect, where the expressed response was either concordant or discordant with the observed emotion. The Simon task was included as a nonemotional comparison for the fMRI study. Facilitation and interference effects were observed in the latency of facial EMG responses. Neuroimaging revealed activation of distributed brain regions including anterior right inferior frontal gyrus (brain area [BA] 47), supplementary motor area (facial area), posterior superior temporal sulcus (STS), and right anterior insula during emotion expression-associated interference. In contrast, nonemotional response conflict (Simon task) engaged a distinct frontostriatal network. Individual differences in empathy and emotion regulatory tendency predicted the magnitude of EEI-evoked regional activity with BA 47 and STS. Our findings point to these regions as providing a putative neural substrate underpinning a crucial adaptive aspect of social/emotional behavior.