Interference and facilitation effects during selective attention: an H215O PET study of Stroop task performance

Specific metabolites in the medial prefrontal cortex are associated with the neurocognitive deficits in schizophrenia: a preliminary study

We measured brain metabolites in the medial prefrontal cortex of 19 schizophrenic patients and 18 healthy controls by 3 T proton magnetic resonance spectroscopy ((1)H MRS), and examined the relationship between prefrontal cortex-related neurocognitive functions and brain metabolites in the medial prefrontal cortex. The patients with schizophrenia exhibited deficits on the verbal fluency, Wisconsin card sorting test (WCST), trail making test, Stroop test and digit span distraction test (DSDT), but not on the Iowa gambling test. The patients showed statistical significant changes in the ratio of glutamine/glutamate, the ratio of N-acetyl-l-aspartate (NAA)/glycerophosphorylcholine plus phosphorylcholine (GPC+PC) and the levels of taurine in the medial prefrontal cortex compared with normal controls. Furthermore, we found significant correlations of the ratio of glutamine/glutamate with WCST and DSDT scores, the ratio of NAA/(GPC+PC) with verbal fluency and WCST scores, and the levels of taurine with scores on the Stroop test and Trail making test A among the participants. The ratios of NAA/(GPC+PC) and (GPC+PC)/(Cr+PCr) had significant relationships with the duration of untreated psychosis of the schizophrenic patients. The glutamine/glutamate ratio and levels of taurine were significantly related to the duration of illness of the patients. These data suggest that specific metabolites of the medial prefrontal cortex are associated with the neurocognitive deficits in schizophrenia.

Structural disruption of the dorsal cingulum bundle is associated with impaired Stroop performance in patients with schizophrenia

Previous diffusion tensor imaging (DTI) studies have shown structural abnormalities of the cingulum bundle (CB) in patients with schizophrenia. However, regional specificity and functional relevance of the pregenual and dorsal CB subdivisions has not been fully studied. In the current study, 31 patients with schizophrenia and 65 age- and gender-matched healthy subjects underwent DTI to measure fractional anisotropy (FA) and mean diffusivity (MD) in cross sections of dorsal and pregenual CB tractography. To test the hypothesis of region-specific association with neurocognition, all of the patients and 31 controls performed the Stroop task, which is assumed to mainly involve dorsal cingulate function. The verbal memory subscale of Wechsler Memory Scale-Revised and premorbid IQs estimated from the Japanese version of the National Adult Reading Test, which were non-specific to dorsal cingulate function, were also employed as control neurocognitive indices. Significant bilateral FA reductions in the pregenual and dorsal CB, and bilateral MD increases in the dorsal CB were observed in the patients compared with the controls. As predicted, significant associations between DTI measures and neurocognition were found in the schizophrenia group only: double-dissociable correlation between higher MD in the dorsal, not in the pregenual CB, and a longer reaction time in the Stroop task, not verbal memory or premorbid IQs. The current DTI study suggests that structural disruption of the dorsal CB has region-specific functional relevance to selective attention deficits, although structural disruption also exists in the pregenual CB in patients with schizophrenia.

Menstrual cycle phase effects on memory and Stroop task performance

The present study examined differences in Stroop and memory task performances modulated by gonadal steroid hormones during the menstrual cycle in women. Thirty women with regular menstrual cycles performed a logical memory task (Wechsler Memory Scale) and the Stroop task. The results showed a significant difference in Stroop task performance between low and high levels of estradiol and progesterone during the menstrual cycle, but there was no significant difference in memory performance between the two phases, nor was there any significant mood change that might have influenced cognitive performance. These findings suggest that sex-related hormone modulation selectively affects cognitive functions depending on the type of task and low level secretion of estradiol appears to contribute to reducing the level of attention that relates to the prefrontal cortex.

Effect of handedness on the Stroop Colour Word Task

Handedness is associated with cerebral organisation, but its relationship with cognition remains unclear. Since the Stroop task is believed to measure aspects of executive control, this study aims to investigate the effect of handedness on Stroop interference. We used the Stroop task with 90 young adults with university education, of whom 47 (23 males) were right-handed and 43 (21 males) were left-handed. Main dependent variables were Stroop baseline (SB), Stroop incongruent (SI), and the proportional derivative Stroop reduction (SR) [SR=(SB - SI)/SB×100%] (Bugg, Delosh, Davalos, & Davis, 2007; Graf, Uttl, &Tuokko, 1995) scores. The analysis revealed that SI is significantly affected by both handedness and the interaction of sex×handedness, whereas SR is only affected by handedness. After controlling for the effect of SB on SI, only the effect of handedness remained statistically significant [F(1, 83) = 6.44, p=.013]. Post-hoc comparisons showed that left-handed females performed significantly better than right-handed females on both SI (p=.003) and SR (p=.007). The data suggest that handedness is associated with cognitive function alterations, which lead to a smaller Stroop interference of left-handers irrespectively of sex, an effect that is more pronounced in the female subpopulation.

P300 AND RESPONSE TIME FROM THE COLORED KANJI STROOP TASK

The P300 component of the event-related brain potential during the colored Kanji Stroop task was used in conjunction with response time to identify the locus of interference. Participants were instructed to respond to the colored Kanji characters as quickly as possible in the respective stimulus conditions. Response time varied with the congruence and incongruence stimulus conditions. However, the P300 latency remained stable during the stimulus-related processes. P300 amplitude decreased from the parietal, central to the frontal electrode sites in order in each stimulus condition. The findings provide further evidence that response-related processes are the primary source of Stroop interference.

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.

The effect of acute treadmill walking on cognitive control and academic achievement in preadolescent children

The effect of an acute bout of moderate treadmill walking on behavioral and neuroelectric indexes of the cognitive control of attention and applied aspects of cognition involved in school-based academic performance were assessed. A within-subjects design included 20 preadolescent participants (age=9.5+/-0.5 years; eight female) to assess exercise-induced changes in performance during a modified flanker task and the Wide Range Achievement Test 3. The resting session consisted of cognitive testing followed by a cardiorespiratory fitness assessment to determine aerobic fitness. The exercise session consisted of 20 min of walking on a motor-driven treadmill at 60% of estimated maximum heart rate followed by cognitive testing once heart rate returned to within 10% of pre-exercise levels. Results indicated an improvement in response accuracy, larger P3 amplitude, and better performance on the academic achievement test following aerobic exercise relative to the resting session. Collectively, these findings indicate that single, acute bouts of moderately-intense aerobic exercise (i.e. walking) may improve the cognitive control of attention in preadolescent children, and further support the use of moderate acute exercise as a contributing factor for increasing attention and academic performance. These data suggest that single bouts of exercise affect specific underlying processes that support cognitive health and may be necessary for effective functioning across the lifespan.

Relationship Between White Matter Integrity, Attention, and Memory in Schizophrenia: A Diffusion Tensor Imaging Study

Attention and memory deficits are among the most prominent cognitive disturbances observed in schizophrenia. It has been suggested that a disruption in anatomical connectivity between areas involved in attentional control might be responsible for these abnormalities. We used Diffusion Tensor Tractography and Color Stroop/Negative Priming(NP) paradigm to investigate integrity of Cingulum Bundle(CB), the main white matter tract interconnecting these regions, and its relationship with executive functions in patients with schizophrenia and matched controls. The Fractional Anisotropy(FA), was calculated along the CB pathways, and correlated with reaction times for each Stroop item, and both Stroop, and NP effects. Patients with schizophrenia demonstrated decreased CB integrity and diminished NP effect, compared with controls, but both groups showed Stroop effect. For patients only, reaction times for every item, as well as for Stroop effect, correlated with left CB FA. These findings suggest that CB integrity disruptions might compromise the executive processes in schizophrenia.

Structural and functional MRI correlates of Stroop control in benign MS

The objective of this study was to assess the functional and structural substrates of cognitive network changes in patients with benign multiple sclerosis (BMS), using an analysis of effective connectivity and MR tractography. Using a 3-Tesla scanner, we acquired dual-echo, diffusion tensor (DT) and functional MRI during the performance of the Stroop task from 15 BMS patients and 19 healthy controls. DT MRI tractography was used to calculate DT derived metrics from several white matter (WM) fiber bundles, thought to be involved in cognitive performance. DT MRI metrics from WM fiber bundles not directly related with cognitive performance were also derived. Effective connectivity analysis was performed using statistical parametric mapping. MS patients had significantly abnormal DT MRI metrics in all the structures analyzed. Compared with controls, MS patients had more significant activations of several areas of the cognitive network involved in Stroop performance, bilaterally. Compared with controls, BMS patients also had increased connectivity strengths between several cortical areas of the sensorimotor network and the right (R) inferior frontal gyrus and the R cerebellum, as well as decreased connectivity strengths with the anterior cingulate cortex. Coefficients of altered connectivity were moderately correlated with structural MRI metrics of tissue damage within intra- and inter-hemispheric cognitive-related WM fiber bundles, while no correlations were found with the remaining fiber bundles studied, suggesting that functional cortical changes in patients with BMS might represent an adaptive response driven by damage of specific WM structures.

Attention enhances the neural processing of relevant features and suppresses the processing of irrelevant features in humans: a functional magnetic resonance imaging study of the Stroop task

We present a functional MRI experiment investigating the neural basis of feature-based attention in humans using the Stroop task. Cortical areas specifically involved in color processing and word reading were first identified in individual participants using independent tests. These areas were then probed during the Stroop task (in which participants must selectively attend to the font color of a word while ignoring the word itself). We found that activation in functionally defined color areas increased during the task relative to a neutral color-naming task while activation in functionally defined word areas decreased. These results are consistent with a biased competition model of feature-based attention in which the processing of attended features is enhanced and the processing of ignored features is suppressed.

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.

Functional MRI study of brain activation alterations in patients with obsessive-compulsive disorder after symptom improvement

Dysfunction of the frontal-subcortical circuits has been the most common finding in the pathophysiology of obsessive-compulsive disorder (OCD), and recent neuropsychological studies have shown cognitive impairments in OCD. To clarify the pathophysiology of OCD without the confounding effects of medication, we investigated the alterations of brain function in OCD patients and changes after clinical improvement due solely to behavior therapy. The participants were 11 outpatients with OCD and 19 normal controls. The patients received 12 weeks of behavior therapy. We investigated the differences in the behavioral performance and functional magnetic resonance imaging results during the Stroop test in the patients and normal controls, and their changes after treatment in the patients. The patients showed less activation in the anterior cingulate gyrus and cerebellum than control subjects. Following significant improvement in OC symptoms, the cerebellum and parietal lobe showed increased activation, and the orbitofrontal cortex, middle frontal gyrus, and temporal regions showed decreased activation during the Stroop task, and performance of the task itself improved. Our findings suggest that dysfunction of the posterior brain regions, especially the cerebellum, is involved in the pathogenesis of OCD, and that normalization in function can occur with improvement of OC symptoms.

Processing conflicting information: facilitation, interference, and functional connectivity

When a conflict task involves congruent, neutral, and incongruent conditions, it is possible to examine facilitation (neutral vs. congruent) and interference (incongruent vs. neutral) components. Very few studies investigated the brain areas that are specifically involved in facilitation or interference. We used functional magnetic resonance imaging while participants performed a magnitude conflict task (the size congruity paradigm). We observed four findings: (1) while most of the brain areas that were activated by conflict tasks showed interference effects, the intraparietal sulcus was the only region activated for both interference and facilitation components. (2) Two groups of participants could be distinguished based on the pattern of anterior cingulate cortex (ACC) activity, one with classical facilitation (congruent<neutral), one with reverse facilitation. (3) Functional connectivity analysis of the areas that were modulated by the conflict task revealed an anterior cingulate - lateral prefrontal cortex network and a dorsal parietal - premotor cortex network. We suggest that the former plays a role in cognitive control and conflict detection, whereas the latter participates in top-down selection of task-relevant stimuli and response mapping. (4) These networks were modulated by the two groups that we distinguished based on the ACC activation.

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.

Negative correlation between brain glutathione level and negative symptoms in schizophrenia: a 3T 1H-MRS study

Background

Glutathione (GSH), a major intracellular antioxidant, plays a role in NMDA receptor-mediated neurotransmission, which is involved in the pathophysiology of schizophrenia. In the present study, we aimed to investigate whether GSH levels are altered in the posterior medial frontal cortex of schizophrenic patients. Furthermore, we examined correlations between GSH levels and clinical variables in patients.

Methods and Findings

Twenty schizophrenia patients and 16 age- and gender-matched normal controls were enrolled to examine the levels of GSH in the posterior medial frontal cortex by using 3T SIGNA EXCITE ¹H-MRS with the spectral editing technique, MEGA-PRESS. Clinical variables of patients were assessed by the Global Assessment of Functioning (GAF), Scale for the Assessment of Negative Symptoms (SANS), Brief Psychiatric Rating Scale (BPRS), Drug-Induced Extra-Pyramidal Symptoms Scale (DIEPSS), and five cognitive performance tests (Word Fluency Test, Stroop Test, Trail Making Test, Wisconsin Card Sorting Test and Digit Span Distractibility Test). Levels of GSH in the posterior medial frontal cortex of schizophrenic patients were not different from those of normal controls. However, we found a significant negative correlation between GSH levels and the severity of negative symptoms (SANS total score and negative symptom subscore on BPRS) in patients. There were no correlations between brain GSH levels and scores on any cognitive performance test except Trail Making Test part A.

Conclusion

These results suggest that GSH levels in the posterior medial frontal cortex may be related to negative symptoms in schizophrenic patients. Therefore, agents that increase GSH levels in the brain could be potential therapeutic drugs for negative symptoms in schizophrenia.

Performance on the Stroop predicts treatment compliance in cocaine-dependent individuals

Treatment dropout is a problem of great prevalence and stands as an obstacle to recovery in cocaine-dependent (CD) individuals. Treatment attrition in CD individuals may result from impairments in cognitive control, which can be reliably measured by the Stroop color-word interference task. The present analyses contrasted baseline performance on the color-naming, word-reading, and interference subtests of the Stroop task in CD subjects who completed a cocaine treatment trial (completers: N=50) and those who dropped out of the trial before completion (non-completers: N=24). A logistic regression analysis was used to predict trial completion using three models with the following variables: the Stroop task subscale scores (Stroop model); the Hamilton depression rating scale (HDRS) scores (HDRS model); and both the Stroop task subscale scores and HDRS scores (Stroop and HDRS model). Each model was able to significantly predict group membership (completers vs non-completers) better than a model based on a simple constant (HDRS model p=0.02, Stroop model p=0.006, and Stroop and HDRS model p=0.003). Models using the Stroop preformed better than the HDRS model. These findings suggest that the Stroop task can be used to identify cocaine-dependent subjects at risk for treatment dropout. The Stroop task is a widely available, reliable, and valid instrument that can be easily employed to identify and tailor interventions of at risk individuals in the hope of improving treatment compliance.

Structural brain correlates of response inhibition in Bipolar Disorder I

Deficits in response inhibition are a prominent feature of Bipolar Disorder, type I (BDI). The purpose of this study was to examine the relationship between inhibitory control and cerebral structure as it may inform our understanding of the pathophysiology of BDI. Inhibitory control was measured in remitted patients with BDI (n = 44) and healthy controls (n = 44), using the interference score from the Stroop Colour Word Task and the scaled total error score from the Hayling Sentence Completion Test. Structural magnetic resonance imaging brain scans were also obtained for all participants. For both measures, better performance in controls correlated positively with gray matter volume in the dorsal and ventral prefrontal cortical (PFC) regions with parietal involvement additionally seen for the interference score. In contrast, better inhibitory control in BDI patients correlated positively with gray matter volume in the right parietal cortical regions, namely the cuneus for the scaled total error score and the inferior parietal lobule for the interference score. The observed lack of correlation between PFC grey matter and measures of inhibitory control in BDI patients is suggestive of PFC dysfunction; the correlation between response inhibition and parietal grey matter volume may be indicative of a compensatory involvement of the parietal cortices in BDI.

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.

Neuropsychological performance predicts clinical recovery in bipolar patients

BACKGROUND

Although a number of investigations have reported cognitive deficits in patients with bipolar disorder, relatively few have focused on the relationship between these impairments and clinical outcome.

METHODS

In order to help clarify the pattern of and extent to which cognitive deficits are present at the onset of illness and their relationship to outcome, we examined 26 bipolar patients during their first hospitalization and 20 psychiatrically healthy control subjects. All subjects completed tests of frontal/executive control, psychomotor speed and memory function at baseline and self-reports of clinical recovery (time to recover in days) at 12 months post study enrollment.

RESULTS

At baseline, first episode bipolar patients demonstrated greater deficits relative to control subjects on neurocognitive measures, and a significant association was detected between time to recover and performance on a measure of frontal/executive function (interference condition of the Stroop; p=.05; derived interference: p=.04). A trend towards significance was also demonstrated between time to clinical recovery and verbal fluency (p=.06).

CONCLUSIONS

These findings indicate that neuropsychological deficits are seen early in the course of bipolar disorder, prior to the effects of multiple or prolonged episodes, and may be associated with clinical outcome. Future studies are needed to determine whether changes in inhibitory processing or other cognitive function predict clinical outcome or are associated with treatment response.

Age-related changes in cognitive conflict processing: An event-related potential study

Cognitive tasks involving conflicting stimuli and responses are associated with an early age-related decline in performance. Conflict and conflict-induced interference can be stimulus- or response-related. In classical stimulus-response compatibility tasks, such as the Stroop task, the event-related potential (ERP) usually reveals a greater negativity on incongruent versus congruent trials which has often been linked with conflict processing. However, it is unclear whether this negativity is related to stimulus- or response-related conflict, thus rendering the meaning of age-related changes inconclusive. In the present study, a modified Stroop task was used to focus on stimulus-related interference processes while excluding response-related interference. Since we intended to study work-relevant effects ERPs and performance were determined in young (about 30 years old) and middle-aged (about 50 years old) healthy subjects (total n=80). In the ERP, a broad negativity developed after incongruent versus congruent stimuli between 350 and 650 ms. An age-related increase of the latency and amplitude of this negativity was observed. These results indicate age-related alterations in the processing of conflicting stimuli already in middle age.

Effects of cigarette smoking and abstinence on Stroop task performance

RATIONALE

Smokers report enhanced concentration after cigarette smoking and difficulty concentrating when abstinent from smoking. These perceived effects may contribute to smoking cessation failures, and if so, clarification of their cognitive bases could inform treatment strategies. Selective attention may be important in this regard, but earlier literature presents inconsistent findings on how smoking abstinence and resumption of smoking influence this cognitive function.

OBJECTIVES

We aimed to compare smokers and nonsmokers on selective attention, and in smokers, to test the effects of overnight abstinence from smoking and of acute smoking on selective attention.

MATERIALS AND METHODS

Smokers and nonsmokers (n = 43) performed a Stroop test (two test days, two test blocks per day). Smokers participated after overnight abstinence and also within 1-h of ad libitum smoking. Smokers each smoked a cigarette between test blocks on each day; nonsmokers did not.

RESULTS

Smokers demonstrated longer response latencies for both congruent and incongruent stimuli after overnight than brief abstinence, but no deficit specifically related to selective attention. Whereas nonsmokers showed no changes in performance in the second test block, smoking between blocks reduced the Stroop effect when smokers were abstinent overnight.

CONCLUSIONS

These data are consistent with the hypothesis that abstinence from smoking among nicotine-dependent individuals has deleterious effects on cognitive performance, but do not indicate that selective attention is adversely effected. Improvement in selective attention after terminating abstinence with one cigarette may also contribute to smokers' perceived enhanced ability to concentrate after smoking.

Imaging functional brain connectivity patterns from high-resolution EEG and fMRI via graph theory

We describe a set of computational tools able to estimate cortical activity and connectivity from high-resolution EEG and fMRI recordings in humans. These methods comprise the estimation of cortical activity using realistic geometry head volume conductor models and distributed cortical source models, followed by the evaluation of cortical connectivity between regions of interest coincident with the Brodmann areas via the use of Partial Directed Coherence. Connectivity patterns estimated on the cortical surface in different frequency bands are then imaged and interpreted with measures based on graph theory. These computational tools were applied on a set of EEG and fMRI data from a Stroop task to demonstrate the potential of the proposed approach. The present findings suggest that the methodology is able to identify differences in functional connectivity patterns elicited by different experimental tasks or conditions.

Dexamphetamine normalises electrophysiological activity in attention deficit-hyperactivity disorder during the Stroop task

A case study was conducted to investigate whether dexamphetamine enhances interference control in an adult with attention deficit/hyperactivity disorder. Continuous electroencephalography was recorded both on and off dexamphetamine during performance on a Stroop task. An age-, gender- and IQ-matched control also completed the same task. Event related potentials for the control participant revealed a positive potential to incongruent stimuli between 270 and 440 ms, whereas for the participant with attention deficit/hyperactivity disorder off medication, the reverse polarity was observed in a later time window. Following administration of dexamphetamine, however, the event-related potentials for the incongruent condition closely resembled those in the control, suggesting that dexamphetamine successfully normalises electroencephalographic activity.

Neural correlates of automatic beliefs about gender and race

Functional MRI was used to identify the brain areas underlying automatic beliefs about gender and race, and suppression of those attitudes. Participants (n = 20; 7 females) were scanned at 3 tesla while performing the Implicit Association Test (IAT), an indirect measure of race and gender bias. We hypothesized that ventromedial prefrontal cortex areas (PFC) would mediate gender and racial stereotypic attitudes, and suppression of these beliefs would recruit dorsolateral prefrontal cortex (DLPFC) and the anterior cingulate cortex (ACC). Performance data on the IAT revealed gender and racial biases. Racial bias was correlated with an explicit measure of racism. Results showed activation of anteromedial PFC and rostral ACC while participants implicitly made associations consistent with gender and racial biases. In contrast, associations incongruent with stereotypes recruited DLPFC. Implicit gender bias was correlated with amygdala activation during stereotypic conditions. Results suggest there are dissociable roles for anteromedial and dorsolateral PFC circuits in the activation and inhibition of stereotypic attitudes.

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.

Preparatory neural activity predicts performance on a conflict task

Advance preparation has been shown to improve the efficiency of conflict resolution. Yet, with little empirical work directly linking preparatory neural activity to the performance benefits of advance cueing, it is not clear whether this relationship results from preparatory activation of task-specific networks, or from activity associated with general alerting processes. Here, fMRI data were acquired during a spatial Stroop task in which advance cues either informed subjects of the upcoming relevant feature of conflict stimuli (spatial or semantic) or were neutral. Informative cues decreased reaction time (RT) relative to neutral cues, and cues indicating that spatial information would be task-relevant elicited greater activity than neutral cues in multiple areas, including right anterior prefrontal and bilateral parietal cortex. Additionally, preparatory activation in bilateral parietal cortex and right dorsolateral prefrontal cortex predicted faster RT when subjects responded to spatial location. No regions were found to be specific to semantic cues at conventional thresholds, and lowering the threshold further revealed little overlap between activity associated with spatial and semantic cueing effects, thereby demonstrating a single dissociation between activations related to preparing a spatial versus semantic task-set. This relationship between preparatory activation of spatial processing networks and efficient conflict resolution suggests that advance information can benefit performance by leading to domain-specific biasing of task-relevant information.

Attention and executive functions profile in drug naive ADHD subtypes

Attention deficit hyperactivity disorder (ADHD) has been associated with executive functioning and sustained and divided attention deficits. In order to clarify the questions on neurocognitive impairment in ADHD, we investigated the presence of specific executive functions (EFs) and attention deficit patterns in ADHD clinical subtypes. 50 patients with ADHD and 44 controls were evaluated. All subjects were boys and performed a clinical-psychopathological and neuropsychological battery. Five main domains of EFs and attention were studied. Executive functions-related neurocognitive abilities were used as control tasks. ADHD patients, inattentive and combined subtypes differ from controls on response inhibition, divided attention, phonological, and visual object working memory and on variability of reaction times measured with CPT. Comparison of ADHD subtypes, in five main domains of EFs, did not show evidence of different executive functioning profiles. Response inhibition can predict performance on working memory tests but it cannot predict performance on divided attention/set shifting and on sustained attention. ADHD boys exhibit a selective impairment on executive functions and attention tasks. These data suggest the involvement of partially independent neural circuits which control inhibition and divided attention in ADHD. Since right prefrontal cortex seems to be crucial in controlling response inhibition, while left dorsolateral prefrontal cortex seems important in modulating divided attention, these areas are deputated to be involved in the pathogenesis of neuropsychological deficits in ADHD subtypes. In addition, this study candidates the impairment in phonological and visual-object working memory as a possible neuropsychological trait in ADHD males with inattentive or combined subtypes.

Interference resolution: insights from a meta-analysis of neuroimaging tasks

A quantitative meta-analysis was performed on 47 neuroimaging studies involving tasks purported to require the resolution of interference. The tasks included the Stroop, flanker, go/no-go, stimulus-response compatibility, Simon, and stop signal tasks. Peak density-based analyses of these combined tasks reveal that the anterior cingulate cortex, dorsolateral prefrontal cortex, inferior frontal gyrus, posterior parietal cortex, and anterior insula may be important sites for the detection and/or resolution of interference. Individual task analyses reveal differential patterns of activation among the tasks. We propose that the drawing of distinctions among the processing stages at which interference may be resolved may explain regional activation differences. Our analyses suggest that resolution processes acting upon stimulus encoding, response selection, and response execution may recruit different neural regions.

Neural correlates of primary and reflective consciousness of spatial orienting

Using functional magnetic resonance imaging, we asked participants to perform a visual target detection task with peripheral cues. In the first part of the experiment, cues were not predictive of the side of occurrence of the incoming target. In the second part of the experiment, unbeknownst to the participants, cues became 80% predictive, thus inducing an endogenous orienting of spatial attention. Confirming previous results, in the second part response times (RTs) decreased for validly cued trials and increased for invalid trials. Half of the participants were subsequently able to correctly describe the cue-target relationships ('verbalizers'), thus demonstrating reflective consciousness of endogenous orienting. Also non-verbalizer participants showed a similar RT pattern, indicating the occurrence of endogenous orienting without reflective consciousness. Both groups of participants showed fronto-parietal activity typically observed in spatial attention tasks. Verbalizers, in addition, demonstrated stronger activity in the anterior cingulate cortex (ACC), consistent with the proposed role of this structure in purposeful behaviour and in the monitoring of its consequences. The extensive pattern of connectivity of the ACC is ideally suited to integrate the activity of the large neural assemblies necessary for reflective consciousness to emerge.

Left ventrolateral prefrontal cortex and the cognitive control of memory

Cognitive control mechanisms permit memory to be accessed strategically, and so aid in bringing knowledge to mind that is relevant to current goals and actions. In this review, we consider the contribution of left ventrolateral prefrontal cortex (VLPFC) to the cognitive control of memory. Reviewed evidence supports a two-process model of mnemonic control, supported by a double dissociation among rostral regions of left VLPFC. Specifically, anterior VLPFC (approximately BA 47; inferior frontal gyrus pars orbitalis) supports controlled access to stored conceptual representations, whereas mid-VLPFC (approximately BA 45; inferior frontal gyrus pars triangularis) supports a domain-general selection process that operates post-retrieval to resolve competition among active representations. We discuss the contribution of these control mechanisms across a range of mnemonic domains, including semantic retrieval, recollection of contextual details about past events, resolution of proactive interference in working memory, and task switching. Finally, we consider open directions for future research into left VLPFC function and the cognitive control of memory.

Event-related potentials dissociate facilitation and interference effects in the numerical Stroop paradigm

In the numerical Stroop paradigm (NSP) participants compare simultaneously presented Arabic digits based on either their numerical or on their physical size dimension. Responses are faster when the numerical and size dimensions are congruent with each other (facilitation), and responses are slower when the numerical and size dimensions are incongruent with each other (interference). We aimed to find out whether facilitation and interference appears during the course of perceptual or response processing. To this end, facilitation and interference effects in the amplitude of event-related brain potentials (ERPs) were examined. The onset of motor preparation was determined by monitoring the lateralized readiness potential. In numerical comparison one facilitation effect was related to perceptual processing at the level of the magnitude representation. A second facilitation effect and interference effects appeared during response processing. In size comparison facilitation and interference appeared exclusively during response processing. In both tasks, ERP interference effects were probably related to contextual analysis and to the conflict monitoring and selection for action activity of the anterior cingulate cortex. The results demonstrate that facilitation and interference effects in the NSP appear during multiple stages of processing, and that they are related to different cognitive processes. Therefore these effects should be clearly separated in studies of the NSP. A model of the processes involved in the NSP is provided and implications for studies of the NSP are drawn.

Age-Related Changes and the Attention Network Task: An Examination of Alerting, Orienting, and Executive Function

The effects of aging on alerting, orienting, and executive function were examined with the use of the Attention Network Task, which combines the Posner spatial cuing task and the Eriksen flanker task into a single procedure. We found that older adults showed significantly less alerting than young adults in response to a warning cue, although there were no age differences in orienting or executive function once processing speed was taken into account. We suggest that age differences in alerting may depend in part upon the presentation duration or persistence of the warning cue.

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.

Dopaminergic modulation of cognitive interference after pharmacological washout in Parkinson's disease

The dopaminergic modulation of prefrontal function in Parkinson's disease (PD) has been consistently demonstrated. There is evidence that the effects of pharmacological manipulations on cognitive performances are described by an "Inverted-U" shaped curve. Neuroimaging studies performed before and after an overnight withdrawal from therapy showed significant differences between drug states, but did not control for the relative impact of the long duration response to levodopa. Here we evaluate the brain response after a complete pharmacological washout by correlating dopaminergic-related changes of this response to changes in performance during cognitive interference. Twelve idiopathic PD patients were studied with functional MRI while performing a modified version of the Stroop task. Patients were scanned twice: (1) following a prolonged washout procedure ("OFF" state) and (2) 90-120 min after the administration of levodopa ("ON" state). Task-related changes of PD patients were compared to those of matched healthy controls. Healthy controls displayed prefrontal and parietal responses that were positively correlated with task accuracy. In the "OFF" state, PD patients showed significant responses in anterior cingulate and pre-supplementary motor area, which are hypothesized to operate at a higher level of basal dopaminergic modulation. Levodopa administration attenuated such responses and enhanced the response of prefrontal cortex (PFC), which was correlated with improved accuracy. Results demonstrate that the behavioral effects of pharmacological manipulations of the dopamine system are highly dependent on the baseline status of PFC. When a true hypodopaminergic state is induced in PD patients, cognitive interference might significantly benefit from the administration of levodopa via an enhanced PFC response.

Effect of cigarette smoking on prefrontal cortical function in nondeprived smokers performing the Stroop Task

Some reports indicate that cigarette smoking can help smokers focus attention, even when they have not abstained from smoking for a substantial period of time (eg, >1 h). Understanding the mechanisms by which smoking affects attention may help in designing smoking cessation treatments. Thirteen nonsmokers and nine smokers participated in two tests of blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). During fMRI, the participants performed the Stroop Task. There was a 15-min break between the two tests. During the break, each smoker smoked one cigarette. For smokers, the first test began 45-60 min after the last cigarette of ad libitum smoking. The differences in BOLD signal changes between Stroop conditions (ie, incongruent minus congruent) showed a group x test interaction in the right precentral sulcus, including the putative human frontal eye field (FEF). Smokers, but not nonsmokers, showed greater changes (relative to rest) in BOLD signal in the incongruent than in the congruent condition in the first fMRI test but not in the second. Even after brief abstinence from smoking, therefore, smokers exhibit compromised functional efficiency in the right FEF and adjacent precentral sulcus in a test of selective attention; and smoking ameliorates this condition.

Corticolimbic dysregulation and chronic methamphetamine abuse

AIMS

This review aims to present and interpret evidence that methamphetamine dependence is associated with disorder of brain function that is required for top-down control of behavior.

APPROACH

Presented here are findings from brain imaging studies of human research participants with histories of chronic methamphetamine abuse in the context of functional consequences and implications for treatment of their dependence on methamphetamine.

FINDINGS

Brain imaging studies have revealed differences in the brains of research participants who have used methamphetamine chronically and then abstained from taking the drug, compared with healthy control subjects. These abnormalities are prominent in cortical and limbic systems, and include deficits in markers of dopaminergic and serotonergic neurotransmitter systems, differences in glucose metabolism and deficits in gray matter. These abnormalities accompany cognitive deficits, including evidence of impaired inhibitory control.

CONCLUSION

Cortical deficits in abstinent methamphetamine abusers can affect a wide range of functions that can be important for success in maintaining drug abstinence. These include but are not limited to modulation of responses to environmental stimuli as well as internal triggers that can lead to craving and relapse. Potential therapies may combine behavioral approaches with medications that can improve cognitive control.

Comparison of different cortical connectivity estimators for high-resolution EEG recordings

The aim of this work is to characterize quantitatively the performance of a body of techniques in the frequency domain for the estimation of cortical connectivity from high-resolution EEG recordings in different operative conditions commonly encountered in practice. Connectivity pattern estimators investigated are the Directed Transfer Function (DTF), its modification known as direct DTF (dDTF) and the Partial Directed Coherence (PDC). Predefined patterns of cortical connectivity were simulated and then retrieved by the application of the DTF, dDTF, and PDC methods. Signal-to-noise ratio (SNR) and length (LENGTH) of EEG epochs were studied as factors affecting the reconstruction of the imposed connectivity patterns. Reconstruction quality and error rate in estimated connectivity patterns were evaluated by means of some indexes of quality for the reconstructed connectivity pattern. The error functions were statistically analyzed with analysis of variance (ANOVA). The whole methodology was then applied to high-resolution EEG data recorded during the well-known Stroop paradigm. Simulations indicated that all three methods correctly estimated the simulated connectivity patterns under reasonable conditions. However, performance of the methods differed somewhat as a function of SNR and LENGTH factors. The methods were generally equivalent when applied to the Stroop data. In general, the amount of available EEG affected the accuracy of connectivity pattern estimations. Analysis of 27 s of nonconsecutive recordings with an SNR of 3 or more ensured that the connectivity pattern could be accurately recovered with an error below 7% for the PDC and 5% for the DTF. In conclusion, functional connectivity patterns of cortical activity can be effectively estimated under general conditions met in most EEG recordings by combining high-resolution EEG techniques, linear inverse estimation of the cortical activity, and frequency domain multivariate methods such as PDC, DTF, and dDTF.

Autonomic arousal in cognitive conflict resolution

Although cognitive efforts were reported to elicit global autonomic arousal, which cognitive processes associate with autonomic arousal has not been clear. We investigated autonomic arousal using event-related skin conductance responses (SCRs) during the Stroop color-word task. After baseline SCR deflections were determined in each trial block, SCRs were compared between cognitive conflict conditions (incongruent vs. congruent stimuli), between tasks assigned (word reading vs. color naming), and between erroneous and correct responses. Baseline SCRs were significantly greater at the beginning of each trial block. SCRs were significantly greater with incongruent than congruent stimuli while SCRs differed little between word reading and color naming. SCRs were greater when responses were incorrect. The results suggested that autonomic arousal occurs during cognitive conflict resolution in addition to mental set adoption for a task and in error awareness.

Imaging informational conflict: a functional magnetic resonance imaging study of numerical stroop

We employed a parametric version of the comparison Stroop paradigm to investigate the processing of numerical magnitude and physical size under task-relevant and -irrelevant conditions to investigate two theoretical issues: (1) What is the neural fate of task-irrelevant information? (2) What is the neural basis of the resolution of the conflict between task-relevant and -irrelevant information? We show in 18 healthy adults that numerical magnitudes of numbers call for higher processing requirements than physical sizes. The enhanced activation elicited by numerical magnitudes is not modulated by task relevance, indicating autonomous processing. Moreover, the normal behavioral distance effect when the numerical dimension is task relevant and reversed distance effect when it is not show that autonomous processing fully encodes numerical magnitudes. Conflict trials elicited greater activation in bilateral inferior frontal gyri, right middle frontal gyri, and right superior frontal gyri. We postulate two sources to the conflict, namely, at cognitive and response levels.

Neural correlates of semantic priming for ambiguous words: An event-related fMRI study

We investigated the neural correlates of semantic priming by using event-related fMRI to record blood oxygen level dependent (BOLD) responses while participants performed speeded lexical decisions (word/nonword) on visually presented related versus unrelated prime-target pairs. A long stimulus onset asynchrony of 1000 ms was employed, which allowed for increased controlled processing and selective frequency-based ambiguity priming. Conditions included an ambiguous word prime (e.g. bank) and a target related to its dominant (e.g. money) or subordinate meaning (e.g. river). Compared to an unrelated condition, primed dominant targets were associated with increased activity in the LIFG, the right anterior cingulate and superior temporal gyrus, suggesting postlexical semantic integrative mechanisms, while increased right supramarginal activity for the unrelated condition was consistent with expectancy based priming. Subordinate targets were not primed and were associated with reduced activity primarily in occipitotemporal regions associated with word recognition, which may be consistent with frequency-based meaning suppression. These findings provide new insights into the neural substrates of semantic priming and the functional-anatomic correlates of lexical ambiguity suppression mechanisms.

Correlates of Stimulus-Response Congruence in the Posterior Parietal Cortex

Primate behavior is flexible: The response to a stimulus often depends on the task in which it occurs. Here we study how single neurons in the posterior parietal cortex (PPC) respond to stimuli which are associated with different responses in different tasks. Two rhesus monkeys performed a task-switching paradigm. Each trial started with a task cue instructing which of two tasks to perform, followed by a stimulus requiring a left or right button press. For half the stimuli, the associated responses were different in the two tasks, meaning that the task context was necessary to disambiguate the incongruent stimuli. The other half of stimuli required the same response irrespective of task context (congruent). Using this paradigm, we previously showed that behavioral responses to incongruent stimuli are significantly slower than to congruent stimuli. We now demonstrate a neural correlate in the PPC of the additional processing time required for incongruent stimuli. Furthermore, we previously found that 29% of parietal neurons encode the task being performed (task-selective cells). We now report differences in neuronal timing related to congruency in task-selective versus task nonselective cells. These differences in timing suggest that the activity in task nonselective cells reflects a motor command, whereas activity in task-selective cells reflects a decision process.

Identification by [99mTc]ECD SPECT of anterior cingulate hypoperfusion in progressive supranuclear palsy, in comparison with Parkinson's disease

PURPOSE

Progressive supranuclear palsy (PSP) is an akinetic-rigid syndrome that can be difficult to differentiate from Parkinson's disease (PD), particularly at an early stage. [99mTc]ethyl cysteinate dimer (ECD) SPECT could represent a widely available tool to assist in the differential diagnosis. In this study we used voxel-based analysis and Computerised Brain Atlas (CBA)-based principal component analysis (PCA) of [99mTc]ECD SPECT data to test whether: (1) specific patterns of rCBF abnormalities can differentiate PSP from controls and PD; (2) networks of dysfunctional brain regions can be found in PSP vs controls and PD.

METHODS

Nine PD patients, 16 PSP patients and ten controls were studied with [99mTc]ECD SPECT using a brain-dedicated device (Ceraspect). Voxel-based analysis was performed with statistical parametric mapping. PCA was applied to volume of interest data after spatial normalisation to CBA.

RESULTS

The voxel-based analysis showed hypoperfusion of the anterior cingulate and medial frontal cortex in PSP compared with controls and PD. In PSP patients the rCBF impairment extended to the pre-supplementary motor area and prefrontal cortex, areas involved in executive function and motor networks. Compared with PSP patients, PD patients showed a mild rCBF decrease in associative visual areas which could be related to the known impairment of visuospatial function. The PCA identified three principal components differentiating PSP patients from controls and/or PD patients that included groups of cortical and subcortical brain regions with relatively decreased (cingulate cortex, prefrontal cortex and caudate) or increased (parietal cortex) rCBF, representing distinct functional networks in PSP.

CONCLUSION

Anterior cingulate hypoperfusion seems to be an early, distinct brain abnormality in PSP as compared with PD.

Post-error adaptation in adults with high functioning autism

Deficits in executive function (EF), i.e. function of the prefrontal cortex, may be central in the etiology of autism. One of the various aspects of EF is error detection and adjusting behavior after an error. In cognitive tests, adults normally slow down their responding on the next trial after making an error, a compensatory mechanism geared toward improving performance on subsequent trials, and a faculty critically associated with activity in the anterior cingulate cortex (ACC). The current study evaluated post-error slowing in people with high functioning autism (HFA) (n=36), taking symptom severity into account, compared to the performance of a normal control group (n=32). Symptom severity in the HFA group was defined in terms of level of adaptation: living independently (outpatients; n=12) and living residentially (inpatients; n=24). Half the group of inpatients was on medication; the results of their performance were analyzed separately. A computerized version of a memory search task was used with two response probability conditions. The subjects in the control group adjusted their reaction time (RT) substantially after an error, while the group of participants with HFA appeared to be overall slow, with no significant adjustment of RT after an error. This finding remained significant if the medication factor was taken into account, and was independent of the degree of severity of the autistic disorder, as defined by the dichotomy 'inpatient versus outpatient'. Possible causes and implications of the finding are discussed.

Conundrums in the use of observational measures of socioemotional behavior

The potential for translation of observational measures of social and emotional behavior used in small-scale studies for use in large-, possibly national-scale, studies of child development is currently an unresolved challenge. To begin to address this issue, the advantages and disadvantages to using observational measures of social and emotional behavior are discussed. In addition, alternatives to observational measures that may be helpful in assessing social and emotional behavior are considered with special emphasis on the benefits of cognitive measures.