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

An fMRI study of anterior cingulate function in posttraumatic stress disorder

BACKGROUND

Several recent neuroimaging studies have provided data consistent with functional abnormalities in anterior cingulate cortex in posttraumatic stress disorder (PTSD). In our study, we implemented a cognitive activation paradigm to test the functional integrity of anterior cingulate cortex in PTSD.

METHODS

Eight Vietnam combat veterans with PTSD (PTSD Group) and eight Vietnam combat veterans without PTSD (non-PTSD Group) underwent functional magnetic resonance imaging (fMRI) while performing the Emotional Counting Stroop. In separate conditions, subjects counted the number of combat-related (Combat), generally negative (General Negative), and neutral (Neutral) words presented on a screen and pressed a button indicating their response.

RESULTS

In the Combat versus General Negative comparison, the non-PTSD group exhibited significant fMRI blood oxygenation level-dependent signal increases in rostral anterior cingulate cortex, but the PTSD group did not.

CONCLUSIONS

These findings suggest a diminished response in rostral anterior cingulate cortex in the presence of emotionally relevant stimuli in PTSD. We speculate that diminished recruitment of this region in PTSD may, in part, mediate symptoms such as distress and arousal upon exposure to reminders of trauma.

The relative involvement of anterior cingulate and prefrontal cortex in attentional control depends on nature of conflict

While numerous studies have implicated both anterior cingulate and prefrontal cortex in attentional control, the nature of their involvement remains a source of debate. Here we determine the extent to which their relative involvement in attentional control depends upon the levels of processing at which the conflict occurs (e.g., response, non-response). Using a combination of blocked and rapid presentation event-related functional magnetic resonance imaging techniques, we compared neural activity during incongruent Stroop trial types that produce conflict at different levels of processing. Our data suggest that the involvement of anterior cingulate and right prefrontal cortex in attentional control is primarily limited to situations of response conflict, while the involvement of left prefrontal cortex extends to the occurrence of conflict at non-response levels.

Neuroimaging correlates of negative priming

Many theoretical accounts of selective attention and memory retrieval include reference to active inhibitory processes, such as those argued to underlie the negative priming effect. fMRI was used in order to investigate the areas of cortical activation associated with Stroop interference, Stroop facilitation and Stroop negative priming tasks. The most significant activation within the negative priming task was within the inferior parietal lobule, left temporal lobe and frontal lobes. Areas of cortical activation are discussed with reference to theoretical accounts of the negative priming effect.

The role of the anterior cingulate cortex in conflict processing: evidence from reverse stroop interference

A recent theoretical account delineated the role of the anterior cingulate cortex (ACC) in cognitive control as the detection of conflict between competing information streams. Using functional magnetic resonance imaging, we examined the activity of this brain structure during different forms and degrees of conflict between the word and the color dimensions of Stroop stimuli. Overall, our results showed a dissociation between the degree of conflict and ACC activation. More specifically, although ACC activation was very extensive when print color interfered with word reading performance, the level of conflict, as measured by reaction time costs, was only moderate compared to other conditions. These results suggest that either the ACC is differentially sensitive to various types of conflict or its function should be extended to include other cognitive constructs, such as resolution of prior inhibition.

Persecutory delusions: a review and theoretical integration

Persecutory (paranoid) delusions are a frequently observed clinical phenomenon. In recent years, an increasing volume of research has attempted to explain these types of beliefs in terms of psychological mechanisms. Theories have emphasized early experience, perceptual abnormalities, motivational factors, and information-processing deficits. In this article we review relevant findings, including our own studies of the role of causal attributions and theory of mind deficits. We propose a new integrative model that builds on this work. The core of the model is an account of the way that causal attributions influence self-representations, which in turn influence future attributions: the attribution--self-representation cycle. We argue that biases in this cycle cause negative events to be attributed to external agents and hence contribute to the building of a paranoid world view. These abnormalities are amenable to investigation by functional neuroimaging, and recent studies have implicated specific areas of neuroactivation. However, these findings do not necessarily suggest that paranoid delusions are entirely biological in origin, and there is evidence that adverse early experience may play a role in determining the development of a cognitive vulnerability to paranoid thinking.

Electric source imaging of human brain functions

We review recent methodological advances in electromagnetic source imaging and present EEG data from our laboratory obtained by application of these methods. There are two principal steps in our analysis of multichannel electromagnetic recordings: (i) the determination of functionally relevant time periods in the ongoing electric activity and (ii) the localization of the sources in the brain that generate these activities recorded on the scalp. We propose a temporal segmentation of the time-varying activity, which is based on determination of changes in the topography of the electric fields, as an approach to the first step, and a distributed linear inverse solution based on realistic head models as an approach to the second step. Data from studies of visual motion perception, visuo-motor transfer, mental imagery, semantic decision, and cognitive interference illustrate that this analysis allows us to define the patterns of electric activity that are present at given time periods after stimulus presentation, as well as those time periods where significantly different patterns appear between different stimuli and tasks. The presented data show rapid and parallel activation of different areas within complex neuronal networks, including early activity of brain regions remote from the primary sensory areas. In addition, the data indicate information exchange between homologous areas of the two hemispheres in cases where unilateral stimulus presentation requires interhemispheric transfer.

Attention mechanisms in visual search -- an fMRI study

The human visual system is usually confronted with many different objects at a time, with only some of them reaching consciousness. Reaction-time studies have revealed two different strategies by which objects are selected for further processing: an automatic, efficient search process, and a conscious, so-called inefficient search [Treisman, A. (1991). Search, similarity, and integration of features between and within dimensions. Journal of Experimental Psychology: Human Perception and Performance, 17, 652--676; Treisman, A., & Gelade, G. (1980). A feature integration theory of attention. Cognitive Psychology, 12, 97--136; Wolfe, J. M. (1996). Visual search. In H. Pashler (Ed.), Attention. London: University College London Press]. Two different theories have been proposed to account for these search processes. Parallel theories presume that both types of search are treated by a single mechanism that is modulated by attentional and computational demands. Serial theories, in contrast, propose that parallel processing may underlie efficient search, but inefficient searching requires an additional serial mechanism, an attentional "spotlight" (Treisman, A., 1991) that successively shifts attention to different locations in the visual field. Using functional magnetic resonance imaging (fMRI), we show that the cerebral networks involved in efficient and inefficient search overlap almost completely. Only the superior frontal region, known to be involved in working memory [Courtney, S. M., Petit, L., Maisog, J. M., Ungerleider, L. G., & Haxby, J. V. (1998). An area specialized for spatial working memory in human frontal cortex. Science, 279, 1347--1351], and distinct from the frontal eye fields, that control spatial shifts of attention, was specifically involved in inefficient search. Activity modulations correlated with subjects' behavior best in the extrastriate cortical areas, where the amount of activity depended on the number of distracting elements in the display. Such a correlation was not observed in the parietal and frontal regions, usually assumed as being involved in spatial attention processing. These results can be interpreted in two ways: the most likely is that visual search does not require serial processing, otherwise we must assume the existence of a serial searchlight that operates in the extrastriate cortex but differs from the visuospatial shifts of attention involving the parietal and frontal regions.

Neural activation during response competition

The flanker task, introduced by Eriksen and Eriksen [Eriksen, B. A., & Eriksen, C. W. (1974). Effects of noise letters upon the identification of a target letter in a nonsearch task. Perception & Psychophysics, 16, 143--149], provides a means to selectively manipulate the presence or absence of response competition while keeping other task demands constant. We measured brain activity using functional magnetic resonance imaging (fMRI) during performance of the flanker task. In accordance with previous behavioral studies, trials in which the flanking stimuli indicated a different response than the central stimulus were performed significantly more slowly than trials in which all the stimuli indicated the same response. This reaction time effect was accompanied by increases in activity in four regions: the right ventrolateral prefrontal cortex, the supplementary motor area, the left superior parietal lobe, and the left anterior parietal cortex. The increases were not due to changes in stimulus complexity or the need to overcome previously learned associations between stimuli and responses. Correspondences between this study and other experiments manipulating response interference suggest that the frontal foci may be related to response inhibition processes whereas the posterior foci may be related to the activation of representations of the inappropriate responses.

Cognitive interference is associated with neuronal marker N-acetyl aspartate in the anterior cingulate cortex: an in vivo (1)H-MRS study of the Stroop Color-Word task

The neurobiology of cognitive interference is unknown. Previous brain imaging studies using the Stroop Color-Word (SCW) task indicate involvement of the cingulate cortex cognitive division. The present study examines interrelationships between regional brain N-Acetyl aspartate (NAA) levels (as identified by in vivo proton magnetic resonance spectroscopy in the right and left anterior cingulate cortex (ACC), dorsolateral prefrontal cortex, orbitofrontal cortex and thalamus) and cognitive interference (as measured by the SCW task) in 15 normal subjects. The results show that brain chemistry depends on cognitive interference levels (high vs low). Reduction of NAA levels was demonstrated in the right ACC (ie, cognitive midsupracallosal division) of high interference subjects, as compared to the low interference group (P < 0.01, two-tailed t-test). Chemical-cognitive relationships were analyzed by calculating correlations between regional NAA levels and the SCW task scores. Cognitive interference was highly correlated with the right anterior cingulate NAA (r = 0.76, P < 0.001), and was unrelated to other studied regional NAA, including the left ACC (P < 0.025; comparing the difference between r values in the right and left ACC). The interrelationships between NAA across brain regions were examined using correlation analysis (square matrix correlation maps), which detected different connectivity patterns between the two groups. These findings provide evidence of ACC involvement in cognitive interference suggesting a possibility of neuronal reorganization in the physiological mechanism of interference (most likely due to genetically predetermined control of the number of neurons, dendrites and receptors, and their function). We conclude that spectroscopic brain mapping of NAA, the marker of neuronal density and function, to the SCW task measures differentiates between high and low interference in normal subjects. This neuroimaging/cognitive tool may be useful for documentation of interference in studying cognitive control mechanisms, and in diagnosis of neuropsychiatric disorders where dysfunction of cingulate cortex is expected.

On the tip of the tongue: an event-related fMRI study of semantic retrieval failure and cognitive conflict

The tip of the tongue (TOT) state refers to a temporary inaccessibility of information that one is sure exists in long-term memory and is on the verge of recovering. Using event-related fMRI, we assessed the neural correlates of this semantic retrieval failure to determine whether the anterior cingulate-lateral prefrontal neural circuit posited to mediate conflict resolution is engaged during metacognitive conflicts that arise during the TOT. Results revealed that, relative to successful retrieval or unsuccessful retrieval not accompanied by a TOT, retrieval failures accompanied by TOTs elicited a selective response in anterior cingulate-prefrontal cortices. During a TOT, cognitive control mechanisms may be recruited in attempts to resolve the conflict and retrieval failure that characterize this state.

Encoding novel face-name associations: a functional MRI study

The process of forming new associations between previously unrelated items of information, such as a name and a face, likely requires the integration of activity within multiple brain regions. The hippocampus and related structures in the medial temporal lobe are thought to be particularly critical in binding together items of information. We studied eight healthy young subjects with functional magnetic resonance imaging (fMRI) during the encoding of novel face-name associations compared to viewing repeated face-name pairs. A consistent pattern of activation was observed in the hippocampus, pulvinar nucleus of the thalamus, fusiform and dorsolateral prefrontal cortices across individual subjects. The location of the activation within the hippocampus was more anterior than previously reported in studies using similar novel vs. repeated paradigms with stimuli that did not specifically require relational processing among unrelated items. These data suggest that the process of forming new face-name associations is supported by a distributed network of brain regions, and provide additional evidence for the essential role of the hippocampus in associative memory processes.

The functional anatomy of inhibition processes investigated with the Hayling task

The cortical areas involved in inhibition processes were examined with positron emission tomography (PET). The tasks administered to subjects were an adaptation of the Hayling test. In the first condition (response initiation), subjects had to complete sentences with a word clearly suggested by the context, whereas in the second condition (response inhibition), subjects had to produce a word that made no sense in the context of the sentence. Results indicated that the response initiation processes were associated to increases of activity in the left inferior frontal gyrus (BA 45/47), whereas response inhibition processes led to increases in a network of left prefrontal areas, including the middle (BA 9 and BA 10) and inferior (BA 45) frontal areas.

Conflict monitoring and cognitive control

A neglected question regarding cognitive control is how control processes might detect situations calling for their involvement. The authors propose here that the demand for control may be evaluated in part by monitoring for conflicts in information processing. This hypothesis is supported by data concerning the anterior cingulate cortex, a brain area involved in cognitive control, which also appears to respond to the occurrence of conflict. The present article reports two computational modeling studies, serving to articulate the conflict monitoring hypothesis and examine its implications. The first study tests the sufficiency of the hypothesis to account for brain activation data, applying a measure of conflict to existing models of tasks shown to engage the anterior cingulate. The second study implements a feedback loop connecting conflict monitoring to cognitive control, using this to simulate a number of important behavioral phenomena.

Progress in the neural sciences in the the century after Cajal (and the mysteries that remain)

One hundred years after Santiago Ramon y Cajal provided critical evidence for the "neuron doctrine," his cellular view of the brain remains the basis of modern neural science. This article begins with a review of how the early work of Ramon y Cajal, Charles Sherrington, and John Eccles and their contemporaries laid the groundwork for our current understanding of he information processing of neural systems and for understanding the task faced by studies of how the brain develops. The visual system is examined in some detail as a model for experimental investigation into the structure, operational mechanisms, and functions of large neural systems. Discussion of the phenomena of visual awareness and consciousness, links between the visual system and other brain systems, and disorders that disrupt voluntary control of cognition and emotion lead to a broader consideration of the problem of consciousness.

Brain imaging of attention deficit/hyperactivity disorder

Advances in imaging technology allow unprecedented access to the anatomy and physiology of the living, growing human brain. Anatomical imaging studies of individuals with attention deficit/hyperactivity disorder (ADHD) consistently point to involvement of the frontal lobes, basal ganglia, corpus callosum, and cerebellum. Imaging studies of brain physiology also support involvement of right frontal-basal ganglia circuitry with a powerful modulatory influence from the cerebellum. Although not currently of diagnostic utility, further extension and refinement of these findings may offer hope for greater understanding of the core nature of ADHD and possible subtyping to inform treatment interventions.

Effects of attention and emotion on face processing in the human brain: an event-related fMRI study

We used event-related fMRI to assess whether brain responses to fearful versus neutral faces are modulated by spatial attention. Subjects performed a demanding matching task for pairs of stimuli at prespecified locations, in the presence of task-irrelevant stimuli at other locations. Faces or houses unpredictably appeared at the relevant or irrelevant locations, while the faces had either fearful or neutral expressions. Activation of fusiform gyri by faces was strongly affected by attentional condition, but the left amygdala response to fearful faces was not. Right fusiform activity was greater for fearful than neutral faces, independently of the attention effect on this region. These results reveal differential influences on face processing from attention and emotion, with the amygdala response to threat-related expressions unaffected by a manipulation of attention that strongly modulates the fusiform response to faces.

Control of semantic interference in episodic memory retrieval is associated with an anterior cingulate-prefrontal activation pattern

Prefrontal activation is a consistent finding in functional neuroimaging studies of episodic memory retrieval. In the present study we aimed at a further analysis of prefrontal neural systems involved in the executive control of context-specific properties in episodic memory retrieval using an event-related fMRI design. Nine subjects were asked to learn two 20-item word lists that consisted of concrete nouns assigned to four semantic categories. Ten items of both word lists referred to the same semantic category. Subjects were instructed to determine whether nouns displayed in random order corresponded to the first 20-item target list. The interference evoked by the retrieval of semantically related items of the second list resulted in significantly longer reaction times compared to the noninterference condition. Contrasting the interference against the noninterference retrieval condition demonstrated an activation pattern that comprised a right anterior cingulate and frontal opercular area and a left-lateralized dorsolateral prefrontal region. Trial averaged time series revealed that the PFC areas were selectively activated at the interference condition and did not respond to the familiarity of learned words. These findings suggest a functionally separable role of prefrontal cortical areas mediating processes associated with the executive control of interfering context information in episodic memory retrieval.

Deficits in visual cognition and attention following bilateral anterior cingulotomy

A series of eight tests of visual cognitive abilities was used to examine pre- to post-operative performance changes in a patient receiving bilateral anterior cingulotomy. Compared with a set of eight matched control participants, post-operatively, the patient exhibited deficits in (a) the ability to sequence novel cognitive operations required to generate multipart images or rotate perceptual stimuli; (b) the ability to search for, select, and compare images of objects when the instructions did not specify precisely which objects should be visualized; and, (c) the ability to select a controlled and unpracticed response over an automatic one. Other imagery and cognitive tasks were not affected. Results are consistent with the hypothesis that anterior cingulate cortex is a component of an executive control system. One of the anterior cingulate's roles may be to monitor on-line processing and signal the motivational significance of current actions or cognitions.

Frontal midline theta rhythm is correlated with cardiac autonomic activities during the performance of an attention demanding meditation procedure

Frontal midline theta rhythm (Fm theta), recognized as distinct theta activity on EEG in the frontal midline area, reflects mental concentration as well as meditative state or relief from anxiety. Attentional network in anterior frontal lobes including anterior cingulate cortex is suspected to be the generator of this activity, and the regulative function of the frontal neural network over autonomic nervous system (ANS) during cognitive process is suggested. However no studies have examined peripheral autonomic activities during Fm theta induction, and interaction of central and peripheral mechanism associated with Fm theta remains unclear. In the present study, a standard procedure of Zen meditation requiring sustained attention and breath control was employed as the task to provoke Fm theta, and simultaneous EEG and ECG recordings were performed. For the subjects in which Fm theta activities were provoked (six men, six women, 48% of the total subjects), peripheral autonomic activities were evaluated during the appearance of Fm theta as well as during control periods. Successive inter-beat intervals were measured from the ECG, and a recently developed method of analysis by Toichi et al. (J. Auton. Nerv. Syst. 62 (1997) 79-84) based on heart rate variability was used to assess cardiac sympathetic and parasympathetic functions separately. Both sympathetic and parasympathetic indices were increased during the appearance of Fm theta compared with control periods. Theta band activities in the frontal area were correlated negatively with sympathetic activation. The results suggest a close relationship between cardiac autonomic function and activity of medial frontal neural circuitry.

Activation of the left amygdala to a cognitive representation of fear

We examined the neural substrates involved when subjects encountered an event linked verbally, but not experientially, to an aversive outcome. This instructed fear task models a primary way humans learn about the emotional nature of events. Subjects were told that one stimulus (threat) represents an aversive event (a shock may be given), whereas another (safe) represents safety (no shock will be given). Using functional magnetic resonance imaging (fMRI), activation of the left amygdala was observed in response to threat versus safe conditions, which correlated with the expression of the fear response as measured by skin conductance. Additional activation observed in the insular cortex is proposed to be involved in conveying a cortical representation of fear to the amygdala. These results suggest that the neural substrates that support conditioned fear across species have a similar but somewhat different role in more abstract representations of fear in humans.

Stroop interference and facilitation effects in first-episode schizophrenic patients

In the Stroop test, interference occurs in naming the print color of a word when the word is itself the name of another color. Facilitation occurs when the word is the same as the print color. Previous studies on selective attention in schizophrenia using the Stroop interference effects have yielded contradicting results. Constraints included limited sample size and the recruitment of medicated chronic patients. We studied the Stroop interference and facilitation effects in a relatively large sample of first-episode schizophrenic patients (n=56), a substantial proportion of whom were medication-naïve (n=30) at the time of initial testing. We have also carried out longitudinal follow-up assessments when patients reached a clinically stable state, as well as 4months after recovery from the episode. We found that the Stroop interference effect was not increased in first-episode schizophrenic patients, whether medication-naïve or not. This effect did not change over the follow-up period. In addition, we detected an increase in Stroop facilitation effect in medicated schizophrenic patients, but only in the initial assessment soon after they had received medication. After sustained treatment, the increase in facilitation was normalized. These observations supported previous findings of a normal Stroop interference effect amongst schizophrenic patients. The increased facilitation effect for patients in their early phase of treatment (but not later) may represent an acute effect of anti-psychotic medication. Its nature and significance require further investigation.

Emotional and personality changes following cingulotomy

The effects of bilateral anterior cingulate cortex (ACC) lesions on emotional and personality functioning were studied. Patients undergoing cingulotomy for chronic intractable pain were assessed on the Minnesota Multiphasic Personality Inventory (MMPI), the Profile of Mood States (POMS), cognitive tests, and pain ratings, pre- and postsurgically. Patients with intractable pain, not treated with cingulotomy, served as controls. Cingulotomy patients experienced reductions in POMS-Tension, POMS-Anger, and MMPI Scale 7 (Psychasthenia) compared with baseline and the controls. POMS-Tension was significantly correlated with attention-intention performance. The results indicate that the ACC modulates emotional experience, related to self-perceived tension, and that there is relationship between the emotional and the attentional effects of cingulotomy.

Regional cerebral blood flow abnormalities in early-onset obsessive-compulsive disorder: an exploratory SPECT study

OBJECTIVE

Recent epidemiological and clinical data suggest that obsessive-compulsive disorder (OCD) may be subtyped according the age of onset of obsessive-compulsive symptoms. The regional cerebral blood flow (rCBF) single photon emission computed tomography (SPECT) technique was used to investigate whether the pathophysiology of OCD differs between early- and late-onset OCD subjects.

METHOD

Resting rCBF was measured in 13 early-onset (<10 years) and 13 late-onset (>12 years) adult OCD subjects and in 22 healthy controls. Voxel-based rCBF comparisons were performed with statistical parametric mapping.

RESULTS

Early-onset OCD cases showed decreased rCBF in the right thalamus, left anterior cingulate cortex, and bilateral inferior prefrontal cortex relative to late-onset subjects (p < .0005, uncorrected for multiple comparisons). Relative to controls, early-onset cases had decreased left anterior cingulate and right orbitofrontal rCBF, and increased rCBF in the right cerebellum, whereas late-onset subjects showed reduced right orbitofrontal rCBF and increased rCBF in the left precuneus. In early-onset subjects only, severity of obsessive-compulsive symptoms correlated positively with left orbitofrontal rCBF.

CONCLUSIONS

rCBF differences in frontal-subcortical circuits between early-onset and late-onset OCD subjects were found, both in location and direction of changes. These results provide preliminary evidence that brain mechanisms in OCD may differ depending on the age at which symptoms are first expressed.

Differential prefrontal cortex and amygdala habituation to repeatedly presented emotional stimuli

Repeated presentations of emotional facial expressions were used to assess habituation in the human brain using fMRI. Significant fMRI signal decrement was present in the left dorsolateral prefrontal and premotor cortex, and right amygdala. Within the left prefrontal cortex greater habituation to happy vs fearful stimuli was evident, suggesting devotion of sustained neural resources for processing of threat vs safety signals. In the amygdala, significantly greater habituation was observed on the right compared to the left. In contrast, the left amygdala was significantly more activated than the right to the contrast of fear vs happy. We speculate that the right amygdala is part of a dynamic emotional stimulus detection system, while the left is specialized for sustained stimulus evaluations.

The classical stroop interference task as a prefrontal activation probe: a validation study using 99Tcm-ECD brain SPECT

This study investigated the feasibility of brain single photon emission computed tomography (SPECT) functional imaging in a neuropsychological test setting, following a single-day protocol with a split-dose paradigm. The Stroop Color Word Test (SCWT) is an example of a well-documented prefrontal activation task. In a split-dose protocol, ten right-handed healthy volunteers were injected twice with 370 MBq 99Tcm-ethyl cysteinate dimer while performing consecutively both series of card-reading of the SCWT. Images were reconstructed using filtered back-projection and normalized to a standard template in Talairach coordinates. Statistical Parametric Mapping (SPM96) was used to determine voxelwise significant changes. A first activation cluster was found in the left medial prefrontal cortex, consisting of the gyrus cinguli anterior and the gyrus frontalis medius and superior. A second activation cluster included the right gyrus frontalis dorsalis and medius. These findings confirm to a large extent the results of previous functional magnetic resonance imaging, positron emission tomography studies of Stroop-like tasks. The choice and validity of various methodological characteristics of the experimental design leading to these results is critically discussed. It is concluded that brain SPECT activation with the Stroop Color Word Test under standard neuropsychological conditions in healthy volunteers, is both technically and practically feasible.

The effect of stimulus-response compatibility on cortical motor activation

Stimulus-response compatibility (SRC) is a general term describing the relationship between a triggering stimulus and its associated motor response. The relationship between stimulus and response can be manipulated at the level of the set of stimulus and response characteristics (set-level) or at the level of the mapping between the individual elements of the stimulus and response sets (element-level). We used functional magnetic resonance imaging (fMRI) to investigate the effects of SRC on functional activation in cortical motor areas. Using behavioral tasks to separately evaluate set- and element-level compatibility, and their interaction, we measured the volume of functional activation in 11 cortical motor areas, in the anterior frontal cortex, and in the superior temporal lobe. Element-level compatibility effects were associated with significant activation in the pre-supplementary motor area (preSMA), the dorsal (PMd) and ventral (PMv) premotor areas, and the parietal areas (inferior, superior, intraparietal sulcus, precuneus). The activation was lateralized to the right hemisphere for most of the areas. Set-level compatibility effects resulted in significant activation in the inferior frontal gyri, anterior cingulate and cingulate motor areas, the PMd, PMv, preSMA, the parietal areas (inferior, superior, intraparietal sulcus, precuneus), and in the superior temporal lobe. Activation in the majority of these areas was lateralized to the left hemisphere. Finally, there was an interaction between set and element-level compatibility in the middle and superior frontal gyri, in an area co-extensive with the dorsolateral prefrontal cortex, suggesting that this area provided the neural substrate for common processing stages, such as working memory and attention, which are engaged when both levels of SRC are manipulated at once.

Deriving numerosity and shape from identical visual displays

We presented identical displays of three to five dots in a functional magnetic resonance imaging (fMRI) experiment with normal volunteers. Two distinct directed attention tasks were performed on these displays: In one condition, subjects assessed the numerosity of the display; in the other condition, they assessed the shape of the display. Decisions based on numerosity activated differentially striate and extrastriate visual processing areas as well as left inferior frontal cortex. Decisions based on shape derived from arrangement activated differentially temporoparietal cortex bilaterally, medial posterior cingulate cortex, and left dorsolateral prefrontal cortex. These divergent neural activations in response to identical stimuli suggest that attentional mechanisms are deployed in very different ways in rapid enumeration of visual objects and in linking spatially discrete elements to one form.

The effect of medial frontal and posterior parietal demyelinating lesions on stroop interference

Functional imaging has consistently shown that attention-related areas of medial frontal and posterior parietal cortices are active during the attentional conflict induced by color naming in the presence of distracting words (Stroop task). Such studies, however, have provided few details of the correlational nature between observed regional brain activations and reaction time delay occurring in this situation. We analyzed the effect of medial frontal and posterior parietal lesions on the Stroop response in a group of patients with multiple sclerosis, a neurological disorder in which Stroop response speed is affected to varying degrees. Forty-five patients were assessed using a computer-presented verbal version of the Stroop task and specific MRI protocol. Demyelination areas were measured on five anatomical divisions of the medial frontal white matter and on white matter of the posterior parietal lobe. We found that a combination of frontal and parietal lesion measurements accounted for 45% of the Stroop interference time variance. Patients with more right frontal than left parietal demyelination showed slowed Stroop responses, whereas the predominance of lesions in the left posterior parietal region was associated with a reduced Stroop interference. These results may contribute to defining the specific participation of these attention-related brain areas in the conflict of attention represented by the Stroop paradigm. They also help to explain the variability of the Stroop effect in multiple sclerosis patients and suggest that the Stroop test does not assess just a single cognitive operation, but rather the combined effect of anatomically segregated neural processes.

Color-word matching stroop task: separating interference and response conflict

The Stroop interference task requires a person to respond to a specific dimension of a stimulus while suppressing a competing stimulus dimension. Previous PET and fMRI studies using the Color Stroop paradigm have shown increased activity in the "cognitive division" of the cingulate cortex. In our fMRI study with nine subjects, we used a Color-Word Matching Stroop task. A frontoparietal network, including structures in the lateral prefrontal cortex, the frontopolar region, the intraparietal sulcus, as well as the lateral occipitotemporal gyrus, was activated when contrasting the incongruent vs the neutral condition. However, no substantial activation in either the right or left hemisphere of the anterior cingulate cortex (ACC) was detected. In accordance with a series of recent articles, we argue that the ACC is not specifically involved in interference processes. The ACC seems rather involved in motor preparation processes which were controlled in the present Color-Word Matching Stroop task. We argue that the region around the banks of the inferior frontal sulcus is required to solve interference problems, a concept which can also be seen as a component of task set management.

Cognitive neuroscience: origins and promise

Both Freud and Wundt had hoped to base psychology on an understanding of the neural basis of mental events. Their efforts were unsuccessful because the structure and function of the human brain was not available for empirical study at the physiological level. Over the last part of this century, there has been amazing growth and vitality in the field of human brain function. In this paper, we trace critical developments in the fields of cognitive psychology, neuropsychology, and brain imaging related to the development of cognitive neuroscience. Cognitive Neuroscience has established that the decomposition of mental events can be united with an understanding of the mental and emotional computations carried out by the human brain. Cognitive neuroscience has the capability of influencing psychology in diverse areas from how children develop to how adults age; from how humans learn to how we imagine; from volitional control to psychopathologies.

The functional neuroanatomy of simple calculation and number repetition: A parametric PET activation study

We examined cerebral activation patterns with positron emission tomography (PET) in 12 right-handed normal volunteers while they were completing simple calculation tasks or merely repeating numbers. Using a parametric experimental design, during calculation we found activation in the medial frontal/cingulate gyri, left dorsolateral prefrontal cortex, left anterior insular cortex and right anterior insular cortex/putamen, left lateral parietal cortex, and the medial thalamus. Number repetition engaged bilateral inferior sensorimotor cortex, bilateral temporal areas, and left inferior frontal cortex. These results suggest a functional anatomical network for simple calculation, which includes aspects of attention, auditory, and motor processing and the phonological store and articulatory loop components of working memory; they add some support for a special role of the parietal cortex in calculation tasks.

fMri studies of Stroop tasks reveal unique roles of anterior and posterior brain systems in attentional selection

The brain's attentional system identifies and selects information that is task-relevant while ignoring information that is task-irrelevant. In two experiments using functional magnetic resonance imaging, we examined the effects of varying task-relevant information compared to task-irrelevant information. In the first experiment, we compared patterns of activation as attentional demands were increased for two Stroop tasks that differed in the task-relevant information, but not the task-irrelevant information: a color-word task and a spatial-word task. Distinct subdivisions of dorsolateral prefrontal cortex and the precuneus became activated for each task, indicating differential sensitivity of these regions to task-relevant information (e.g., spatial information vs. color). In the second experiment, we compared patterns of activation with increased attentional demands for two Stroop tasks that differed in task-irrelevant information, but not task-relevant information: a color-word task and color-object task. Little differentiation in activation for dorsolateral prefrontal and precuneus regions was observed, indicating a relative insensitivity of these regions to task-irrelevant information. However, we observed a differentiation in the pattern of activity for posterior regions. There were unique areas of activation in parietal regions for the color-word task and in occipitotemporal regions for the color-object task. No increase in activation was observed in regions responsible for processing the perceptual attribute of color. The results of this second experiment indicate that attentional selection in tasks such as the Stroop task, which contain multiple potential sources of relevant information (e.g., the word vs. its ink color), acts more by modulating the processing of task-irrelevant information than by modulating processing of task-relevant information.

Interdimensional interference in the Stroop effect: uncovering the cognitive and neural anatomy of attention

In the classic Stroop effect, naming the color of an incompatible color word (e.g. the word RED printed in green ink; say, 'green') is much slower and more error-prone than is naming the color of a control item (e.g. XXX or CAT printed in green; say 'green'). This seemingly simple interference phenomenon has long provided a fertile testing ground for theories of the cognitive and neural components of selective attention. We present a sketch of the behavioral phenomenon, focusing on the idea that the relative automaticity of the two dimensions determines the direction and the degree of interdimensional interference between them. We then present an outline of current parallel processing explanations that instantiate this automaticity account, and we show how existing interference data are captured by such models. We also consider how Stroop facilitation (faster response of 'red' to RED printed in red) can be understood. Along the way, we describe research on two tasks that have emerged from the basic Stroop phenomenon - negative priming and the emotional Stroop task. Finally, we provide a survey of brain imaging research, highlighting the possible roles of the anterior cingulate in maintaining attentional set and in processing conflict or competition situations.

Cognitive neuroscience

The last decade of the 20th century has seen the development of cognitive neuroscience as an effort to understand how the brain represents mental events. We review the areas of emotional and motor memory, vision, and higher mental processes as examples of this new understanding. Progress in all of these areas has been swift and impressive, but much needs to be done to reveal the mechanisms of cognition at the local circuit and molecular levels. This work will require new methods for controlling gene expression in higher animals and in studying the interactions between neurons at multiple levels.

Common regions of the human frontal lobe recruited by diverse cognitive demands

Though many neuroscientific methods have been brought to bear in the search for functional specializations within prefrontal cortex, little consensus has emerged. To assess the contribution of functional neuroimaging, this article reviews patterns of frontal-lobe activation associated with a broad range of different cognitive demands, including aspects of perception, response selection, executive control, working memory, episodic memory and problem solving. The results show a striking regularity: for many demands, there is a similar recruitment of mid-dorsolateral, mid-ventrolateral and dorsal anterior cingulate cortex. Much of the remainder of frontal cortex, including most of the medial and orbital surfaces, is largely insensitive to these demands. Undoubtedly, these results provide strong evidence for regional specialization of function within prefrontal cortex. This specialization, however, takes an unexpected form: a specific frontal-lobe network that is consistently recruited for solution of diverse cognitive problems.

Functional imaging of brain responses to pain. A review and meta-analysis (2000)

Brain responses to pain, assessed through positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) are reviewed. Functional activation of brain regions are thought to be reflected by increases in the regional cerebral blood flow (rCBF) in PET studies, and in the blood oxygen level dependent (BOLD) signal in fMRI. rCBF increases to noxious stimuli are almost constantly observed in second somatic (SII) and insular regions, and in the anterior cingulate cortex (ACC), and with slightly less consistency in the contralateral thalamus and the primary somatic area (SI). Activation of the lateral thalamus, SI, SII and insula are thought to be related to the sensory-discriminative aspects of pain processing. SI is activated in roughly half of the studies, and the probability of obtaining SI activation appears related to the total amount of body surface stimulated (spatial summation) and probably also by temporal summation and attention to the stimulus. In a number of studies, the thalamic response was bilateral, probably reflecting generalised arousal in reaction to pain. ACC does not seem to be involved in coding stimulus intensity or location but appears to participate in both the affective and attentional concomitants of pain sensation, as well as in response selection. ACC subdivisions activated by painful stimuli partially overlap those activated in orienting and target detection tasks, but are distinct from those activated in tests involving sustained attention (Stroop, etc.). In addition to ACC, increased blood flow in the posterior parietal and prefrontal cortices is thought to reflect attentional and memory networks activated by noxious stimulation. Less noted but frequent activation concerns motor-related areas such as the striatum, cerebellum and supplementary motor area, as well as regions involved in pain control such as the periaqueductal grey. In patients, chronic spontaneous pain is associated with decreased resting rCBF in contralateral thalamus, which may be reverted by analgesic procedures. Abnormal pain evoked by innocuous stimuli (allodynia) has been associated with amplification of the thalamic, insular and SII responses, concomitant to a paradoxical CBF decrease in ACC. It is argued that imaging studies of allodynia should be encouraged in order to understand central reorganisations leading to abnormal cortical pain processing. A number of brain areas activated by acute pain, particularly the thalamus and anterior cingulate, also show increases in rCBF during analgesic procedures. Taken together, these data suggest that hemodynamic responses to pain reflect simultaneously the sensory, cognitive and affective dimensions of pain, and that the same structure may both respond to pain and participate in pain control. The precise biochemical nature of these mechanisms remains to be investigated.

Anxiety in healthy humans is associated with orbital frontal chemistry

The present study examines relationships between regional brain chemistry (as identified by localized in vivo three-dimensional single-voxel proton magnetic resonance spectroscopy (1H-MRS) and anxiety (as measured by the State-Trait Anxiety Inventory) in 16 healthy subjects. The relative concentrations of N-Acetyl aspartate, choline, glutamate, glutamine, gamma-aminobutyric acid, inositol, glucose and lactate were measured relative to creatine within six 8-cm3 brain voxels localized to: thalamus, cingulate, insula, sensorimotor, dorsolateral prefrontal, and orbital frontal cortices (OFC) in the left hemisphere. Analysis of variance, across brain regions, chemicals, and high and low anxiety groups, showed a relationship between anxiety and chemical composition of OFC, with high anxiety subjects demonstrating 32% increase in overall chemical concentrations within OFC, as compared to the lower anxiety group (F= 60.8, P < 10(-7)). Other brain regions, including cingulate, showed no detectable anxiety dependence. The combination of the state and trait anxiety was highly correlated with the concentration of OFC chemicals (r2 = 0.98), and N-Acetyl aspartate in OFC was identified as the strongest chemical marker for anxiety (changed by 43.2% between the two anxiety groups, F = 21.5, P = 0.000005). The results provide direct evidence that the OFC chemistry is associated with anxiety in healthy humans. The method can be used as a neuroimaging/behavioral tool for documentation of OFC chemistry changes in relation to anxiety per se and anxiety disorders. The presented relationship between regional brain chemistry and anxiety reflects the functional/behavioral state of the brain, pointing to possible mechanisms of the neurobiology of anxiety.

Effects of task context and fluctuations of attention on neural activity supporting performance of the stroop task

The influence of task context and transient fluctuations in attentional control on neural processes supporting performance of the Stroop task was investigated using event-related brain potentials. Task context was manipulated by varying the proportion of congruent and incongruent trials across different blocks of trials, and fluctuations of attentional control were considered by examining differences between trials eliciting faster and slower responses. The amplitudes of the N450, thought to reflect the suppression of a conceptual level processing system, and a temporo-parietal slow wave, thought to index the processing of color information, were greater when trials were mostly congruent in comparison to when trials were mostly incongruent. These findings indicate that the neural systems supporting inhibition and color processing are modulated by task demands. For the N450 the effect of task context interacted with the efficiency of attentional control being present for those trials eliciting faster responses and not for those trials eliciting slower responses. This finding is consistent with those from a growing number of studies indicating that the neural systems supporting attentional control are transient in nature, tending to fluctuate in efficiency over time.

Schizophrenic subjects show aberrant fMRI activation of dorsolateral prefrontal cortex and basal ganglia during working memory performance

BACKGROUND

Working memory (WM) deficits in schizophrenia have been associated with dorsolateral prefrontal cortex (DLPFC) dysfunction in neuroimaging studies. We previously found increased DLPFC activation in schizophrenic versus normal subjects during WM performance (Manoach et al 1999b). We now have investigated whether schizophrenic subjects recruit different brain regions, particularly the basal ganglia and thalamus, components of frontostriatal circuitry thought to mediate WM.

METHODS

We examined regional brain activation in nine normal and nine schizophrenic subjects during WM performance using functional magnetic resonance imaging. Subjects performed a modified version of the Sternberg Item Recognition Paradigm that included a monetary reward for correct responses. We compared high and low WM load conditions to each other and to a non-WM baseline condition. We examined activation in both individual subjects and averaged group data.

RESULTS

Relative to normal subjects, schizophrenic subjects exhibited deficient WM performance, at least an equal magnitude of right DLPFC activation, significantly greater left DLPFC activation, and increased spatial heterogeneity of DLPFC activation. Furthermore, only the schizophrenic group activated the basal ganglia and thalamus, even when matched for task performance with the normal group.

CONCLUSIONS

Aberrant WM performance and brain activation in schizophrenia may reflect dysfunction of frontostriatal circuitry that subserves WM. Future studies will elucidate the contribution of the anatomical components of this circuitry to WM deficits.

A voxel-based investigation of regional cerebral blood flow abnormalities in obsessive-compulsive disorder using single photon emission computed tomography (SPECT)

Several functional imaging studies have reported abnormalities of the orbitofrontal and anterior cingulate cortices, striatum and thalamus in obsessive-compulsive disorder (OCD). These studies have often been limited by small patient samples and image analysis methods that rely on region-of-interest (ROI) approaches. We have assessed resting regional cerebral blood flow with 99mTc-ECD SPECT in 26 unmedicated OCD patients and 22 healthy control subjects using the voxel-based Statistical Parametric Mapping method for data analysis. We found a significantly reduced ECD uptake in OCD patients relative to the control subjects in the right lateral orbitofrontal cortex, and in the left dorsal anterior cingulate cortex (P<0.001 two-tailed, uncorrected for multiple comparisons). There were significant positive correlations in the OCD group between the ECD uptake in the left lateral orbitofrontal cortex and ratings for obsessive-compulsive symptoms (OCS), and between the ECD uptake in the right medial orbitofrontal cortex and the ratings for both OCS and depressive symptoms. There were also unpredicted significant ECD uptake increases in the cerebellum in OCD patients, as well as a negative correlation between posterior cingulate ECD uptake and OCS severity (P<0.05, corrected for multiple testing). These results implicate specific subregions of the orbitofrontal and anterior cingulate cortices in the pathophysiology of OCD, as well as suggesting the involvement of other areas not usually included in ROI-based imaging studies. With the incorporation of voxel-based methods and the use of large patient samples, rCBF-SPECT studies may continue to provide valuable information about the functional anatomy of OCD.

Depth electrodes in clinical neurophysiology: neuronal activity and human cognitive function

Depth intracranial electrodes are used in medicine for the diagnosis and treatment of certain medically intractable disorders including epilepsy and parkinsonism. Electrophysiological studies including the recording of neuronal activity via depth electrodes during cognitive tasks allow the mapping of the functional significance of various brain regions for certain cognitive functions. Knowledge accumulated throughout the last several decades allows us to draw some theoretical inferences about neuronal mechanisms of human cognition. The present paper provides a selective review of studies of neuronal activity of the human brain in relation to language, verbal memory and error detection.

Activation of anterior paralimbic structures during guilt-related script-driven imagery

BACKGROUND

Several recent neuroimaging studies have examined the neuroanatomical correlates of normal emotional states, such as happiness, sadness, fear, anger, anxiety, and disgust; however, no previous study has examined the emotional state of guilt.

METHODS

In the current study, we used positron emission tomography and the script-driven imagery paradigm to study regional cerebral blood flow (rCBF) during the transient emotional experience of guilt in eight healthy male participants. In the Guilt condition, participants recalled and imagined participating in a personal event involving the most guilt they had ever experienced. In the Neutral condition, participants recalled and imagined participating in an emotionally neutral personal event.

RESULTS

In the Guilt versus Neutral comparison, rCBF increases occurred in anterior paralimbic regions of the brain: bilateral anterior temporal poles, anterior cingulate gyrus, and left anterior insular cortex/inferior frontal gyrus.

CONCLUSIONS

These results, along with those of previous studies, are consistent with the notion that anterior paralimbic regions of the brain mediate negative emotional states in healthy individuals.

Executive attention and metacognitive regulation

Metacognition refers to any knowledge or cognitive process that monitors or controls cognition. We highlight similarities between metacognitive and executive control functions, and ask how these processes might be implemented in the human brain. A review of brain imaging studies reveals a circuitry of attentional networks involved in these control processes, with its source located in midfrontal areas. These areas are active during conflict resolution, error correction, and emotional regulation. A developmental approach to the organization of the anatomy involved in executive control provides an added perspective on how these mechanisms are influenced by maturation and learning, and how they relate to metacognitive activity.

Cognitive and emotional influences in anterior cingulate cortex

Anterior cingulate cortex (ACC) is a part of the brain's limbic system. Classically, this region has been related to affect, on the basis of lesion studies in humans and in animals. In the late 1980s, neuroimaging research indicated that ACC was active in many studies of cognition. The findings from EEG studies of a focal area of negativity in scalp electrodes following an error response led to the idea that ACC might be the brain's error detection and correction device. In this article, these various findings are reviewed in relation to the idea that ACC is a part of a circuit involved in a form of attention that serves to regulate both cognitive and emotional processing. Neuroimaging studies showing that separate areas of ACC are involved in cognition and emotion are discussed and related to results showing that the error negativity is influenced by affect and motivation. In addition, the development of the emotional and cognitive roles of ACC are discussed, and how the success of this regulation in controlling responses might be correlated with cingulate size. Finally, some theories are considered about how the different subdivisions of ACC might interact with other cortical structures as a part of the circuits involved in the regulation of mental and emotional activity.

Prefrontal-cingulate interactions in action monitoring

We found that medial frontal cortex activity associated with action monitoring (detecting errors and behavioral conflict) depended on activity in the lateral prefrontal cortex. We recorded the error-related negativity (ERN), an event-related brain potential proposed to reflect anterior cingulate action monitoring, from individuals with lateral prefrontal damage or age-matched or young control participants. In controls, error trials generated greater ERN activity than correct trials. In individuals with lateral prefrontal damage, however, correct-trial ERN activity was equal to error-trial ERN activity. Lateral prefrontal damage also affected corrective behavior. Thus the lateral prefrontal cortex seemed to interact with the anterior cingulate cortex in monitoring behavior and in guiding compensatory systems.

Analysis of activation in anterior cingulate cortex during cognitive process of selection following somatosensory stimuli: fMRI study with elaborate task paradigms

The anterior cingulate cortex (ACC) has been pointed out to play an important role in the cognitive process of selection underlying "early selection" of perceptually (visually or auditorily) and "late selection" of behaviorally relevant information. However, it is still unclear in cognitive process of selection that the ACC can be activated by somatosensory stimuli as perceptually relevant information. To determine whether the ACC is activated by "early selection" of somatosensory stimuli surely without effects of motor acts as behavior, eighteen normal subjects performed elaborately designed tasks of selection while receiving somatosensory stimuli on their toes of the right and left feet under three different conditions using functional magnetic resonance imaging (fMRI) at 1.5 T. ACC activation was observed to be 2.1+/-0.3% (mean +/- SE) in selection and finger movement as motor acts, and 1.3+/-0.3% in selection and counting (without motor acts), whereas there was no activation in non-selection. The present fMRI study demonstrates that the ACC is activated by "early selection" following somatosensory stimuli surely without subsequent motor acts.