Part Of Anterior Cingulate Cortex Research Articles

Structural and functional changes of anterior cingulate cortex subregions in migraine without aura: relationships with pain sensation and pain emotion.

Migraine without aura is a multidimensional neurological disorder characterized by sensory, emotional, and cognitive symptoms linked to structural and functional abnormalities in the anterior cingulate cortex. Anterior cingulate cortex subregions play differential roles in the clinical symptoms of migraine without aura; however, the specific patterns and mechanisms remain unclear. In this study, voxel-based morphometry and seed-based functional connectivity were used to investigate structural and functional alterations in the anterior cingulate cortex subdivisions in 50 patients with migraine without aura and 50 matched healthy controls. Compared with healthy controls, patients exhibited (1) decreased gray matter volume in the subgenual anterior cingulate cortex, (2) increased functional connectivity between the bilateral subgenual anterior cingulate cortex and right middle frontal gyrus, and between the posterior part of anterior cingulate cortex and right middle frontal gyrus, orbital part, and (3) decreased functional connectivity between the anterior cingulate cortex and left anterior cingulate and paracingulate gyri. Notably, left subgenual anterior cingulate cortex was correlated with the duration of each attack, whereas the right subgenual anterior cingulate cortex was associated with migraine-specific quality-of-life questionnaire (emotion) and self-rating anxiety scale scores. Our findings provide new evidence supporting the hypothesis of abnormal anterior cingulate cortex subcircuitry, revealing structural and functional abnormalities in its subregions and emphasizing the potential involvement of the left subgenual anterior cingulate cortex-related pain sensation subcircuit and right subgenual anterior cingulate cortex -related pain emotion subcircuit in migraine.

Antinociceptive tolerance to NSAIDs in the anterior cingulate cortex is mediated via endogenous opioid mechanism

BackgroundIn the past decade several studies have reported that in some brain areas, particularly, in the midbrain periaqueductal gray matter, rostral ventro-medial medulla, central nucleus of amygdala, nucleus raphe magnus, and dorsal hippocampus, microinjections of non-steroidal anti-inflammatory drugs (NSAIDs) induce antinociception with distinct development of tolerance. Given this evidence, in this study we investigated the development of tolerance to the analgesic effects of NSAIDs diclofenac, ketorolac and xefocam microinjected into the rostral part of anterior cingulate cortex (ACC) in rats.MethodsMale Wistar experimental and control (saline) rats were implanted with a guide cannula in the ACC and tested for antinociception following microinjection of NSAIDs into the ACC in the tail-flick (TF) and hot plate (HP) tests. Repeated measures of analysis of variance with post-hoc Tukey-Kramer multiple comparison tests were used for statistical evaluations.ResultsTreatment with each NSAID significantly enhanced the TF and HP latencies on the first day, followed by a progressive decrease in the analgesic effect over a 4-day period, i.e., developed tolerance. Pretreatment with an opioid antagonist naloxone completely prevented the analgesic effects of the three NSAIDs in both behavioral assays.ConclusionsThese findings support the concept that the development of tolerance to the antinociceptive effects of NSAIDs is mediated via an endogenous opioid system possibly involving descending pain modulatory systems.

The neural correlates of visual imagery vividness – An fMRI study and literature review

Using the Vividness of Visual Imagery Questionnaire we selected 14 high-scoring and 15 low-scoring healthy participants from an initial sample of 111 undergraduates. The two groups were matched on measures of age, IQ, memory and mood but differed significantly in imagery vividness. We used fMRI to examine brain activation while participants looked at, or later imagined, famous faces and famous buildings. Group comparison revealed that the low-vividness group activated a more widespread set of brain regions while visualising than the high-vividness group. Parametric analysis of brain activation in relation to imagery vividness across the entire group of participants revealed distinct patterns of positive and negative correlation. In particular, several posterior cortical regions show a positive correlation with imagery vividness: regions of the fusiform gyrus, posterior cingulate and parahippocampal gyri (BAs 19, 29, 31 and 36) displayed exclusively positive correlations. By contrast several frontal regions including parts of anterior cingulate cortex (BA 24) and inferior frontal gyrus (BAs 44 and 47), as well as the insula (BA 13), auditory cortex (BA 41) and early visual cortices (BAs 17 and 18) displayed exclusively negative correlations. We discuss these results in relation to a previous, functional imaging study of a clinical case of ‘blind imagination’, and to the existing literature on the functional imaging correlates of imagery vividness and related phenomena in visual and other domains.

Neuroanatomical bases of effortful control: evidence from a large sample of young healthy adults using voxel-based morphometry.

Effortful control (EC) is a base of individuality in cognition and psychological adjustment. EC is defined as a capacity to control responses and behaviors. We investigated associations between individual differences of EC and regional gray and white matter volume (rGMV/rGMV) in 374 men and 306 women (age, 20.61 ± 1.82 years) using Japanese version of Effortful control scale (J-ECS). J-ECS consists of three subscales such as inhibitory control (IC), activation control (ACTC), and attentional control (ATC). Results showed that (a) IC was associated with larger rGMV in the dorsal part of anterior cingulate cortex (dACC), the supplementary motor area (SMA) and the pre SMA and larger rWMV in the dACC, (b) ACTC was correlated with smaller rGMV in the insula and the putamen, and (c) ATC was associated with larger rWMV in the inferior frontal gyrus, orbital frontal gyrus, ACC, and insula. Our study revealed key neuroanatomical correlations between EC and rGMV and rWMV.

Task and Resting-State fMRI Reveal Altered Salience Responses to Positive Stimuli in Patients with Major Depressive Disorder.

Altered brain function in patients with major depressive disorder (MDD) has been repeatedly demonstrated by task-based and resting-state studies, respectively. However, less is known concerning whether overlapped abnormalities in functional activities across modalities exist in MDD patients. To find out the answer, we implemented an fMRI experiment and collected both task and resting-state data from 19 MDD patients and 19 matched, healthy, controls. A distraction paradigm involving emotionally valenced pictures was applied to induce affective responses in subjects. As a result, concurrent deficits were found in arousing activation during a positive task in both the reward circuit and salience network (SN) that is composed of the dorsal part of anterior cingulate cortex (dACC) and bilateral anterior insulae (AI) in only the MDD group. Subsequent amplitude of low frequency fluctuations (ALFF) and functional connectivity analyses based on resting-state data exhibited consistent alterations in the bilateral AI of MDD patients, and indicated patients’ difficulties in regulating the balance between central executive network (CEN) and default mode network (DMN) due to altered connectivity among the CEN, DMN, and SN. Our findings provide new evidence demonstrating impaired salience processing and resulting alterations in responses to positive stimuli in MDD patients. Furthermore, brain abnormalities synchronized across functional states in MDD patients can be evidenced by a combination of task and resting-state fMRI analyses.

The Dorsal Anterior Cingulate Cortex Modulates Dialectical Self-Thinking.

Dialectical self-thinking involves holding the view that one can possess contradictory traits such as extraverted and introverted. Prior work has demonstrated that the dorsal part of anterior cingulate cortex (dACC) plays a crucial role in conflict monitoring as well as self-related processing. Here, we tested the function of dACC in dialectical self-thinking using a modified classical self-referential paradigm (self- vs. other-referential thinking), in which participants had to make a judgment whether a simultaneously presented pair of contradictory or non-contradictory traits properly described them while brain activity was recording using functional magnetic resonance imaging (fMRI). The data showed that activity in the dACC during the processing of self-relevant conflicting information was positively correlated with participants’ dispositional level of naïve dialecticism (measured with the Dialectical Self Scale). Psychophysiological interaction (PPI) analyses further revealed increased functional connectivity between the dACC and the caudate, middle temporal gyrus and hippocampus during the processing of self-relevant conflicting information for dialectical thinkers. These results support the hypothesis that the dACC has a key role in dialectical self-thinking.

Cytoarchitecture and neurocytology of rabbit cingulate cortex.

The rabbit cingulate cortex is highly differentiated in contrast to rodents and numerous recent advances suggest the rabbit area map needs revision. Immunohistochemistry was used to assess cytoarchitecture with neuron-specific nuclear binding protein (NeuN) and neurocytology with intermediate neurofilament proteins, parvalbumin and glutamic acid decarboxylase. Key findings include: (1) Anterior cingulate cortex (ACC) area 32 has dorsal and ventral divisions. (2) Area 33 is part of ACC. (3) Midcingulate cortex (MCC) has anterior and posterior divisions and this was verified with extensive quantitative analysis and a horizontal series of sections. (4) NeuN, also known as Fox-3, is not limited to somata and formed nodules, granular clusters and striations in the apical dendrites of pyramidal neurons. (5) Area 30 forms a complex of anterior and posterior parts with further medial and lateral divisions. (6) Area 29b has two divisions and occupies substantially more volume than in rat. (7) Area 29a begins with a subsplenial component and extends relatively further caudal than in rat. As similar areal designations are often used among species, direct comparisons were made of rabbit areas with those in rat and monkey. The dichotomy of MCC is of particular interest to studies of pain as anterior MCC is most frequently activated in human acute pain studies and the rabbit can be used to study this subregion. Finally, the area 30 complex is not primarily dysgranular as in rat and is more differentiated than in any other mammal including human. The large and highly differentiated rabbit cingulate cortex provides a unique model for assessing cingulate cortex, pain processing and RNA splicing functions.

Abnormal white matter connections between medial frontal regions predict symptoms in patients with first episode schizophrenia

IntroductionThe medial orbitofrontal cortex (mOFC) and rostral part of anterior cingulate cortex (rACC) have been suggested to be involved in the neural network of salience and emotional processing, and associated with specific clinical symptoms in schizophrenia. Considering the schizophrenia dysconnectivity hypothesis, the connectivity abnormalities between mOFC and rACC might be associated with clinical characteristics in first episode schizophrenia patients (FESZ). MethodsAfter parcellating mOFC into the anterior and posterior part, diffusion properties of the mOFC-rACC white matter connections for 21 patients with FESZ and 21 healthy controls (HCs) were examined using stochastic tractography, one of the most effective Diffusion Tensor Imaging (DTI) methods for examining tracts between adjacent gray matter (GM) regions. ResultsFractional anisotropy (FA) reductions were observed in bilateral posterior, but not anterior mOFC-rACC connections (left: p < .0001; right: p < .0001) in FESZ compared to HCs. In addition, reduced FA in the left posterior mOFC-rACC connection was associated with more severe anhedonia-asociality (rho = −.633, p = .006) and total score (rho = −.520, p = .032) in the Scale for the Assessment of Negative Symptoms (SANS); reduced FA in the right posterior mOFC-rACC connection was associated with more severe affective flattening (rho = −.644, p = .005), total score (rho = −.535, p = .027) in SANS, hallucinations (rho = −.551, p = .018), delusions (rho = −.632, p = .005) and total score (rho = −.721, p = .001) in the Scale for the Assessment of Positive Symptoms (SAPS) in FESZ. ConclusionsThe observed white matter abnormalities within the connections between mOFC and rACC might be associated with the psychopathology of the early stage of schizophrenia.

Tai Chi and its anti-inflammatory effect on the peripheral blood leukocytes

Purpose: From the perspective of neuroscience, acupuncture-induced sensation is not only coming from the bottom-up modulation of ‘simple needling’ in the somatosensory receptor, but also from the reciprocal interaction with the topdown modulation of the brain. Enhanced body schema triggered by acupuncture stimulation can influence the homeostatic control system through a modulated salience network of the brain. We investigated commonalities and differences in brain responses to enhanced bodily attention around the acupuncture points with or without actual stimulation. Methods: Fourteen participants received acupuncture needles at both PC6 (median nerve) and HT7 (ulnar nerve) acupoints in the left hand. To enhance bodily attention to acupoints, participants were required to respond to the locations of stimulations at PC6 or HT7 in a two alternative-forced choice task. Two fMRI scans were taken in a block design: session 1 labeled withmanual stimulation (actual stimulation with randomized acupoint stimulation) and session 2 labeled with electro-acupuncture (no physical stimulation; pseudostimulation). To compare cortical activation patterns, data were analyzed using the freesurfer software. Results: In the conjunction analysis, both actual and pseudo-stimulation produced brain activations in the insula, anterior cingulate cortex, secondary somatosensory cortex, superior parietal cortex, and brain deactivations in themedial prefrontal cortex, posterior cingulate cortex, inferior parietal cortex, and the parahippocampus. In the contrast analysis, actual stimulation exhibited greater brain activations inposterior insula, posterior operculumand the caudal part of anterior cingulate cortex, compared to pseudo-stimulation. Conclusion:We demonstrated that enhanced bodily attention triggered by acupuncture stimulation is able to activate the salience network and deactivate the default mode network regardless of actual stimulation. Our findings suggest that the component of enhanced attention to a certain part of the body plays an important role in the brain responses to acupuncture stimulation. Contact: Younbyoung Chae, ybchae@khu.ac.kr

Is social categorization based on relational ingroup/outgroup opposition? A meta-analysis

Social categorization is known to be an important part of social cognition. The categorizations we use, despite their multitude, frequently take the form of the general ingroup/outgroup distinction. A meta-analysis of 33 fMRI studies, reporting selective activations to various social groups, was used to identify common neural structures responsible for relational representation of social structure. Activation Likelihood Estimation (ALE) analysis revealed areas in bilateral amygdala, cingulate gyrus, fusiform gyrus, right TPJ and right insula as implementing various aspects of social categorization. Activation of amygdala can be associated with modulation of behavioral response to subjectively significant stimuli. A more ventral part of anterior cingulate cortex (ACC) can be associated with self-referential reasoning about ingroup members while a more dorsal part of ACC is involved in the regulation of emotions toward outgroup members. Right insula can be engaged in the modulation of outgroup avoidance behavior. Fusiform gyrus (FG) appears to be directly involved in social categorization process via top-down modulation of social perception. Yet it is difficult to associate any of the revealed clusters with the relational ingroup/outgroup structure.

Pain processing in patients with migraine: an event-related fMRI study during trigeminal nociceptive stimulation

We explored the functional pattern of the pain-processing network in patients with migraine, in the interictal periods, during trigeminal noxious stimulation. Contact heat evoked potential stimulation induced thermal pain and functional magnetic resonance imaging were used to measure whole-brain activation in 16 patients with episodic migraine without aura and 16 age- and gender-matched healthy controls in response to a severe (53°C) noxious, a moderate (51°C) noxious, and a control (41°C) stimulus applied to the maxillary skin. When comparing the fMRI activation over the entire brain, patients with migraine, with respect to healthy controls, showed a significantly greater activation in the perigenual part of anterior cingulate cortex at 51°C and less activation in the bilateral secondary somatosensory cortex at 53°C. A group-by-stimulus interaction analysis revealed a region in the pons showing a divergent response in patients and healthy controls. Correlation analyses demonstrated that the pons activation correlated with higher headache-related disability in patients. Our findings demonstrate increased antinociceptive activity in patients with migraine, which may represent a compensatory reorganization to modulate pain perception at the same intensity of healthy controls.

Interictal cortical reorganization in episodic migraine without aura: an event-related fMRI study during parametric trigeminal nociceptive stimulation

The aim of our study was to explore the pain processing network in patients with migraine during trigeminal nociceptive stimulation. Sixteen patients with episodic migraine without aura and 16 healthy controls performed functional magnetic resonance imaging during thermal stimuli (at 41, 51 and 53°C). Patients with migraine showed a greater activation in the perigenual part of anterior cingulate cortex at 51°C and less activation in the bilateral somatosensory cortex at 53°C compared to healthy controls. There were no differences in experimental pain perception between groups. Our findings demonstrate a functional reorganization of cerebral areas known to be involved in pain processing in patients with migraine.

Impaired Error Monitoring and Correction Function in Autism

INTRODUCTION: Error monitoring and correction is one of the executive functions and is important for effective goal directed behavior. Deficient executive functioning, including reduced error monitoring ability, is one of the typical features of such neurodevelopmental disorders as autism, probably related to perseverative responding, stereotyped repetitive behaviors, and an inability to accurately monitor ongoing behavior. Our prior studies of behavioral and event-related potential (ERP) measures during performance on visual oddball tasks in high-functioning autistic (HFA) children showed that despite only minor differences in reaction times HFA children committed significantly more errors. METHODS: This study investigated error monitoring in children with autism spectrum disorder (ASD) with response-locked event-related potentials - the Error-related Negativity (ERN) and Error-related Positivity (Pe) recorded at fronto-central sites. The ERN reflects early error detection processes, while the Pe has been associated with later conscious error evaluation and attention re-allocation. Reaction times (RT) in correct trials and post-error slowing in reaction times were measured. In this study fourteen subjects with ASD and 14 age- and IQ- matched controls received a three-category visual oddball task with novel distracters. RESULTS: ERN had a lower amplitude and longer latency in the ASD group but was localized in the caudal part of anterior cingulate cortex (ACC) in both groups. The Pe component was significantly prolonged in the ASD group but did not reach significance in amplitude differences compared to controls. We found significant post-error slowing in RTs in controls, and post-error acceleration in RTs in the ASD group. CONCLUSIONS: The reduced ERN and altered Pe along with a lack of post-error RT slowing in autism might be interpreted as insensitivity in the detection and monitoring of response errors and a reduced ability of execute corrective actions. This might result in reduced error awareness and failure in adjustment when dealing with situations where erroneous responses may occur. This deficit might be manifested in the perseverative behaviors often seen in individuals with ASD. The results are discussed in terms of a general impairment in self-monitoring and other executive functions underlying behavioral and social disturbances in ASD.

Abnormalities of the contingent negative variation in Huntington's disease: Correlations with clinical features

The contingent negative variation (CNV) is a neurophysiological pattern related to planning of external — paced, voluntary movements. The aim of the study, was to examine the CNV in a cohort of mild demented and non-medicated HD patients, evaluating the CNV amplitude modifications in the light of clinical features and performing Low Resolution Brain Electromagnetic Tomography (LORETA) analysis in order to show the CNV multiple generators. Fourteen HD patients and 25 sex and age-matched controls were studied. All subjects were evaluated by the motor section of UHDRS, MMSE and WAIS. The CNV was recorded by 19 scalp electrodes, with a red light flash as visual warning stimulus (S1), followed by a blue light flash (S2) after a fixed interval of 3 s. The amplitude of early CNV was significantly reduced in HD, compared to controls: the amplitude reduction was significantly correlated with the bradikinesia score. LORETA analysis of early CNV significantly discriminated patients from controls, for a prevalent activation of the posterior part of anterior cingulate cortex in HD. An abnormal activation of the associative cortex devoted to the processing of attention preceding voluntary movement may be supposed in HD, probably mediated by the altered basal ganglia modulation.

Intrinsic connections of the cingulate cortex in the rat suggest the existence of multiple functionally segregated networks

The cingulate cortex is a functionally and morphologically heterogeneous cortical area comprising a number of interconnected subregions. To date, the exact anatomy of intracingulate connections has not been studied in detail. In the present study we aimed to determine the topographical and laminar characteristics of intrinsic cingulate connections in the rat, using the anterograde tracers Phaseolus vulgaris-leucoagglutinin and biotinylated dextran amine. For assessment of these data we further refined and compared the existing cytoarchitectonic descriptions of the two major cingulate constituents, the anterior cingulate and retrosplenial cortices. The results of this study demonstrate that rostral areas, i.e. the infralimbic and prelimbic cortices and the rostral one third of the dorsal anterior cingulate cortex are primarily interconnected with each other and not with other cingulate areas. The caudal two thirds of the dorsal anterior cingulate cortex project to the caudal part of the ventral anterior cingulate cortex, whereas the entire ventral anterior cingulate cortex projects to only the mid-rostro-caudal part of the dorsal anterior cingulate cortex. Dense reciprocal connections exist between the remaining, i.e. the supracallosal parts of the anterior cingulate and retrosplenial cortices with a general rostro-caudal topography, in the sense that the rostral part of the anterior cingulate cortex and caudal part of the retrosplenial cortex are interconnected and the same holds true for the caudal part of the anterior cingulate cortex and rostral part of the retrosplenial cortex. This topographical pattern of intracingulate connections relates to the results of several functional studies, suggesting that specific cingulate functions depend on a number of interconnected cingulate subregions. Through their intricate associational connections, these subregions form functionally segregated networks.

Passive perception of odors and semantic circuits.

The sense of smell has been traditionally assumed to be different from other sensory modalities in that odors are encoded perceptually, without a semantic component. Recent findings of improved odor memory upon encoding with verbal cues question this view. Furthermore, familiar odors are easier to remember and discriminate than are unfamiliar ones, and odor familiarity is reported to predict odor naming. To investigate whether familiar odors are processed by different cerebral structures than those that process unfamiliar odors, (15)O H(2)O-positron emission tomography (PET) measurements of cerebral blood flow were carried out in 14 healthy men. The task was passive, birhinal, smelling of familiar odors (FAM), unfamiliar odors (uFAM), and odorless air (AIR). Significant activations (P < 0.05) were calculated using the contrasts FAM-AIR, uFAM-AIR, and FAM-uFAM, and deactivations running these contrasts in the opposite direction. In relation to AIR, both FAM and uFAM activated amygdala, piriform cortex, and parts of anterior cingulate cortex. FAM activated, in addition, left frontal cortex (Brodmann's areas 44,45,47), left parietal cortex incorporating precuneus, and right parahippocampus. Clusters covering parahippocampus and precuneus were observed also in FAM-uFAM. The activation of left frontal cortex and right parahippocampus was positively correlated with familiarity ratings. Smelling of familiar but not unfamiliar odorants seems to engage cerebral circuits mediating memory and language functions, in addition to the engagement of olfactory cortex. Already the most elemental form of odor processing, passive perception thus seems to engage semantic circuits. This is achieved by the ability of odorants to immediately elicit associations and judgments of odor characteristics.

Analgesia by electrostimulation of the trigeminal ganglion in patients with trigeminopathic pain: a PET activation study

Electrostimulation of the trigeminal ganglion (TGES) has shown good results in treatment of trigeminopathic pain in selected patients. To map the mechanisms of TGES analgesia, we determined changes in relative regional cerebral blood flow (rCBF) in ten patients with trigeminopathic pain using positron emission tomography. The patients were scanned before stimulation (habitual pain), after short-term stimulation (1 min, stTGES) and after long-term stimulation (ltTGES). Highly significant pain alleviation was reported after ltTGES. Relative rCBF changes after stTGES, which was without significant pain relief, were attributed mainly to intrinsic TGES effects. A statistical comparison of the subtraction images of ltTGES and stTGES disclosed significant rCBF increases after ltTGES in rostral parts of anterior cingulate cortex (ACC) and neighboring orbitofrontal and medial frontal cortices. Regression analysis of rCBF changes and subjective ratings of pain revealed an inverse relationship in the ipsilateral rostral ACC, and only rCBF changes in the caudal part of the contralateral ACC were consistent with the encoding of pain. The present study provides evidence for a pain modulating role of the rostral ACC, critically important in electrostimulation-induced analgesia, and identifies the caudal ACC as a region encoding pain sensation.

Anterior cingulate cortex pathology in schizophrenia and bipolar disorder.

To explore possible morphological abnormalities in the dorsal and subgenual parts of anterior cingulate cortex in mood disorders and schizophrenia, we performed a quantitative postmortem study of 44 schizophrenic patients, 21 patients with sporadic bipolar disorder, 20 patients with sporadic major depression, and 55 age- and sex-matched control cases. All individuals were drug naïve or had received psychotropic medication for less than 6 months, and had no history of substance abuse. Neuron densities and size were estimated on cresyl violet-stained sections using a stereological counting approach. The distribution and density of microtubule-associated (MAP2, MAP1b) and tau proteins were assessed by immunocytochemistry and quantitative immunodot assay. Mean total and laminar cortical thicknesses as well as mean pyramidal neuron size were significantly decreased in the dorsal and subgenual parts of areas 24 (24sg) in schizophrenic cases. Patients with bipolar disorder showed a substantial decrease in laminar thickness and neuron densities in layers III, V, and VI of the subgenual part of area 24, whereas patients with major depression were comparable to controls. Immunodot assay showed a significant decrease of both MAP2 and MAP1b proteins in bipolar patients but not in patients with schizophrenia and major depression. The neuroanatomical and functional significance of these findings are discussed in the light of current hypotheses regarding the role of areas 24 and 24sg in schizophrenia and bipolar disorder.

PET evaluation of bilingual language compensation following early childhood brain damage

We report a positron emission tomography (PET) study in a 37-year-old, right handed, bilingual (English and American Sign Language) male with left frontal lobe damage, without evidence of language or general intellectual dysfunction. A brain MRI scan demonstrated an atrophic lesion of the left dorsolateral prefrontal, orbital, and opercular cortices extending from the frontal pole to precentral gyrus and including parts of anterior cingulate cortex, due to an probable infantile encephalitis. H 2 15O PET scans found evidence of increased right hemisphere activity compared to normal controls during spontaneous generation of narrative in both English and ASL. Neuropsychological data were within normal limits with the exception of visuospatial function. The results suggest the possibility that plasticity, unmasking of neural pathways, and or other adaptations of language function in the right hemisphere may have occurred, and are discussed with regard to the crowding hypothesis.

Contributions of anterior cingulate cortex to behaviour.

Assessments of anterior cingulate cortex in experimental animals and humans have led to unifying theories of its structural organization and contributions to mammalian behaviour. The anterior cingulate cortex forms a large region around the rostrum of the corpus callosum that is termed the anterior executive region. This region has numerous projections into motor systems, however, since these projections originate from different parts of anterior cingulate cortex and because functional studies have shown that it does not have a uniform contribution to brain functions, the anterior executive region is further subdivided into 'affect' and 'cognition' components. The affect division includes areas 25, 33 and rostral area 24, and has extensive connections with the amygdala and periaqueductal grey, and parts of it project to autonomic brainstem motor nuclei. In addition to regulating autonomic and endocrine functions, it is involved in conditioned emotional learning, vocalizations associated with expressing internal states, assessments of motivational content and assigning emotional valence to internal and external stimuli, and maternal-infant interactions. The cognition division includes caudal areas 24' and 32', the cingulate motor areas in the cingulate sulcus and nociceptive cortex. The cingulate motor areas project to the spinal cord and red nucleus and have premotor functions, while the nociceptive area is engaged in both response selection and cognitively demanding information processing. The cingulate epilepsy syndrome provides important support of experimental animal and human functional imaging studies for the role of anterior cingulate cortex in movement, affect and social behaviours. Excessive cingulate activity in cases with seizures confirmed in anterior cingulate cortex with subdural electrode recordings, can impair consciousness, alter affective state and expression, and influence skeletomotor and autonomic activity. Interictally, patients with anterior cingulate cortex epilepsy often display psychopathic or sociopathic behaviours. In other clinical examples of elevated anterior cingulate cortex activity it may contribute to tics, obsessive-compulsive behaviours, and aberrent social behaviour. Conversely, reduced cingulate activity following infarcts or surgery can contribute to behavioural disorders including akinetic mutism, diminished self-awareness and depression, motor neglect and impaired motor initiation, reduced responses to pain, and aberrent social behaviour. The role of anterior cingulate cortex in pain responsiveness is suggested by cingulumotomy results and functional imaging studies during noxious somatic stimulation. The affect division of anterior cingulate cortex modulates autonomic activity and internal emotional responses, while the cognition division is engaged in response selection associated with skeletomotor activity and responses to noxious stimuli. Overall, anterior cingulate cortex appears to play a crucial role in initiation, motivation, and goal-directed behaviours.(ABSTRACT TRUNCATED AT 400 WORDS)