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Query: UNIPROT:Q16637 (SMA)
 8,107 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alternating between task sets involves detection that the current task set is unfavorable, initiation of a change in set, and application of the new task set while fine-tuning to optimally adjust to the demands of the environment. Functional magnetic resonance imaging (fMRI) studies of cognitive flexibility consistently report activation of the anterior cingulate cortex and/or adjacent pre-supplementary motor regions (ACC/pre-SMA, medial Brodmann's areas 24/32/6), suggesting that these cortical regions are involved in switching task set. In the current study, our objective was to probe whether ACC/pre-SMA activation would decrease for a number of trials following a switch in task set, implying longer-term involvement in fine-tuning adjustments. By measuring activation when switching between word reading and color naming in response to Stroop stimuli, ACC/pre-SMA activation was observed when actively countering the influence of the irrelevant task set, and this activation decreased as a function of the number of trials since a task switch. Basal ganglia and thalamic regions also displayed a decreased response over successive trials after task switches. These findings suggest that the ACC/pre-SMA are not only involved in generating a new course of action, but are also involved (along with subcortical regions) in fine-tuning operations that resolve competition between task sets over subsequent repetitions of the same task.
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PMID:Short- and long-term changes in anterior cingulate activation during resolution of task-set competition. 1637 61

Cognitive impairments have been found in thyroid hormone-related diseases (e.g. hyperthyroidism and hypothyroidism) for a long time. However, whether and how subclinical hypothyroidism (SCH) causes any deficits in brain functions, and whether a hormone-replacement treatment is necessary for SCH patients, still remain controversial subjects. In the present study, functional MRI (fMRI) was used to measure brain functions by asking euthyroid subjects, hyperthyroid patients and SCH patients to perform the widely used digit n-back working memory task. After having been treated with l-thyroxine for approximately 6 months, the SCH patients were asked to do the same fMRI experiment. The hypothyroid and SCH patients scored significantly lower in the 2-back task than either the hyperthyroid patients or the euthyroid subjects (P < 0.012). The fMRI showed that a common frontoparietal network, including bilateral middle/inferior frontal gyri (M/IFG), bilateral dorsolateral prefrontal cortex (DLPFC), bilateral premotor areas (PreMA), the supplementary motor area/anterior cingulate cortex (SMA/ACC) and bilateral parietal areas (PA), was activated by the n-back task in all the subjects. Further quantitative analysis showed that the load effect of blood oxygen level-dependent (BOLD) response appeared in all the five regions of interest (ROIs) in the euthyroid and hyperthyroid subjects. In the pre-treatment SCH patients, however, the load effect of BOLD response was only found in the PA and PreMA, but not in other frontal cortex ROIs [general linear model (GLM), F < 2.6, P > 0.1]. After an approximately 6 month treatment with LT4, the SCH patients exhibited the same load effects in all five ROIs as the euthyroid subjects (GLM, F > 6, P < 0.05) along with an improvement of performance in n-back task. These results suggest that working memory (but not other memory functions) is impaired in SCH patients, mainly as far as disorders of the frontoparietal network were concerned. Both the memory performance and frontal executive functions were improved after an l-thyroxine-replacement treatment.
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PMID:fMRI revealed neural substrate for reversible working memory dysfunction in subclinical hypothyroidism. 1692 Nov 78

In the human brain, a well known frontoparietal circuit, including lateral prefrontal cortex (LPFC), presupplementary motor area/anterior cingulate cortex (pre-SMA/ACC), and both the superior and inferior parietal cortex, is involved in cognitive control. One proposal is that the frontoparietal cortex holds a flexible description of attended or task-relevant information, biasing processing in favor of this information in many different parts of the brain. Here, we separate frontoparietal coding of attended information from its active use in behavior. In two experiments, subjects watch a stream of visual stimuli in a fixed location. In the first experiment, there is no task to perform; in the second, decisions are orthogonal to the occurrence of new stimulus events. Even in these simple circumstances, we find that attended stimulus changes give extensive activation of LPFC, pre-SMA/ACC and parietal cortex, whereas unattended changes do not. Even without behavior to control, these classical "control" regions are active in simple update of attended information.
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PMID:Frontoparietal activity with minimal decision and control. 1698 51

Together with a detailed behavioral analysis, simultaneous measurement of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) permits a better elucidation of cortical pain processing. We applied painful electrical stimulation to 6 healthy subjects and acquired fMRI simultaneously with an EEG measurement. The subjects rated various stimulus properties and the individual affective state. Stimulus-correlated BOLD effects were found in the primary and secondary somatosensory areas (SI and SII), the operculum, the insula, the supplementary motor area (SMA proper), the cerebellum, and posterior parts of the anterior cingulate gyrus (ACC). Perceived pain intensity was positively correlated with activation in these areas. Higher unpleasantness rating was associated with suppression of activity in areas known to be involved in stimulus categorization and representation (ventral premotor cortex, PCC, parietal operculum, insula) and enhanced activation in areas initiating, propagating, and executing motor reactions (ACC, SMA proper, cerebellum, primary motor cortex). Concordant dipole localizations in SI and ACC were modeled. Using the dipole strength in SI, the network was restricted to SI. The BOLD signal change in ACC was positively correlated to the individual dipole strength of the source in ACC thus revealing a close relationship of BOLD signal and possibly underlying neuronal electrical activity in SI and the ACC. The BOLD signal change decreased in SI over time. Dipole strength of the ACC source decreased over the experiment and increased during the stimulation block suggesting sensitization and habituation effects in these areas.
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PMID:A simultaneous EEG-fMRI study of painful electric stimulation. 1717 35

Attentional control involves the ability to allocate preparatory attention to improve subsequent stimulus processing and response selection. There is behavioral evidence to support the hypothesis that increased expectancy of stimulus and response conflict may decrease the subsequent experience of conflict during task performance. We used a cued flanker and event-related fMRI design to separate processes involved in preparation from those involved in resolving conflict and to identify the brain systems involved in these processes as well as the association between preparatory activity levels and activity related to subsequent conflict processing. Our results demonstrate that preparatory attentional allocation following a cue to the upcoming level of conflict is mediated by a network involving Dorsolateral Prefrontal Cortex (DLPFC) and the Intraparietal Sulcus (IPS). Informed preparation for conflict processing was associated with decreased Anterior Cingulate Cortex/pre-Supplementary Motor Area (ACC/pre-SMA) and IPS activity during the flanker target presentation, supporting their roles in conflict processing and visuospatial attention during the flanker task. Ventrolateral Prefrontal Cortex/Orbitofrontal Cortex (VLPFC/OFC) was active when specific strategic task rule and outcome information was available.
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PMID:Preparatory allocation of attention and adjustments in conflict processing. 1725 12

Mutational analyses in xenopus oocyte and mice models indicate that the positive effect of nicotine on attention may be modulated by genetic variations within exon 5 of the alpha4 subunit of the nicotinergic acetylcholine receptor gene CHRNA4. The potential relevance of exon 5 is further emphasized by two recent family-based association studies of nicotine dependence because subgroups of nicotine-dependent subjects are thought to 'self-medicate' attentional deficits with nicotine. We investigated a synonymous single nucleotide polymorphisms (SNP): rs1044396, which has recently been associated with nicotine-dependence, plus two adjacent synonymous SNPs rs1044394 and rs1044393 in exon 5 of n = 47 unrelated healthy Caucasian subjects (age: 22.7 +/- 1.7 years; sex: n = 23 males; regular smokers: n = 19). Attentional network function was assessed in supplementary motor area/anterior cingulate (SMA/ACC) and parietal cortex with functional magnetic resonance imaging during an attention-requiring visual oddball task. SNP rs1044396 showed genotype effects on attentional network function both in the SMA/ACC and parietal cortex in the absence of overt behavioral effects. In the parietal cortex, a gene-dosage effect was seen. Comparable genotype effects were also found for the other two SNPs. This investigation provides first evidence that attentional network function may be modulated by genetic variations within CHRNA4 exon 5. If confirmed, future studies need to address what 'functional' polymorphisms are causative for the observed effects.
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PMID:Association of attentional network function with exon 5 variations of the CHRNA4 gene. 1761 39

Fluid intelligence (g(f)) influences performance across many cognitive domains. It is affected by both genetic and environmental factors. Tasks tapping g(f) activate a network of brain regions including the lateral prefrontal cortex (LPFC), the presupplementary motor area/anterior cingulate cortex (pre-SMA/ACC), and the intraparietal sulcus (IPS). In line with the "intermediate phenotype" approach, we assessed effects of a polymorphism (val(158)met) in the catechol-O-methyltransferase (COMT) gene on activity within this network and on actual task performance during spatial and verbal g(f) tasks. COMT regulates catecholaminergic signaling in prefrontal cortex. The val(158) allele is associated with higher COMT activity than the met(158) allele. Twenty-two volunteers genotyped for the COMT val(158)met polymorphism completed high and low g(f) versions of spatial and verbal problem-solving tasks. Our results showed a positive effect of COMT val allele load upon the blood oxygen level-dependent response in LPFC, pre-SMA/ACC, and IPS during high g(f) versus low g(f) task performance in both spatial and verbal domains. These results indicate an influence of the COMT val(158)met polymorphism upon the neural circuitry supporting g(f). The behavioral effects of val allele load differed inside and outside the scanner, consistent with contextual modulation of the relation between COMT val(158)met genotype and g(f) task performance.
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PMID:COMT val158met genotype affects recruitment of neural mechanisms supporting fluid intelligence. 1825 43

Recent functional neuroimaging studies have examined cognitive inhibitory control, decision-making and stress regulation in heroin addiction using a cue-reactivity paradigm. Few studies have considered impairments in heroin users from an integrated perspective for evaluation of their brain functions. We hypothesized that the brain regions that are dysregulated in the chronic heroin users during cue-reactivity studies may also show dysfunctional connectivity in memory, inhibition and motivation-related dysfunctions during a resting state free of cues. The present study used resting functional magnetic resonance imaging (fMRI) to compare the interaction of brain regions between 12 chronic heroin users and 12 controls by employing a novel graph theory analysis (GTA) method. As a data-driven approach, GTA has the advantage of evaluating the strength as well as the temporal and spatial patterns of interactions among the brain regions. Abnormal topological properties were explored in the brain of chronic heroin users, such as the dysfunctional connectivity in the prefrontal cortex, ACC, SMA, ventral striatum, insula, amygdala and hippocampus. Our results suggest that GTA is a useful tool in defining dysregulated neural networks even during rest. This dysfunctional brain connectivity may contribute to decrease self-control, impaired inhibitory function as well deficits in stress regulation in chronic heroin users.
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PMID:Dysfunctional connectivity patterns in chronic heroin users: an fMRI study. 1945 Jun 64

The aim of the present paper is to assess the effects of altered dopamine (DA) transmission on the functional connectivity among brain regions mediating aversive conditioning in humans. To this aim, we analyzed a previous published data set from a double-blind design combined with functional magnetic resonance imaging (fMRI) recordings in which healthy volunteers were randomly assigned to one of three drug groups: amphetamine (an indirect DA agonist), haloperidol (DA D2 receptor antagonist), and placebo. Participants were exposed to an aversive classical conditioning paradigm using cutaneous electrical stimulation as the unconditioned stimulus (US), and visual cues as the conditioned stimuli (CS) where one colour (CS+) was followed by the US in 33% of the trials and another colour (CS-) had no consequences. All participants reported awareness of stimulus contingencies. Group analysis of fMRI data revealed that the left ventral striatum (VS) and amygdala activated in response to the CS+ in all the three groups. Because of their activation patterns and documented involvement in aversive conditioning, both regions were used as seeds in the functional connectivity analysis. To constrain the functional networks obtained to relate to the conditioned response, we also correlated seed activity with the Galvanic Skin Response (GSR). In the placebo group, the right ventral tegmental area/substantia nigra (VTA/SN), bilateral caudate, right parahippocampal gyrus, left inferior parietal lobule (IPL), bilateral postcentral gyrus, bilateral middle frontal (BA 46), orbitofrontal, and ventromedial prefrontal cortices (PFC, BA 10/11) correlated with the VS and amygdala seeds in response to the CS+ compared to the CS-. Enhancing dopamine transmission via amphetamine was associated with reduced task differences and significant functional connectivity for both CS+ and CS- conditions between the left VS seed and regions modulated by DA, such as the left VTA/SN, right caudate, left amygdala, left middle frontal gyrus (BA 46), and bilateral ventromedial PFC (BA 10). Blocking dopamine transmission via haloperidol was associated with significant functional connectivity across an alternate network of regions including the left amygdala seed and the right insula, the left ACC (BA 24/32), bilateral IPL (BA 40), precuneus (BA 7), post-central gyrus, middle frontal gyrus (BA 46), and supplementary motor area (SMA, BA 6) to the CS+ versus the CS-. These data provide insight into the distinct effects of DA agents on the functional connectivity between striatal, limbic, and prefrontal areas.
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PMID:Dopamine-induced changes in neural network patterns supporting aversive conditioning. 1996 36

The goal of the present study was to investigate the neuroanatomical basis of arithmetic fact retrieval. The rationale was that areas playing a crucial role in arithmetic fact retrieval should show a systematic increase of activation with increasing retrieval effort. To achieve this goal, we utilized the problem-size effect as this is known to be systematically related to retrieval effort. In contrast to many previous studies, we here took a parametric approach to account for the continuous increase of retrieval effort with problem size. BOLD signals were modeled with problem size as parametric regressor and negative slow waves of the EEG were categorized into six levels of problem size. The fMRI data showed that activation in the angular gyrus and ACC/SMA increased parametrically with problem size. The ERP data showed a systematic amplitude increase with increasing problem size, especially at fronto-central electrodes. Consistent with the fMRI data, source modeling localized this effect to the ACC. While these findings support previous notions about the crucial role of the angular gyrus during fact retrieval, they also provide evidence that the medial frontal cortex is involved when single-digit multiplications are solved. Thus, both parietal and frontal structures seem to be integral parts of a system that enables and controls arithmetic fact retrieval.
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PMID:Frontal and parietal contributions to arithmetic fact retrieval: a parametric analysis of the problem-size effect. 2033 90


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