scholarly journals Contribution of Exploratory Methods to the Investigation of Extended Large-Scale Brain Networks in Functional MRI: Methodologies, Results, and Challenges

2008 ◽  
Vol 2008 ◽  
pp. 1-14 ◽  
Author(s):  
V. Perlbarg ◽  
G. Marrelec

A large-scale brain network can be defined as a set of segregated and integrated regions, that is, distant regions that share strong anatomical connections and functional interactions. Data-driven investigation of such networks has recently received a great deal of attention in blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI). We here review the rationale for such an investigation, the methods used, the results obtained, and also discuss some issues that have to be faced for an efficient exploration.

2016 ◽  
Vol 36 (12) ◽  
pp. 2177-2193 ◽  
Author(s):  
Cornelia Helbing ◽  
Marta Brocka ◽  
Thomas Scherf ◽  
Michael T Lippert ◽  
Frank Angenstein

Several human functional magnetic resonance imaging studies point to an activation of the mesolimbic dopamine system during reward, addiction and learning. We previously found activation of the mesolimbic system in response to continuous but not to discontinuous perforant pathway stimulation in an experimental model that we now used to investigate the role of dopamine release for the formation of functional magnetic resonance imaging responses. The two stimulation protocols elicited blood-oxygen-level dependent responses in the medial prefrontal/anterior cingulate cortex and nucleus accumbens. Inhibition of dopamine D1/5 receptors abolished the formation of functional magnetic resonance imaging responses in the medial prefrontal/anterior cingulate cortex during continuous but not during discontinuous pulse stimulations, i.e. only when the mesolimbic system was activated. Direct electrical or optogenetic stimulation of the ventral tegmental area caused strong dopamine release but only electrical stimulation triggered significant blood-oxygen level-dependent responses in the medial prefrontal/anterior cingulate cortex and nucleus accumbens. These functional magnetic resonance imaging responses were not affected by the D1/5 receptor antagonist SCH23390 but reduced by the N-methyl-D-aspartate receptor antagonist MK801. Therefore, glutamatergic ventral tegmental area neurons are already sufficient to trigger blood-oxygen-level dependent responses in the medial prefrontal/anterior cingulate cortex and nucleus accumbens. Although dopamine release alone does not affect blood-oxygen-level dependent responses it can act as a switch, permitting the formation of blood-oxygen-level dependent responses.


2019 ◽  
Vol 3 ◽  
pp. 247054701984864 ◽  
Author(s):  
Khalil Thompson ◽  
Kendrick King ◽  
Eddy Nahmias ◽  
Negar Fani ◽  
Trevor Kvaran ◽  
...  

Background Social anxiety is characterized by a tendency to overestimate the likelihood of negative outcomes and consequences before, during, and after interpersonal interactions with social partners. Recent evidence suggests that a network of brain regions critical for perspective-taking, threat appraisal, and uncertainty resolution may function atypically in those prone to social anxiety. In this study, we used functional magnetic resonance imaging to examine neural activity in specific regions of interest in a sample of young adults who endorsed high or low levels of social anxiety. Methods We recruited 31 college student volunteers (age: 18–28 years), categorized as having high or low anxiety based on their Liebowitz Social Anxiety Scale-Self Report scores. These participants were each scanned while playing the iterated Prisoner’s Dilemma game with three computerized confederates, two of whom they were deceived to believe were human co-players. This study focuses on data collected during play with the presumed humans. Regions of interest were defined for the temporoparietal junction, anterior midcingulate, and dorsomedial prefrontal cortex. Average weighted mean blood-oxygen-level-dependent signals for each subject were extracted and analyzed using mixed design analyses of variance to detect group differences in activation during decision-making, anticipation, and appraisal of round outcomes during the game. Results Behavior analysis revealed that the high-anxiety group was more likely to defect than the low-anxiety group. Neuroimaging analysis showed that the high-anxiety group exhibited elevated blood-oxygen-level-dependent activity relative to the low-anxiety group in all three regions during the social feedback appraisal phase but not during decision-making or the anticipation of interaction outcomes. Conclusions These findings provide evidence that some behaviors linked to cognitive biases associated with social anxiety may be mediated by a network of regions involved in recognizing and processing directed social information. Future investigation of the neural basis of cognition and bias in social anxiety using the prisoner’s dilemma and other economic-exchange tasks is warranted. These tasks appear to be highly effective, functional magnetic resonance imaging-compatible methods of probing altered cognition and behavior associated with anxiety and related conditions.


Neurosurgery ◽  
2004 ◽  
Vol 54 (4) ◽  
pp. 902-915 ◽  
Author(s):  
Asta Håberg ◽  
Kjell Arne Kvistad ◽  
Geirmund Unsgård ◽  
Olav Haraldseth

Abstract OBJECTIVE This study sought to evaluate the ability of blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to successfully identify functional cortical areas in patients with primary brain tumors, to evaluate the use of the fMRI results in presurgical planning, and to assess the functional outcome of the patients with respect to the functional maps obtained with fMRI. METHODS The study included 25 consecutive preoperative fMRI sessions in patients with primary brain tumors in or near sensorimotor and/or language cortices. All fMRI paradigms were analyzed and rated according to the degree of success. Several distances between tumor and functional cortex as delineated with BOLD fMRI were measured to assess the topographic relationship between these two structures. Pre- and postoperative neurological statuses were obtained from the patients' journals. RESULTS Acquisition of BOLD fMRI images was successful in 80% of the cases. The primary cause of unsuccessful fMRI was echo-planar imaging signal voids that were the result of previous craniotomy; the secondary cause was excessive motion. The neurosurgeons used the fMRI results for preoperative planning in 75% of the cases in which fMRI was successful. The risk of postoperative loss of function tested with fMRI was significantly lower when the distance between tumor periphery and BOLD activity was 10 mm or more. CONCLUSION The majority of patients with primary brain tumors were capable of satisfactorily performing the fMRI paradigms, and the information obtained was used in the preoperative planning. A distance of 10 mm or more between the functional cortex, as delineated with fMRI, and the tumor significantly reduced the risk of postoperative loss of function.


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