NeuroImage
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Social anxiety disorder patients suffer from excessive anxious responses in social interaction leading to avoidance behavior and social impairment. Although the amygdala has a central role in perception and processing of threatening cues, little is known about the involved networks and corresponding dysfunctions in social anxiety. Therefore, this study aims to investigate the functional connectivity network of the amygdala in patients with social anxiety disorder and to identify regions that might influence amygdalar reactivity via modulatory pathways. ⋯ In addition, an exploratory analysis revealed further reduced functional connectivity and a marked functional separation between the medial orbitofrontal and anterior cingulate cortices in the patient group. Our results suggest alterations within the amygdalar functional connectivity network in social anxiety disorder. Combined with the amygdalar hyperactivation our findings corroborate the proposed dysfunction of the fronto-amygdalar inhibition in anxiety disorders and indicate a modulatory influence of the anterior and posterior cingulate cortices on threat perception and processing.
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MRI-based measurements of surface cortical thickness (SCT) have become a sensitive tool to quantify changes in cortical morphology. When comparing SCT to histological cortical thickness maps, a good correspondence can be found for many but not all human brain areas. Discrepancies especially arise in the sensory motor cortex, where histological cortical thickness is high, but SCT is very low. ⋯ After partial volume correction, two subsets with a differential relationship between SCT and BP(ND) were identified: a fronto-parietal homotypical subset where neuronal density is relatively constant and mainly independent of SCT, and a subset comprising heterotypical and mainly temporal and occipital homotypical regions where neuronal density is negatively correlated with SCT. This is the first in-vivo study demonstrating a differential relationship between SCT, neuronal density and cytoarchitectonics in humans. These findings are of direct relevance for the correct interpretation of SCT-based morphometry studies, in that there is no simple relationship between apparent cortical thickness and neuronal density, here attributed to FMZ binding, holding for all cortical regions.
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Epilepsy is a neurological disorder characterized by seizures, i.e. abnormal synchronous activity of neurons in the brain. During a focal seizure, the abnormal synchronous activity starts in a specific brain region and rapidly propagates to neighboring regions. Intracranial ElectroEncephaloGraphy (IEEG) is the recording of brain activity at a high temporal resolution through electrodes placed within different brain regions. ⋯ The full frequency ADTF outperforms the integrated ADTF and masked ADTF. Accordingly, we applied this full frequency ADTF to 4 seizure onset and 29 subclinical seizure IEEG recordings of a patient with refractory epilepsy. Hereby, we showed that connectivity patterns derived from IEEG recordings can provide useful information about seizure propagation and may improve the accuracy of the pre-surgical evaluation in patients with refractory epilepsy.
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Pseudocontinuous arterial spin labeling (PCASL), a newly proposed perfusion magnetic resonance imaging (MRI) technique, has the potential of providing a better balance between labeling efficiency and signal-to-noise ratio than conventional ASL methods. The advantage will not be exploitable until adequate reproducibility can be achieved. In this study, we investigated the reproducibility of PCASL on twelve healthy volunteers by taking into account the inclusion of correction for coil sensitivity (CS) and labeling efficiency (α). ⋯ With CS correction alone, coefficient of variance (CV) remained larger with PCASL than PASL (p=0.02). CV was 12% with CS-corrected PASL and 11% with PCASL when CS and α were corrected for in conjunction. We concluded that CS correction is necessary for ASL imaging when using phased array receiver and that after CS correction, PCASL requires α correction to provide reproducibility comparable to PASL.
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Voxel-based morphometry (VBM) is a widely applied method in computational neurosciences but it is currently recommended to compare only data collected at a single MRI scanner. Multi-site VBM would be a desirable approach to increase group size and, thus, statistical power. We aimed to assess if multi-site VBM is feasible on similar hardware and compare the magnitude of inter- and intra-scanner differences. 18 healthy subjects were scanned in two identical 3T MRI scanners using different head coil designs, twice in scanner A and once in scanner B. 3D T1-weighted images were processed with SPM8 and FSL4.1 and compared as paired t-test (scan versus re-scan) on a voxel basis by means of a general linear model (GLM). ⋯ Intra-scanner scan/re-scan differences were generally weaker and did not exceed a p<0.05 (FWE corrected) threshold in the GLM analysis. At 3T profound inter-scanner differences are to be expected that could severely confound an unbalanced VBM analysis. These are like related to the receive bias of the radio-frequency hardware.