NeuroImage
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This paper presents a method for automatic segmentation of white matter fiber bundles from massive dMRI tractography datasets. The method is based on a multi-subject bundle atlas derived from a two-level intra-subject and inter-subject clustering strategy. This atlas is a model of the brain white matter organization, computed for a group of subjects, made up of a set of generic fiber bundles that can be detected in most of the population. ⋯ An atlas bundle is represented by the multi-subject list of the centroids of all intra-subject clusters in order to get a good sampling of the shape and localization variability. The atlas, composed of 36 known deep white matter bundles and 47 superficial white matter bundles in each hemisphere, was inferred from a first database of 12 brains. It was successfully used to segment the deep white matter bundles in a second database of 20 brains and most of the superficial white matter bundles in 10 subjects of the same database.
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Traumatic brain injury (TBI) is a leading cause of sustained impairment in military and civilian populations. However, mild (and some moderate) TBI can be difficult to diagnose because the injuries are often not detectable on conventional MRI or CT. Injured brain tissues in TBI patients generate abnormal low-frequency magnetic activity (ALFMA, peaked at 1-4 Hz) that can be measured and localized by magnetoencephalography (MEG). ⋯ Among 96 cortical regions, the likelihood of abnormal slow-wave generation was less in the mild TBI patients with blast than in the mild non-blast TBI patients, suggesting possible protective effects due to the military helmet and armor. Finally, the number of cortical regions that generated abnormal slow-waves correlated significantly with the total post-concussive symptom scores in TBI patients. This study provides a foundation for using MEG low-frequency source imaging to support the clinical diagnosis of TBI.
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Animal and human autopsy studies suggest that subfields of the hippocampal formation are differentially affected by neuropsychiatric diseases. Therefore, subfield volumes may be more sensitive to effects of disease processes. The few human studies that segmented subfields of the hippocampal formation in vivo either assessed the subfields only in the body of the hippocampus, assessed only three subfields, or did not take the differential angulation of the head of the hippocampus into account. ⋯ In conclusion, this study shows that it is possible to delineate the main subfields of the hippocampal formation along its full-length in vivo at 7 T MRI. Our data give evidence that this can be done in a reliable manner. Segmentation of subfields in the full-length of the hippocampus may bolster the study of the etiology neuropsychiatric diseases.
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In the context of focal and drug-resistant epilepsy, surgical resection of the epileptogenic zone may be the only therapeutic option for reducing or suppressing seizures. In many such patients, intracranial stereo-EEG recordings remain the gold standard for the epilepsy surgery work-up. Assessing the extent of the epileptogenic zone and its organisation is a crucial objective, and requires advanced methods of signal processing. ⋯ Our findings also indicate that the cortical regions beyond the dysplasia involved in the ictal activity essentially act as "secondary" generators of synchronous activity. The leading role of the lesional zone may account for the good post-surgical outcome of patients with type II focal cortical dysplasia as resecting the dysplasia removes the epileptogenic zone responsible for seizure organisation. Furthermore, our findings strongly suggest that advanced signal processing techniques aimed at studying synchronisation and characterising brain networks could substantially improve the pre-surgical evaluation of patients with focal epilepsy, even in cases without an associated anatomically detectable lesion.
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Harm Avoidance is a temperament trait that associates with sensitivity to aversive and non-rewarding stimuli, higher anticipated threat and negative emotions during stress as well as a higher risk for affective disorders. The neurobiological correlates of interindividual differences in Harm Avoidance are largely unknown. We hypothesized that variability in Harm Avoidance trait would be explained by differences in the activity of μ-opioid system as the opioid system is known to regulate affective states and stress sensitivity. ⋯ These associations were driven by two subscales of Harm Avoidance; Shyness with Strangers and Fatigability and Asthenia. In conclusion, higher Harm Avoidance score in healthy subjects is associated with higher μ-opioid availability in regions involved in the regulation of anxiety as well as in the control of emotions, affective component of pain and interoceptive awareness. The results have relevance in the research of vulnerability factors for affective disorders.