NeuroImage
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The regions at risk of ischemia following cardio-respiratory arrest have not been systematically analysed. This knowledge may be of use in determining the mechanism of ischemic injury at vulnerable sites. The aim of this study is to evaluate the use of principal component analysis to analyse the covariance patterns of hypoxic ischemic injury. ⋯ The sensitivity analysis showed that the pattern of ischemic injury did not change when the analysis was restricted to patients who died. In conclusion, PCA method has many advantages over probabilistic method. In the context of this dataset, PCA showed covariance between deep grey matter nuclei and the posterior cortical structures whereas the probabilistic map provided complementary information on the frequency of occurrence at these locations.
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[(18)F]fluoroethoxybenzovesamicol ([(18)F]FEOBV) is one of the most promising radioligands for imaging the vesicular ACh transporter (VAChT) with positron emission tomography (PET). We report here that this method can detect subtle cholinergic terminals losses such as those associated with aging, or those following a partial lesion of the nucleus basalis magnocellularis (NBM). Twenty-one adult rats were evenly distributed in three groups including 1) aged rats (18 months); 2) young rats (3 months); and 3) rats with unilateral lesion of the NBM, following a local stereotaxic infusion of 192 IgG-saporin. ⋯ This binding distribution is consistent with the known anatomy of brain cholinergic systems. In the lesioned rats, [(18)F]FEOBV binding was found to be reduced mostly in the ventral frontal cortex on the side of the lesion, but some reductions were also observed in the homologous region of the contralateral hemisphere. Aging was found to be associated with a [(18)F]FEOBV binding reduction limited to the hippocampus of both hemispheres. [(18)F]FEOBV appears to be a very promising marker for the in vivo quantification of the brain VAChT; PET imaging of this agent allows in vivo detection of both physiological and pathological reductions of cholinergic terminals density.
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Multimodal imaging improves the accuracy of the localization and the quantification of brain activation when measuring different manifestations of the hemodynamic response associated with cerebral activity. In this study, we incorporated cerebral blood flow (CBF) changes measured with arterial spin labeling (ASL), Diffuse Optical Tomography (DOT) and blood oxygen level-dependent (BOLD) recordings to reconstruct changes in oxy- (ΔHbO(2)) and deoxyhemoglobin (ΔHbR). Using the Grubb relation between relative changes in CBF and cerebral blood volume (CBV), we incorporated the ASL measurement as a prior to the total hemoglobin concentration change (ΔHbT). ⋯ Moreover, our approach allows the computation of baseline total hemoglobin concentration (HbT(0)) as well as of the BOLD calibration factor M on a single subject basis. We obtained an average HbT(0) of 71 μM, an average M value of 0.18 and an average increase of 13% in cerebral metabolic rate of oxygen (CMRO(2)), all of which are in agreement with values previously reported in the literature. Our method yields an independent measurement of M, which provides an alternative measurement to validate the hypercapnic calibration of the BOLD signal.
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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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The perception of airways irritation is represented in a distributed brain network. However, the functional roles of sub-regions of this network are yet to be determined. The aim of this study was to measure brain activation in healthy participants as they inhaled two doses of capsaicin to identify dose-dependent and dose-independent responses. ⋯ Activation in the somatosensory and mid-cingulate cortices correlated with ratings of urge-to-cough. In the brainstem, capsaicin produced dose-dependent activations in respiratory-related regions of the dorsal pons and lateral medulla. These data show dissociable response patterns to capsaicin inhalation that may represent different regional processes involved in monitoring and assessing stimulus intensity, determining the spatial localization of the stimulus and suppressing motor responses.