NeuroImage
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Whilst MRI is routinely used for the assessment and diagnosis of multiple sclerosis, there is poor correspondence between clinical disability in primary progressive multiple sclerosis (PPMS) patients and conventional MRI markers of disease activity (e.g., number of enhancing lesions). As PPMS patients show diffuse and global myelin loss, the aim of this study was to evaluate the efficacy of whole-brain myelin water fraction (MWF) imaging in PPMS. Specifically, we sought to use full-brain analysis techniques to: 1) determine the reproducibility of MWF estimates in PPMS brain; 2) compare MWF values in PPMS brain to healthy controls; and 3) establish the relationship between MWF and clinical disability, regionally and globally throughout the brain. ⋯ A significant correlation was found between the volume of significantly reduced MWF and clinical disability (p=0.008, R=0.58). Our results show that clinical disability is reflected in particular regions of cerebral white matter that are consistent between subjects, and illustrates a method to examine tissue alteration throughout the brain of individual patients. These results strongly support the use of MWF imaging to evaluate disease activity in PPMS.
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Several brain structures have been consistently found to be involved in visceral pain processing. However, recent research questions the specificity of these regions and it has been suggested that it is not singular activations of brain areas, but their cross-communication that results in perception of pain. Moreover, frequency at which neurons are firing could be what separates pain from other sensory modalities which otherwise involve the same anatomical locations. In this test/retest study, we identified the network of sources and their frequencies following visceral pain. ⋯ This study gives evidence of operculum's central integrative role for perception of pain and shows that MMP is a reliable method to study upstream brain activity.
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The role of operculo-insular region in the processing of somato-sensory inputs, painful or not, is now well established. However, available maps from previous literature show a substantial overlap of cortical areas activated by these stimuli, and the region referred to as the "secondary somatosensory area (SII)" is widely distributed in the parietal operculum. Differentiating SII from posterior insula cortex, which is anatomically contiguous, is not easy, explaining why the "operculo-insular" label has been introduced to describe activations by somatosensory stimuli in this cortical region. ⋯ Pain stimuli induced the most widespread and intense activation that was bilateral in SII (OP1, OP4) and distributed to all sub-regions of contralateral insula (except OP2) and to the anterior part of the ipsilateral insula (PreCG, MSG, ASG). However, the posterior granular part of insula contralateral to stimulus (Ig area) and the anterior part of SII bilaterally (OP4) were specifically activated during pain stimulation. This raises the question whether these latter areas could be the anatomical substrate of the sensory-discriminative processing of thermal pain.