NeuroImage
-
The segmentation of infant brain tissue images into white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) plays an important role in studying early brain development in health and disease. In the isointense stage (approximately 6-8 months of age), WM and GM exhibit similar levels of intensity in both T1 and T2 MR images, making the tissue segmentation very challenging. Only a small number of existing methods have been designed for tissue segmentation in this isointense stage; however, they only used a single T1 or T2 images, or the combination of T1 and T2 images. ⋯ We compared the performance of our approach with that of the commonly used segmentation methods on a set of manually segmented isointense stage brain images. Results showed that our proposed model significantly outperformed prior methods on infant brain tissue segmentation. In addition, our results indicated that integration of multi-modality images led to significant performance improvement.
-
Different pathological processes like demyelination and axonal loss can alter the magnetisation transfer ratio (MTR) in brain tissue. The standard method to measure this effect is to scan the respective tissue twice, one with and one without a specific saturation pulse. A major drawback of this technique based on spoiled gradient echo (GRE) sequences relates to its long acquisition time due to the saturation pulses. ⋯ In a multiple linear regression model, we found an association between MTR of cortical lesions and a clinical measure of disability (r= -0.407, p=0.035) in the bSSFP dataset only. The different relaxation weighting of the base images (T2/T1 in bSSFP, proton density in GRE) had no effects besides a larger spreading of the MTR values of the different NA structures. This was demonstrated by the nearly perfect linearity between the NA matter MTR of both techniques as well as in the absolute MTR differences between NA matter and the respective lesions.
-
Itch is an independent sensory modality and a very common symptom with manifold causes. However, the neuronal representation of itch perception in the central nervous system is not entirely understood and there is hardly any knowledge about neuronal correlates of itch in the human spinal cord. In the present study we aimed to identify itch-related neural activity in the cervical spinal cord in healthy volunteers employing high-resolution functional magnetic resonance imaging (fMRI). ⋯ Non-noxious cooling of histamine-treated skin compared to cooling of non-treated skin led to a significant increase in itch perception. On the neural level, itch was paralleled by activation in the dorsal horn of the spinal cord at the transition between spinal segment C5 and C6, ipsilateral to the side of stimulation. These results suggest that itch-related neural activity can be assessed noninvasively in humans at the spinal cord.
-
The human brain responds both before and during the application of aversive stimuli. Anticipation allows the organism to prepare its nociceptive system to respond adequately to the subsequent stimulus. The context in which an uncomfortable stimulus is experienced may also influence neural processing. ⋯ The scores of the psychological questionnaires and the rating of perceived anticipatory anxiety were included as covariates in the fMRI data analysis. Our experiments led to the following key findings: 1) the subgenual anterior cingulate cortex (sgACC) is the only activation site that relates to uncertainty in healthy volunteers and is directly correlated to individual questionnaire score for pain-related anxiety; 2) uncertain anticipation of rectal distension involved several relevant brain regions, namely activation of sgACC and medial prefrontal cortex and deactivation of amygdala, insula, thalamus, secondary somatosensory cortex, supplementary motor area and cerebellum; 3) most of the brain activity during anticipation, but not distension, is associated with activity of the central autonomic network. This approach could be applied to study the ANS impact on brain activity in various pathological conditions, namely in patients with chronic digestive conditions characterized by visceral discomfort and ANS imbalance such as irritable bowel syndrome or inflammatory bowel diseases.
-
Peripheral neuropathy often manifests clinically with symptoms of mechanical and cold allodynia. However, the neuroplastic changes associated with peripheral neuropathic pain and the onset and progression of allodynic symptoms remain unclear. Here, we used a chronic neuropathic pain model (spared nerve injury; SNI) to examine functional and metabolic brain changes associated with the development and maintenance of mechanical and cold hypersensitivity, the latter which we assessed both behaviorally and during a novel acetone application paradigm using functional MRI (fMRI). ⋯ These functional brain changes temporally coincided with early and sustained increases in both mechanical and cold sensitivity. SNI rats also showed increased glutamate within the ACC that correlated with behavioral measures of cold hypersensitivity. Together, our findings suggest that extensive functional reorganization within pain-related brain regions may underlie the development and chronification of allodynic-like behaviors.