NeuroImage
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The majority of nerve fibers in the spinal cord run longitudinally, playing an important role in connecting the brain to the peripheral nerves. There is a growing interest in applying diffusion tensor imaging (DTI) to the evaluation of spinal cord microarchitecture. The current study sought to compare the organization of longitudinal nerve fibers between healthy and myelopathic spinal cords using entropy-based analysis of principal eigenvector mapping. ⋯ In contrast, orientation entropy values in myelopathic cord were significantly higher at the compression site (0.91±0.03), and the adjacent levels (above: 0.85±0.03; below: 0.83±0.05). This study provides a novel approach to analyze the orientation information in diffusion MR images of healthy and diseased spinal cord. These results indicate that orientation entropy can be applied to determine the contribution of each compression level to the overall disorganization of principal nerve tracts of myelopathic spinal cord in cases with multi-level compression.
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This article has been withdrawn at the request of the authors. The Publisher apologizes for any inconvenience this may cause. ⋯ The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Randomized Controlled Trial
Ketamine effects on brain function--simultaneous fMRI/EEG during a visual oddball task.
Behavioral and electrophysiological human ketamine models of schizophrenia are used for testing compounds that target the glutamatergic system. However, corresponding functional neuroimaging models are difficult to reconcile with functional imaging and electrophysiological findings in schizophrenia. Resolving the discrepancies between different observational levels is critical to understand the complex pharmacological ketamine action and its usefulness for modeling schizophrenia pathophysiology. ⋯ The findings from our ketamine experiment are consistent across modalities and directly related to observations in schizophrenia supporting the validity of the model. Our investigation provides the first prototypic example of a pharmacoimaging study using simultaneously acquired fMRI/EEG.
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Medial temporal lobe (MTL) atrophy is one of the key biomarkers to detect early neurodegenerative changes in the course of Alzheimer's disease (AD). There is active research aimed at identifying automated methodologies able to extract accurate classification indexes from T1-weighted magnetic resonance images (MRI). Such indexes should be fit for identifying AD patients as early as possible. ⋯ The present automated MRI-based technique revealed a strong relationship between highly localized baseline-MRI features and the baseline clinical assessment. In addition, the classification index was also used to predict the probability of AD conversion within a time frame of two years. The definition of a single index combining local analysis of several regions can be useful to detect AD neurodegeneration in a typical MCI population.
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Spontaneous fluctuations in the blood oxygenation level-dependent (BOLD) signal, as measured by functional magnetic resonance imaging (fMRI) at rest, exhibit a temporally coherent activity thought to reflect functionally relevant networks. Antero-mesial temporal structures are the site of early pathological changes in Alzheimer's disease and have been shown to be critical for declarative memory. Our study aimed at exploring the functional impact of basal connectivity of an anterior temporal network (ATN) on declarative memory. ⋯ These correlations were specific to the ATN, as no correlation between performance on memory tasks and the other selected networks was found. Taken together, these findings provide evidence that basal connectivity inside the ATN network has a functional role in object-related, context-free memory. They also suggest that increased connectivity at rest within the ATN could reflect compensatory mechanisms that occur in response to early pathological insult.