NeuroImage
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Spatial attention amplifies the neural response, i.e. spike rates, brain metabolism, and oscillatory activity at gamma frequency (beyond 30 Hz). In this study we show that when a visual target is attended enhanced synchrony between gamma phase (30 to 50 Hz) and theta phase (4 to 7 Hz), representing bottom-up and top-down activity, respectively, can be observed. ⋯ This seems to be true in particular for theta oscillations showing increased interregional phase-coupling. We conclude that memory information is stored within a distributed theta network and it is matched with an incoming sensory trace at posterior brain areas.
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Spinal cord fMRI is a useful tool for studying spinal mechanisms of pain, hence for analgesic drug development. Its technical feasibility in both humans and rats has been demonstrated. This study investigates the reproducibility, robustness, and spatial accuracy of fMRI of lumbar spinal cord activation due to transcutaneous noxious and non-noxious electrical stimulation of the hindpaw in alpha-chloralose-anesthetized rats. ⋯ Spatially, the fMRI signal extended approximately 5 mm in the longitudinal direction, covering L(3)-L(5) segments. In the cross-sectional direction, the highest signal change of blood volume-weighted fMRI was in the middle of the ipsilateral dorsal horn, which roughly corresponds to laminae V and VI, while the highest signal change of BOLD fMRI was in the ipsilateral dorsal surface. This study demonstrates that spinal cord fMRI can be performed in anesthetized rats reliably and reproducibly offering it as a potential tool for analgesic drug discovery.
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Diffusion Tensor Imaging (DTI) data is characterized by a high noise level. Thus, estimation errors of quantities like anisotropy indices or the main diffusion direction used for fiber tracking are relatively large and may significantly confound the accuracy of DTI in clinical or neuroscience applications. ⋯ It is applied to artificial phantom data and a brain scan. We show that this method significantly improves the quality of the estimate of the diffusion tensor, by means of both bias and variance reduction, and hence enables one either to reduce the number of scans or to enhance the input for subsequent analysis such as fiber tracking.
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Gender greatly influences pain processing. Not only do females display greater pain sensitivity, many chronic pain conditions affect females more than males. Although gender-based differences in pain sensitivity may be related to cultural and social factors, animal studies also reveal gender differences in pain sensitivity, suggesting that physiological factors may contribute to differences in the processing of pain in males and females. ⋯ In 24 healthy adults we used functional magnetic resonance imaging (fMRI) to measure signal intensity changes during muscle and cutaneous pain induced by intramuscular and subcutaneous injections of hypertonic saline, respectively. In addition to activating the "pain neuromatrix", i.e. cingulate, insular, somatosensory and cerebellar cortices, both muscle pain and cutaneous pain evoked gender-based differences in the mid-cingulate cortex, dorsolateral prefrontal cortex, hippocampus and cerebellar cortex. These differences may reflect differences in emotional processing of noxious information in men and women and may underlie the gender bias that exists in many chronic pain conditions.
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The corpus callosum (CC) is of great interest for pathophysiological models of schizophrenia. Volume and structural integrity of the CC have been examined by volumetric and diffusion tensor imaging (DTI) studies, but results were not consistent across methods or studies. A possible explanation may be varying methodologies and accuracy of measurements based on a single slice or small regions of interest. ⋯ The results emphasize the importance of using different methods in evaluation of white matter (WM) in schizophrenia to avoid false negative findings. In addition, the measures were highly correlated with each other, implying a common pathological process influencing FA, MD and volume of the CC. Although we cannot rule out other mechanisms affecting volume, FA and MD, converging evidence from cytoarchitectonic and genetic studies suggests that WM changes observed in schizophrenia may involve disintegration of healthy, functional axons and strengthening of aberrant connections resulting in increased severity of clinical symptoms.