NeuroImage
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Observational studies investigating the association between smoking, cognitive decline and dementia have produced conflicting results. We completed this trial to determine if smoking cessation decreases the progression of cognitive decline in later life. ⋯ These results are consistent with the hypothesis that smoking causes cognitive decline and loss of gray matter tissue in the brain over time.
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Signal loss in gradient-echo echo planar imaging (GE-EPI) due to susceptibility-induced magnetic field inhomogeneity makes it difficult to assess the blood oxygenation level-dependent (BOLD) effect in fMRI investigations. The z-shim method that applies an additional gradient moment is one of the more popular methods of compensating for GE-EPI signal loss. However, this method requires a calibration sweep scan and post-processing to identify the optimal z-shim gradients, which slows down fMRI experiments. ⋯ The optimization procedure for obtaining negative and positive gradient moments generally requires about twenty GE-EPI repetitions. In conclusion, the proposed z-shim method includes an automated real-time framework to achieve a significant reduction in susceptibility-induced signal loss in GE-EPI with a minimal increase in calibration time. The proposed procedure is fully automatic and compatible with conventional GE-EPI and can thus serve as a pre-adjustment module in EPI-based fMRI researches.
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Correlation of diffusion tensor imaging (DTI) with histochemical staining for demyelination and axonal damage in multiple sclerosis (MS) ex vivo human cervical spinal cords. ⋯ Increased radial diffusivity can serve as a surrogate for demyelination. However, radial diffusivity was also altered with axon injury, suggesting that this measure is not pathologically specific within chronic human MS tissue. We propose that radial diffusivity can serve as a marker of overall tissue integrity within chronic MS lesions. This study provides pathologic foundation for on-going in vivo DTI studies in MS.
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The brainstem is the part of the human brain that plays a pivotal role in the maintenance of many critical body functions. Due to the elevated level of cardiogenic noise, few fMRI studies have investigated the brainstem so far. Cardiac-gated echo-planar imaging with acquisition of two echoes per excitation (dual-echo EPI) is one method that significantly reduces cardiogenic noise and, thus, allows for fMRI measurements of the brainstem. ⋯ Five methods were found to be sensitive for activation of both nuclei. These included FSL normalization with 3mm and 4.5mm pre-smoothing as well as 3mm post-smoothing, SPM unified normalization with 3mm pre-smoothing and ABC normalization with 4.5mm pre-smoothing. All these methods can be recommended for normalization and smoothing when analyzing fMRI data of the brainstem acquired by cardiac-gated dual-echo EPI.
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There is still controversy in the literature whether a single episode of mild traumatic brain injury (mTBI) results in short- and/or long-term functional and structural deficits in the concussed brain. With the inability of traditional brain imaging techniques to properly assess the severity of brain damage induced by a concussive blow, there is hope that more advanced applications such as resting state functional magnetic resonance imaging (rsFMRI) will be more specific in accurately diagnosing mTBI. In this rsFMRI study, we examined 17 subjects 10±2 days post-sports-related mTBI and 17 age-matched normal volunteers (NVs) to investigate the possibility that the integrity of the resting state brain network is disrupted following a single concussive blow. ⋯ The YMCA physical stress induced nonspecific and similar changes in brain network connectivity patterns in both the mTBI and NV groups. These major findings are discussed in relation to underlying mechanisms, clinical assessment of mTBI, and current debate regarding functional brain connectivity in a clinical population. Overall, our major findings clearly indicate that functional brain alterations in the acute phase of injury are overlooked when conventional clinical and neuropsychological examinations are used.