Human brain mapping
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Human brain mapping · Dec 2007
Comparative StudyImaging mesial temporal lobe activation during scene encoding: comparison of fMRI using BOLD and arterial spin labeling.
Memory encoding is a critical brain function subserved by the hippocampus (HP) and mesial temporal lobe (mTL) structures. Visualization of mTL memory activation with BOLD fMRI is complicated by the presence of static susceptibility gradients in this region. Arterial spin labeled (ASL) perfusion fMRI offers an alternative approach not dependent on susceptibility contrast that instead suffers from lower intrinsic signal-to-noise ratio. ⋯ Perfusion fMRI using this approach with 4 mm isotropic resolution yielded better localized and stronger group activation maps than BOLD fMRI at a standard resolution of 3 mm isotropic voxels. Increasing the resolution for BOLD to 2.5 mm isotropic produced stronger mTL and hippocampal activation in the group and individual subjects than the ASL technique, due to superior temporal resolution and reduced partial volume effects. Future improvements in ASL spatial and temporal resolution would allow the benefits of both approaches to be combined to further enhance the sensitivity for detecting mTL activation during memory encoding.
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Human brain mapping · Dec 2007
Voxel-based morphometry study of brain volumetry and diffusivity in amyotrophic lateral sclerosis patients with mild disability.
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the progressive and simultaneous degeneration of upper and lower motor neurons. The pathological process associated to ALS, albeit more pronounced in the motor/premotor cortices and along the corticospinal tracts (CST), does not spare extra-motor brain gray (GM) and white (WM) matter structures. However, it remains unclear whether such extra-motor cerebral abnormalities occur with mildly disabling disease, and how irreversible tissue loss and intrinsic tissue damage are interrelated. ⋯ In ALS patients contrasted to controls, we also found significant clusters of locally increased MD (P < 0.001) in the splenium of the corpus callosum and in the WM adjacent to the IFG, STG, and middle temporal gyrus (MTG) of the right hemisphere, and in the WM adjacent to the MTG and lingual gyrus in the left hemisphere. Compared with controls, ALS patients also had significant clusters of locally decreased FA values (P < 0.001) in the CST in the midbrain and corpus callosum, bilaterally. This study supports the notion that ALS is a multisystem disorder and suggests that extra-motor involvement may be an early feature of the disease.