NeuroImage
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Comparative Study Clinical Trial
Activity in the fusiform gyrus predicts conscious perception of Rubin's vase-face illusion.
We localized regions in the fusiform gyrus and superior temporal sulcus that were more active when subjects viewed photographs of real faces than when they viewed complex inanimate objects and other areas in the parahippocampal gyrus and the lateral occipital lobe that showed more activity during the presentation of nonface objects. Event-related functional magnetic resonance imaging was then used to monitor activity in these extrastriate visual areas while subjects viewed Rubin's vase-face stimulus and indicated switches in perception. Since the spontaneous shifts in interpretation were too rapid for direct correlation with hemodynamic responses, each reported percept (faces or vase) was prolonged by suddenly adding subtle local contrast gradients (embossing) to one side or the other of the figure-ground boundary, stabilizing the percept. ⋯ To control for effects of the physical change to Rubin's stimulus (i.e., addition of embossing), we compared activity when the face contours were embossed after the subject had just reported the onset of perception of either faces or vase. Activity in the fusiform face area responded more strongly under the first condition, despite the fact that the physical stimulus sequences were identical. Moreover, on a trial-to-trial basis, the activity was statistically predictive of the subjects' responses, suggesting that the conscious perception of faces could be made explicit in this extrastriate visual area.
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Comparative Study Clinical Trial
Patterns of cerebral atrophy in dementia with Lewy bodies using voxel-based morphometry.
Previous cross-sectional MRI studies based on region-of-interest analyses have shown that increased cerebral atrophy is a feature of both Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD). Relative preservation of the hippocampus and temporal lobe structures in DLB compared to AD has been reported in region-of-interest-based studies. Recently, image processing techniques such as voxel-based morphometry (VBM) have been developed to provide an unbiased, visually informative, and comprehensive means of studying patterns of cerebral atrophy. ⋯ Regional gray matter volume loss was observed bilaterally in the temporal and frontal lobes and insular cortex of patients with DLB compared to control subjects. Comparison of dementia groups showed preservation of the medial temporal lobe, hippocampus, and amygdala in DLB relative to AD. Significant gray matter loss was also observed in the thalamus of AD patients compared to DLB.
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Clinical Trial
Cortical processing of noxious somatosensory stimuli in the persistent vegetative state.
The persistent vegetative state (PVS) is a devastating medical condition characterized by preserved wakefulness contrasting with absent voluntary interaction with the environment. We used positron emission tomography to assess the central processing of noxious somatosensory stimuli in the PVS. Changes in regional cerebral blood flow were measured during high-intensity electrical stimulation of the median nerve compared with rest in 15 nonsedated patients and in 15 healthy controls. ⋯ Moreover, in PVS patients, the activated primary somatosensory cortex was functionally disconnected from secondary somatosensory, bilateral posterior parietal, premotor, polysensory superior temporal, and prefrontal cortices. In conclusion, somatosensory stimulation of PVS patients, at intensities that elicited pain in controls, resulted in increased neuronal activity in primary somatosensory cortex, even if resting brain metabolism was severely impaired. However, this activation of primary cortex seems to be isolated and dissociated from higher-order associative cortices.
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The aim of the present study was the investigation of neural correlates of music processing with fMRI. Chord sequences were presented to the participants, infrequently containing unexpected musical events. ⋯ To what extent this network might also be activated by the processing of non-linguistic information has remained unknown. The present fMRI-data reveal that the human brain employs this neuronal network also for the processing of musical information, suggesting that the cortical network known to support language processing is less domain-specific than previously believed.
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Functional MRI (fMRI) can detect blood oxygenation level dependent (BOLD) hemodynamic responses secondary to local neuronal activity. The most commonly used method for detecting fMRI signals is the gradient-echo echo-planar imaging (EPI) technique because of its sensitivity and speed. However, it is known that much of the signal obtained with this approach arises from large veins, with additional contribution from the capillaries and venules. ⋯ This method is based on task-induced changes of the apparent diffusion coefficients (ADC), a signal that we demonstrate is generated in vascular compartments that only partially overlap with those generating the BOLD signal. The approach allows both the ADC-based maps and the more commonly used BOLD-based maps to be acquired simultaneously. The spatial overlap between these maps can be used to create composite maps that permit improved localization of the underlying neuronal activity patterns by identifying signals generated in those vascular components that are in closest proximity to the active neuronal populations of interest.