NeuroImage
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White matter (WM) fractional anisotropy (FA) is thought to be related to WM integrity and decline in FA is often used as an index of decreasing WM health. However, the relationship of FA to other structural indices of cerebral health has not been well studied. We hypothesized that the decline in WM health will be associated with changes in several other indices of cerebral health. ⋯ Intra-hemispheric correlations between FA and other measures of cerebral health had generally greater effect sizes than inter-hemispheric correction, with correlation between left FA and left GM thickness being the most significant (r=0.6, p<0.01). Regional analysis of FA values showed that late-myelinating fiber tracts of the genu of corpus callosum had higher association with other cerebral health indices. These data are consistent with the hypothesis that late-myelinating regions of the brain bear the brunt of age-related degenerative changes.
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High resolution ex vivo diffusion tensor imaging (DTI) studies of neural tissues can improve our understanding of brain structure. In these studies we can modify the tissue relaxation properties of the fixed tissues to better suite the scanner hardware. We investigated the use of Gd-DTPA contrast agent to provide the optimum signal-to-noise (SNR) ratio in 3D DTI scans of formalin fixed nonhuman primate brains at 4.7 T. ⋯ Studies of the temperature dependence of diffusion in these tissues suggested that a 30 degrees increase in sample temperature may yield an improvement of up to 55% in SNR-efficiency for a given diffusion weighting. Our Gd soaking regimen appeared to have no detrimental effect on standard histology of the fixed brain sections. Our methods yield both high SNR and spatial resolution DTI data in fixed primate brains, allowing us to perform high resolution tractography which will facilitate the process of 'validation' of DTI fiber tracts against traditional measures of brain fiber architecture.
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Extraversion and neuroticism are two important and frequently studied dimensions of human personality. They describe individual differences in emotional responding that are quite stable across the adult lifespan. Neuroimaging research has begun to provide evidence that neuroticism and extraversion have specific neuroanatomical correlates within the cerebral cortex and amygdala of young adults. ⋯ We observed that the thickness of specific lateral prefrontal cortex (PFC) regions, but not amygdala volume, correlates with measures of extraversion and neuroticism. The results suggest differences in the regional neuroanatomic correlates of specific personality traits with aging. We speculate that this relates to the influences of age-related structural changes in the PFC.
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Echo-planar imaging (EPI) generates considerable acoustic noise by rapidly oscillating gradients. In functional magnetic resonance imaging (FMRI), unshielded EPI sounds activate the auditory system inasmuch as it is responsive. Instead of attenuating EPI noise, our goal was to utilize it for auditory FMRI by omitting read-outs from the pulse sequence's gradient train. ⋯ We illustrate the applicability of this novel EPI modification for clinical diagnostic purposes and report on a patient with bilateral large vestibular aqueducts (LVAs) and severe binaural sensorineural hearing loss (SNHL). In this particular case, read-out omissions from EPI were used to assert residual audition prior to cochlear implantation (CI). Requiring no specific task compliance or sophisticated stimulation equipment other than the scanner on its own, FMRI by read-out omissions lends itself to auditory investigations and to quickly probe audition.
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Together with a detailed behavioral analysis, simultaneous measurement of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) permits a better elucidation of cortical pain processing. We applied painful electrical stimulation to 6 healthy subjects and acquired fMRI simultaneously with an EEG measurement. The subjects rated various stimulus properties and the individual affective state. ⋯ The BOLD signal change in ACC was positively correlated to the individual dipole strength of the source in ACC thus revealing a close relationship of BOLD signal and possibly underlying neuronal electrical activity in SI and the ACC. The BOLD signal change decreased in SI over time. Dipole strength of the ACC source decreased over the experiment and increased during the stimulation block suggesting sensitization and habituation effects in these areas.