For a more accurate determination of a thalamic lesion or target for neurosurgical intervention as well as for a better interpretation of functional MRIs and PET studies, we are currently preparing a 3-D atlas of the human thalamus. For the present study, 5 brains have been used from human subjects without known neurological or psychiatric deficits. Postmortem MRIs were taken before brains were paraffin embedded, cut in the frontal plane at a thickness of 20 μm and stained with Gallyas modification for neuronal cell bodies. Cytoarchitectonic criteria, in particular cell density, cell size and shape, as well as arrangement of cells, were used to delineate the various thalamic nuclei in sections taken at an interval of about 1 mm. The mammillary bodies, mammillothalamic tract, habenula, subthalamic nucleus, and nucleus ruber were included in the 3-D atlas as additional landmarks. The Gallyas-stained sections with the delineated cell masses were superimposed on the postmortem 3-D MRIs after local affine trans...

Functional magnetic resonance imaging (fMRI) has previously been used in humans to show functional separation between activation of dorsal and ventral visual areas using three dimensional structure from motion (SFM) stimuli (Naumer et al., Human Brain Mapping Abstr. 2000). We used identical stimuli to measure BOLD signals in ketamine anesthetized macaque monkeys (N=5). This imaging technique has recently been applied to monkeys anesthetized with isoflurane in a high magnetic field (4.7 T) scanner (Logothetis et al., 1999) and to awake monkeys in a standard 1.5T scanner (Vanduffel et al., Soc. Neurosci. Abst. 1998). Our fMRI study was performed at 1.5T using standard EPI sequences (Siemens Magnetom Vision, 8-16 slices, voxel size: 1.6 - 3.2 mm3, TR = 2-3 s). The head of the anesthetized monkeys was restrained in sphinx position with bolt implant and custom head holder or in supine position with cushions. Eye refraction was corrected with contact lenses. FMRI signals was analyzed using BrainVoyager 2000 incl...

Brain atrophy is a consistent finding in patients with multiple sclerosis (MS). The present study investigated if the amount of glucocorticoids (GC), administered as treatment for acute episodes of MS, can serve as an additional explanatory factor for this finding. From a total of 379 patients with relapsing-remitting MS, baseline and two year follow up Magnetic Resonance Imaging (MRI) scans of 27 cases were selected. During the trial period, 14 patients had received high doses of glucocorticoid treatment, while 13 patients were without treatment. Subjects in both groups were matched for gender, age, and evaluation on the Expanded Disability Status Scale (EDSS) at study begin (0-4,5). T1 weighted images with 3mm axial contiguous slices were acquired. All MR images were transformed into standard stereotaxic space. Volumetric analyses were performed for white matter, gray matter, hippocampus, and ventricles using both manual and automatic segmentation procedures. The GC treatment group showed significant atr...

Functional magnetic resonance imaging (fMRI) of primary olfactory cortex (POC) has yielded inconsistent results. Odorant-induced POC activity is present at times and absent at others even within the same lab using the same task. Most statistical models used to analyze fMRI data rely on two assumptions: 1. a monotonic transform from stimulus magnitude to neural activity quantity, and 2. a linear transform from neural activity quantity to MR signal magnitude. Whereas the latter has been demonstrated for MR (Boynton et al 1996), the former has not been demonstrated for POC. An equally viable alternative to a rate-encoding model is a temporal-encoding model. Models of temporal-encoding imply no monotonic transform from stimulus magnitude to neural activity quantity. Thus, fMRI is a potentially invalid measure of POC activity under temporal-encoding models. To address this issue we set out to quantify the stimulus magnitude dependence in POC in thirty subjects. An olfactometer generated low, medium and high con...

Significant white matter signal alteration is a frequent finding in both individuals with HIV (HIV+) and normal elderly subjects seronegative for HIV (HIV-). As the incidence of HIV in older individuals increases, the detection of white matter abnormalities (WMA) related to HIV in the elderly presents a challenge. The present study compared WMA in these groups using MRI morphometry. Analyses were performed on 122 HIV- subjects aged 20 to 99 years, and 42 HIV+ subjects aged 25 to 55 years. Volumes of WMA in the HIV+ group resembled those of HIV- individuals who were more than 30 years older. To investigate whether there were regional differences in WMA, three groups were compared: a younger HIV- group aged 25 to 50 (HIV-Y), HIV+ subjects in this age range (HIV+Y), and HIV- individuals aged 60-75 (HIV-O). Both HIV-O and HIV+Y groups exhibited significant increases in the volume of WMA, relative to the HIV-Y group, across multiple regions including the 4 cerebral lobes and a region of deep white matter surrou...

The human sense of smell plays an important role in appetite and food intake, detecting environmental threats, social interactions, and memory processing. However, little is known about the neural circuity supporting its function. The olfactory tracts project from the olfactory bulb along the base of the frontal cortex, branching into several striae to meet diverse cortical regions. Historically, using diffusion magnetic resonance imaging (dMRI) to reconstruct the human olfactory tracts has been prevented by susceptibility and motion artifacts. Here, we used a dMRI method with readout segmentation of long variable echo-trains (RESOLVE) to minimize image distortions and characterize the human olfactory tracts in vivo . We collected high-resolution dMRI data from 25 healthy human participants (12 male and 13 female) and performed probabilistic tractography using constrained spherical deconvolution (CSD). At the individual subject level, we identified the lateral, medial, and intermediate striae with their re...

Humans detect motions of images defined not only by luminance difference (first-order) but images segregated by the second-order characteristics such as texture, contrast, and so on. There have been few electrophysiological studies addressed on the mechanism underlying the second-order motion detection. First, we measured the magnetoencephalographic (MEG) response to the second-order motion defined by the sinusoidally modulated dots speeds but there was no obvious responses detected whereas the responses to the first-order sinusoidal grating at the same speed (2.6 deg/s) were found peaking at about 310 ms. Second, we measured the MEG responses to the apparent motions of the square areas. The areas were defined by the three characteristics: difference in the dots speeds (second-order apparent motion; SA), luminance of the dots (first-order; FA), and dots speeds and luminance (mixed; MA). For all the stimuli, MEG latencies decreased and the amplitudes increased as the motion distance increased. The latencies...

Despite neuropathological evidence for significant neuronal and glial cell reductions in specific cortical regions in bipolar disorder, MRI studies have not consistently demonstrated either global or regional cortical gray matter reductions. Several MRI studies have suggested that brain abnormalities may be more prominent in familial mood disorders. Therefore, this study examined DSE and MP-RAGE MRI images of 20 familial bipolar I subjects (age 38.9 ± 9.4 years) and 45 control subjects (age 34.6 ± 10.4 years) utilizing quantitative MRI tissue segmentation and Talairach-atlas based volumetric techniques. ANCOVA with age, sex, and intracranial volume as covariates was used for statistical analysis. The bipolar I disorder group demonstrated significantly increased sulcal (p=0.010) and ventricular CSF (p=0.015), as well as decreased white matter (p=0.043) and cortical gray matter(p=0.009). To further investigate the cortical gray matter reduction, Talairach atlas-based regional voluming revealed significantly ...

Smart molecular probes for both diagnostic and therapeutic purposes are expected to provide quantum advances in clinical medicine and biomedical research. We describe such a probe that targets β-amyloid plaques of Alzheimer’s disease and is detectable by magnetic resonance imaging (MRI) because of contrast imparted by gadolinium labeling. Three essential properties are shown to exist in this smart molecular probe, putrescine-gadolinium-amyloid-β peptide: 1) transport across the blood-brain-barrier following intravenous injection which is conferred by the polyamine moiety, 2) binding to plaques with high affinity by the putrescine-labeled amyloid-β peptide, and 3) MRI detectability conferred by the contrast agent, gadolinium. MRI was performed on ex vivo tissue specimens at a spatial resolution approximating plaque size (62.5 μm3), in order to prove the concept that the probe can selectively enhance plaques when administered intravenously. The plaque-to-background tissue contrast-to-noise ratio, that was pr...

Sensitivity changes, beginning at the first stages of visual transduction, permit neurons with modest dynamic range to respond to contrast variations across an enormous range of mean illumination. We have used functional magnetic resonance imaging (fMRI) to investigate how these sensitivity changes are controlled within the visual pathways. We measured responses in human visual area V1 to a constant-amplitude, contrast-reversing probe presented on a range of mean backgrounds. We found that signals from probes initiated in the L and M cones were affected by backgrounds that changed the mean absorption rates in the L and M cones, but not by background changes seen only by the S cones. Similarly, signals from S cone-initiated probes were altered by background changes in the S cones, but not by background changes in the L and M cones. Performance in psychophysical tests under similar conditions closely mirrored the changes in V1 fMRI signals. We compare our data with simulations of the visual pathway from phot...