Objective To evaluate the reliability of MRI diffusion tensor tracking (DTT) of the amygdalo-calcarine pathway and for general neuroscience studies. Introduction DTT provides a means to assess white matter (WM) connections in living humans by tracing water diffusion. To use DTT, it is important to know its reliability. Methods We quantified vector distance errors by numerical simulation of the DTT procedures for an analytical curved pathway. We also assessed experimental reproducibility across subjects. Results Errors in track location at 6cm were 0.04±0.08mm (N=30) for standard conditions. The variance V of the error distance was proportional to track length L for almost all experimental conditions, with α=V/L strongly dependent on SNR, number of averages, and WM anisotropy. To gauge reproducibility, the amygdalo-calcarine tract involved in emotional modulation of visual perception was replicated across subjects, including a tight curve at the amygdala (arrows in Figure). Conclusion DTT errors have a pred...

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...

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...

Resting-state networks (RSNs) are increasingly forwarded as candidate biomarkers for neuropsychiatric disorders. Such biomarkers may provide objective measures for evaluating novel therapeutic interventions in nonhuman primates often used in translational neuroimaging research. This study aimed to characterize the RSNs of awake squirrel monkeys and compare the characteristics of those networks in adolescent and adult subjects. Twenty-seven squirrel monkeys [ n  = 12 adolescents (6 male/6 female) ∼2.5 years and n  = 15 adults (7 male/8 female) ∼9.5 years] were gradually acclimated to awake scanning procedures; whole-brain fMRI images were acquired with a 9.4 T scanner. Group-level independent component analysis (ICA; 30 ICs) with dual regression was used to detect and compare RSNs. Twenty ICs corresponding to physiologically meaningful networks representing a range of neural functions, including motor, sensory, reward, and cognitive processes, were identified in both adolescent and adult monkeys. The reprod...

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. At the individual subject level, we identified the lateral, medial, and intermediate striae with their respecti...

Although neurodevelopmental in origin, autism spectrum disorders are not currently diagnosed by neuroanatomical metrics but rather by behavioral observation. Autistic people differ from other people in their social interactions, communication, movement, and the level to which they focus on interests

The brain commonly exhibits spontaneous (i.e., in the absence of a task) fluctuations in neural activity that are correlated across brain regions. It has been established that the spatial structure, or topography, of these intrinsic correlations is in part determined by the fixed anatomical connectivity between regions. However, it remains unclear which factors dynamically sculpt this topography as a function of brain state. Potential candidate factors are subcortical catecholaminergic neuromodulatory systems, such as the locus ceruleus-norepinephrine system, which send diffuse projections to most parts of the forebrain. Here, we systematically characterized the effects of endogenous central neuromodulation on correlated fluctuations during rest in the human brain. Using a double-blind placebo-controlled crossover design, we pharmacologically increased synaptic catecholamine levels by administering atomoxetine, an NE transporter blocker, and examined the effects on the strength and spatial structure of res...

It is not known how the brain decides to act on moving objects. We demonstrated previously that neurons in the macaque supplementary eye field (SEF) reflect the rule of ocular baseball, a go/nogo task in which eye movements signal the rule-guided interpretation of the trajectory of a target. In ocular baseball, subjects must decide whether to pursue a moving spot target with an eye movement after discriminating whether the target will cross a distal, visible line segment. Here we identify cortical regions active during the ocular baseball task using event-related human functional magnetic resonance imaging (fMRI) and concurrent eye-movement monitoring. Task-related activity was observed in the SEF, the frontal eye field (FEF), the superior parietal lobule (SPL), and the right ventrolateral prefrontal cortex (VLPFC). The SPL and right VLPFC showed heightened activity only during ocular baseball, despite identical stimuli and oculomotor demands in the control task, implicating these areas in the decision pro...