To evaluate the histological finding of reversible cerebral ischemic tissue on perfusion and diffusion weighted MRI, we produced the animal models of reversible cerebral ischemia in 10 cats by means of MCA occlusion with transorbital approach for an hour. MRI was performed at 1,3,6,24 and 36 hrs after reperfusion. Perfusion (PWI) and diffusion (DWI) weighted images were obtained. We divided the ischemic zones into the reversible and irreversible DWI zone. PWI revealed increased rCBV in all regions of the affected hemisphere on initial few hours. On initial DWI, increased signal intensity lesions were seen at ipsilateral striatum, superior/inferior temporal gyri and some parts of inferior frontal gyrus. In 6 cats, ADC recovery was noted at superior temporal and inferior frontal gyri, which also showed increased rCBV until the last PWI while striatum showed depletion of rCBV. Tissue slices were obtained after the last MRI. TUNEL stain and DNA ladder analysis were performed. We investigated differences in the...

To single out visual perceptual impairment in children with multiple handicap, Stiers ea. (Brain Dev 21:397) evaluated visual perception against non-verbal intelligence. This procedure revealed impaired visual categorization of suboptimal object presentations in children with early ischaemic brain damage, but not in a control group with mental retardation. To confirm that these impairments are perceptual in nature, 3 children (7-10 yr.) with divers clinical features but impairment on the visual perception battery L94 relative to their non-verbal intelligence, underwent a structural MRI scan to ascertain whether their brain lesions converged in visual neural structures. All had spastic diplegia following preterm birth. Visual acuity was between 0.5 and 1.0. In addition, one child with periventricular leukomalacia (PVL) had normal IQ but specific learning disabilities, one child with PVL had specific non-verbal intelligence impairment, and the third child had non-ischaemic hydrocephalus with global mental re...

The current study examined the development of frontostriatal circuitry involved in overriding a competing or well learned behavioral set in favor of a novel response mapping. Imaging studies of motor response learning, such as serial reaction time tasks, have implicated the insula cortex and basal ganglia regions in the learning of novel response patterns. Given the delay in maturation of prefrontal cortex and the basal ganglia, we predicted a developmental difference in performance on tasks involving stimulus-response conflict, presumably related to the developmental delay in organization of this circuitry. Using functional MRI, we compared the brain activation elicited during well-learned and novel stimulus-response mappings. Nine right handed adults (mean age=24.5 years, 3 females) and nine right handed children (mean age=8.8 years, 4 females) were scanned while performing the stimulus-response compatibility task. Echo planar images (TR = 6000, TE = 40, 128 X 64) were acquired in twenty-six 5 mm contigu...

Ultra-high field magnetic resonance (MR) imaging provides the potential for detection of greater signal contrast associated with brain pathology. In this study, preliminary data were gathered to assess whether the pathology of Alzheimer's disease results in sufficient signal changes to distinguish it from normal brain. T2 images were acquired on an 8 Tesla whole body system of 1 cubic inch slices of hippocampus from human Alzheimer specimens and age/sex-matched normal controls. Two acquisitions with the spin echo sequence using TR=750ms and TE=20 and 50ms were collected. Images were reconstructed off-line using a Silicon Graphics workstation. T2 was then calculated for each pixel and displayed as a map. Regions of interest (3 pixels x 3 pixels) were drawn in hippocampal subregions. There was a significant difference in the T2 signal of the CA1 region sampled between groups (T-test). This suggests that signal intensity may be a useful marker for Alzheimer's disease using ultra-high field MR imaging. This co...

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

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...

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...