We investigated somatosensory cortical activation in squirrel monkeys using high-field imaging (9.4T, Bruker) during vibrotactile and electrocutaneous stimulation of the hand. Accompanying high-resolution T1 anatomical experiments were used to define the laminar organization of SI. Vibrotactile stimulation was administered by piezoelectric elements that drove a circular contact (0.5 mm dia.) onto the surface of a digit segment. Electrocutaneous stimuli were presented via electrodes positioned on the digit volar surfaces and base of the palm. All stimuli were delivered in a blocked design. In T1-images, whole brain coverage was achieved with a 7 cm coil to achieve a 195µm in-plane resolution. For EPI data, a 3 cm coil was positioned over somatosensory cortex for a 625µm in-plane resolution. Isoflurane anesthesia (0.5-0.8%) was maintained by monitoring physiological variables (SpO2, BPM, CO2; see Cheney et al., this meeting). Data was acquired from two monkeys that were scanned over 20 fMRI sessions. Prelimi...

In this study we investigated how activity in the cerebellum is related to the ocular following of optokinetic stimulation. Eight healthy volunteers (of about 30 years of age) participated in three experiments. For each experiment, T2*-weighted single shot gradient echo EPI functional scans were acquired (TR/TE 3750/50ms, matrix size 64x64, slice thickness 4mm). The image data was processed with SPM-99 on both single-subject and group analysis level. In the first experiment, optokinetic eye movements were evoked by a random dot pattern with an infinite lifetime. In the second experiment, the optokinetic reflex was evoked by a random pattern of dots that had a limited lifetime (i.e., each dot was repositioned within 50 ms), which effectively excludes ocular following by smooth pursuit. As a control condition, smooth pursuit eye movements were evoked by a single dot in a third experiment. In each experiment a block design was used with three conditions of 30 seconds with 5 repetitions: the stimulus moved to ...

Introduction In this work we investigate how the hemodynamic changes evoked by D-amphetamine in normal and MPTP treated monkeys can be mapped using pharmacologic MRI (phMRI) and PET to validate the degree of dopaminergic denervation after MPTP treatment. Methods Macaca Fascicularis: 6 normal control monkeys and 3 MPTP treated monkeys (2 with minor and 1 with severe PD symptoms). MRI phMRI images of cerebral blood volume changes were collected on a Siemen's 3T allegra system for 60-120 minutes (50sec/image set). 1.5-2.5mg/kg amphetamine was used to probe dopaminergic function. PET 11C-CFT was used to assess the binding potential of the dopamine transporter protein (DAT) in the striatum. Results Administration of amphetamine to control monkeys produced strong phMRI activation in caudate, putamen, accumbens, thalamus, and substantia nigra (increase in CBV between 10-35%). There was much less cortical activation compared to our prior rat phMRI studies. For the MPTP-treated monkeys with minor symptoms and moder...

Attention-Deficit Hyperactivity Disorder (ADHD) is the most common psychiatric disorder among school-aged children, occurring in about 5% of the population. Between 40-70% of these children also portray a persistent pattern of antisocial behavior, referred to as Conduct Disorder (CD). Researchers using MRI to study children with ADHD have consistently attributed core deficits of inattention and impulsivity to frontal-striatal-cerebellar abnormalities; however, no study has investigated the neuroanatomical characteristics of children diagnosed with ADHD co-morbid with CD. This study examined a community sample of 12 children with ADHD (aged 8-12, 7 with CD) and 24 healthy controls matched for age, sex, handedness, and SES. Volume measurements, including right-left asymmetries, were quantified from MRI of the total brain and cerebellar vermis. No significant differences in brain size or asymmetry were found between the groups. Measurements of the left and total posterior superior and inferior lobes of the ve...

14C-labeled α-aminoisobutyric acid (AIB)-based quantitative autoradiography (QAR) was used to confirm MRI observations of loss of BBB integrity during reperfusion in a rat model of transient, unilateral, focal cerebral ischemia. All MRI observations were made using a 7-Tesla system. Diffusion- and T2-weighted imaging (DWI and T2WI, respectively) were performed during and after 3 hours of ischemia to identify the ischemic lesion. Qualitative and quantitative assessment of BBB integrity were done by serial scanning using T1-weighted imaging (T1WI) Look-Locker sequence to track a bolus injection of a gadolinium-chelate (Gd-DTPA). Immediately afterwards the rats were injected with a 14C-AIB bolus for QAR. The MRI images were processed to generate tissue segmentation maps and regions of interest (ROI) that demonstrated Gd-DTPA leakage. The ROI corresponded closely with regions showing 14C-AIB extravasation (i.e. BBB opening) on the autoradiograms. Transfer constants (Ki) were generated for the ROI from QAR data...

Therapeutic hypothermia has become standard therapy for term neonates with moderate to severe hypoxic-ischemic encephalopathy (HIE). In rodent animal models of neonatal brain hypoxia-ischemia, hypothermia showed different degrees of tissue sparing and r...

Anatomical MRI templates are commonly used in human neuroimaging to facilitate data analysis and comparison across subjects and studies. Template use is rare in non-human primate neuroimaging, in part because previous in vivo templates of the monkey bra...

Considering the close phylogenetic relationship between humans and chimpanzees, it is of particular interest to characterize the age-related changes of the chimpanzee brain that correspond to key foci of pathologic brain aging in humans such as hippocampus, entorhinal cortex, and basal ganglia. Recently, we reported that, unlike aged humans with neurodegenerative pathology, aged great apes have preserved neuron number and cellular volume in layer II neurons of the entorhinal cortex. In the present study, we measured the volume of the hippocampus, caudate nucleus, and putamen from magnetic resonance images (MRIs) of a cross-sectional age-graded sample of postmortem chimpanzee brains. Volumes of interest (VOIs) were measured from either axial T1 weighted or coronal T2 weighted scans, using MRIcro software. VOI measurements were normalized for whole brain volume. Whole brain, raw VOI, and normalized VOI volumes were not correlated with age. ANOVA found no differences in any VOI between age cohorts (19-27 and ...

Converging lines of evidence suggest that the Human Immunodeficiency Virus (HIV) can cause frontal-subcortical damage and cognitive dysfunction. Neuropsychological studies have demonstrated sensitivity of the Stroop Interference Task to HIV-related cognitive dysfunction, but the underlying pathophysiology is poorly understood. In this study, fMRI (1.5T Siemens, TR=2, 21 slices of 5 mm, blocked design, SPM '99) was used to compare patterns of brain activity in 9 HIV-positive (HIV+) and 8 HIV-negative (HIV-) males during performance of two Stroop-variant tasks. In the Counting Stroop (Bush '98), subjects used a button-press to indicate the number of animal names (neutral) or incongruent number words (interference) presented on a screen. HIV+ subjects were slower and more susceptible to interference than HIV- subjects. FMRI analysis (interference vs. neutral) showed that HIV+ subjects also recruited more regions of motor and parietal cortex compared to HIV- subjects. In the Oddball Stroop (Bush, personal comm...

It is still unclear to what extent cortical areas are involved in non-conscious processing of tactile stimuli. However, from subdural recordings of somatosensory evoked potentials in awake humans there is evidence for excitation of areas in the postcentral gyrus in response to peripheral subliminal electrical stimulation without any associated conscious sensation (Libet et al. 1967). For further investigation an fMRI study (6 subjects, mean age±S.D.=27.7±2.3 yrs) was performed with an 1.5 T scanner using echoplanar sequences (TR=2 s, FOV=256 mm, voxel size=4×4×5 mm, 16 slices). Blocks (10 scans) of subthreshold and suprathreshold electrical stimuli (pulse frequency=7 Hz, pulse duration=0.2 ms), at least 15% below (2.2±0.42 mA) and 15% above (3.1±0.62 mA) sensory threshold for conscious perception (2.7±0.52 mA), respectively, were scan triggered and delivered in a randomized order to the left index finger via ring electrodes. Parametrical maps were calculated using BrainVoyager. In the group analysis, subth...