Introduction: We present a nonmagnetic Plexiglas stereotaxic localizer box that can be fitted directly to the pig skull by aluminum screws, allowing stereotaxic MRI or ventriculography and subsequent high-precision stereotaxic procedures. Methods: The localizer box was used to target the subthalamic nucleus (STN) bilaterally in 5 female Göttingen minipigs. Stereotaxic markers were inserted in the pig skull, the head fixated in the localizer box by aluminum screws inserted bilaterally in the zygoma bone with the hard palate locked on a horizontal palate holder. MRI was obtained on a 3T-MR-imager revealing the relation between the inserted markers and the estimated STN-position, and thus the target coordinates. After the MRI a stereotaxic frame with attached micromanipulator was locked on to the localizer box converting it into a stereotaxic device. The stereotaxic markers were exposed and used as starting point for the stereotaxic procedure, whereby a microelectrode for electrolytic lesioning was inserted i...

We recently reported preliminary data suggesting Constraint Induced Therapy (CIT), a promising intervention to enhance motor recovery from stroke, may be associated with increases in motor cortical projections to the weak finger muscles as measured by transcranial magnetic stimulation (TMS; 1). Here we report the results of parallel functional MRI (fMR) studies. METHODS: As part of an ongoing multicenter project, hemiparetic patients received CIT within one year of their stroke. fMR was performed prior to CIT (baseline), 2 weeks later, and at 4 months. During fMR patients repeatedly extended/flexed their paretic fingers at 70% maximal rate for 30 second blocks alternating with rest. fMR maps were generated with SPM99. RESULTS: One chronic and four subacute patients are included. There was considerable variability between patients. In many, both hemispheres showed increased activation at 2 weeks compared to baseline, more on the side of the stroke. These changes persisted or increased at 4 months. Fugl-Meye...

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 ...

This investigation demonstrates that Magnetic Resonance Imaging (MRI) can be used to determine the localization of implanted multichannel silicon microelectrodes with good spatial resolution, unnoticeable image distortions, and imaging times within acceptable ranges for in vivo studies. Four-shank 16-channel MRI-compatible silicon microelectrodes, used for neural recording and stimulation of the Central Nervous System (CNS) in animal models, were tested on 9.4 and 2 Tesla (T) animal research magnets. At high magnetic fields (9.4T), Spin Echo images with in plane resolution of 30μm x 30μm, showed a detectable volume void caused by the individual shanks of the microelectrode, precisely showing its location. At low magnetic fields (2T), Gradient Echo (GE) phase images, with in plane resolution of 100μm x 100μm and after phase unwrapping and image differentiation, showed enough signal dephasing to outline the overall shape of the electrode although individual shanks were not distinguished. For users or applica...

According to the amyloid hypothesis, it is the progressive accumulation of β-amyloid that leads to a cascade of neurodegenerative processes in Alzheimer's disease (AD). Thus, current strategies for diagnosis and treatment evaluation rely on the ability to accurately quantify β-amyloid burden. It has previously been shown that β-amyloid plaques can be imaged using Magnetic Resonance Microscopy (MRM) at 40μm isotropic resolution in ex vivo human samples of the hippocampus. Transgenic (Tg) mice have been generated for research as β-amyloidosis models. Plaque sizes range can from 5μm to 200μm, with an average diameter of approximately 25μm. In the present study, we used high resolution MRM to explore the feasibility of visualizing β-amyloid plaque deposits in the brain of Tg2576 mice carrying the Swedish mutation of APP. We obtained T2 weighted 3D whole brain MRM data at 20μm and 25μm isotropic resolution. MRM images were compared with histological data to confirm that the signal seen on MRM corresponded to ac...

Reports suggest that depressed patients with more WMLs on T2W MRI have decreased response rates to antidepressant treatment, perhaps due to interruption of pathways involved in emotional regulation. To systematically identify WML number and location, we studied late-life depression using T2W and 3D T1W MRI. T2W scans were performed using 2D TSE: TR 4000ms, TE 97ms, 17 echoes, 2mm thickness, 10mm gap, 6 interleaves, 256x256x108, (1x1x2mm). Four separate sagittal 3D T1W scans were performed with MP-RAGE: TR 1900ms, TE 4ms, TI 1100ms, 222x256x128 (1x1x1.25mm). The T1W scans were coregistered to correct for head motion prior to averaging. The TSE scans were coregistered with the T1W scans and both were transformed into Talairach space. Parabolic gain field corrections were performed on both images to allow whole brain tissue type determination. A 2D histogram of pixel values was used to identify peaks for CSF, air, gray matter, white matter and two soft tissues. WML pixels were separated from both white and gr...

Executive cognitive processes have been implicated in a wide variety of cognitive tasks, from maintenance of an item in working memory to selection of an infrequent response. The current study investigated whether working memory and response selection cues evoke transient activity in similar brain regions, using functional magnetic resonance imaging (fMRI) at 4T. Subjects viewed a series of simple shapes (triangles and circles) presented one at a time in a rapid sequence, with each shape visible for 500ms with a 1000ms interstimulus interval. Most stimuli were black and task-irrelevant. On infrequent oddball trials (10%), the stimuli were blue and required a button press response, regardless of its shape. On encoding trials (5%), the stimuli were green and subjects remembered their shape. On subsequent retrieval trials (5%) presented in red, the subject pressed a button if the presented shape matched that on the previous encoding trial. The encoding and retrieval stimuli were separated by intervals of betw...

Although the role of the frontal cortex in executive performance has been widely accepted, issues regarding the contribution of subcortical structures to these functions remain unresolved. In this study, the neural circuitry underlying selective sub-components of working memory was investigated using event-related functional magnetic resonance imaging (fMRI). Ten healthy volunteers performed a verbal memory task, which allowed different aspects of working memory function such as maintenance, retrieval and manipulation to be tested within the same general paradigm. During performance of this task as a whole, fMRI revealed increases in signal intensity throughout the frontostriatal network. However, when signal intensity during the manipulation of information within working memory was compared to that during periods requiring only simple maintenance and retrieval, significant changes were observed only in the caudate nuclei, bilaterally. These results suggest an essential and specific role for the caudate nu...

We present a neuroanatomical study of the harbor porpoise (Phocoena phocoena) brain using Magnetic Resonance Imaging (MRI). The specimen is the postmortem brain of a stranded adult harbor porpoise. Magnetic resonance images of the entire brain were acquired in the coronal plane with a 1.5 T Philips NT scanner (Philips Medical System, The Netherlands) at Emory University School of Medicine. Computer-generated 3D reconstructed images were created using the software programs VoxelView and VoxelMath programs (Vital Images, Inc.). The 3D rendered model was then digitally resectioned in orthogonal planes to produce corresponding virtual section series in the horizontal and sagittal planes. Morphometric analyses were conducted using the computer-based program Scion Image. In this poster we present both qualitative and quantitative data on various structures and features of the harbor porpoise brain. This study represents one of a very few studies of the harbor porpoise brain and provides critical data for compara...

The olfactory system is a unique route for uptake and transport of materials to the central nervous system. The purpose of this study is to trace transport of a paramagnetic substance, manganese, in the rat olfactory system using serial magnetic resonance imaging. Sequential magnetic resonance imaging on a 1.5T MR scanner using a rat brain volume coil and 3D SPGR pulse sequence was performed at pre-injection, and 6, 9, 12, 24, 36, and 48 hour post injection of 10 microliter MnCl2 solution via polyethylene catheter into the right nasal cavity in 5 male Sprague Dawley rats under isoflurane anesthesia. Changes in signal intensity were measured by region-of-interest analysis as well as voxel-by-voxel subtraction analysis of post-pre injection images using image coregistration. Signal intensity changes of greater than 1.9 target to muscle ratio were seen progressively in the right olfactory epithelium (post injection), olfactory bulb (< 6 hrs), olfactory tubercle (<9 hrs), piriform cortex (<9 hrs), and entorhin...