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Characterization of displaced white matter by brain tumors using combined DTI and fMRI

NEUROimage 2006年第4期30卷 1100-1111页

作者： Schonberg, Tom Pianka, Pazit Hendler, Talma Pasternak, Ofer Assaf, Yaniv Tel Aviv Univ Dept Neurobiochem Fac Life Sci IL-69978 Tel Aviv Israel Tel Aviv Univ Dept Psychol IL-69978 Tel Aviv Israel Tel Aviv Sourasky Med Ctr Levie Edersheim Gitter Inst Funct Brain Imaging Tel Aviv Israel Tel Aviv Univ Sch Comp Sci IL-69978 Tel Aviv Israel

In vivo white matter tractography by diffusion tensor imaging (DTI) has become a popular tool for investigation of white matter architecture in the normal brain. Despite some unresolved issues regarding the accuracy of DTI, recent studies applied DTI for delineating white matter organization in the vicinity of brain lesions and especially brain tumors. Apart from the intrinsic limitations of DTI, the tracking of fibers in the vicinity or within lesions is further complicated due to changes in diseased tissue such as elevated water content (edema), tissue compression and degeneration. These changes deform the architecture of the white matter and in some cases prevent definite selection of the seed region of interest (ROI) from which fiber tracking begins. We show here that for displaced fiber systems, the use of anatomical approach for seed ROI selection yields insufficient results. Alternatively, we propose to select the seed points based on functional MRI activations which constrain the subjective seed ROI selection. The results are demonstrated on two major fiber systems: the pyramidal tract and the superior longitudinal fasciculus that connect critical motor and language areas, respectively. The fMRI based seed ROI selection approach enabled a more comprehensive mapping of these fiber systems. Furthermore, this procedure enabled the characterization of displaced white matter using the eigenvalue decomposition of DTI. We show that along the compressed fiber system, the diffusivity parallel to the fiber increases, while that perpendicular to the fibers decreases, leading to an overall increase in the fractional anisotropy index reflecting the compression of the fiber bundle. We conclude that definition of the functional network of a subject with deformed white matter should be done carefully. With fMRI, one can more accurately define the seed ROI for DTI based tractography and to provide a more comprehensive, functionally related, white matter mapping, a very impor

关键词： Anisotropy Brain Edema/diagnosis Brain Edema/pathology Brain Edema/physiopathology Brain Mapping Brain Mapping Brain Neoplasms/diagnosis Brain Neoplasms/pathology Brain Neoplasms/physiopathology Cerebral Cortex/pathology Cerebral Cortex/physiopathology Diffusion Magnetic Resonance Imaging Dominance, Cerebral/physiology Humans image processing, computer-assisted Internal Capsule/pathology Internal Capsule/physiopathology Magnetic Resonance Imaging Neoplasm Invasiveness/pathology Nerve Fibers, Myelinated/pathology Nerve Fibers, Myelinated/physiology Neural Pathways/pathology Neural Pathways/physiopathology Neuropsychological Tests Pyramidal Tracts/pathology Pyramidal Tracts/physiopathology Reference Values

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An expanded conformation of single-ring GroEL-GroES complex encapsulates an 86 kDa substrate

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STRUCTURE 2006年第11期14卷 1711-1722页

作者： Chen, Dong-Hua Song, Jiu-Li Chuang, David T. Chiu, Wah Ludtke, Steven J. Baylor Coll Med Natl Ctr Macromol Imaging Verna & Marrs Mclean Dept Biochem & Mol Biol Houston TX 77030 USA Univ Texas SW Med Ctr Dept Biochem Dallas TX 75390 USA

Electron cryomicroscopy reveals an unprecedented conformation of the single-ring mutant of GroEL (SR398) bound to GroES in the presence of Mg-ATP. This conformation exhibits a considerable expansion of the folding cavity, with similar to 80% more volume than the X-ray structure of the equivalent cis cavity in the GroEL-GroES-(ADP)(7) complex. This expanded conformation can encapsulate an 86 kDa heterodimeric (alpha beta) assembly intermediate of mitochondrial branched-chain alpha-ketoacid dehydrogenase, the largest substrate ever observed to be cis encapsulated. The SR398-GroES-Mg-ATP complex is found to exist as a mixture of standard and expanded conformations, regardless of the absence or presence of the substrate. However, the presence of even a small substrate causes a pronounced bias toward the expanded conformation. Encapsulation of the large assembly intermediate is supported by a series of electron cryomicroscopy studies as well as the protection of both alpha and beta subunits of the substrate from tryptic digestion.

关键词： Adenosine Triphosphate/chemistry Cryoelectron Microscopy Crystallography, X-Ray Dimerization Escherichia coli/metabolism GroEL Protein/chemistry GroES Protein/chemistry Humans image processing, computer-assisted Ketone Oxidoreductases/chemistry Models, Molecular Molecular Conformation Mutation Protein Conformation Trypsin/chemistry

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Blood volume and hemoglobin oxygenation response following electrical stimulation of human cortex

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NEUROimage 2006年第1期31卷 66-75页

作者： Suh, Minah Bahar, Sonya Mehta, Ashesh D. Schwartz, Theodore H. Cornell Univ Dept Neurosurg Weill Med Coll Presbyterian Hosp New York NY 10021 USA

Our understanding of perfusion-based human brain mapping techniques relies on a detailed knowledge of the relationship between neuronal activity and cerebrovascular hemodynamics. We performed optical imaging of intrinsic signals at wavelengths sensitive to total hemoglobin (Hbt;which correlate with cerebral blood volume (CBV)) and deoxygenated hemoglobin (Hbr) directly in humans during neurosurgical operations and investigated the optical signals associated with bipolar cortical stimulation at a range of amplitudes. Cortical stimulation elicited a rapid focal increase in Hbr (initial dip) in all subjects. An equally rapid increase in Hbt (< 200 ms), with a slightly higher signal-to-noise ratio, was also highly localized for < 2 s in spite of the non-columnar nature of the stimulus, after which the signal spread to adjacent gyri. A later decrease in Hbr (> 3 s), which is relevant to the blood oxygen level dependent (BOLD) signal, was poorly localized. Increasing the stimulus amplitude elicited a linear increase in the area of the optical signal for Hbt and the initial dip but not the late decrease in Hbr, and a nonlinear increase in optical signal amplitude with a plateau effect for initial dip, Hbt and late decrease in Hbr. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Blood Volume/physiology Cerebral Cortex/blood supply Cerebral Cortex/physiopathology Craniotomy Electric Stimulation Electrodes, Implanted Electrodes, Implanted Electroencephalography Epilepsy/physiopathology Epilepsy/surgery Hemoglobins/metabolism Humans image Enhancement image processing, computer-assisted Magnetic Resonance Angiography Magnetic Resonance Imaging Neurons/physiology Oxygen/blood Oxyhemoglobins/metabolism Signal processing, computer-assisted

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Orientation-restricted continuous visual exposure induces marked reorganization of orientation maps in early life

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NEUROimage 2006年第2期30卷 462-477页

作者： Tanaka, S Ribot, J Imamura, K Tani, T RIKEN Brain Sci Inst Lab Visual Neurocomp Wako Saitama 3510198 Japan

To elucidate the effect of visual experience on the development of orientation maps, we conducted intrinsic signal optical imaging of the visual cortex of kittens that were continuously exposed to a single orientation through cylindrical-lens-fitted goggles under a freely moving condition starting at post-natal week 3. We observed a rapid reorganization of orientation maps, characterized by extensive representation of exposed orientations with reduced responsiveness to unexposed orientations. The over-representation of exposed orientation was marked for 1-2 weeks of goggle rearing. A longer period of goggle rearing, however, decreased the degree of over-representation, which still remained at a remarkable level. Dark rearing episodes daily interleaved between single orientation exposures moderated the over-representation effect. Unit recording from goggle-reared kittens showed preferred orientations consistent with optical imaging. Using c-Fos immunoreactivity mapping, we showed that the number of neurons strongly responding to the exposed orientation was 3 times larger in a goggle-reared cat than the number of neurons responding to the vertical orientation in a normal cat. Taken together, these results suggest that the reorganization of orientation maps was caused by the expansion of domains maximally responding to exposed orientation as well as the strong reduction of responses to unexposed orientations. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Algorithms Animals Brain/physiology Brain Mapping Brain Mapping Cats Electrodes, Implanted Electrodes, Implanted Electrophysiology image processing, computer-assisted Immunohistochemistry Immunohistochemistry Light Light Orientation/physiology Photic Stimulation Proto-Oncogene Proteins c-fos/biosynthesis Proto-Oncogene Proteins c-fos/physiology Vision, Monocular/physiology

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Spatial maps in frontal and prefrontal cortex

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NEUROimage 2006年第2期29卷 567-577页

作者： Hagler, DJ Sereno, MI Univ Calif San Diego Dept Cognit Sci La Jolla CA 92093 USA

Though the function of prefrontal cortex has been extensively investigated, little is known about the internal organization of individual prefrontal areas. Functional magnetic resonance imaging was used to show that some frontal and prefrontal cortical areas represent visual space in orderly, reproducible, topographic maps. The map-containing areas partly overlap dorsolateral prefrontal areas engaged by working memory tasks. These maps may be useful for attending to task-relevant objects at various spatial locations, an aspect of the executive control of attention. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Adult Attention/physiology Brain Mapping Brain Mapping Choice Behavior Female Frontal Lobe/anatomy & histology Functional Laterality/physiology Humans image processing, computer-assisted Magnetic Resonance Imaging Male Memory, Short-Term/physiology Middle Aged Photic Stimulation Prefrontal Cortex/anatomy & histology Psychomotor Performance/physiology Reaction Time/physiology Visual Fields/physiology

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Metaphorical vs. literal word meanings: fMRI evidence against a selective role of the right hemisphere

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NEUROimage 2006年第2期29卷 536-544页

作者： Lee, SS Dapretto, M Univ Calif Los Angeles Ahmanson Lovelace Brain Mapping Ctr Dept Psychiat & Biobehav Sci Los Angeles CA 90095 USA

The neural networks associated with processing metaphorical word meanings were investigated in normal adults using fMRI. Subjects listened to sets of three adjectives and decided whether the last two had a similar meaning. One condition required accessing the literal meaning of the middle word (e.g., hot-(cold) under bar-(chilly) under bar), whereas the other condition required accessing its nonliteral, or metaphorical, meaning (e.g., hot-(cold) under bar-(unfriendly) under bar. Direct comparison of the nonliteral vs. literal condition showed reliable activity only in left prefrontal and temporo-parietal regions. These results argue against a selective role of the right hemisphere (RH) in accessing metaphorical word meanings. In line with a growing literature, these findings suggest that prior reports of greater RH involvement for metaphorical language might reflect the increased complexity of figurative language rather than an RH specialization for understanding metaphors. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Adult Brain/physiology Female Functional Laterality/physiology Humans image processing, computer-assisted Magnetic Resonance Imaging Male Nerve Net/physiology Perception/physiology Psycholinguistics Psychomotor Performance/physiology Reaction Time/physiology

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Neuroanatomical differences between mouse strains as shown by high-resolution 3D MRI

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NEUROimage 2006年第1期29卷 99-105页

作者： Chen, XJ Kovacevic, N Lobaugh, NJ Sled, JG Henkelman, RM Henderson, JT Hosp Sick Children Mouse Imaging Ctr Dept Med Biophys Toronto ON M5G 1X8 Canada Univ Toronto Sunnybrook & Womens Coll Hlth Sci Ctr Imaging Res Cognit Neurol Toronto ON Canada Univ Toronto Leslie Dan Fac Pharm Dept Pharmaceut Sci Toronto ON Canada

The search for new mouse models of human disease requires a sensitive metric to make three-dimensional (3D) anatomical comparisons in a rapid and quantifiable manner. This is especially true in the brain, where changes in complex shapes such as the hippocampus and ventricles are difficult to assess with 2D histology. Here, we report that the 3D neuroanatomy of three strains of mice (129S1/ SvImJ, C57/B16, and CD1) is significantly different from one another. Using image co-registration, we `morphed' together nine brains of each strain scanned by magnetic resonance imaging at (60 mu m)(3) resolution to synthesize an average image. We applied three methods of comparison. First, we used visual inspection and graphically examined the standard deviation of the variability in each strain. Second, we annotated 42 neural structures and compared their volumes across the strains. Third, we assessed significant local deviations in volume and displacement between the two inbred strains, independent of prior anatomical knowledge. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Algorithms Animals Brain Mapping Brain Mapping image processing, computer-assisted Least-Squares Analysis Magnetic Resonance Imaging Mice Mice, Inbred C57BL Mice, Inbred Strains/anatomy & histology Species Specificity Terminology as Topic

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In vivo flow territory mapping of major brain feeding arteries

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NEUROimage 2006年第1期29卷 136-144页

作者： van Laar, PJ Hendrikse, J Golay, X Lu, HZ van Osch, MJP van der Grond, J Univ Utrecht Ctr Med Dept Radiol NL-3508 GA Utrecht Netherlands Natl Inst Neurosci Dept Neuroradiol Singapore Singapore NYU Dept Radiol New York NY 10003 USA Leiden Univ Ctr Med Dept Radiol Leiden Netherlands

The ability to visualize the perfusion territories of major feeding arteries to the brain is important for many clinical applications. Since the work of Duret in 1874 on vascularization of the brain, many textbooks and atlases have shown schematic drawings of the supply areas of the major cerebral arteries. Recent postmortem studies demonstrated that the variability of the cerebral vascular territories is significantly greater than previously assumed. The aim of the present study was to investigate in vivo, the variability of flow territories of major brain feeding arteries. Flow territory mapping of the anterior (internal carotid arteries) and posterior (basilar artery) circulation was performed in 115 (58 +/- 9 years of age) subjects with selective arterial spin labeling MRI. Flow territory maps for the entire population indicated significant variation in flow territories. However, when the subjects are further categorized into groups with a complete circle of Willis, with a missing A1 segment and with a unilateral or bilateral fetal-type posterior cerebral artery, the results showed considerably lower variation within groups. It is therefore concluded that, the variation observed from the entire population is mainly caused by anatomical variants of the circle of Willis. To relate focal brain lesions to underlying flow territories in individual cases, knowledge of the anatomy of the circle of Willis is essential. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Aged Brain Mapping Brain Mapping Carotid Artery, Internal/physiology Cerebral Arteries/anatomy & histology Cerebral Arteries/physiology Cerebrovascular Circulation/physiology Circle of Willis/anatomy & histology Circle of Willis/physiology Data Interpretation, Statistical Female Humans image processing, computer-assisted Magnetic Resonance Imaging Male Middle Aged

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NEUROimage 2006年第1期31卷 255-263页

作者： Gaab, Nadine Gaser, Christian Schlaug, Gottfried Beth Israel Deaconess Med Ctr Dept Neurol Neuroimaging Lab Boston MA 02215 USA Harvard Univ Sch Med Boston MA 02115 USA Univ Jena Dept Psychiat D-07740 Jena Germany

Functional activation patterns of an auditory working memory task were examined prior to and after 5 days of training (1 h/day). A control group with no training was scanned twice at the same intervals to assess test-retest effects. Based on behavioral improvement scores, the training group (n = 14) was divided into "Strong-Learners (SL)" and "Weak-Learners (WL)". No significant functional or structural brain differences were seen between the SL and WL groups prior to training. Imaging contrasts comparing post- with pre-training sessions showed a significant signal increase in the left Heschl's gyrus (HG) as well as in the left posterior superior temporal and supramarginal gyrus for the SL group, while the WL group showed significant signal increases in the left HG and anterior insular cortex as well as in a lingual-orbitofrontal-parahippocampal network. The test-retest analysis in the control group revealed only minimal signal increases in a right dorsolateral prefrontal region. A random effects analysis comparing the SL group with the WL group using the post- and pre-training contrast images showed increased activation only in the left supramarginal gyros but not in HG. The importance of HG in pitch discrimination has been established in previous studies. The pitch memory component differentiated our task from a straight pitch discrimination task. It is most likely that the activation of the SMG reflects its importance in the short-term storage of auditory material, and it was this activation that best differentiated between subjects' levels of performance. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Adult Attention/physiology Brain/physiology Brain Mapping Brain Mapping Cerebellum/physiology Cerebral Cortex/physiology Dominance, Cerebral/physiology Female Humans image processing, computer-assisted Imaging, Three-Dimensional Individuality Magnetic Resonance Imaging Male Memory, Short-Term/physiology Neural Pathways/physiology Neuronal Plasticity/physiology Pitch Discrimination/physiology Practice (Psychology) Reference Values Serial Learning/physiology

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Magnetic resonance imaging of functional Schwann cell transplants labelled with magnetic microspheres

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NEUROimage 2006年第1期31卷 172-180页

作者： Dunning, Mark D. Kettunen, Mikko I. Constant, Charles Ffrench Franklin, Robin J. M. Brindle, Kevin M. Univ Cambridge Dept Vet Med Cambridge CB3 0ES England Univ Cambridge Cambridge Ctr Brain Repair Cambridge CB2 2PY England Univ Cambridge Dept Biochem Cambridge CB2 1QW England Univ Cambridge Dept Pathol Cambridge CB2 1QP England

There is increasing interest in the use of magnetic resonance imaging (MRI) methods for tracking the fate of labelled cells in vivo post-implantation. The majority of studies have employed cell labels based on nanometer-sized ultrasmall dextran-coated iron oxide. particles (USPIO), which are detected through signal hypointensity in T-2-weighted images. Although sensitive to MR detection, these labels can be difficult to distinguish from other sources of signal loss in vivo and can be diluted by cell division. Recently, a micron-sized cell label has been described that is much more sensitive to MR detection and which allows detection of single labels in vivo. We show here that glial cells readily take up this label in culture and that the labelled Schwann cells can be detected in vivo by MRI following their implantation into a demyelinated lesion in the rat spinal cord. Signal loss due to the label is sufficiently great that the labelled cells can easily be distinguished from surrounding haemorrhage at the lesion site. Subsequent histological analysis of the lesion area showed that the transplanted cells were remyelinating the demyelinated axons, demonstrating that the labelled cells retained their biological function and that the majority of the label had remained within the transplanted cells. (c) 2005 Elsevier Inc. All rights reserved.

关键词： Animals Animals, Newborn Axons/pathology Cell Survival/physiology Cells, Cultured Contrast Media Contrast Media image processing, computer-assisted Imaging, Three-Dimensional Iron/diagnostic use Magnetic Resonance Imaging Magnetics Microscopy, Electron Microspheres Myelin Sheath/pathology Neuroglia/pathology Neuroglia/transplantation Oxides/diagnostic use Radiation Injuries, Experimental/pathology Radiation Injuries, Experimental/pathology Radiation Injuries, Experimental/surgery Radiation Injuries, Experimental/surgery Rats Rats, Inbred F344 Schwann Cells/pathology Schwann Cells/transplantation Sensitivity and Specificity Spinal Cord/pathology Spinal Cord/radiation effects Spinal Cord/surgery

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