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Results for “Brain Mapping”

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At least 577 records · Page 32Linked to original sources

PubMed2002

Analysis of a human brain transcriptome map.

BACKGROUND: Genome wide transcriptome maps can provide tools to identify candidate genes that are over-expressed or silenced in certain disease tissue and increase our understanding of the structure and organization of the genome. Expressed Sequence Tags (ESTs) from the public dbEST and proprietary Incyte LifeSeq databases were used to derive a transcript map in conjunction with the working draft assembly of the human genome sequence. RESULTS: Examination of ESTs derived from brain tissues (excluding brain tumor tissues) suggests that these genes are distributed on chromosomes in a non-random fashion. Some regions on the genome are dense with brain-enriched genes while some regions lack brain-enriched genes, suggesting a significant correlation between distribution of genes along the chromosome and tissue type. ESTs from brain tumor tissues have also been mapped to the human genome working draft. We reveal that some regions enriched in brain genes show a significant decrease in gene expression in brain tumors, and, conversely that some regions lacking in brain genes show an increased level of gene expression in brain tumors. CONCLUSIONS: This report demonstrates a novel approach for tissue specific transcriptome mapping using EST-based quantitative assessment.

Journal Article↗

PubMed2006

Cortical auditory systems: speech and other complex sounds.

The neural systems that mediate human perception of speech and other complex sounds are currently the focus of considerable research. Brain mapping studies have provided new insights into the cortical processing of complex sounds. Findings from three lines of brain mapping research--stroke-lesion, neuroimaging, and electrocortical mapping studies--are reviewed. Unresolved questions regarding the relative contributions of cortical and subcortical auditory processing and the existence of separate, functionally specialized, cortical auditory systems for processing speech and nonspeech sounds are discussed. An integrated approach is proposed for future research on the neural bases of complex sound processing.

Acoustics↗

PubMed1986

[Results of EEG mapping in brain tumors. Comparison with imaging methods].

Thirty-nine patients with brain tumors were studied with conventional and Q. EEG mapping (FFT) comparatively to CT-Scan. In 33 cases, Q. EEG provided a precise localization of the tumor site, based on slow waves. Furthermore there was a good correlation between CT-Scan and focal theta activity in 31 patients. Focal delta waves were more frequent in deep tumors involving white matter. In 11 of 13 superficial tumors, alpha rhythm was ipsilaterally located, whereas in deeper lesions, its activity was decreased on the tumor side. The putative mechanism of these results are discussed.

Alpha Rhythm↗

PubMed2000

Mapping clinically relevant plasticity after stroke.

After stroke, patients show a wide range in the degree of recovery. Recovery occurs on the basis of discrete physiologic events. Identifying and measuring these events will be useful for a better understanding of stroke recovery mechanisms. The most extensive experience mapping these events has been with positron emission tomography, functional magnetic resonance imaging, and transcranial magnetic stimulation. This article reviews brain mapping studies that have examined stroke recovery. Serial assessment of patients during recovery raises the need for control studies evaluating the effect of intra-subject variability over time. The clearest insights into the significance of bilateral activation during unilateral movements by the stroke-affected hand will come from studies that include bilateral electromyographic measurements. Most brain imaging studies have focused on patients with very good recovery; further study of patients with a wide range of outcomes is needed. The described brain mapping methods have complementary strengths. Insights into the biological basis of recovery may best be achieved when results are considered together. With the advent of treatments targeting stroke recovery, measurement of post-stroke restorative events may also have value as a surrogate end point in clinical trials.

Animals↗

PubMed1997

Topographic maps are fundamental to sensory processing.

In all mammals, much of the neocortex consists of orderly representations or maps of receptor surfaces that are typically topographic at a global level, while being modular at the local level. These representations appear to emerge in development as a result of a few interacting factors, and different aspects of brain maps may be developmentally linked. As a result, evolutionary selection for some map features may require other features that may not be adaptive. Yet, an overall adaptiveness of brain maps seems likely. Most notably, topographic representations permit interconnections between appropriate sets of neurons to be made in a highly efficient manner. Topographic maps provide an especially suitable substrate for the common spatiotemporal computations for neural circuits. Finally, aspects of perception suggest the functional importance of topographic maps.

Aging↗

PubMed1996

Three-dimensional statistical analysis of sulcal variability in the human brain.

Morphometric variance of the human brain is qualitatively observable in surface features of the cortex. Statistical analysis of sulcal geometry will facilitate multisubject atlasing, neurosurgical studies, and multimodality brain mapping applications. This investigation describes the variability in location and geometry of five sulci surveyed in each hemisphere of six postmortem human brains placed within the Talairach stereotaxic grid. The sulci were modeled as complex internal surfaces in the brain. Heterogeneous profiles of three-dimensional (3D) variation were quantified locally within individual sulci. Whole human heads, sectioned at 50 micrometer, were digitally photographed and high-resolution 3D data volumes were reconstructed. The parieto-occipital sulcus, the anterior and posterior rami of the calcarine sulcus, the cingulate and marginal sulci, and the supracallosal sulcus were delineated manually on sagittally resampled sections. Sulcal outlines were reparameterized for surface comparisons. Statistics of 3D variation for arbitrary points on each surface were calculated locally from the standardized individual data. Additional measures of surface area, extent in three dimensions, surface curvature, and fractal dimension were used to characterize variations in sulcal geometry. Paralimbic sulci exhibited a greater degree of anterior-posterior variability than vertical variability. Occipital sulci displayed the reverse trend. Both trends were consistent with developmental growth patterns. Points on the occipital sulci displayed a profile of variability highly correlated with their 3D distance from the posterior commissure. Surface curvature was greater for the arched paralimbic sulci than for those bounding occipital gyri in each hemisphere. On the other hand, fractal dimension measures were remarkably similar for all sulci examined, and no significant hemispheric asymmetries were found for any of the selected spatial and geometric parameters. Implications of cortical morphometric variability for multisubject comparisons and brain mapping applications are discussed.

Aged↗

PubMed1988

Benzodiazepine receptor sites in the human brain: autoradiographic mapping.

Receptor autoradiography was used to localize and quantify the distribution of benzodiazepine receptor sites in human post mortem materials using [3H]flunitrazepam. The distribution and density of these sites was analysed in the brains of 21 patients dying without reported neurological disease. The distribution of benzodiazepine receptors in the human brain was found to be comparable from case to case although differences in the density occurred among the brains examined. No influence of the post mortem delay, age, gender or pre mortem drug treatment on the distribution and densities was observed in our series. The highest densities of benzodiazepine receptors in human brain were localized in cortical and hippocampal areas, nucleus accumbens, amygdala and mammillary bodies. Intermediate densities were found in the basal ganglia and thalamic and hypothalamic nuclei. [3H]Flunitrazepam binding was low in the brainstem nuclei and very low in white matter. The triazolopyridazine Cl 218872, reported to differentiate between type I and type II benzodiazepine receptor sites, exhibited regional differences in affinity when used to block [3H]flunitrazepam binding. Benzodiazepine receptors in the cerebellar cortex were more sensitive to this compound than those in the dentate gyrus of the hippocampus and the tuberal nuclei of the hypothalamus. An enrichment in the concentration of type I benzodiazepine receptor Cl 218872-sensitive sites was observed in motor areas as compared to structures of the limbic system. The addition of GABA to the incubation medium resulted in an increase of [3H]flunitrazepam binding, suggesting the coupling of these sites to a GABAA receptor. The increase in binding was directly proportional to the density of benzodiazepine receptors but unrelated to the density of high-affinity GABAA sites. The distribution of benzodiazepine receptor sites in the human brain compares well with that previously described in the rat brain. The high densities of receptors localized in the limbic system and in the cortical areas suggest that the effects of benzodiazepines are mediated through an interaction with the sites we have visualized in these anatomical structures. Our results provide a detailed map of the distribution of benzodiazepine receptors and a basis for the understanding of pharmacological effects of these drugs in humans and for future studies of modifications of these receptors in neurological and neuropsychiatric conditions in humans.

Aged↗

PubMed2004

Mapping structural brain alterations in obsessive-compulsive disorder.

BACKGROUND: Recent technical developments have made it feasible to comprehensively assess brain anatomy in psychiatric populations. OBJECTIVE: To describe the structural brain alterations detected in the magnetic resonance images of a large series of patients with obsessive-compulsive disorder (OCD) using imaging procedures that allow the evaluation of volume changes throughout the brain. DESIGN: Case-control study. SETTING: Referral OCD unit in a tertiary hospital. PARTICIPANTS: A consecutive sample of 72 outpatients with OCD and 72 age- and sex-matched control subjects. INTERVENTIONS: Three-dimensional sequences were obtained in all participants. A statistical parametric mapping approach was used to delineate possible anatomical alterations in the entire brain. To preserve volumetric information, voxel values were modulated by the Jacobian determinants (volume change measurement) derived from spatial normalization. MAIN OUTCOME MEASURES: Voxelwise brain volumes. RESULTS: The brains of patients with OCD showed reduced gray matter volume in the medial frontal gyrus, the medial orbitofrontal cortex, and the left insulo-opercular region. A relative increase in gray matter volume was observed bilaterally in the ventral part of the putamen and in the anterior cerebellum. All these brain alterations were abnormally correlated in patients with OCD, and age statistically significantly contributed to the relative enlargement observed in the striatal areas. Disease severity, the nature of symptoms, and comorbidities were not related to the changes described. Nevertheless, patients with prominent aggressive obsessions and checking compulsions showed reduced amygdala volume in the right hemisphere. CONCLUSIONS: The pattern of anatomical features depicted by this voxelwise approach is consistent with data from functional studies. The reported anatomical maps identified the specific parts of the frontostriatal system that were altered in patients with OCD and detected changes in anatomically connected distant regions. These data further define the structural brain alterations in OCD and may contribute to constraining the prevailing biological models of this psychiatric process.

Adolescent↗

PubMed2003

Genome scale mapping of brain gene expression.

Two new approaches, voxelation and gene expression tomography (GET), permit multiplex acquisition of gene expression patterns in the brain. Both methods result in volumetric images of gene expression analogous to those produced in biomedical imaging systems. Voxelation employs analysis of spatially registered cubes from the brain, whereas GET entails analysis of parallel slices obtained by rotation about multiple axes. These methods have been used to investigate neurologic diseases and their models in both humans and mice. The results of these studies are discussed, as is the future of high-throughput gene expression mapping in the brain.

Animals↗

PubMed1989

Anatomical mapping of brain stimulation reward sites in the anterior hypothalamic area: special attention to the stria medullaris.

The boundaries and relative fiber density of the brain stimulation reward systems of the anterior hypothalamic area were mapped at the level of the stria medullaris using a dorsal-ventral moveable electrode. Three clusters of reward sites were observed. One cluster was just medial to the stria medullaris, a second larger cluster was within the boundaries of the myelinated fibers of the stria, and a third cluster was observed just lateral to the stria in the medial forebrain bundle. These data are consistent with the view that there exist at least two anatomically distinct brain stimulation reward pathways connecting the midbrain and forebrain: one in the medial forebrain bundle and a second in the dorsal diencephalic bundle.

Animals↗

PubMed2004

The RUMBA software: tools for neuroimaging data analysis.

The enormous scale and complexity of data sets in functional neuroimaging makes it crucial to have well-designed and flexible software for image processing, modeling, and statistical analysis. At present, researchers must choose between general purpose scientific computing environments (e.g., Splus and Matlab), and specialized human brain mapping packages that implement particular analysis strategies (e.g., AFNI, SPM, VoxBo, FSL or FIASCO). For the vast majority of users in Human Brain Mapping and Cognitive Neuroscience, general purpose computing environments provide an insufficient framework for a complex data-analysis regime. On the other hand, the operational particulars of more specialized neuroimaging analysis packages are difficult or impossible to modify and provide little transparency or flexibility to the user for approaches other than massively multiple comparisons based on inferential statistics derived from linear models. In order to address these problems, we have developed open-source software that allows a wide array of data analysis procedures. The RUMBA software includes programming tools that simplify the development of novel methods, and accommodates data in several standard image formats. A scripting interface, along with programming libraries, defines a number of useful analytic procedures, and provides an interface to data analysis procedures. The software also supports a graphical functional programming environment for implementing data analysis streams based on modular functional components. With these features, the RUMBA software provides researchers programmability, reusability, modular analysis tools, novel data analysis streams, and an analysis environment in which multiple approaches can be contrasted and compared. The RUMBA software retains the flexibility of general scientific computing environments while adding a framework in which both experts and novices can develop and adapt neuroimaging-specific analyses.

Algorithms↗

PubMed2001

T2 relaxation measurements in X-linked adrenoleukodystrophy performed using dual-echo fast fluid-attenuated inversion recovery MR imaging.

SUMMARY: The purpose of this study was to determine whether dual-echo fast fluid-attenuated inversion recovery MR imaging and corresponding T2 brain maps can show different zones in the affected white matter of patients with cerebral X-linked adrenoleukodystrophy. Ten male patients with cerebral X-linked adrenoleukodystrophy underwent imaging performed using dual-echo fast fluid-attenuated inversion recovery and dual-echo conventional spin-echo MR sequences. Corresponding T2 relaxation maps of the brain were generated. On the basis of dual-echo fast fluid-attenuated inversion recovery images and T2 maps, the affected white matter could be divided into two distinct zones in four patients with cerebral X-linked adrenoleukodystrophy.

Adolescent↗

PubMed1989

[Evaluation of the therapeutic effect of flumazenil in hepatic encephalopathy using cerebral cartography].

We investigated the therapeutic effect of flumanezil on acute and chronic hepatic encephalopathy in a group of cirrhotics; its efficacy was evaluated using clinical data and neurophysiologic examination, e.g. brain mapping. Flumazenil was not found to induce significant changes in the clinical status or in maps of the cerebral activity of patients with chronic encephalopathy. In acute encephalopathy, flumazenil improved clinical status, as was confirmed neurophysiologically by improved cerebral activity on brain mapping.

Acute Disease↗

PubMed1999

Spatial and temporal distribution enhancement of movement-related brain macropotentials.

Conventional brain maps suffer from severe limitations due to both the spatial blur of potential distributions and the dependence on electrical reference. The surface Laplacian (SL) has been used to deblur movement-related brain macropotentials (MRBM) since it acts as a high-pass spatial filter that reduces the head volume conductor effects. Moreover, the method usually employed to improve the signal-to-noise ratio (SNR) is the well-known synchronized average. However, this method is no longer valid when the object of the study is the sweep-by-sweep variability. In this case, the SNR of original and Laplacian-transformed single-sweep MRBM can be improved by autoregressive with exogenous input (ARX) filtering. In our study, isolated or combined ARX and SL are applied to enhance the spatial distributions of single-sweep MRBM associated with unilateral voluntary self-paced finger movements in humans. It shows that single-sweep brain mappings are more coherent to physiological findings when ARX is first used followed by SL.

Algorithms↗

PubMed1995

Movement control. Moving the mental maps.

The brain's maps of the outside world must be shifted when the point of view changes. Recent experiments on cortical neurons imply that this is done by modulating a distributed population code for position.

Animals↗

PubMed1997

Fluctuations in the cerebral oxygenation state during the resting period in functional mapping studies of the human brain.

Functional mapping studies using near-infrared spectroscopy have detected for the first time the existence of significant fluctuations in the concentration of cerebral oxygenated [oxy-Hb], and deoxygenated haemoglobin, [deoxy-Hb], during the resting period. The fluctuations are not related to alterations in the systemic circulatory system. The temporal pattern varies with each brain region. In some instances, the degrees of change in [oxy-Hb] and [deoxy-Hb] caused by highly integrated tasks are within this resting variation range. Thus, taking account of these fluctuations is essential to the interpretation of distribution patterns of cerebral activity.

Adolescent↗

PubMed1999

Cortical intraoperative stimulation in brain tumors as a tool to evaluate spatial data from motor functional MRI.

RATIONALE AND OBJECTIVE: The purpose of this prospective, double-blind study was to correlate motor functional MRI (fMRI) with cortical brain mapping by intraoperative stimulation using 3D reconstructed images of the surface of the brain, and to validate the spatial data of fMRI in patients with brain tumors. METHODS: Fourteen patients with tumors of the rolandic region underwent functional MR mapping of the hand region and subsequently cortical mapping before tumor resection. Data obtained with fMRI and brain mapping were not known previously by the neurosurgeon and by the neuroradiologist, respectively (double-blind study). RESULTS: In each case, the results of direct cortical mapping matched those obtained with fMRI, both positively and negatively, although the extent of the functional activations was larger than the area required to elicit the corresponding movement during intraoperative brain mapping. CONCLUSION: fMRI can be used before surgery to assess motor functional area in patients with rolandic tumors. More studies are needed to validate during surgery the real extent of fMRI activations.

Adult↗

PubMed1998

An efficient method for correcting the edge artifact due to smoothing.

Spatial smoothing is a common pre-processing step in the analysis of functional brain imaging data. It can increase sensitivity to signals of specific shapes and sizes (Rosenfeld and Kak [1982]: Digital Picture Processing, vol. 2. Orlando, Fla.: Academic; Worsley et al. [1996]: Hum Brain Mapping 4:74-90). Also, some amount of spatial smoothness is required if methods from the theory of Gaussian random fields are to be used (Holmes [1994]: Statistical Issues in Functional Brain Mapping. PhD thesis, University of Glasgow). Smoothing is most often implemented as a convolution of the imaging data with a smoothing kernel, and convolution is most efficiently performed using the Convolution Theorem and the Fast Fourier Transform (Cooley and Tukey [1965]: Math Comput 19:297-301; Priestly [1981]: Spectral Analysis and Time Series. San Diego: Academic; Press et al. [1992]: Numerical Recipes in C: The Art of Scientific Computing, 2nd ed. Cambridge: Cambridge University Press). An undesirable side effect of smoothing is an artifact along the edges of the brain, where brain voxels become smoothed with non-brain voxels. This results in a dark rim which might be mistaken for hypoactivity. In this short methodological paper, we present a method for correcting functional brain images for the edge artifact due to smoothing, while retaining the use of the Convolution Theorem and the Fast Fourier Transform for efficient calculation of convolutions.

Artifacts↗