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Results for “Brain Mapping”

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At least 703 records · Page 39Linked to original sources

PubMed1994

Functional MR mapping of activated cortical areas.

Magnetic resonance imaging (MRI) has recently been demonstrated to be sensitive to changes in neuronal activity of cortical areas. We report our initial experiences with functional MR brain mapping at high spatial resolution using a conventional whole-body MR system. A total of 10 visual and motor cortex activation studies were carried out on 8 healthy volunteers. In each examination, a time course series of 15 strongly T2*-weighted FLASH images was measured from three adjacent slices. The image analysis revealed a subtle but highly significant signal increase in cortical layers of gray matter in primary and associative visual as well as sensorimotoric cortex regions during periods of excessive brain activity provoked by photic stimuli or motoric tasks, respectively. To correlate brain structure and brain function, the computed MR brain activation maps were directly superimposed on T1-weighted anatomic spin-echo images. With this advance into the area of functional neuroimaging, MRI is moving into an established domain of positron emission tomography (PET). We, therefore, discuss the advantages and limitations of the MR method in comparison to PET as far as this can be done at present.

Adult↗

PubMed2002

Language plasticity revealed by electroencephalogram mapping.

Reasoning is the result of the computations made by intelligent systems, for instance those in the brain. It is not an abstract concept because calculations performed by computations are very concrete transactions among the different central processing unit components. Entropy measurements are proposed here to disclose the plasticity of the cerebral processing associated with language comprehension in video game playing. It is also assumed that entropy may be evaluated from the correlation coefficients obtained for the game event-related activity calculated for the different electroencephalogram derivations in the 10/20 system. The brain mapping derived from these entropy measurements clearly demonstrates the reallocation of speech functions to right brain areas when the classic left language circuits are damaged during prenatal life.

Brain Damage, Chronic↗

PubMed1996

Activation PET scanning in pretreatment evaluation of patients with cerebral tumours or vascular lesions in or close to the sensorimotor cortex.

Treatment of tumours and vascular lesions in or close to eloquent cortex may inflict neurological deficits. Intra-operative mapping procedures have been used for many decades in efforts to minimize neurological sequelae. The possibility for non-invasive pre-operative brain mapping has emerged with the advent of positron emission tomography (PET). In this paper we report on 11 patients with a tumour or vascular lesion in or close to the sensorimotor (10 patients) or visual cortex (one patient). The patients were subjected to activation PET scanning by means of vibrotactile or visual stimulation. The results show that in most of the patients the important relation between the lesion and the sensorimotor cortex could be determined. The patient with a lesion in the occipital lobe had involvement of the entire visual cortex as judged by comparison with activated areas on the nonlesion side.

Adult↗

PubMed2004

Determining the hemispheric dominance of spatial attention: a comparison between fTCD and fMRI.

Human brain mapping allows the systematic assessment of interindividual differences in functional brain anatomy. Functional transcranial Doppler sonography (fTCD) is an imaging tool that allows for fast and mobile assessment of hemispheric lateralization of task-related brain activation. It is ideal to screen large cohorts of subjects. The goal of the present study was to investigate whether fTCD and functional magnetic resonance imaging (fMRI) determine hemispheric lateralization of brain activation related to visuospatial attention concordantly. Used together, fMRI and fTCD may then open up a wide range of potential applications in neuroscience. Fifteen subjects were examined both with fTCD and fMRI while they judged accuracy of line bisections (Landmark task). For fTCD, the maximal mean difference in stimulus-related relative cerebral blood flow velocity changes in the left and right middle cerebral arteries was assessed as the lateralization index LI(fTCD). For fMRI, two approaches were used to determine hemispheric dominance. First, we measured brain activity as the extent of the activated region, i.e., the number of activated voxels above a statistical threshold. Second, we calculated the magnitude of the fMRI signal change between the activation and the control task within a region of interest. Results of fTCD and fMRI were concordant in every single case. Therefore, scanning large cohorts with fTCD for hemispheric dominance during Landmark task will provide results consistent with fMRI. FMRI can then be used for in depth assessment of the specific patterns of activation.

Adult↗

PubMed1994

Brain atlases--a new research tool.

Conventional brain atlases are collections of micrographs or schematic drawings of brain sections from one or a few brains in which anatomical structures are identified, for example, nuclei, cortical areas and fibre tracts. Conventional brain maps have now been replaced with modern computer-based brain atlases. The structures in computerized atlases are deformable so as to fit the sizes and shapes of individual brains, and transform three-dimensional reconstructions or images of brains into a standard brain format. In order to make generalizations about localization of function and structure at both the macroscopical and microscopical level computerized brain atlases are needed. Computerized brain atlases are also used to compensate for the shrinkage and distortions during sectioning and embedding of post-mortem brains, to study structural-functional relationships in the human brain at both the macroscopical and microscopical level, and variations in gross morphology and microstructure of the human brain, and for establishing a three-dimensional human-brain database for all of the above and also for topographically defined data from the literature.

Animals↗

PubMed2006

Using proton magnetic resonance imaging and spectroscopy to understand brain "activation".

Upon stimulation, areas of the brain associated with specific cognitive processing tasks may undergo observable physiological changes, and measures of such changes have been used to create brain maps for visualization of stimulated areas in task-related brain "activation" studies. These perturbations usually continue throughout the period of the stimulating event, and then subside when the event is terminated. In this communication, we consider the nature and meaning of these task-related brain activations. Since stimulation usually results in an increase in the frequency of neuron depolarizations or "spikes", an energy expensive activity that requires ATP for restoration of ionic gradients, additional energy supplies must be rapidly deployed to the stimulated areas or rates of re-polarization could be decreased, and refractory periods between spikes increased. As a result, maximum spiking rates may be decreased and some frequency-encoded information lost. The energy available to brain cells to re-synthesize ATP from ADP is a function of levels of glucose and oxygen in blood, and their availability to stimulated neurons is a function of the rate at which focal blood supplies can be increased (hyperemia). In this review we explore how neurons transmit meaningful encoded information; how the integrity of that information is dependent on a continuous supply of energy, and how proton magnetic imaging and spectroscopy may aid in understanding the process. Finally, evidence is presented that the neuropeptide, N-acetylaspartylglutamate, is a neuronal astrocyte-vascular feedback signal that regulates activation induced focal hyperemic responses.

Animals↗

PubMed1994

Dynamic magnetic resonance imaging of the rat brain during forepaw stimulation.

A magnetic resonance (MR) imaging brain mapping method was used to localize an activated volume of brain tissue in chloralose-anesthetized rats during electrical stimulation of the forepaw. Physiologically-induced changes are characterized by alterations of the magnetic properties of blood as determined by the oxygenation state of hemoglobin. Stimulation of the left forepaw led to an increase in MR signal intensity of the contralateral frontal and parietal cortices, which corresponded to forelimb motor and somatosensory areas. The activation was contiguous in coronal planes between +5 and +2 mm anterior to the bregma, and its volume was calculated to be 20-30 mm3. Each activated region was revealed using a paired t-test statistical analysis method and the activated volume was calculated from regions exposed by thresholding at p < 0.005. Physiologically-induced fractional signal changes, delta S/S, in the motor and somatosensory areas were 0.06 +/- 0.04 and 0.17 +/- 0.06, respectively.

Animals↗

PubMed2004

Columnar resolution of blood volume and oximetry functional maps in the behaving monkey; implications for FMRI.

The ultimate goal of high-resolution functional brain mapping is single-condition (stimulus versus no-stimulus maps) rather than differential imaging (comparing two "stimulus maps"), because the appropriate ("orthogonal") stimuli are rarely available. This requires some component(s) of activity-dependent hemodynamic signals to closely colocalize with electrical activity, like the early increase in deoxyhemoglobin, shown previously to yield high-quality functional single-condition maps. Conversely, nonlocal vascular responses dominate in cerebral blood volume (CBV)-based single-condition maps. Differential CBV maps are largely restricted to the parenchyma, implying that part of the CBV response does colocalize with electrical activity at fine spatial scale. By removing surface vascular activation from optical imaging data, we document the existence of a capillary CBV response component, regulated at fine spatial scale and yielding single-condition maps exhibiting approximately 100 microm resolution. Blood volume and -flow based single-condition functional mapping at columnar level should thus be feasible, provided that the capillary response component is selectively imaged.

Animals↗

PubMed1985

Cultured neurons contain a variety of microtubule-associated proteins.

The non-tubulin proteins associated with microtubules (MAPs) in cultures of pure sympathetic neurons have been identified using a variety of biochemical and immunochemical methods. MAPs of cultured sympathetic neurons include proteins corresponding to brain MAP-1 (consisting of MAP-1a and MAP-1b species), MAP-2, MAP-3, tau, 4 proteins that range in molecular weight from 60,000 to 76,000, and proteins with molecular weights of 210,000, 130,000 and 32,000. Many of the MAPs are phosphorylated in situ. MAP-2 and tau of cultured sympathetic neurons differ from their counterparts of brain in electrophoretic mobility. The observed variety of MAPs in sympathetic neurons together with the differences in MAPs of brain and sympathetic neurons are discussed in terms of microtubule heterogeneity in the nervous system.

Alkaloids↗

PubMed2003

Distinct brain regions associated with syllable and phoneme.

The syllable and the phoneme are two important units in the phonological structure of speech sounds. In the brain mapping literature, it remains unsolved as to whether there are separate brain regions mediating the processing of syllables and phonemes. Using functional magnetic resonance imaging (fMRI), we investigated the neural substrate of these phonological units with Chinese subjects. Results revealed that the left middle frontal cortex contributes to syllabic processing, whereas the left inferior prefrontal gyri contributes to phonemic processing. This pattern of findings offers compelling evidence for distinct cortical areas relevant to the representation of syllables and phonemes.

Adult↗

PubMed2005

PASTA: pointwise assessment of streamline tractography attributes.

Diffusion tensor MRI tractography aims to reconstruct noninvasively the 3D trajectories of white matter fasciculi within the brain, providing neuroscientists and clinicians with a potentially useful tool for mapping brain architecture. While this technique is widely used to visualize white matter pathways, the associated uncertainty in fiber orientation and artifacts have, to date, not been visualized in conjunction with the trajectory data. In this work, the bootstrap method was used to determine the distributions of diffusion indices such as trace and anisotropy, together with the uncertainty in fiber orientation. A novel visualization scheme was developed to encode this information at each point along reconstructed trajectories. By integrating these schemes into a graphical user interface, a new tool which we call PASTA (Pointwise Assessment of Streamline Tractography Attributes) was created to facilitate identification of artifacts in tractography that would otherwise go undetected.

Brain Mapping↗

PubMed2003

Comparison of BOLD fMRI and MEG characteristics to vibrotactile stimulation.

The characteristics of blood oxygenation level-dependent (BOLD) fMRI and magnetoencephalographic (MEG) responses to vibrotactile stimuli in humans were studied and compared. The stimuli, presented with interstimulus intervals (ISIs) ranging from 1 to 5 s, yielded highly reproducible MEG responses, with current dipoles in the primary somatosensory (SI) cortex in all subjects. BOLD fMRI responses to similar stimuli showed substantial intrasubject variation in the activation sites around the SI cortex. BOLD responses were detected in all subjects in the secondary somatosensory (SII) cortices as well, with comparable BOLD response amplitudes to those in the SI cortex. Current dipoles, used to model the MEG signals, were stronger at longer ISIs than shorter ISIs. The BOLD response amplitudes did not show a similar dependence on ISI, but the activated brain area was larger when longer ISIs or longer stimuli were applied. Our results support the view that combined use of brain mapping methods provides complementary information and should be considered in functional brain examinations.

Adult↗

PubMed2001

Developmental dyslexia: an update on genes, brains, and environments.

The science of reading and developmental dyslexia has experienced spectacular advances during the last few years. Five aspects of this research are discussed in the article. (1) The holistic phenomenon of reading is complex. Many lower-level psychological processes (e.g., phonemic awareness, phonological decoding, ability to process stimuli rapidly and automatize this process, memory, ability to recognize words) contribute to a single act of reading. Conceptualizing the complex process of reading through its partly overlapping but partly independent components--which contribute to, but do not fully explain, the holistic process of reading--provides an excellent model for understanding complex hierarchies of higher mental functions. Those who master reading skills successfully and those who have difficulties doing so differ in a wide range of reading-related processes. The central deficit experienced by poor readers appears to be related to phonological processing (a complex hierarchy of functions related to processing phonemes), whereas characteristics of automatization processes seem to moderate the reading outcome for people whose phonological skills are weak. (2) There are new data addressing models of dyslexia in languages other than English. The most fascinating finding is that the model implicating phonological deficit as central to dyslexia, and the lack of ability to automatize as leading to troubled reading, appears to be universal, regardless of the specific language. However, there is an interaction effect between the characteristics of a particular language and the developmental model of dyslexia. In phonologically more difficult languages (e.g., English), the most pronounced weakness appears to occur in phonological processing, whereas in phonologically easier languages (e.g., German), the crucial role in the manifestation of dyslexia is played by the lack of the skills needed to achieve automatization. (3) There is abundant evidence that reading (i.e., any single act of reading as well as reading as a holistic process) is "cooked" by the brain. Although no unified brain map of reading has been developed, some specific areas of the brain have been implicated in different reading-related cognitive processes by different laboratories and on different samples. (4) Indisputable evidence has been accumulated suggesting the involvement of the genome in developmental dyslexia. As of now, specific regions of the genome have been identified as being intimately involved with a number of different reading-related processes. Today the field of developmental dyslexia is the only area of genetic studies of human abilities and disabilities in which linkages to the genome have been robustly replicated in independent laboratories. (5) Finally, evidence suggests that developmental dyslexia might be only one of the manifestations of a deep, underlying, anatomical syndrome. The comorbidity of developmental dyslexia with both internalizing and externalizing behavioral disturbances, as well as with other learning disabilities, underscores the need for wide-ranging cognitive and behavioral approaches in the remediation programs offered to dyslexic children.

Adolescent↗

PubMed2003

Temporal dynamics of linguistic processes are reorganized in aphasics' cortex: an EEG mapping study.

Brain lesions are known to elicit reorganization of function in representational cortex. Using linguistic function as an example, we show that (a) injury-related reorganization may also be observed in language-related cortex and (b) this reorganization not only appears in cortical space but also in the dynamic flow of activity. The present study investigated cortical reorganization in a group of 10 nonfluent aphasics who demonstrated partial recovery of linguistic functions. Compared with controls, linguistic functions were organized in an atypical manner, both in terms of spatial structures involved and in the time course of the linguistic processes, from word reading to late stages of word encoding in working memory. For this purpose, event-related potentials were recorded in a two-stimulus design comprising phonological and semantic tasks. Subjects were asked to judge whether two words, separated by a 2-s interval, rhymed (phonological task) or were semantically associated. During word reading of the phonological task, controls showed negativity/activation over occipital sites, whereas patients displayed negativity at left-medial orbitofrontal locations anterior to the common sites of lesion. During the subsequent 2-s interval associated with word encoding, the two groups showed a reversed pattern: significant left-right anterior asymmetry prevailed in controls, whereas lateralization was absent in patients. Aphasics displayed maximum positivity/inhibition over the left frontal regions, at the typical site of lesion. Compared with controls, patients exhibited significant disinhibition (decreased positivity) of right frontal areas and greater activation of left temporal sites. These results suggest that the concept of language plasticity should include, in addition to spatial aspects of linguistic reorganization, the reorganized temporal dynamics associated with recovery of impaired functions.

Adult↗

PubMed1994

Brain electrical activity mapping in childhood absence epilepsy.

BACKGROUND: Brain electrical activity mapping (BEAM) studies related to children with epileptic seizures have been rarely reported. The authors wished to search for BEAM values in children with epilepsy, to better understand the changes in the cerebral field distribution of epileptiform events. METHODS: Electroencephalographies (EEGs) of 19 Chinese children with childhood absence epilepsy (CAE), but with normal intelligence, were studied prospectively and consecutively. Among them, 11 were boys aged from 6-12 years; 8 girls aged from 6-13 years. EEGs were simultaneously recorded on the Concerto (32 channels), and on the EEG machine, according to standardized recommendations. Frequency or spectral analysis was measured in terms of Band power (uv2), RMS (uv) and InstVolt (uv). Maps were also displayed simultaneously as color in their topographic distriution, with four-picture maximum. RESULTS: In comparing the four bands of background activities in subjects with eyes closed and open, in the different subgroups, there were no significant differences between boys and girls, nor between the group with epileptiform discharge events (EDE) and the group without EDE, except for the beta band in subjects with eyes closed of the EDE group. There was a significant increase of band power in the group treated with valproic acid, and an increase over the F3 in beta band, Fp1, F4 in theta band, F3, F4, P4, 02 in delta band, but no significant increase was found in alpha band. EDE was also measured and mapped and showed bilateral symmetry with a mid-frontal maximum. Root mean square (RMS) measurements of epochs, from the beginning of EDE to the end of EDE, showed significant increases in voltage over the F8 area. CONCLUSIONS: BEAM can clearly show cerebral field distribution, but also can employ statistical tests to give significance to the analyzed data. Furthermore, BEAM may be helpful for localization of the epileptiform discharges in EEG.

Adolescent↗

PubMed1987

Binding of mammalian brain microtubule-associated proteins (MAPs) to insect ovarian microtubules.

In this study we have applied microtubule-associated proteins (MAPs) from mammalian brain to both native and reassembled insect ovarian microtubules. Such microtubules, which are normally smooth walled, become decorated with projections similar to those observed when mammalian brain MAPs are added back to assembling or assembled mammalian brain microtubules. The mammalian MAPs were also detected as components of insect microtubules when analyzed by polyacrylamide gel electrophoresis. Our observations suggest that mammalian brain MAPs have common binding sites on microtubules from two widely different sources and indicate the degree of evolutionary conservation of such sites.

Animals↗

PubMed1998

Topographic guidance labels in a sensory projection to the forebrain.

Visual connections to the mammalian forebrain are known to be patterned by neural activity, but it remains unknown whether the map topography of such higher sensory projections depends on axon guidance labels. Here, we show complementary expression and binding for the receptor EphA5 in mouse retina and its ligands ephrin-A2 and ephrin-A5 in multiple retinal targets, including the major forebrain target, the dorsal lateral geniculate nucleus (dLGN). These ligands can act in vitro as topographically specific repellents for mammalian retinal axons and are necessary for normal dLGN mapping in vivo. The results suggest a general and economic modular mechanism for brain mapping whereby a projecting field is mapped onto multiple targets by repeated use of the same labels. They also indicate the nature of a coordinate system for the mapping of sensory connections to the forebrain.

Aging↗

PubMed1990

Neurophysiological monitoring during astrocytoma surgery.

The technique of direct stimulation mapping of the cortex is used to identify regions of language representation in the dominant cerebral hemosphere and the Rolandic cortex in either hemisphere. The use of electrocorticography to remove epileptogenic zones in patients with difficult-to-control seizures is described. The article presents the authors' experience with brain mapping during glioma surgery to maximize the extent of tumor resection and minimize surgical morbidity.

Adult↗