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At least 361 records · Page 20Linked to original sources
PubMed2003

Functional near-infrared optical imaging: utility and limitations in human brain mapping.

Although near-infrared spectroscopy (NIRS) was developed as a tool for clinical monitoring of tissue oxygenation, it also has potential for neuroimaging. A wide range of different NIRS instruments have been developed, and instruments for continuous intensity measurements with fixed spacing [continuous wave (CW)-type instruments], which are most readily available commercially, allow us to see dynamic changes in regional cerebral blood flow in real time. However, quantification, which is necessary for imaging of brain functions, is impossible with these CW-type instruments. Over the past 20 years, many different approaches to quantification have been tried, and several multichannel time-resolved and frequency-domain instruments are now in common use for imaging. Although there are still many problems with this technique, such as incomplete knowledge of how light propagates through the head, NIRS will not only open a window on brain physiology for subjects who have rarely been examined until now, but also provide a new direction for functional mapping studies.

Algorithms↗
PubMed1987

Carbonic anhydrase-II messenger RNA in neurons and glia of chick brain: mapping by in situ hybridization.

The enzyme carbonic anhydrase is widespread in brain tissue. In rodent brains it has been reported to be exclusively in oligodendroglia but there has been some debate about the generality of this finding. To investigate the cellular distribution of carbonic anhydrase by an independent technique, we have examined the chick brain by in situ hybridization to detect mRNA from the carbonic anhydrase-II gene, using as controls the actin and vimentin genes. The most intense carbonic anhydrase-II hybridization is to the choroid plexus, to the Bergmann glia of the cerebellum, and to the Müller cells in the retina. Elsewhere, some brain regions are negative while others show many individual strongly positive cells; carbonic anhydrase-II mRNA is particularly abundant in some parts of the hyperstriatum, tectum and thalamus. Some of the larger labelled cells are identifiable as neurons. By histochemistry, we confirm the presence of the carbonic anhydrase enzyme in choroid plexus and Bergmann glia, but the enzyme is also present in blood vessel walls where there is no carbonic anhydrase-II mRNA; this may be a different isozyme. During embryogenesis, carbonic anhydrase-II mRNA appears in the retina as early as two days of incubation, but does not appear in the brain until much later.

Animals↗
PubMed2003

Functional magnetic resonance imaging for brain mapping in neurosurgery.

One of the most pertinent applications of the principle primum non nocere (first do no harm) is in the optimization of neurosurgical procedures for patients with resectable lesions. The gold standard for identifying eloquent areas of the brain to be avoided in resections is direct cortical stimulation and somatosensory evoked potential monitoring, which is itself an invasive, cumbersome and difficult technique for mapping these areas. Functional magnetic resonance imaging shows great promise as a viable noninvasive alternative to invasive mapping as well as significant current clinical utility in cases in which it cannot yet fully supplant cortical stimulation methods. Ongoing work is directed toward overcoming technical limitations, improved mapping of complex functions such as language and memory, and mapping of white matter tracts.

Brain Diseases↗
PubMed1993

Brain mapping in thinking and language function.

Regional cerebral blood flow, rCBF, is coupled to regional cerebral metabolism and changes in rCBF reflects changes in neuronal activity. rCBF studies have provided information about the functions of a great number of cortical regions in the normal human brain. Outside the motor areas and sensory association areas there are areas committed to the transformation of information retrieved or generated within the brain itself. Language is processed within these regions. In contrast to the general clinical impression the functional mapping methods reveal that there is a large number of cortical regions activated bilaterally during language processing. Pure intrinsic brain work causes a profound activation of the cerebral cortex. Different types of thinking are seen to activate different sectors of the cortical space.

Brain↗
PubMedDate not supplied

Topographical variation of the human primary cortices: implications for neuroimaging, brain mapping, and neurobiology.

The relationships of the "primary" cytoarchitectonic neocortical fields, 17, 41, 3b, and 4 (Brodmann areas), to salient topographic landmarks have been reconstructed from serial histological sections in 20 human cerebral hemispheres (10 brains). Each of these architectonic fields is found to bear a characteristic relationship to a set of enframing anatomic landmarks, in particular, gyri, fissures, and sulci, that can be readily defined by MRI. Two classes of variability were found characteristic, at least to some extent, of each of the fields. Class 1 variability--variability that is not predictable from visible landmarks--was typical of the polar and for the cuneal and lingual extracalcarine distributions of field 17 and the distribution of field 4 upon the paracentral lobule. Class 2 variability--variability that is closely predictable from visible landmarks--is seen in the marked interindividual or interhemispheric variation in size or shape of a field and was found to be prominent for all four fields. Because of the prominence of class 2 variability, direct reference to the landmarks that frame these fields may be expected to be a more reliable basis for functional mapping than reference to a template or stereotactic coordinate-based system of reference to a standard or idealized brain.

Adolescent↗
PubMed1986

Rapid proteolysis of brain MAP-1 related cytoskeleton-associated 350kd protein by purified calpain.

Microtubule associated protein-1 of brain and its intracellular 350kd analogues were highly sensitive to purified Ca2+-dependent cysteine proteinase (calpain). After 15 second digestion, we detected intermediate degradation products of MAP-1 by immunoblotting using anti-MAP-1 antibody as 290, 260, 220, 170, 140, 112, 80, 68, and 32kd polypeptides. These values corresponded to the molecular weights of the immunoreactive polypeptides of microtubule-enriched cytoskeletons isolated from HeLa and SV-3Y1 cells, suggesting the action of endogenous calpain on intracellular MAP-1 analogues in vivo or during the course of preparation.

Animals↗
PubMed1997

Quantitation of dopamine transporter mRNA in the rat brain: mapping, effects of "binge" cocaine administration and withdrawal.

Dopamine transporter (DAT) mRNA from selected brain regions of individual male Fischer rats was quantitated utilizing a sensitive solution hybridization assay in which the levels of RNase-protected 32P-labeled mRNA:cRNA hybrids were measured. DAT mRNA was detected in whole brain regions known to contain abundant DAT mRNA (mean picogram of DAT mRNA/microgram of total RNA +/- SEM): substantia nigra, 7.17 +/- 0.47; ventral tegmentum, 4.71 +/- 0.38. In regions known to contain low levels of DAT mRNA, these levels were detected: central grey, 0.39 +/- 0.06; hypothalamus, 0.14 +/- 0.03. In addition, DAT mRNA was detected in areas where it had not previously been identified: amygdala, 0.19 +/- 0.03; caudate-putamen, 0.15 +/- 0.03; nucleus accumbens, 0.13 +/- 0.01; pons/medulla, 0.12 +/- 0.02; globus pallidus, 0.09 +/- 0.04; pituitary 0.07 +/- 0.01; frontal cortex, 0.05 +/- 0.01. No DAT mRNA was detected in 150 micrograms of rat liver RNA. As cocaine binds to and inhibits the activity of the dopamine transporter, we sought to determine if there were differences in dopamine transporter mRNA levels between saline- and cocaine-injected rats or rats withdrawn from a chronic "binge" pattern (15 mg/kg per dose i.p.; three doses at 1 h intervals each day) cocaine injection. Using trichloroacetic acid precipitation of mRNA:cRNA hybrids from RNA extracted from whole brain regions, we found no significant differences in the substantia nigra or the ventral tegmentum following subacute (3 days) binge, chronic (14 days) binge or 10 days withdrawal from a chronic binge pattern cocaine or saline administration.

Animals↗
PubMed1999

Mapping brain metabolites using a double echo-filter metabolite imaging (DEFMI) technique.

A double echo-filter metabolite imaging (DEFMI) technique was developed for spatial mapping of low-concentration metabolites in the human brain. This imaging technique simultaneously acquires two images from two individual metabolites, respectively, using conventional imaging acquisition. It provides (i) efficient water and lipid suppressions, (ii) the capability of collecting high-resolution metabolite images within a short time and creating a ratio image from two interesting metabolites within a single experiment, and (iii) flexibility and simplicity for experimental setup and data processing. The technique was examined by both phantom and human brain experiments at 4 Tesla. The results reveal that the DEFMI technique is promising for applications in metabolism studies aimed at investigating physiological and pathological questions.

Aspartic Acid↗
PubMed2004

Standardized whole brain mapping of tubers and subependymal nodules in tuberous sclerosis complex.

Tuberous sclerosis complex is associated with radiologically visible abnormalities of brain structure, principally tubers and subependymal nodules. We reviewed the literature on neuroimaging of tubers and subependymal nodules and found qualitative evidence of bilateral, predominantly frontal distribution of tubers and bilateral, predominantly subcortical distribution of subependymal nodules in prior studies of pediatric samples. We studied 25 high-functioning adults with tuberous sclerosis complex and normal IQ, acquiring both dual spin-echo and fluid-attenuated inversion recovery magnetic resonance imaging sequences to optimize radiologic diagnosis of tubers and nodules. Individual lesion maps were then coregistered in a standard stereotactic space to facilitate construction of lesion density maps and estimation of lesion density in cortical and subcortical regions reliably defined by a parcellated template image. We found the highest frequency of tubers in frontal lobes and the highest density of tubers in parietal regions. There was significant regional variation in tuber density but no significant lateralization of frequently bilateral tubers. Nodules were located predominantly in the caudate nucleus and were not significantly lateralized. Tuber and nodule volumes were significantly positively correlated. Tuber volume was larger, on average, in patients with a lifetime history of epilepsy, but there was no correlation between IQ and these measures of lesion load. Contemporary image processing tools can be used to enhance quantitative, whole brain analysis of lesion load in patients with tuberous sclerosis complex.

Adolescent↗
PubMedDate not supplied

Brain MAP-2 phosphorylation is decreased following prenatal alcohol exposure in rats.

The effects of prenatal alcohol treatment on the development and in vitro phosphorylation of specific neuronal phosphoproteins isolated from the frontal cortex and hippocampus of rat brains were studied. In vitro phosphorylation of microtubule-associated protein-2 (MAP-2) was decreased in the frontal cortex but not the hippocampus of animals exposed prenatally to alcohol. Phosphorylation of additional phosphoproteins, including tau proteins, Synapsin I, and GAP-43, was not affected by prenatal alcohol exposure. Littermates of animals used for the phosphorylation assays showed impaired passive avoidance learning. These data demonstrate that the previously reported structural changes in the development of the cerebral cortex following prenatal alcohol exposure and behavioral deficits are accompanied by changes in the phosphorylation of the important cytoskeletal protein MAP-2.

Animals↗
PubMed1986

The significance of pharmacodynamic measurements in the assessment of bioavailability and bioequivalence of psychotropic drugs using CEEG and dynamic brain mapping.

There are a variety of problems in evaluating the bioavailability of psychotropic drugs. Psychotropics have many metabolites; there are discrepancies between peripheral plasma levels and therapeutic effects, and psychotropics must penetrate the blood-brain barrier to have an effect on their target organ. Therefore, "classical" pharmacokinetic evaluation may not be sufficient to determine the bioavailability and bioequivalence of these drugs. Additional and more precise information may be obtained by adding pharmacodynamic procedures to these evaluations. Quantitative pharmaco-EEG (QPEEG), which uses the computer-analyzed electroencephalogram (CEEG), may be the method of choice for determining the pharmacodynamic profiles of psychotropic drugs at the central nervous system (CNS) level. The difficulties in evaluating the bioavailability of psychotropics, as well as the results of several studies that confirm the significance of CEEG as a pharmacodynamic measure, are discussed.

Biological Availability↗
PubMed2002

Functional brain mapping of psychopathology.

In this paper, we consider the impact that the novel functional neuroimaging techniques may have upon psychiatric illness. Functional neuroimaging has rapidly developed as a powerful tool in cognitive neuroscience and, in recent years, has seen widespread application in psychiatry. Although such studies have produced evidence for abnormal patterns of brain response in association with some pathological conditions, the core pathophysiologies remain unresolved. Although imaging techniques provide an unprecedented opportunity for investigation of physiological function of the living human brain, there are fundamental questions and assumptions which remain to be addressed. In this review we examine these conceptual issues under three broad sections: (1) characterising the clinical population of interest, (2) defining appropriate levels of description of normal brain function, and (3) relating these models to pathophysiological conditions. Parallel advances in each of these questions will be required before imaging techniques can impact on clinical decisions in psychiatry.

Brain↗
PubMed1996

Self-assembly of the brain MAP-2 microtubule-binding region into polymeric structures resembling Alzheimer filaments.

The neuronal microtubule-associated protein known as MAP-2 has not been considered to be a subunit of paired helical filaments (PHFs) in neurofibrillary tangles seen in Alzheimer's Disease. We now describe the assembly of paired helical filament-like structures from MAP-2's 203-residue microtubule-binding region (MTBR). SDS gel electrophoresis and equilibrium ultracentrifugation suggest that a dimeric form, cross-linked by an interchain disulfide, is involved in polymerization. MAP-2 MTBR polymers bind thioflavin-S, a dye used to histochemically localize Alzheimer neurofibrillary tangles. Our finding that PHF-like structures assemble from a MAP-2 fragment raises new questions about MAP-2's role in the etiology of Alzheimer's Disease.

Alzheimer Disease↗
PubMed1988

Topographic EEG brain mapping during Yogic Flying.

Voluntary focal activity typically disrupts EEG alpha activity. This experiment tested the hypothesis that the alpha wave would not be disrupted during "Yogic Flying" (YF), a TM-Sidhi technique that produces movement of the body such as hopping, because the technique operates at a self-referral level in which attention remains in a settled, inwardly directed state. In 23 subjects YF was compared with voluntary jumping in the same subjects which mimicked the movements of YF. The percentage of relative power of alpha was significantly higher for YF in virtually all EEG derivations, supporting the hypothesis. The effect appeared to be of similar magnitude in all cortical areas.

Alpha Rhythm↗
PubMed1995

Brain mapping with functional MR imaging: comparison of gradient-echo--based exogenous and endogenous contrast techniques.

PURPOSE: To compare directly the two most widely used methods of functional magnetic resonance (MR) imaging--dynamic contrast material-enhanced MR imaging and blood oxygenation level-dependent (BOLD) MR imaging. MATERIALS AND METHODS: Five healthy volunteers underwent dynamic contrast-enhanced and BOLD MR imaging with a conventional 1.5-T MR unit during visual stimulation and a dark control state. BOLD studies were performed with a gradient-echo sequence, and dynamic MR imaging was performed with an echo-shifted gradient-echo sequence after intravenous administration of a bolus of gadopentetate dimeglumine. RESULTS: A significantly greater percentage signal change was found with dynamic MR imaging than with the BOLD technique. The extent of area activated was also significantly greater. CONCLUSION: With standard clinical imagers and these gradient-echo-based techniques, greater percentage activation and area of activation can be achieved with dynamic MR imaging than with BOLD MR imaging.

Brain↗
PubMed1991

Differences in the capacity of two herpes simplex virus isolates to spread from eye to brain map to 1610 base pairs of DNA found in the gene for DNA polymerase.

A intertypic recombinant, designated HSV-R(D1), had previously been generated from non-neuroinvasive HSV-2(186) and neuroinvasive HSV-1(17). Although the recombinant contained less than 2% of the HSV-1 genome, it retained the neuroinvasive phenotype. The nucleotide sequences responsible for the neuroinvasiveness of HSV-R(D1) were previously mapped to a 3.0 kb segment of DNA located within the DNA polymerase gene (mu 0.414 to 0.430) via marker rescue experiments. We have now sequenced this region and compared our results to the published nucleotide sequence of the HSV-1(17) and HSV-2(186) DNA polymerase genes. It was found that the 3.0 kb HSV-R(D1) DNA fragment consisted entirely of HSV-2(186) nucleotide sequences except for the presence of 1610 bp of HSV-1(17) DNA. The 1610 bp of HSV-1 DNA coded for a 536 amino acid (AA) region which were located between AA 254 and 790 of the DNA polymerase enzyme. Comparison of the 536 AA sequence of neuroinvasive HSV-1(17) with the homologous area of the non-neuroinvasive HSV-2(186) DNA polymerase indicated that the two polymerases differed at 56 AA positions. In addition, this area of the HSV-1(17) DNA polymerase was 5 AA acids shorter than the HSV-2(186) DNA polymerase. Specific amino acid changes that might account for the neuroinvasive phenotype of HSV-R(D1) are discussed.

Amino Acid Sequence↗