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PubMed2004

Brain mappings of the arithmetic processing in children and adults.

Despite the increasing number of experimental mapping showing that human arithmetic cognition is supported by widely spread neural circuits; the theoretical reasoning about these data remains mostly metaphorical and guided by a connectionist approach. Although neurons at distinct areas in the brain are assumed to take charge of different duties in the solution of the experimental task, the results are always discussed by hypothesizing some association between the different areas without questioning any difference of behavior at the level of the neurons at each of these areas. Here, the brain is assumed as Distributed Intelligent Processing System (DIPS) formed by collections of loosely interacting specialized agents (neurons), each agent specializing, for example, in data collection (sensors), problem solving (associative neurons), data communication (interneuronal systems) and in acting upon the surrounding environment (motorneurons). A new technique for EEG brain mapping is proposed and used to study arithmetic cognition in elementary school aged children and adults. Factor analysis showed three distinct patterns of neuronal recruitment for arithmetic calculations in all experimental groups which varied according to the type of calculation, age and sex.

Adult↗
PubMed1984

A noninvasive approach to quantitative functional brain mapping with H2 (15)O and positron emission tomography.

Positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) with intravenously administered 15O-labeled water and an adaptation of the Kety autoradiographic model are well suited to the study of functional-anatomical correlations within the human brain. This model requires arterial blood sampling to determine rCBF from the regional tissue radiotracer concentration (Cr) recorded by the tomograph. Based upon the well-defined, nearly linear relation between Cr and rCBF inherent in the model, we have developed a method for estimating changes in rCBF from changes in Cr without calculating true rCBF and thus without arterial sampling. This study demonstrates that quantitative functional brain mapping does not require the determination of rCBF from Cr when regional neuronal activation is expressed as the change in rCBF from an initial, resting-state measurement. Patterned-flash visual stimulation was used to produce a wide range of increases in rCBF within the striate cortex. Changes in occipital rCBF were found to be accurately estimated directly from Cr over a series of 56 measurements on eight subjects. This adaptation of the PET/autoradiographic method serves to simplify its application and to make it more acceptable to the subject.

Adult↗
PubMed2001

Using (10)CO2 for single subject characterization of the stimulus frequency dependence in visual cortex: a novel positron emission tomography tracer for human brain mapping.

Carbon-10-labeled carbon dioxide ((10)CO2) with a half-life of 19.3 seconds offers almost ideal characteristics as a positron emission tomography (PET) tracer for assessment of the regional cerebral blood flow (rCBF) distribution, enabling multiple independent measurements at short intervals. To appraise the feasibility of (10)CO2 for localizing and characterizing human brain function in single subjects, the authors chose a well-characterized activation paradigm. In 6 healthy volunteers, 50 to 64 independent PET scans of the rCBF distribution were acquired while viewing an annular reversing checkerboard presented at 10 reversal frequencies between 0.03 and 30 Hz. Changes in regional cerebral activity as a function of reversal frequency were modeled in every subject using a set of polynomial basis functions, which, as predicted, showed highly significant second or third order relations located in the striatal cortex. Correlation coefficients (R2) ranged from 0.46 to 0.63. The average intersubject maximal response relative to the 0.03 Hz condition was 8.0% +/- 1.7% SD occurring at stimulus contrast reversal frequencies between 6 and 15 Hz with an average of 11.8 +/- 3.8 (SD) Hz. From the qualitative and quantitative replication of previous results it is concluded that (10)CO2 PET is a feasible technique for human brain mapping studies and a great improvement compared with the existing oxygen-15-labeled water (H(2)(15)O) PET method, particularly for single subject studies and parametric design.

Brain Mapping↗
PubMed1988

Comparative bioavailability studies with a new mixed-micelles solution of diazepam utilizing radioreceptor assay, psychometry and EEG brain mapping.

In a double-blind, placebo-controlled study the pharmacokinetic and pharmacodynamic properties of a standard solution of diazepam (DZ) (ValiumR) were compared with those of a novel diazepam mixed-micelles solution (DZ MM) (Valium MMR) both after i.v. and i.m. application utilizing radioreceptor assay, quantitative pharmaco-EEG and brain mapping techniques as well as psychometric and psychophysiological methods. The local tolerance was studied as well. The subjects received randomized and, in weekly intervals, following injections: (1) 10 mg DZ i.v. + placebo i.m.; (2) 10 mg DZ MM i.v. + placebo i.m.; (3) placebo i.v. + 10 mg DZ i.m.; (4) placebo i.v. + 10 mg DZ MM i.m.; (5) placebo i.v. + placebo i.m. Blood sampling, EEG-recordings, psychometric and psychophysiological tests as well as tolerance evaluations were carried out at 0, 1/2, 1, 2, 4, 6 and 8 h. Blood level evaluation demonstrated after i.m. application a significantly shortened tmax, a higher Cmax and generally higher plasma concentrations in the first and second hour following the mixed-micelles solution than the standard formulation, which suggests better absorption of the former than the latter in the muscle. Subsequent to i.v. administration, lower blood levels were observed between 30 min and 2 h after DZ MM than DZ. Power spectral density analysis of the EEG resulted in typical anxiolytic-sedative pharmaco-EEG profiles after all 4 active substances as compared with placebo. However, there were significant inter-drug differences as far as topographic aspects (pharmaco-EEG maps) were concerned. DZ MM i.v. induced significantly more initial but also late delta augmentation, alpha attenuation and centroid slowing than DZ i.v. which suggests more sedative effects at those times. Following i.m. application, a significantly more pronounced delta/theta attenuation, beta augmentation and centroid acceleration after DZ MM than DZ suggested more anxiolytic effects of the novel than the standard formulation. Discriminant analysis of changes in 6 thymopsychic, 12 noopsychic and 17 psychophysiological variables demonstrated the best discrimination of the 4 substances based on thymopsychic effects. Considering the latter, all 4 active compounds differed significantly from placebo, with no inter-drug differences after i.v. application but a marked superiority of the novel mixed-micelles solution over the standard solution after i.m. application. Specifically, DZ MM i.m. induced more desactivation and affect-attenuation than DZ i.m.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

EEG brain mapping in evaluating the time-course of the central action of DUP 996--a new acetylcholine releasing drug.

1. In a double-blind, placebo-controlled study the encephalotropic effects of DUP 996, a novel phenylindolinone derivative for Alzheimer's disease enhancing the release of acetylcholine in cholinergic nerve terminals in the brain only when its release is triggered, were studied with special consideration of the pharmacodynamic time-course. 2. Thirteen healthy male volunteers aged 18-40 years received randomized and at weekly intervals, single oral doses of placebo and 30 mg DUP 996. Blood sampling for plasma concentration analysis, EEG recordings and evaluation of pulse, blood pressure and side effects were carried out at 0, 1, 2, 4, 8, 12 and 24 h. 3. Computer-assisted spectral analysis of the EEG and subsequent topographic brain mapping of the drug-induced EEG changes demonstrated significant central effects of DUP 996 suggesting vigilance-improving properties. The findings were characterized mostly by an augmentation of total power as well as by an increase of absolute power in the alpha and alpha-adjacent beta activity. 4. Time-course investigations demonstrated two pharmacodynamic peaks: a first one in the 2nd h and a second one in the 12th h. In detail CNS effects increased up to the 2nd h, showed a drop in the 4th h, increased again thereafter to peak in the 12th h. Even in the 24th h there were significant differences between DUP 996 and placebo. The latter suggests an indirect effect and/or an active metabolite, as the parent drug is rapidly absorbed and has a rather short plasma half-life between 1-3 h. 5. DUP 996-induced EEG-changes over time were most pronounced over temporo-occipital, temporo-frontal, parietal and frontal regions, e.g. over brain areas afflicted most by Alzheimer's disease. 6. Evaluation of vital signs, laboratory findings and ECG as well as adverse effects showed a very good tolerability of DUP 996.

Acetylcholine↗
PubMed1993

Functional brain mapping by blood oxygenation level-dependent contrast magnetic resonance imaging. A comparison of signal characteristics with a biophysical model.

It recently has been demonstrated that magnetic resonance imaging can be used to map changes in brain hemodynamics produced by human mental operations. One method under development relies on blood oxygenation level-dependent (BOLD) contrast: a change in the signal strength of brain water protons produced by the paramagnetic effects of venous blood deoxyhemoglobin. Here we discuss the basic quantitative features of the observed BOLD-based signal changes, including the signal amplitude and its magnetic field dependence and dynamic effects such as a pronounced oscillatory pattern that is induced in the signal from primary visual cortex during photic stimulation experiments. The observed features are compared with the results of Monte Carlo simulations of water proton intravoxel phase dispersion produced by local field gradients generated by paramagnetic deoxyhemoglobin in nearby venous blood vessels. The simulations suggest that the effect of water molecule diffusion is strong for the case of blood capillaries, but, for larger venous blood vessels, water diffusion is not an important determinant of deoxyhemoglobin-induced signal dephasing. We provide an expression for the apparent in-plane relaxation rate constant (R2*) in terms of the main magnetic field strength, the degree of the oxygenation of the venous blood, the venous blood volume fraction in the tissue, and the size of the blood vessel.

Biophysical Phenomena↗
PubMed1997

Magnetic source imaging as a tool for presurgical functional brain mapping.

This article describes magnetic source imaging, a newly-developing technology which can be used to noninvasively map eloquent cortex prior to surgical procedures. It is based on large-array detection of extracranial magnetic fields arising from neuronal currents evoked by peripheral stimulation. A range of evoked and spontaneous neuromagnetic activities are discussed along with clinical examples of the utility of the technique and comparison to other brain mapping techniques, such as positron emission tomography, functional magnetic resonance imaging, EEG, and ECoG.

Adolescent↗
PubMed2003

Functional brain mapping in freely moving rats during treadmill walking.

A dilemma in functional neuroimaging is that immobilization of the subject, necessary to avoid movement artifact, extinguishes all but the simplest behaviors. Recently, we developed an implantable microbolus infusion pump (MIP) that allows bolus injection of radiotracers by remote activation in freely moving, nontethered animals. The MIP is examined as a tool for brain mapping in rats during a locomotor task. Cerebral blood flow-related tissue radioactivity (CBF-TR) was measured using [14C]-iodoantipyrine with an indicator-fractionation method, followed by autoradiography. Rats exposed to walking on a treadmill, compared to quiescent controls, showed increases in CBF-TR in motor circuits (primary motor cortex, dorsolateral striatum, ventrolateral thalamus, midline cerebellum, copula pyramis, paramedian lobule), in primary somatosensory cortex mapping the forelimbs, hindlimbs and trunk, as well as in secondary visual cortex. These results support the use of implantable pumps as adjunct tools for functional neuroimaging of behaviors that cannot be elicited in restrained or tethered animals.

Animals↗