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PubMed1991

Topographic maps of brain electrical activity in primary degenerative dementia of the Alzheimer type and multiinfarct dementia.

The topography of the electroencephalographic (EEG) pattern of ten patients with primary degenerative dementia of the Alzheimer type, ten multiinfarct dementia patients, and ten age-matched controls was compared during three different behavioral conditions: resting condition with eyes open (EO), memorizing a list of words (M), and recalling the same list of words (R). Results indicate that the alpha frequency band does not show significant changes. On the other hand, the theta band could be considered an important factor in the differential diagnosis of the primary degenerative dementia of the Alzheimer type, showing a higher power over right posterior regions in this group of patients compared with the multiinfarct dementia patients under different behavioral conditions.

Aged↗
PubMed1990

Anatomical mapping of brain sites involved in the antinociceptive effects of ketoprofen.

Ketoprofen, a non-steroidal anti-inflammatory drug, has analgesic effects in animals and humans through a peripheral as well as a central action. This study was designed to determine which brain sites are involved in the central analgesic action of ketoprofen, by using the hot-plate test. Latencies to the first hindpaw lick were recorded in animals receiving local cerebral injections of ketoprofen (10 micrograms in 0.3 microliters) or a control solution (saline). Nineteen brain sites were tested. A significant analgesia was obtained in the 8 following sites: central gray, centro-medial nucleus of the thalamus, nucleus reuniens, dorso-lateral geniculate nucleus, medial geniculate nucleus, dorso-medial and ventro-medial nuclei of the hypothalamus, posterior hypothalamic nucleus and lateral vestibular nucleus. A slight analgesia, which did not reach significance, was observed in three structures: dorsal raphé, raphé magnus and ventral postero-medial thalamic nucleus. No analgesia was observed in other sites: centro-lateral nucleus of the thalamus, posterior thalamic nuclear group, parafascicular nucleus, bed nucleus of the stria terminalis, mesencephalic tegmentum, nucleus of the tractus solitarius, spinal trigeminal complex, and brainstem reticular formation. Therefore ketoprofen seems to be centrally active mostly at the level of several integrative and non-specific structures.

Animals↗
PubMed1995

Mapping cognitive brain function with modern high-resolution electroencephalography.

High temporal resolution is necessary to resolve the rapidly changing patterns of brain activity that underlie mental function. While electroencephalography (EEG) provides temporal resolution in the millisecond range, which would seem to make it an ideal complement to other imaging modalities, traditional EEG technology and practice provides insufficient spatial detail to identify relationships between brain electrical events and structures and functions that are visualized by magnetic resonance imaging (MRI) or positron emission tomography (PET). Recent advances overcome this problem by recording EEGs from more electrodes, by registering EEG data with anatomical information from each subject's MRI, and by correcting the distortion that is caused by volume conduction of EEG signals through the skull and scalp. Along with its ability to record how brains think when performing everyday activities in the real world, these advances make modern EEG an invaluable complement to other functional neuroimaging modalities.

Brain↗
PubMed1977

Concurrent mapping of brain sites for sensitivity to the direct application of morphine and focal electrical stimulation in the production of antinociception in the rat.

The effect of morphine microinjection (5 microgram/0.5 microliter) and focal electrical stimulation on the animal's response to radiant heat and noxious pinch was studied concurrently at 117 brain loci extending from the medial thalamus caudally to the periaqueductal gray area (PAG). Three populations of brain sites were discernible based on their responsiveness to focal electrical stimulation and morphine microinjection in the production of antinociception: (a) sites which support stimulation-produced analgesia (SPA, n = 24), (b) sites which were sensitive to the direct application of morphine (n = 8), (c) sites responsive to both manipulations (n = 8). With a few exceptions, all morphine sensitive sites were located within the anatomical boundaries of the PAG while sites supporting SPA were located not only within the PAG but also in the brain regions peripheral to this structure. Sites responsive to both manipulations were generally distributed throughout thf lateral aspect of the posteroventral PAG. Stimulation strength-effect curves for sites subserving SPA were also obtained. No differences were discovered between curves obtained from morphine-sensitive and -insensitive brain loci.

Analgesia↗
PubMed2005

Mapping of brain networks involved in consolidation of lamb recognition memory.

In sheep, ewes at parturition are responsive to any newborn lamb, but within less than 1 h, mothers learn to recognize the odor of their lamb and restrict maternal care to their own offspring (maternal selectivity). In a first experiment, we investigated the long-term retention of maternal selectivity after various mother-young contact and separation durations. After 4 h of contact, 36 h of separation leads to a total loss of selectivity. Increasing contact duration to 7 days prior to this separation maintains selectivity. These data suggest that lamb memory after going through an initial labile state after parturition, is consolidated over time into a more stable long-term memory. Fos immunohistochemistry reveals that reintroduction of the lamb after 4 h of mother-young contact and 3 h of separation activates different maternal brain regions than reintroduction of the lamb after 7 days of mother-young contact and 3 h of separation. While the piriform cortex shows an enhanced activation at both times, a selective enhancement of activation is observed in the frontal medial and orbitofrontal cortices only after 7 days of mother-young contact. These data suggest that as consolidation occurs, the neurobiological networks sustaining lamb memory involve different structures.

Animals↗
PubMed2004

Functional MRI mapping of brain activation during visually guided saccades and antisaccades: cortical and subcortical networks.

Antisaccade tasks require a subject to inhibit a saccade toward a briefly appearing peripheral target and instead to immediately generate a saccade to an equivalent point in the opposite hemifield. Using functional magnetic resonance imaging (fMRI), we investigated the neural networks required to inhibit reflexive saccades and to voluntarily generate saccades. The results demonstrated that saccade and antisaccade tasks often bilaterally activate frontal, parietal and supplementary eye fields, lenticular nuclei and occipital cortex. Additional activation of bilateral dorsolateral prefrontal cortices, supramarginal gyri, anterior cingulate cortices and thalamus was observed during antisaccade tasks. These results indicate that fronto-parietal and fronto-striato-thalamo-cortical circuits are involved in antisaccade tasks. The fronto-parietal circuit is thought to be related to the planning of saccadic eye movements that involve attentional control, while the fronto-striato-thalamo-cortical circuits connect to cortical region as a feedback network. We speculate that the abnormalities in spatial attention and eye movement control observed in schizophrenia stem from dysfunctions in the fronto-parietal and fronto-striato-thalamo-cortical circuits.

Adult↗
PubMed1997

Autoradiographic mapping of brain 5-HT2A binding sites in P and in AA alcohol-preferring rats.

There is considerable evidence for an involvement of serotonergic mechanisms in the control of alcohol consumption. In the present study, an extensive 5-HT2A receptor autoradiographic investigation was carried out in two genetically selected rat strains, P and AA alcohol-preferring rats, respectively, as well as in the corresponding NP and ANA alcohol-nonpreferring rats. The aim was to determine if there is any common pattern in 5-HT2A binding site densities that may illuminate mechanisms of alcohol preference in these animals. For quantitating 5-HT2A binding sites, [3H]ketanserin (2 nM) was used. Nonspecific binding was measured in the presence of methysergide 10(-6) M. Results demonstrated a lower level (from 50 to 70%) of 5-HT2A binding sites in the layer IV of prefrontal cortex, frontal cortex, parietal cortex of P rats compared to NP controls. Similarly, in the claustrum, 5-HT2A binding density of P rats was 50% lower than that of NP rats, although this failed to achieve statistical significance. No difference was detected in the other areas investigated, including the olfactory tubercles, nucleus accumbens, caudate putamen, pyriform cortex, ventral tegmental area, temporal cortex, and entorhinal cortex. In AA rats, [3H]ketanserin binding density measured in these brain areas was very similar to that observed in ANA nonpreferring controls, and statistical analysis did not reveal any significant difference between the two rat lines. The present study confirms previous reports demonstrating lower densities of 5-HT2A binding sites in the P rats and provides the first autoradiographic evidence showing that such an alteration does not occur in AA rats. These findings suggest that the expression of high alcohol preference in genetically selected P and AA rats is not associated with a shared neurochemical alteration of the 5-HT2A receptor system.

Alcoholism↗
PubMed2001

Spatiotemporal mapping of brain activity by integration of multiple imaging modalities.

Functional magnetic resonance imaging (fMRI) and positron emission tomography measure local changes in brain hemodynamics induced by cognitive or perceptual tasks. These measures have a uniformly high spatial resolution of millimeters or less, but poor temporal resolution (about 1s). Conversely, electroencephalography (EEG) and magnetoencephalography (MEG) measure instantaneously the current flows induced by synaptic activity, but the accurate localization of these current flows based on EEG and MEG data alone remains an unsolved problem. Recently, techniques have been developed that, in the context of brain anatomy visualized with structural MRI, use both hemodynamic and electromagnetic measures to arrive at estimates of brain activation with high spatial and temporal resolution. These methods range from simple juxtaposition to simultaneous integrated techniques. Their application has already led to advances in our understanding of the neural bases of perception, attention, memory and language. Further advances in multi-modality integration will require an improved understanding of the coupling between the physiological phenomena underlying the different signal modalities.

Animals↗
PubMed2003

Mapping of brain function after MPTP-induced neurotoxicity in a primate Parkinson's disease model.

Neurophysiological studies of the brain in normal and Parkinson's disease (PD) patients have indicated intricate connections for basal ganglia-induced control of signaling into the motor cortex. To investigate if similar mechanisms are controlling function in the primate brain (Macaca fascicularis) after MPTP-induced neurotoxicity, we conducted PET studies of cerebral blood flow, oxygen and glucose metabolism, dopamine transporter, and D2 receptor function. Our observations after MPTP-induced dopamine terminal degeneration of the caudate and putamen revealed increased blood flow (15%) in the globus pallidus (GP), while blood flow was moderately decreased (15-25%) in the caudate, putamen, and thalamus and 40 % in the primary motor cortex (PMC). Oxygen extraction fraction was moderately increased (10-20%) in other brain areas but the thalamus, where no change was observable. Oxygen metabolism was increased in the GP and SMA (supplementary motor area including premotor cortex, Fig. 3) by a range of 20-40% and decreased in the putamen and caudate and in the PMC. Glucose metabolism was decreased in the caudate, putamen, thalamus, and PMC (range 35-50%) and enhanced in the GP by 15%. No change was observed in the SMA. In the parkinsonian primate, [(11)C]CFT (2beta-carbomethoxy-3beta-(4-fluorophenyltropane) dopamine transporter binding was significantly decreased in the putamen and caudate (range 60-65%). [(11)C]Raclopride binding of dopamine D(2) receptors did not show any significant changes. These experimental results obtained in primate studies of striato-thalamo-cortico circuitry show a similar trend as hypothetized in Parkinson's disease-type degeneration.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1998

New methods for three dimensional mapping of brain waves.

The representation of spatiotemporal pattern of brain electrical activity is an important issue in the research of neural assemblies. This paper describes methods of parametric 3D head or brain modeling and its corresponding interpolation for functional imaging based on brain waves. The 3D interpolation method is an extension of cortical imaging technique. It can be used with features of either transformed domains or higher order statistics of brain waves on realistic head or brain models. The simulating result suggests that it is a better method in comparison with the global nearest neighbor technique. With those techniques, an example of brainwave imaging was given using partial coherence of event-related potentials estimated by multivariate autoregressive model.

Brain Mapping↗
PubMed2005

Mapping metabolic brain activation during human volitional swallowing: a positron emission tomography study using [18F]fluorodeoxyglucose.

We have previously shown that labelled water positron emission tomography (H2(15)O PET) can be used to identify regional cerebral blood flow (rCBF) changes in the human brain during volitional swallowing. (18F) fluorodeoxyglucose (FDG PET), by comparison, uses a glucose analogue to quantitatively measure regional cerebral glucose metabolism (rCMRglc) rather than rCBF. The main advantage of FDG PET is improved spatial resolution, and because of its pharmacodynamic properties, activation can be performed external to the scanner, allowing subjects to assume more physiologic positions. We therefore conducted a study of the brain's metabolic response while swallowing in the erect seated position, using FDG PET. Eight healthy male volunteers were studied with a randomised 2 scan paradigm of rest or water swallowing at 20-second intervals for 30 minutes. Data were analysed with SPM99 using multisubject conditions and covariates design. During swallowing, analysis identified increased rCMRglc (P<0.01) in the following areas: left sensorimotor cortex, cerebellum, thalamus, precuneus, anterior insula, left and right lateral postcentral gyrus, and left and right occipital cortex. Decreased rCMRglc were also seen in the right premotor cortex, right and left sensory and motor association cortices, left posterior insula and left cerebellum. Thus, FDG PET can be applied to measure the brain metabolic activity associated with volitional swallowing and has the advantage of normal task engagement. This has implications for future activation studies in patients, especially those suffering swallowing problems after brain injury.

Adult↗
PubMed1993

Functional mapping of brain areas implicated in auditory--verbal memory function.

Positron emission tomography measurements of regional cerebral blood flow (rCBF) were performed in normal volunteers during two auditory--verbal memory tasks: a subspan and supraspan task. The difference in rCBF between tasks was used to identify brain areas/systems involved in auditory--verbal long-term memory. Increases in rCBF were observed in the left and right prefrontal cortex, precuneus and the retrosplenial area of the cingulate gyrus. Decreases in blood flow were centred in the superior temporal gyrus bilaterally. Separate comparisons were also made between each span task and a resting state. Brain regions showing increases in rCBF in these comparisons included the thalamus, left anterior cingulate, right parahippocampal gyrus, cerebellum and the superior temporal gyrus. The brain areas identified in these comparison define a number of the neuroanatomical components of a distributed system for signal processing and storage relevant to auditory--verbal memory function.

Adult↗
PubMed1993

Neuromagnetic mapping of brain function.

Magnetic source imaging, a technique that combines magnetoencephalography (MEG) and magnetic resonance (MR) imaging, was used to localize the somatosensory and auditory cortex in seven healthy subjects. Functional neuromagnetic data were obtained with a 37-channel biomagnetometer. Structural MR imaging data were obtained with a 1.5-T superconducting imager. Coordinates used in defining MEG and MR imaging space were reconciled to produce magnetic source images that displayed the putative locations of somatosensory and auditory activity in relation to brain anatomy. Sources of somatosensory activity were typically localized to the postcentral gyrus; sources of auditory activity were localized to the superior temporal plane. Extension of these results to patients with tumors (or other disorders) that distort normal brain anatomy has the potential to make noninvasive magnetic source imaging examinations clinically useful in guiding neurosurgical interventional procedures.

Adult↗
PubMed2004

Mapping the brain's orchestration during speech comprehension: task-specific facilitation of regional synchrony in neural networks.

BACKGROUND: How does the brain convert sounds and phonemes into comprehensible speech? In the present magnetoencephalographic study we examined the hypothesis that the coherence of electromagnetic oscillatory activity within and across brain areas indicates neurophysiological processes linked to speech comprehension. RESULTS: Amplitude-modulated (sinusoidal 41.5 Hz) auditory verbal and nonverbal stimuli served to drive steady-state oscillations in neural networks involved in speech comprehension. Stimuli were presented to 12 subjects in the following conditions (a) an incomprehensible string of words, (b) the same string of words after being introduced as a comprehensible sentence by proper articulation, and (c) nonverbal stimulations that included a 600-Hz tone, a scale, and a melody. Coherence, defined as correlated activation of magnetic steady state fields across brain areas and measured as simultaneous activation of current dipoles in source space (Minimum-Norm-Estimates), increased within left- temporal-posterior areas when the sound string was perceived as a comprehensible sentence. Intra-hemispheric coherence was larger within the left than the right hemisphere for the sentence (condition (b) relative to all other conditions), and tended to be larger within the right than the left hemisphere for nonverbal stimuli (condition (c), tone and melody relative to the other conditions), leading to a more pronounced hemispheric asymmetry for nonverbal than verbal material. CONCLUSIONS: We conclude that coherent neuronal network activity may index encoding of verbal information on the sentence level and can be used as a tool to investigate auditory speech comprehension.

Acoustic Stimulation↗