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At least 595 records · Page 33Linked to original sources

PubMed1994

Effects of transcranial magnetic stimulation on single and sequential arm movements.

We studied in humans the effects of transcranial stimulation of cortical motor areas on the execution of single and sequential rapid arm movements. In a reaction time paradigm with an auditory "go" signal, stimulation given after an auditory tone and before the start of movements delayed the onset but did not affect the subsequent performance of single or sequential movements; high intensities of cortical stimulation determined a long-lasting inhibition of movements. Cortical stimulation given during the execution of a sequential movement temporarily interrupted the movements. Reaction time was not prolonged and movements were not inhibited when cortical stimulation was delivered before the auditory tone and the start of movement. Neither electrical stimulation of the corticospinal tracts at the cervico medullary junction nor magnetic stimulation of the cervical roots delayed the onset or interrupted the execution of movements. Transcranial stimulation affects the performance of both single and sequential movements, through cortical mechanisms that interfere with the transfer of the motor program from other cortical structures to the motor cortex.

Adult↗

PubMed1978

On magnopyramidal temporal fields in the human brain - probable morphological counter parts of Wernicke's sensory speech region.

Posterior parts of the human superior temporal gyrus have been examined by means of stereomicroscopical observations of pigment preparations up to 800 microgram thick. As a rule, the proximal half of the first transverse gyrus of Heschl is covered by an extremely lightly pigmented conicortex which is surrounded by belt areas, a proncoinocortex anteriorly and paraconiocortical fields posteriorly and laterally. The paraconiocortex is divisble into a primitively organized part lying just behind the conicortical core and a more advanced portion forming the temporal magnopyramidal region. This extended lateralmost part of the paraconicortex is more or less richly endowed with unusually large and pigment-rich IIIc-pyramids. Third layer pyramidal cells showing densley aggregated lipofuscin deposits are rarely encountered within the human isocortex. As regards the temporal lobe, pyramids of this type, in general, do not occur outside the magnopyramidal region. The magnopyramidal region covers only a part of the temporal plane but extends much more in the lateral direction spreading over distal portions of the first and the second transverse gyri, posterior parts of the exposed surface of the superior temporal gyrus and those of its lower wall. The extension of the magnopyramidal region varies considerably from one side of the brain to the other. It is also subject to a pronounced variation from one individual to another. On account of its localization and its uniqueness in cortical structure, the temporal magnopyramidal region is considered to represent the morphological counterpart of the sensory speech centre of Wernicke.

Aged↗

PubMed1987

The use of computed tomography to quantitate bone formation after distraction epiphysiolysis in the rabbit.

A study of limb lengthening by distraction epiphysiolysis in the rabbit tibia is presented. For this purpose a special external distraction device was developed, which allowed 10 mm lengthening of the leg. Bone formation in the distraction zone was quantified by means of computed tomography. Cross-sectional scan planes at 1.5 mm separation revealed bone formation proceeding for several weeks after the end of the distraction period. A period of bone remodeling followed, resulting in the formation of a solid cortical structure, similar to the diaphysis, in the distraction zone.

Animals↗

PubMed1994

Alzheimer's disease with asymmetric atrophy of the cerebral hemispheres: morphometric analysis of four cases.

To examine the clinicopathological correlations in rare Alzheimer's disease patients with asymmetric cerebral atrophy and to compare their pattern of cortical involvement by senile lesions with that observed in other cases with atypical Alzheimer's disease, we performed an extensive neuropathological analysis of the cerebral cortex in four such cases. Three patients presented with severe language impairment but relatively good preservation of praxis and gnosis even after several years of clinical evolution. Cerebral autopsies of these cases revealed a predominant left hemisphere atrophy. Conversely, in one case with marked right hemisphere atrophy, all of the cognitive functions were involved early in the course of dementia. Neurofibrillary tangles and senile plaques were preferentially localized in the prefrontal, temporal and posterior parietal cortex in both hemispheres, whereas the hippocampal formation displayed lower lesion densities than neocortical areas. Significantly higher neurofibrillary tangle and senile plaque densities were found in the more atrophic side in most of the areas studied. The ratio of neurofibrillary tangle and senile plaque densities between the two hemispheres was not correlated with the number of these lesions in the cerebral cortex. These results indicate that the degenerative process in demented cases with interhemispheric asymmetric cerebral atrophy is characterized by a widespread involvement of the neocortex by senile lesions and lacks clear regional topography of neurofibrillary tangle and senile plaque distribution. Moreover, the relative sparing of the hippocampus, comparable to that found in cases with focal progressive dementia, suggests that the dementing process may involve different cortical structures in cases with asymmetric cerebral atrophy than in typical Alzheimer's disease cases.

Aged↗

PubMed1980

Regional cerebral blood flow in a case of amphetamine intoxication.

The regional cerebral blood flow (133Xe-inhalation method) was measured during acute amphetamine intoxication in a male 25 years old addict. During the study the patient displayed symptoms of paranoia and slight euphoria and tension. The flow level was found to be elevated by about 30% compared to a study in non-intoxicated state. The augmentation was most marked in the left hemisphere and in frontal regions (local increases up to 100%). The results confirm earlier findings in animal models and indicate the central role of frontal cortical structures in the production of psychotic symptoms.

Adult↗

PubMed1986

Acetabular reinforcement in total hip replacement.

In 21 cases of severe secondary protrusio acetabuli with extensive or total destruction of the acetabular cortical structures, the double anchorage of conventional polyethylene cups with nine Müller acetabular reinforcement rings and 12 Burch-Schneider anti-protrusio reinforcement cages was carried out. They were applied in combination with reconstructive surgery of cancellous bone in three primary total hip replacements and in 18 revision operations for loosened acetabular cups following total arthroplasties. Indication for and technique of the acetabular reinforcement are described. The radiological and clinical results in 21 patients followed up were satisfactory. They confirm the efficiency of these screw-fixed reinforcement implants for the solid fixation of the plastic cup in patients with extreme acetabular deficiencies.

Acetabulum↗

PubMed1989

Evidence that dopaminergic sympathetic axons supply the medullary arterioles of human kidney.

The ability of the kidney to excrete sodium appears to depend on release of dopamine from intrarenal sources. In the present study, we have used immunohistochemistry to examine the possibility that renal dopaminergic nerves constitute one of these sources. We found that the sympathetic axons supplying cortical structures in human kidney contain tyrosine hydroxylase-like immunoreactivity but lack DOPA decarboxylase-like immunoreactivity. By contrast, the vasa recta arterioles of the renal medulla are supplied by varicose tyrosine hydroxylase-positive nerve fibres, some of which also contain DOPA decarboxylase. As DOPA decarboxylase has been demonstrated in other situations to be a selective marker for dopaminergic terminal axons, our results suggest the innervation of renal medullary blood vessels in man by both noradrenergic and dopaminergic sympathetic nerves.

Adult↗

PubMed1987

Myoclonus in Alzheimer's disease.

Myoclonus was studied electrophysiologically in seven patients with clinically diagnosed Alzheimer's disease. There seem to be at least two physiological types of myoclonus in Alzheimer's disease. Cerebral cortical structures might participate in the generation of myoclonus in one type, while the other type is probably generated by subcortical structures.

Aged↗

PubMed1991

Source modelling of the rolandic focus.

In rolandic epilepsy, consideration of the stereotyped ictal symptomatology suggests that the epileptic zone is likely to be in the same cortical structure in different patients. Routine EEG tracings of the interictal spike activity suggests a deep Sylvian fissure location. On the basis of the predominantly tangential potential field at the peak spike negativity seen in this group of patients, the inferior bank of the Sylvian fissure appears to be a good candidate. Without invasive studies, little refinement to this rather imprecise localization can be made as there is neither neurologic deficit nor lesion to provide a marker on radiological imaging. However, the application of source modelling technique using a simple single-dipole spherical head model has resulted in improved understanding of the generator behaviour, and facilitated the generation of new ways of analyzing spikes (e.g., stability index). Review of newer quantitative approaches including matrix and singular value decomposition of the dataset, spatial-temporal constrained source estimates etc. suggest other fruitful approaches. At least in some patients with partial epilepsy, the source characteristics of interictal scalp spikes appear to contain information of the ictal generator. Under certain circumstances, such derived information which is not otherwise available from routine electrophysiology may influence clinical management and prognosis. This is an additional bonus to the primary objectives of quantification and data reduction.

Brain↗

PubMed1997

The reflection of cognitive tasks in EEG and MRI and a method of its visualization.

Up until recently, neurology was dominated by localisatory thinking. Language and other so-called "centers" were considered to be centers of command controlling the respective functions. Today, there is general agreement that, instead, for every brain function numerous brain regions must act together. For the exploration of these manifold topographic cooperations produced by cognitive tasks, coherence of long-term EEG periods proved to be a proficient parameter for the representation of functionally essential connections. Because of the unequivocal meaningfulness of absolute coherence values, instead, only the signs of significant differences between coherence values during cognitive tasks and periods of EEG at rest before and after the task were considered for all possible electrode pairings and charted on schematic maps of the brain. In addition, the signs of significant changes of amplitude were entered. This procedure was performed for each of 6 frequency bands and for the 19 electrodes of the 10/20 system, thus yielding 171 possible plus or minus values for coherence and 19 for amplitude, respectively. The positions of the electrodes were marked by an MRI contrast medium. After the EEG, MRI examination was performed. The MRI data were segmented and the cortex was mapped onto a plane using a method similar to cartography. The exact electrode positions are registered from a similarly obtained map of the scalp and the electrode position pattern is used as basis for the coherence graphs. A detailed map of the cortex based on the segmented MRI data with the electrode positions marked is provided as a reference enabling allocation of the electrodes to the cortical structures. The usefulness of this procedure is demonstrated with a single subject by means of different cognitive tasks including musical thinking.

Aged↗

PubMed1979

Post-mortem distribution of dopamine and homovanillic acid in human brain, variations related to age, and a review of the literature.

The post-mortem brain concentrations of dopamine (DA) and homovanillic acid (HVA) were determined in 16 parts of the brain from patients with no history of neurologic or psychiatric illness. Fifteen men and nine women, with a mean age of 61.0 +/- 18.7 years (range 23--92 years) were included. They had died from either ischaemic heart disease or cancer. In the post-mortem investigation several factors were controlled: age, time between death and autopsy, time between autopsy and chemical analysis and storage time (-20 degrees C). The DA concentrations in the different brain areas were found to be positively intercorrelated, especially those in the basal ganglia, hippocampus and the mesencephalon. The HVA concentrations measured in various cortical structures were also positively intercorrelated. In several regions of the brain there was a significant inverse correlation between the DA and HVA concentrations. The DA and HVA concentrations did not differ according to sex, but age had a marked influence on the DA concentration. Significant decrease with age was observed in the nucleus caudatus, globus pallidus, mesencephalon, hippocampus and in the cortex gyrus hippocampus. These findings are discussed in relation to the effect of aging neurons. A review of human post-mortem investigations on DA and HVA concentrations is also presented.

Adult↗

PubMedDate not supplied

Role of cholinergic mechanisms in alterations of rabbit brain functional activity during sea-sickness.

Using the hydrogen-clearance method in chronic experiments on alert rabbits, we investigated the dynamics of changes in local and total cerebral blood-flow, oxygen pressure, bioelectrical activity of the motor, auditory, and visual zones of the cerebral cortex, the heart rate during sea-sickness and the effect of the cholinolytic scopolamine upon changes in these indices. It was found that scopolamine affects the character and direction of changes in both local and overall blood flow in the brain during sea-sickness. Scopolamine does not substantially alter oxygen pressure in the cortical structure of the brain and does not eliminate brachycardia arising during sea-sickness. On the electrocorticogram (ECoG), it does cause an intensification of activational processes and an increase in the total bioelectrical activity, especially in the motor zones of the cerebral cortex. It is suggested that the protective effect of scopolamine during sea-sickness is connected with its central cholinolytic action and with the decrease it brings about in the cerebral hemodynamics and bioelectrical activity of the cerebral cortex arising during "motion sickness."

Animals↗

PubMed1993

The role of the cerebral cortex in swallowing.

This paper reviews clinical, neuroanatomical, and neurophysiological studies that have implicated the cerebral cortex in the initiation and/or regulation of swallowing as well as related functions such as mastication. Cortical dysfunction has been reported to result in a variety of swallowing impairments. Furthermore, swallowing can be evoked and/or modulated by stimulation applied to restricted regions of the cortex. Neuroanatomical investigations and single neuron recording studies also provide some insights into the cortical structures, pathways, and mechanisms that may mediate deglutition.

Cerebral Cortex↗

PubMed1996

Annexins in Paramecium cells. Involvement in site-specific positioning of secretory organelles.

Annexins were isolated from Paramecium cell homogenates by standard ethylene glycol tetraacetic acid (EGTA) extraction and 100 000-g centrifugation. Two different antibodies (Abs) against synthetic peptides were used, Call-15 and B15, which in mammalian cells recognize a sequence of annexin II or a common sequence occurring in several annexins (except for annexin II), respectively. With anti-Call-15 Abs, western blots from EGTA extracts showed strongly reactive bands of 44.5 and 46 kDa and of higher values. Some of these bands bound to the 100 000-g pellet fraction when Ca(2+) was added. Immuno- and affinity labelling revealed selective, Ca(2+)-dependent labelling of the cell cortex, with enrichment around trichocyst docking sites (facing subplasmalemmal Ca(2+) stores). Cortical fluorescence labelling decreased in wild-type (7S) cells when trichocyst ghosts were detached after synchronous exocytosis. Similarly, cortical labelling was reduced when intact trichocysts were detached from the cell surface of non-discharge mutant cells (nd9-28 degrees C, showing identical bands on blots), which then contained numerous heavily labelled phagolysosomes. This strongly suggests annexin downregulation. All together, the dynamic labelling of cortical structures we observed strongly supports involvement of calpactin-like annexins in trichocyst docking. Anti-B15 Abs recognized a band of 51 kDa and some of higher values. These Abs selectively labelled the outlines of the cytoproct, the site of spent phagolysosome exocytosis. In conclusion, our data indicate involvement of specific sets of annexins in site-specific positioning and attachment of widely different secretory organelles at the cell surface in Paramecium cells.

Animals↗

PubMed1996

Theoretical situation of brain white matter tracts evaluated by three-dimensional MRI.

An accurate knowledge of cerebral anatomy is important in order to evaluate the precise location of a cerebral lesion. Cortical structures are identified by knowledge of the adjacent gyri and sulci; however, white matter tracts are difficult to differentiate from one another due to the lack of clear anatomic landmarks. Therefore, even if MRI shows obvious white matter abnormalities, in some cases it is difficult accurately to localize the lesion. The purpose of this study is to evaluate the location of the main white matter tracts by using three-dimensional MR imaging. MRI study was performed by 1.5 Tesla (Signa: General Electric). Computer assisted analysis with Voxtool software (General Electric) was used to generate both surface brain and tomographic images. The exact anatomic basis of white matter signal abnormalities is important when analyzing patients with disconnective syndromes or neuropsychological deficits such as conduction aphasia, visuospatial deficit etc. This preliminary attempt at constructing a three-dimensional MRI white matter atlas of the brain may be helpful for evaluating the anatomico-clinical correlations in these patients, and also as teaching materials for the clinical (neurologic, neurosurgical), anatomic and radiographic disciplines.

Adult↗

PubMed1978

The sequential uptake of (14C) deoxyglucose in brain after embolic stroke.

An i.v. bolus of (14C) deoxyglucose was injected into 4 groups of rats which simultaneously were embolized through the internal carotid artery. 15 and 30 min post embolization there was a massive decrease in (14C) deoxyglucose uptake in both deep and cortical structures. At 4 h a small zone of increased (14C) deoxyglucose uptake persisted around each embolized microsphere.

Animals↗

PubMedDate not supplied

Intracellular mechanisms of glutaminergic and cholinergic signal transduction in the cerebral cortex.

A complex method was used to study the effects of acetylcholine and glutamine on the dynamics of calcium and polyphosphoinositide regulatory system activities over prolonged periods of time in the mammalian cerebral cortex, after exposure to these substances in baseline conditions and in conditions of developing adaptive responses. Adaptive responses were induced by transient hypoxia with oxymetacil as an antioxidant. Agonist stimulation of choline and glutamate receptors produced prolonged calcium and phosphoinositide responses in cortical structures; these had specific characteristics after exposure to glutamate and acetylcholine. During the development of adaptive responses, these changes underwent significant modifications. The functional importance of these effects is discussed.

Animals↗

PubMed1996

Dependence of coherence measurements on EEG derivation type.

The impact is reported of different EEG derivation types on short-term changes in the inter-hemispheric coherence between the left and right sensorimotor areas, during the planning and execution of right index finger movements. Data are recorded during an event-related paradigm in which cued index finger movements are made: Event-related coherence analysis is then applied to the monopolar (nose reference) data, as well as different reference-independent derivations such as bipolar, local average reference and source derivation. The results show that inter-hemispheric coherence between sensorimotor areas is dependent on the EEG derivation type. An increase in coherence during movement is found with nose reference and bipolar data, whereas for local average reference and source derivations, low inter-hemispheric coherence is observed, with no change in the coherence during movement. It is concluded that the coherence increase seen with nose reference data is due to an indirect effect of mu rhythm desynchronisation, rather than any increase in synchrony of the mu rhythms themselves. Local average reference and source derivations better reflect the activity of the underlying cortical structures (the mu generating networks), and coherence analysis using these derivations shows that the mu rhythms of left and right hemispheres are not coherent.

Electroencephalography↗