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At least 307 records · Page 17Linked to original sources
PubMed2004

New partially parallel acquisition technique in cerebral imaging: preliminary findings.

In MRI applications where short acquisition time is necessary, the increase of acquisition speed is often at the expense of image resolution and SNR. In such cases, the newly developed parallel acquisition techniques could provide images without mentioned limitations and in reasonably shortened measurement time. A newly designed eight-channel head coil array (i-PAT coil) allowing for parallel acquisition of independently reconstructed images (GRAPPA mode) has been tested for its applicability in neuroradiology. Image homogeneity was tested in standard phantom and healthy volunteers. BOLD signal changes were studied in a group of six volunteers using finger tapping stimulation. Phantom studies revealed an important drop of signal even after the use of a normalization filter in the center of the image and an important increase of artifact power with reduction of measurement time strongly depending on the combination of acceleration parameters. The additional application of a parallel acquisition technique such as GRAPPA decreases measurement time in the range of about 30%, but further reduction is often possible only at the expense of SNR. This technique performs best in conditions in which imaging speed is important, such as CE MRA, but time resolution still does not allow the acquisition of angiograms separating the arterial and venous phase. Significantly larger areas of BOLD activation were found using the i-PAT coil compared to the standard head coil. Being an eight-channel surface coil array, peripheral cortical structures profit from high SNR as high-resolution imaging of small cortical dysplasias and functional activation of cortical areas imaged by BOLD contrast. In BOLD contrast imaging, susceptibility artifacts are reduced, but only if an appropriate combination of acceleration parameters is used.

Artifacts↗
PubMed2003

Panic attacks, spike-wave activity, and limbic dysfunction. A case report.

INTRODUCTION: Several lines of evidence indicate that an increased neuronal excitability of the corpus amygdaloideum and hippocampus may be one pathophysiological condition of panic attacks. METHODS: In this report, we will describe the case of a 54-year-old female patient with a depressive syndrome who first experienced very rapid atypical panic attacks with dizziness, trance-like and distorted optical perception, but without clear epileptic symptoms. RESULTS: Several EEG recordings showed temporal sharp-waves and spike-wave patterns. Magnetic resonance imaging (MRI) revealed a hypodense area near left mesial temporal structures. Brain imaging with SPECT showed a hypoperfusion of the basal temporal cortical structures on the left side. Treatment with antidepressants had no effect, but the addition of valproic acid led to an attenuation of the panic attacks and epileptic potentials on the EEG. DISCUSSION: A clinical trial using anti-epileptics could be successful in patients not responding to antidepressants or in the presence of epileptiform EEG activity. In this article, we will review the literature concerning the complex relationship between panic attacks and ictal activity of limbic structures and discuss the difficult diagnostic classification of atypical cases.

Anticonvulsants↗
PubMed1981

Effects of cystment on cells of Oxytricha fallax possessing supernumerary dorsal bristle rows.

Cells of Oxytricha fallax possessing cytotactically inherited supernumerary dorsal bristle rows can redevelop those dorsal supernumerary rows after cystment, even though supernumerary ventral cortical structures are permanently lost through cystment. Previous work has demonstrated: (1) that cystement involves a complete dedifferentiation of all ciliary structures-all cilia, basal bodies, microtubules and fibres; and (2) that all ventral ciliary structures arise from a single ciliary primordium during excystement. These observations suggest the following conclusions. (1) The information for the redevelopment of supernumerary dorsal bristle rows during excystment is associated with some ultrastructurally unidentifiable molecular structure of the cyst cortex. (2) Cytotactic information for the development of cortical patterns is retained in at last two locations in the resting cyst; one location specifies the site of development of the ventral ciliature whereas the other specifies the location and pattern of the dorsal ciliature.

Ciliophora↗
PubMed1978

[Mechanisms of interaction between the parietal association and projection areas of the cat neocortex].

The pecularities of evoked potentials changes in the first visual, first somatic and parietal cortical areas locally cooled under nembutal anesthesia, as well as in the association thalamic nuclei (pulvinar and posterolateral) were studied in cats. Two types of interaction between these cortical structures were distinguished. Type I interaction was observed between all the studied cortical areas; type II--took place only between the parietal and each of the projection areas. Type I is suggested to be formed by cortical connections, type II--by direct and indirect subcortical ones. The peculiarities of involving the association parietal area into type I and II interactions according to its activation by different modality signals are discussed.

Animals↗
PubMed1997

[Mesial temporal sclerosis (I): histological data, physiopathological hypothesis and etiological factors].

OBJECTIVE: To review the main anatomical, histological, physiopathological and aetiological data characteristic of the mesial temporal sclerosis syndrome (ETM). Development. The typical histological findings in ETM are: 1) A specific pattern of loss of neurone density which includes so-called endfolium sclerosis (considered to be a specific pathological entity always found in ETM), and which is usually accompanied by neurone loss in other hippocampal and extra-hippocampal regions. The CA2 region is never affected. 2) Phenomenon of 'mossy fibers sprouting' which are granulosa cells which form two types of synapses: with the the 'basket cells' which are inhibitory interneurones and with the dendrites of granulosa or pyramidal cells of the CA1, CA2 and CA3 Ammon horn cells which are excitatory cells. CONCLUSIONS: Probably these organic changes are both the cause and effect of repeated convulsions. Participation in this self-perpetuating circuit may be due to recognised risk factors of ETM (head injury, CNS infections, febrile convulsions in early stages of development) which cause, first of all, death of neurones of the dentate gyrus cells followed by reduced inhibitory activity of the 'basket' cells and therefore sustained hyper-excitability of the pyramidal cells (especially in the CA3 regions), which are responsible for complex partial seizures and massive liberation of glutamic acid. Glutamic acid can cause death of neurones of the granulosa cells of the dentate gyrus, thus closing the circuit. This hypothesis explains the progressive nature of the ETM syndrome. When there is pathology of the cortical structure there is another access via to this circuit--by means of cortical discharges of the so-called perforant pathway which stimulates activity of the pyramidal cells and sets off the chain of events described above. This hypothesis explains the so-called 'dual pathology'.

Brain Injuries↗
PubMedDate not supplied

Morphology and development of mirror-image doublets of Stylonychia mytilus.

This paper describes the cortical anatomy and development of mirror-image doublets of Stylonychia mytilus, analyzed using the protargol technique. The reversed, or "left-handed" (LH) component of these doublets is a mirror image of the normal or "right handed" (RH) component with regard to the arrangement of cortical structures. The mirror-image patterning is imperfect, however, as the individual ciliary structures of the LH component all are of normal internal asymmetry, and the orientation of membranelles is inverted. Certain structures that would be expected to form near the line of symmetry are absent. During cell division and cortical reorganization, ciliary primordia arise and become arranged in a mirror-image pattern that is more perfect than that exhibited by the mature structures. Deviations from a mirror-image pattern appear at late stages when organelle sets differentiate within ciliary primordia: for example, the membranelle set differentiates within the oral primordium of the LH component in a sequence that is an inversion rather than a mirror image of the corresponding sequence of the RH component. This mixed control of oral development by different cortical "informational systems" accounts for some of the characteristic abnormalities of the mature oral structures of the LH component.

Animals↗
PubMed1993

Quantitative immunohistochemical analysis of the distribution of neurofibrillary tangles and senile plaques in the cerebral cortex of nonagenarians and centenarians.

To investigate the neuropathological differences between normal aging and senile dementia of the Alzheimer type (SDAT) in very old people and to see how they compare with a younger population of demented elderly people, we performed an immunohistochemical quantitative analysis of the topography of senile plaques and neurofibrillary tangles in a series of 31 elderly patients aged from 96 to 102 years. According to the medical records, two groups were considered: 7 patients presenting with clinically documented SDAT and 24 patients with no or very mild cognitive impairment. The densities of senile plaques were comparable in both groups. Extensive neurofibrillary tangle formation was restricted to the CA1 hippocampal field of demented subjects, whereas the superior frontal cortex showed rare neurofibrillary tangles, independently of the clinical diagnosis. These results indicate an absence of direct correlation between the number of senile plaques and the clinical manifestation of SDAT. Furthermore, they suggest that the dementing process may involve different cortical structures in nonagenarians and centenarians than in younger demented individuals where a widespread cortical involvement is generally observed. Thus, the neurofibrillary tangle density in the CA1 field may be critical for the neuropathological diagnosis of SDAT in this particular group of very old patients.

Aged↗
PubMed1992

Pre-frontal structural and functional deficits associated with individual differences in schizotypal personality.

This study tests the hypothesis that pre-frontal deficits underlie schizotypal personality in the normal population. Personality measures assessing features of DSM-IIIR schizotypal personality disorder (SPD) were related to left and right pre-frontal brain area assessed by magnetic resonance imaging (MRI), and neuropsychological measures of pre-frontal functioning (Wisconsin Card Sorting Task, WCST) in a group of non-institutionalized, unmedicated normal subjects. High schizotypal scores were significantly associated with reduced pre-frontal area and more WCST perseveration errors; conversely no relationships were observed between these pre-frontal measures and measures of psychosis-proneness unrelated to SPD traits. Pre-frontal structural findings were not found to be mediated by temporal lobe and posterior cortical structural deficits, height, weight, socio-economic status, education level and sex differences, while pre-frontal functional findings were not mediated by non-prefrontal cognitive ability. These findings of pre-frontal structural and functional deficits associated with schizotypal personality provide some initial converging support for a pre-frontal explanation of individual differences in schizotypal personality in the general population.

Adult↗
PubMedDate not supplied

[A method for the in vivo measurement of the mineral content in an experimental animal].

Bone mineral content measurement is not as widely used in experimental conditions as in clinical practice because of the lack of adequate experimental methods. An in vivo measurement method of bone mineral content in the rat is here presented. Measurements were made at the proximal tibio-peroneal segment, which has a mainly trabecular structure, by means of single photon absorptiometry. The presence of the fibula, having cortical structure, has been shown not to affect the read values, which can be therefore attributed to the tibial metaphysis, having a mainly trabecular structure. Expressing mineral content values as a function of the measured bone diameter has proven useless. Limb repositioning on the instrument holding device is critical for the reproducibility of the measurement, but the latter is not affected by the repositioning method. Method reproducibility (depending on either the intrinsic instrumental error or the repositioning error) is 5-6%. This relatively low reproducibility of the suggested method does not prevent its use in the study of physiological and pathological variations of bone mineral content in rats, and of the means to influence it.

Absorptiometry, Photon↗
PubMed1993

The patterns of afferent innervation of the core and shell in the "accumbens" part of the rat ventral striatum: immunohistochemical detection of retrogradely transported fluoro-gold.

Recent data have emphasized the neurochemically distinct nature of subterritories in the accumbens part of the rat ventral striatum termed the core, shell, and rostral pole. In order to gain a more comprehensive understanding of how afferents are distributed relative to these subterritories, immunohistochemical detection of retrogradely transported Fluoro-Gold was carried out following iontophoretic injections intended to involve selectively one of the subterritories. The data revealed that a number of cortical afferents of the medial shell and core originate in separate areas, i.e., the dorsal peduncular, infralimbic, and posterior piriform cortices (to medial shell) and the dorsal prelimbic, anterior agranular insular, anterior cingulate, and perirhinal cortices (to core). The lateral shell and rostral pole are innervated by cortical structures that also project either to the medial shell or core. The orbital, posterior agranular insular, and entorhinal cortices, hippocampus, and basal amygdala were observed to innervate the accumbens in a topographic manner. Following core injections, strong bilateral cortical labeling was observed. Few labeled cortical cells were observed contralaterally following injections in the medial shell. Intermediate numbers of labeled neurons were observed in contralateral cortices following lateral shell injections. Robust subcortical labeling in a variety of structures in the ventral forebrain, lateral hypothalamus, deep temporal lobe, and brainstem was observed after shell injections, particularly those that involved the caudal dorsomedial extremity of the shell, i.e., its "septal pole." Selective ipsilateral labeling of subcortical structures in the basal ganglia circuitry was observed following injections in the core and, to a lesser extent, lateral shell. It was concluded that a number of afferent systems exhibit varying degrees of segregation with respect to the accumbal subterritories.

Afferent Pathways↗
PubMed1995

Structural differences in the cerebral cortex of healthy female and male subjects: a magnetic resonance imaging study.

There are both reproductive and nonreproductive behavioral differences between men and women. Brain regions involved in determining sexual behavior have been reported to differ between the sexes. Nonreproductive, cognitive functional differences between sexes might be reflected in higher-order cortical structural dimorphisms, which have not previously been studied. We hypothesized that cortical regions involved in verbal behavior (which is sexually dimorphic) would differ between sexes. Using magnetic resonance imaging, we assessed gray matter volumes in several cortical regions in 17 women and 43 men. Women had 23.2% (dorsolateral prefrontal cortex) and 12.8% (superior temporal gyrus) greater gray matter percentages (corrected for overall brain size and age) than men in a language-related cortical region, but not in a more visuospatially related cortical region. These data seem to establish sexually dimorphic structural differences in the cerebral cortex, consistent with prior cerebral blood flow reports.

Adult↗
PubMed1995

Structural basis of cortical synchronization. II. Effects of cortical lesions.

1. To understand the structural basis of the different types of interhemispheric synchronizations described in the preceding paper, we made sections of the corpus callosum and lesions of extrastriate cortex. We measured the effects of such operations on the frequency of encounter, width and strength of T, C, and H peaks in cross-correlation histograms computed from single-unit and multiunit recordings from areas 17-18 of opposite cortical hemispheres in the cat. 2. Sectioning of the corpus callosum led to a complete abolition of T and C couplings and a strong reduction of encounter rate and strength of H coupling. A section limited to the posterior half of the corpus callosum abolished T and C couplings completely. This suggests that T and C couplings are mediated by the direct reciprocal connections between visual cortical areas circulating through the posterior part of the corpus callosum. 3. The encounter rate of H peaks depended on the extent of the callosal cut. Larger lesions gave a more pronounced reduction of the number of H peaks. From this observation we conclude that H peaks are at least partially mediated by polysynaptic pathways involving widely distributed cortical regions. 4. Extensive lesions of extrastriate cortex were made by aspiration of the gray matter or injections of ibotenic acid. These lesions removed the direct inputs from cortical areas sending ipsilateral as well as contralateral inputs to the area 17-18 border region. Encounter rate and coupling strength of C and H peaks were decreased, whereas little effect was observed on T peaks. 5. These results demonstrate that all types of interhemispheric synchronization are mediated by corticocortical connections and that T and C peaks are generated by reciprocal connections between areas 17 and 18 of each hemisphere. Feedback connections play a role in mediating or facilitating the C and H types of interhemispheric synchronization.

Animals↗
PubMed1991

Expression of c-fos mRNA in rat brain after intracerebroventricular administration of corticotropin-releasing hormone.

Expression of the proto-oncogene c-fos is known to increase in rat brain following various types of seizures. Measuring c-fos mRNA or protein levels was shown to be a good cellular marker for neurons activated during central nervous system (CNS) excitation. In this study, we used in situ hybridization analysis of c-fos mRNA to determine brain regions activated by a peptide that has been closely linked to stress responsivity and kindling-like seizure activity. Corticotropin-releasing hormone (CRH) was injected into the left lateral ventricle of rats and produced the late onset of seizures between 1.5-5 h after its administration. Rats were sacrificed at various time points after the administration of CRH or sterile water, and c-fos mRNA levels were determined. In the preseizure state, CRH increased c-fos unilaterally in several cerebral cortical structures (most prominently in the dorsal endopiriform nucleus and in the piriform and insular cortices). CRH-induced seizures increased c-fos bilaterally in the same cortical regions, and in addition, in the hippocampus and olfactory bulb. The data are congruous with the hypothesis that intracerebroventricularly (i.c.v.) administered CRH elicits a rapid kindling-like response.

Animals↗
PubMed2004

Prefrontal transcranial magnetic stimulation produces intensity-dependent EEG responses in humans.

The reactivity of the prefrontal cortex (PFC) was studied by measuring electroencephalographic (EEG) responses to transcranial magnetic stimulation (TMS) with different stimulus intensities. Focal TMS at intensities of 60%, 80%, 100%, and 120% of the motor threshold was delivered to the left middle frontal gyrus identified individually from magnetic resonance images (MRI) in seven healthy subjects. EEG was simultaneously recorded with 60 scalp electrodes. Stimulation evoked clear responses at all intensities. Left prefrontal TMS evoked an averaged EEG response consisting of five deflections at 27 +/- 3 ms (peak I), 39 +/- 3 ms (II), 52 +/- 7 ms (III), 105 +/- 14 ms (IV), and 193 +/- 15 ms (V) at the Fz/FCz electrodes. The slope of the almost linear dependence of the overall response on stimulus intensity varied with latency. Potential distributions were relatively similar for the four intensities, suggesting that the same cortical structures may be activated. Intensity dependence function to TMS may be an indicator of cortical activation in humans.

Adult↗
PubMed2003

Motor and parietal cortical areas both underlie kinaesthesia.

Tendon vibration has long been known to evoke perception of illusory movements through activation of muscle spindle primary endings. Few studies, however, have dealt with the cortical processes resulting in these kinaesthetic illusions. We conceived an fMRI experiment to investigate the cortical structures taking part in these illusory perceptions. Since muscle spindle afferents project onto different cortical areas involved in motor control it was necessary to discriminate between activation related to sensory processes and activation related to perceptual processes. To this end, we designed and compared different conditions. In two illusion conditions, covibration at different frequencies of the tendons of the right wrist flexor and extensor muscle groups evoked perception of slow or fast illusory movements. In a no illusion condition, covibration at the same frequency of the tendons of these antagonist muscle groups did not evoke a sensation of movement. Results showed activation of most cortical areas involved in sensorimotor control in both illusion conditions. However, in most areas, activation tended to be larger when the movement perceived was faster. In the no illusion condition, motor and premotor areas were little or not activated. Specific contrasts showed that perception of an illusory movement was specifically related to activation in the left premotor, sensorimotor, and parietal cortices as well as in bilateral supplementary motor and cingulate motor areas. We conclude that activation in motor as well as in parietal areas is necessary for a kinaesthetic sensation to arise.

Adult↗
PubMed1983

Regional differences in vascular autoregulation in the rat brain in severe insulin-induced hypoglycemia.

The present experiments were undertaken to determine if loss of vascular autoregulation during severe hypoglycemia shows regional differences that could help to explain the localization of hypoglycemic cell damage. Artificially ventilated rats (70% N2O) were subjected to a 30-min insulin-induced hypoglycemic coma (with cessation of EEG activity), with mean arterial blood pressure being maintained at 140, 120, 100, and 80 mm Hg. After 30 min of hypoglycemia, local cerebral blood flow (CBF) in 25 brain structures was measured autoradiographically with a [14C]iodoantipyrine technique. Since local CBF values did not differ between the 120 and the 100 mm Hg groups, the animals of these groups were pooled (110 mm Hg group). The results showed that at a blood pressure of 140 mm Hg, CBF was increased in 22 of 25 structures analyzed, the maximal values approximating 300% of control. At 110 mm Hg, cerebral cortical structures had CBF values that were either decreased, normal, or slightly increased; however, many subcortical structures (and cerebellum) showed markedly increased flow rates. Although a lowering of blood pressure to 80 mm Hg usually further reduced flow rates, some of these latter structures also had well-maintained CBF values at that pressure. Thus, there were large interstructural variations of local CBF at any of the pressures examined. Analysis of the pressure-flow relationship showed loss of autoregulation in some structures, whereas others had remarkably well-preserved CBF values at low pressures. The results indicate that during severe hypoglycemia, even relatively moderate arterial hypotension may add a circulatory insult to the primary one, and they strongly suggest that any such insult affects some brain structures more than others.

Animals↗
PubMed2001

Genetic influences on brain structure.

Here we report on detailed three-dimensional maps revealing how brain structure is influenced by individual genetic differences. A genetic continuum was detected in which brain structure was increasingly similar in subjects with increasing genetic affinity. Genetic factors significantly influenced cortical structure in Broca's and Wernicke's language areas, as well as frontal brain regions (r2(MZ) > 0.8, p < 0.05). Preliminary correlations were performed suggesting that frontal gray matter differences may be linked to Spearman's g, which measures successful test performance across multiple cognitive domains (p < 0.05). These genetic brain maps reveal how genes determine individual differences, and may shed light on the heritability of cognitive and linguistic skills, as well as genetic liability for diseases that affect the human cortex.

Adult↗
PubMed1980

In vitro autoradiography of opiate receptors in rat brain suggests loci of "opiatergic" pathways.

Slide-mounted sections of unfixed frozen rat brain can be labeled in vitro with [3H]naloxone to show the mu-like ligand selectivity characterized in previous studies. We have developed an autoradiographic technique using hot paraformaldehyde vapors to prevent diffusion of ligands with reversible binding. Resolution at the light level is sufficient to detect concordance between receptor patterns and terminal fields of axonal projections marked by tract-tracing techniques. The opiate receptor distribution suggests the existence of widespread intrinsic and several longer multisynaptic "opiatergic pathways within sensory and limbic circuits. One multisynaptic pathway may link olfactory structures with limbic circuits in the amygdala and habenula. Another may lie in limbic cortical structures. Opiate receptors are numerous also in sensory systems, and within primary sensory nuclei (visual, auditory, olfactory, somatic) they are found superficially in laminated structures. Together, the opiate receptors are well placed to control incoming sensory and subsequent limbic information processing.

Animals↗