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PubMed2005

Audiogenic seizures associated with a cortical spreading depression wave suppress spike-wave discharges in rats.

To study the role of the cortex and sub-cortical structures in the generation of epileptic spike-wave discharges in more detail, cortical and striatal activity was eliminated by the induction of spreading depression in a non-invasive way. EEG and DC potentials were recorded from the cortex and striatum of WAG/Rij rats. Several of these rats show two forms of generalised epilepsy: spontaneously occurring non-convulsive absence seizures, together with convulsive audiogenic seizures. The latter can be evoked by a brief sound stimulation, provoking a fit of wild running, which is regarded as the first phase of an audiogenic seizure. In a majority of fits the cortical DC potential does not show main changes, while the spontaneously occurring spike-wave discharges are briefly suppressed for some minutes. In a minority of fits, however, audiogenic seizures are associated with a spreading depression wave, clearly expressed in the cortical DC potential. This wave is bilaterally initiated in the cortex and propagates to the caudate nucleus of the striatum. In these cases spontaneously occurring spike-wave discharges are fully suppressed for about 1 h. It is suggested that cortical spreading depression, triggered by a short audiogenic seizure, induces a long-lasting suppression of spike-wave discharges. These results are in line with the concept that spike-wave discharges are originally initiated in the cortex, as proposed by the 'cortical focus' theory. The precise role of the striatum remains less clear, although this structure seems not to play a pivotal role in spike-wave generation.

Acoustic Stimulation↗
PubMed1980

An intermittent somatostatin-immunoreactivity in the cortex and basal ganglia of the rat.

Using light microscopic immunohistochemistry, somatostatin-positive structures were observed in the cortex of the rat. These structures, including cells and fibers, are widely distributed in all cortical laminae and are also found in the basal ganglia. The positive results were obtained exclusively in two groups of animals sacrificed during two different months of two subsequent years. The reason for this variability in the immunocytochemical stainability of cortical structures remains enigmatic.

Animals↗
PubMed1996

Hemispheric specialization for discourse reports of emotional experiences: relationships to demographic, neurological, and perceptual variables.

This study examined hemispheric specialization for discourse reports of emotional and nonemotional experience in 16 right-brain-damaged (RBD), 16 left-brain-damaged (LBD), and 16 demographically-matched normal control (NC) right-handed adults. Patient groups did not differ on etiology, months post-CVA onset, and intrahemispheric lesion location. Subjects were requested to produce monologues about positive and negative emotional and nonemotional experiences. The lexical content of written transcriptions of these monologues was later rated for "emotionality" by naive judges. Overall, RBDs described experiences with less emotional intensity than did NCs and LBDs, providing support for right hemisphere involvement in lexical emotion. Although the RBDs in the current study demonstrated similar patterns of deficits in a prior study [9] on tasks involving lexical emotional perception, there were no significant relationships between the current measures of emotional expression and the previous measures of emotional perception. Finally, the expression and the perception data were examined with respect to intrahemispheric factors. Among the brain-damaged subjects, subcortical structures were more involved in reports of emotional experience, and cortical structures were more involved in the perception of emotion.

Age Factors↗
PubMed2001

Localization of hemiachromatopsia.

Impaired color perception with relative preservation of form vision (achromatopsia) caused by cerebral lesions was first described over a century ago. However, for many years some researchers questioned the existence of an area of cerebral cortex apart from the primary visual cortex specialized in color processing. The development of sophisticated structural and functional neuroimaging techniques has allowed verification of the cortical structures important in color perception. We describe a case of a patient with impaired color perception in one hemifield of vision (hemiachromatopsia) and compare the localization of the lesion with previous cases described in the literature. These cases show that lesions of the ventromedial occipital cortex can impair color perception and leave form vision intact.

Aged↗
PubMed2001

Intracerebral event-related potentials to subthreshold target stimuli.

OBJECTIVES: Event-related potentials (ERPs) elicited by subthreshold visual stimuli were recorded directly from human frontal and temporal lobe structures to study unconscious perception. METHODS: Thirteen intractable epileptic patients undergoing depth electrode recordings prior to their surgical treatment participated in the study. An original method of modified visual oddball paradigm with supraliminal and subliminal stimuli was applied, and the averaged responses to both kinds of stimuli were subsequently compared. RESULTS: The results clearly prove that, at least from an electrophysiological viewpoint, the mechanism of unaware processing of visual stimuli in the human brain does not differ substantially from the aware processing. Finding the subliminal P3 waveform in a number of cortical structures (hippocampus and parahippocampal gyrus bilaterally, and left-sided mesiofrontal, orbitofrontal and lateral temporal cortex) indicates their involvement in unconscious processing, in spite of the fact that typical large-scale neurocognitive networks are not completely activated. The absence of activation consistently observed bilaterally in dorsolateral prefrontal cortices, in connection with right-sided cortical frontal lobe structures and right-sided lateral temporal neocortex in unconscious perception, supports the importance of these structures for the awareness of visual stimuli. The proof of the significantly faster unaware information processing represents another distinctive feature of implicit visual perception. CONCLUSIONS: Based on the presented findings and comparisons with the results of previous ERP, functional magnetic resonance imaging, positron emission tomography, and clinical neuropsychological studies, a crucial role of the large-scale neural system for conscious experience of perception is suggested, which is distributed extensively among the dorsal posterior association areas and the prefrontal cortex, with the dominant part being that of the right hemisphere.

Adult↗
PubMed1997

On the significance of temporally structured activity in the dorsal lateral geniculate nucleus (LGN).

Higher organisms perceive information about external or internal physical or chemical stimuli with specialized sensors that encode characteristics of that stimulus by a train of action potentials. Usually, the location and modality of the stimulus is represented by the location and specificity of the receptor and the intensity of the stimulus and its temporal modulation is thought to be encoded by the instantaneous firing rate. Recent studies have shown that, primarily in cortical structures, special features of a stimulus also are represented in the temporal pattern of spike activity. Typical attributes of this time structure are oscillatory patterns of activity and synchronous discharges in spatially distributed neurons that respond to inputs evoked by a coherent object. The origin and functional significance of this kind of activity is less clear. Cortical, subcortical and even very peripheral sources seem to be involved. Most of the relevant studies were devoted to the mammalian visual system and cortical findings on temporally structured activity were reviewed recently (Eckhorn, 1994, Progr. Brain Res., Vol. 102, pp. 405-426; Singer and Gray, 1995, Annu. Rev. Neurosci., Vol. 18, pp. 555-586). Therefore, this article is designed to give an overview, especially of those studies concerned with the temporal structure of visual activity in subcortical centers of the primary visual pathway, which are the retina and the dorsal lateral geniculate nucleus (LGN). We discuss the mechanisms that possibly contribute to the generation and modulation of the subcortical activity time structure and we try to relate to each other the subcortical and cortical patterns of sensory activity.

Action Potentials↗
PubMed1994

Postnatal development of argyrophilic nucleolar organizer regions in the mammillary body of undernourished rats.

The effects of undernutrition during pregnancy and/or lactation periods on cortical structures have already been reported. However, its effect on non-cortical areas like the hypothalamic, that participates in the regulation of the autonomic nervous system or food intake, has not been extensively investigated. We studied the postnatal development of the medial mammillary nucleus (hypothalamus) in the rat offspring that had a dietary restriction in utero and during lactation. The argyrophilic nucleolar regions (Ag-NORs), that represent the transcriptional activity of the cell, were quantified in their neurons. No statistically significant differences were found in the results between the control and undernourished groups in the ages studied (7, 14, 21 and 30 days). However, a delay in the neuronal activity of the latter group was observed. A critical period in the development of this nucleus, at about 21 days of age, was also seen in both groups. After this age, the activity levels remained steady.

Animals↗
PubMed1991

Ontogeny of cholecystokinin-like immunoreactivity in the Brazilian opossum brain.

We have studied the anatomical distribution of cholecystokinin-like immunoreactive (CCK-IR) somata and fibers in the brain of the adult and developing Brazilian short-tailed opossum, Monodelphis domestica. Animals ranged in age from the day of birth (1PN) to young adulthood (180PN). A nickel enhanced, avidin-biotin, indirect immunohistochemical technique was used to identify CCK-IR structures. Somata containing CCK immunoreactivity were observed in the cerebral cortex, hippocampus, hypothalamus, thalamus, midbrain, and brainstem in the adult. Cholecystokinin immunoreactive fibers had a wide distribution in the adult Monodelphis brain. The only major region of the brain that did not contain CCK-IR fibers was the cerebellum. The earliest expression of CCK immunoreactivity was found in fibers in the dorsal brainstem of 5-day-old opossum pups. It is possible that the CCK-IR fibers in the brainstem at 5PN are of vagal origin. Cholecystokinin immunoreactive somata were observed in the brainstem on 10PN. The CCK-IR cell bodies observed in the brainstem at 10PN may mark the first expression of CCK-IR elements intrinsic to the brain. A broad spectrum of patterns of onset of CCK expression was observed in the opossum brain. The early occurrence and varied ontogenesis of CCK-IR structures indicates CCK may be involved in the function of a variety of circuits from the brainstem to the cerebral cortex. The early expression of CCK-IR structures in the dorsal brainstem suggests that CCK may modulate feeding behavior in the Monodelphis neonate. Cholecystokinin immunoreactivity in forebrain structures such as the suprachiasmatic nucleus, medial preoptic area, thalamus and cortical structures indicates that CCK may also be involved in circadian rhythmicity, reproductive functions, as well as the state of arousal of the Brazilian opossum. The ontogenic timing of CCK immunoreactivity in specific circuitry also indicates that CCK expression does not occur simultaneously throughout the brain. This pattern of CCK onset may relate to the temporal need for CCK in specific circuits of the central nervous system (CNS) during development.

Aging↗
PubMed1984

Nitrous oxide markedly increases cerebral cortical metabolic rate and blood flow in the goat.

Studies to date on the influence of N2O on cerebral blood flow (CBF) and metabolism in dogs, rodents, and humans have produced conflicting results. In the present study the authors have employed techniques in the awake, freely breathing nonstressed goat that allowed the authors to 1) serially obtain rapidly frozen cerebral cortical biopsy specimens (for labile metabolite assay) and 2) measure changes in cerebral O2 metabolism (CMRO2) and total and regional CBF (rCBF). Thus, with each animal utilized as its own control, the authors studied N2O effects on the above variables. Two determinations of the effects of 1 h of N2O (70% via a mask) on these variables were performed on each animal. Following introduction of N2O, PaCO2 and arterial blood pressure did not change, but arterial epinephrine levels declined over the 60-min period. Total CBF increased in the first 5 min of N2O exposure, reached a maximum of 165% control at 15 min, and then decreased to 143% control at 60 min. rCBF evaluations showed that much of this CBF increase was confined to cerebral cortical structures (188-246% control at 60 min). Over the same period cortical CMRO2 increased to 170% of control. No appreciable changes in the levels of high-energy phosphates or glycolytic intermediates were found at 60 min of N2O. The authors attribute the described changes solely to the presence of N2O and not to sympathoadrenal influences, altered ventilation, or anything related to the experimental preparation, and they conclude that N2O (at least in goats) is associated with a marked cerebral cortical "activation".

Anesthesia, Inhalation↗
PubMed1981

Oculomotor reaction time in dementia reflects degree of cerebral dysfunction.

The effects of diffuse cerebral dysfunction on oculomotor reaction time were assessed in patients with dementia of presumed Alzheimer's etiology and in normal age-matched control subjects. Patients were classified into mild, moderate, and severe groups on the basis of independent neurological, neuropsychological, and neuroradiological ratings for disease severity. Saccadic latencies to targets appearing in parafoveal and near peripheral vision showed significant increases from the normal controls to dementia groups, with each severity subdivision clearly differentiated from the others in terms of mean oculomotor reaction time. These data offer strong evidence for a direct relationship between degree of cortical structural integrity and simple oculomotor reaction time and suggest a higher cortical regulatory role in sensory-motor integration.

Alzheimer Disease↗
PubMed2001

[Involvement of the facial skull in Erdheim-Chester disease].

We report on a patient suffering from Erdheim-Chester-disease (ECD). ECD represents a very rare entity with lipogranulomatosis of mesenchymal origin. The most common radiological manifestation is the involvement of the long bones of the extremities. Here we find sclerosis of the spongiosa combined with a thinning of cortical structures. This often results in a small crack of hyperlucency between corticals and spongiosa. Our case demonstrates an involvement of the craniofacial part of the skull showing sclerosis of the upper jaw bone. This manifestation has not yet been reported in the literature.

Adult↗
PubMed1977

[Structural features of the brain stem reticular formation, hippocampus and limbic region of the cortex].

The paper compares the structural reorganization of reticular formation of the brain stem with the cortical structures of the limbic system--hippocamp and limbic cortex in the mammalian comparative order (a hedgehog, a rabbit, a cat, a dog, a dolphin, a monkey, a man). In all the studied links of the limbico-reticular system the author revealed general regularity: the main trend of a structural development is expressed in the intensification of their structural heterogeneity: nuclei are divided in subnuclei, areas in subareas, layers in sublayers. In all structures these features are expressed more vividly in their phylogenetic new parts. Besides, changes of the brain caudal sections--reticular formation are relatively less expressed than the rostral sections, i.e. hippocamp and limbic cortex.

Animals↗
PubMed1984

Transplantation of various regions of embryonic brain tissue into the brain of adult rats.

Brain tissue from the cortex, midbrain (corpora quadrigemina ) or cerebellum was transplanted into the lateral ventricle or parenchyma of the right brain hemisphere of adult Wistar rats. Brain tissue transplants consisted of undifferentiated matrix cells and few neuroblasts. 30 and 110 days after operation transplants showed good development both in the lateral ventricle and inside parenchyma. They differentiated into organotypical and histotypical structures and cells similar to those formed in the normal development. Cortical structures developed from the cortex tissue, cerebellar structures from the cerebellum tissue, and nuclei white substance of corpora quadrigemina where formed from the midbrain tissue. Nerve and glial cells of transplants are well differentiated, tightly connected with the surrounding nervous tissue of the recipient, and remain viable by the end of the experiment. The immune response of the host to the transplant is not expressed. The behaviour of animals remains normal. The present experiments are the beginning of studies on grafting brain embryonal tissue to mammals with some nonhereditary and hereditary changes of the central nervous system (CNS) for our further investigations.

Animals↗
PubMed1985

Regulation of gonadotrophin function in hemidecorticate rats.

The present review focuses on some aspects of the regulation of gonadotrophin (LH and FSH) and prolactin secretion in rats submitted to hemidecortication (HD). The removal of rhinencephalic and cortical structures induces the following changes: Irregular and erratic estrous cycle; Increase in LH and FSH secretion in the afternoon of proestrus and after uni- or bilateral castration; When hormonal replacement therapy was administered to castrated female rats, the controls needed larger doses of estradiol benzoate (E2) to reduce LH levels than the HD animals, which suggests an increase in the sensitivity of the hypothalamus-hypophysis axis to gonadal steroid negative feedback. When HD was performed during the neonatal period (1-3 days old), an earlier onset of puberty and sexual maturation was observed in both female and male HD rats than in controls. During the puberal evolution the HD male rats showed elevation in plasma testosterone levels, an increase in the testicular response to hCG and also in the number of testicular binding sites to LH and FSH at 38-43 days (before the onset of puberty) and to prolactin (after 60 days). The results suggest that after removal of cortical and subcortical structures (HD), with predominant inhibitory influences, the hypothalamus-hypophysis becomes more sensitive to the LH and FSH releasing mechanisms.

Age Factors↗
PubMedDate not supplied

[The effect of chronic Vagus Nerve Stimulation (VNS) on the central conduction time assessed by multimodal evoked potentials in patients with drug resistant epilepsy: preliminary report].

Changes over time in evoked potentials of various modality (VEP, SSEP and BAEP) were analyzed in 3 patients, submitted to chronic Vagus Nerve Stimulation (VNS) due to drug resistant epilepsy. The aim of a study was to establish which cerebral structures are most prone to change their baseline electrophysiological status in consequence of chronic VNS. Evoked potentials were examined before the Vagus Nerve Stimulator implantation and at arbitrarily defined follow-ups several months after the implantation. Preliminary results obtained in a small group of 3 patients suggest a possible prolongation of the central conduction time in the examined modalities of evoked potentials due to the VNS treatment. A hypothetical mechanism of antiepileptic VNS action might be related to the permanent stimulation of brainstem and cortical structures that limit seizures propagation through hyperpolarisation both at the cortical level and in subcortical structures.

Adult↗
PubMed1987

Cortical mechanisms subserving reaching.

The generation and control of reaching in space is a function of several structures, cortical and subcortical. This paper summarizes some principles of the cortical mechanisms subserving this function, as revealed by recording the impulse activity of neurons in motor cortex and area 5 of the posterior parietal cortex in behaving monkeys. Large populations of neurons in these cortical areas are engaged in reaching. This engagement is early in time; for example, cell activity in the motor cortex begins to change 60-80 ms after target onset, and slightly later in area 5. The time course of cell recruitment in the active population is very similar for reaching movements of equal amplitude directed to different targets. In contrast, the intensity of cell discharge in both motor and parietal cortex is clearly modulated with respect to the direction of reaching. Typically, the firing rate is a cosine function of the direction of the movement in space. An unambiguous distributed code for the direction of reaching exists in neuronal populations in the cortical areas studied. The outcome of this population code can be visualized as a vector in neural space that points in the direction of the upcoming movement.

Animals↗
PubMed2003

Cerebral blood flow in chronic symptomatic mild traumatic brain injury.

Patients with mild traumatic brain injury (MTBI) challenge physicians' skills and test their patience. Their manifold symptomatology is often not supported by objective neurological findings. We sought to compare regional cerebral blood flow (rCBF) between symptomatic subjects with longstanding MTBI and healthy controls, and to examine the correspondence between neuropsychological deficit and rCBF compromise. Twenty-eight clinically symptomatic male subjects with MTBI and twenty matched controls underwent neuropsychological testing and Tc-99m-HMPAO brain SPECT imaging. Neuropsychological test data were used to categorize subjects into sub-groups according to the presumed location of lesions based on their neurobehavioral deficits. Image subtraction comparisons were made between controls, all MTBI subjects and sub-groups. MTBI patients demonstrated regions of hypoperfusion in frontal, pre-frontal and temporal cortices, and sub-cortical structures. Hypoperfusion in 'frontal', 'left posterior' and to a lesser extent 'sub-cortical' sub-groups was concordant with neuropsychological localization. This was not the case for the 'right posterior' group, where no concordance was found. The rCBF is reduced in symptomatic patients with longstanding MTBI and unremarkable structural brain imaging. Although group analysis is appropriate for the generation of statistically significant differences, the clinical application of brain SPECT imaging in MTBI calls for a capability to associate clinical examination, neuropsychological assessment and cerebral perfusion at the individual subject level. Such competence is still to be attained.

Adult↗
PubMed1992

A comparison of glycogen phosphorylase a and cytochrome oxidase histochemical staining in rat brain.

The utility of metabolic markers that index functional neuronal circuits is widely appreciated. The present study asks whether patterns of the metabolic enzyme, active glycogen phosphorylase, parallel those of the neuronal marker, cytochrome oxidase. Fresh frozen rat brain sections (30 microns) were processed for either active glycogen phosphorylase or cytochrome oxidase at each of ten levels of the neuraxis. Although these metabolic markers predominate in different cellular compartments--glycogen phosphorylase in the astrocytic compartment and cytochrome oxidase in the neuronal compartment--the patterns of high, moderate, and low levels of activity for both enzymes were generally parallel. These similarities extended to detailed patterns of heterogeneous staining within structures, in particular, to laminated and modular distribution within cerebral and cerebellar cortical structures. The modular distribution was evident in barrel structures in the cerebral cortex and in parasagittal compartments in the vermis of the cerebellum. Conspicuous differences between the two patterns occurred in white matter, in subcortical grey matter regions such as the nucleus accumbens, diagonal band, amygdala, and globus pallidus, and in the superior olivary nuclei of the brainstem as well as in nonneural structures such as the choroid plexus and ependyma. Discrete patchiness was characteristic of active glycogen phosphorylase distribution in the limbic neuropil of the dentate gyrus and entorhinal cortex. The strong parallels between active glycogen phosphorylase and cytochrome oxidase distribution support the view that glycogen phosphorylase, despite its glial localization, can reflect neuronal metabolic demands.

Animals↗