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PubMed1996

Cortical structure and function in euglenoids with reference to trypanosomes, ciliates, and dinoflagellates.

The membrane skeletal complex (cortex) of euglenoids generates and maintains cell form. In this review we summarize structural, biochemical, physiological, and molecular studies on the euglenoid membrane skeleton, focusing specifically on four principal components: the plasma membrane, a submembrane layer (epiplasm), cisternae of the endoplasmic reticulum, and microtubules. The data from euglenoids are compared with findings from representative organisms of three other protist groups: the trypanosomes, ciliates, and dinoflagellates. Although there are significant differences in cell form and phylogenetic affinities among these groups, there are also many similarities in the organization and possibly the function of their cortical components. For example, an epiplasmic (membrane skeletal) layer is widely used for adding strength and rigidity to the cell surface. The ER/alveolus/amphiesmal vesicle may function in calcium storage and regulation, and in mediating assembly of surface plates. GPI-linked variable surface antigens are characteristic of both ciliates and the unrelated trypanosomatids. Microtubules are ubiquitous, and cortices in trypanosomes may relay exclusively on microtubules and microtubule-associated proteins for maintaining cell form. Also, in agreement with previous suggestions, there is an apparent preservation of many cortical structures during cell duplication. In three of the four groups there is convincing evidence that part or all of the parental cortex persists during cytokinesis, thereby producing mosaics or chimeras consisting of both inherited and newly synthesized cortical components.

Animals↗
PubMed2001

Simultaneous modulation of retrieval by dopaminergic D(1), beta-noradrenergic, serotonergic-1A and cholinergic muscarinic receptors in cortical structures of the rat.

Retrieval of inhibitory avoidance has been recently shown to require intact glutamate receptors, protein kinases A and C and mitogen-activated protein kinase in the CA1 region of the rat hippocampus and in the entorhinal, posterior parietal and anterior cingulate cortex. These enzymatic activities are known to be modulated by dopamine D(1), beta-noradrenergic, 5HT1A and cholinergic muscarinic receptors. Here we study the effect on retrieval of this task of well-known agonists and antagonists of these receptors infused in the same brain cortical regions and into the basolateral amygdala, in rats. The drugs used were SKF38393 (D(1) agonist), noradrenaline, 8-HO-DPAT (5HT1A agonist), oxotremorine (muscarinic agonist), SCH23390 (D(1) antagonist), timolol (beta antagonist), NAN-190 (5HT1A antagonist) and scopolamine (muscarinic antagonist). All were studied at two different dose levels. The localised infusion of SKF38393, noradrenaline, NAN-190 and oxotremorine into any of the cortical structures mentioned 10 min prior to a 24-h retention test session of one-trial step-down inhibitory avoidance enhanced retention test performance. SCH2330, timolol, 8-HO-DPAT and scopolamine hindered retention test performance. In the basolateral amygdala only an enhancing effect of noradrenaline and an inhibitory effect of timolol were seen. Three hours after the infusions, retention test performance returned to normal in all cases. None of the treatments affected locomotion or rearing in an open field or behaviour in the elevated plus maze. Therefore, their effects on retention testing can be attributed to an influence on retrieval. In conclusion, memory retrieval of this apparently simple task requires the participation of CA1, entorhinal, posterior parietal and anterior cingulate cortex, and is strongly modulated by, dopaminergic D(1), beta-noradrenergic, muscarinic cholinergic and 5HT1A receptors in the four areas. The first three types of receptor enhance, and the latter inhibits, retrieval. Only beta-adrenoceptors appears to be involved in the modulation of retrieval of this task by the amygdala. The results bear on the well-known influence of emotion and mood on retrieval, and indicate that this involves many areas of the brain simultaneously. In addition, the results point to similarities and differences between the modulatory mechanisms that affect retrieval and those involved in the consolidation of the same task.

Amygdala↗
PubMed2004

Anterior spinal arthrodesis with structural cortical allografts and instrumentation for spine tumor surgery.

STUDY DESIGN: The authors report on anterior vertebral reconstruction following tumor resection with use of fresh-frozen, cortical, long-segment allografts prepared from diaphyseal sections of long bones. A retrospective analysis of clinical outcomes is presented. OBJECTIVE: To analyze the results following the use of cortical allografts in the treatment of spine tumors. SUMMARY OF BACKGROUND DATA: Metastatic disease and primary spinal bone tumors may result in progressive vertebral collapse, instability, deformity, pain, and neurologic deficit. Controversy as to the appropriate type of anterior reconstruction and/or graft material persists. METHODS: From 1995 until 2001, 30 patients with primary spinal bone tumors or metastases to the spine were treated by anterior vertebral reconstruction with fresh-frozen cortical bone allografts. Grafts were used in combination with anterior and posterior instrumentation. RESULTS: The median survival was 14 months. Ninety-three percent of all allografts were radiographically incorporated as early as 6 months after surgery in spite of adjuvant chemotherapy and radiation therapy. Fourteen patients (46%) had intraoperative or postoperative complications. Two patients underwent revision surgery for local recurrence. There were no allograft infections, fractures, or collapse. CONCLUSION: Anterior column reconstruction with structural cortical allografts proved to be a reliable technique in patients with spine tumors. Postoperative complications can often be successfully managed.

Adolescent↗
PubMedDate not supplied

Relationships between human auditory cortical structure and function.

The human auditory cortex comprises multiple areas, largely distributed across the supratemporal plane, but the precise number and configuration of auditory areas and their functional significance have not yet been clearly established. In this paper, we discuss recent research concerning architectonic and functional organisation within the human auditory cortex, as well as architectonic and neurophysiological studies in non-human species, which can provide a broad conceptual framework for interpreting functional specialisation in humans. We review the pattern in human auditory cortex of the functional responses to various acoustic cues, such as frequency, pitch, sound level, temporal variation, motion and spatial location, and we discuss their correspondence to what is known about the organisation of the auditory cortex in other primates. There is some neuroimaging evidence of multiple tonotopically organised fields in humans and of functional specialisations of the fields in the processing of different sound features. It is thought that the primary area, on Heschl's gyrus, may have a larger involvement in processing basic sound features, such as frequency and level, and that posterior non-primary areas on the planum temporale may play a larger role in processing more spectrotemporally complex sounds. Ways in which current knowledge of auditory cortical organisation and different data analysis approaches may benefit future functional neuroimaging studies which seek to link auditory cortical structure and function are discussed.

Animals↗
PubMed1994

Neonatal frontal cortical lesions in rats alter cortical structure and connectivity.

Rats were given frontal cortical lesions at day 1 or 10 of life. Later, as adults, they were either: (1) processed with Golgi-Cox in order to analyze cortical dendritic arborization; (2) given injections of True Blue into the parietal or visual cortex, or (3) given injections of [3H]leucine into the substantia nigra. An additional group of normal rats were given injections of fluorescent dyes into the cortex on day 4 or 10 of life. The main findings were that (1) adult hemispheres with day 10 lesions had greater dendritic arbor than normal hemispheres, (2) adult hemispheres with day 1 lesions had reduced dendritic branching relative to normal hemispheres, (3) adult rats with day 10 lesions had no obvious abnormalities in cortical connections, (4) adult rats with day 1 lesions had abnormal thalamo-cortical, amygdalo-cortical, and nigro-cortical connections, and (5) many of these abnormal connections were present in the brains of 4-day-old normal rats. Since the 'abnormal' connections in the very early frontal operates were present in day 4 animals, it appears that they result from the failure of exuberant connections to retract after the lesions. The increased dendritic growth in day 10 operates does not appear related to qualitative changes in cortical afferents or efferents and may related to increased intrinsic cortical connectivity. Since rats with day 10 lesions have previously been shown to exhibit significant recovery of function, it is possible that the increased dendritic arborization is supporting the functional restitution.

Aging↗
PubMed2000

Involvement of cerebral cortical structures in the classical conditioning of eyelid responses in rabbits.

The classical conditioning of the eyelid motor system in alert behaving rabbits has been used to study the expression of Fos in the hippocampus, and in the occipital, parietal, piriform and temporal cortices. Animals were classically conditioned with both delay and trace conditioning paradigms. As conditioned stimulus, both short and long (20 and 100 ms) tones (600 Hz, 90 dB) or short, weak (20 ms, 1kg/cm(2)) air puffs were used. The unconditioned stimulus was always a long, strong (100 ms, 3 kg/cm(2)) air puff that started 250-270 ms after the onset of the conditioned stimulus. The expression of Fos was significantly increased after both delayed and trace conditioning in the hippocampus, and in the parietal and piriform cortices contralateral to the unconditioned stimulus presentation side, compared with equivalent ipsilateral structures in conditioned animals, or with Fos production in the same contralateral structures in pseudo-conditioned and control animals. Fos expression in some cortical sites was specific to tone versus air puff stimuli when used as conditioned stimulus. Thus, Fos expression was significantly increased in the contralateral temporal lobe when tones were used as conditioned stimulus, for both delayed and trace conditioning paradigms, but not when animals were conditioned to short, weak air puffs. The present results indicate a specific Fos activation in several cerebral cortical structures during associative eyelid conditioning.

Animals↗
PubMed2000

The laminar pattern of connections between prefrontal and anterior temporal cortices in the Rhesus monkey is related to cortical structure and function.

The laminar pattern of axonal termination from prefrontal (caudal orbitofrontal, rostral orbitofrontal and lateral areas) to anterior temporal areas (entorhinal cortex, perirhinal cortex and area TE) and from temporal to prefrontal areas was investigated with the aid of anterograde tracers. Both regions are characterized by structural heterogeneity, and include agranular, dysgranular and granular cortical types, denoting, respectively, the absence, incipience and presence of granular layer 4. In addition, both the prefrontal and anterior temporal cortices are composed of areas that have related though specialized functions. The pattern of cortical axonal termination was associated with both the structural type of the cortex of origin and the structure of the destination cortex. Thus, efferent fibers from a single origin in either prefrontal or anterior temporal cortex terminated in different patterns depending on their target area. Conversely, axons terminated in different patterns in a single target area, prefrontal or anterior temporal, depending on their area of origin. Projections from agranular or dysgranular type cortices (e.g. medial temporal areas and caudal orbitofrontal areas) terminated mostly in the upper layers of granular cortices (e.g. area TE and lateral prefrontal areas), and projections from granular cortices terminated mostly in the deep layers of agranular or dys- granular cortices. A robust projection from dysgranular orbitofrontal areas terminated in the deep layers of the agranular entorhinal cortex. Projections from prefrontal areas to area TE terminated in the upper layers, and may facilitate focused attention on behaviorally relevant stimuli processed through reciprocal pathways between prefrontal and temporal cortices.

Animals↗
PubMed1986

Neurogenesis in reptilian cortical structures: 3H-thymidine autoradiographic analysis.

Histogenesis was studied in forebrain cortical areas of two reptiles, Emys orbicularis and Lacerta trilineata, by using tritiated thymidine autoradiography. Four areas were considered: the dorsomedial, the general (dorsal), and the lateral cortices, and the dorsal ventricular ridge (DVR). The bulk of neurogenesis in these four pallial fields proceeds within a short period of 8-9 days, between developmental stages 15 and 18 in Emys and stages 32-34 in Lacerta. Lateral-to-medial as well as anterior-to-posterior tangential gradients of histogenesis are present in both species. Radial neurogenetic gradients are directed from outside to inside, except in the medial cortex of lizards, where no radial gradient is seen. This pattern of histogenesis in the cortex of turtles and lizards is comparable to that in mammals in terms of timing and tangential, areal variations. It might represent a "common denominator" of cortical histogenesis. However, in contrast to the mammalian cortex, which develops according to an inside to outside, "inverted" pattern, radial neurogenesis in the cortex of turtles and lizards follows an outside-to-inside gradient. These observations suggest that the inside-out gradient of cortical neurogenesis has been acquired during evolution of the synapsid radiation from stem reptiles to mammals, and that it may be related to the development of radial cortical architectonics.

Animals↗
PubMed2026

Cerebral Cortical Structural Variation and General Cognitive Ability: Evidence From Mendelian Randomization.

Understanding the cortical architecture underlying individual differences in general cognitive ability (GCA) remains a central question in cognitive neuroscience. Prior work has established associations between global brain size and GCA, yet the regional effects and directionality of these relationships remain debated. Using a genetically informed cortical parcellation in 11,289 UK Biobank participants, we examined associations between cortical surface area (SA), cortical thickness (CT), and GCA measured via verbal-numerical reasoning. Total SA showed a robust positive association with GCA. At the regional level, dorsolateral prefrontal and superior temporal SA exhibited the strongest positive associations, which persisted after adjustment for global SA. In contrast, CT showed comparatively modest associations. Using Mendelian randomization (MR) with genome-wide significant genetic instruments, we observed evidence consistent with a bidirectional relationship between total SA and GCA. At the regional level, dorsolateral prefrontal and temporal SA demonstrated evidence of MR-inferred directional effects on GCA, while GCA showed evidence of MR-inferred directional effects on total SA and perisylvian thickness. These findings support a polyregional SA architecture underlying GCA, with prominent contributions from prefrontal and temporal association cortices. Our results refine global brain-GCA models and highlight the value of genetically informed parcellation for identifying regional cortical contributions.

Humans↗
PubMed1999

Regulation of cortical structure by the ezrin-radixin-moesin protein family.

Molecules involved in ERM (ezrin-radixin-moesin) based attachment of membrane proteins to the cortical cytoskeleton in cell surface structures have been identified. In lymphocytes, a direct interaction is seen with extracellular matrix receptors and intercellular adhesion molecules. In polarized epithelial cells, an adaptor molecule named EBP50 provides a bridge between the amino-terminal domain of ezrin and the cytoplasmic regions of plasma membrane proteins, including the cystic fibrosis transmembrane conductance regulator (CFTR) and the beta2 adrenergic receptor. ERM proteins are conformationally regulated - binding sites for EBP50 and F actin are masked in the dormant molecules and activation leads to exposure of these sites. The mechanism of activation, however, remains to be fully elucidated. ERM proteins also play a role in the Rho and Rac signaling pathways: activated ERM proteins can dissociate Rho-GDI (GDP dissociation inhibitor) from Rho and thereby activate Rho-dependent pathways.

Blood Proteins↗
PubMed2006

Cortical surface-based analysis of 18F-FDG PET: measured metabolic abnormalities in schizophrenia are affected by cortical structural abnormalities.

The purpose of the study is to propose a new framework for surface-based statistical parametric mapping of PET images using MRI-based cortical surface analysis, including partial volume correction, intensity normalization and spatial normalization on the cortical surface. Maximum PET intensities along the path between inner and outer layer of the cortical gray matter are mapped onto the cortical surface to generate a metabolic activity surface map. For the partial volume correction, the metabolic activity surface map was divided by the partial volume effect map. The regional metabolic activity was normalized by the global activity iteratively calculated at the surface nodes, statistically independent of the group, as measured by F statistics. After surface-based spatial normalization, a statistical evaluation of both cortical thickness and cortical metabolic activity was conducted on the normalized surfaces of 16 patients with schizophrenia and 16 age- and gender-matched healthy controls. The patients with schizophrenia were found to have significant cortical thinning in the temporal and inferior frontal cortices. Accordingly, their PET imaging was significantly affected by the partial volume effect, indicating that partial volume correction could change the statistical results. After correction of the partial volume effects, the patients showed hyperactivity in the temporal cortex, whereas hypoactivity in the prefrontal cortex, predominantly in the left hemisphere. Our results demonstrate that anatomical factors affect an analysis for functional data from the PET, and therefore the importance of combining anatomy and function in the analysis of imaging data for schizophrenia should be considered.

Adult↗
PubMed1971

Shift in binocular disparity causes compensatory change in the cortical structure of kittens.

Kittens were raised with prisms in front of their eyes which introduced a vertical disparity. At 4 months of age the disparity necessary to maximally stimulate a sample of binocular cortical cells was determined. The distribution of optimal disparities was abnormal, and shifted in a direction which would tend to compensate for the prism-induced disparity.

Adaptation, Ocular↗
PubMedDate not supplied

[The phasic relations between the rhythmic activities of the rabbit cortical structures at different frequencies of stimulation of the midbrain reticular formation].

Phase shifts between the rhythmical activity of the hippocampus (CA1), somatosensory, motor and visual areas of the neocortex in the delta-, theta- and alpha-bands were studied during electrostimulation of the mesencephalic reticular formation with different frequencies. It was found that increasing stimulation frequency resulted in nonlinear decrease of the phase shifts in the theta-band between recordings which included the visual cortical area, and increase of the phase shifts between the theta-rhythm, recorded in the hippocampus, somatosensory and motor cortical areas. In the delta-band increase of the phase shifts was observed only in the pairs of recordings from the last-mentioned group of structures at stimulation frequencies more than 200 1/sec. Phase shifts in the alpha-rhythm between the cortical recordings varied at different stimulation frequencies. Reliable changes of the alpha-rhythm phase shifts were observed during stimulation with the frequency 60-200 1/sec between recordings from the hippocampus, motor and somatosensory areas, and at 500-700 1/sec--in the pairs of recordings which included the visual cortical area.

Animals↗
PubMedDate not supplied

Cerebral cartography--a method for visualizing cortical structures.

We present a method for visualizing the human cortex on one planar map. The data are taken from a 3D MRI study. Ray tracing with non-parallel rays is used to project the cortical relief onto a non-planar projection surface, which is in turn mapped onto the plane by cartographical projection. Two modifications of the method are proposed: the spherical mapping uses a sphere as the projection surface; the model-based mapping uses an analytically defined model of the scalp to generate the normal vectors. The cerebral cartography can be used for example for producing anatomical reference maps on which EEG measurement data can be superimposed.

Algorithms↗
PubMed2004

A gammaGT-AT1A receptor transgene protects renal cortical structure in AT1 receptor-deficient mice.

To understand the physiological role of angiotensin type 1 (AT(1)) receptors in the proximal tubule of the kidney, we generated a transgenic mouse line in which the major murine AT(1) receptor isoform, AT(1A), was expressed under the control of the P1 portion of the gamma-glutamyl transpeptidase (gammaGT) promoter. In transgenic mice, this promoter has been shown to confer cell-specific expression in epithelial cells of the renal proximal tubule. To avoid random integration of multiple copies of the transgene, we used gene targeting to produce mice with a single-copy transgene insertion at the hypoxanthine phosphoribosyl transferase (Hprt) locus on the X chromosome. The physiological effects of the gammaGT-AT(1A) transgene were examined on a wild-type background and in mice with targeted disruption of one or both of the murine AT(1) receptor genes (Agtr1a and Agtr1b). On all three backgrounds, gammaGT-AT(1A) transgenic mice were healthy and viable. On the wild-type background, the presence of the transgene did not affect development, blood pressure, or kidney structure. Despite relatively low levels of expression in the proximal tubule, the transgene blunted the increase in renin expression typically seen in AT(1)-deficient mice and partially rescued the kidney phenotype associated with Agtr1a(-/-)Agtr1b(-/-) mice, significantly reducing cortical cyst formation by more than threefold. However, these low levels of cell-specific expression of AT(1) receptors in the renal proximal tubule did not increase the low blood pressures or abolish sodium sensitivity, which are characteristic of AT(1) receptor-deficient mice. Although our studies do not clearly identify a role for AT(1) receptors in the proximal tubules of the kidney in blood pressure homeostasis, they support a major role for these receptors in modulating renin expression and in maintaining structural integrity of the renal cortex.

Animals↗
PubMed1999

Disorganization of cortical structure and the brain tumors.

In the course of histopathological investigation of the temporal lobe sections, selected from 63 patients treated surgically for intractable epilepsy and finally presented with primary temporal tumors, we found 12 cases expressed both neoplastic process' and developmental disorders. The temporal mass lesions consisting of neuro-glial or pure glial tumors were associated with some developmental abnormalities such as cortical dysplasia, neuronal heterotopias and additional cortical neoplastic nodules. The possible "dual pathology" concerning these lesions are discussed in this paper.

Brain Neoplasms↗
PubMed2000

[Localization of attention related cortical structures by evoked potentials].

Attention is an ambiguous concept, difficult to direct implementation in neurophysiological studies. The paper presents application of the Continuous Attention Test (CAT) items as stimuli in event related potential (ERP) studies on attention. Stimuli with high demand of attention result in enlarged N1 component in occipital derivations. Spatial analysis revealed increased positivity in frontal derivations. Three-dimensional image of cortical current density by means of Low Resolution Electromagnetic Tomography (LORETA) revealed sources of N1 component in occipital, parietal and postero-temporal derivations with the maximal current value at 17 Brodmann area. After target stimuli increase of current density in frontal derivations was observed, with the maximal value in the left 9 Brodmann area.

Attention↗