SEARCH · PubMed Health

Results for “cortex”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources

PubMed1994

Efferents of frontal or occipital cortex grafted into adult rat's motor cortex.

Phaseolus vulgaris leucoagglutinin (PHA-L) was used to examine the efferent connectivity of embryonic (E16) frontal (homotopic) or occipital (heterotopic) neocortical transplants placed into--or in the vicinity of--lesion cavities made in the frontal cortex of adult recipients. Homotopic transplants projected towards the host sensorimotor cortex and, in most cases, into the lateral caudate-putamen (CPu). Heterotopic transplants projected into the anterior cingulate cortex and, in most cases, distributed terminals into the medial CPu. It is suggested that embryonic neocortical tissue placed into a damaged cortical site of an adult recipient develops a pattern of efferents corresponding to its cortical origin.

Animals↗

PubMed1987

Dopaminergic innervation of the primary visual cortex in the rat, and some correlations with human cortex.

Dopaminergic terminals have been identified in the primary visual cortex with three techniques; immunocytochemistry with an anti-dopamine antiserum, retrograde axonal transport techniques using unconjugated wheat germ agglutinin and HPLC determination of catecholamines and metabolites in microdissected sub-regions of occipital cortex in the rat. The results demonstrate a specific dopaminergic innervation, arising from the ventral tegmental area, which is found mainly in laminae VI and V, but with minor innervation also in lamina I. Dopaminergic innervation to adjacent cortical regions is also described. Neurochemical data from post-mortem human material suggests that a similar innervation exists in man. An analysis of the distribution of dopaminergic fibres in relation to the known connections and possible functions of the deep laminae of visual cortex suggests that dopaminergic axons may participate in the corticofugal control of visual afferent pathways.

Aged↗

PubMed1988

Layer V in rat auditory cortex: projections to the inferior colliculus and contralateral cortex.

This study compares the form and distribution within layer V of cells projecting to the inferior colliculus with that of commissural cells of origin in adult rat auditory cortex after horseradish peroxidase injections in the ipsilateral inferior colliculus or auditory cortex. The goal of this work was to determine whether every part of layer V participates equally in both projections, and if the cortical neurons in each pathway were similar. The types of neurons were defined in Golgi-Cox preparations and matched with the profiles of retrogradely labeled cells from architectonically defined cortical area 41. Inferior colliculus and commissural neurons form two populations that differ in their distribution in layer V, in somatic area, and in the form of their apical dendritic arbors. Corticocollicular neurons include the largest pyramidal cells, whose robustly filled apical dendrites ascend into layer II or farther. Commissural cells are smaller and have a more heterogeneous form. Their apical dendrites do not usually extend above layer IV, and a few of these cells may be non-pyramidal. Small pyramidal cells and inverted pyramidal cells project to the opposite cortex, but not to the inferior colliculus. Medium-sized pyramidal cells project in both systems. In addition, certain callosal cells of origin in layers V and III were morphologically similar. More than one-third of the commissural cells originate in the superficial part of layer V, where only 7% of the inferior colliculus projection neurons arise. Most corticocollicular cells lie deeper in layer V, where there are fewer commissural neurons. These findings suggest that the efferent systems projecting to telencephalic and mesencephalic targets are morphologically distinct and spatially segregated in layer V. However, the commissural projection includes similar cells in different cortical layers. The types of these efferent neurons may be more closely related to their target than to their laminar origin.

Animals↗

PubMed2005

Cortical reorganization of hand motor function to primary sensory cortex in hemiparetic patients with a primary motor cortex infarct.

OBJECTIVE: To show cortical reorganization in hemiparetic patients with a primary motor cortex (M1) infarct including the precentral knob by using functional magnetic resonance imaging (fMRI). DESIGN: Case-control. SETTING: Outpatient clinics in the rehabilitation department of a university hospital. PARTICIPANTS: Two stroke patients and 20 control subjects. INTERVENTIONS: By using fMRI, we evaluated the hand motor function of 2 hemiparetic stroke patients, who had made some recovery from complete paralysis of the affected hand, and 20 control subjects. MAIN OUTCOME MEASURES: fMRI was performed by using the blood oxygen level-dependent technique at 1.5 T with a standard head coil. The motor task paradigm consisted of hand grasp-release movements. RESULTS: The contralateral primary sensorimotor cortex was activated by the hand movements of the control subjects and of the unaffected side of the 2 patients. Only the contralateral (infarct side) primary sensory cortex (S1) was activated by the movements of the affected hand of the 2 patients, a result that was not observed in the control subjects or with the unaffected hand in the stroke patients. CONCLUSIONS: The hand motor function associated with the infarcted M1 in our patients was reorganized into the S1. These results suggest cortical reorganization in patients with an M1 infarct.

Adult↗

PubMed2006

Mapping an intrinsic MR property of gray matter in auditory cortex of living humans: a possible marker for primary cortex and hemispheric differences.

Recently, magnetic resonance properties of cerebral gray matter have been spatially mapped--in vivo--over the cortical surface. In one of the first neuroscientific applications of this approach, this study explores what can be learned about auditory cortex in living humans by mapping longitudinal relaxation rate (R1), a property related to myelin content. Gray matter R1 (and thickness) showed repeatable trends, including the following: (1) Regions of high R1 were always found overlapping posteromedial Heschl's gyrus. They also sometimes occurred in planum temporale and never in other parts of the superior temporal lobe. We hypothesize that the high R1 overlapping Heschl's gyrus (which likely indicates dense gray matter myelination) reflects auditory koniocortex (i.e., primary cortex), a heavily myelinated area that shows comparable overlap with the gyrus. High R1 overlapping Heschl's gyrus was identified in every instance suggesting that R1 may ultimately provide a marker for koniocortex in individuals. Such a marker would be significant for auditory neuroimaging, which has no standard means (anatomic or physiologic) for localizing cortical areas in individual subjects. (2) Inter-hemispheric comparisons revealed greater R1 on the left on Heschl's gyrus, planum temporale, superior temporal gyrus and superior temporal sulcus. This asymmetry suggests greater gray matter myelination in left auditory cortex, which may be a substrate for the left hemisphere's specialized processing of speech, language, and rapid acoustic changes. These results indicate that in vivo R1 mapping can provide new insights into the structure of human cortical gray matter and its relation to function.

Adult↗

PubMed2004

A role for right medial prefontal cortex in accurate feeling-of-knowing judgements: evidence from patients with lesions to frontal cortex.

The hypothesis that prefrontal cortex plays a critical role in accurate predictions of episodic memory performance was tested using the feeling-of-knowing (FOK) paradigm. Fourteen patients with a broad spectrum of damage to the frontal cortex and matched controls read sentences and later were tested for recall memory, confidence judgments, and FOK accuracy using as cues the sentences with the final word missing. While frontal patients were impaired at recall and recognition memory, they were able to make accurate confidence judgments about their recall attempts. By contrast, as a group, the patients were markedly impaired in the accuracy of their prospective FOK judgments. Lesion analysis of frontal patients with clear FOK impairment revealed an overlapping region of damage in right medial prefrontal cortex. These findings provide functional and anatomical evidence for a dissociation between recall confidence and prospective memory monitoring and are discussed in terms of familiarity and access theories of FOK predictions.

Adult↗

PubMed2000

Functional plasticity in extrastriate visual cortex following neonatal visual cortex damage and monocular enucleation.

Neonatal lesions of primary visual cortex (areas 17, 18 and 19; VC) in cats lead to significant changes in the organization of visual pathways, including severe retrograde degeneration of retinal ganglion cells of the X/beta class. Cells in posteromedial lateral suprasylvian (PMLS) cortex display plasticity in that they develop normal receptive-field properties despite these changes, but they do not acquire the response properties of striate neurons that were damaged (e.g., high spatial-frequency tuning, low contrast threshold). One possibility is that the loss of X-pathway information, which is thought to underlie striate cortical properties in normal animals, precludes the acquisition of these responses by cells in remaining brain areas following neonatal VC damage. Previously, we have shown that monocular enucleation at the time of VC lesion prevents the X-/beta-cell loss in the remaining eye. The purpose of the present study was to determine whether this sparing of retinal X-cells leads to the development of striate-like response properties in PMLS cortex. We recorded the responses of PMLS neurons to visual stimuli to assess spatial-frequency tuning, spatial resolution, and contrast threshold. Results indicated that some PMLS cells in animals with a neonatal VC lesion and monocular enucleation displayed a preference for higher spatial frequencies, had higher spatial resolution, and had lower contrast thresholds than PMLS cells in cats with VC lesion alone. Taken together, these results suggest that preserving X-pathway input during this critical period leads to the addition of some X-like properties to PMLS visual responses.

Animals↗

PubMed1999

Frontal midline theta rhythms reflect alternative activation of prefrontal cortex and anterior cingulate cortex in humans.

Frontal midline theta rhythm (Fm theta) often appears on electroencephalogram (EEG) during consecutive mental tasks. To clarify the source of rhythmic activity, magnetoencephalogram (MEG) and EEG were simultaneously measured in six healthy volunteers during different mental tasks using whole head MEG system. MEG records were averaged every one cycle of Fm theta rhythms using individual positive peaks of Fm theta waves in Fz EEG as a trigger. Averaged theta components of MEG signals were analyzed with a multi-dipole model. Two sources were estimated to the regions both of the prefrontal-medial superficial cortex and anterior cingulate cortex (ACC). These regions were alternatively activated in about 40 to 120 degrees phase shift during one Fm theta cycle. From above results, we hypothesize that appearance of Fm theta during consecutive mental tasks reflects alternative activities of the medial prefrontal cortex and ACC.

Adult↗

PubMed1983

Neonatal hemidecortication or frontal cortex ablation produces similar behavioral sparing but opposite effects on morphogenesis of remaining cortex.

Rats with complete removal of the neocortex of one hemisphere (hemidecorticate) or of the cortex anterior to bregma in both hemispheres (frontal cortex) in adulthood were compared behaviorally and neuroanatomically with rats with similar removals at 7 days of age. Neonatal ablation of the frontal cortex produced partial sparing of performance on the Morris water task and reduced the thickness of the remaining neocortex. Neonatal hemidecortication produced similar sparing of function on the water task but increased the thickness of the contralateral neocortex. These results imply that behavioral sparing following neonatal cortical lesions is independent of the gross morphogenesis of the remaining neocortex.

Age Factors↗

PubMed1992

[Morphologic aspects of the maturation of the sensory areas of the cerebral cortex exemplified by the visual cortex of the rabbit].

When the cerebral cortex commences its earliest functional tasks, the cellular layers and the basic organisation pattern of cell processes have already developed. In the rabbit visual cortex it could be shown that the functional differentiation runs parallel to an increase in number and growth of cell processes. Those tissue compartments where the newly formed branches of the dendritic trees of cortical neurons come into contact with the axons arising from other cerebral regions, grow between two and six times larger depending on the cortical layer where their volume fractions are measured. Cell processes grow and increase in number most rapidly between the second and the fourth postnatal weeks. Myelination of fast conducting axons takes longer and attains an adult level about three month after birth. Then the visual cortex of the rabbit may be regarded as mature with regard to both structure and function.

Animals↗

PubMedDate not supplied

Cadmium in kidney cortex, liver, and pancreas from Swedish autopsies. Estimation of biological half time in kidney cortex, considering calorie intake and smoking habits.

Cadmium and zinc have been analyzed in tissues from 292 persons autopsied in Stockholm. In kidney cortex, liver, and pancreas the individual cadmium levels are distributed in a lognormal way. In kidney cortex there is a continuous accumulation of cadmium with age up to 50 years, followed by a decrease. Smokers show a higher cadmium accumulation. For nonsmokers, the biological half time of cadmium in kidney cortex is estimated at 30 years, with an average concentration at age 50 of 11 mug/g wet weight. When smokers are included, the average cadmium concentration at age 50 is 22 mug/g wet weight. Based on the more pronounced cadmium accumulation among smokers than nonsmokers, the respiratory absorption rate of cadmium from tobacco smoke is estimated to be approximately 50%.

Adolescent↗

PubMed2002

Involvement of reelin and Cajal-Retzius cells in the developmental formation of vertical columnar structures in the cerebral cortex: evidence from the study of mouse presubicular cortex.

The mammalian cerebral cortex is organized into horizontal and vertical arrays of neurons and their fiber connections that form anatomically and physiologically distinct laminar and columnar compartments. However, the developmental mechanism(s) underlying this dichotomous pattern remains a mystery. We provide anatomical evidence suggesting that reelin, a diffusible protein produced and secreted by Cajal-Retzius cells, is involved in the developmental formation of the vertical cell structures in the mouse presubicular cortex, the unique site where the vertical columnar arrays of cortical plate neurons and their dendritic branches are clearly identified during the early postnatal period. Our results also suggest that reelin plays a role in the formation of these vertical structures by acting as an inhibitory or stop signal for cortical plate neurons and their dendritic extensions. In addition to having perturbed horizontal laminae, reeler mutant mice, lacking reelin, display disruption of these vertical structures. Based on the present findings, we hypothesize that reelin and Cajal-Retzius cells regulate the developmental formation of not only horizontal laminations, but also vertical columnar structures in the cerebral cortex.

Animals↗

PubMed2004

Localization of the glutamine transporter SNAT1 in rat cerebral cortex and neighboring structures, with a note on its localization in human cortex.

SNAT1 mediates glutamine (Gln) influx into neurons and is believed to replenish the transmitters pools of glutamate (Glu) and gamma-aminobutyric acid (GABA). We investigated its distribution and cellular localization in the cerebral cortex and neighboring regions of rats and humans using light and electron microscopic immunocytochemical methods with specific antibodies. In the first somatic sensory cortex of rats and in areas 9, 10, 21 and 46 of the human cortex, numerous SNAT1-positive (+) cells were present in the cortical parenchyma and in the white matter; >95% of SNAT1+ cells were neurons, but some were astrocytes. Most SNAT1+ cells were pyramidal neurons, but numerous non-pyramidal neurons were also observed: SNAT1/GABA double-labeling studies showed that SNAT1 is expressed in all GABA+ neurons. SNAT1/synaptophysin studies showed that <0.1% of all synaptophysin+ puncta coexpressed SNAT1. SNAT1 immunoreactivity (ir) was also in leptomeninges, ependymal cells and choroid plexus. Electron microscopic studies showed that neuronal SNAT1 ir was almost exclusively observed in perikarya and dendritic profiles. SNAT1 ir was also in distal astrocytic processes, including end feet profiles, and in leptomeninges. These findings suggest that the major function of SNAT1 is not to replenish the transmitter pools of Glu and GABA.

Amino Acid Transport System X-AG↗

PubMed2005

Neuronal representations of stimuli in the mouth: the primate insular taste cortex, orbitofrontal cortex and amygdala.

The responses of 3687 neurons in the macaque primary taste cortex in the insula/frontal operculum, orbitofrontal cortex (OFC) and amygdala to oral sensory stimuli reveals principles of representation in these areas. Information about the taste, texture of what is in the mouth (viscosity, fat texture and grittiness, which reflect somatosensory inputs), temperature and capsaicin is represented in all three areas. In the primary taste cortex, taste and viscosity are more likely to activate different neurons, with more convergence onto single neurons particularly in the OFC and amygdala. The different responses of different OFC neurons to different combinations of these oral sensory stimuli potentially provides a basis for different behavioral responses. Consistently, the mean correlations between the representations of the different stimuli provided by the population of OFC neurons were lower (0.71) than for the insula (0.81) and amygdala (0.89). Further, the encoding was more sparse in the OFC (0.67) than in the insula (0.74) and amygdala (0.79). The insular neurons did not respond to olfactory and visual stimuli, with convergence occurring in the OFC and amygdala. Human psychophysics showed that the sensory spaces revealed by multidimensional scaling were similar to those provided by the neurons.

Adult↗

PubMed2003

The eloquence of silent cortex: analysis of afferent input to deafferented cortex in arm amputees.

Cortical reorganisation after limb amputation includes topographic displacements of body representation areas and changes of areal extent. Remarkably, truncated nerves, which had innervated amputated limb parts and remained in the residual limbs, can retain access to the deafferented somatosensory cortex. Using somatosensory evoked potentials (SEP) we characterized afferences from electrically stimulated truncated nerves to the brachial plexus and cortex in 12 arm amputees. While peripheral responses were highly variable, thalamocortical input to S-1, as reflected by the primary cortical SEP component, was present in 11 of 12 patients. Despite long-term deafferentation, macroscopic phenomena of inhibition/refractoriness, as assessed by stimulus rate variations, appeared to be changed only marginally. Thus, deafferented cortex remains responsive when given artificial phantom input and could provide a neuronal substrate for spontaneous phantom limb sensations, including phantom pain.

Adult↗

PubMed2004

The parietal cortex and attentional modulations of activities of the visual cortex.

We recorded high density event-related brain potentials (ERPs) from a patient with focal left parietal damage in a covert visual orienting task requiring detection of targets in the attended or unattended hemifield. A positivity peaking at 120 ms (P1) to the left visual field stimuli was enlarged when attended than unattended and was localized to the right extrastirate cortex. However, spatial attention did not influence the ERPs to the right visual field stimuli. The leftward cue elicited an enlarged P1 relative to the rightward cue. The results suggest that human parietal cortex is critical for the attentional modulation of the neural activities in the extrastriate cortex associated with stimuli in the contralateral hemifield.

Adolescent↗

PubMed1991

Acute effects of alcohol on unit activity in the motor cortex of freely moving rabbits: comparison with the limbic cortex.

Unit activity was recorded from the motor cortex of eight freely moving rabbits in order to examine the acute effect of ethanol (1 g kg-1) on organization of unit activity and to compare it with our earlier results from the limbic cortex. The rabbits performed a food-acquisition task in the experimental cage. Unit activity was recorded during behaviour in the control experiment followed by the alcohol experiment on the next day. After ethanol, behavioural mistakes and the duration of the behavioural cycle significantly increased. In the control experiments activation of 58% of the units had no constant relation to the phases of the behavioural cycle (non-involved units), whereas 42% of the units were constantly activated during certain phases (involved units). Two per cent of the latter units were activated in relation to newly learned behavioural acts (e.g. pedal pressing; L units), 28% in relation to food seizure and/or grinding (S units) and 12% in relation to certain movements during different behavioural acts (M units). Ethanol had no effect on the number of active units and the same relation between the number of non-involved and involved units or between the number of different types of involved units was found. However, the number of involved units decreased in the upper and increased in the lower cortical layers. Also the number of units with low background frequency increased, although the frequency within activations did not change. In our earlier study the number of active units in the limbic cortex decreased after ethanol by one third and the relation between the number of L and M units was reversed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

Chronic suppression of activity in barrel field cortex downregulates sensory responses in contralateral barrel field cortex.

Numerous lines of evidence indicate that neural information is exchanged between the cerebral hemispheres via the corpus callosum. Unilateral ablation lesions of barrel field cortex (BFC) in adult rats induce strong suppression of background and evoked activity in the contralateral barrel cortex and significantly delay the onset of experience-dependent plasticity. The present experiments were designed to clarify the basis for these interhemispheric effects. One possibility is that degenerative events, triggered by the lesion, degrade contralateral cortical function. Another hypothesis, alone or in combination with degeneration, is that the absence of interhemispheric activity after the lesion suppresses contralateral responsiveness. The latter hypothesis was tested by placing an Alzet minipump subcutaneously and connecting it via a delivery tube to a cannula implanted over BFC. The minipump released muscimol, a GABA(A) receptor agonist at a rate of 1 mul/h, onto one barrel field cortex for 7 days. Then with the pump still in place, single cells were recorded in the contralateral BFC under urethan anesthesia. The data show a approximately 50% reduction in principal whisker responses (D2) compared with controls, with similar reductions in responses to the D1 and D3 surround whiskers. Despite these reductions, spontaneous firing is unaffected. Fast spiking units are more sensitive to muscimol application than regular spiking units in both the response magnitude and the center/surround ratio. Effects of muscimol are also layer specific. Layer II/III and layer IV neurons decrease their responses significantly, unlike layer V neurons that fail to show significant deficits. The results indicate that reduced activity in one hemisphere alters cortical excitability in the other hemisphere in a complex manner. Surprisingly, a prominent response decrement occurs in the short-latency (3-10 ms) component of principal whisker responses, suggesting that suppression may spread to neurons dominated by thalamocortical inputs after interhemispheric connections are inactivated. Bilateral neurological impairments have been described after unilateral stroke lesions in the clinical literature.

Action Potentials↗