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PubMed2002

Unmasking motion-processing activity in human brain area V5/MT+ mediated by pathways that bypass primary visual cortex.

Most models of the human visual system argue that higher-order motion-processing cortical regions receive their inputs only via the primary visual cortex (striate cortex), rather than also via direct projections from the thalamus that bypass primary visual cortex. However, recent evidence in non-human primates, along with some evidence in humans with damaged primary visual cortex (e.g., "blindsight" for motion in the blind visual hemifield), have argued for the existence of a direct thalamic-to-extrastriate projection for motion processing. This evidence remains controversial. Here we tested the idea that direct thalamic input to extrastriate motion processing areas exists in humans but might be masked in scalp recordings by activity from early visual areas. To do this, we employed stimuli that induced strong refractory effects in primary visual cortex--thereby creating a brief "reversable lesion" in primary visual cortex--immediately before the presentation of a motion stimulus. Under these conditions, we then assessed whether motion areas of cortex were still able to process the motion stimuli by recording event-related potentials (ERPs) and event-related magnetic fields (ERFs/MEG). We found robust motion-related activity in extrastriate motion processing areas in the ERP and MEG signals even when primary visual cortex was heavily suppressed by our manipulation. This finding provides evidence for a direct thalamic functional pathway to extrastriate visual cortical motion processing areas in the human that bypasses primary visual cortex.

Adult↗

PubMed2002

[Electron microscopic analysis of expression of NMDA-R1 in the developmental process of visual cortex in strabismic amblyopic cat].

OBJECTIVE: To investigate the expression and distribution of N-methyl-D-aspartate receptor subunit 1 (NMDA-R1) in neuronal ultrastructure in visual cortex of strabismic amblyopic cat during development. METHODS: Eleven kittens were used for this study. Esotropia in six kittens had been made monocularly by tenotomy at two weeks of age. Two pairs of normal and strabismic kittens were sacrificed in three weeks of age, one week after tenotomy. Another two pairs of normal and strabismic kittens were sacrificed in five weeks of age, three weeks after tenotomy. One normal and two strabismic amblyopic cats were sacrificed after 6 months of age. Animals were deeply anaesthetized and perfused transcardially with 4% paraformaldehyde. Cryostat sections of frontal central area P5-P0 were cut to 25 micro m thickness. The mouse anti-NMDA-R1 monoclonal antibody (mAb54.1, PharMingen) was used. After stained, a light microscope was used to select regions of layer II-III, layer IV and layer V-VI of visual cortex area 17 for re-embedding. HITACHI H-7000 transmission electron microscope at magnifications ranging from 30 000 - 300 000 X was used for observation. RESULTS: Three hundred and twenty-eight neurons of strait cortex were observed. NMDA-R1 receptor was located at the nuclei, Nissl body, cytoplasm, plasma membrane and the postsynaptic element of axons and dendrites. The ultrastructural morphology, including the mitochondrion, smooth endoplasmic reticulum, rough endoplasmic reticulum, and the Golgi apparatus, was not significantly different in the comparison between the cells in visual cortex of normal and strabismic groups. In the entire normal group, the percentage density of NMDA-R1 labeled cells was higher than that of strabismic groups (chi(2) = 4.280, 4.41, 4.89; P < 0.05). One thousand and three hundred and twenty NMDA-R1 immunopositive synapses were counted. The NMDA-R1 immunopositive synapses were dominated in layer II-III of visual cortex and increased during the development of normal kittens (F = 3.28, P < 0.05). There was no significant difference of NMDA-R1 immunopositive synapse distribution between the normal and strabismic kitten at 3 weeks (one week after operation) of age (F = 0.17, P > 0.05). The reduction of NMDA-R1 immunopositive synapse of plasma membrane in visual cortex of strabismic kitten was started at 5 weeks (threes weeks after surgery) of age. It was decreased significantly in strabismic amblyopic cat compared with that of the normal cat (F = 26.94, 47.01; P < 0.001). The ratios of nuclear membrane invagination of cells in visual cortex of normal and strabismic cat were higher than those of normal and squint kittens (chi(2) = 36.24, P < 0.01), but the ratio was not significantly different between the normal and strabismic group. CONCLUSION: (1) In the normal developmental process of cat, the plasticity of the neuronal synapsis in II and III layer of visual cortex is relatively great. (2) In the strabismus amblyopia occurring in the plastic critical period of visual development, no pathological changes of neuronal organelle in the visual cortex are found, but there are changes at molecular level in the neuronal synapsis.

Amblyopia↗

PubMed1991

[The functional relationship between the cerebral cortex and deep brain areas in normal individuals].

Recent PET or SPECT studies have demonstrated a reduction of blood flow and metabolism in the cortex ipsilateral to a deep-seated lesion, and in the thalamus and/or basal ganglia ipsilateral to a cortical lesion. A close relationship between the cerebral cortex and deep areas of the brain has been shown in pathological conditions, presumably because of functional interconnections between the cortex and deeper area. The present study was designed to investigate the relationship of cerebral blood flow in the cerebral cortex to that in the deep gray matter including the basal ganglia and the thalamus in normal subjects. Twenty-two healthy subjects were studied using SPECT with N-isopropyl-p[123I]iodoamphetamine while in a resting state. The asymmetry index (AI) of blood flow in both the cerebral cortex and deep gray matter was calculated as follows; AI = (R-L)/(R+L)/200 (%) (R: right side, L: left side). The AI in deep gray matter was significantly correlated with the AI values in the upper frontal cortex (r = 0.54, p less than 0.01), and parietal cortex (r = 0.58, p less than 0.01), as well as the mean cortical hemispheric AI (r = 0.48, p less than 0.05). Our results suggest the existence of a functional relationship between the cerebral cortex and deep areas not only in pathological conditions but also in the resting state in normal subjects. This functional relationship is likely to be mediated by neuronal mechanisms through the projectional fiber connections between the cortex and the deep gray matter.

Adult↗

PubMed1989

The visual cortex of the agouti (Dasyprocta aguti): architectonic subdivisions.

1. We have studied the cytoarchitecture and myeloarchitecture of the agouti's cortical surface that can be activated by visual stimulation. Five architectonic subdivisions that correspond to distinctive visuotopic representations were characterized. 2. The largest portion of the visual cortex is occupied by area 17 which is situated lateral to the cingulate cortex, medial to area 18, posterior to the parietal cortex, and anterior to the agranular retrosplenial cortex. Additionally, four architectonic subdivisions in the extrastriate visual cortex were distinguished, i.e., from medial to lateral: area 18, area 19, anterior lateral area, and temporal posterior area. 3. Along the border of the extrastriate cortex a ring of nonvisual cortical fields was encountered encompassing parietal (somatic sensorial) cortex, temporal anterior and temporal intermediate (auditory) areas, a band of pre-rhinal cortex, and agranular retrosplenial cortex.

Animals↗

PubMedDate not supplied

[Lateralization of opioid receptors and their putative ligands in the visual cortex of the turtle].

Opioid mu-agonist morphine, delta-agonist D-Ala2,D-Leu5-enkephalin (DADL) and kappa-agonist bremazocine locally applied to the surface of turtle visual cortex inhibited the orthodromic evoked potential (EP; fast negative component N1). The lack of cross-desensitization to the inhibitory action of opioids upon EP indicates that the drugs exert their effects via different opioid receptors. Morphine and bremazocine predominantly inhibited the left cortex EP, whereas DADL was a potent inhibitor of the right cortex EP. Thus opioid receptors which modulate evoked electrical activity of the left visual cortex (LVC) apparently belong mostly to mu- and kappa-type while delta-receptors were predominantly responsible for the modulation of electrical activity in the right visual cortex (RVC). Application of LVC- and RVC-extracts to the cortex surface led to EP inhibition, which was partially (60-80%) prevented by antagonist naloxone. LVC-extract proved to be a more potent inhibitor of the left cortex EP, whereas RVC-extract was found to be more effective when applied to the right cortex. It is suggested that not only opioid receptors, but also their endogenous ligands are lateralized in turtle visual cortex.

Animals↗

PubMedDate not supplied

[The functional organization of the spatial structures of the neuronal receptive fields in field 21 of the cat cerebral cortex].

In result study of structural organization of neural receptive fields (RFs) and their different zones on the prestriate cortex level was shown that neural RFs in this area have hypercomplex structure and consist of some spatial different excitatory zones. Orientation and velocity selectivity and spatial-frequency characteristics of the excitatory zones of the same RF may differ between zones. The number of zones in RFs correlate with RF sizes: the more RF size the more zones number in them (r = 0.05, P < 0.02). About 66% of zones in RFs have approximately identical sizes (12-16 deg) and sizes those zones an dependence as from their number in RFs (r = 0.03, P > 0.05) as from the eccentricity (r = 0.3, P > 0.05). Zones in RF were distributed so that distance their centres was between 56-65 degrees (an average across all 60 degrees). If two or three zones were tested simultaneously the neuron changed own frequency and orientation tuning. Consequently the functional organization of neural RFs of prestriate cortex depend upon number simultaneously tested zones in spatial information processing. Was shown that important properties of prestriate cortex neurons is their ability to integrate and complex processing of spatial information across wide area of the visual field; in the prestriate cortex thus violate of straight retinotopical representation principle of visual field, characteristics of all investigated areas of visual system. The results represented in this review allow suppose that the structural and functional unit of cortex which make integration of spatial information from different compose this information is prestriate cortex neurons and not is no striate cortex modules. Consequently combined of neurons which make images description from different parts of visual field out of dependence of cortical area in turn integrate in neuron networks. Is known that neurons of any level have characteristics different of (from) characteristics of other levels visual system. The interaction of different elements of visual system form ultrastructure of RFs and their different zones in prestriate cortex, and ensure function of networks. So just on prestriate cortex neurons level appear whole system of surrounding world universe system of connections from different cortical areas which is morphological and functional base in process of spatial information integration RFs which have the central and peripheral representation.

Animals↗

PubMed1995

The projection from the primary motor and somatic sensory cortex to the basilar pontine nuclei. A detailed electrophysiological and anatomical study in the rat.

The projections from the primary motor and somatic sensory cortex onto the basilar pontine grey were studied in Wistar Rats injecting microvolumes of WGA-HRP solution in sites of the motor and sensory cortex electrophysiologically identified. The main results may be summarized as follows. (a) The projections from both the motor and sensory cortex were found as rostrocaudally oriented columns of terminals in the basilar pontine nuclei. The projection from the motor cortex extended to all over the rostrocaudal extension of the basilar pontine nuclei. To a rostrocaudal shift of the pontine projection field correspond a rostrocaudal displacement in the motor area. The projection from the sensory cortex was mainly restricted to the caudal two thirds of the basilar pontine nuclei, though the hindlimb region of the sensory cortex also showed a discrete representation in the rostral third of the basilar pontine nuclei. (b) The terminal fields of the motor and sensory cortex were segregated except those in the caudal pontine level, which come from the projection of the hindlimb cortical regions. (c) Within the terminal fields of the projections from the motor as well as from the sensory cortex a clearcut topographical arrangement was observed between the projections of cortical areas controlling the head, the forelimb and the hindlimb regions. (d) Within the location of these major subdivisions, the representations of individual body segments were overlapped for a little part ("convergent zones"), whereas the greater part of their projection zones was selective of each cortical field ("private zones"). In conclusion, the present study showed that the projections from the motor and sensory cortex to the basilar pontine nuclei are arranged with a very precise somatotopical organization.

Animals↗

PubMed1983

Opiate receptor localization in rat cerebral cortex.

The differential distributions of [3H]naloxone-labeled and [3H]D-Ala-D-Leu-enkephalin-labeled opiate receptors in rat cerebral cortex were localized autoradiographically and quantified by grain counting and computerized densitometry. In addition, receptor distributions were compared to terminal patterns of thalamocortical projections labeled by axoplasmic transport of [3H]amino acids. Opiate receptors labeled with [3H]naloxone in a mu ligand selectivity pattern show striking laminar heterogeneity and are densest in limbic cortical areas, intermediate in the motor cortex, and fewest in the primary sensory areas. By contrast, opiate receptors labeled with [3H]D-Ala2-D-Leu5-enkephalin in a delta ligand selectivity pattern are much more homogeneously distributed across both regions and laminae within regions. Mu receptors in most cortical areas have density peaks in layers I and VI and each peak shows a density gradient that is sloped within the layer so that the highest densities are at the most superficial and the deepest portions of cortex. In addition, there is an intermediate peak whose laminar position varies depending on the area in which it is found. In rostral agranular cortex, including limbic and motor areas, the [3H]naloxone binding peaks are in layers I, III, and VI. In primary somatosensory cortex, the intermediate peak is in layer Va and in most of remaining homotypical cortex it is in layer IV. Some areas have only bilaminar labeling, in superficial and deep layers; these include portions of the sulcal and retrosplenial cortices. Piriform and entorhinal cortices have dense [3H]naloxone binding only in the deepest layer and show a descending gradient of density toward the superficial layer. The positions of the mu receptor peaks were compared with termination patterns of projections originating in the thalamus. Close correspondence was found between receptor binding in the prelimbic, primary somatosensory, and entorhinal areas and projection terminations arising from the thalamic mediodorsal, posterior, and central medial nuclei, respectively. Although regional variations in [3H]D-Ala2-D-Leu5-enkephalin-labeled receptor density are uncommon, a gradual decrease in the number of sites along the dorsomedial wall of the cortex from anterior cingulate to caudal retrosplenial limbic cortex can be observed. Laminar variations in binding density are small as well; higher concentrations of the peptide binding sites are usually found in the deep cortical layers. These findings emphasize aspects of opiate receptor architecture which may be relevant to identifying cortical "opiatergic" neurocircuitry and raise the possibility of opiate modulation of thalamocortical transmission.

Animals↗

PubMed1977

Columnar distribution of cortico-cortical fibers in the frontal association, limbic, and motor cortex of the developing rhesus monkey.

The terminal distribution of cortico-cortical connections was examined by autoradiography 7-8 days following injections of tritium labeled amino acids into the dorsal bank of the principal sulcus, the posterior part of the medial orbital gyrus, or the hand and arm area of the primary motor cortex in monkeys ranging in age from 4 days to 5.5 months. Labeled axons originating in these various regions of the frontal lobe have topographically diverse ipsilateral and contralateral destinations but virtually all of these projections share a common mode of distribution: they terminate in distinct vertically oriented columns, 200-500 mum wide, that extend across all layers of cortex and alternate in regular sequence with columns of comparable width in which grains do not exceed background. Spatial periodicity in the pattern of transported label in such regions as the prefrontal association cortex, the retrosplenial limbic cortex and the motor cortex indicates that columination in the intracortical distribution of afferent fibers is not unique to sensory specific cortex but is instead a general feature of neocortical organization. A columnar mode of distribution of cortico-cortical projections is present in monkeys at all ages investigated but is especially well delineated in the youngest of them. Thus, grain concentrations within columns are very high in monkeys injected at 4 days of age, somewhat lower in monkeys injected at 39-45 days of age, and least dense in those injected at 5.5 months. The distinctness of the spatially segregated pattern of innervation in the cortex of neonates indicates that the columnar organization of association-fiber systems in the frontal and limbic cortex is achieved before or shortly after birth.

Animals↗

PubMed1987

Consequences of damage to the sensorimotor cortex in neonatal and adult cats. II. Maintenance of exuberant projections.

After chronic sensorimotor cortex ablations, sparing and greater recovery of function were seen in neonatally operated cats compared with adult operated cats. These results suggested that undamaged cortex in neonatal operates might display projections different from those of adult operates. Injections of horseradish peroxidase-wheat germ agglutinin (HRP-WGA) were made in ipsilateral parietal cortex adjacent to the sensorimotor cortex ablations or in the contralateral sensorimotor cortex. No changes in the projections of the parietal cortex were seen in operated cats or in the projections of the undamaged sensorimotor cortical projections of adult operates. In contrast, the intact sensorimotor cortex of neonatal operates exhibited crossed corticothalamic and corticorubral projections not present in normal or adult operated animals, whereas the corticospinal tract (CST) was unchanged by the ablations. Analysis of neurons within the ventroanterior-ventrolateral nuclear complex of the thalamus ipsilateral to the ablation showed that the surviving cells of neonatal operates were equal in number but were, on average, larger than those of normals and adult operates. Some neurons in neonatal operates were larger than any seen in adult operates and normals. Injections of HRP/WGA were also made into the sensorimotor cortex of normal newborn animals. Dense bilateral corticothalamic and corticorubral projections were present. The CST had extended to lumbar levels by the day of birth but projections to the grey matter were sparse. Thus, bilateral projections seen in neonatal operates probably represent retention of some exuberant projections present in normal neonatal animals. The CST which exhibited no exuberant projection was unchanged by the lesion. The crossed corticothalamic and corticorubral projections are likely to play a role in sparing and recovery of function particularly in sparing of contact placing.

Animals↗

PubMed2005

Cortical efferents of the entorhinal cortex and the adjacent parahippocampal region in the monkey (Macaca fascicularis).

Entorhinal cortex (EC) relays information from the hippocampus to the cerebral cortex. The origin of this entorhino-cortical pathway was studied semiquantitatively and topographically with the use of 23 retrograde tracer injections in cortical areas of the frontal, temporal, and parietal lobes of the monkey. To assess possible alternative, parallel pathways, the parahippocampal region, comprised of temporal pole (TP), perirhinal (PRC), and posterior parahippocampal cortices (PPH), was included in the study. The majority of the cortical areas receive convergent projections from EC and the parahippocampal region. Strong EC layer V output is directed to temporal pole, medial frontal and orbitofrontal cortices, and the rostral part of the polysensory area of the superior temporal sulcus (sts). Moderate EC output is directed to the caudal superior temporal gyrus, area TE, and parietal cortex, and little to none to the lateral frontal cortex. With the exception of the projection to the medial frontal cortex, output from TP, PRC, and PPH surpassed that from EC, although with regional differences. TP layers II-III, V-VI project strongly to all areas injected except parietal cortex and caudal superior temporal gyrus, while PRC layers III/V-VI send strong projections to rostral parts of area TE and sts. PPH layers III/V-VI project heavily to parietal cortex and caudal superior temporal gyrus. These results suggest that the medial temporal output is primarily organized hierarchically, but at the same time, it has multiple exits of information. These parallel, alternative routes may influence local circuitry in the cerebral cortex and participate in the consolidation of declarative memory.

Animals↗

PubMed2004

Electromagnetic function of polymicrogyric cortex in congenital bilateral perisylvian syndrome.

BACKGROUND: Congenital bilateral perisylvian syndrome (CBPS) is characterised by bilateral perisylvian polymicrogyria and suprabulbar paresis. Mild tetraparesis, cognitive impairment, and epilepsy are frequently associated. Sensory deficits are surprisingly rare, even though polymicrogyria often extends to auditory and sensorimotor cortex. OBJECTIVES: To study the sensorimotor and auditory cortex function and location in CBPS patients. METHODS: We mapped the sensory and motor cortex function onto brain magnetic resonance images in six CBPS patients and seven control subjects using sources of somatosensory and auditory evoked magnetic fields, and of rhythmic magnetoencephalographic (MEG) activity phase-locked to surface electromyogram (EMG) during voluntary hand muscle contraction. RESULTS: MEG-EMG coherence in CBPS patients varied from normal (if normal central sulcus anatomy) to absent, and could occur at abnormally low frequency. Coherent MEG activity was generated at the central sulcus or in the polymicrogyric frontoparietal cortex. Somatosensory and auditory evoked responses were preserved and also originated within the polymicrogyric cortex, but the locations of some source components could be grossly shifted. CONCLUSION: Plastic changes of sensory and motor cortex location suggest disturbed cortex organisation in CBPS patients. Because the polymicrogyric cortex of CBPS patients may embed normal functions in unexpected locations, functional mapping should be considered before brain surgery.

Adolescent↗

PubMedDate not supplied

[Dynamics of changes in the level of GABA in various sections of the cerebral cortex and cerebellum of dogs during postnatal ontogenesis].

The content of gamma-aminobutyric acid (GABA) in different sections of dog cerebral cortex and cerebellum suffers considerable changes in the postnatal ontogenesis. In the optic area (field 17) of the cerebral cortex GABA content significantly increases from the birthday till six-month age and then it decreases and remains in puberal animals (the 365th day) at the level of three-month ones. In the parietal and motor sections of the cortex and cerebellum the content of GABA increases intensively during the first fortnight of the postnatal development, decreases sharply during the third week of the development, remains at the reached level till the 90th day and then it increases till the six-month age, reaching maximum levels which are 1.6, 1.8 and 2.3 times as high as the GABA content in these areas, respectively. In puberal (the 365th day) animals GABA content in these sections of the cortex and cerebellum considerably decreases in comparison with 6-month animals. In the parietal and motor sections of the cortex it reaches approximately the level of that in newborn ones and in the optic area of the cortex and cerebellum it is 1.7 and 1.8 respectively, as high as this level. In all the studied sections of the brain cortex and in the cerebellum the content of GABA changes most intensively (2.7 muM per 100 g of fresh tissue a day) during the first three weeks of postnatal development. Some of the investigated sections of the brain cortex and cerebellum differ in GABA content mainly at the early stages of the postnatal ontogenesis (till the 21st day after birth).

Age Factors↗

PubMed1981

[Associative connections of the parietal cortex in cats].

Cortico-cortical connections of sensory (visual, auditory and somatosensory) areas of cortex with parietal associative cortex were investigated in cat by means of retrograde axonal transport of horse-radish peroxidase and Fink-Haimer technique. The shape, size and localization of cells which make monosynaptic connections between the primary sensory areas and parietal cortex and the distribution of fiber terminals of such cells in the associative parietal cortex were determined. Maximum number of cells connected with field 7 of the parietal associative cortex was found in field V1 of the visual cortex, and with field 5 in field S1 of the somatosensory cortex. Besides HRP-positive pyramidal neurons, mainly localized in layers II-IV, labelled stellate and spindle-shaped cells were found in a small amount. The connections of parietal associative cortex are discussed on the basis of the data obtained.

Animals↗

PubMed1997

T2 shortening in the visual cortex: effect of aging and cerebrovascular disease.

PURPOSE: To evaluate the effect of aging and cerebrovascular disease on T2 shortening in the visual cortex at MR imaging. METHODS: MR images of 72 neurologically normal subjects (45 men and 27 women, 35 to 92 years old) and 32 (13 men and 19 women, 54 to 92 years old) with cerebrovascular disease were evaluated retrospectively. On T2-weighted spin-echo images, the signal intensity of the visual, motor, and sensory cortices was divided into three grades and compared with the signal intensity of the frontal subcortical white matter. RESULTS: Decreased signal intensity (grade III) was rarely seen in the visual and sensory cortices of the neurologically normal subjects who were less than 60 years old. The signal intensity of the motor cortex decreased rapidly after the age of 50 years. At 61 to 70 years of age, 53% of these subjects had grade III intensity, and at age 71 years or older, 94% had reached grade III. The frequency of progression from grade I to grade III was lower in the visual cortex than in the motor cortex; 22% of these subjects had grade III appearance at age 61 to 70 years, and at age 71 years older, 56% had reached grade III. In patients with cerebrovascular disease who were older than 60 years of age, the frequency of grade III signal intensity in the visual cortex was almost equal to that in the neurologically normal subjects. CONCLUSIONS: T2 shortening in the visual cortex is frequently seen in neurologically normal older persons. These findings are compatible with a previously reported histochemical study of normal iron deposition in the visual cortex. Cerebrovascular disease has no effect on T2 shortening in the visual cortex.

Adult↗

PubMed1994

Direct projections from the non-laminated divisions of the medial geniculate nucleus to the temporal polar cortex and amygdala in the cat.

The medial geniculate nucleus (MG) is well known to send projection fibers not only to the auditory cortex, but also to the limbic structures of the forebrain including the perirhinal cortex and amygdala. In the cat, the non-laminated portions of the MG are also known to project to the amygdala, as well as to the auditory cortical areas surrounding the primary auditory area. On the other hand, projections from the non-laminated MG to the limbic cortical areas have not so far been studied systematically. Thus, in the present study, direct projections from the non-laminated portions of the medial geniculate nucleus to the temporal polar cortex and amygdala were examined in the cat by retrograde and anterograde tract-tracing techniques. The temporal polar cortex is the ventral polar region of the posterior sylvian and posterior ectosylvian gyri, which is located dorsal to the posterior rhinal sulcus and includes the ectorhinal area. After injection of cholera toxin B subunit into the temporal polar cortex, retrogradely labeled neurons were seen in the caudal two-thirds of the medial geniculate nucleus ipsilateral to the injection; they were distributed in the non-laminated portions of the MG (the dorsal and medial divisions and the ventromedial part of the ventral division), but not in the laminated portion (the principal part of the ventral division). These findings were confirmed by injecting Phaseolus vulgaris leucoagglutinin into each division of the MG. After the injection into each non-laminated division, terminal labeling was observed in the temporal polar cortex. Terminal labeling was further found in the lateral amygdaloid nucleus ipsilateral to the injection. Then, cholera toxin B subunit was injected into the lateral amygdaloid nucleus; retrogradely labeled neurons were observed ipsilaterally in the non-laminated portions of the MG, as well as in the temporal polar cortex. The results indicate that the non-laminated portions of the MG send projection fibers to the temporal polar cortex and lateral amygdaloid nucleus, and that the non-laminated portions of the MG and temporal polar cortex give rise to overlapping projections to the lateral amygdaloid nucleus. These connections appear to constitute neuronal links in "emotional" and/or "motivational" circuitry in the forebrain.

Amygdala↗

PubMed1995

Human orbitofrontal cortex: cytoarchitecture and quantitative immunohistochemical parcellation.

The primate orbitofrontal cortex is a component of the paralimbic cortical "belt" and consists of several distinct areas. It is involved in high order association functions that include the integration of emotion, behavior, and various sensory processes. To define the cyto- and chemo-architectonic organization of the human orbitofrontal cortex, we have used antibodies to the nonphosphorylated neurofilament triplet protein and to the calcium-binding proteins parvalbumin and calretinin. Immunohistochemistry revealed labeling patterns corresponding to the cytoarchitecture defined by Nissl preparations. Neurofilament protein-immunoreactive pyramidal neurons were located only in layers V-VI in the agranular posterior orbitofrontal cortex, whereas they were distributed in both layers III and V-VI in the anteromedial and anterolateral granular regions. The intermediate dysgranular portion of the orbitofrontal cortex represented a transition zone with a progressive decrease in layer III labeled pyramidal cell numbers posteriorly. The distribution of parvalbumin- and calretinin-immunoreactive interneurons was more homogeneous, although the posteromedial region and the cortex of the inferior rostral sulcus had slightly lower parvalbumin-positive neuron counts than the other orbitofrontal areas. Parvalbumin immunoreactivity in the neuropil exhibited a high degree of regional specialization in that it was consistently less intense in the cortex of the intermediate and posterior part of the gyrus rectus, whereas the other orbitofrontal areas had a very dense neuropil staining in layers III to V. Also, there was a dense plexus of parvalbumin-immunoreactive fibers restricted to layer I in the posterolateral orbitofrontal cortex, and patches of neuropil staining in layer III of the inferior rostral sulcus. These region-specific neuropil staining patterns may correspond to the distribution of parvalbumin-immunoreactive thalamocortical projections to distinct domains of the orbitofrontal cortex. This regional parcellation of the human orbitofrontal cortex as defined by specific neuronal markers, may represent an anatomical substrate for the localization of the various functions attributed to this poorly understood cortical region.

Aged↗

PubMed1993

Neurochemical development of the hippocampal region in the fetal rhesus monkey. I. Early appearance of peptides, calcium-binding proteins, DARPP-32, and monoamine innervation in the entorhinal cortex during the first half of gestation (E47 to E90).

Although the entorhinal cortex is a key structure connecting the hippocampal formation with the rest of the cerebral cortex, little is known about its early chemoanatomical development in primates. In the present study, a cytoarchitectonic analysis and immunocytochemical detection of somatostatin, neurotensin, parvalbumin, calbindin-D 28K, DARPP-32, as well as tyrosine hydroxylase, dopamine-beta-hydroxylase, and serotonin, were carried out on serial sections of the entorhinal cortex of six rhesus monkey fetuses aged E47 to E90 (gestation period 165 days). At E56 the cortical plate of the entorhinal cortex already exhibited a sublamination; at E64 the lamina dissecans was partly formed, allowing the emergence of the lamina principalis externa and interna, and at E83 most of the regional and laminar subdivisions characteristic of the adult cortex could be identified, except for the rhinal sulcus restricted to a small dimple. The neurochemical development paralleled the early cytoarchitectonic differentiation, both largely preceding that of the neighboring cortical areas. The somatostatin-like immunoreactive innervation, first detected at E56, was very dense as early as E64 and displayed by E83 a laminar distribution similar to that found in the adult. Labeled neurons indicated an intrinsic origin for this innervation but an extrinsic connection might be present as labeled fibers in the subplate of the entorhinal cortex were in continuity with positive fibers in the intermediate zone of the hippocampal formation. A faint neurotensin-like immunoreactivity first detected at E64 became prominent at E83 in the entorhinal cortex but stopped abruptly at the anlage of the rhinal sulcus. The lack of neurotensin-labeled neurons contrasted with their presence in other parts of the hippocampal region and suggested a precocious extrinsic connection. Only rare parvalbumin-LIR neurons were detected at midgestation, whereas calbindin-D 28K was expressed from E47 on in Cajal-Retzius cells and from E56 on in various types of neurons in the cortical plate and subplate. Most characteristic was a category of medium-sized, deeply stained calbindin-LIR neurons, present only in the lamina principalis externa and possibly corresponding to the population of large neurons described by Kostovic et al. (1990, Soc Neurosci Abstr 16:846) in early developing entorhinal cortex of human fetuses. These and probably other neurons were also DARPP-32-positive, suggesting the possibility of an early dopaminergic regulation. Indeed, the monoaminergic innervation of the entorhinal cortex was detected from E56 on and gradually increased in density, displaying areal and laminar differences in the distribution of the dopaminergic, noradrenergic, and serotoninergic afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗