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PubMed1988

Projections from the medial cortex in the brain of lizards: correlation of anterograde and retrograde transport of horseradish peroxidase with Timm staining.

Efferent projections of the medial cortex of the lizards Podarcis hispanica and Gallotia stehlinii were studied by examining the transport of horseradish peroxidase; results were correlated with those from Timm-stained sections. Two efferent systems were found. The first reaches the distal part of the outer plexiform layer in the medial, dorsomedial, and dorsal cortices, i.e., zones that are negative to Timm staining, and possibly originates from horizontal fusiform neurons. The second reaches the Timm-positive zones in the cortex and septum and is topographically arranged: the vertical portion of the intermediate and caudal medial cortex and the entire rostral medial cortex project to the inner two-thirds of the outer plexiform layer of the dorsomedial cortex and of the medial subfield of the dorsal cortex; to the paraventricular zone of the inner plexiform layer of the medial cortex; and bilaterally to the dorsal part of the dorsal precommissural septum. The dorsal part of the intermediate and caudal medial cortex and the ventralmost folded part of its caudal edge project rostrally to the juxtasomatic zone of the outer plexiform layer and the entire inner plexiform layer of the intermediate and lateral subfields of the dorsal cortex and to the ventral part of the dorsal septum. In its intense Timm reaction and its ultrastructural properties, as reported in earlier studies, the Timm-positive fiber system of the lizard brain shows a close resemblance to the mossy fiber system of the mammalian hippocampus.

Animals↗
PubMed1989

Efferent connections of the dorsal cortex of the lizard Gekko gecko studied with Phaseolus vulgaris-leucoagglutinin.

The efferent connections from the dorsal cortex of the lizard Gekko gecko have been studied with the anterograde tracer Phaseolus vulgaris-leucoagglutinin. It appeared that the dorsal cortex is not a homogeneous structure as far as the efferent connections are concerned. All parts of the dorsal cortex project to the septum. All parts except the most medial project to the dorsal ventricular ridge, amygdala, nucleus periventricularis hypothalami, area lateralis hypothalami, and the anterior olfactory nucleus. The most medial part, in addition to the septal projections, is connected with the medial cortex and the contralateral medial and dorsal cortices. From the rostral part additional projections could be traced to the nucleus dorsolateralis hypothalami, nucleus ventromedialis thalami, nucleus dorsolateralis thalami, striatum, pallial thickening, medial cortex, nucleus olfactorius anterior, and the main and accessory olfactory bulbs. From the caudal part additional projections exist to the nucleus dorsomedialis thalami, nucleus accumbens, and the contralateral dorsal cortex. A system of intrinsic connections exists that can be subdivided into four subsystems, each of which subserves the interconnections within four subdivisions of the cortex: 1) the superficial medial part, 2) the deep medial part, 3) the caudal lateral and caudal intermediate parts, and 4) the rostral lateral and rostral intermediate parts. Connections between these four areas are scarce. From the present results the conclusion is drawn that the dorsal cortex of the lizard Gekko gecko has many hodological aspects in common with the ventral subiculum of mammals. The present results do not support the hypothesis that the dorsal cortex is the reptilian equivalent of the mammalian neocortex.

Amygdala↗
PubMed1989

Calcitonin gene-related peptide immunoreactivity in the visceral sensory cortex, thalamus, and related pathways in the rat.

It has been proposed that calcitonin gene-related peptide (CGRP) may serve as a major neuromodulator in visceral sensory pathways, but its exact role in the visceral sensory thalamus and cortex has not been determined. We therefore examined the distribution of CGRP-like immunoreactive (CGRPir) innervation of the insular cortex and the parvicellular division of the ventroposterior nucleus of the thalamus (VPpc) in the rat by using immunohistochemistry for CGRP combined with retrograde transport of the fluorescent dye fluoro-gold. Modest numbers of CGRPir fibers were distributed in the dysgranular and agranular insular cortex, but few were observed in the granular insular cortex. The density of CGRPir innervation increased caudally along the rhinal fissue and was considerably greater in the perirhinal cortex. When fluoro-gold was injected into the insular cortex numerous retrogradely labeled neurons were seen in the VPpc, but few of these were CGRPir. Retrogradely labeled CGRPir neurons were, however, seen in the ventral lateral and medial parabrachial (PB) subnuclei. Injection of fluoro-gold into the perirhinal cortex (which is just caudal to the insular cortex along the rhinal fissure) resulted in many retrogradely labeled CGRPir neurons in the posterior thalamic region, including the subparafascicular, the lateral subparafascicular, and the posterior intralaminar nuclei. The VPpc was heavily innervated by CGRPir fibers but contained few CGRPir cell bodies. Injection of fluoro-gold into the VPpc resulted in many retrogradely labeled CGRPir neurons in the external medial PB subnucleus bilaterally, but with a contralateral predominance. Smaller numbers of retrogradely labeled CGRPir neurons were also observed in the ventrolateral PB subnucleus, bilaterally with an ipsilateral predominance. These results suggest that CGRP may be a neuromodulator in the ascending visceral sensory pathways from the PB to the VPpc and the insular cortex, but not between the latter two structures.

Animals↗
PubMed1991

Serotoninergic innervation of the ferret cerebral cortex. I. Adult pattern.

We have investigated the serotoninergic innervation of the adult ferret cerebral cortex with immunohistochemical techniques. Distribution pattern of serotoninergic fibers in the ferret neocortex is characterized by a decrease in the density of fibers as one moves from the pial surface towards the white matter. Throughout the entire cerebral cortex, the serotoninergic fibers are very dense within the supragranular layers, especially within layer 1. In contrast, granular and infragranular layers exhibit only a sparse innervation. Although this general pattern of innervation is roughly the same in all cortical areas, significant variations in the fiber density are apparent in different regions. Areas 17, 1, 6, and 8 (primary visual cortex, presumptive somatosensory cortex, presumptive motor cortex, and prefrontal cortex, respectively) are described in more detail to illustrate the diversity of the serotoninergic innervation patterns. The density of innervation is highest in areas 1 and 6, intermediate in area 8, and lowest in area 17. It is noteworthy that while areas 1, 6, and 8 show a marked decrease in fiber density at the boundary between layer 3 and 4, the less strongly innervated area 17 shows a change in density in the transition from layer 2 to layer 3. The types of fibers found within the ferret cortex are similar to those described in other mammalian species. The bulk of the innervation is made by very fine fusiform axons with small ovoid varicosities. In addition to this fiber type, axons with thick round varicosities and some smooth nonvaricose axons were found. The latter types occur in very small numbers within the supragranular layers and mostly in more anterior cortical regions. While the general innervation pattern and the fiber types are similar to those described in the cat cerebral cortex, the pericellular baskets found in the cat cortex (Mulligan and Törk, J Comp Neurol 270:86-110, 1988) are not seen in the ferret.

Animals↗
PubMed1992

Subdivisions and connections of auditory cortex in owl monkeys.

The organization and connections of auditory cortex in owl monkeys, Aotus trivirgatus, were investigated by combining microelectrode mapping methods with studies of architecture and connections in the same animals. In most experiments, portions of auditory cortex were first explored with microelectrodes, neurons were characterized as responsive or not to auditory stimuli, and best frequencies were determined whenever possible. Most recordings were in cortex previously designated as primary (A-I) and rostral (R) auditory fields (Imig et al. J Comp Neurol 171:111, '77) and in a newly defined rostrotemporal field (RT) located rostral to R. Injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and fluorescent tracers were placed in electrophysiologically identified locations of A-I, R, and RT; the posterolateral (PL) and anterolateral (AL) divisions of a narrow belt of auditory cortex lateral and adjacent to A-I and R; cortex of the superior temporal gyrus lateral and rostrolateral to PL and AL; and regions of prefrontal cortex that receive inputs from auditory cortex. There were several major findings: 1. Best frequencies were most clearly determined for neurons within a densely myelinated strip of cortex on the lower bank and lip of the lateral sulcus. We divided this strip into three fields, A-I, R, and RT, although an alternative interpretation that A-I and R are parts of a single field remains tenable. In some cases, isofrequency contours appeared to continue uninterrupted across fields A-I and R, with lower frequencies represented laterally and higher frequencies represented deeper in the sulcus. In other cases, there was a tendency for high frequencies to be represented caudally and medially, and low frequencies laterally in A-I and rostrally in R, with partial discontinuity in the isofrequency contours. A reversal of the tonotopic gradient appeared in RT with a common low-frequency representation at the caudal border with R, and progressively higher frequencies encountered rostrally. Of the three fields, A-I appears slightly more myelinated than R, and RT slightly less than R. The distinctiveness of the three fields is further demonstrated by the patterns of connections. In particular, A-I and RT are both interconnected with R, but not with each other. Connections between A-I and R are between tonotopically matched locations. 2. A narrow 2-3 mm wide band of cortex lateral to A-I, R, and RT was also responsive to auditory stimuli, but typically neurons were more difficult to activate, and best frequencies were more difficult to determine. No distinctions in myeloarchitecture or CO activity were obvious.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1994

Parietal, temporal, and occipital projections to cortex of the superior temporal sulcus in the rhesus monkey: a retrograde tracer study.

The afferent cortical connections of individual cytoarchitectonic areas within the superior temporal sulcus (STS) of the rhesus monkey were studied by retrograde tracer techniques, including double tracer experiments. Rostral superior temporal polysensory (STP) cortex (area TPO-1) receives input from the rostral superior temporal gyrus (STG), cortex of the circular sulcus, and parahippocampal gyrus (PHG) (areas 35, TF, and TL). Mid-STP cortex (areas TPO-2 and -3) has input from the mid-STG, cortex of the mid-circular sulcus, caudal inferior parietal lobule (IPL), cingulate gyrus (areas, 23, 24, retrosplenial cortex), and mid-PHG (areas 28, TF, TH, and TL). Caudal STP cortex (area TPO-4) has afferent connections with the caudal STG, cortex of the caudal insula and caudal circular sulcus, caudal IPL, lower bank of the intraparietal sulcus (IPS), medial parietal lobe, cingulate gyrus, and mid- and caudal PHG (areas TF, TH, TL; prostriate area). The most rostral cortex of the lower bank of the STS (areas TEa and TEm), a presumed visual association area, receives input from the rostral inferotemporal (IT) region; more caudal portions of areas TEa and TEm have afferent connections with the caudal IT region, PHG, preoccipital gyrus, and cortex of the lower bank of the IPS.

Afferent Pathways↗
PubMed1995

Projections from visual areas of the cerebral cortex to pretectal nuclear complex, terminal accessory optic nuclei, and superior colliculus in macaque monkey.

The purpose of this study was to analyze the projections from visually related areas of the cerebral cortex of rhesus monkey to subcortical nuclei involved in eye-movement control; i.e., the pretectal nuclear complex, the terminal nuclei of the accessory optic system (AOS), and the superior colliculus (SC). The anterograde tracer 3H-leucine was pressure injected bilaterally into the cortex of six monkeys (for a total of 12 cases) involving the primary visual cortex (area 17); the medial prestriate cortex (medial 18/19); dorsomedial area 19; the caudal portion of the cortex of the superior temporal sulcus, upper bank (cytoarchitectural area OAa) and lower bank (area PGa); the lower bank of the caudal lateral intraparietal sulcus (area POa); and the inferior parietal lobule (area 7). The results revealed that the pretectal nucleus of the optic tract received inputs from medial prestriate cortex, dorsomedial part of area 19, OAa, and PGa. The posterior pretectal nucleus received sparse projections from area 7 and the cortex lining the intraparietal sulcus (dorsomedial part of area 19 and POa). The pretectal olivary nucleus was targeted by neurons in cortex of dorsomedial area 19, and the anterior pretectal nucleus was targeted by neurons in both dorsomedial 19 and area 7. The nuclei of the AOS (dorsal terminal; lateral terminal; and interstitial nuclei of the superior fasciculus, posterior and medial fibers) received projections exclusively from areas OAa and PGa. Furthermore, in one case with PGa injection, the medial terminal nucleus, dorsal portion, was also labeled. The visual cortical areas studied projected differentially upon the SC laminae. The primary visual area 17 projected only to the superficial laminae, i.e., stratum zonale (SZ), stratum griseum superficiale (SGS), and stratum opticum (SO). On the other hand, the medial portion of the prestriate cortex and caudal OAa and PGa targeted the superficial and intermediate laminae, i.e., SZ, SGS, SO, and stratum griseum intermediale (SGI), whereas caudal area POa projected primarily to the intermediate layer SGI. Rostral area 7 (mainly 7b) neurons terminated in the stratum album intermediale (SAI); no SC terminals were found in a case in which caudal area 7 (mainly 7a) was injected.

Animals↗
PubMed2004

The microstructural border between the motor and the cognitive domain in the human cerebral cortex.

When we voluntarily interact with our environment, the agranular frontal cortex (Brodmann's areas 4 and 6) plays a pivotal role in cortical motor control. The primary motor cortex (area 4) influences kinematic and dynamic parameters of movements, whereas the rostrally adjoining nonprimary motor cortex (area 6) uses external (e.g., sensory) or internal cues to trigger and guide movements. Once thought to be homogeneous, data from nonhuman primates have shown that area 6 is a mosaic of areas, each with distinct structural and functional properties: the supplementary motor areas "SMA proper" and "pre-SMA" on the mesial cortical surface, and the dorso- and ventrolateral premotor cortex on the cortical convexity. Dorso- and ventrolateral premotor areas are specifically connected with posterior parietal areas. These parieto-frontal circuits work in parallel and tranform different aspects of sensory information into appropriate motor commands. The rostral border of area 6 is very important for functional neuroimaging studies in humans since it separates the "motor domain" of the supplementary motor/premotor cortex from the "cognitive domain" of the prefrontal cortex. Can the topography of this border be inferred from the gyral pattern of the frontal lobe? To answer this, ten postmorterm brains were scanned with a T1-weighted magnetic resonance sequence. The brains were serially sectioned at 20 micro M and area 6 was defined by subjective and objective cytoarchitectonic analysis. Each brain's histological volume (with the representation of area 6) was reconstructed in 3-D and spatially normalized to the reference brain of a computerized atlas. The ten normalized volumes were superimposed and a population map was generated that describes, for each voxel, how many brains have a representation of area 6. On the mesial coetical surface, the rostral border of area 6 lies rostral to the anterior commissure-- though the distance varies across different brains. On the lateral convexity, the border recedes in a caudal direction-- again to a varying degree in different brains-- and lies on the precentral gyrus close to the sylvian fissure. No macroanatomical landmark indicates the border between area 6 and the prefrontal cortex. The question whether a motor task engages only the "motor domain" of the supplementary motor/premotor cortex or in addition the "cognitive domain" of the prefrontal cortex can only be answered by superimposing the functional activation map with the microstructural population map of area 6.

Animals↗
PubMed1995

Postnatal migration of neurons and formation of laminae in rat cerebral cortex.

Migration of neurons and formation of laminae in the developing neocortex were studied by means of thymidine autoradiography. Timed pregnant rats received a single pulse injection of [3H]thymidine in the morning of embryonic day (E)13, 14, 15, 16, 17, 18 or 19. Pups were killed on postnatal day (P)0, 1, 2, 3, 4, 6, 10, 30, or 60 and brains were processed for autoradiography. Neurons in posterior (visual) cortical areas labeled by [3H]thymidine administration on E13 or E14 were found predominantly in the cortical subplate; cells labeled on E15 in layer VI; cells labeled on E16 in layers VI and V, cells labeled on E17 in layers V and IV; E18 in layers IV and III; and E19 in layers III and II. By the day of birth (P0), neurons labeled from E13-16 injections were already in their mature laminae in cortex. Many of the cells labeled on E17 were still situated within the cell-dense cortical plate (CP) at P0, and within layer V by P1. Cells labeled on E18 were found in the most superficial part of the CP on P0, in the deep part of the CP on P1, and formed layer IV on P2 and P3. At P0, many E19 labeled cells appeared to be in migration to the cortex and were found in the CP on P1, in layer III by P4, and in layer II by P6. Cells in the auditory cortex labeled by [3H]thymidine injections on a particular day were situated more superficially than comparable labeled cells in the visual cortex, indicating a lateral to medial gradient in which the auditory cortex is formed earlier than the visual cortex. Distributions of labeled cells in the somatosensory cortex were similar to those in the visual cortex. These data provide a detailed and comprehensive description of the position of varied populations of cortical neurons during the early postnatal period, as well as a description of the formation of cortical laminae at times when major systems of afferents are growing into the cortex and making synaptic connections with their target cells.

Afferent Pathways↗
PubMed1987

Responses of neurons in the inferior temporal cortex in short term and serial recognition memory tasks.

Gaffan and Weiskrantz (1980) and Mishkin (1982) have shown that lesions to the inferior temporal visual cortex can impair the performance of serial visual recognition memory tasks. In order to provide evidence on whether the inferior temporal visual cortex contains a mechanism which enables memory to span the intervening items in a serial recognition task, or whether the inferior temporal cortex is merely afferent to such recent memory mechanisms, we analysed the activity of single neurons in the inferior temporal visual cortex and the adjacent cortex in the superior temporal sulcus in both delayed match to sample and serial recognition memory tasks. In the serial recognition task, various numbers of stimuli intervened between the first and second presentations of a stimulus. A considerable proportion (64/264 or 26%) of visually responsive inferotemporal neurons showed a different response to the "novel" and "familiar" presentations of a stimulus in the serial recognition memory task, and often a corresponding difference in response between the sample and match presentations of a stimulus in the delayed match to sample task. For the majority of neurons this difference was not sustained across even one intervening stimulus in the serial recognition task, and no neurons bridged more than 2 intervening stimuli. These results show that neurons in the inferior temporal cortex have responses which would be useful for a short term visual memory for stimuli, but would not be useful in recency memory tasks in which more than one stimulus intervenes between the first and second presentations of a stimulus. In this investigation, neurons were recorded both in the cortex on the inferior temporal gyrus (commonly called inferior temporal visual cortex, and consisting of areas TE3, TE2 and TE1 of Seltzer and Pandya 1978), and in the cortex in the adjacent anterior part of the superior temporal sulcus, in which a number of different temporal cortical visual areas have now been described.

Animals↗
PubMed1989

Projection patterns of surviving neurons in the dorsal lateral geniculate nucleus following discrete lesions of striate cortex: implications for residual vision.

In four monkeys with long-standing partial ablation of the striate cortex pellets of horseradish peroxidase were placed in either the striate cortex immediately adjacent to the ablation, or in the extrastriate cortex of the ventral prelunate gyrus, i.e. in visual area V4. We examined the dorsal lateral geniculate nucleus to see whether surviving neurons, within the region that shows retrograde degeneration as a result of the cortical lesion, project to remaining striate cortex and/or to extrastriate cortex. Neurons labelled from extrastriate cortex were found throughout the degenerated region, whereas neurons labelled from striate cortex were confined to the border between the normal and degenerated region of the nucleus. This shows that isolated neurons found within the degenerated region survive striate cortex damage because they project to an extrastriate visual area, and not because their terminals depart from the otherwise strict topographic representation of the lateral geniculate nucleus on to striate cortex.

Animals↗
PubMed1996

Mianserin markedly and selectively increases extracellular dopamine in the prefrontal cortex as compared to the nucleus accumbens of the rat.

The atypical antidepressant mianserin, administered at doses of 1, 5 and 10 mg/kg SC, dose-dependently increased up to about 6 times extracellular dopamine in the medial prefrontal cortex of the rat, as estimated by vertical concentric microdialysis probes. Mianserin failed to modify extracellular dopamine in the nucleus accumbens. Mianserin also dose-dependently increased extracellular noradrenaline in the prefrontal cortex. Yohimbine, an alpha2 antagonist, increased extracellular dopamine in the prefrontal cortex but the maximal increase was lower than that elicited by mianserin. Yohimbine also increased extracellular noradrenaline in the prefrontal cortex, but to a lesser extent than dopamine. Clonidine, an alpha2 antagonist, decreased extracellular dopamine and noradrenaline in the prefrontal cortex but failed to affect extracellular dopamine in the nucleus accumbens. Ritanserin, a 5HT2 antagonist, at doses of 1.0 mg/kg, failed to increase extracellular dopamine in the prefrontal cortex, but significantly potentiated the increase in extracellular noradrenaline due to yohimbine. Ritanserin failed to potentiate the increase in extracellular noradrenaline elicited by yohimbine in the prefrontal cortex. The results are interpreted to indicate that mianserin increases extracellular DA as a result of the concurrent blockade of alpha2 and 5HT2 receptors. Failure to affect extracellular dopamine in the nucleus accumbens is explained as due to the lack of a significant effect of alpha2 and 5HT2 tone on DA release in the nucleus accumbens as compared to the prefrontal cortex. The results are consistent with the postulated relationship between antidepressant drug action and the ability to increase extracellular dopamine in the prefrontal cortex.

Animals↗
PubMed1997

Pharmacological characterisation of human cerebral cortex somatostatin SRIF1 and SRIF2 receptors.

Radioligand binding studies were performed in membranes of human cerebral cortex using [125I]Tyr3-octreotide in the presence of 5 mM MgCl2, [125I]SRIF-14 ([125I]Tyr11-SRIF-14) and [125I]CGP 23996 ([125I]c[Asu- Lys-Asn-Phe-Phe-Trp-Lys-Thr-Tyr-Thr-Ser]) both in the presence of 120 mM NaCl, to characterise the nature of the somatostatin (SRIF) receptors. The pharmacological profile of human brain SRIF recognition sites was compared with that of recombinant human SRIF1 (sst2-sst3-sst5) or SRIF2 receptors (sst1-sst4) and with that of native rat sst1, sst2, and sst4 receptors. [125I]Tyr3-octreotide labelled binding sites in human cerebral cortex: Bmax = 238 +/- 36 fmol/mg protein and pKd = 9.73 +/- 0.08. The pharmacological profile of [125I]Tyr3-octreotide labelled sites correlated very significantly with that of recombinant human sst2 receptors (r = 0.98) and much less with those of recombinant human sst3 (r = 0.65) or sst5 receptors (r = 0.72). The correlation between [125I]Tyr3-octreotide binding to native sst2 receptors in human and rat cerebral cortex was also highly significant (r = 0.97). [125I]SRIF-14 and [125I]CGP 23996 binding (performed in the presence of 120 mM NaCl) in the human cerebral cortex identified very similar populations of sites Bmax = 44 +/- 7 and 36 +/- 5 fmol/mg protein and pKd = 9.44 +/- 0.08 and 9.48 +/- 0.10, respectively. The pharmacological profiles of the sites labelled with [125I]SRIF-14 and [125I]CGP 23996 correlated highly significantly with those of recombinant human sst1 (r = 0.97-0.99) or sst4 receptors (r = 0.91-0.94). Similarly, the correlations between [125I]SRIF-14 or [125I]CGP 23996 binding in human cortex and [125I]SRIF-14 binding to native sst1 sites in rat cerebral cortex were also highly significant (r = 0.97 and 0.94, respectively). Finally, the pharmacological profile of native rat lung sst4 sites determined with [125I]LTT-SRIF-28 ([Leu8,D-Trp22, 125I-Tyr25]SRIF-28) correlated with [125I]SRIF-14 and [125I]CGP 23996 binding in human cortex; r = 0.91 and 0.87, respectively. The present data show that in human cerebral cortex, [125I]Tyr3-octreotide labels SRIF1 receptor sites which are best characterised as of the sst2 type, whereas [125I]SRIF-14 and [125I]CGP 23996 (both in the presence of 120 mM NaCl), label sites which fit almost equally well with sst1 or sst4 receptors and therefore are best described as of the SRIF2 type. Under the conditions used, there was no evidence that either of these ligands would label sst3 or sst5 receptors in human cerebral cortex.

Animals↗
PubMed2006

A 3 T event-related functional magnetic resonance imaging (fMRI) study of primary and secondary gustatory cortex localization using natural tastants.

INTRODUCTION: It is known that taste is centrally represented in the insula, frontal and parietal operculum, as well as in the orbitofrontal cortex (secondary gustatory cortex). In functional MRI (fMRI) experiments activation in the insula has been confirmed, but activation in the orbitofrontal cortex is only infrequently found, especially at higher field strengths (3 T). Due to large susceptibility artefacts, the orbitofrontal cortex is a difficult region to examine with fMRI. Our aim was to localize taste in the human cortex at 3 T, specifically in the orbitofrontal cortex as well as in the primary gustatory cortex. METHODS: Event-related fMRI was performed at 3 T in seven healthy volunteers. Taste stimuli consisted of lemon juice and chocolate. To visualize activation in the orbitofrontal cortex a dedicated 3D SENSE EPI fMRI sequence was used, in addition to a 2D SENSE EPI fMRI sequence for imaging the entire brain. Data were analyzed using a perception-based model. RESULTS: The dedicated 3D SENSE EPI sequence successfully reduced susceptibility artefacts in the orbitofrontal area. Significant taste-related activation was found in the orbitofrontal and insular cortices. CONCLUSION: fMRI of the orbitofrontal cortex is feasible at 3 T, using a dedicated sequence. Our results corroborate findings from previous studies.

Adult↗
PubMed2004

Thalamic projections to the auditory cortex in the rufous horseshoe bat (Rhinolophus rouxi). II. Dorsal fields.

In this study, we analyzed the thalamic connections to the parietal or dorsal auditory cortical fields of the horseshoe bat, Rhinolophus rouxi. The data of the present study were collected as part of a combined investigation of physiologic properties, neuroarchitecture, and chemoarchitecture as well as connectivity of cortical fields in Rhinolophus, in order to establish a neuroanatomically and functionally coherent view of the auditory cortex. Horseradish peroxidase or wheat-germ-agglutinated horseradish peroxidase deposits were made into cortical fields after mapping response properties. The dorsal fields of the auditory cortex span nearly the entire parietal region and comprise more than half of the non-primary auditory cortex. In contrast to the temporal fields of the auditory cortex, which receive input mainly from the ventral medial geniculate body (or "main sensory nucleus"), the dorsal fields of the auditory cortex receive strong input from the "associated nuclei" of the medial geniculate body, especially from the anterior dorsal nucleus of the medial geniculate body. The anterior dorsal nucleus is as significant for the dorsal fields of the auditory cortex as the ventral nucleus of the medial geniculate body is for the temporal fields of the auditory cortex. Additionally, the multisensory nuclei of the medial geniculate body provide a large share of the total input to the nonprimary fields of the auditory cortex. Comparing the organization of thalamic auditory cortical afferents in Rhinolophus with other species demonstrates the strong organizational similarity of this bat's auditory cortex with that of other mammals, including primates, and provides further evidence that the bat is a relevant and valuable model for studying mammalian auditory function.

Animals↗
PubMed1992

Calretinin-immunoreactive neurons in the primary visual cortex of dolphin and human brains.

A new class of gamma-aminobutyric acid (GABA)ergic neurons immunoreactive to the calcium-binding protein calretinin (CR) was demonstrated in primary visual cortices of the bottlenose dolphin (Tursiops truncatus) and humans (Homo sapiens). Comparative analysis revealed several differences between dolphin and human visual cortex in the laminar distribution of CR-positive perikarya, although general typology of the immunoreactive CR-positive neurons was similar in both species. Thus, in both human and dolphin primary visual cortex almost all CR-positive neurons are non-pyramidal, either fusiform or bipolar cells, oriented with their long axis along the radial axis of the cortex. Large multipolar stellate cells were also observed in layers I and VI. The CR-positive neurons in the dolphin visual cortex are concentrated almost exclusively in layer I and, to a lesser extent, in layer II. In all other layers (IIIa, b, IIIc/V and VI) of the dolphin visual cortex CR-positive neurons were only rarely seen. In the human primary visual cortex CR-positive neurons are located mainly in layers II, III and IVa, b, c, with considerably lower densities of these cells observed in layers V and VI. CR-positive neurons in layer I of the human visual cortex are represented by Cajal-Retzius horizontal cells, whereas no such cells were seen in layer I of the dolphin neocortex. The numerical density of CR-positive neurons in the dolphin primary visual cortex is significantly lower than in the area of cortex in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1996

Age-related change of neuropeptide Y-immunoreactive neurons in the cerebral cortex of aged rats.

Recent studies have explored certain changes with aging of neurons containing neuropeptides. The extent of loss in aged central nervous system (CNS) of neuronal cells containing neuropeptide Y (NPY) has not yet been established with certainty, and available data is often contradictory. Changes of NPY-containing neurons with aging in the cerebral cortex of aged rat were demonstrated by immunocytochemistry. A major loss of NPY-immunoreactive (ir) neurons in the aged rat brain was observed in the retrosplenial cortex, frontal cortex area 1 and 2, parietal cortex area 1 and 2, occipital cortex area 1 and 2, temporal cortex area 3, cingulate cortex and the hippocampus proper. A loss of NPY-ir neurons was observed mostly in layers V and VI; in addition, the number and length of dendritic branches appeared to be decreased and shortened in the age group. These results indicate the involvement of NPY-ir neurons in the aging process of cerebral cortex, and provide the first morphological evidence for the loss of NPY neurons in the cerebral cortex of aged rats.

Aging↗
PubMed1995

Ultrastructural analysis of tryptophan hydroxylase immunoreactive nerve terminals in the rat cerebral cortex and hippocampus: their associations with local blood vessels.

Physiological evidence has indicated that serotonin (5-hydroxytryptamine) could be a regulator of cerebral blood flow in various regions of the brain. In the present study, tryptophan hydroxylase immunocytochemistry was used to characterize, both at the light and electron microscopic levels, serotonergic nerve terminals and primarily their relationships with intraparenchymal microarterioles and capillaries in the rat frontoparietal cortex, entorhinal cortex and hippocampus. Irrespective of the brain area, serotonergic varicosities were primarily apposed to either dendrites or nerve terminals, were on average 0.37 micron2 in surface area (0.69 micron calculated diameter) and 12-22% of them engaged in synaptic junctions, mostly with dendritic elements. Perivascular terminals (defined as immunolabelled varicosities located within a 3 micron perimeter around the vessel basal lamina) in the frontoparietal cortex represented 8-11% of all immunoreactive terminals counted, as determined by light and electron microscopy, respectively. In the entorhinal cortex and hippocampus, the proportion of perivascular terminals was only determined at the ultrastructural level and corresponded to 10% and 4%, respectively. In the frontoparietal cortex, serotonergic varicosities were located significantly closer (n = 250, 0.98 +/- 0.05 micron; P < 0.001) to the blood vessels than those of the entorhinal cortex (n = 116, 1.41 +/- 0.08 microns) or hippocampus (n = 105, 1.31 +/- 0.08 microns). Of all perivascular serotonergic terminals in the frontoparietal cortex, 26% were in the immediate vicinity (0-0.25 micron) of the vessel wall, with 2.8% directly abutting on the basement membrane, while 11.6% were separated from it only by a thin astrocytic leaflet. This situation contrasts with that observed in the entorhinal cortex and hippocampus, where no immunoreactive varicosity was ever seen directly contacting the vessel basal lamina and with only 10-13% of the terminals being within 0.25 micron from the vessels. The surface area of perivascular serotonergic terminals was comparable in all regions studied and corresponded to 0.22 micron2; these virtually never engaged in synaptic contacts with adjacent neuronal structures. Our results indicate that tryptophan hydroxylase-immunolabelled terminals are identical to previously characterized serotonin-containing varicosities. Furthermore, the present data show intimate associations between serotonergic terminals and microvessels in the three regions examined. However, perivascular terminals in the frontoparietal cortex were more frequent and/or located much closer to local microvessels than those in the other regions, and might be more directly involved in neurogenic control of local cerebral blood flow.

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