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J F Staiger

Publications and source records attributed to J F Staiger.

32 records · Page 2Linked to original sources
PubMed1997

Interneurons immunoreactive for vasoactive intestinal polypeptide (VIP) are extensively innervated by parvalbumin-containing boutons in rat primary somatosensory cortex.

Sensory perception results from the synchronized action of large ensembles of cortical neurons. Receptive field properties of such neurons in sensory areas strongly depend on circuits utilizing the inhibitory amino acid transmitter gamma-aminobutyric acid (GABA). GABAergic neurons often co-localize neuropeptides and/or calcium-binding proteins in a cell-type specific manner. We have taken advantage of this fact to study the synaptic circuitry involving presynaptic parvalbumin-containing boutons (originating from horizontally extensive basket cells) and postsynaptic VIP-immunoreactive GABAergic targets which mostly have a vertically oriented axonal field. Abundant appositions between parvalbumin-immunoreactive boutons and all VIP-stained neurons were observed at the light microscopic level. The numbers of contacts ranged between three and well over 20 for single VIP cells. The higher numbers were especially frequent in the supragranular and granular layers contacting the numerous bipolar, as well as multipolar VIP cells located there; but the VIP-immunoreactive neurons in the infragranular layers were also targeted by parvalbumin-immunoreactive boutons without exception, albeit in more variable, mostly lower numbers. Correlated electron microscopic investigations revealed that virtually all of these light microscopically observed appositions resembled symmetric synaptic specializations. The vast majority were located on the soma or proximal dendrites of the VIP-positive neurons. Since pyramidal cells, in turn, represent a major target for the parvalbumin and VIP synapses, the activation of these synapses may lead to coherent oscillations providing the necessary clock function to synchronize pyramidal cell discharges, both across and within cortical columns.

Animals↗
PubMed1996

Innervation of VIP-immunoreactive neurons by the ventroposteromedial thalamic nucleus in the barrel cortex of the rat.

We investigated the synaptic terminals of fibers originating in the ventroposteromedial thalamic nucleus (VPM) and projecting to the main input layers (IV/III) of the rat posteromedial barrel subfield. It was our aim to determine whether or not the subpopulation of vasoactive intestinal polypeptide (VIP)-immunoreactive neurons in these layers are directly innervated by the sensory thalamus. Anterograde tracing with Phaseolus vulgaris leucoagglutinin (PHA-L) and immunohistochemistry for VIP were combined for correlated light and electron microscopic examination. Columns of cortical tissue were well defined by barrel-like patches of PHA-L-labeled fibers and boutons in layers IV and III. Within these columns VIP-immunoreactive perikarya were located mainly in supragranular layers. Marked perikarya were also seen in infragranular layers, but their immunoreactivity was often weaker. Granular layer IV, which is the main terminal field for thalamic fibers, contained fewer VIP neurons than supragranular layers. In the light microscope, however, PHA-L-labeled fibers appeared to contact the somata or proximal dendrites of 60-86% of the layer IV VIP neurons . By contrast, only 18-35% of the VIP neurons in the supragranular layers, which receive a moderately dense projection from the VPM, appeared to be contacted. PHA-L-labeled boutons were seen close to 13-25% of infragranular VIP-positive cells. Electron microscopy showed that thalamic fibers formed at most four asymmetric synapses on a single layer IV, VIP-positive neuron. Although the proportion of VIP-positive neurons with labeled synapses was lower in supragranular layers, most of them shared multiple asymmetric synapses with labeled thalamic fibers. Up to six labeled synapses were seen on individual VIP neurons in layer III. We conclude that subpopulations of VIP-immunoreactive neurons, located in layers IV, III, and II are directly innervated by the VPM. These neurons may be involved in the initial stages of cortical processing of sensory information from the large, mystacial vibrissae. Since VIP is known to be colocalized with the inhibitory transmitter GABA, it is likely that VIP neurons participate in the shaping of the receptive fields in the barrel cortex.

Afferent Pathways↗
PubMed1996

Recurrent axon collaterals of corticothalamic projection neurons in rat primary somatosensory cortex contribute to excitatory and inhibitory feedback-loops.

Intrinsic circuitry within the primary somatosensory cortex of the rat was examined in a combined light and electron microscope study. Corticothalamic projection neurons were retrogradely labeled by applying Phaseolus vulgaris leucoagglutinin (PHA-L) into the ventro-posteromedial thalamic nucleus (VPM). Most labeled neurons were pyramidal cells of layer VI. Postsynaptic targets of recurrent axon collaterals originating from these neurons were assessed in layers IV and V. Single labeled cells, complete with recurrent collaterals, could be isolated in "barrels" in which no anterograde transport had taken place. These findings were confirmed by first eliminating thalamocortical projections from the VPM with kainic acid and then applying PHA-L into the same nucleus. This procedure led to selective retrograde accumulation of tracer in layer VI pyramidal cells. Reconstructed portions of labeled axonal trees reached layer IV, bringing numerous boutons to layers IV, V and VI. The boutons had characteristic drumstick-like shapes. In order to identify postsynaptic targets, 4 sections of axons stemming from 3 neurons were reembedded and serially sectioned for electron microscopy. The ultrastructure of 72 asymmetric synapses, all belonging to identified collaterals, was analysed. Of the 72 terminals, 44 (59.5%) ended on dendritic spines and 30 on shafts of dendrites (40.5%). Perikarya were not among the targets. In a subset of the sample, the nature of the target neurons was examined by postembedding immunohistochemistry for gamma-amino butyric acid (GABA) after staining for PHA-L. A total of 42 labeled terminals was found in layers IV and V; 23 (55%) were located on GABA-negative spines and 19 (45%) on dendritic shafts. Only 6 (32%) of the shafts were GABA-positive. The remaining ones were either clearly GABA-negative, or labeled only at background levels (n = 13; 68%). The results show that most synapses of corticothalamic projection neurons found in layers IV and V terminate on spines and shafts of GABA-negative dendrites. This finding suggests that such recurrent collaterals are involved in both excitatory and inhibitory feedback mechanisms.

Animals↗
PubMed1996

Distribution of GABAergic elements postsynaptic to ventroposteromedial thalamic projections in layer IV of rat barrel cortex.

The spatial synaptic pattern formed by boutons, originating in the ventroposteromedial thalamic nucleus, with GABAergic neurons in the rat barrel cortex was mapped. The aim was to shed light on the structural basis by which inhibitory circuits may be activated at the first stage of cortical information processing. The thalamic afferent projection was labelled by anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L), whereas the GABAergic targets in layer IV of the rat barrel cortex was visualized by postembedding GABA immunogold-labelling or by pre-embedding parvalbumin immunocytochemistry. In the first set of experiments, we mapped barrels, contained in single ultrathin sections, by means of a computer-controlled electron microscope stage in their entire layer IV representation. From a total of 1199 asymmetric PHA-L-labelled synapses, only 98 were on GABAergic elements, mainly on dendritic shafts. This corresponded to 8.2% of all synapses counted. These synapses on GABAergic targets were essentially homogeneously distributed without a reliable relationship to barrel subdivisions, i.e., hollow versus wall; or layer IVa versus layer IVb. In the second part of the study, we demonstrated that parvalbumin-containing neurons represent the major GABAergic cell type targetted by thalamic afferents in layer IV of the barrel cortex, since all parvalbumin-positive cells investigated received multiple synaptic contacts (up to eight synapses per neuron) from the ventroposteromedial thalamic nucleus. These results imply that interneurons responsible for perisomatic inhibition (basket and chandelier cells known to contain parvalbumin) are likely to be strongly excited by thalamic afferents, despite the relatively low proportion of thalamic synapses on GABAergic elements compared to spines of principal cells, and participate in the early stages of cortical sensory information processing.

Animals↗
PubMed1995

Corpus callosum and brain volume in women and men.

Using high-resolution in vivo magnetic resonance morphometry we measured the midsagittal area of the corpus callosum and total forebrain volume in 120 healthy young adults (mean age (+/- s.d.) 25.7 +/- 4.7 years). The forebrain volume-adjusted size of the corpus callosum was larger in women than in men (32 mm2 mean difference; p = 0.011). Handedness had no effect in this measurement. The morphometric data confirm a gender difference in cerebral structural organization.

Adult↗
PubMed1995

Increased corpus callosum size in musicians.

Using in-vivo magnetic resonance morphometry it was investigated whether the midsagittal area of the corpus callosum (CC) would differ between 30 professional musicians and 30 age-, sex- and handedness-matched controls. Our analyses revealed that the anterior half of the CC was significantly larger in musicians. This difference was due to the larger anterior CC in the subgroup of musicians who had begun musical training before the age of 7. Since anatomic studies have provided evidence for a positive correlation between midsagittal callosal size and the number of fibers crossing through the CC, these data indicate a difference in interhemispheric communication and possibly in hemispheric (a)symmetry of sensorimotor areas. Our results are also compatible with plastic changes of components of the CC during a maturation period within the first decade of human life, similar to those observed in animal studies.

Adult↗
PubMed1992

Restricted origin and distribution of projections from the lateral to the medial septal complex in rat and guinea pig.

The origin and distribution of projections from the lateral to the medial septal complex were studied at the light- and electron-microscopical level in the rat and the guinea pig, with the use of sensitive anterograde tracing techniques. Injections in the lateral septal complex resulted in only weak to moderate labeling in the medial septal nucleus. In contrast, injections in all but the ventral subdivision of the lateral septal complex labeled restricted terminal arborizations in the angular portions of the vertical diagonal band. Analyses at the electron-microscopical level indicated that these fibers form both symmetrical and asymmetrical synapses with dendrites and somata, but not with axons. These findings are discussed in the light of a presumed functional circuit from the hippocampal formation, via the lateral septal complex, to cells in the medial septal complex that originate projections to the hippocampal formation.

Animals↗
PubMed1991

The efferent connections of the lateral septal nucleus in the guinea pig: projections to the diencephalon and brainstem.

The anterograde Phaseolus vulgaris-leucoagglutinin (PHA-L) tracing technique was used to determine the distribution of efferent fibers originating in the lateral septal nucleus of the guinea pig. For complementary detection of the chemical identity of the target neurons, double-labeling immunocytochemistry was performed with antibodies to PHA-L and to vasopressin, oxytocin, vasoactive intestinal polypeptide, serotonin or dopamine beta-hydroxylase, respectively. The hypothalamus received the majority of the PHA-L-stained septofugal fibers. Here, a specific topography was observed. (1) The medial and lateral preoptic area, (2) the anterior, lateral, dorsal, posterior hypothalamic and retrochiasmatic area, (3) the supraoptic, paraventricular, suprachiasmatic, dorsomedial, caudal ventromedial and arcuate nuclei, and (4) the tuberomammillary, medial and lateral supramammillary, dorsal and ventral premammillary nuclei always contained PHA-L-labeled fibers. The rostral portion of the ventromedial nucleus and the medial and lateral mammillary nucleus only occasionally showed weak terminal labeling. In other diencephalic areas, termination of PHA-L-labeled fibers was observed in the epithalamus and the nuclei of the midline region of the thalamus. In the mesencephalon, terminal varicosities occurred in the ventral tegmental area, interfascicular and interpeduncular nucleus, and periaqueductal gray. In addition, the dorsal and medial raphe nuclei of the metencephalon, together with the locus coeruleus and the dorsal tegmental nucleus, received lateral septal efferents.

Animals↗
PubMed1991

The efferent connections of the lateral septal nucleus in the guinea pig: intrinsic connectivity of the septum and projections to other telencephalic areas.

The distribution of efferent fibers originating in the lateral septal nucleus was investigated in guinea pigs by means of anterograde tracing with Phaseolus vulgaris-leucoagglutinin (PHA-L). Special emphasis was placed on the intraseptal fiber systems. The fibers originating from the different subnuclei of the lateral septal nucleus formed massive horizontal connections in the rostrocaudal axis. Projections to the contralateral, congruent subnuclei were also detected. In the medial septum/diagonal band of Broca complex the largest number of PHA-L-stained fibers was found after application of the tracer into the dorsal subnucleus of the lateral septal nucleus; the density of the efferent fibers decreased progressively after injection into the intermediate or ventral subnuclei. In all cases the diagonal band contained a much higher number of efferent fibers from the lateral septal nucleus than from the medial septal nucleus. In the medial septal nucleus, terminal labeling was generally sparse. Other telencephalic areas (organum vasculosum of the lamina terminalis, nucleus accumbens, bed nucleus of the stria terminalis, amygdala, hippocampal complex, and other cortical areas) contained varying numbers of labeled projections. In double-labeling experiments, a close spatial relationship between PHA-L-stained fibers and vasoactive intestinal polypeptide-immunoreactive perikarya was observed in several of these target areas.

Animals↗
PubMed1990

Efferent projections from the lateral septal nucleus to the anterior hypothalamus in the rat: a study combining Phaseolus vulgaris-leucoagglutinin tracing with vasopressin immunocytochemistry.

The tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) was injected into the lateral septum of the rat at different rostrocaudal locations to study the efferent septal projections to the anterior hypothalamus. For spatial correlation of these septofugal elements with the vasopressinergic system a dual immunocytochemical technique was used (i) to demonstrate nerve fibers and their corresponding bouton-like structures labeled with the tracer, and (ii) to identify vasopressin in the same section. The hypothalamic paraventricular and supraoptic nuclei, the accessory hypothalamic magnocellular system, and the suprachiasmatic nucleus are recipients of PHA-L-labeled fibers from all parts of the lateral septum. Close appositions between (i) these axons and their varicosities, and (ii) vasopressin-immunoreactive perikarya and their processes, putatively indicating functional interrelationships, were observed in all these nuclear areas, especially in their neuropil formations.

Animals↗
PubMed1990

Columnar arrangement of lumbar motoneurons innervating a pair of antagonistically acting leg muscles in the rat.

Various problems concerning the physiology of muscular units depend on the exact localization of motoneurons innervating antagonistically acting muscles. The present communication is focussed on the distribution of motoneurons innervating the gastrocnemius (GC) and tibialis anterior (TA) muscles. After injection of horseradish peroxidase (HRP) into these muscles and a survival time ensuring sufficient retrograde transport, the number of motoneurons, their segmental distribution, the mean area covered the labeled cells and the mean diameter of their somata were determined. After injections into the GC-muscle, 129 +/- 6 labeled perikarya were found, and following injections into the TA-muscle, 120 +/- 9 motoneurons were marked with HRP. The motoneurons of both muscles were distributed in spinal cord segments L4-5-6; however, the GC-neurons accumulated in segments L5-6 (approximately 94%) and the TA-neurons in L4-5 (approximately 95%). Although the motoneurons innervating both muscles were located in a rather similar area of the ventral column, i.e. its dorsolateral portion as judged from transverse sections, the GC-motoneurons were situated ventrolaterally to the TA-motoneurons. The measurement of the area of the somata and the mean soma diameter did not reveal any conspicuous differences between both pools of motoneurons. An unimodal distribution pattern of these parameters suggests a broad overlap in the size of alpha-, beta-, and gamma-motoneurons.

Animals↗
PubMed1989

Pattern of afferents to the lateral septum in the guinea pig.

The septal region represents an important telencephalic center integrating neuronal activity of cortical areas with autonomous processes. To support the functional analysis of this brain area in the guinea pig, the afferent connections to the lateral septal nucleus were investigated by the use of iontophoretically applied horseradish peroxidase (HRP). Retrogradely labeled perikarya were located in telencephalic, diencephalic, mesencephalic and metencephalic sites. The subnuclei of the lateral septum (pars dorsalis, intermedia, ventralis, posterior) receive afferents from the (i) medial septal nucleus, diagonal band of Broca (pars horizontalis and pars ventralis), and the principal nucleus of the stria terminalis, the hippocampus, and amygdala (nucleus medialis): (ii) the medial habenular nucleus, and the para- (peri-) ventricular, parataenial and reuniens nuclei of the thalamus; the anterior, lateral and posterior hypothalamic areas (in particular, the medial and lateral preoptic, suprachiasmatic, periventricular, paraventricular, arcuate, premammillary, and supramammillary nuclei; (iii) the periaquaeductal grey, ventral tegmental area, nucleus interfascicularis, nucleus reticularis linearis, central linear nucleus, interpeduncular nucleus; (iv) dorsal and medial raphe complex, and locus coeruleus. Each subnucleus of the lateral septum displays an individual, differing pattern of afferents from the above-described regions. Based on a double-labeling method, the vasopressinergic and serotonergic afferents to the lateral septum were found to originate in the nucleus paraventricularis hypothalami and the raphe nuclei, respectively.

Animals↗
PubMedDate not supplied

The relationship between corpus callosum size and forebrain volume.

Using high-resolution in vivo magnetic resonance morphometry we measured forebrain volume (FBV), midsagittal size of the corpus callosum (CC) and four CC subareas in 120 young and healthy adults (49 women, 71 men). We found moderate linear and quadratic correlations, indicating that the CC and all CC subareas increase with FBV both in men and women (multiple r2 ranging from 0.10 to 0.28). Allometric equations revealed that these increases were less than proportional to FBV (r2 ranging from 0.02 to 0.30). Absolute CC measurements, as well as CC subareas relative to total CC or FBV (the latter measures termed the CC ratios), were further analyzed with regard to possible effects of handedness, gender, or handedness by gender interaction. Contrary to previous reports, left-handers did not show larger CC measurements compared to right-handers. The only apparent influence of gender was on the CC ratios, which were larger in women. However, smaller brains had larger CC ratios which were mainly independent of gender, a result of the less than proportional increase of callosal size with FBV. We suggest that the previously described gender differences in CC anatomy may be better explained by an underlying effect of brain size, with larger brains having relatively smaller callosa. This lends empirical support to the hypothesis that brain size may be an important factor influencing interhemispheric connectivity and lateralization.

Adult↗