bluuebunny/crossref_metadata_2025 huggingface dataset:
Afferents to the zona incerta in the rat: A combined retrograde and anterograde study
Authors: Roger Michel , Cadusseau Josette
Published: May 2005

In a first set of experiments, the retrograde transport of horseradish peroxidase (HRP) was utilized to investigate the afferent projections to the zona incerta (ZI) in the hooded rat. HRP was introduced in its crystalline form into various sectors of the ZI of seven subjects. The largest contingent of afferents arises from the following centers: the cingulate and somatosensory cortices, central amygdaloid nucleus, ventromedial hypothalamic nucleus, posterior thalamic nucleus, anterior pretectal nucleus, peripeduncular area, deep and intermediate layers of the superior colliculus, dorsal and ventral parabrachial nuclei, principal and interpolar trigeminal subnuclei, and cuneate nucleus. Other centers less systematically or more sparsely labeled were the lateral hypothalamic area, ventrobasal complex, lateral geniculate nucleus pars ventralis, medial geniculate nucleus, interstitial nucleus of Cajal, Darkschewitsch nucleus, perirubral fields, cuneiform, tegmental pedunculopontine, and deep mesencephalic reticular nuclei, pontine reticular nucleus pars oralis, lateral and interpositus cerebellar nuclei, and gracile nucleus.

In a second set of experiments, an anterograde tracer (WGA‐HRP) was injected in several centers projecting to the ZI in order to localize their terminal fields within this structure. It has been thus possible to distinguish a ventral zone (ventral sector of pars caudalis and pars ventralis) in which the somesthetic somatosensory cortex, trigeminal complex, and dorsal column nuclei (DCN), collicular, and cerebellar projections terminate, from a dorsal zone (pars dorsalis) to which a limbic input (cingulate cortex and ventromedial hypothalamic nucleus) is directed. In most cases, the labeled terminal fields consisted of well‐delimited, narrow bands disposed obliquely, parallel to the cerebral peduncle or the internal capsule.

The contingent of somatosensory afferents is relatively large and there is a high degree of overlapping between the different somatosensory terminal fields within the ventral ZI. This suggests a participation of this structure in the treatment of somesthetic information and/or in the transmission of noxious stimuli.
The afferent connections of the substantia innominata in the monkey,Macaca fascicularis
Authors: Russchen F. T. , Amaral D. G. , Price J. L.
Published: May 2005

The afferent connections of the substantia innominata and the magnocellular nuclei within it (the nucleus of the horizontal limb of the diagonal band, NHDB, and the nucleus basalis of Meynert, NBM) have been studied with anterograde and retrograde axonal tracing techniques. Prominent inputs arise in the amygdaloid complex, restricted areas of the cerebral cortex, parts of the thalamus and hypothalamus, and nuclei of the lower brainstem.

Autoradiographic tracing experiments indicate that the amygdaloid fibers are distributed throughout the NHDB and the NBM, and to a lesser extent to the ventral pallidum. Relatively few fibers innervate the more medially located nucleus of the vertical limb of the diagonal band (NVDB) and the medial septal nucleus. Visualization of the amygdalofugal fibers with the tracer PHA‐L (Phaseolus vulgarisleuco‐agglutinin) shows that they have varicosities resemblingboutons en passantalong their length in the substantia innominata. Retrograde tracing experiments using WGA‐HRP indicate that the cells of origin of the projection from the amygdala are concentrated in the parvicellular basal nucleus, the caudal part of the magnocellular basal nucleus, the magnocellular accessory basal nucleus, and the central nucleus. Relatively few fibers to the substantia innominata arise in the rostrodorsal part of the magnocellular basal nucleus, or in the lateral or parvicellular accessory basal nuclei.

Cortical cells projecting to the substantia innominata were retrogradely labeled in the orbitofrontal cortex (including areas 11–14 and 25), the rostral insula (especially the agranular area), the rostroventral temporal cortex (including areas 35, 36, and parts of TG and TE), and the piriform and entorhinal cortices. The projections from the orbital and rostral temporal cortex were confirmed with anterograde tracers. Projections to the substantia innominata were not found from the more lateral, dorsal or caudal parts of the cerebral cortex, although fibers from temporal area TA may pass through the dendritic field of the most caudal cells of the NBM.

Diencephalic cells projecting to the substantia innominata are distributed diffusely throughout the preoptic area and hypothalamus, with higher concentration in the lateral preoptic area and in the pre‐, supra‐, and tuberomammillary nuclei. Cells are also found in the midline thalamic nuclei and in the region between the peripeduncular and subparafascicular nuclei.

In the brainstem, high concentrations of cells projecting to the substantia innominata are located in the dorsal and median raphe nuclei, the parabrachial nuclei, and the ventral tegmental area and pars compacta of the substantia nigra. There are also cells in the central gray and pedunculopontine region, the reticular formation, the locus coeruleus, and the nucleus of the solitary tract.
The somatotopic organization of forelimb cutaneous nerves in the brachial dorsal horn: An anatomical study in the cat
Authors: Nyberg Gunnar , Blomqvist Anders
Published: May 2005

The projection of forelimb cutaneous nerves to the brachial dorsal horn was studied in the cat by the transganglionic transport method. The results demonstrate a precise somatotopic termination pattern. Afferent nerves from the paw occupy the largest area, with the palm represented most medially in the dorsal horn, followed progressively more laterally by the representations for the palmar and dorsal surfaces of the digits and the dorsum of the paw. The digits are represented in a longitudinal sequence, with the first digit in the caudal part of C6 and the fifth in the caudal part of C8. The projections of the wrist and arm are split, with the line of discontinuity located along the ventral surface of the limb, so that the radial side is represented rostral to the paw and the ulnar side caudal to the paw, with the dorsal surface of the arm represented lateral to the paw. Nerves innervating the skin of the back project to the lateralmost part of the dorsal horn. The degree of overlap or separation of the terminal fields of the nerves along the mediolateral axis of the dorsal horn seems to correspond to the degree of overlap or separation of the peripheral innervation fields. However, along the rostrocaudal axis there appears to be an overlap for which there is no counterpart peripherally.
Ultrastructure of the olfactory neuron of the bullfrog: The dendrite and its microtubules
Authors: Burton Paul R.
Published: May 2005

The ciliated dendritic bulb of the olfactory neuron of the bullfrog was studied with the electron microscope, with emphasis on microtubular elements. Methods used included various fixation procedures with and without detergent extraction, serial sectioning, microtubule polarity assays, and an assay to demonstrate F‐actin. Structural continuity exists, via microtubules, between the ciliary membrane and the perikaryon of the neuron. One type of structural link connects the distal end of the basal body to the plasma membrane and, in slightly oblique cross sections of the basal body, the link shows a highly characteristic tripartite profile resembling a claw hammer. The six to ten basal bodies of a dendritic bulb have a lateral foot that serves as an organizing center for microtubules, and these microtubules (totaling about 150) extend toward the perikaryon in the basal half of the epithelium. Polarity assays indicate that the attached or minus ends of dendritic microtubules are in the dendritic bulb, with their plus or fast‐growing ends near or within the perikaryon of the neuron. It is shown that dendritic microtubules are depolymerized by direct osmium tetroxide fixation, in contrast to olfactory axonal microtubules, which persist after such fixation. F‐actin appears to be abundantly present in the dendritic bulb of the neuron, and it is possible that this actin could play a role in shape changes of the dendrite. The various findings provide new information about the olfactory dendrite, its microtubule organizing centers, and the nature and relationships of its microtubules.
Projections to the subcortical forebrain from anatomically defined regions of the medial geniculate body in the rat
Authors: LeDoux Joseph E. , Ruggiero David A. , Reis Donald. J.
Published: May 2005

Although the auditory cortex is believed to be the principal efferent target of the medial geniculate body (MG), our recent behavioral studies indicate that in rats the conditioned coupling of emotional responses to an acoustic stimulus is mediated by subcortical projections of the MG. In the present study we have therefore used WGA‐HRP as an anterograde and retrograde axonal marker to (1) define the full range of subcortical efferent projections of the MG; (2) identify the cells of origin within the MG of each projection; and (3) determine whether the subregions of the MG that project to subcortical areas receive inputs from acoustic relay nuclei of the midbrain, particularly the inferior colliculus.

The rat MG was first parcelled into three major cytoarchitectural areas: the ventral, medial, and dorsal divisions. The suprageniculate nucleus, located within the body of the MG just dorsal to the medial division, was also identified.

Efferent projections of the MG were determined by combined anterograde and retrograde tracing methods. Injections of WGA‐HRP in the MG produced anterograde transport to cortex and several subcortical areas, including the posterior caudate‐putamen and amygdala, the ventromedial nucleus of the hypothalamus, and the subparafascicular thalamic nucleus. The cells of origin of the subcortical projections were then mapped retrogradely after injections in the anterogradely labeled areas. Injections in the caudate‐putamen or amygdala retrogradely labeled the medial division of the MG and the suprageniculate nucelus, as well as several adjacent areas of the posterior thalamus surrounding the MG. In contrast, injections in the ventromedial nucleus of the hypothalamus or the subparafascicular thalamic nucleus only produced labeling in the areas surrounding MG.

Afferents to MG from the inferior colliculus were then identified. The central nucleus of the inferior colliculus, the main lemniscal acoustic relay nucleus in the midbrain, was found to project to the ventral and medial divisions of the MG. In contrast, the dorsal cortex and external nucleus of the inferior colliculus project to each division of the MG and to several additional nuclei in adjacent areas of the posterior thalamus.

These data demonstrate that the medial division of MG, the suprageniculate nucleus, and immediately adjacent areas of the posterior thalamus provide a direct linkage between auditory neurons in the inferior colliculus and subcortical areas of the forebrain and thereby support the view that thalamic sensory nuclei relay afferent signals to subcortical as well as cortical areas.
The terminations of corticospinal tract axons in the macaque monkey
Authors: Ralston Diane Daly , Ralston Henry J.
Published: May 2005

This study examined the corticospinal tract in monkey by utilizing the anterograde transport of wheat germ lectin conjugated to horseradish peroxidase (WGA HRP) at the light microscopic level and the axonal transport of 3H‐proteins with both light and electron microscopic autoradiographic techniques. The animals survived 3–9 days after the injections of 3H‐leucine or 3H‐leucine/WGA HRP into either motor or sensory cortices. With the laminar schema of Rexed as a guide to the layers of the spinal gray matter, qualitative and quantitative analyses of labeled projections of the corticospinal tract (CST) were made. With the light microscope, axons from the sensory cortex labeled with WGA‐HRP could be observed in the contralateral spinal gray from lamina I to the border of laminae VI/VII, the heaviest distribution being located in medial III–VI. There was a small ipsilateral projection to V and VI. With 3H label, laminae I and II revealed few overlying silver grains; many grains overlay laminae III–VI. Projections from the motor cortex labeled with either WGA‐HRP or 3H extended from the contralateral laminae III/IV border into the motor nucleus (lamina IX) and were seen to be somewhat more dense in the lateral areas of the spinal gray. The motor cortex projected heavily to ipsilateral VIII, and in sparse amounts to ipsilateral V and VI.

Electron microscopy of radioactive axons from the sensory cortex to dorsal horn revealed many radioactive myelinated fibers and some labeled non‐myelinated axons. Labeled terminals contacted medium to small dendrites; there were a few labeled C‐type profiles in glomeruli and occasional axo‐axonal or dendro‐axonal contacts, the labeled cortical axons being the postsynaptic structure. In ventral horn following motor cortex injections, the labeled axons were all myelinated. The synaptic contacts were found on small, medium, and large proximal dendrites as well as on cell bodies. Labeled terminals which formed the central element in glomeruli were also seen in this region. Most of the labeled corticospinal terminals in dorsal and ventral horn contained rounded vesicles, but a significant number revealed pleomorphic vesicles. The relationship of these morphological findings to physiological studies of the CST is presented.
The long visual fibers of the dragonfly optic lobe: Their cells of origin and lamina connections
Authors: Armett‐Kibel Christine , Meinertzhagen I. A.
Published: May 2005

A pair of long visual fibers projects from each ommatidium of the compound eye of the dragonfly Sympetrum. They arise from retinular cell R7 and its slender partner R6. To investigate the segregation of lamina input pathways between these and the well‐described short retinular terminals, we have examined the cell morphology and en passant synaptic involvements of R7 and 6 in the ventral lamina using serial‐EM and combined Golgi‐EM. In the retinula, R7 has a large apical rhabdomere with microvilli aligned along the animal's horizon, and a basal axon. R6 has a few microvilli at all depths, which align with those of neighboring rhabdomeres. In the lamina, R7 and 6 neighbor on MV, the fifth monopolar cell. The stout axon of R7 has many diffusely distributed spines which contact the neighboring terminals of R5 and 8, and MIL In one entire cartridge R7 was presynaptic to MII at 24 dyads and triads throughout the lamina and also to MV at dyads exclusively in the distal lamina. Another class of element which derives from the unidentified processes called a was also postsynaptic to R7 at dyads, and, mostly in the proximal lamina, was reciprocally presynaptic to R7, along with R5 and 8. R6 is slender with a single conspicuous spine. At a total of three zones in the proximal lamina and distal chiasma it was presynaptic at 38 dyads—also upon MII and MV and often in combination with other elements; it was not postsynaptic in the lamina. R6 and 7 thus provide the sole input to MV and contribute to the general retinular input to MIL They form the lowest ratios of triad:dyad synapses of all lamina retinular elements. Comparison is made with the long visual fibers of other arthropods but known examples are too diverse to detect functional commonalities.
Pituitary afferents originating in the paraventricular organ (PVO) of the goldfish hypothalamus
Authors: Fryer James N. , Boudreault‐Chateauvert Chantal , Kirby Richard P.
Published: May 2005

The diencephalon of nonmammalian vertebrates contains aminergic perikarya situated beneath the ependyma lining the third ventricle, known as the paraventricular organ (PVO). Catecholamines were visualized in the goldfish forebrain by formaldehyde‐glutaraldehyde‐induced fluorescence. Neuronal somata containing catecholamines were found in three paraventricular nuclei—the nucleus recessus posterioris (NRP), the nucleus recessus lateralis(NRL), and the nucleus posterioris paraventricularis (NPPv)—which may be considered to constitute the PVO of the goldfish. Lesion‐degeneration investigations were conducted to determine whether the PVO contributes to the innervation of the goldfish pituitary. Following electrothermic lesions of the NRP, degenerating axons and nerve terminals were observed in the rostral pars distalis and in the proximal pars distalis, but not in the neurointermediate lobe of the pituitary. Following lesions of the NRL or of the NPPv, degenerating axons and nerve terminals were observed in the rostral pars distalis, the proximal pars distalis, and in the neurointermediate lobe. These observations demonstrate that the PVO is a source of pituitary afferents in the goldfish and suggest that the PVO is a source of the catecholaminergic innervation of the teleost pituitary.
Projections from the nucleus tractus solitarii to the rostral ventrolateral medulla
Authors: Ross Christopher A. , Ruggiero David A. , Reis Donald J.
Published: May 2005

Projections from the nucleus tractus solitarii (NTS) to autonomic control regions of the ventrolateral medulla, particularly the nucleus reticularis rostroventrolateralis (RVL), which serves as a tonic vasomotor center, were analyzed in rat by anterograde, retrograde, and combined axonal transport techniques.

Autonomic portions of the NTS, including its commissural, dorsal, intermediate, interstitial, ventral, and ventrolateral subnuclei directly project to RVL as well as to other regions of the ventrolateral medulla. The projections are organized topographically. Rostrally, a small cluster of neurons in the intermediate third of NTS, the subnucleus centralis, and neurons in proximity to the solitary tract selectively innervate neurons in the retrofacial nucleus and nucleus ambiguus. Neurons generally located in more caudal and lateral sites in the NTS innervate the caudal ventrolateral medulla (CVL). The RVL, CVL, and nucleus retroambiguus are interconnected.

A combined retrograde and anterograde transport technique was developed so as to prove that projections from NTS to the ventrolateral medulla specifically innervate the region of RVL containing neurons projecting to the thoracic spinal cord or the region of the nucleus containing vagal preganglionic neurons.

When the retrograde tracer, fast blue, was injected into the thoracic spinal cord, and wheat germ agglutinin‐conjugate horseradish peroxidase (HRP) was injected into the NTS, anterogradely labeled terminals from the NTS surrounded the retrogradely labeled neurons in the RVL and in the nucleus retroambiguus in the caudal medulla. Among the bulbospinal neurons in the RVL innervated by the NTS were adrenaline‐synthesizing neurons of the C1 group.

When fast blue was applied to the cervical vagus, and HRP was injected into the NTS, anterogradely labeled terminals from the NTS surrounded retrogradely labeled neurons in the rostral dorsal motor nucleus of the vagus, the region of the nucleus ambiguus, the retrofacial nucleus, and the dorsal portion of the RVL, a region previously, shown to contain cardiac vagal preganglionic neurons. This combined anterograde and retrograde transport technique provides a useful method; for tracing disynaptic connections in the brain.

These data suggest that the RVL is part of a complex of visceral output regions in the ventrolateral medulla, all of which receive afferent projections from autonomic portions of the NTS. Bulbospinal neurons in the RVL, in particular the C1 adrenaline neurons, may provide a portion of the anatomic substrate of the baroreceptor and other visceral reflexes.
Comparison between the dimensions of dendritic spines in the cerebral cortex of newborn and adult guinea pigs
Authors: Schüz Almut
Published: May 2005

Dendritic spines in the cerebral cortex of newborn and adult guinea pigs were compared quantitatively. An increase in the average diameter of the head by 21% and in the diameter of the stalk by 29% was found. No difference could be measured in the average length of the spines of both age groups.

When plotting the individual measurements against each other, a slight correlation could be found only between the size of the spine head and the thickness of the stalk.
Location of motoneurones projecting to the cat distal forelimb. II. Median and ulnar motornuclei
Authors: Fritz Norbert , Illert Michael , Reeh Peter
Published: May 2005

The position of the motornuclei projecting through the median (Mn) and ulnar (Ul) nerves to the cat distal forelimb has been investigated. Horseradish peroxidase (HRP) and fluorescent (Fl) compounds have been used as retrograde tracers. They were either injected into forelimb muscles or applied to the proximal end of transected forelimb nerves. Limb muscles that were not investigated were carefully denervated. The position and the architecture of the individual rotornuclei were traced with HRP. The topographical relations between the nuclei were established with application of up to three different Fl compounds in the same animal. The Mn motoneurones had a bimodal distribution in the brachial spinal cord. The motoneurones to the pronator teres and flexor carpi radialis muscles were located in C7 and the other Mn motoneurones were located in C8 and Thl. In C7 the Mn motoneurones occupied a single representation area, which is located some distance medially of the lateral funiculus. In C8 and Th1 two Mn representation areas were found: A dorsal one that contacts the lateral funiculus and is located at the level of the central canal; a ventral one that is located ventrally in the ventral horn. The dorsal area is occupied by the motornuclei projecting to the intrinsic hand muscles and the ventral one by the nuclei projecting to the limb. The Ul motoneurones extend with an unimodal distribution from the caudal C7 to the caudal Thl segments. They occupy a single, broad representation area. The dorsal part, which contacts the lateral funiculus, is located at the level of the central canal and harbours the nuclei to the intrinsic hand muscles. The other Ul nuclei are located ventromedially deep in the ventral horn. These results, together with those from the companion paper on the location of the deep radial motornuclei, provide important anatomical information for the investigation of the cat brachial enlargement.
Development of connections between the mediodorsal nucleus of the thalamus and the prefrontal cortex in the rat
Authors: Van Eden C. G.
Published: May 2005

The postnatal ingrowth of thalamocortical fibers from the mediodorsal nucleus to the prefrontal cortex was investigated in relation to the development of cortical lamination. Like the dopaminergic fibers in the prefrontal cortex and the thalamic fibers in the visual cortex, the mediodorsal fibers have entered the prefrontal cortex at birth. Most of the fibers are found in the developing layer VI, but, in contrast to the above‐mentioned systems, a considerable number of mediodorsal fibers have already penetrated into the upper, most immature part of the cortical plate on postnatal day 1. From day 1 to day 7 an increasing number of mediodorsal fibers reach the upper cortical plate, which by then is developing layer 111, the terminal layer of these fibers. The reciprocal connection from the layer VI cells of the prefrontal cortex to the mediodorsal nucleus develops between day 4 and day 9. Finally, the projection from the contralateral prefrontal cortex to the mediodorsal nucleus is established around day 10. The early presence of the mediodorsal fibers in the upper, differentiating cortical plate might indicate an important role for the mediodorsal fibers in the laminar development of the prefrontal cortex.
Frontal eye field efferents in the macaque monkey: II. Topography of terminal fields in midbrain and pons
Authors: Stanton G. B. , Goldberg M. E. , Bruce C. J.
Published: May 2005

Frontal eye field (FEF) projections to the midbrain and pons were studied in nine macaque monkeys that were used to study FEF projections to the striatum and thalamus (Stanton et al.: J. Comp. Neurol. 271:473‐492, '88). Injections of tritiated amino acids or WGA‐HRP were made into FEF cortical locations where low‐level microstimulation (≤50 μA) elicited saccadic eye movements, and anterograde axonal labeling was mapped. The injections were made into the anterior bank of the arcuate sulcus from dorsomedial sites where large saccades were evoked (lFEF) to ventrolateral sites where small saccades were evoked (sFEF).

The largest terminal fields of FEF fibers were located in the ipsilateral superior colliculus (SC). Projections to SC were topographically organized: lFEF sites projected to intermediate and deep layers of caudal SC, sFEF sites projected to intermediate and superficial layers of rostral SC, and FEF sites between these extremes projected to intermediate locations in SC. Patches of terminal labeling were located ipsilaterally in the lateral mesencephalic reticular formation near the parabigeminal nucleus and the ventrolateral pontine reticular formation. These patches were larger from lFEF injections. Small, dense terminal patches were seen in the ipsilateral pontine gray, mostly along the medial and dorsal borders of these nuclei but occasionally in central and dorsolateral regions. Patches of label like those in the pontine nuclei were located ipsilaterally in the reticularis tegmenti pontis nucleus in lFEF cases and bilaterally in sFEF cases.

Small terminal patches were found in the nucleus of Darkschewitsch and dorsal and medial parts of the parvicellular red nucleus in most FEF cases. In the pretectal region, labeled terminal patches were consistently found in the nucleus limitans of the posterior thalamus, but we could not determine if label in the nucleus of the pretectal area and dorsal parts of the nucleus of the posterior commissure marked axon terminals or fibers of passage.

We found small, lightly labeled terminal patches in the pontine raphe between the rootlets of the abducens nerve (three cases) or in the adjacent paramedian pontine reticular formation (one case). Omnipauser cells in this region are important in initiating saccades. In one sFEF case, very small patches of label were located in the supragenual nuclei anterior to the abducens nuclei and in the ipsilateral nucleus prepositus hypoglossi posterior to the abducens nucleus. Presaccadic burster neurons in the periabducens region are known to fire immediately before horizontal saccades. Neither IFEF or SFEF projections appeared to terminate in the rostral interstitial nucleus of the medial longitudinal fasciculus, the interstitial nucleus of Cajal, or the motor nuclei of the extraocular muscles.
Distribution and some projections of cholinergic neurons in the brain of the common marmoset, Callithrix jacchus
Authors: Everitt Barry J. , Sirkiä Taina E. , Roberts Angela C. , Jones Graham H. , Robbins Trevor W.
Published: May 2005

The distribution of choline acetyltransferase‐immunoreactive (ChAT‐IR) neurons was studied in the brain of the common marmoset by using immunohistochemistry. ChAT‐IR neurons were found in the medial septal nucleus, vertical and horizontal limb nuclei of the diagonal band, the nucleus basalis of Meynert, pedunculopontine nucleus and laterodorsal tegmental nucleus, and also in the striatum, habenula, and brainstem cranial nerve motor nuclei. The organization of ChAT‐IR neurons in the basal forebrain, midbrain, and pons is consistent with the Ch1–Ch6 nomenclature introduced by Mesulam et al. ('83). The combination of the retrograde transport of HRP‐WGA with ChAT immunohistochemistry revealed the distribution of neurons in the Ch4 cell group projecting to the dorsolateral prefrontal cortex. The activity of ChAT was highest in limbic cortical structures, such as the hippocampus, and lowest in association areas of the neocortex. Lesions at various loci in the basal forebrain resulted in differential patterns of ChAT loss in the cortex, which suggests some degree of topographical organization of Ch4 projections to the cortical mantle.
Neural control of leg movements in a metamorphic insect: Sensory and motor elements of the larval thoracic legs in Manduca sexta
Authors: Kent Karla S. , Levine Richard B.
Published: May 2005

During the metamorphosis of the hawkmoth Manduca sexta the larval thoracic legs degenerate to be replaced in the adult by legs of very different form and function. This change must be accompanied by a reorganization of the neural circuits controlling leg movements. As an initial step in the study of this reorganization we describe here the sensory and motor elements of this circuitry in the larval stage of life. Sensory neurons innervating mechanoreceptive hairs on the thoracic surface were stained individually with cobalt. Those innervating hairs on the general thoracic surface project topographically into two ventral regions of the segmental ganglia. Sensory neurons innervating leg sensilla also map topographically to the more ventral of these regions but in addition have arborizations in a midlateral region. The density of branching within this lateral “leg neuropil” is greatest for sensory neurons from sensilla on the more distal leg segments.

Leg motor neurons were identified with intracellular recording and cobalt injection techniques. Those innervating muscles controlling distal leg segments have dense dendritic arbors in the lateral “leg neuropil,” while motor neurons controlling more proximal segments and muscles of the ventral body wall have extensive arborizations in a dorsomedial region of the ganglion. In general, flexor motor neurons are excited by medial and inhibited by lateral leg sensilla, while the opposite is true of extensors. Distal segment motor neurons respond most strongly to sensory neurons from distal segments, thus suggesting some interaction within the lateral “leg neuropil.” Thus, in the larval nervous system a highly ordered array of of sensory and motor elements underlies the specific behavioral responses of the legs to tactile stimulation.
Nucleus sagulum: Projections of a lateral tegmental area to the inferior colliculus in the cat
Authors: Henkel Craig K. , Shneiderman Amiram
Published: May 2005

The nucleus sagulum, an area of the midbrain tegmentum, has been considered a component of a lateal tegmental system within the ascending auditory pathway to the thalamus. In this study, connections of the nucleus sagulum within the midbrain were investigated in adult cats. Tracing methods using anterograde and retrograde axonal transport of markers were employed. The nucleus sagulum was identified as a region of principally small neurons (261 ± 79 μm2) at the margin of the midbrain and neighboring the nuclei of the lateral lemniscus. Injections of tritiated leucine in the nucleus sagulum labeled axons that ended in dense patches within the superficial layers of the caudal portion of the dorsal cortex of the inferior colliculus on the ipsilateral side. Retrograde experiments confirmed this connection. Other axonal projections labeled in the anterograde studies included fibers ending in the dorsomedial nucleus, the superficial layers of the dorsal cortex, and the rostral nucleus of the inferior colliculus with some bilateral distribution. Outside of the inferior colliculus, sagulum injections labeled other axons ending in the ventral intercollicular tegmentum on both sides and in a dorsal and rostral region of the contralateral nucleus sagulum that appeared contiguous with the dorsal nucleus of the lateral lemniscus. The latter region included a population of larger neurons (340‐540 μm2) and had different connections with the inferior colliculus. The distribution of axonal labeling after injections in the nucleus sagulum was contrasted with the distribution of projections from several neighboring areas of the lateral tegmentum, including the dorsal nucleus of the lateral lemniscus. None of these areas exhibited connections with the superficial layers of the caudal cortex of the inferior colliculus, which was the major target in the inferior colliculus of the nucleus sagulum. Thus, the results indicated that the nucleus sagulum is distinguished from adjacent regions of the lateral tegmentum by its connectivity. Its association with midbrain auditory pathways is supported by these connections as well as ascending ones to the auditory thalamus.
Gamma‐aminobutyric acid in the medial rat nucleus accumbens: Ultrastructural localization in neurons receiving monosynaptic input from catecholaminergic afferents
Authors: Pickel Virginia M. , Towle Andrew C. , Joh Tong H. , Chan June
Published: May 2005

Neurons containing gamma‐aminobutyric acid (GABA) in the medial portion of the adult rat nucleus accumbens were characterized with respect to their ultrastructure, sites of termination, and catecholaminergic input. Antisera against GABA‐conjugates and the catecholamine‐synthesizing enzyme, tyrosine hydroxylase (TH), were localized within single sections by means of peroxidase‐antiperoxidase (PAP) and immunoautoradiographic labeling methods. Peroxidase reaction product indicating GABA‐like immunoreactivity (GABA‐LI) was seen in medium‐size (15‐20 μm) perikarya containing either round and unindented or invaginated nuclear membranes. The cells with invaginated nuclei were few in number and usually exhibited more intense peroxidase reaction product in sections collected at the same distance from the surface of the tissue. Reaction product for GABA was also detected in proximal (1.5‐3.0 μm) dendrites, axons, and terminals. Terminals with GABA‐LI formed symmetric junctions on perikarya, proximal dendrites, and dendritic spines of neurons that usually lacked detectable immunoreactivity. Many of the GABAergic terminals also were apposed directly to other unlabeled terminals and to terminals exhibiting either peroxidase labeling for GABA or immunoautoradiographic labeling for TH. Many of the unlabeled terminals associated with the GABAergic axons formed asymmetric junctions on dendritic spines.

From 138 TH‐labeled, principally dopaminergic terminals that were examined in the medial nucleus accumbens, 4% were associated with the somata of GABAergic neurons and another 14% formed symmetric junctions with proximal dendrites showing GABA‐LI. The remaining TH‐immunoreactive terminals either lacked recognizable densities or formed symmetric synapses on unlabeled dendrites and spines. A few of the unlabeled dendrites, as well as those containing GABA‐LI, received symmetric synapses from both catecholaminergic and GABAergic terminals.

We conclude that in the medial portion of the rat nucleus accumbens, GABA is localized to two morphologically distinct types of neurons, one or both of which receive monosynaptic input from catecholaminergic afferents, and that GABAergic terminals form symmetric synapses on other princi‐pally non‐GABAergic neurons. The results also support earlier physiological evidence showing that GABA may modulate the output of other GABAergic and non‐GABAergic neurons through presynaptic associations.
Visual and auditory association areas of the cat's posterior ectosylvian gyrus: Cortical afferents
Authors: Bowman E. M. , Olson C. R.
Published: May 2005

In a preceding report, we described patterns of thalamic retrograde labeling following 17 tracer deposits on the cat's posterior ectosylvian gyrus and concluded, on the basis of patterns of thalamic connectivity, that the posterior ectosylvian gyrus is composed of three major divisions: a tonotopic auditory zone located anteriorly, a belt of auditory association cortex occupying the gyral crown, and a visual belt located posteriorly. We describe here patterns of transcortical retrograde labeling obtained from tracer deposits in the three zones so defined. Our results indicate that the tonotopic auditory strip is innervated primarily by axons from low‐order auditory areas (AAF, AI, P, VP, and V), that the auditory belt receives its strongest input from nontonotopic auditory fields (AII, temporal cortex, and other parts of the auditory belt), and that projections to the visual belt derive primarily from extrastriate visual areas (ALLS, PLLS, DLS, 19, 20, and 21) and from association areas affiliated with the visual system (insular cortex, posterior cingulate gyrus, area 7p, and frontal cortex). We discuss the results in relation to previous systems for parcellating the posterior ectosylvian gyrus of the cat and consider the possibility that divisions of the feline posterior ectosylvian gyrus correspond directly to areas making up the superior temporal gyrus in primates.
Dendritic morphology and axon collaterals of corticotectal, corticopontine, and callosal neurons in layer V of primary visual cortex of the hooded rat
Authors: Hallman L. Eric , Schofield Brett R. , Lin Chia‐Sheng
Published: May 2005

Recent evidence indicates that corticotectal neurons belong to only one of the three morphological classes of pyramidal cells in layer V. The present study compares the dendritic morphology and axon collaterals of corticotectal, corticopontine, and layer V callosal neurons by using techniques based on the retrograde transport of horseradish peroxidase and fluorescent dyes as well as in vitro intracellular dye injections. Our results indicate that corticotectal and corticopontine neurons are located predominantly in the upper middle part of layer V. These neurons have medium to large somas with 5 or 6 primary basal dendrites and a single apical dendrite ascending to layer I. Approximately 60% of these cells send axon collaterals to both the superior colliculus and the pons. In contrast, callosal neurons form a heterogeneous group. In general, they have small pyramidal or ovoid cell bodies which give rise to 3 or 4 primary basal dendrites. Many cells have an apical dendrite that bifurcates and terminates in layer V or IV. We find that callosal neurons do not send an axon collateral to either the superior colliculus or the pons.

We conclude that the corticotectal and corticopontine systems are similar in their intralaminar distribution, dendritic morphology, and pattern of axon collaterals, whereas the callosal system differs in these characteristics.
Death of the subcallosal glial sling is correlated with formation of the cavum septi pellucidi
Authors: Hankin Mark H. , Schneider Bernard F. , Silver Jerry
Published: May 2005

In this study we have examined the developmental fate of a population of cells that is located beneath the rostral corpus callosum during the perinatal period. These cells form a distinct slinglike structure along the geographically defined corticoseptal boundary (CSB) and may play a role in guiding callosal axons across the midline. The sling is a transient structure present in fetal and neonatal animals but not in adults.

Here we show that the CSB cells die and that this debris is removed by macrophages. The sequence of cell degeneration in the CSB is highly stereotyped and follows a spatiotemporal pattern that is correlated with fusion of the cerebral hemispheres and subsequent growth across the midline of the callosal axons. The subcallosal location of the resorbing CSB is found in the exact place in which a fluid‐filled cavity (the cavum septi pellucidi) is transiently found during the perinatal period.

The tight temporal and spatial correlation between callosal axon decussation, degeneration of the CSB, and cavum septi formation suggests that these three phenomena may be causally related.
Organization of cortical and subcortical projections to anterior cingulate cortex in the cat
Authors: Musil S. Y. , Olson C. R.
Published: May 2005

The aim of the experiments reported here was to identify cortical and subcortical forebrain structures from which anterior cingulate cortex (CGa) receives input in the cat. Deposits of retrograde tracers were placed at nine sites spanning the anterior cingulate area and patterns of retrograde transport were analyzed.

Thalamic projections to CGa, in descending order of strength, originate in the anteromedial nucleus, lateroposterior nucleus, ventroanterior nucleus, rostral intralaminar complex, reuniens nucleus, mediodorsal nucleus, and laterodorsal nucleus. Minor and inconsistent ascending pathways arise in the paraventricular, parataenial, parafascicular, and subparafascicular thalamic nuclei. The basolateral nucleus of the amygdala, the hypothalamus, the nucleus of the diagonal band, and the claustrum are additional sources of ascending input.

Cortical projections to CGa, in descending order of strength, derive from posterior cingulate cortex, prefrontal cortex, motor cortex (areas 4 and 6), parahippocampal cortex (entorhinal, perirhinal, postsubicular, parasubicular, and subicular areas), insular cortex, somesthetic cortex (areas 5 and SIV), and visual cortex (areas 7p, 20b, AMLS, PS and EPp).

In general, the limbic, sensory, and motor afferents of CGa are weak. The dominant sources of input to CGa are other cortical areas with highorder functions. This finding calls into question the traditional characterization of cingulate cortex as a bridge between neocortical association areas and the limbic system.
Organization of cortical and subcortical projections to medial prefrontal cortex in the cat
Authors: Musil S. Y. , Olson C. R.
Published: May 2005

We have analyzed the cortical and subcortical afferent connections of the medial prefrontal cortex (MPF) in the cat with the specific aim of characterizing subregional variations of afferent connectivity. Thirteen tracer deposits were placed at restricted loci within a cortical district extending from the proreal to the subgenual gyrus. The distribution throughout the forebrain of retrogradely labeled neurons was then analyzed.

Within the thalamus, retrogradely labeled neurons were most numerous in the mediodorsal nucleus and in the ventral complex. The projection from each region exhibited continuous topography such that more medial thalamic neurons were labeled by tracer from more ventral and posterior cortical deposits. Marked retrograde labeling without any sign of topographic order occurred in a narrow medioventral sector of the lateroposterior nucleus. Several additional thalamic nuclei contained small numbers of labeled neurons. In a subset of nuclei closely affiliated with the limbic system (the parataenial, paraventricular, reuniens, and basal ventromedial nuclei), retrograde labeling occurred exclusively after deposits at extremely ventral and posterior cortical sites.

Within the amygdala, retrogradely labeled neurons occupied the anterior basomedial nucleus, the posterior basolateral nucleus, and a narrow strip of the lateral nucleus immediately adjoining the basolateral nucleus. The number of labeled neurons was greater after more ventral deposits. Very ventral deposits resulted in extensive labeling of the cortical amygdala.

Within the cerebral cortex, the distribution of labeled neurons depended on the location of the tracer deposit. Comparatively dorsal deposits produced prominent retrograde transport to the anterior and posterior cingulate areas, to the agranular insula, and to lateral prefrontal cortex. Comparatively ventral deposits gave rise to prominent labeling of the hippocampal subiculum, various parahippocampal areas, and prepiriform cortex.

On the basis of afferent connections, it is possible to divide the cat's medial prefrontal cortex into an infralimbic component, MPFil, marked by strong afferents from prepiriform cortex and the cortical amygdala, and a dorsal component, MPFd, without afferents from these structures. Further, within MPFd, it is possible to define an axis, running from ventral and posterior to dorsal and anterior levels, along which limbic afferents gradually become weaker and projections from cortical association areas gradually become stronger.
Calcitonin gene‐related peptide immunostained axons provide evidence for fine primary afferent fibers in the dorsal and dorsolateral funiculi of the rat spinal cord
Authors: McNeill D. L. , Chung K. , Carlton S. M. , Coggeshall R. E.
Published: May 2005

The hypothesis being tested in the present paper is that there are large numbers of fine primary afferent axons in the dorsal and dorsolateral funiculi of the lumbar spinal cord of the rat. The data show numerous calcitonin gene‐related peptide labeled fine myelinated and unmyelinated axons in these funiculi. Approximately 95% of the labeled axons disappear after dorsal rhizotomy. Accordingly, the hypothesis is confirmed. Thus it is becoming apparent that fine primary afferent fibers are more widely distributed in spinal white matter than had been previously recognized. Implications are that it is not possible to find areas in the spinal white matter that contain only large myelinated sensory axons and that significant numbers of fine primary afferent fibers will be lost even if lesions are restricted to the dorsal funiculus. The sizable population of fine myelinated primary afferent axons in the dorsal funiculus is emphasized. An obvious question, suggested by significant differences in average diameters of the axons in the different pathways, is whether there are differences in the types of information carried by the fine afferent fibers in their different locations in the white matter of the lumbar cord.
Light microscopic localization of putative glycinergic neurons in the larval tiger salamander retina by immunocytochemical and autoradiographical methods
Authors: Yang Chen‐Yu , Yazulla Stephen
Published: May 2005

Putative glycinergic neurons in the larval tiger salamander retina were localized by a comparative analysis of high affinity 3H‐glycine uptake and glycine‐like immunoreactivity (Gly‐IR) at the light microscopic level. Commonly labeled neurons include at least three types of amacrine cell (Type IAd, Type IAb, Type IIAd; distinquished by soma location and dendritic ramification), cell bodies in the ganglion cell layer (GCL), and rarely observed Type II (inner) bipolar cells. With the increased resolution provided by Gly‐IR, we identified a Type IAa amacrine cell, two types of Type IIAd amacrine cells, and Gly‐IR interplexiform cells. Gly‐IR axons in longitudinal sections of the optic nerve indicate the presence of Gly‐IR ganglion cells. The percentage of labeled somas in the inner nuclear layer (INL) compared to all cells in each layer was similar for the two methods: 30‐40% in INL 2 (middle layer of somas), 30–40% in INL 3 (inner layer of somas), and about 5% in the GCL. Labeled processes were found throughout the full thickness of the inner plexiform layer (IPL), but with a much denser band in the proximal half (sublamina b). The only major difference between the two methods (3H‐glycine uptake vs. Gly‐IR) was that Type I (outer) bipolar cells were labeled only by 3H‐glycine uptake; these cells were more lightly labeled with silver grains than cell bodies in either INL 2 or INL 3. Postembed labeling of 1 μm Durcupan plastic sections for Gly‐IR showed the same pattern, but with much higher resolution, as obtained with 10 μm cryostat sections. This study indicates extensive colocalization of labeling by both probes in INL 2, INL 3, the IPL, and the GCL. We conclude that Gly‐IR can serve as a valid and reliable marker for glycine‐containing neurons in this retina and suggest that glycine serves as a transmitter for several morphologically distinct types of amacrine cell, an interplexiform cell, and perhaps a small percentage of Type II bipolar cells and ganglion cells.