Showing papers in "The Journal of Comparative Neurology in 1984"

Somatosensory cortical map changes following digit amputation in adult monkeys

Abstract: The cortical representations ofthe hand in area 3b in adult owl monkeys were defined with use of microelectrode mapping techniques 2-8 months after surgical amputation of digit 3, or of both digits 2 and 3. Digital nerves were tied to prevent their regeneration within the amputation stump. Suc­ cessive maps were derived in several monkeys to determine the nature of changes in map organization in the same individuals over time. In all monkeys studied, the representations of adjacent digits and pal­ mar surfaces expanded topographically to occupy most or all of the cortical territories formerly representing the amputated digit(s). With the expansion of the representations of these surrounding skin surfaces (1) there were severalfold increases in their magnification and (2) roughly corresponding decreases in receptive field areas. Thus, with increases in magnification, surrounding skin surfaces were represented in correspondingly finer grain, implying that the rule relating receptive field overlap to separation in distance across the cortex (see Sur et aI., '80) was dynamically maintained as receptive fields progressively decreased in size. These studies also revealed that: (1) the discontinuities between the representations of the digits underwent significant translocations (usually by hundreds of microns) after amputation, and sharp new discontinuous boundaries formed where usually separated, expanded digital representa­ tions (e.g., of digits 1 and 4) approached each other in the reorganizing map, implying that these map discontinuities are normally dynamically main­ tained. (2) Changes in receptive field sizes with expansion of representations of surrounding skin surfaces into the deprived cortical zone had a spatial distribution and time course similar to changes in sensory acuity on the stumps of human amputees. This suggests that experience-dependent map changes result in changes in sensory capabilities. (3) The major topographic changes were limited to a cortical zone 500-700 JIm on either side of the initial boundaries of the representation of the amputated digits. More dis­ tant regions did not appear to reorganize (i.e., were not occupied by inputs from surrounding skin surfaces) even many months after amputation. (4) The representations of some skin surfaces moved in entirety to locations within the former territories of representation of amputated digits in every

Amygdalo-cortical projections in the monkey (Macaca fascicularis)

Abstract: Amygdalo-cortical projections were analyzed in the macaque monkey (Macaca fascicularis) in a series of experiments in which 3H-amino acids were injected into each of the major divisions of the amygdaloid complex and the anterogradely transported label was demonstrated autoradiographically. Projections to widespread regions of frontal, insular, temporal, and occipital cortices have been observed. The heaviest projections to frontal cortex terminated in medial and orbital regions which included areas 24, 25, and 32 on the medial surface and areas 14, 13a, and 12 on the orbital surface. Lighter projections were also seen in areas 45, 46, 6, 9, and 10. The heaviest projection to the insula terminated in the agranular insular cortex with a decreasing gradient of innervation to the more caudally placed dysgranular and granular insular areas. The projection to this region continues around the dorsal limiting sulcus to terminate in the somatosensory fields 3, 1-2, and SII. Essentially all major divisions of the temporal neocortex receive a projection from the amygdaloid complex with the most prominent projections ending in the cortex of the temporal pole (area TG) and the perirhinal cortex. The entire rostrocaudal extent of the inferotemporal cortex (areas TE and TEO) is also in receipt of an amygdaloid projection. While the rostral superior temporal gyrus (area TA) is heavily labeled in several of the experiments (with light labeling continuing into AI and adjacent auditory association regions) there was little indication of labeling in the caudal reaches of area TA. There was a surprisingly strong projection to prestriate regions of the occipital lobe and, in at least one case, clear-cut labeling in areas OB and 17. Labeling in the parietal cortex was primarily observed in the depths of the intraparietal sulcus. In all cortical fields, label was heaviest at the border between layers I and II and in some regions layers V and VI also had above background levels of silver grains.

Projections to the frontal cortex from the posterior parietal region in the rhesus monkey.

Abstract: The projections to the frontal cortex from the various subdivisions of the posterior parietal region in the rhesus monkey were studied by means of autoradiographic technique. The rostral superior parietal lobule (area PE) projects to the dorsal areas 4 and 6 on the lateral surface of the frontal lobe as well as to the supplementary motor area (MII) on its medial surface. The caudal area PE sends its connections to dorsal area 6 and MII. The projections from the medial parietal cortex (areas PEc and PGm) are similar to those of the superior parietal lobule but they tend to concentrate in the more rostral part of dorsal area 6, MII, and in the cingulate gyrus (area 24). The most caudal part of the medial parietal cortex also projects to area 8. The anteriormost part of the inferior parietal lobule (area PF) projects to the ventral area 6, including the caudal bank of the lower branch of the arcuate sulcus, to the ventral area 46 below the sulcus principalis, and to the frontal and pericentral opercular cortex. The middle inferior parietal lobule (areas PFG and PG) projects to the ventral part of area 46 and area 8, whilst the posteriormost inferior parietal lobule (caudal PG and area Opt) is connected with both dorsal and ventral area 46, dorsal area 8, as well as the anteriormost dorsal area 6, and the cingulate gyrus (area 24).

Glutamate- and GABA-containing neurons in the mouse and rat brain, as demonstrated with a new immunocytochemical technique.

Abstract: Antisera were raised against γ-aminobutyric acid (GABA) or glutamate (Glu) conjugated to bovine serum albumin with glutaraldehyde. After purification, these antisera reacted strongly with fixed GABA or Glu, but not significantly with other amino acids fixed with glutaraldehyde to brain macromolecules. The antisera were used to demonstrate the distributions of Glu-like and GABA-like immunoreactivities (Glu-LI and GABA-LI) in parts of the perfusion-fixed mouse and rat brain, including the olfactory bulb, cerebral neocortex, thalamus, basal ganglia, lower brain stem, and cerebellum. The level of GABA-LI varied widely among brain regions, thus it was very high in the globus pallidus and substantia nigra and low in the bulk of the thalamus. The GABA antisera labeled nonpyramidal neurons of the neocortex, most cells of the reticular nucleus of the thalamus, medium-sized cells of the caudatoputamen, and stellate, basket, Golgi, and Purkinje cells of the cerebellum. The distribution of GABA-LI closely matched that of the GABA-synthesizing enzyme, glutamic acid decarboxylase (GAD), as revealed in immunocytochemical studies by others. However, the GABA antisera seem to be better suited than GAD antisera for demonstrating putative GABA-ergic axons. The results suggest that GABA-LI, as displayed by the present method, is a good marker of neurons thought to use GABA as a transmitter. Glutamate-like immunoreactivity was much more evenly distributed among regions than GABA-LI, but was particularly low in globus pallidus and substantia nigra and high in the cerebral cortex. Mitral cells of the olfactory bulb, pyramidal neocortical cells, and other cells assumed to use Glu or aspartate as transmitter were stained for Glu-LI, but so also were neurons that are thought to use other transmitters, such as cells in the substantia nigra pars compacta, in the dorsal raphe nucleus, and in the brain stem motor nuclei. The Glu antisera seem to reveal the “transmitter pool” as well as the “metabolic pool” of Glu in perfusion-fixed material. This report shows that it is possible by means of immunocytochemistry to display reliably the tissue contents of GABA and Glu in material that has been fixed by perfusion with glutaraldehyde.

The cytoarchitectonic organization of the spinal cord in the rat. I. The lower thoracic and lumbosacral cord

Abstract: A laminar cytoarchitectonic scheme of the lower thoracic and lumbosacral segments of the rat spinal cord is presented in which Rexed's principles for the cat are applied. The material consists of 80-micron-thick sections stained with toluidine blue or according to van Gieson and 2-micron-thick sections stained with p-phenylenediamine or toluidine blue. The cytoarchitectonic organization of the rat spinal cord was found to be basically similar to that of the cat, although certain differences exist--for example, in the extension of the laminae. In addition to the laminar scheme, the distribution of certain cell groups, Lissauer's tract, and the pyramidal tract were investigated.

The organization of projections from the cortex, amygdala, and hypothalamus to the nucleus of the solitary tract in rat.

Abstract: Direct projections from the forebrain to the nucleus of the solitary tract (NTS) and dorsal motor nucleus of the vagus in the rat medulla were mapped in detail using both retrograde axonal transport of the fluorescent tracer True Blue and anterograde axonal transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). In the retrograde tracing studies, cell groups in the medial prefrontal cortex, lateral prefrontal cortex (primarily ventral and posterior agranular insular cortex), bed nucleus of the stria terminalis, central nucleus of the amygdala, paraventricular, arcuate, and posterolateral areas of the hypothalamus were shown to project to the NTS and in some cases also to the dorsal motor nucleus of the vagus. The prefrontal cortical areas projecting to the NTS apparently overlap to a large degree with those cortical areas receiving mediodorsal thalamic and dopaminergic input. The retrogradely labeled cortical cells were situated in deep layers of the rat prefrontal cortex. The anterograde tracing studies revealed a prominent topography in the mediolateral termination pattern of forebrain projections to the rostral part of the NTS and to the dorsal pons. The projections to the NTS were generally bilateral, except for projections from the central nucleus of the amygdala and bed nucleus of the stria terminalis which were predominantly ipsilateral. The prefrontal cortical projections to the NTS travel through the cerebral peduncle and pyramidal tract and terminate throughout the rostrocaudal extent of the NTS. Specifically, the prefrontal cortex innervates dorsal portions of the NTS (lateral part of the dorsal division of the medial solitary nucleus, dorsal part of the lateral solitary nucleus and the caudal midline region of the commissural nucleus), areas which receive relatively sparse subcortical projections. These dorsal portions of the NTS receive major primary afferent projections from the vagal and glossopharyngeal nerves. In contrast, the subcortical projections, which travel through the midbrain and pontine tegmentum, terminate most heavily in the ventral portions of the NTS, i.e., the area immediately dorsal and lateral to the dorsal motor nucleus of the vagus. Only the paraventricular hypothalamic nucleus has substantial terminals throughout the dorsal motor nucleus of the vagus. Hypothalamic cell groups innervate the area postrema and, along with the prefrontal cortex, innervate the zone subjacent to the area postrema.(ABSTRACT TRUNCATED AT 400 WORDS)

Organization of cerebral cortical afferent systems in the rat. II. Magnocellular basal nucleus

Abstract: The organization of the magnocellular basal nucleus (MBN) projection to cerebral cortex in the rat has been studied by using cytoarchitectonic, immunohistochemical, and retrograde and anterograde transport methods. The distribution of retrogradely labeled basal forebrain neurons after cortical injections of wheat germ agglutinin-horseradish peroxidase conjugate was essentially identical to that of neurons staining immunohistochemically for choline acetyltransferase. These large (20-30 micrometers perikaryon diameter) multipolar neurons were found scattered through a number of basal forebrain cell groups: medial septal nucleus, nucleus of the diagonal band of Broca, magnocellular preoptic nucleus, substantia innominata, and globus pallidus. This peculiar distribution mimics the locations of pathways by which descending cortical fibers enter the diencephalon. Each cortical area was innervated by a characteristic subset of MBN neurons, always located in close association with descending cortical fibers. In many instances anterogradely labeled descending cortical fibers appeared to ramify into diffuse terminal fields among MBN neurons which were retrogradely labeled by the same cortical injection. Double label experiments using retrograde transport of fluorescent dyes confirmed that MBN neurons innervate restricted cortical fields. Anterograde autoradiographic transport studies after injections of 3H-amino acids into MBN revealed that MBN axons reach cerebral cortex primarily via two pathways: (1) The medial pathway, arising from the medial septal nucleus, nucleus of the diagonal band, and medial substantia innominata and globus pallidus MBN neurons, curves dorsally rostral to the diagonal band nucleus, up to the genu of the corpus callosum. Most of the fibers either directly enter medial frontal cortex or turn back over the genu of the corpus callosum into the superficial medial cingulate bundle. Many of these fibers enter anterior cigulate or retrosplenial cortex, but some can be traced back to the splenium of the corpus callosum, where a few enter visual cortex but most turn ventrally and sweep into the hippocampal formation. Here they are joined by other fibers which, at the genu of the corpus callosum, remain ventrally located and run caudally through the dorsal fornix into the hippocampus. (2) The lateral pathway arises in part from medial septal, diagonal band, and magnocellular preoptic neurons whose axons sweep laterally through the substantia innominata to innervate primarily piriform, perirhinal, and endorhinal cortex. Some of these fibers may also enter the hippocampal formation from the entorhinal cortex via the ventral subiculum.(ABSTRACT TRUNCATED AT 400 WORDS)

Mapping the body representation in the SI cortex of anesthetized and awake rats

Abstract: We have used single unit recording techniques to map the representation of cutaneous and joint somatosensory modalities in the primary somatosensory (SI) cortex of both anesthetized and awake rats. The cytoarchitectonic zones within the rat SI were divided into the following main categories: (1) granular zones (GZs)--areas exhibiting koniocortical cytoarchitecture (i.e., containing dense aggregates of layer IV granule cells), (2) perigranular zones (PGZs)--narrow strips of less granular cortex surrounding the GZs, and (3) dysgranular zones (DZs)--large areas of dysgranular cortex enclosed within the SI. The narrow strip between the SI and the rostrally adjacent frontal agranular cortex was termed the "transitional zone" (TZ). Initial computer-based studies of the properties of cutaneous receptive fields (RFs) in SI showed that, although there were differences in response threshold, adaptability, frequency response, and overall RF size and shape of adjacent neurons, the size and location of the "centers" of the RFs were quite constant and were similar to those seen in multiple unit recordings. The same was true of RFs of single neurons recorded through different anesthetic states. The body representation in SI was first mapped by determining single unit and unit cluster RFs within a total of 2,170 microelectrode penetrations in barbiturate-anesthetized rats. Cutaneous RFs in the GZs were quite discrete. Thus, a single, finely detailed, continuous map of the cutaneous periphery was definable within the GZs themselves. Only the forepaw had a double representation. RFs in the PGZs were larger and more diffuse, but since they covered roughly the same skin areas as the RFs in the most closely adjacent GZs, they fit into the same body map. Neurons in the DZs were unresponsive to any sensory stimuli in the anesthetized animal. In chronically implanted, freely moving, awake animals cutaneous RFs were larger and more volatile than in the anesthetized, but the accuracy of the map was clearly preserved by the fact that the locations of the RF centers (which often must be defined quantitatively) were unchanged. The PGZs and DZs in the awake animals exhibited a multimodal convergence of cutaneous and joint movement RFs within single vertical penetrations, or even on single neurons. Directionally specific and bilateral cutaneous RFs were also observed in the DZs. It was concluded the DZs are more associational or integrative areas within the SI, but they could not be shown to comprise a distinct and separate body representation.(ABSTRACT TRUNCATED AT 400 WORDS)

Central projections of gustatory nerves in the rat

Abstract: The central distributions of gustatory and non-gustatory branches of cranial nerves V, VII, IX, and X were examined after application of horseradish peroxidase to the cut nerve. The nerves conveying gustatory information, chorda tympani (CT), greater superficial petrosal (GSP), lingual-tonsilar branch of IX (LT-IX), superior laryngeal branch of X (SL), distributed primarily to the lateral division of the nucleus of the solitary tract (NST) from its rostral pole to the obex. The CT and GSP distributions were coextensive and terminated most densely in the rostral pole of NST. The LT-IX distribution concentrated between this major CT/GSP distribution and the area postrema with a caudal extension into the interstitial nucleus of NST. This nerve also had a substantial projection, not found in other gustatory nerves, into the dorsolateral aspect of the medial NST. The SL distribution overlapped LT-IX in the caudal medulla. The lingual and inferior alveolar nerves, two oral trigeminal branches, projected to regions of NST innervated by the gustatory nerves. The cervical vagus nerve distributed primarily to the medial NST in the caudal half of the nucleus and exhibited only minimal overlap with gustatory nerve distributions. The nucleus of the solitary tract appears to have two major functional divisions--an anterior-lateral oral-gustatory half, and a posterior-medial visceral afferent half.

Cell death during differentiation of the retina in the mouse

Abstract: A reproducible pattern of cell death associated with differentiation of the retina in mice was analyzed quantitatively by microscopy. Cell death occurs primarily during the first 2 weeks after birth and is essentially complete by the end of the third week. Death of individual cells involves nuclear condensation and pyknosis (apoptosis), followed by phagocytosis of the cellular remains by adjacent cells or motile phagocytes. From birth through 4 days, an increasing incidence of cell death is observed among ventricular cells. Ganglion cell degeneration is prominent during the first 11 days, peaking on days 2-5. Many presumptive amacrine cells die within the inner plexiform and inner nuclear layers, particularly between 3 and 8 days. Among adjoining bipolar and Muller cells, degeneration reaches a peak at 8-11 days. On day 5, formation of the outer plexiform layer separates the rods into two groups. Rod nuclei situated on the inner side of that layer immediately move across it to enter the outer nuclear layer, but numerous cells die during nuclear migration. Sporadic death of rods continues during the following 2 weeks. Cell death associated with cell differentiation (histogenetic death) is considered to represent a normal developmental process. Possible mechanisms resulting in cell degeneration are discussed. It is suggested that genetically regulated cell death serves to fine-tune neuronal networks during the terminal stages of development.

Rostral ventrolateral medulla: selective projections to the thoracic autonomic cell column from the region containing C1 adrenaline neurons.

Abstract: Anterograde, retrograde, and combined axonal transport methods were used to describe the descending efferent projections of a region of rostral ventrolateral medullary reticular formation important in cardiovascular control. We have termed this region, which contains C1 adrenaline-synthesizing neurons, the nucleus reticularis rostroventrolateralis (RVL). Efferent projections from the RVL innervate all segmental levels of the thoracic intermediolateral and intermediomedial columns as shown using retrograde transport of lectin-conjugated horseradish peroxidase (HRP) or fast blue dye, and anterograde transport of either HRP or labeled amino acids. The projection is highly specific in that there are no projections to thoracic dorsal or ventral horns. This innervation corresponds to the distribution of preganglionic sympathetic neurons in the intermediolateral column. In particular, terminals surround neurons projecting to the adrenal medulla, as demonstrated by combined anterograde and retrograde transport methods at the light level. Terminals containing phenylethanolamine-N-methyl transferase (PNMT) were mapped using immunocytochemical techniques. PNMT-labeled terminals were present at all levels of thoracic intermediolateral column, in a distribution similar to that of the descending projections from the RVL. We have previously shown using double label techniques (Ross et al., '81-'83), that many of the spinal projections of the RVL originate from C1 neurons. These data support our suggestion that certain bulbospinal neurons within the RVL, in particular the C1 neurons, are crucial for tonic vasomotor control.

Cortical projections to the superior colliculus in the macaque monkey: A retrograde study using horseradish peroxidase

Abstract: The topical and laminar distribution of corticotectal cells, as well as their size and morphology, were studied in the macaque monkey with the horseradish peroxidase (HRP) technique. After HRP injections restricted primarily to the superficial layers of the colliculus, labelled cells were found in visual cortex (areas 17, 18, and 19) and both in the frontal eye field (area 8) and the adjacent part of premotor cortex (area 6). The clustering of labelled cells in visual cortex indicated that each of the anatomically and functionally distinct visual areas has its own set of collicular projections. When intermediate and deeper layers of the colliculus were injected, labelled cells were found also in posterior parietal cortex (area 7) where they were concentrated mainly on the posterior bank of the intraparietal fissure, in inferotemporal cortex (areas 20 and 21), in auditory cortex (area 22), in the somatosensory representation SII (anterior bank of sylvian fissure, area 2), in upper insular cortex (area 14), in motor cortex (area 4), in premotor cortex (area 6), and in prefrontal cortex (area 9). In the motor and premotor cortex, labelled cells formed a continuous band which appeared to stretch across finger-hand-arm-shoulder-neck representation. Similarly, the cluster of labelled cells in area 2 may correspond to the finger-hand representation of SII. The cortical regions not containing labelled cells were the somatosensory representation SI (areas 3, 1 and 2) and the infraorbital cortex. Labelled cells were restricted to layer V of all cortical areas except in the primary visual cortex, where labelled cells were found in both layer V and layer VI. The size spectrum of corticotectal cells ranged from 14.8 micron (average diameter) in area 17 to 27.8 micron in area 6, comprising cells as small as 8 micron and as large as 45 micron. Labelled cells in posterior parietal (area 7), in auditory (area 22), and in motor cortex (area 4) were small and distributed over only a narrow range of sizes. Those in premotor cortex (area 6) were often large and had a wide range in size distribution. The differences in size and morphology of corticotectal neurons suggest that they do not form a uniform class of neurons.

Occurrence of neurotensinlike immunoreactivity in subpopulations of hypothalamic, mesencephalic, and medullary catecholamine neurons.

Abstract: By using indirect immunofluorescence histochemistry combined with the elution-restaining technique, the presence of a neurotensinlike peptide in some catecholamine neurons in the rat brain has been demonstrated. At the level of the medulla oblongata neurotensinlike immunoreactivity was observed in most of the small-sized catecholamine (adrenaline) cell bodies in the dorsolateral part of the nucleus of the solitary tract and in some catecholamine (noradrenaline) cells in the medial part. Neurotensin-positive fibers were found throughout the solitary tract nucleus with increasing concentrations in the rostral direction. Very few neurotensin fibers were seen in the vagal dorsal motor nucleus, which contained a dense network of adrenaline fibers. In the ventral mesencephalon, neurotensinlike immunoreactivity was seen mainly in dopamine cell bodies in the ventral tegmental area, including midline structures, with only single examples of coexistence in the substantia nigra. The dopamine cell bodies of both the A9 and A10 cell groups were surrounded by dense to medium-dense networks of neurotensin fibers. In the hypothalamus numerous dopamine neurons in the arcuate nucleus exhibited neurotensinlike immunoreactivity. Neurotensin-positive nerve terminals, partially overlapping catecholamine (mainly dopamine) fibers, were seen in the external layer of the median eminence. The present results demonstrate coexistence of neurotensinlike immunoreactivity and catecholamines in populations of neurons in some of the central catecholamine cell groups and provide a morphological basis for interactions between the peptide and amines.

The morphology and distribution of neurons containing choline acetyltransferase in the adult rat spinal cord: An immunocytochemical study

Abstract: A monoclonal antibody to choline acetyltransferase (ChAT), the acetylcholine (ACh)-synthesizing enzyme, has been used to localize ChAT within neurons in immunocytochemical preparations of adult rat spinal cord. Morphological details of known cholinergic spinal neurons are presented in this study, and previously unidentified ChAT-containing neurons are also described. Immunoreaction product was present within cell bodies, dendrites, axons, and axon terminals, thereby allowing comprehensive descriptions of the distribution of ChAT-positive neurons and the interrelationships of their processes. In the ventral horn, ChAT-positive motoneurons were located in the medial, central, and lateral motor columns, and their dendrites formed elaborate longitudinal and transverse ChAT-positive bundles. These bundles were present throughout the rostrocaudal extent of the spinal cord. In the central gray matter, small ChAT-positive cell bodies were clustered around the central canal. Small longitudinal fascicles of immunoreactive processes were also observed in this region adjacent to the ependymal layer. The intermediate gray matter of virtually the entire spinal cord was spanned by medium to large ChAT-positive multipolar cells termed partition neurons. At autonomic spinal levels, partition neurons were intermingled with other immunoreactive cells that were identified as preganglionic sympathetic or parasympathetic neurons because of their locations and morphological characteristics. In the sympathetic system, four groups of ChAT-positive neurons were observed; the principal intermediolateral nucleus (ILp) in the lateral horn, the central autonomic cell column (CA) dorsal to the central canal, the intercalated nucleus (IC) located between ILp and CA, and the funicular intermediolateral neurons (ILf) in the white matter lateral to the ILp. The dendrites of ILp and CA neurons formed substantial longitudinal bundles within each group, as well as transverse bundles between the groups that resembled the rungs of a ladder. ChAT-positive cell bodies were also present in the dorsal horn, and those located in laminae III-V extended dendrites dorsally into a longitudinal plexus within lamina III.

Organization of the efferent projections of the nucleus accumbens to pallidal, hypothalamic, and mesencephalic structures: a tracing and immunohistochemical study in the cat.

Abstract: The efferent connections of the nucleus accumbens in the cat were studied with the aid of anterograde and retrograde tracing techniques. The description of the topography of these projections to pallidal, hypothalamic, and mesencephalic areas is preceded by a redefinition of the borders of the pallidal regions in the cat, using immunohistochemical criteria. In agreement with previous studies in rat and monkey substance-P-like and enkephalinlike immunoreactivity in the pallidum of the cat appears to be present in so-called "woolly fibers." Substance-P- and enkephalin-positive woolly fibers are differentially distributed in the internal and external segments of the globus pallidus, as traditionally defined, but are both present in the rostral part of the substantia innominata, here called the "ventral pallidum." Woolly fibers are also found in a number of other basal telencephalic structures and in the rostral part of the lateral hypothalamic area. Fibers from the medial part of the nucleus accumbens distribute to the ventral pallidum and to the just-mentioned area in the rostral part of the lateral hypothalamus, which most probably represents part of the internal segment of the globus pallidus. The medial nucleus accumbens projects in addition to the lateral septum, the bed nucleus of the stria terminalis, the medial preoptic and hypothalamic areas, the ventral tegmental area, the retrorubral nucleus, the central superior nucleus, the nucleus tegmenti pedunculopontinus, and the central gray. The lateral part of the nucleus accumbens projects to the ventral pallidum, the subcommissural part of the globus pallidus, the entopeduncular nucleus, the substantia nigra, and the retrorubral nucleus.

The location and morphology of preganglionic neurons and the distribution of visceral afferents from the rat pelvic nerve: a horseradish peroxidase study.

Abstract: Preganglionic neurons of the sacral parasympathetic nucleus (SPN) were located almost exclusively (98%) within the L6-S1 spinal cord segments. The SPN contained approximately 550 neurons of medium size (10 X 20 micron). These were mainly located in the intermediolateral gray matter and had dendrites that extended into the dorsolateral funiculus, along the lateral marginal zone of the dorsal horn, and medially into the dorsal gray commissure. Labeled dorsal root ganglion cells were almost all located (95%) in the L6 and S1 ganglia. An average of approximately 1,500 sensory neurons were found. These were small cells (17 X 25 micron) whose central processes entered Lissauer's tract from which two groups of collaterals emerged: 1) a prominent lateral pathway along the lateral margin of the dorsal horn that extended into the region of the SPN and also into the dorsal gray commissure, 2) a less prominent medial pathway extending around the dorsal margin of the dorsal horn to terminate in the dorsal gray commissure. These two collateral groups formed fiber bundles that were spaced by approximately 100 micron between centers when observed in the horizontal plane. A third afferent bundle, composed of rostrocaudally oriented fibers, was located in the sagittal plane immediately ventral to the central canal. Comparisons are made between the results in rats and the results of similar experiments performed in cats and monkeys.

Light and electron microscopic studies of the distribution of microtubule-associated protein 2 in rat brain: a difference between dendritic and axonal cytoskeletons.

Abstract: A specific antiserum was used to ascertain the distribution of microtubule-associated protein 2 (MAP2) in the rat brain at the light and electron microscope levels. Light microscopy showed MAP2 to be present only in neurons, and only in the dendrites and the perikaryon of each cell. This same polarized distribution pattern was found in the Purkinje, Golgi, basket, stellate, and granule cells of the cerebellum, and also in neurons of the hippocampus, the olfactory bulb, and the midbrain. While labelling of the dendritic arborization was extensive and intense, MAP2 density tended to decrease in the proximal dendritic trunk. Particularly in large neurons (e.g., Purkinje, Golgi, and pyramidal cells), staining was reproducibly weaker in the cell body than in the main dendrites. Dendritic contours generally appeared smooth, without any evidence of staining of dendritic spines. An electron microscope examination of the cerebellum confirmed the presence of MAP2 reactivity in neurons and its absence from axons and non-neuronal cells. MAP2 in dendrites was associated with microtubules, while MAP2 in neuronal perikarya was associated with polyribosomes. There was no evidence of specific staining in dendritic spines and in postsynaptic densities. MAP2 is a novel dendritic marker and labels part of a specific dendritic cytoskeleton, different from that in axons and non-neuronal cells.

A stereotaxic atlas of the brain of the cynomolgus monkey (Macaca fascicularis).

Abstract: Outline drawings of representative frontal sections of the Macaca fascicularis brain are presented in stereotaxic coordinates. The levels extend from the rostral tip of the neostriatum to the posterior end of the deep cerebellar nuclei. The illustrations are based on the photographs of unstained frozen sections of three formalin-fixed brains in which stainless steel needles were inserted to mark the horizontal zero and several anteroposterior positions. The sections were not stained in order to prevent shrinkage. Stereotaxic measurements were taken in situ of the highest points on the cortical surface, the position of the central and lunate sulcus, and of certain landmarks at the base of the cranium in a large number of monkeys. These data along with brain dimensions and the weight of animals are displayed in tables to indicate individual variations and to aid investigators in determining the best stereotaxic coordinates for a given structure. It is recommended that the cortical point of entry for an electrode or needle be routinely noted and be compared to the parameters in the atlas to compensate for deviations in the horizontal plane.

Prenatal and postnatal development of retinogeniculate and retinocollicular projections in the mouse

Abstract: The development of retinal projections to the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) has been studied in fetal and neonatal mice of the pigmented C57BL/6 strain, using the anterograde transport of tritiated proline and horseradish peroxidase (HRP). Retinal efferents are present contralaterally just beyond the chiasm at E14. By E16 they have grown into both dLGN and SC. Ipsilateral fibers are limited to the proximal optic tract at E16; their growth into dLGN and SC is delayed until E18-birth. During the first 2 postnatal days, an early population of ipsilateral fibers invades the dLGN. Most of these fibers grow in or around the medio-dorsal sector of the dLGN, i.e., the future binocular segment. Fibers are also present, but at lower densities, in the ventral half of the nucleus and thereafter become dispersed or are lost, without at any stage becoming dense. Some denser labeling is also present ipsilaterally in the outer rim of dLGN, just below the optic tract, and later disappears. On the third postnatal day, the ipsilateral fibers establish a deep and denser projection along the medial and dorsal borders of dLGN; this projection overlaps part of the crossed projection, which at this age extends to the whole nucleus. The segregation of each projection starts on the fourth postnatal day, when crossed fibers begin to disappear from the small region of uncrossed projection. This process goes on for another 4 days. During this period, the ipsilateral fibers withdraw from the deepest layer of dLGN, and their terminal density increases gradually; by the eighth postnatal day, both projections are already well separated. Dense crossed projections first appear near the surface of the SC at birth. Prior to this, retinal fibers course throughout neurons of the collicular plate and underneath the pia. The uncrossed fibers invade the SC between birth and P3. They are located preferentially in the anterior and medial aspect of the SC. Subsequently, there occurs a diminution in the laminar and tangential extent of these projections, simultaneously with an intensification of the ipsilateral input to several small, longitudinally oriented clusters located deep to the crossed projections.

The neuronal architecture of the inferior colliculus in the cat: defining the functional anatomy of the auditory midbrain.

Abstract: This study defines anatomical subdivisions in Golgi-impregnated material from the inferior colliculus of the cat. The findings demonstrate that the inferior colliculus consists of a mosaic of morphologically distinct parts of neuropil. Each part is also characterized by a unique set of neuronal types. Each part of the inferior colliculus can be defined as tectal or tegmental on the basis of the fundamental pattern of dendritic branching. The main subdivisions of the auditory tectum are the central nucleus, the cortex, and the paracentral nuclei. The central nucleus is distinguished by its laminated neuropil composed of neurons with disc-shaped dendritic fields oriented in parallel arrays with the lemniscal axons. In contrast, the cortex is identified by its broad layers of loosely woven neuropil, which are orthogonal to those in the central nucleus and lack neurons with disc-shaped dendritic fields. The paracentral nuclei, so called because of their scattered arrangement around the central nucleus, are the commissural, dorsomedial, rostral pole, lateral, and ventrolateral nuclei. The main subdivisions of the auditory tegmentum are the pericollicular areas, the nucleus of the brachium of the inferior colliculus, and the sagulum. The pericollicular areas are intercollicular or subcollicular and separate the tectal division from the superior colliculus, central gray, and remaining portions of the tegmentum. The afferent projections to each tectal and tegmental subdivision, as observed in silver-degeneration experiments, distinguish the parcellations based on the Golgi findings. Subdivisions containing tectal cell types receive afferents predominantly from the auditory pathways, in contrast to subdivisions with tegmental cell types, which receive inputs from a wide variety of sources. This suggests a correlation between neuronal types and the nature of their inputs. This analysis of the subdivisions of the inferior colliculus differs from previous studies, especially those relying on Nissl stains. It is likely that subdivisions distinguished by the pattern of the neuropil differ functionally, since the structural components identified in the Golgi-impregnated material are essential parts of the synaptic organization of the auditory midbrain. Future physiological studies should benefit from approaches in which the cell types serve as the focus for the analysis.

The representation of the visual field in parvicellular and magnocellular layers of the lateral geniculate nucleus in the macaque monkey.

Abstract: Two-dimensional maps of individual layers of the dorsal lateral geniculate nucleus (LGN) in the macaque monkey were constructed and used as a basis for comparing laminar size, shape, and topographic organization. Topographical data from the electrophysiological investigation of the LGN by Malpeli and Baker ('75) were displayed on maps of all six layers. As known from previous studies, there is a significant over-representation of central vision in the LGN. Unexpectedly, though, the visual representation is anisotropic over portions of most LGN layers. That is, the linear magnification factor (millimeters along the laminar surface per degree of visual field) is not equal for all directions from a given point in the visual field. Moreover, the visual representations in the parvicellular and magnocellular divisions of the LGN differ both in their emphasis on central vision and in their anisotropies. To determine the degree of individual variability, laminar maps were prepared from the LGN of seven other hemispheres. The shapes of laminar maps varied considerably between LGNs, from nearly circular to highly elliptical, but the surface area was relatively constant for each layer. Topographical organization, determined by mapping the optic disc representation on the LGN laminae and by labeling from anterograde and retrograde tracer injections in striate cortex, showed significant individual variability. Interestingly, the visual representations in the LGN and striate cortex are topologically inverted with respect to one another. This indicates that the establishment of geniculocortical connections involves a systematic crossing-over of fibers. Information on cell densities and magnification factors in striate cortex obtained from other studies was compared to the results of the present study in order to estimate ratios of cortical neurons to LGN neurons at different eccentricities. The total number of cortical neurons per LGN neuron is about 130 on average, but it extends over approximately a tenfold range, from less than 100 in the far periphery to nearly 1,000 in the fovea. The estimated number of cells in layers 4A and 4C beta per parvicellular layer neuron is smaller and extends over a slightly narrower range, from 30 to 240, whereas the number of layer 4C alpha neurons per magnocellular neuron varies more widely, from about 45 to 7,000.

A monoclonal antibody against neurofilament protein specifically labels a subpopulation of rat sensory neurones

Abstract: A monoclonal antibody (RT97) against neurofilament protein specifically and exclusively labelled n subpopulation of rat dorsal root ganglion (DRG) neurons. For seven ganglia (L4 and T13) studied quantitatively the frequency distribution histograms of the size of labelled cells could be fitted by a single normal distribution whose parameters were extremely close to those of the normally distributed large light cell population in that ganglion. On this basis and on the basis of a statistical analysis of the results it was suggested that this antibody can be used as a much needed specific label for the large light population of neurons in rat DRGs. The small dark neuron population was not labelled by this antibody. In one ganglion the subjective analysis of whether each neuron was labelled or not was directly compared with microdensitometric measurements of reaction product intensity. This analysis supported the above conclusion, and furthermore no subdivisions of the labelled population were apparent on the basis of neuronal size plotted against intensity of the reaction product. Other neuronal cell bodies strongly labelled by this antibody were found in association with small unlabelled neurones not only in DRGs, but also in the trigeminal ganglion, the vagal ganglia, and the mesencephalic V nucleus, all of which are made up of primary afferent neurones and all of which are completely or partially derived from the neural crest. Sympathetic and central nervous system neuronal cell bodies were unlabelled or occasionally very lightly labelled although immunoreactive fibers abound in the central nervous system.

The central nucleus of the inferior colliculus in the cat

Abstract: The central nucleus of the inferior colliculus in the cat is distinguished by its unique neuropil. In Golgi-impregnated material, it is composed primarily of neurons with disc-shaped dendritic fields arranged into parallel arrays, or laminae, complemented by the laminar afferent axons from the lateral lemniscus. Large, medium-large, medium, and small varieties of disc-shaped cells are distinguished on the basis of the size of the dendritic field and cell body size, dendritic diameter, and dendritic appendages. A second major class of neurons in the central nucleus are the stellate cells with dichotomously branched, spherical-shaped dendritic trees. Simple, complex, and small stellate cells can be distinguished by their size and by the complexity of the dendritic and axonal branching. Laminar afferent axons are recognized by the nests of collateral side branches and the grapelike clusters of terminal boutons – thick, thin, and intermediate-sized varieties are apparent. Other axon types include local collaterals of central nucleus neurons, some of which are distinguished by their frequent and complex collaterals. In the central nucleus, the configuration of the fibrodendritic laminae, the presence of subdivisions, and the banding of afferent axons suggest levels of organization which are superimposed on the synaptic arrangements of the individual cell and axon types. The laminar pattern, as studied in serial Golgi-impregnated sections, differs from previous reports. The central nucleus contains subdivisions which can be distinguished by their laminar pattern, different proportions of cell types, and the packing density of the cell bodies and axonal plexus. The patterns of degeneration observed in Nauta-stained material after lesions of caudal auditory pathways show that thick and fine afferent fibers form dense bands of degeneration separated by sparse, fine-fiber degeneration. The bands are thicker than individual laminae but smaller than the subdivisions. The intrinsic organization of the neurons and axons, combined with the laminar organization, subdivisions, and banding patterns, each may contribute different aspects to the processing of auditory information in the central nucleus.

Trigeminal projections to supratentorial pial and dural blood vessels in cats demonstrated by horseradish peroxidase histochemistry

Abstract: Anatomical and clinical observations suggest that supratentorial vascular structures contain afferent projections from the trigeminal ganglia. To characterize this innervation, horseradish peroxidase (HRP) and HRP conjugated to wheat germ agglutinin were applied to the pial and dural arteries and sinuses of 33 cats. HRP was restricted to the site of interest by applying it dissolved in a viscous polymer, polyvinyl alcohol (PVA), to achieve slow release and minimize diffusion. The ganglia of cranial nerves V, VII, IX, and X and the superior cervical ganglia (SCGs) were examined bilaterally for the presence of retrogradely transported protein. Horseradish peroxidase applied to the proximal middle cerebral artery was located in cell bodies occupying the portion of the ipsilateral trigeminal ganglion corresponding to the ophthalmic division and throughout both SCGs. When the tracer was applied to the right anterior or posterior superior sagittal sinus, HRP-positive cells were present as above, predominantly in the ipsilateral trigeminal ganglia corresponding to the ophthalmic division and throughout both SCG. When applied to the right middle meningeal artery, HRP was observed within neurons of ipsilateral SCG and in the ophthalmic division of trigeminal ganglia; a few enzyme-containing cells were present in ipsilateral regions corresponding to the second and third divisions. These observations support the concept that supratentorial vascular structures receive afferent nervous projections from trigeminal neurons.

Direct connections of rat visual cortex with sensory, motor, and association cortices

Abstract: Each division of rat visual cortex, areas 17, 18a, and 18b, has connections with sensory, motor, and association cortices. These corticocortical connections were sampled using anterograde autoradiographic and retrograde horseradish peroxidase labeling techniques. Area 17 is connected via reciprocal pathways with each division of visual cortex, the posterior one-third of motor area 8, association area 7, and posteroventral area 36 of temporal cortex. It also receives projections from perirhinal areas 13 and 35. Area 18a has reciprocal connections with areas 17 and 18b, a patch in posterior somatosensory area 3, and dorsal auditory area 41. Like area 17, area 18a receives afferents from and projects to the posterior one-third of motor area 8. The connections of area 18a with association cortices are extensive; these regions include parietal areas 7, 39, 40, and 14, posteroventral and dorsal area 36, and perirhinal cortex. Area 18b is connected with areas 17 and 18a, a patch in medial area 3, and dorsal area 41. There are reciprocal projections between area 18b and posterior area 8. As for association cortex, area 18b projects to frontal area 11, area 7, posteroventral and dorsal area 36, and perirhinal cortex. In addition, area 18b receives input from and projects efferents to the dorsal claustrum. Most of the interconnections among areas 17, 18a, and 18b originate from neurons in layers II, III, and V and end in terminal fields in layers I–III and V. In contrast, projections of other sensory, motor, and association cortices to visual cortex originate mainly from neurons in layer V and to a lesser extent from layer II. The reciprocal pathways from visual cortex terminate predominantly in the supragranular layers. In conclusion, these corticocortical pathways provide the basis for cortical visuosensory and visuomotor integration that may aid the rat in the coordination of visually guided behaviors.

Quantitative light and electron microscopic analysis of cytochrome oxidase‐rich zones in the striate cortex of the squirrel monkey

Abstract: Cytochrome oxidase activity was examined in the striate cortex (area 17) of squirrel monkeys at both the light and ultrastructural levels. Two prominent bands of reactivity were found in 4A and 4C with intermittent puffs of cytochrome oxidase reactivity in laminae 2 and 3. These puffs, spaced 0.5 mm apart, were in register with intermittent concentrations of activity in laminae 4B, 5, and 6. A thin band of reactivity was observed in lamina 1. The upper portion of 4C beta was less reactive than 4C alpha or the lower portion of 4C beta. Reactive neurons included stellate cells in all laminae and pyramidal cells in laminae 2 through 4B, 5, and 6. A row of large reactive pyramidal cells was observed in upper lamina 6. More reactive neurons were found in the puffs (laminae 2 and 3) than were observed in interpuff regions, and the reactive neurons were significantly larger than the nonreactive neurons. Reactive neurons contained two to three times as many reactive mitochondria as did the nonreactive neurons and often had indented nuclei. Based on the number of darkly or highly reactive, moderately reactive and lightly reactive mitochondria, puff regions were significantly different from nonpuff regions; there were approximately two times as many darkly reactive mitochondria in puff regions as compared to a similar nonpuff area. The majority of mitochondria (32% in puff; 44% in nonpuff) were found to reside in the dendritic profiles, which also contained the majority of highly reactive mitochondria. In a separate analysis, the total area of highly reactive mitochondria within puff regions was found to be twice the total area of highly reactive mitochondria in a comparable nonpuff region. An analysis of synapses showed that there were more asymmetrical synapses in both puff and nonpuff regions (55% and 54%, respectively) than symmetrical ones (45% in puff and 46% in nonpuff). There was an increase in mitochondrial reactivity in both asymmetrical and symmetrical synapses in the puff areas; however, the increased reactivity within asymmetrical terminals was significantly greater than that within symmetrical ones. Several somatodendritic synapses were observed and they were all of the symmetrical variety. Axospinous contacts were primarily of the asymmetrical type; however, symmetrical axospinous synapses were observed and were typically seen in association with an asymmetrical synapse. It was concluded that cytochrome oxidase activity is localized primarily within the dendritic profiles in both puff and nonpuff regions.(ABSTRACT TRUNCATED AT 400 WORDS)

The development of photoreceptors in the zebrafish, Brachydanio rerio. I. Structure

Abstract: Morphological development of photoreceptors in the central retina of the zebrafish, Brachydanio rerio, was studied by using light and electron microscopic techniques. Outer segments (OS) first appeared at 2.5 days postfertilization (d2.5). On d3, synaptic elaborations were seen. By d8, two OS types were present and were identified as cones. The first indication of rod formation was also evidenced at this time, when vitreally positioned nuclei were observed and rodlike cells were infrequently detected in electron micrographs. At d12, the full complement of zebrafish photoreceptors, rods and four cone types, was identified. From this time on cells grew until adult dimensions were reached at d24. These structural observations are consistent with results of functional studies which utilized physiological and behavioral techniques.

Subcortical projections of area MT in the macaque.

Abstract: Area MT is a visuotopically organized area in extrastriate cortex of primates that appears to be specialized for the analysis of visual motion. To examine the full extent and topographic organization of the subcortical projections of MT in the macaque, we injected tritiated amino acids in five cynomolgus monkeys and processed the brains for autoradiography. The injection sites, which we identified electrophysiologically, ranged from the representation of central through peripheral vision in both the upper and lower visual fields and included, collectively, most of MT. Projections from MT to the superior colliculus are topographically organized and in register with projections from striate cortex to the colliculus. Unlike projections from striate cortex, those from MT are not limited to the upper layer of the stratum griseum superficiale but rather extend ventrally from the upper through the lower layer of the stratum griseum superficiale and even include the stratum opticum. Projections from MT to the pulvinar are organized into three separate fields. One field (P1) is located primarily in the inferior pulvinar but extends into a portion of the adjacent lateral pulvinar. The second field (P2) partially surrounds the first and is located entirely in the lateral pulvinar. The third and heaviest projection field (P3) is located posteromedially in the inferior pulvinar but also includes small portions of the lateral and medial pulvinar that lie dorsal to the brachium of the superior colliculus. While projections from MT to P1 and P2 are topographically organized, there appears to be a convergence of MT inputs to P3. Projections from MT to the reticular nucleus of the thalamus are located in the ventral portion of the nucleus, approximately at the level of the caudal pulvinar. There was some evidence that MT sites representing central vision project more caudally than do those representing peripheral vision. Projections from MT to the caudate, putamen, and claustrum are localized to small, limited zones in each structure. Those to the caudate terminate within the most caudal portion of the body and the tail. Similarly, projections to the putamen are always to its most caudal portion, where the structure appears as nuclear islands. Projections to the claustrum are located ventrally, approximately at the level of the anterior part of the dorsal lateral geniculate nucleus. Projections from MT to the pons terminate rostrally in the dorsolateral nucleus, the lateral nucleus, and the dorsolateral portion of the peduncular nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Morphometry of intracellularly labeled neurons of the auditory nerve: correlations with functional properties.

Abstract: Single auditory-nerve fibers were injected with horseradish peroxidase after their tuning properties, characteristic frequencies, and spontaneous discharge rates were measured From these functional properties virtually all other aspects of auditory-nerve response can be predicted Labeled fibers were reconstructed from the point of peripheral termination on cochlear hair cells to the point at which they enter the cochlear nucleus Several morphological properties were measured at the light-microscopic level, including axonal diameter, axonal length, internodal distances, cell-body area, and cell-body shape All of these parameters were correlated, though some weakly, with characteristic frequency However, only axonal diameter was correlated with spontaneous discharge rate

Demonstration of a sexual dimorphism in the distribution of serotonin‐immunoreactive fibers in the medial preoptic nucleus of the rat

Abstract: The distribution of serotonergic fibers in the medial preoptic nucleus (MPN) and adjacent areas was evaluated with an indirect immunohistochemical method in the normal adult male and female albino rat. Sections through the MPN were processed for immunofluorescence with an anti-serum directed toward serotonin and were counterstained with the fluorescent Nissl stain ethidium bromide. The distribution of serotonin-immunoreactive fibers in the MPN was correlated with cytoarchitectonic features of the nucleus. On the basis of the results, we have subdivided the MPN into three parts: a medial cell-dense part ( MPNm ), a lateral cell-sparse part ( MPNl ), and a central very cell-dense part ( MPNc ) that is embedded in the medial part. The MPNc corresponds to the sexually dimorphic nucleus of the preoptic area identified by Gorski et al. ('80). A marked sexual dimorphism was found in the relative size of each part of the MPN. In the male, the volumes of the cell-dense MPNm and MPNc appear to be notably larger, while in the female more than half of the nucleus is occupied by the cell-sparse lateral part. The MPN as a whole appears to be slightly larger in the male. Each subdivision contains a characteristic pattern of serotonin-immunoreactive fibers. In each sex, the MPN is surrounded by a low to medium density of serotonin-stained fibers, while the MPNl is filled with a dense plexus of varicose immunoreactive fibers. In contrast, the MPNm contains a low density of stained fibers, and the MPNc is virtually devoid of serotonin-stained fibers. Since both the MPNm and the MPNc are larger in the male, a correspondingly larger region of very low serotonin-stained fiber density is found in the male. It appears then that the MPN is a sexually dimorphic complex composed of at least three cytoarchitectonically distinct subdivisions, each of which contains a characteristic density of serotonin-immunoreactive fibers.