bluuebunny/crossref_metadata_2025 huggingface dataset:
An autoradiographic study of the rubroolivary tract in the rhesus monkey
Authors: Strominger Norman L. , Truscott Timothy C. , Miller Richard A. , Royce G. James
Published: January 2005

Autoradiographic tracing methods were employed to study the course and distribution of the rubroolivary tract following unilateral injections of tritiated leucine into the rostral red nucleus of seven rhesus monkeys. A topographic organization of projections to the ipsilateral principal nucleus of the inferior olivary complex was demonstrated. Lateral and medial portions of the rostral red nucleus projected to medial parts of the dorsal and ventral laminae of the principal inferior olive respectively; neurons in intermediate lateralities emitted fibers which terminated in lateral parts of the principal olive. Injections involving the oral end of the rostral red nucleus elicited label overlying the medial accessory olive in addition to the principal nucleus. Projections to the medial accessory olive may have arisen from the rostral end of the red nucleus and/or the immediately adjacent tegmentum. There were no projections to the dorsal accessory olive. Fibers of rubral origin also were distributed ipsilaterally to several reticular nuclei including the pedunculopontine, pontis oralis, caudalis, and gigantocellularis.
The development of the septal region in the rat. I. Neurogenesis examined with 3H‐thymidine autoradiography
Authors: Bayer Shirley A.
Published: January 2005

Neurogenesis in the rat septal region was examined with3H‐thymidine autoradiography. The rats in the prenatal groups were the offspring of pregnant females given two injections of 3H‐thymidine on consecutive days in an overlapping series: embryonic day (E) 13 + E14, E14 + E15, … E21 + E22. The rats in the postnatal groups were injected in a nonoverlapping series: the day of birth and postnatal day (P) 1, P2 + P3, P3 + P4. On 60 days of age, the percentage of labelled cells and the proportion of cells added during each day of formation were determined at several anatomical levels within the midline nuclear group (nucleus of the diagonal band, medial and triangular septal nuclei), the lateral septal nucleus, and the ventrolateral nuclear group (nucleus accumbens, bed nuclei of the stria terminalis and the anterior commissure). The neurons within each nuclear group form in significantly different waves, those of the midline group forming between E13‐E17, the lateral septal nucleus between E15‐E19, the bed nuclei of the stria terminalis and anterior commissure between E14‐E18, the nucleus accumbens between E17‐P2. All nuclei and nuclear groups show characteristic gradients of formation. Both the midline nuclear group and the bed nucleus of the stria terminalis (including the commissural bed nucleus) have their earliest forming neurons lying near the crossing of the anterior commissure; younger neurons are located both rostrally and caudally with the youngest neurons lying in the most rostral extension of the diagonal band nucleus and the strial bed nucleus. The lateral septal nucleus forms along a strong mediolateral gradient throughout its length after neurogenesis is almost complete in the midline nuclear group. Throughout the length of the nucleus accumbens, the oldest neurons are located ventrally while progressively younger cells are found dorsally beneath the inferior horn of the lateral ventricle.
Vibrissae representation in subcortical trigeminal centers of the neonatal rat
Authors: Belford Gary R. , Killackey Herbert P.
Published: January 2005

In the neonatal rat differential activity levels of the metabolic enzyme succinic dehydrogenase (SDH) reveal intricately detailed segmentation in the neuropil of the spinal and principal trigeminal nuclei of the brainstem and in the ventrobasal complex of the thalamus. The segmentation occurs in the portions of these nuclei that electrophysiological evidence has indicated to be related to the mystacial vibrissae and sinus hairs on the face of the rat. Indeed, the pattern of segmentation in each nucleus replicates the topographic distribution of the vibrissae and sinus hairs. Further, within the spinal trigeminal nucleus, there appear to be two distinct representations of the vibrissae, one in the subnucleus caudalis and a second in the subnucleus interpolaris. Examination of these patterns of segmentation indicates that the large mystacial vibrissae and sinus hairs on the face of the young rat are somatotopically represented three times within the trigeminal complex, as straight cylinders of neuropil, and once in the ventrobasal complex, as curved cylinders of neuropil.

Neonatal vibrissae damage leads to an aberrant organization of the segmentation in the spinal trigeminal nucleus and the ventrobasal complex. In the spinal trigeminal nucleus, the SDH activity in areas associated with damaged vibrissae is of a lower than normal density, and patterns are indistinct. However, rows of clusters associated with the adjacent normal vibrissae are apparent and appear to be enlarged. In the ventrobasal complex, vibrissae damage results in bands of normal density SDH activity where rows of segmented clusters would normally be present. Comparison of these data to the cortical data in the previous paper (Killackey and Belford, '79) indicates that cortical and nuclear structures can have aspects of their development controlled by similar mechanisms.
Ascending projections to the inferior colliculus
Authors: Adams Joe C.
Published: January 2005

Cells that send ascending projections to the inferior colliculus were identified following injections of horseradish peroxidase into the colliculus. Labelled cells were found in all subcollicular auditory nuclei. Virtually all cells of the ipsilateral ventral nucleus of the lateral lemniscus and medial superior olive appear to project to the colliculus. Very few cells in these nuclei were labelled on the contralateral side. Heavy labelling on the contralateral side was found in the dorsal nucleus of the lateral lemniscus and cochlear nucleus, with less labelling being found ipsilaterally in these nuclei. The lateral superior olive was approximately evenly labelled on the two sides, with about half the cells from each side projecting to each colliculus. Cells in all periolivary cell groups were labelled, with most being found adjecent to the medial superior olive. An effort was made to identify individual cell types that were labelled and some 24 cell types were identified. In the cochlear nucleus there were marked differences between cell types in the extent of their labelling. Topographic projections matched previously described tonotopic organization of the colliculus and all major subcollicular nuclei except the ventral nucleus of the lateral lemniscus. A description of the cells in the nucleus is provided.
The parasagittal zonation within the olivocerebellar projection. II. Climbing fiber distribution in the intermediate and hemispheric parts of cat cerebellum
Authors: Groenewegen H. J. , Voogd J. , Freedman S. L.
Published: January 2005

Olivocerebellar fibers from different subnuclei of the rostral inferior olive decussate in the brain stem and terminate as climbing fibers in one or two narrow, longitudinally arranged zones of the cerebellar cortex. These fibers issue collaterals to the central cerebellar nucleus that receives its afferents from the same cortical zone in which the parent fibers terminate. The rostral medial accessory olive projects to zone C2 and sends collaterals to the posterior interposed nucleus. A differentiation can be made between the rostral pole of this subnucleus which projects primarily to the paraflocculus and the ansiform lobule. More caudal areas connect with zone C2 in the anterior lobe and the paramedian lobule. The dorsomedial cell column projects to a lateral zone (zone A2) of lobule IX and more rostrolateral portions of the medial accessory olive supply a still more lateral zone of this lobule. The rostral half of the dorsal accessory olive sends fibers to zones C1 and C3. These fibers issue collaterals to the anterior interposed nucleus. A distinction can be made between the ventrolateral dorsal accessory olive, projecting to lobules II‐IV and the ventral folia of the paramedian lobule and the dorsomedial portion of the rostral dorsal accessory olive that connects with lobules V, VI and the dorsal folia of the paramedian lobule. The most rostral part of the dorsal accessory olive provides more fibers into zone C3, more caudally located cells distribute primarily to zone C1. The rostral principal olive is connected with zone D and collateral terminations are found in the lateral cerebellar nucleus. In the paraflocculus the D zone can be divided into subzones D1 and D2. This study further substantiates the similarity in the organization of corticonuclear and olivocerebellar connections. The results are in general agreement with other recent investigations on the olivocerebellar system (Armstrong et al., '74; Brodal et al., '75; Brodal, '76; Hoddevik et al., '76; Brodal and Walberg, '77a,b; Oscarsson, '73, '76; Oscarsson and Sjölund, '77a,b).
Influences of thyroxine on cell proliferation in the retina of the clawed frog at different ages
Authors: Beach D. H. , Jacobson Marcus
Published: January 2005

The change in spatial pattern of retinal cell production that occurs after midlarvae stages in Xenopus is shown to occur because of a greater proliferative response to thyroxine in the ventral than in the dorsal margin of the retina. The asymmetry of retinal cell production is not caused by a dorsoventral difference in the duration of the mitotic cycle. It is concluded that the asymmetry is due to differences in the number of proliferative cells in different parts of the retinal margin.
An autoradiographic study of the efferent connections of the lateral hypothalamic area in the rat
Authors: Saper C. B. , Swanson L. W. , Cowan W. M.
Published: January 2005

The efferent connections of the lateral hypothalamic area (LHA) have been analyzed in a series of 30 rat brains with injections of 3H‐amino acids into different parts of the area and the surrounding regions. Our findings indicate that all parts of the LHA contribute ascending and descending fibers to the medial forebrain bundle, and also project medially to certain of the adjoining hypothalamic nuclei. All levels of the LHA appear to send some fibers to a continuous group of structures that extends from the medial septal‐diagonal band complex rostrally, through the lateral preoptic and lateral hypothalamic areas to the mammillary complex and the ventral tegmental area caudally. In addition, it is evident that cells at different levels within the LHA may have differential projections. Thus, the anterior and lateral parts of the LHA also appear to project substantially to the anterior hypothalamic area, the ventromedial and dorsomedial hypothalamic nuclei, the parataenial and paraventricular nuclei of the thalamus, and the medial part of the lateral habenular nucleus. Similarly, cells in the tuberal and posterior parts of the LHA project to the central gray, the longest projections from the posterior region reaching as far caudally as the central tegmental field, the parabrachial nucleus, the locus coeruleus, and the superior central and dorsal nuclei of the raphe. Viewed as a whole, the LHA is therefore well‐suited to integrate inputs from the limbic system and brainstem and to relay them on the one hand to the medial zone of the hypothalamus and on the other to virtually every structure closely associated with the medical forebrain bundle and to the nuclei of origin of the major ascending monoaminergic systems.
Anomalous ipsilateral retinotectal projections in syrian hamsters with early lesions: Topography and functional capacity
Authors: Finlay Barbara L. , Wilson Karen G. , Schneider Gerald E.
Published: January 2005

Retinotectal topography, response properties of neurons in superior colliculus, and visual orienting behavior were studied in hamsters whose superior colliculi were innervated by one or the other of two types of anomalous ipsilateral projections.

For the first type, an abnormally large uncrossed projection was created by monocular enucleation on the day of birth. This projection extended over the superficial part of the rostral half of the colliculus. The upper visual field was represented medially, and the lower visual field laterally, which corresponds to a normal projection. The rostrocaudal axis was disordered, but showed a slight tendency for nasal visual field to be represented rostrally and temporal field caudally; this tendency corresponds to an inversion of the normal ipsilateral projection, fitting instead the pattern of a contralateral projection.

For the second type of anomalous ipsilateral projection, an abnormal intertectal decussation of optic tract fibers was created by neonatal ablation of the superficial layers of one superior colliculus and removal of the ipsilateral eye (Schneider, '73). Retinotectal topography observed in this recrossing projection was predominantly mirror‐symmetric to the normal contralateral projection; however, some distortions in retinotopic order were observed, including misplaced fields and local inversions of the mirror‐symmetric topography, and distortions of local magnification factor. Response properties of single units found medially in the left colliculus were similar to those found in normal colliculus. Units found more laterally were underresponsive, showing response decrements with repeated stimulation which is abnormal for units in the superficial gray, and many had abnormally large receptive fields. This physiological pattern was reflected in the pattern of errors made in visual orienting to small targets.

It was concluded that polarity cues exist in the tectum sufficient to order the terminals of the retinotectal projection independent of the direction of fiber arrival or order in the optic tract as it enters the tectum. In addition, the functional competence of the abnormal recrossing retinotectal projection has been demonstrated by both electrophysiological and behavioral methods.
Correlation of variability in structure with variability in synaptic connections of an identified interneuron in locusts
Authors: Pearson Keir G. , Goodman Corey S.
Published: January 2005

Numerous reports have described variability in the morphology of identified neurons; none, however, has previously reported variability in the pattern of synaptic connection. In this report we describe variability in the synaptic connections of an identified interneuron in two species of locust (Locusta migratoria and Schistocerca gregaria) and show that this variability is associated with a large variation in the structure of the interneuron.

The morphology of the descending contralateral movement detector (DCMD) interneuron was determined in the thoracic ganglia by intracellularly staining with cobalt sulphide followed by Timm's silver‐intensification of whole‐mount preparations. The striking characteristic of the structure of this interneuron was the variability from animal to animal. This was so large we were unable to describe a “normal” structure. However, five distinct branches of the interneuron were identified in the metathoracic ganglion. In each animal the structure of DCMD could be described by specifying which of these branches were present. One or more of these branches were usually absent, and there were differences in the probability of any particular branch being absent.

Corresponding to the variation in the structure of DCMD there was a large variation in the synaptic connections made by this interneuron. DCMD can make monosynaptic connections to the fast extensor tibiae (FETi) motoneuron, fast and intermediate flexor tibiae motoneurons, and depressor and elevator flight motoneurons. These functional connections were not found in all animals. The absence of an EPSP from DCMD in FETi was associated with either the complete absence of a ventral branch or with the absence of an identifiable process of a ventral branch, and the absence of an EPSP from DCMD in flight motoneurons was associated with the absence of the dorsal branch. The connection of each of these specific branches of DCMD to FETi and flight motoneurons respectively was confirmed by double staining the motoneurons and DCMD in cases which had the functional connection. The implication of our findings is that the connections of interneurons in invertebrates may, in some cases, be far more variable than is generally believed at the present time.
The brainstem projection of the vestibular nerve in the cat
Authors: Korte Gary E.
Published: January 2005

The projection of the vestibular nerve to the brainstem of the cat was re‐examined with silver degeneration methods after complete lesions of the vestibular ganglion. Whereas previous investigations emphasize that only parts of the major vestibular nuclei are innervated by the vestibular nerve, the present investigation shows that only the dorsal division of the lateral vestibular nucleus is uninnervated. Thus, the terminal field of the vestibular nerve extends to the cytoarchitectonic boundaries of the superior, medial, descending, and the ventral division of the lateral vestibular nuclei. Vestibular nerve fibers were also traced to discrete terminal fields in the reticular formation lateral to the abducens nucleus and in the rostral, lateral parts of the accessory cuneate nucleus. These observations indicate a more widespread distribution of vestibular nerve fibers in the brainstem of the cat than previously believed.
Remodelling of optic nerve myelin sheaths and axons during metamorphosis in Xenopus laevis
Authors: Cullen Michael J. , Def. Webster Henry
Published: January 2005

Whole mounts and transverse sections of Xenopus optic nerves were examined with the light and electron microscopes before, during, and after metamorphosis. In stage 52‐58 tadpoles, almost all myelin sheaths were circular in transverse sections. Early in metamorphosis (stages 60‐61) large redundant myelin loops surrounded many large axons in central regions of the nerve. The loops subsequently were broken down into ovoids and lamellar segments that remained mostly within oligodendrocytes. These myelin changes were not observed in the chiasm or next to the eye. They were not associated with significant axonal degeneration and were no longer apparent in optic nerves of young frogs. Xenopus optic nerves also became shorter during metalmorphosis. We therefore suggest that myelin sheaths with redundant loops which degenerate and disappear are being remodelled as the nerve decreases in length.
Effects of early vibrissae damage on neurons in the ventrobasal (VB) thalamus of the mouse
Authors: Woolsey Thomas A. , Anderson James R. , Wann Janice R. , Stanfield Brent B.
Published: January 2005

We have examined the effects of vibrissal damage on the structure of the VB of the murine thalamus. The findings are: (1) The barreloid (Van der Loos, '76) pattern can be recognized in the normal adult mouse thalamus. On the basis of size, the population of VB neurons in bimodal, the larger neurons–presumed to be thalamocortical relay cells (TCR's)–outnumbering the smaller neurons–presumed to be thalamic interneurons–by 3:1. (2) Damage to vibrissa Row‐C on PND‐1 (postnatal day‐1) results in an altered cytoarchitectonic pattern in the barreloids in the contralateral VB, which is qualitatively similar to the altered pattern of barrels in the cortex. The middle row of large barreloids is affected, which is anatomical evidence for the pattern of somatotopic organization in mouse VB. (3) The time course of alterations in thalamic architecture is different than that for the barrels in the cortex. The barreloids show progressively less severe alteration with increasing age at the time the peripheral lesions are made, like the barrels in the cortex. However, the thalamus of animals lesioned on PND‐4 or later appears normal, while the cortex of animals lesioned on PND‐4 and PND‐5 still can be altered. Thus, in the thalamus, as in the cortex, there is a “critical period” during which vibrissal damage alters cytoarchitectonic patterns, but the thalamic “critical period” ends about two days before that in the cortex. (4) Measurements of TCR's in the barreloids did not reveal any statistically significant size differences between neurons in different sectors of the experimental thalami. In particular, we could find no evidence for increases of TCR size in barreloids bordering affected Row‐C barreloid zones or for reductions in TCR size in barreloids in the C‐zones. (5) In Timm's stained normal material there is a parallel development of Timm's positive staining in the thalamus and in the cortex. Barreloid related Timm's positive staining appears by PND‐4, while Timm's staining in the cortical barrel hollows appears later by PND‐8. Of particular interest is the difference in the appearance of the barrels with the Timm's stain in the PND‐8 animals and in adults. In the former, the barrel hollows are filled with granular precipitate, while in the latter they are practically devoid of Timm's precipitate, suggesting a major changeover in the staining pattern (and possibly the functional attributes) of the terminal fields of the thalamocortical afferents in postnatal development.
Electron microscopic studies of serially sectioned cat spinal α‐motoneurons. IV. Motoneurons innervating slow‐twitch (type s) units of the soleus muscle
Authors: Conradi S. , Kellerth J‐O. , Berthold C‐H. , Hammarberg C.
Published: January 2005

Two intracellularly stained cat α‐motoneurons of the soleus‐S type (Burke et al., '74) were studied ultrastructurally. The architecture and synaptology of the cell body and proximal parts of the dendrites were analyzed from a long series of sonsecutive sections (Conradi et al., '79). Only few of the dendrites had a base diameter exceeding 10 μm. The proportion of the membrane surface of the cell body and dendrites covered by boutons was 40‐45% and 50‐80%, respectively. Out of this, 15‐20% was constituted by S‐boutons and 70‐75% by F‐boutons in both regions. In contrast to the situation in the gastrocnemius FR‐neurons (Kellerth et al., '79) the large boutons of the C‐type showed no clustering around the dendritic roots and were absent on the axon hillock. In addition, the M‐boutons of dorsal root origin were more sparse on the proximal parts on the dendrites of the soleus‐S neurons.
The developmental morphology of Torpedo marmorata: Electric organ—electrogenic phase
Authors: Fox Geoffrey Q. , Richardson Guy P.
Published: January 2005

The electrogenic developmental phase of the electric organ of Torpedo marmorata begins at 40 mm of embryo length and is characterized by a horizontal flattening of the vertically orientated myotubes. The first sign of this process is a rounding up of the ventral poles of the myotubes and a disassembly of the myofibrils located therein. Occurring concomitantly with this is a migration of the nuclei to the cell center which results in a horizontal plane of nuclei. Filament bundles are then found within the ventral cytoplasm often projecting upwards from the ventral plasma membrane. The filaments of the bundles are dimensionally similar to the myofilaments of muscle and it is suggested that the bundles play a role in cellular transformation.

In contrast the dorsal pole of the cell appears to be integrated “passively” with the final cell shape as no morphological correlates of a retraction process have been found. A canalicular system, composed of a complex network of irregular tubules and vacuoles, appears just below the dorsal plasma membrane characterizing this region of the cell. A mononucleated satellite cell population lies in close proximity to the dorsal surface of the differentiating cell and fusion between the two cell types occurs throughout development.

Cell shape transformation is complete by 55 mm of embryo length and the intercolumnar nerves begin to invade the interelectrocyte space. The ingrowing neurites preferentially course along the ventral electrocyte surface establishing junctions similar to motor endplates.
Functional organization of rat olfactory bulb analysed by the 2‐deoxyglucose method
Authors: Stewart William B. , Kauer John S. , Shepherd Gordon M.
Published: January 2005

The spatial patterns of activity elicited in the rat olfactory bulb under different odor conditions have been analysed using the 2‐deoxyglucose (2DG) technique. Rats were injected with 14C‐2DG, exposed to controlled environments of amyl acetate, camphor, cage air, dimethyl disulfide, and pure air and autoradiographs prepared by the method of Sokoloff. Amyl acetate was associated with regions of glomerular layer densities in the anterolateral and mid‐ to posteromedial parts of the bulbar circumference, as previously reported. The extents of the densities increased with increasing concentration. Camphor odor was associated with regions of increased density in the anterodorsal and mid‐ to posteromedial parts of the bulb. Exposure to cage air produced scattered densities in the posteromedial and posterolateral bulb. Exposure to dimethyl disulfide gave variable results. Pure air was associated with a minimal number of small dense foci.

The results with amyl acetate, camphor and cage air suggest that patterns for different odors are distinguishably different but overlapping. The regions of activity are greatest in extent and density with the highest odor concentrations. These define the regions within which more restricted and isolated foci appear at lower concentrations. The results thus provide evidence for the specific role of spatial factors in the neural processing of odor quality and odor concentration.
Localization of vagal cardioinhibitory preganglionic neurons within rat brain stem
Authors: Nosaka Shoichiro , Yamamoto Tetsuro , Yasunaga Koheisho
Published: January 2005

In chloralose‐urethane anesthetized spinal rats, electrical stimulation of systematically chosen points over the entire caudal brain stem area was carried out to explore the site(s) responsible for vagally mediated bradycardia. A dorsomedial locus including the nucleus dorsalis and the adjacent structures, the nucleus tractus solitarius, the nucleus commissuralis and the area postrema, and a ventrolateral locus around the nucleus ambiguus were found to elicit bradycardia with low threshold and high responsiveness. In another series of experiments, horseradish peroxidase (HRP) was iontophoretically administered through a glass capillary microelectrode into the identified cardiac branch of the vagus nerve of rats in order to localize more precisely the cells of origin of vagal cardioinhibitory fibers within the brain stem. Distribution of the HRP‐labeled cells was not confined to one area, but these cells were found within the nucleus dorsalis, the reticular formation surrounding the nucleus ambiguus and an intermediary zone between the two nuclei. Such a pattern of distribution of vagal cardioinhibitory preganglionic cells is discussed in relation to phylogenetic and ontogenetic development of the vagal motor nuclei.
Spinal termination of functionally identified primary afferent neurons with slowly conducting myelinated fibers
Authors: Light A. R. , Perl E. R.
Published: January 2005

Single primary afferent myelinated fibers from cutaneous receptors of cat and monkey were functionally identified by recording from the spinal cord with micropipettes filled with horseradish peroxidase (HRP). Relatively slowly conducting fibers (< 40 m/sec) from high threshold mechanoreceptors (mechanical nociceptors) and two types of low threshold mechanoreceptor (D‐hair and field) were selected for staining. Iontophoresis of the HRP and subsequent histochemical reaction stained the axons recorded from and their collaterals, including terminations, for several millimeters. The termination patterns in the two species proved essentially identical. Ipsilaterally, the mechanical nociceptor fibers terminated principally in the dorsal horn's marginal zone and in the ventral parts of the nucleus proprius (lamina V in the cat). Some of these nociceptors also had terminals in the midline just dorsal to the central canal, contralaterally in the marginal zone, and at the base of the opposite nucleus proprius. In contrast, the D‐hair primary afferent axons terminated in the dorsal part of the nucleus proprius overlapping into the innermost portion of the substantia gelatinosa. The field receptor fibers terminated predominantly in the middle part of the nucleus proprius. These results suggest that there is a highly specialized central projection of primary afferent endings which is related to sensory function and not to fiber diameter. The marginal zone and most dorsal parts of the substantia gelatinosa receive direct projections from cutaneous nociceptors but do not have direct input from cutaneous receptors transmitting activity initiated by innocuous stimulation.
Morphological features of functionally defined neurons in the marginal zone and substantia gelatinosa of the spinal dorsal horn
Authors: Light A. R. , Trevino D. L. , Perl E. R.
Published: January 2005

Functional characteristics of spinal neurons located in the marginal zone (lamina I) and substantia gelatinosa (lamina II) were compared to their structural features by intracellularly staining the source of unitary potentials with horseradish peroxidase (HRP) in unanesthetized, spinal cats. The responses of postsynaptic units to graded electrical volleys in intact dorsal roots and to physiological stimulation revealed that the peripheral excitatory input to neurons of the region is dominated by slowly conducting afferent fibers; often, the input to a given element is largely from a particular class of receptors. One type commonly seen received its principal peripheral excitation from low threshold mechanoreceptors with Aδ or C afferent fibers. Mechanoreceptive elements often exhibited a marked, prolonged habituation and many were not excited by afferent volleys. Other units were predominantly excited by nociceptors with myelinated or unmyelinated fibers, or by thermoreceptors with unmyelinated fibers. A few units (principally the thermoreceptive) showed substantial ongoing activity which was modulated by sensory stimulation, but most had little or none.

The HRP staining revealed neuronal morphology in fine detail. No relationship between neuronal configuration and physiological response was discerned. Soma location was not always linked to afferent input, although the cell bodies of nonciceptive and thermoreceptive neurons tended to be in lamina I or outer lamina II (SGo) while those of the inocuous mechanoreceptive neurons tended to be in inner lamina II (SGi). The locus of a neuron's major dendritic arborization was more closely related to the source(s) of peripheral excitation. Cells excited by nociceptors with myelinated fibers had major dendritic projections in the marginal zone. Cells excited by nociceptors or thermoreceptors with unmyelinated fibers had important dendritic branching in the SGo. Innocuous mechanoreceptive neurons had primary dendritic aranching in the SGo. Innocuous mechanoreceptive neurons had primary dendritic arborization in the SGi when the input derived from unmyelinated fibers, or in the SGi and extending into the outer nucleus proprius (lamina III) when the afferent drive came from Aδ fibers.

These findings support the concept that laminae I and II constitute a major termination region for thin primary afferent fibers, myelinated fibers from nociceptors ending principally in lamina I and unmyelinated fibers from nociceptors, thermoreceptors, and mechanoreceptors terminating predominantly in lamina II. Substantial integrative and distributive functions can be expected of such an afferent termination zone.
Primary afferent axons in the tract of Lissauer in the cat
Authors: Chung Kyungsoon , Coggeshall Richard E.
Published: January 2005

The present study is concerned with the numbers of primary afferent axons in the tract of Lissauer in the cat. The data show that approximately 27% of the axons in mid‐thoracic and lumbosacral tracts are primary afferent fibers from the segment in question and another 20% of the axons are primary afferent fibers that come from nearby segments. In addition the data show that approximately 80% of the axons in the tract are unmyelinated and that there is a slightly higher proportion of unmyelinated as opposed to myelinated primary afferents. There is also a higher proportion of primary afferents in the medial as opposed to lateral parts of the tract, but there are significant numbers of primary afferents in lateral parts of the tract. Thus it seems clear that the tract contains more primary afferent fibers than was previously believed and if these data are confirmed, the conclusions will have a bearing on considerations of the primary afferent input into the dorsal horn.
An autoradiographic study of the retinotectal projection in the golden hamster
Authors: Chalupa Leo M. , Rhoades Robert W.
Published: January 2005

Intracular injections of tritiated leucine and proline were used to examine the retinotectal projection of the golden hamster. In the contralateral superior colliculus intense and complete label was seen in the stratum zonale, stratum griseum superficiale and the upper portion of the stratum opticum, with relatively less dense label in the lower part of the opticlayer. On the ipsilateral side no label was found in the most rostral portion of the tectum. This area comprised about 10% of the rostro‐caudal extent of the colliculus, and most likely, it receives a crossed input from the temporal retina (as demonstrated in the cat by Harting and Guillery, '76). Very sparse label was observed in an anterior segment of the ipsilateral colliculus. In coronal sections it appeared as discrete clumps or patches which were confined to the stratum opticum. Within this layer there was a tendency for the clumps to be located more dorsally with increasing laterality. There was considerable variability between and within animals in the size of the clumps as well as the distance between clumps. Reconstruction of coronal sections showed that the ipsilateral label forms discontinuous ribbons which extend up to 180 microns in the rostro‐caudal dimension. No label was seen on the ipsilateral side in the remaining tectum (caudal 60%).
Afferent projections to the ventral tegmental area of Tsai and interfascicular nucleus: A horseradish peroxidase study in the rat
Authors: Phillipson O. T.
Published: January 2005

Using the retrograde transport of horseradish peroxidase (HRP), a study has been made of projections to the ventral tegmental area of Tsai (VTA) and related dopaminergic cell groups (A 10). In order to minimise the possibility of damage to fibres of passage, a technique was evolved for the microiontophoresis of HRP such that minimal current strengths and durations were applied. In addition to a sham injection, control injections were also made to the medial leminiscus, red nucleus, deep tegmental decussations, mesencephalic reticular formation and brachium conjunctivum. Following HRP injections confined to the areas of the VTA containing the dopamine cell groups, labelled neurons appeared in prefrontal cortex, dorsal bank of rhinal sulcus, nucleus accumbens, bed nucleus of stria terminalis, amygdala, diagonal band of Broca, substantia innominata, magnocellular preoptic area, medial and lateral preoptic areas, anterior, lateral and postero‐dorsal hypothalamus, lateral habenular, nucleus parafascicular nucleus of thalamus, superior colliculus, nucleus raphe dorsalis, nucleus raphe magnus and pontis, dorsal and ventral parabrachial nuclei, locus coeruleus and deep cerebellar nuclei. Regions containing catecholamine goups A 1, A 5, A 6, A 7, A 9, A 13 and the serotonin group B 7 corresponded to the topography of labeled cell groups. Injections of HRP to the interfascicular nucleus resulted in labeling predominantly confined to the medial habenular and median raphe nuclei. The results are discussed in relation to the known connections of these regions. Other regions of the brain labelled by VTA injections are assessed in relation to control injections and the limitations of the HRP technique.

A review of the organisation of some of these afferents in relation to the known cortical‐subcortical‐mesencephalic projection systems, suggests that the VTA is in a position to receive information from a massively convergent system derived ultimately from the entire archi‐, paleo‐, and neo‐cerebral cortices. In addition A 10 dopaminergic neurons are known to project to restricted regions of both pre‐frontal and entorhinal cortices, which themselves also receive massively convergent association cortico‐cortical connections. It would appear reasonable to propose that these neurons perform a correspondingly important integrative function.
The decussation of the retinothalamic pathway in the cat, with a note on the major meridians of the cat's eye
Authors: Cooper Michael Lee , Pettigrew John D.
Published: January 2005

We have studied the naso‐temporal division of the retinothalamic pathway of the cat by making large unilateral injections of horseradish peroxidase into the lateral geniculate nucleus. In confirmation of previous work, our retinal whole‐mounts show a distinct vertical decussation line separating the contralaterally projecting nasal retina from the ipsilaterally projecting temporal retina. The ipsilateral decussation line is quite sharp, while the contralateral decussation is somewhat more diffuse, with numbers of large cells extending a few degrees into the temporal retina. However, in contrast to the results of optic tract section, our material (demonstrating the thalamic component only) does not reveal any significant population of contralaterally projecting small cells across most of the temporal retina. The previous observation of approximately 200 μm of naso‐temporal overlap in the area centralis is confirmed here, and evidence is presented that this overlap may in crease at eccentricities above the horizontal meridian.

Taken together with previously published data, this demonstration of the vertical decussation line has allowed us to estimate the relative inclinations of the major meridians of the cat's eye.
Spinal projections from the mesencephalic and pontine reticular formation in the north american opossum:A study using axonal transport techniques
Authors: Martin George F. , Humbertson A. O. , Laxson L. C. , Panneton W. M. , Tschismadia I.
Published: January 2005

The results from several experimental approaches lead to the following conclusions. The nucleus cuneiformis projects to at least lumbar levels of the spinal cord. Its axons course through the ipsilateral sulcomarginal and ventral funiculi to distribute within lamina VIII and adjacent portions of lamina VII. Neurons within the nucleus reticularis pontis (RP), particularly within more medial parts of the nucleus, project through comparable routes to the same laminae. In addition, however, neurons within the lateral and dorsolateral RP relay through the lateral and dorsolateral funiculi, ipsilaterally, and the dorsolateral funiculus, contralaterally. Axons could be traced from the dorsolateral tracts to laminae IV through VII, lamina X and, in some instances, to laminae I and II. Injections of the dorsolateral pons also label the intermediolateral cell column and an area presumed to be the sacral parasympathetic nucleus. Many of the neurons which contribute to the contralateral bundle are located adjacent to the ventral nucleus of the lateral lemniscus.

The nucleus reticularis gigantocellularis projects mainly via the sulcomarginal, ventral and lateral funiculi to laminae VIII and adjacent portions of laminae VII. The nucleus reticularis gigantocellularis pars ventralis innervates the same laminae; but, in addition, projects heavily to laminae I and II, to lateral portions of laminae IV through VII, to laminae IX and X and to the intermediolateral cell column. Axons destined for laminae I and II, as well as IV through VII and X, traverse the dorsolateral funiculi as described for the cat by Basbaum et al. (1978). Neurons within the nucleus reticularis parvocellularis project to cervical levels, mainly through the ventral funiculi. In general our results show that reticulospinal projections are more complex than suggested by degeneration methods and that laminae I, II, lateral parts of laminae IV‐VII, laminae IX and X, as well as the intermediolateral cell column and sacral parasympathetic nucleus are targets of axons from specific areas.
The origin of descending pathways in the dorsolateral funiculus of the spinal cord of the cat and rat: Further studies on the anatomy of pain modulation
Authors: Basbaum Allan I. , Fields Howard L.
Published: January 2005

There is considerable evidence that the dorsolateral funiculus (DLF) of the spinal cord contains descending pathways critical for both opiate and brainstem stimulation‐produced analgesia. To obtain a comprehensive map of brainstem neurons projecting to the spinal cord via the DLF, large injections of horseradish peroxidase (HRP) were made into the lumbosacral spinal cord of cat and rat. These injections were made caudal to midthoracic lesions which spared only a single DLF or ventral quadrant (VQ); thus only those neurons whose axons descended in the spared funiculus would be labelled.

Cells with descending axons in the VQ were concentrated in the medullary nucleus raphe pallidus and obscurus, nucleus retroambiguus and in various subregions of the reticular formation including the nucleus reticularis ventralis, gigantocellularis, magnocellularis, pontis caudalis and pontis oralis. Significant numbers of neurons were also found in medial and lateral vestibular nuclei and in several presumed catecholamine‐containing neurons of the dorsolateral pons. In the rat, but not in the cat, considerable numbers of cells are present in the mesencephalic reticular formation, just lateral to the periaqueductal gray. In both species, some cells were found in the paraventricular nucleus of the hypothalamus.

Brainstem cells projecting in the DLF were concentrated in the nucleus raphe magnus and in the adjacent nucleus reticularis magnocellularis, ipsilateral to the spared funiculus. Significant numbers of cells were found in the dorsolateral pons, differing somewhat in their distribution from those projecting in the VQ. DLF‐projecting cells were also present in the ipsilateral Edinger‐Westphal nucleus and periaqueductal grey contralateral red nucleus of the midbrain and in the ipsilateral hypothalamus. Smaller projections from other sites are described.

These results are discussed in terms of the differential contribution of several brainstem neuronal groups, including the serotonergic nucleus, raphe magnus, the ventromedial reticular formation of the medulla, and various catecholamine‐containing neurons of the dorsolateral pontine tegmentum to the analgesia produced by opiates and electrical brain stimulation.
Subcortical projections of six visual cortical areas in the owl monkey, Aotus trivirgatus
Authors: Graham J. , Lin C.‐S. , Kaas J. H.
Published: January 2005

Subcortical projections of six visual cortical areas (Areas 17 and 18, the Middle Temporal, Dorsomedial and Medial Areas, and the Posterior Parietal Region) in the owl monkey, Aotus trivirgatus, were investigated with autoradiographic methods following injections of tritiated proline. No contralateral projections were demonstrated. While some brainstem structures received input from all six subdivisions of cortex, each cortical area appeared to exhibit its own unique pattern of subcortical projections. All six cortical areas were found to project to the superior and inferior divisions of the pulvinar, reticular nucleus of the thalamus, pretectum and superior colliculus. Other subcortical targets of one or more visual cortical areas were the basal ganglia, claustrum, zona incerta, one or more of the intralaminar nuclei, lateral posterior nucleus, pregeniculate nucleus, dorsal lateral geniculate nucleus, and pontine nuclei. Furthermore, details of corticofugal projections to the dorsal lateral geniculate nucleus, pretectum and superior colliculus varied with the cortical area studied. The projections to the reticular nucleus, pregeniculate nucleus, dorsal lateral geniculate nucleus, the inferior and a portion of the superior division of the pulvinar and the superior colliculus were found to be topographically organized. The targets of the subcortical projections were compared with those of the retina, as revealed by autoradiographic methods following tritiated proline injections of the eye and were found to overlap to varying extents in the superior colliculus, pretectum and dorsal lateral geniculate nucleus and to be segregated in the pregeniculate nucleus. The results substantiate the validity of previous studies in the owl monkey that suggest that the visual cortex is subdivided into several functionally distinct areas and illustrate the complexity of corticofugal influence on visual processing.
Topological analysis of the brain stem of the lungfish Lepidosiren paradoxa
Authors: Thors Frans , Nieuwenhuys Rudolf
Published: January 2005

The ventricular sulcal pattern and the cellular structure of the brain stem of the lungfish Lepidosiren paradoxa have been studied in transversely cut Nissl and Bodian stained sections. Five longitudinal sulci, the sulcus medianus inferior, the sulcus intermedius ventralis, the sulcus limitans, the sulcus intermedius dorsalis and the sulcus medianus superior could be distinguished. In the isthmus region a number of obliquely oriented sulci is present. One of these, designated here as sulcus d, continues as a longitudinal groove into the mesencephalon. In Lepidosiren most neuronal perikarya are contained within a diffuse periventricular gray. However, 24 separate cell masses could be delineated. Six of these are primary efferent nuclei, six are primary afferent centers, six nuclei are considered to be components of the reticular formation and the remaining six may be interpreted as “relay” nuclei.

The distribution of the cell masses and their relations to the ventricular sulci were studied with the aid of the graphical reconstruction procedure termed topological analysis (cf. Nieuwenhuys, 1974, and fig. 11). This analysis yielded the following results. In the rhombencephalon the gray matter is arranged in four longitudinal columns or areas which have been termed the area ventralis, area intermedioventralis, area intermediodorsalis and area dorsalis. In many places the sulcus intermedius ventralis, the sulcus limitans and the sulcus intermedius dorsalis mark the boundaries between these morphological entities. These longitudinal areas coincide largely, but not entirely, with the so‐called functional columns of Herrick and Johnston. The most obvious incongruity is that the area intermediodorsalis contains, in addition to the nucleus of the solitary tract, two non‐visceral sensory cell masses, namely the magnocellular and parvocellular vestibular nuclei. The four longitudinal zones connot be distinguished in the mesencephalon nor can the sulcus limitans be recognized here. Functionally, however, the medial part of the tegmentum mesencephali may be considered the rostral extreme of the somatic motor column, whereas the remainder of the midbrain contains a number of somatic sensory centers.