bluuebunny/crossref_metadata_2025 huggingface dataset:
Double representation of the body surface within cytoarchitectonic area 3b and 1 in “SI” in the owl monkey (aotus trivirgatus)
Authors: Merzenich Michael M. , Kaas Jon H. , Sur Mriganka , Lin Chia‐Sheng
Published: May 2005

Microelectrode multiunit mapping studies of parietal cortex in owl monkeys indicate that the classical “primary” somatosensory region (or “SI”) including the separate architectonic fields 3a, 3b, 1, and 2 contains as many as four separate representations of the body rather than one. An analysis of receptive field locations for extensive arrays of closely placed recording sites in parietal cortex which were later related to cortical architecture led to the following conclusions: (1) There are two large systematic representations of the body surface within “SI”. Each is activated by low threshold cutaneous stimuli; one representation is coextensive with Area 3b and the other with Area 1. (2) While each of these representations contain regions of cortex with topological or “somatotopic” transformations of skin surface, the representations have many discontinuities where adjoining skin surfaces are adjoining in the representations. Thus, the representations can be considered as composites of somatotopically organized regions, but cannot be accurately depicted by simple continuous homunculi. Lines of discontinuity often cut across dermatomes and seldom follow dermatomal boundaries, i.e., neither cutaneous representation constitutes a systematic representation of dermatomal skin fields. (3) While the two cutaneous fields are basically similar in organization and are approximate mirror images of each other, they differ in important details, i.e., lines of discontinuity in the representations and the sites of representations of different specific skin surfaces differ significantly in the two representations. (4) The two cutaneous representations also differ in size and in the relative proportions in each representation differ, they cannot both be simple reflections of overall peripheral innervation density. (5) All or part of Area 2 contains a systematic representation of deep body structures.

These conclusions are consistent with a view of the anterior parietal region as containing functionally distinct fields at least partially related to different subsets of receptor populations and coding or representing different aspects of somatic sensation. We suggest that the “SI” region of primates be redefined as a parietal somatosensory strip, the Area 1 representation as the posterior cutaneous field, and, for reasons of probable homology with “SI” of other mammals, the Area 3b representation as SI proper.
Postnatal synaptogenesis in the rat interpeduncular nucleus
Authors: Lenn Nicholas J.
Published: May 2005

The rat interpeduncular nucleus (IPN) was studied by electron microscopy from the day of birth to 33 days of age. The habenulointerpeduncular (H‐IPN) axons, the principal afferents to IPN, were prominent at birth, occuring in large groups. They formed occasional S synapses en passant at this time. S synapses subsequently increased progressively in number and maturity until 28 days of age. Crest synapses, also formed by the H‐IPN axons, appeared at eight days without a recognized formative stage. They exhibited their diverse adult morphology by 14 days of age. F synapses, endings of uncertain origin that contain flattened vesicles, were seen at 21 days, although endings containing small vesicles at 14 days represented the same population. Axosomatic synapses were first seen at four days and remained infrequent subsequently. Dendritic growth cones had their maximal prevalence at birth, decreased at four days and were absent by six days of age.

Thus each of the four synaptic types previously described in the adult rat IPN exhibited a characteristic time of appearance and pattern of development in normal rat pups. This well‐ordered sequence of synaptogenesis makes the H‐IPN system well suited for a study of synaptic plasticity.
Smooth and sparsely‐spined stellate cells in the visual cortex of the rat: A study using a combined golgi‐electron microscope technique
Authors: Peters Alan , Fairén Alfonso
Published: May 2005

The visual cortex of the rat was impregnated by the rapid Golgi procedure. From these preparations, smooth (spine‐free) and sparsely‐spined multipolar stellate cells with well impregnated axons were selected and drawn in the light microscope using a camera lucida. Five suitably impregnated cells were then gold‐toned and deimpregnated by removal of the silver chromate produced by the Golgi impregnation, so that they could be examined in the electron microscope to determine both their cytological features and their pre‐ and postsynaptic relationships. A sixth neuron was not deimpregnated, and was examined in the electron microscope only to evaluate the types of synapses formed by its axons terminals. Five of these cells had extensive local axonal plexus and the sixth had a plexus which was less profuse.

In the electron microscope the various portions of the deimpregnated neurons were readily identified by their content of fine gold particles, and it was found that their perikarya possessed a rather dark cytoplasm containing many ribosomes. Both symmetric and asymmetric synapses were present on the perikarya, and some of the perikarya had spines. The dendrites of the cells had relatively smooth contours and contained rather closely packed microtubules. The dendrites also had both symmetric and asymmetric synapses along their shafts, with the symmetric synapses being more frequent on the proximal portions of the dendrites.

The axons of the neurons were unmyelinated and all of them formed symmetric synapses with their postsynaptic partners. The synapses occurred at dilatations of the axons at both en passant and terminal boutons. Neuronal elements identified as being postsynaptic to the axon terminals of the stellate cells included the perikarya and apical dendritic shafts of pyramidal neurons, the perikarya and dendritic shafts of other stellate cells, and an axons initial segment.

Reasons are given for concluding that these multipolar, smooth and sparsely‐spined stellate cells are inhibitory in function, and their relationships with some other neuronal components of the rat visual cortex are considered.
A light and electron microscopic study of the pineal in the blind goby, Typhlogobius californiensis (Pisces: Gobiidae)
Authors: McNulty John A.
Published: May 2005

The pineal of the burrow‐inhabiting, blind goby, Typhlogobius californiensis, was studied by light and electron microscopy. The two predominant cell types were photoreceptor and supportive cells. Ganglion cells could not be positively identified. The majority of photoreceptor cells had well developed outer segments and made apparent synaptic contact with nerve process of unknown origin. Similar unmyelinated nerve fibers containing dense‐cored vesicles were seen descending the pineal stalk. The cytoplasm of supportive cells contained several Golgi zones, occasional dense aggregations of smooth endoplasmic reticulum, abundant quantities of glycogen, some dense‐cored vesicles and unusual rod crystalline inclusions measuring approximately 0.5 μm in width and 4–5 μm in length. These observations suggest that the pineal in this light‐deprived species has retained its photoreceptive function and is a metabolically active organ which may also function in secretion.
Histology and ultrastructure of the carotid sinus in experimental hypertension
Authors: Rees Peter M. , Sleight Peter , Robinson James L. , Bonchek Lawrence I. , Doctor Aspi
Published: May 2005

Histological studies including electron microscopy were performed on the carotid sinuses of dogs with renal hypertension of 17 to 82 days duration or hypertension of two years secondary to aortic coarctation. Physiological abnormalities in the baroreceptors including resetting had been demonstrated before death. Histologically there were no qualitative or quantitative differences in the intrasinus nerve fibers of the hypertensive animals compared to controls with normal blood pressures, and there was no evidence that baroreceptor degeneration occurred as a consequence of the hypertension. Structural lesions confined to the intima were evident in the sinus walls of some of the renal hypertensive animals whereas the dogs with coarctation showed more advanced sinus wall changes including medial calcification and enlargement of the vascular lumen.
Observations on the development of brainstem‐spinal systems in the north american opossum
Authors: Martin G. F. , Beals J. K. , Culberson J. L. , Dom R. , Goode G. , Humbertson A. O.
Published: May 2005

The North American opossum is born 12 to 13 days after conception and is available for 90 days or more in an external pouch where it can be observed and experimentally manipulated. It is of particular interest that the hindlimbs of the newborn opossum are very immature and remain immobile for a week or more after birth.

Degeneration techniques reveal that immature brainstem axons are present within the marginal zone of the lumbosacral cord before hindlimb movements begin (our stage I) and material processed for formaldehyde induced fluorescence shows that some of them transport monoamines. Several lines of evidence suggest that part of the fluorescent axons arise within the nucleus locus coeruleus. At this early stage the electron microscope reveals that all brainstem‐spinal axons are small (0.1‐0.4 μm in diameter) and unmyelinated. By the time random hindlimb movements can be observed (stage II), brainstem axons, including those transporting monoamines, can be demonstrated to have grown into limited areas of the intermediate zone of the lumbosacral cord and to arise from most of the areas contributing to them in the adult animal (horseradish peroxidase technique). Such axons are still immature and it is not yet clear that they have formed synaptic terminals. Brainstem axons continue to grow into the intermediate zone of the lumbosacral cord for some time and come to occupy all of their adult territories before thoracic transection produces obvious change in hindlimb motility (beginning of stage III). It is still another 20 days or so before thoracic transection produces spinal shock comparable to that in the adult animal. The relatively mature use of the hindlimbs and the full expression of spinal shock correlate with changes in the technique and survival time needed to demonstrate degenerating brainstem axons in experimental material.
Nuclei of the solitary tract: Efferent projections to the lower brain stem and spinal cord of the cat
Authors: Loewy A. D. , Burton H.
Published: May 2005

The efferent projections from the solitary complex to the lower brain stem and spinal cord were studied in the cat with the autoradiographic anterograde axonal transport and retrograde horseradish peroxidase (HRP) techniques. A revised cytoarchitectonic description of the caudal two‐thirds of the complex is presented in which the complex was subdivided into six nuclei: lateral, ventrolateral, intermediate, medial, parvocellular, and commissural solitary tract nuclei. Following injections of 3H amino acids into electrophysiologically defined regions of the complex in which cardiac or respiratory units were recorded, labeled fibers could be traced to a number of sites in the caudal brain stem including the medial and lateral parabrachial nuclei, Kölliker‐Fuse nucleus and the area ventral to this nucleus, lateral periaqueductal gray matter, ambiguus complex, which consists of the retrofacial, ambiguus and retroambiguus nuclei, ventrolateral reticular nucleus (in an area equivalent to the A1 cell group of Dahlström and Fuxe, '64), medial accessory olive, paramedian reticular formation, and lateral cuneate nucleus. Descending solitario‐spinal projections have been traced bilaterally, but predominantly to the contralateral side, to the region of the phrenic motor neurons in the C4‐C6 ventral horn, to the thoracic ventral horn, and intermediolateral cell column.

Confirmatory evidence of some of these projections was obtained from a series of HRP experiments. Mainly small neurons of the parvocellular, medial and commissural solitary tract nuclei project to the region of the parabrachial and Kölliker‐Fuse nuclei. The lateral solitary nucleus projects almost exclusively to the ipsilateral medial accessory olive. It was not possible to interpret conclusively the labeling seen in the medium and large neurons of the ventrolateral solitary nucleus after HRP injections made in the region of the ambiguus‐retroambiguus complex due to the problem of fibers of passage. Following injections of HRP into the cervical, thoracic, lumbar, or sacral spinal cord, retrograde cell labeling was seen in the solitary complex. Cells in the intermediate and commissural nuclei were labeled after all four types of experiments. In the ventrolateral nucleus, medium sized neurons were predominantly labeled after the cervical spinal cord experiments, while large sized neurons were labeled mainly after the thoracic spinal cord injections. The potential physiological significance of these various connections is discussed in terms of central control of cardiovascular and respiratory functions.
Distribution of motoneurones to the neck muscles, biventer cervicis, splenius and complexus in the cat
Authors: Richmond F. J. R. , Scott D. A. , Abrahams V. C.
Published: May 2005

The distribution of motoneurones to the cat dorsal neck muscles biventer cervicis, splenius and complexus has been examined using the technique of retrograde horseradish peroxidase transport. A comparison was initially made of HRP uptake into motoneurones produced either by injecting HRP solution directly into a singly neck muscle or by exposing the cut ends of motor nerves to an HRP solution. The injection of HRP into single neck muscles was found to produce widespread labelling of motoneurones presumably due to diffusion of HRP into adjacent muscles. For the examination of individual motoneurone pools the technique of cut nerve exposure was therefore used.

Labelled neck muscle motoneurones ranged from 10–70 μ in diameter, but the majority of cells had diameters which were less than 40 μ. Most cells were located in the ventromedial nucleus and along the medial border of the ventral horn. In these regions there was considerable overlap between the motoneurones pools of the three neck muscles examined. In addition, some splenius motoneurones were located in the nucleus of the spinal accessory nerve. Labelled neck muscle motoneurones were also located in areas not usually considered to contain motoneurones such as the commissural and centrodorsal nuclei and in the ventral commissure.
Afferent and efferent fiber connections of the carp torus longitudinalis
Authors: Ito Hironobu , Kishida Reiji
Published: May 2005

The efferent and afferent pathways of the carp torus longitudinalis were studied by means of degeneration and retrograde HRP methods. Efferent projections were only seen in the most superficial layer of the ipsilateral optic tectum (stratum fibrosum marginale).

Afferent pathways to the torus longitudinalis were found to originate mainly in the valvula cerebelli. Degenerating fibers course in the tractus mesencephalocerebellaris posterior within the valvula, and join the tractus mesencephalocerebellaris anterior in the tegmentum. The fibers which ascend in the tract gradually invade the optic tectum through which they are distributed to the torus longitudinalis. The remaining fibers pass through the posterior commissure and terminate in the torus longitudinalis at the rostral end of the tract.

Degenerating terminals were also seen in the torus longitudinalis when lesions were made in the optic tectum, tectal commissure, torus semicircularis, and in the area between the valvula and the corpus cerebelli. The possibility of projection from these areas is discussed depending upon the results of the retrograde HRP method.
Effects of early monocular lid suture upon neurons in the cat's medial interlaminar nucleus
Authors: Kratz Kenneth E. , Webb Sarah V. , Murray Sherman S.
Published: May 2005

Single unit extracellular recordings, cell size measurements, and cell packing density measurements were made in the medial interlaminar nucleus (MIN) of nine adult cats that had been monocularly deprived by lid suture prior to natural eye opening. The electrophysiological properties of neurons in the nondeprived regions of MIN (areas receiving input from the nondeprived eye) remained unaffected by monocular lid suture. The latencies to optic chiasm stimulation and receptive field properties, including receptive field center size, were essentially the same as those found for MIN neurons of normal adult cats. In contrast, cells in the deprived regions were severely affected by monocular deprivation. We encountered in the deprived regions of MIN only about one half as many active neurons per mm of electrode penetration as we did in the nondeprived regions. Of the physiologically active cells remaining, about one half had abnormal receptive field and/or response properties. This resulted in a sampling density of 5.1 normal Y‐cells per mm of penetration in nondeprived regions of MIN compared to 1.0 normal Y‐cell per mm in deprived regions of MIN.

Histological effects of deprivation were also seen. Deprived regions of MIN were distinguished from nondeprived regions in four cats by autoradiography following intravitreal injection of tritiated proline into the deprived or nondeprived eye (2 cats each). The man cell size of deprived regions of MIN was 34% smaller than that of nondeprived regions. We did not find a difference in cell packing density between these two regions.

It appears that the effects of monocular lid suture upon MIN are in most respects similar to the effects of monocular lid suture previously reported for the A laminae. Since MIN is composed solely of Y‐cells, these data support the idea that the Y‐pathways are more severely affected by visual deprivation than are the X‐pathways. Further, since MIN projects largely outside the striate cortex, these data give the first clear demonstration of a primary effect of early lid suture upon extrastriate visual pathways.
Brain stem origins of spinal projections in the lizard Tupinambis nigropunctatus
Authors: Cruce William L. R. , Newman Donald B.
Published: May 2005

In order to study brainstem origins of spinal projections, ten Tegu lizards (Tupinambis nigropunctatus) received complete or partial hemisections of the spinal cord at the first or second cervical segment. Their brains were processed for conventional Nissl staining. The sections were surveyed for the presence or absence of retrograde chromatolysis. Based on analysis and comparison of results from lesions in the various spinal cord funiculi, the following conclusions were reached:

The interstitial nucleus projects ipsilaterally to the spinal cord via the medial longitudinal fasciculus, as does the middle reticular field of the metencephalon. The red nucleus and dorsal vagal motor nucleus both project contralaterally to the spinal cord via the dorsal part of the lateral funiculus. The superior reticular field in the rostral metencephalon and the ventrolateral vestibular nucleus project ipsilaterally to the spinal cord via the ventral funiculus. The dorsolateral metencephalic nucleus and the ventral part of the inferior reticular nucleus of the myelencephalon both project ipsilaterally to the spinal cord via the dorsal part of the lateral funiculus.

Several brainstem nuclei in Tupinambis project bilaterally to the spinal cord. The ventrolateral metencephalic nucleus, for example, projects ipsilaterally to the cord via the medial longitudinal fasciculus and contralaterally via the dorsal part of the lateral funiculus. The dorsal part of the inferior reticular nucleus projects bilaterally to the spinal cord via the dorsal part of the lateral funiculus. The nucleus solitarius complex projects contralaterally via the dorsal part of the lateral funiculus but ipsilaterally via the middle of the lateral funiculus. The inferior raphe nucleus projects bilaterally to the spinal cord via the middle part of the lateral funiculus.

These data suggest that supraspinal projections in reptiles, especially reticulospinal systems, are more highly differentiated than previously thought. On the other hand, recent findings in cat, opossum, and monkey reveal that the organization of supraspinal pathways in the Tegu lizard bears a striking resemblance to that observed in mammals.
Cell types of the auditory caudomedial neostriatum of the starling (Sturnus vulgaris)
Authors: Saini K. D. , Leppelsack H.‐J.
Published: May 2005

Cell types of the auditory neostriatum in the starling forebrain are described. This area in the caudal neostriatum is defined neurophysiologically by the appearance of auditory neurons.

Through use of the rapid Golgi technique, four types of neurons are identified, mainly on the basis of their processes: Neurons with long descending axons and thick dendrites rich in spines (type 1), neurons with long ascending axons and thin dendrites poor in spines (type 2), short‐axon neurons (type 3), and microneurons (type 4).

The axons of the long neurons pass outside the confines of the auditory neostriatum. Among neurons of type 1; some of the long descending axons directed toward the lower brain centers enter the capsula interna occipitalis (CIO). The descending axons give off many collaterals within the auditory neostriatum. With neurons of type 2; most of the ascending axons cross the lamina hyperstriatica, enter the hyperstraiatum ventrale, and arborize near its periventricular region. Some of the long ascending axons reach the overlying hyperstriatum ventrale, pars caudale (HVc, the vocal control area). Among neurons of types 3 and 4; the axons of short‐axon neurons and of microneurons end with fine branches within the auditory neostriatum.

The dendrites of long‐axon neurons are oriented in specific directions, whereas those of short‐axon neurons and of microneurons do not show a definite pattern of orientation.

In the region of the auditory neostriatum that lies immediately adjacent to the midline of the brain, the first three types of neurons are arranged around the central core known as field L, which is composed of the microneurons and the terminal ramifications of auditory afferents. Laterally the microneurons, along with the fibers of the input tract, undergo a rostral shift to occupy a more peripheral position within the auditory neostriatum.

The neurons of the auditory neostriatum are compared with those of the mammalian auditory cortex, and a functional classification of nerve cells into projection neurons, association neurons, and interneurons is proposed.
An intracellular electrophysiological study of the ontogeny of functional synapses in the rabbit retina. II. Amacrine cells
Authors: Dacheux Ramon F. , Miller Robert F.
Published: May 2005

Intracellular recordings in an isolated perfused retina‐eyecup preparation of the neonate rabbit were used to study the physiological development of amacrine cells. By responding with transient depolarizations at the onset and termination of illumination, mature mammalian on‐off amacrine cell recordings appeared similar to those described in lower vertebrates. However, immature amacrine cell recordings showed a predominantly on response, with off responses small and easily fatigued during repetitive stimulation. This underdeveloped off component of the amacrine cell response could also be abolished by decreasing the area of receptive field that was stimulated. The more slowly developing off component may reflect a different maturation rate of depolarizing (on) and hyperpolarizing (off) bipolar cells. In addition, properties of the maturing inner plexiform layer were examined with extracellular recordings of the proximal negative response (PNR). The PNR showed evidence of evidence of easy fatigability more evident in the off response. These observations are consistent with the idea that the initial phase of light sensitivity is associated with labile synaptic input from bipolar cells.
Immunohistochemical localization of substance‐P, somatostatin, and methionine‐enkephalin in the spinal cord and dorsal root ganglia of the north american opossum, Didelphis virginiana
Authors: Ditirro Frank J. , Ho Raymond H. , Martin George F.
Published: May 2005

The occurrence and distribution of substance‐P (SP), somatostatin (SOM), and enkephalin (ENK) were studied in the North American opossum, a generalized marsupial. Substance‐P immunoreactivity was present in the tract of Lissauer as well as within lamina I, the outer part of lamina II, the lateral portion of laminae III through VII, and lamina X at all spinal levels. Although present, it was very sparse in the ventral horn. Substance‐P was also localized within autonomic areas of the thoracolumbar cord. ENK immunoreactivity was present in laminae I‐III and laminae VII‐X, as well as within autonomic areas. There was more ENK immunoreactivity in the ventral horn than SP. The densest aggregates of ENK, however, were found within the outer part of lamina II. In contrast, SOM could not be localized within the spinal cord of the opossum. (See NOTE ADDEDIN PROOF).
Development of the brain stem in the rat. V. Thymidine‐radiographic study of the time of origin of neurons in the midbrain tegmentum
Authors: Altman Joseph , Bayer Shirley A.
Published: May 2005

Groups of pregnant rats were injected with two successive daily doses of 3H‐thymidine from gestational day E12 and 13 (E12 + 13) until the day before parturition (E21 + 22) in order to label in their embryos the proliferating precursors of neurons. At 60 days of age the proportion of neurons generated (no longer labeled) on specific embryonic days was determined quantitatively in 18 regions of the midbrain tegmentum. The neurons of the oculomotor and trochlear nuclei are generated concurrently on days E12 and E13. There was a mirror image cytogenetic gradient in these nuclei and this was interpreted as the dispersal of neurons derived from a common neuroepithelial source to the medial longitudinal fasciculus. Neurons in three other components of the tegmental visual system are produced in rapid succession after the motor nuclei. In the nucleus of Darkschewitsch peak production time was on days E12 and E13, extending to day E15; in the Edinger‐Westphal nucleus the time span was the same but with a pronounced peak on day E13; finally, the neurons of the parabigeminal nucleus were produced between days E13 and E15 with a peak on day E14. The neurons of the periaqueductal gray were generated between days E13 and 17 with a pronounced ventral‐to‐lateral and lateral‐to‐dorsal gradient.

In the red nucleus the neurons were produced on days E13 and E14 with a caudal‐to‐rostral gradient: the cells of the magnocellular division preceding slightly but significantly the cells of the parvocellular division. The neurons of the interpeduncular nucleus originated between days E13 and E15; the peak in its ventral portion was on day E13, in its dorsal portion on days E14 and E15. A ventral‐to‐dorsal gradient was seen also in both the dorsal and the median raphe nuclei in which neuron production occurred between days E13 and E15. The neurons of the pars compacta and pars reticulata of the substantia nigra were both produced between days E13 and E15 with a modified lateral‐to‐medial gradient. This gradient extended to the ventral tegmental area where neurons of the pars medialis were produced between days E14 and E16. With the exception of the central gray, neuron production was rapid and relatively early in the structures situated ventral to the midbrain tectum. A comparison of the cytogenetic gradients in the raphe nuclei of the lower and upper medulla, the pontine region, and the midbrain suggests that they originate from at least three separate neuroepithelial sources.
Transplantation of tectal tissue in rats. I. Organization of transplants and pattern of distribution of host afferents within them
Authors: Lund Raymond D. , Harvey Alan R.
Published: May 2005

We have examined the maturation of tectal tissue transplanted from fetal rats to the midbrain of newborns and have characterized the distribution of host retinal and cortical afferents within the transplants.

The transplants develop characteristic internal order and connections which distinguish them from either embryonic cortex or retina placed in the same region. Host retinal afferents project to clearly circumscribed regions, where they synapase mainly on small dendrites or dendritic spines, and only rarely on vesicle‐containing profiles. The retinorecipient areas contain few stained axons in neurofibrillar preparations and are almost always located at the surface of the transplant. There is very little overlap in the input from the two eyes into a single transplant even though the projections from each eye may lie adjacent to one another. Cortical afferents spread more broadly in the transplants, but are largely absent from areas of optic termination and from other more deeply located regions with sparse fiber staining properties.

The observations suggest that when placed close to its normal location, tectal tissue can develop a number of features characteristic of normal superior colliculus. Appreciation of the internal order of the transplants makes it possible to investigate the cortical and retinal afferent pathways using physiological techniques.
Trigeminal projections to the superior colliculus of the rat
Authors: Killackey Herbert P. , Erzurumlu Reha S.
Published: May 2005

The deep layers of the rodent superior colliculus contain a vibrissae‐related organization that is in “spatial register” with the overlying visuotopic organization (Dräger and Hubel, '76). The distribution of vibrissae‐related afferents and their cells of origin were determined with a number of anatomical techniques. The brainstem trigeminal complex afferents to the superior colliculus terminate in the lateral portions of the strata album intermediale and griseum profundum and, to a lesser degree, in deep portions of the stratum griseum intermediale. The cells giving rise to these afferents are located mainly in the ventral portions of the contralateral principal sensory nucleus, subnucleus oralis, and subnucleus interpolaris. The majority of tectal projection cells are found in subnucleus interpolaris, and the fewest in the principal sensory nucleus. Further, the density of projection cells in the three components of the brainstem trigeminal complex can be correlated with the density of their projections to the superior colliculus.

The afferents from the somatosensory cortex terminate in a continuous band in the strata album intermediale and griseum intermediale. The cells of origin of this projection are located in layer Vb of the agranular zones of the ipsilateral somatosensory cortex.

The present results suggest that the organization of trigeminal afferents to the deep portion of the superior colliculus is similar to that of the visual afferents to the superficial laminae. Further, the results suggest that observations on the nature of afferent termination patterns should be made with care, considering both the techniques employed and the idiosyncrasies of the local neuropil.
Evidence for a lack of distinct rubrospinal somatotopy in the North American opossum and for collateral innervation of the cervical and lumbar enlargements by single rubral neurons
Authors: Martin G. F. , Cabana T. , Humbertson A. O.
Published: May 2005

Studies using axonal transport techniques on the North American opossum show that rubral neurons innervating the cervical cord are not distinctly separated from those which project to lumbar levels. This absence of clear rubrospinal somatotopy contrasts with that described for the placental mammals studied to date. Use of fluorescent markers in double‐labelling experiments shows that most rubral neurons in the opossum still innervate either the cervical or lumbar enlargement alone, but that some supply collaterals to both levels.
Postnatal increase of unmyelinated axon profiles in the feline ventral root L7
Authors: Risling Mårten , Hildebrand Claes , Aldskogius Håkan
Published: May 2005

The proportion of unmyelinated axon profiles and possible agerelated, degenerative and regenerative alterations were studied ultrastructurally in the L7 ventral root of 25 cats ranging from 3 weeks to 11 years of age. For comparison, the ventral root C6 was examined in 5 of these animals. The sections were taken from a level midway between the proximal and distal ends of the roots. The proportion of unmyelinated axon profiles in the L7 ventral root increased from about 14% to around 31% between 4 and 7 months after birth. Simultaneously, the average number of unmyelinated axon profiles per Schwann cell was doubled from 2–3 to 4–5. Thereafter, these figures remained largely unchanged for at least a decade. The total number of myelinated axons was similar in kittens and in cats. In the C6 root the proportion of unmyelinated axon profiles was about 20%, both in kittens and in young or old adult cats. At both segmental levels in the oldest cats, some unmyelinated axons showed degenerative changes and medium‐sized and large axons had features characteristic of demyelination and remyelination.
Projections from visual areas of the middle suprasylvian sulcus onto the lateral posterior complex and adjacent thalamic nuclei in cat
Authors: Updyke B. V.
Published: May 2005

The distribution of corticothalamic projections from lateral suprasylvian areas AMLS, PMLS, ALLS, and PLLS was investigated with the autoradiographic method. Areas AMLS and PMLS were both found to project retinotopically upon the medial interlaminar nucleus and the lateral and pulvinar zones of the lateral posterior complex, as well as to the ventral lateral geniculate nucleus, intralaminar nuclei, and thalamic reticular complex. Retinotopic projections to the dorsal lateral geniculate nucleus were demonstrated from PMLS but not AMLS, and projections to zona incerta were demonstrated from AMLS but not PMLS. Areas PLLS and ALLS were both found to project retinotopically upon the interjacent zone of the lateral posterior complex, as well as to the intermediate and suprageniculate divisions of the posterior nuclear group, the magnocellular division of the medial geniculate complex, the thalamic reticular complex, and central lateral nucleus. Area ALLS was also found to project onto the dorsal division of the medial geniculate complex and lateral division of the posterior nuclear group. Differences between the four cortical areas in the pattern and density of their thalamic projections supports the parcellation of these areas as proposed by Palmer et al. ('78).

The projection patterns of areas PMLS, AMLS, PLLS, and ALLS were found to respect the boundaries of the zones of the lateral posterior complex, which had been identified and defined previously (Updyke, ′77), and the results thus support the hypothesis that these zones are the functional units of organization for visual traffic between the cat's extrastriate visual areas.
Observations on the organization of the visual cortex in the reeler mouse
Authors: Dräger Ursula C.
Published: May 2005

The developmental abnormality caused by the autosomal recessive mutation reeler leads to a systematic inversion in the depth distribution of morphologically defined cell classes in the cortex and to an abnormal course taken by thalamocortical projections (Caviness, '77). The course of the geniculocortical projections was visualized in reeler through transneuronal autoradiography. After traveling under the pial surface, the fibers terminate in a slightly patchy manner at intermediate levels of the primary visual cortex. As in the normal mouse, there is a weaker projection to the lateral part of area 17 ipsilateral to the injection. The retinal ganglion cells giving rise to the ipsilateral projection in reeler were labeled with horseradish peroxidase and were found to be located at normal positions in the retina.

The functional competence of the primary visual cortex in reeler was studied by recording the response properties of single cells. In most respects the reeler cortex appeared remarkably normal: the cortical topography of the visual‐field representations was normal overall, all receptive field types seen in the normal mouse were present, and cells within the binocular region received normally convergent input from the two eyes. The reeler differed from normal in having a greater number of poorly responding cells and a lower fraction of cells with oriented receptive fields. The tendency for oriented cells to occur preferentially in upper cortical layers in the normal mouse was not present in reeler.

These results imply that the cells in the reeler cortex are connected in a largely normal manner despite the gross malformation. Thus it appears that the specificity of intercellular connections, in reeler and in normal cortex, does not depend crucially upon the position of the cells in the cortex.
Evidence for cholinergic participation in the control of bird song: Acetylcholinesterase distribution and muscarinic receptor autoradiography in the zebra finch brain
Authors: Ryan Susan M. , Arnold Arthur P.
Published: May 2005

Brain regions thought to be involved in the control of song in the zebra finch (Poephila guttata), were examined histochemically using the Karnovsky and Roots direct‐coloring method for the detection of acetylcholinesterase (AChE) and the autoradiographic method for the localization of muscarinic cholinergic receptors following injection of tritiated quinuclidinyl benzilate (3H QNB). All presently identified vocal control nuclei in both males and females contain AChE. These nuclei include Area X, magnocellular nucleus of the anterior neostriatum (MAN), nucleus interface (NIF), caudal nucleus of the hyperstriatum ventrale (HVc), intercollicular nucleus (ICo), nucleus uva, robust nucleus of the archistriatum (RA), and tracheosyringeal portion of the hypoglossal nerve nucleus (nXIIts). All nuclei except Area X contain mostly AChE‐synthesizing cell bodies. All of these nuclei contain some AChE in the neuropil, with particularly intense staining in Area X, the surrounding LPO, and the dorsomedial portion of ICo. In agreement with this description are very high concentrations of 3H QNB in both Area X and the dorsomedial ICo. HVc also appears specifically labeled. Evidence from these two histological techniques suggests that efferent projections of most vocal control areas may untilize acetylcholine, and that several of the vocal control nuclei may themselves receive muscarinic cholinergic projections. In Area X, there are sex differences in AChE neuropil staining. This evidence suggests that sexually dimorphic projections to or within Area X are cholinergic or cholinoceptive.
The retinal projection to the thalamus in the cat: A quantitative investigation and a comparison with the retinotectal pathway
Authors: Illing R.‐B. , Wässle H.
Published: May 2005

The projection of cat retinal ganglion cells to the thalamus was examined using the method of retrograde axonal transport of horseradish peroxidase (HRP). After the injection site was determined physiologically, HRP was applied by one of three methods: iontophoretic injection of minimal amounts, single pressure injections and multiple pressure injections.

Iontophoretic injections into single laminae of the dorsal part of the lateral geniculate nucleus (LGNd) revealed that laminae A and A1 receive almost exclusively axon terminals from α and β cells. Single pressure injections elucidated the retinotopic organization of the LGNd. Multiple injections lead to HRP uptake in the whole LGNd including parts of adjacent thalamic nuclei and revealed that at least 77% of all retinal ganglion cells project to the thalamus. This pathway is made up of all α cells, all β cells and almost half of the γ cells. The thalamus receives its visual input predominantly from the ipsilateral temporal and the contralateral nasal retina; some α cells were also labeled in the contralateral temporal retina.

The shape of the decussation line was analyzed and its width was found to be proportional to the average ganglion cell spacing along the dorsoventral axis of the retina. From a comparison of the retinothalamic and retinotectal pathways, an estimate of the number of cells with bifurcating axons could be given. The axons of all α cells, 10% of the β cells, and every second γ cell bifurcate; this amounts to 30% of the retinal ganglion cells.
Fibers in spinal nerves of tree frogs: Eleutherodactylus and Hyla
Authors: Sutherland Rodrique M. , Nunnemacher Rudolph F.
Published: May 2005

This is a study on numbers and sizes of nerve fibers as determined by electron microscope mapping of the spinal nerves of two species (in different families) of tree frogs. The study provides data for comparison of fiber populations in the grass frog, Rana pipiens. In both tree frogs the greatest number of fibers in the ten pairs of spinal nerves are in the second and ninth rami. The combined counts of myelinated and unmyelinated fibers in the rami on one side of the cord in Eleutherodactylus and Hyla are respectively: to the forelimb, 3,147 and 4,460 fibers; to the trunk, 334 and 1,234 fibers; and to the hindlimb, 4,335 and 6,213 fibers. With a few notable differences this distribution of fibers to regional body parts correlates closely with that found in Rana. The arboreal frogs have a relatively smaller number of medium and especially large size fibers in comparison with the aquatic‐terrestrial living grass frog. The importance is stressed of examining the spinal nerves of an entirely aquatic frog with different feeding habits, such as Xenopus, for further comparison.
Magnification functions and receptive field sequences for submodality‐specific bands in SI cortex of cats
Authors: Dykes Robert W. , Gabor Andrew
Published: May 2005

Electrophysiological data were collected from the forelimb region of somatosensory cortex in barbiturate‐anesthetized cats using low‐impedance microelectrodes in long slanting trajectories. Subsequently, the brains were fixed and stained with thionin to locate the electrode trajectories and to correlate cytoarchitecture with neural activity. Confirming earlier experiments, regions of cortex, preferentially responsive to one submodality of afferent input, were observed to stretch in mediolateral bands across SI. Separate magnification functions were calculated for each band. In the forelimb region the magnification functions for the deep and cutaneous RA bands could be approximated by linear functions while the data for the cutaneous SA band was best described by a second‐order equation. At least in the forelimb region this magnification function applied only along the anteroposterior dimension of the band because the body representation is anisotropic; along the anteroposterior dimension of the band, receptive field loci may change only millimeters on the skin when the electrode moves through 1 mm of cortex, whereas when an electrode moves in a mediolateral direction they change centimeters on the forearm for an equivalent cortical distance.

Each representation is separated from the others by a transition zone having a minimal width less than 200 m̈m. Within the transition zones, neurons often have receptive field loci which are a compromise between loci found in the adjacent representations. In these zones responses are often difficult to elicit. Electrode penetrations encountering these transition zones contain data which fulfill the receptive field and modality criteria for the boundary of a cortical column. However, within the mediolateral length of each submodality band we have found no unit with a dimension greater than 200 m̈m which has a boundary or transition zone. Evidence for units of smaller size cannot be obtained because of limitations in the data collection techniques. Thus, within each submodality‐specific band, large portions of the somatotopic map appear to be a mediolateral continuum while relatively abrupt changes occur in receptive field locus and in submodality when the electrode passes through a transition zone between adjacent bands.
Morphological study of noradrenaline innervation in the caudal raphe nuclei with special reference to fine structure
Authors: Takagi Hiroshi , Yamamoto Kazumi , Shiosaka Sadao , Senba Emiko , Takatsuki Kenichi , Inagaki Shinobu , Sakanaka Masahiro , Tohyama Masaya
Published: May 2005

Previous histofluorescence studies have demonstrated that the caudal raphe nuclei (CRa) of the rat, particularly the ventral portion (VCRa), contains a very high density of noradrenaline (NA) terminals and in the present study we attempted to elucidate the origins and free structure of the NA terminals in this region.

The majority of NA terminals found in the VCRa originated from A1 and A3 NA neurons and disclosed that a small number of very strongly fluorescent fibers located along the blood vessels arise from the superior cervical ganglion (SGC). Electron microscopic analysis after potassium permanganate fixation demonstrated that the NA terminals originated from A1 and A3 NA neurons are connected with neuronal elements, while NA fibers from the SGC were identified among the vascular elements. Axodendritic contacts were found to be predominant among the synapselike contacts of NA terminals in this area.
Alterations in cerebellar germinal cell division induced by graft‐versus‐host disease
Authors: Griffin W. S. T. , Crom E. N. , Head J. R.
Published: May 2005

A systemic immunological syndrome, graft‐versus‐host disease (GVHD), which does not cause inflammation or cell death in the cerebellum, is shown to retard granule cell production by decreasing the rate of DNA synthesis (S phase) and prolonging mitosis (M), at metaphase. The rate of cell production in diseased animals at postnatal day 14, quantitated by analysis of the rate of labeling of DNA with 3H‐thymidine (3H‐Tdr), revealed decreased ability to synthesize new DNA. The number of cells taking up 3H‐Tdr label per mm2, as detected by autoradiography, was similar in 14‐day‐old GVHD and control tissue as was the area of the germinal matrix zone and the number of mitotically active germinal cells per mm2 in sagittal sections near the midline. However, because the total volume of the cerebellum was less, the total number of mitotically active cells in the whole cerebellum of 11‐, 14‐, and 17‐day‐old diseased animals was less than in littermate controls. Furthermore, DNA synthesis per mitotically active germinal cell was less in diseased animals at each age examined. The mitotic index was unaffected until late in the disease (day 17), suggesting that a prolongation of the cell cycle was responsible for this GVHD‐induced decrease in DNA synthesis. Consistent with a prolongation of the cell cycle was the finding that the mitotic figures in 14‐day‐old GVHD cerebella were mostly metaphase figures, whereas those in control cerebella were, as predicted, mostly prophase. Prolongation of the cerebellar cell cycle in 11‐ and 14‐day‐old diseased animals may explain the dramatic decrease in the mitotic index, the thickness of the germinal matrix zone, and the number of germinal cells at postnatal day 17.