bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of neurons in cat's dorsal lateral geniculate nucleus: A comparison between medial interlaminar and laminated parts of the nucleus
Authors: Dreher Bogdan , Sefton Ann Jervie
Published: January 2005

We studied the receptive field properties of 460 cells in the cat's dorsal lateral geniculate nucleus (LGNd), 108 cells were located in the medial interlaminar nucleus (MIN) and 352 in the laminated part of the LGNd.

In both the MIN and laminated parts of the LGNd, relay cells belonging to all three functional classes (W, X and Y) have been identified. Of cells in the laminated LGNd, about 32.5% were Y cells, about 54.5% were X cells and about 8.5% were W cells. By contrast, in the MIN, about 84% were Y cells, only about 4.5% being X cells and about 7.5%, W cells. In the laminated LGNd, Y cells represented 25% of cells with receptive fields near the area centralis (0–3° eccentricity group) and about 42% in the group of cells with the most peripherally located receptive fields (20–40° eccentricity group). A similar but much weaker trend was observed in the MIN. In the laminated LGNd but not in the MIN the receptive field center sizes increased with increasing eccentricity of receptive field position. At any eccentricity, receptive field centers of MIN Y cells tended to be larger than those of Y cells in the laminated LGNd.

Response latency ranges to orthodromic and antidromic stimulation were the same for cells located in the laminated LGNd and those in the MIN. However, the mean response latency to stimulation of the optic chiasm was significantly shorter for Y cells in MIN than for Y cells in the laminated LGNd.

Our results suggest that the most numerous cells observed histologically in the MIN, class 1 cells of Guillery ('66) are morphological equivalents of Y cells.
Properties of superior colliculus neurons in the golden hamster
Authors: Stein Barry E. , Dixon James P.
Published: January 2005

A laminar representation of sensory modalities was present in the hamster superior colliculus (SC) with upper laminar cells being exclusively visual, while intermediate and deeper layer cells were visual, somatic acoustic or multimodal.

Receptive field (RF) properties of visual SC cells were studied quantitatively with stationary spots and moving bars of light of various sizes, velocities and directions of movement. The most effective stimuli were usually less than half of the diameter of the RF. Increasing stimulus size beyond a critical range produced progressively lower discharge rates even though the stimulus was confined within the borders of the RF. Low velocities (10–50°/sec) were most frequently optimal for both upper and lower laminar cells and the majority of cells were directionally selective. Movements in the upper nasal direction usually elicited the highest discharge rates and were thus preferred most frequently. However, directional preferences often could be minimized, or obliterated, by employing nonoptimal stimulus sizes and/or velocities.

Most intermediate and deeper laminar somatic cells could be activated by gentle cutaneous stimuli and a general somatotopic plan, which was in register with the overlying visuotopy, was noted. Cells optimally, or solely, activated by noxious stimuli were also located, but RFs of such cells were extensive and a somatotopic plan was not apparent.

Although species differences are apparent, the similarities between the organization and the RF properties of SC cells of the hamster and distantly related species are striking. Apparently the same SC system is adaptive in diverse species despite the very different behavioral repertories of these animals and their different ecological niches.
The formation of afferent patterns in the somatosensory cortex of the neonatal rat
Authors: Killackey Herbert P. , Belford Gary R.
Published: January 2005

In the rat, the clustered pattern of thalamocortical afferent terminals to the “barrel field” portion of primary somatosensory cortex replicates the arrangement of vibrissae on the face, and the pattern of the terminals can be altered by the removal of vibrissae at birth (Killackey et al., 1976). These patterns of terminals were studied using the enzyme succinic dehydrogenase (SDH) because in somatosensory cortex the activity levels of SDH closely correspond to the patterns of thalamocortical afferent terminals.

The present experiments show that the pattern of high SDH segmentation in the portion of layer IV of somatosensory cortex that is related to the vibrissae develops during postnatal Days 3 through 6. Activity related to the centers of individual clusters is first visible, with indistinct boundaries. At later times the edges of individual clusters become apparent. Further, in animals with Row C of vibrissae removed at birth, the abnormal SDH segmentation in somatosensory cortex develops with a time course similar to that of normal animals. At ages when edge boundaries are first distinct, a fused band corresponding to the removed row of vibrissae is present. Thus the aberrant organization seen in the adult cortex is the result of an abnormal initial development, not a later reorganization from a normal pattern. And indeed, vibrissae removal at Day 5 or 6 does not result in an aberrant cortical SDH pattern. Finally, after removal of all five rows of mystacial vibrissae at birth, the cortical SDH pattern seen at postnatal Days 6 and 7 consists of five bands in place of the normally present five rows of clusters. This may indicate that closer relationships exist between vibrissae within one row than vibrissae in adjacent rows.
An ultrastructural study of schwann cell response to axonal degeneration
Authors: Payer Andrew F.
Published: January 2005

Adult Sprague‐Dawley rats were used to prepare isolated and distal segments of ovarian, vagus and saphenous nerves. Isolated segments were prepared by cutting between double ligatures followed by retracting and anchoring the proximal and distal segments 0.5 cm or more away from the isolated piece. After various intervals between 3 and 123 days the rats were perfused with buffered glutaraldehyde and nerves were processed for electron microscopic examination. Cross sections of isolated and distal segments of all nerves displayed an abundance of mostly circular profiles containing microtubules and filaments that were indistinguishable from those in unmyelinated nerve fibers. Many such profiles were nested against perinuclear Schwann cell cytoplasm, others were present in isolated clusters enclosed only by basement membrane. Examples of continuity between the nerve‐like profiles and perinuclear cytoplasm of Schwann cells were found in longitudinal sections. In time, the number of such processes gradually diminished, but 123 days after transection they still could be found. It was concluded that Schwann cells in isolated and distal segments of transected nerves develop great numbers of small cylindrical processes that are arranged in bundles parallel to the long axis of the degenerated nerve. These processes had an arrangement of cytoplasmic organelles similar to axons of the proximal segment and the contralateral nerve. However the processes differed from most mature axons in that they were not ensheathed by Schwann cell cytoplasm with a mesaxon.
The afferent and efferent connections of the ventromedial thalamic nucleus in the rat
Authors: Herkenham Miles
Published: January 2005

The afferent and efferent connections of the ventromedial (VM) nucleus of the thalamus in the rat were studied by experiments using the methods of retrograde cell marking by horseradish peroxidase (HRP) and anterograde fiber tracing by autoradiography. Tritiated amino acids deposited microelectrophoretically into VM label a cortical projection that is distributed to a sharply defined superficial portion of layer I of almost the entire extent of the ipsilateral neocortex. The labeling is most dense at frontal cortical levels, where fibers radiate through the deeper layers to terminate in the outer one‐quarter of layer I throughout all neocortex rostral to the genu of the corpus callosum. A lesser number of labeled fibers extends caudally in a supracallosal location to innervate parieto‐occipital cortical areas. Labeled collaterals ascend through the cortical layers to reach layer I, where grains in the superficial portion are found in a gradually decreasing rostrocaudal gradient of density that reaches the caudal pole of the hemisphere. Coronal sections at most levels contain a band of labeling in layer I that extends uninterrupted from the callosal sulcus at the midline to the banks of the rhinal sulcus laterally. Caudal retrosplenial and ventral temporal areas appear to be the only sectors of neocortex spared by the ubiquitous projection. Evidence for additional terminal distribution in deeper layers is found only in the dorsal and lateral sectors of the cortex rostral to the genu where sparsely labeled bands appear in layers III and V. The nearly exclusive distribution of VM's cortical afferents to layer I is compared and contrasted with multilaminar distributions of other “unspecific” cortical afferent fibers.

HRP injected into VM labels neurons in a variety of structures at levels ranging from the frontal cortex to caudal medulla. Cell labelling in the globus pallidus, deep layers of the superior colliculus, cerebellar nuclei and the substantia nigra, pars reticulata suggest that VM is a point of convergence for several components of the extrapyramidal motor system. The nigrothalamic projection is topographic: medial and lateral districts of the pars reticulata are connected to medial and lateral districts of VM, respectively. A dorsal‐ventral association may also obtain. Cell labeling in the prefrontal cortex, the cortex along the rhinal sulcus, the lateral habenular nucleus, tegmental and medullary reticular formations, and parabrachial nuclei indicates that VM also receives projections from more heterogeneous sources.
Electron microscopic evidence of a ventronasal to dorsotemporal variation in fiber size in pigeon optic nerve
Authors: Duff Thomas A. , Scott Grayson
Published: January 2005

Using a uniform sampling method, electron‐microscopic examination of pigeon optic nerve revealed a dorsotemporal to ventronasal gradient in mean fiber size. In the dorsotemporal region small, myelinated axons (mean diameter = 0.87 μm, S.D. = 0.27) were predominant. Also unique to this region were scattered clusters of fine, unmyelinated fibers. A wider, bimodal spectrum in fiber size (mean diameter = 1.50 μm, S.D. = 0.66) was found in the ventronasal region of the nerve. Axons located in the area between these regions possessed a (mean diameter of 1.15 μm, S.D. = 0.43) This gradient, constant throughout the length of the nerve, resulted from a nasal‐to‐temporal diminution in size and frequency of large fibers superimposed upon a relatively uni form small fiber base. The total number of fibers within the nerve, excluding those comprising the unmyelinated clusters, was calculated to be approximately 2.3 × 106. The overall distribution in fiber size appeared to be unimodal with the peak at 0.75 μm and mean diameter = 1.04 μm, S.D. = 0.44. Although previous invertigators have reported that cross‐sectional analysis of pigeon optic nerve revealed a homogeneous distribution in fiber size, the findings of the present study may be more compatable with anatomical and physiological features of pigeon retinotectal organization. These features include visual field acuity gradients, ganglion cell population pattern, and dendity fields of tectal afferent terminations.
A neurophysiological determination of the vertical horopter in the cat and owl
Authors: Cooper Michael Lee , Pettigrew John D.
Published: January 2005

We have undertaken a determination of the vertical horopter in two species by simultaneously mapping the receptive field positions of binocular cortical neurons at various elevations along the zero azimuthal meridians.

In the paralyzed cat our recordings show that the zero meridians of the two eyes are parallel and vertical under paralysis. Slit‐pupil photographs demonstrate that paralysis induces an average net intorsion of 9° between the two eyes. Correction back to the unparalyzed state results in the zero meridians themselves being out‐torted with respect to each other. Since the two eyes' zero meridians define physiologically the positions of corresponding retinal points, this out‐torsion results in a vertical horopter in the mid‐sagittal plane which is tilted away from the alert, unparalyzed cat.

The limited eye movements of the owl permit the use of an unparalyzed preparation; it is therefore possible to avoid the problem of the cyclotorsion under paralysis which occurs in the cat. The results of our physiological analysis in the burrowing owl (Speotyto cunicularia) also reveal a tilted horopter in this terrestrial avian species.
The location of spinal neurons with long descending axons (long descending propriospinal tract neurons) in the cat: A study with the horseradish peroxidase technique
Authors: Matsushita Matsuo , Ikeda Michiko , Hosoya Yasuhiko
Published: January 2005

The distribution of spinal neurons with long descending axons was studied in the cat by means of retrograde transport of horseradish peroxidase. Labeled neurons appeared bilaterally in the cervical and the thoracic cord following injections in the lumbosacral cord. In some cases hemisections were made rostrally and contralaterally to the injections in an attempt to determine whether or not the axons crossed.

Neurons with uncorssed descending axons were located in laminae I, V, VII and VIII. Lamina I neurons were present in all the spinal segments. In lamina V labeled neurons were distributed mainly laterally in the cervical cord but medially and laterally in the thoracic cord. In the upper cervical and the thoracic cord laminae VII and VIII neurons were distributed very densely along the lateral cord, accounting for 30% and 40% of the total labeled neurons, respectively. In the cervical enlargement they were located in the middle part of lamina VII and in lamina VIII, accounting for about 25% of the total labeled neurons. Neurons with crossed descending axons were found in laminae VI, VII and VIII, in the medial part of lamina VII including the intermediomedial nucleus of the thoracic levels and close to the central canal. Lamina V neurons were very small in number. The largest collections of labeled neurons were present in the medial part of laminae VII and VIII. They accounted for about 45% to 55% and 37percnt; of the total in the cervical and the thoracic cord.

These neurons may function as the long spinal reflex paths for forelimb‐hindlimb synergies and the intercalated paths between the supraspinal descending tracts and the spinal motor centers.
Anatomical organization of the spinocerebellar system in the cat, as studied by retrograde transport of horseradish peroxidase
Authors: Matsushita Matsuo , Hosoya Yasuhiko , Ikeda Michiko
Published: January 2005

The distribution of spinocerebellar tract (SCT) neurons has been studied in the entire length of the spinal cord of the cat following injections of horseradish peroxidase into the cerebellum, and whether or not the axons of the labeled neurons crossed within the spinal cord was determined in cases with injections preceded by hemisections at the cervical levels.

The SCTs were classified into the following corssed and uncrossed tracts according to the cell origin and the fiber course; The crossed SCTs originate from (1) the central cervical nucleus (the CCN‐SCT), (2) lamina VIII neurons of the cervical to the lumbar cord (the lamina VIII‐SCT), (3) spinal border cells (the border cell‐SCT), (4) neurons in the medial lamina VII of the lumbar to the caudal spinal segments (the medial lamina VII‐SCT), (5) ventral horn neurons (laminae VII and VIII) of the sacral and caudal segments (the ventral horn‐SCT) and (6) dorsal horn neurons (lamina V) of the sacral and the caudal segments (the dorsal horn‐SCT). The uncorssed tracts originate from (1) neurons of the medial lamina VI of C2 to T1 (the medial lamina VI‐SCT of the cervical cord), (2) neurons in the central part of lamina VII of C6 to T1 (the central lamina VII‐SCT of the cervical enlargement), (3) lamina V neurons of the lower cervical to the lumbar cord (the lamina V‐SCT), (4) Clarke's column (the Clarke's column‐SCT) and (5) neurons in the medial lamina VI of L5 and L6 (the medial lamina VI‐SCT of the lumbar cord).

The present study suggests that the spinocerebellar system originates from more diverse laminae than has previously been known, and further refined studies on the topographic projections of each tract will yield more important and valuable information in this field.
Differential origins of spinothalamic tract projections to medial and lateral thalamus in the rat
Authors: Giesler Glenn J. , Menétrey Daniel , Basbaum Allan I.
Published: January 2005

In an earlier study (Giesler et al., 1976), antidromically identified cells of origin of the rat spinothalamic tract (STT) were found to be widely distributed throughout the lumbar dorsal horn and intermediate gray zone (IGZ). Interestingly, it appeared that STT neurons located within the ventral dorsal horn and IGZ, which appeared to respond to stimuli delivered to subcutaneous tissue, tended to be activated only from midline thalamic structures. In contrast, STT neurons within nucleus proprius and the marginal zone, which responded to noxious and innocuous cutaneous stimuli, were activated from lateral thalamic structures. The present study has investigated this apparent dichotomy in thalamic afferents using the technique of retrograde transport of horseradish peroxidase (HRP).

Single and multiple small injections of HRP were made in various thalamic regions. Tissue was reacted with diaminobenzidine (DAB) or o‐dianisidine (OD). Our data provide evidence that DAB histochemistry yields a more accurate reflection of the HRP concentrations surrounding an injection site which are necessary for visible retrograde transport. On the other hand, OD was found to be the more useful technique for examining labeled spinal cord neurons. With this method, 3 to 5.3 times more STT neurons were seen and far greater morphological detail was evident.

Multiple HRP infusions which filled an entire hemi‐thalamus labeled large numbers of cells within the spinal extensions of the dorsal column nuclei, the lateral cervical nucleus, the ventral horns and IGZ bilaterally within C1 and C2, and the nucleus proprius and IGZ at all levels. STT neurons were also seen, but in lesser numbers within the marginal zone. Labeling in spinal segments below C3 was, with a single exception, exclusively contralateral. The lumbar enlargement was seen to contribute a greater number of STT neurons than the cervical enlargement. Injections into posterior medial thalamic structures produced bilateral labeling in the ventral horns and IGZ in upper cervical segments. Within the cervical and lumbar enlargements, labeled neurons were restricted to ventral dorsal horn and to IGZ contralaterally. With the exception of the ventral horn cells of C1 and C2 where a marked reduction in labeling occurred, more anterior medial thalamic injections produced labeling within the identical areas of the gray matter and in numbers comparable to those produced by more posterior medial thalamic injections. In contrast, injections into lateral thalamic areas yielded dense labeling within the caudal extensions of the dorsal column nuclei and lateral cervical nucleus. Labeled cells were seen in the marginal zone and nucleus proprius at all levels.

Together with our earlier findings, these data suggest that the rat STT is composed of two components which vary in their cells of origin, their terminations and, very likely, their functions.
Modification of neuron numbers in the visual system of the rat
Authors: Cunningham Timothy J. , Huddelston Chris , Murray Marion
Published: January 2005

After unilateral lesions of the posterior cerebral cortex at birth, the ipsilateral dorsal lateral geniculate nucleus disappears within 96 hours. Several of the remaining visual centers may be distorted, atrophic or hypertrophic. Examples of the last are the ipsilateral nucleus of the optic tract (NOT) and superficial layers of the superior colliculus (SC), which usually show a volume increase. In order to determine changes in neuron numbers in these two regions, we exposed rats to 3H‐thymidine on specific embryonic days. Some of these rats received posterior cortical lesions on the day of birth and others served as controls. Counts from adult rats exposed to 3H‐thymidine on embryonic days 13 and 14 reveal a significant increase in the number of labeled neurons in both the NOT and SC on the side of the lesion. The retinal projections in rats with posterior lesions at birth were determined by the application of silver degeneration methods after eye removal. Atypical optic projections are found to the lateral posterior nucleus and the NOT on the side of the lesion. We conclude that the redistribution of optic collaterals after early destruction of the dorsal lateral geniculate nucleus serves to increase neuron numbers in the NOT and SC. Therefore, the present findings are comparable to the results in nonmammals after transplantation of additional peripheral organs.
Somatic neurons in the brainstem and neocortex projecting to the external nucleus of the inferior colliculus: An anatomical study in the opossum
Authors: Robards Martine J.
Published: January 2005

Some brainstem and neocortical neurons projecting to the external nucleus of the inferior colliculus were identified by retrograde axonal transport of horseradish peroxidase (HRP). Large pressure injections of HRP were used to define the population of cells in the dorsal column and trigeminal nuclei projecting to the entire inferior colliculus. Subsequently, tiny injections of HRP were delivered electrophoretically to various parts of the external nucleus using micropipettes. In each case the electrophoretic placements were made in sites identified as somatic by their response to foot shock or manual stimulation of the body. Receptive fields were found to be large and almost always bilaterally symmetric. Areas excitable by stimulation of the upper body were often found adjacent to areas excitable by stimulation of the lower body, tail, or, rarely, the face and head. In general, sites in the external nucleus which were identified by their responsiveness to stimulation of the body were not responsive to click stimuli. No topographic representation of the body was evident. After small electrophoretic injections of HRP absolutely restricted to the external nucleus, HRP‐filled neurons were found bilaterally in the nucleus gracilis, nucleus Bischoff, (the midline and tail representation of the dorsal column nuclei), nucleus cuneatus, and nucleus trigeminalis, subnucleus caudalis. Ipsilateral neocortical cellular filling was found primarily in a continuous strip along the caudal and inferior margin of the parietotemporal cortex, in the area corresponding to SMII (Pubols, '77). Rarely, filled cells were found in the parietal area corresponding to SMI and in the temporal pole. In sum, small somaticactivated loci of the external nucleus receive bilateral, topographically convergent projections from hindbrain somatosensory structures and from the SMII cortex.
Commissural and intrinsic connections of the rat hippocampus
Authors: Laurberg S.
Published: January 2005

The commissural and intrinsic connections of the hippocampus were studied using the Fink‐Heimer method and the horseradish peroxidase (HRP) uptake technique.

A conspicuous septo‐temporal gradient was found of the density of the commissural projection that passes through the psalterium ventrale to the Ammon's horn. The degeneration resulting from transection of the psalterium ventrale was most dense in the septal tip and decreased towards the temporal tip. The commissural and ipsilateral connections from the hilus fasciae dentatae (CA4) and regio inferior (CA3/CA2) were found to terminate in different parts of the hippocampus. The hilus fasciae dentatae gave rise to ipsilateral and commissural projections to the dentate area only. The regio inferior has ipsilateral and commissural projections to the Ammon's horn.

A specific termination pattern was found of the projection from regio inferior to stratum radiatum of both the ipsilateral and contralateral regio superior (CA1) and regio inferior (CA2/CA3). At levels temporal to the lesion, the projection is primarily to the superficial part of stratum radiatum, while at levels septal to the lesion the terminal zone occupies the deep part of the layer. This pattern was not related to the position of the cells of origin, along the septotemporal or subiculo‐dentate axes.

In general, the commissural projections showed the same degree of septotemporal divergence as the ipsilateral projections. The only major difference in the terminal fields of the two sets of projections to the Ammon's horn was that the terminal zone of the commissural projection to stratum oriens was always more dense than that of the ipsilateral projection to this layer, while an inverse gradient was seen in stratum radiatum.

The projections from the septal and middle dorso‐ventral parts of regio inferior differed. The temporal spread of the projections from the septal part was large while that from the projections arising at middle dorso‐ventral levels was more restricted. Moreover, a longitudinal association path interconnecting different parts of the regio inferior along the septo‐temporal axis was seen to arise only from the cells in the septal parts of the regio inferior.

Each part of the regio inferior projected to all parts of stratum radiatum and oriens of the contralateral Ammon's horn. However, the projection to the contralateral regio inferior was most dense at the site homotopic to that lesioned. The ventricular part of regio inferior projected primarily to the contralateral stratum oriens of the Ammon's horn, while the part adjacent to the dentate area mostly supplied stratum radiatum.
Behavioral and electrophysiological effects of unilateral optic tract section in ordinary and siamese cats
Authors: Antonini A. , Berlucchi G. , Marzi C. A. , Sprague J. M.
Published: January 2005

In ordinary cats section of one optic tract produced a complete contralateral hemianopsia in both eyes. Single‐unit recordings showed a normal representation of the contralateral nasal retina and ipsilateral temporal retina in the SC on the side of the intact optic tract. In addition, in the rostral portion of this SC there was a representation of a small portion of the contralateral temporal retina. This portion was apposed to the vertical meridian and its width was at most 6°. In the anterior half of the SC on the side of the optic tract section, despite the interruption of any direct optic input, there was an extensive representation of the ipsilateral nasal retina and the contralateral temporal retina. This indirect visual input to the SC ipsilateral to the optic tract section was absent in a cat with a section of the forebrain commissures.

In Boston Siamese cats, section of one optic tract led to a virtually complete blindness in the eye contralateral to the section, whereas the other eye retained a full visual field, although the responsiveness of the temporal retina beyond 20° from the vertical meridian was reduced. Similarly, the nasal hemiretina and most of the temporal hemiretina on the side of the section were represented in the opposite SC, whereas stimulation of the eye contralateral to the section could not drive SC units. There was some evidence that the visual field of the eye on the side of the section could at least in part be represented in the SC on the same side. The findings indicate that the crossed projections from temporal hemiretina in the ordinary cat, and the uncrossed projections from temporal hemiretina in the Siamese cat are insufficient by themselves to sustain visual orientation and to drive SC neurons. Each half of the visual field in the ordinary cat, and the field of each eye in the Siamese cat, can be represented in the ipsilateral SC via across‐the‐midline, indirect connections.
Fine structural analysis of the cortico‐striatal pathway
Authors: Hattori T. , McGeer E. G. , McGeer P. L.
Published: January 2005

Considerable evidence has accumulated indicating that one neurotransmitter in the excitatory cortico‐striatal tract is glutamate. Lesions of the tract result in reductions in the striatum of glutamate levels as well as high affinity uptake of glutamate into synaptosomes. Furthermore, such lesions leminate the neurotoxicity of the glutamate analog kainic acid when injected into the striatum. The fine structure of the cortico‐striatal pathway was studied to provide evidence regarding the morphology of glutamate nerve endings.

Seven days after injection of 3H‐proline (20–25 μCi) into the rat frontal cortex, axonally transported label appeared in the striatum with uniform distribution in a single type of nerve ending. The labeled boutons had common round vesicles and made asymmetrical contacts, mostly with dendritic spines. This morphology is typical of excitatory synapses, and similar to that previously shown for cholinergic boutons in the striatum.

In four animals similarly injected with 3H‐proline, kainic acid was administered directly into the striatum to induce degeneration of postsynaptic elements eight to ten hours before sacrifice. In areas affected by these injections, grains appear in pathches, possibly resulting from glial swelling. Labeled boutons were seen almost four times as often in synaptic contact with degenerating dendritic elements as with normal ones. The data provide morphological evidence as to the nature of the probable glutamatergic boutons in the striatum, and show the close relationship of such boutons with the neurotoxic effects of kainic acid. This would be anticipated in view of the dependency of kainic acid neurotoxicity on the intergrity of the cortico‐striatal pathway.
A quantitative study of lipofuscin accumulation with age in normals and individuals with Down's syndrome, phenylketonuria, progeria and transneuronal atrophy
Authors: West Christopher D.
Published: January 2005

The amount of lipofuscin in neurons of two brainstem nuclei, the inferior olivary nucleus (ION) and the lateral geniculate nucleus (LGN), was measured in the brains of 1 progeric, 2 phenylketonuric, 5 Down's syndrome and 13 normal individuals. Aggregations of lipofuscin granules in cresyl violet stained sections were examined with epi‐fluorescent illumination, drawn with a camera lucida, and measured with a planimeter. The proportion of lipofuscin to cell size was a linear function of age over the age range examined, 14 to 92 years. There was no difference between progeric, phenylketonuric, Down's and normal brains in the amount of lipofuscin accumulated with age, nor was there a marked within‐individual correlation between amounts of lipofuscin in the two nuclei when these amounts were subtracted from the regression line values to control for age. The proportion of lipofuscin to cell size was the same in neurons of the LGN showing transneuronal atrophy in response to right eye pathology as it was in non‐atrophic neurons.
Reexamination of the dorsal root projection to the spinal dorsal horn including observations on the differential termination of coarse and fine fibers
Authors: Light A. R. , Perl E. R.
Published: January 2005

Primary afferent fibers in the lumbar, sacral, and caudal spinal segments of several mammals (rat, cat, monkey) were stained by applying horseradish peroxidase to the proximal part of cut dorsal rootlets and reacting the tissue histochemically after several hours of survival. The stained fibers' pattern of termination in the dorsal horn was similar in all three species, with many bouton‐like enlargements in the ipsilateral marginal zone, substantia gelatinosa, and nucleus proprius, as well as a few projections at each level to the dorsal commissure and contralaterally to the ventral border of the nucleus proprius. Partial lesions of dorsal rootlets in monkey revealed that the thin fibers comprising the lateral division end principally in the marginal zone and substantia gelatinosa, while the thick fibers of the medial division terminate in the nucleus proprius and deeper regions, contributing little to the substantia gelatinosa and marginal zone. On the basis of the termination patterns observed for whole and partly sectioned rootlets, the superficial dorsal horn can be divided into at least four regions. (1) The marginal zone (lamina I of cat) appears to receive terminations from intermediate (smaller myelinated) fibers; (2) the outer substantia gelatinosa (outer lamina II) receives many terminations from the very finest afferent fibers; (3) the inner substantia gelatinosa (inner lamina II) receives endings from some of the finest fibers and also from intermediate (smaller myelinated) fibers; and (4) the superficial part of the nucleus proprius (lamina III) receives endings from intermediate and large diameter dorsal root fibers.
Trajectory of group Ia afferent fibers stained with horseradish peroxidase in the lumbosacral spinal cord of the cat: Three dimensional reconstructions from serial sections
Authors: Ishizuka Norio , Mannen Hajime , Hongo Toshinori , Sasaki Shigeto
Published: January 2005

A reconstruction was made of the intramedullary trajectory of 23 physiologically identified Ia afferents from cat hind limb muscles (medial gastrocnemius, soleus, plantaris, flexor digitorum‐hallucis longus, and hamstring). The afferents were stained by intra‐axonally injected HRP. The axons of these afferents were traced over distances of 5.8 mm to 15.7 mm rostrocaudally. In the dorsal funiculus fibers from all the muscles showed a similar course and similarly bifurcated into an ascending and a descending branch. The mean diameters of stem axons, ascending branches, and descending branches were 6.6 μm, 5.8 μm, and 3.0 μm, respectively. Within the analyzed lengths of the spinal cord five to eleven collaterals were given off from the two branches. The distances between adjacent collaterals of the ascending and descending branches averaged 1200 μm and 790 μm, respectively.

The collaterals as a rule passed through the medial half of the dorsal horn before they entered the deeper parts of the gray matter. The terminal distribution areas common to all Ia collaterals were: (1) the medial half of the base of the dorsal horn, mainly lamina VI; (2) lamina VII; and (3) lamina IX. The numbers of terminals were largest in lamina IX and smallest in lamina VII. The density of terminals in lamina IX was highest in the homonymous motor cell column. The terminal distribution areas of adjacent collaterals showed no overlap in the sagittal plane. Terminal branches carried one bouton terminal and up to six boutons en passage with an average of 1.8 terminals per terminal branch. Apparent axosomatic and axodendritic contacts were seen on small‐sized and medium‐sized neurons in laminae V–VI, medium‐sized neurons in lamina VII, and large neurons in lamina IX. One motoneuron was contacted by an average of 3.3 terminals.

In addition to the common features, Ia collaterals of various muscles of origin showed some differences in their trajectories in the ventral horn, and in their terminations in the gray matter.
Alpha‐ and gamma‐motoneurons in the adult human spinal cord and somatic cranial nerve nuclei: The significance of dendroarchitectonics studied by the Golgi method
Authors: Abdel‐Maguid Thoraya E. , Bowsher David
Published: January 2005

A modified Golgi method (Vaisamruat and Hess, '53) was found to give satisfactory impregnation of cell bodies and dendrites, but not of dendritic spines and axons, in adult human material fixed by immersion in formalin. Examination of the motor columns in the spinal cord intumescences and of the third and twelfth cranial nerve nuclei revealed four neuron types, based on dendritic field size and dendritic branching pattern. Two of these were recognized as alpha‐motoneurons; one of them was seen only in the medial motor column of the spinal ventral horn, while the other was observed in the cranial motor nuclei as well as the spinal lateral motor column. Differences in somadendritic dimensions in this neuron type were thought to reflect motor unit size, and thus terminal axon field dimensions. Of the two types of gamma‐motoneurons recognized in the spinal cord and oculomotor nucleus, one was a miniature version of the commoner type of alpha‐motoneuron. On this basis, it is proposed that it may give rise to fusimotor axons with plate endings. The second type of gamma‐motoneuron does not resemble any of the other motoneuron types, and its axons may therefore be thought to terminate in trail endings.
Cerebellar corticonuclear fibers of the dorsal culminate lobule (anterior lobe—lobule V) in a prosimian primate, Galago senegalensis
Authors: Haines D. E. , Rubertone J. A.
Published: January 2005

The organization of corticonuclear fibers from lobule V of the anterior lobe of the lesser bushbaby, Galago senegalensis, was studied utilizing the Fink and Heimer ('67) method. Corticonuclear fibers of lobule V are ipsilateral, topographically arranged in their trajectory into the deep cerebellar nuclei and organized into six identifiable zones. No evidence is seen to support the contention that these fibers may project diffusely into the cerebellar nuclei, either in a rostro‐caudal or medio‐lateral sequence, or that they may project to any of the contralateral nuclei.

Lesions in lateral lobule V cortex produce degeneration in rostroventral magnocellular NL. No debris is seen in parvicellular NL and no degenerated axons enter the NIA, NIP or NM. The terminal field in the NL is roughly pyramid shaped with the base being located at the periphery of the nucleus and the apex directed toward the hilus. Based on the totality of its efferent projections the intermediate cortex (IC) of lobule V is a relatively wide region which is divisible into three separate areas. Lateral portions of the IC project heavily into the lateral NIA and send a sparse number of fibers into the NIP. The middle area of the IC sends fibers almost exclusively to a bifid terminal field located in the NIP. From this area of cortex no degenerated fibers enter either the NL or NM and only extremely sparse amounts of debris are seen in rostrolateral NIA. Following damage to medial regions of IC degeneration is seen primarily in medial portions of the NIA and in the juxtarestiform body, if the lesion involves the lateral portions of the vermal cortex. These three regions of the IC, identified here based on the arrangement of their corticonuclear fibers, represent the cortical correlates of compartments C1, C2 and C3 (of Voogd, '69). Lesions involving the lateral aspect of the vermal cortex produce degeneration in the vestibular complex, primarily its lateral nucleus, and in the NIP. These observations may represent a subdivision of this area, a fact previously reported in the cat (Oscarsson and Sjölund, '77a). The medial portions of the vermal cortex project primarily to rostrodorsal NM.

The results of this study provide data concerning the arrangement of zones in the anterior lobe cortex of a primate. Due to the fact that differential projections into magnocellular versus parvicellular NL were not seen, the lateral cortex is designated only as zone D. The IC contains, from lateral to medial, zones C3, C2 and C1. The lateral edge of the vermal cortex is designated zone B, although it is recognized that subdivisions of this area may exist (Oscarsson and Sjölund, '77a) while zone A is the more medial area of vermal cortex. These zone designations represent those portions of cortex which overlie previously identified compartments (Voogd, '69) in the subcortical white matter.
A quantitative investigation of spine and dendrite development of neurons in visual cortex (area 17) of Macaca nemestrina monkeys
Authors: Boothe Ronald G. , Greenough William T. , Lund Jennifer S. , Wrege Kathy
Published: January 2005

In a previous Golgi study (Lund et al., '77) which examined the development of the macaque monkey striate cortex (area 17) it was observed that the dendrites of neurons within the visual cortex show a marked increase in the number of spines on their surface during the first eight weeks of postnatal life. The qualitative observation was also made that all neurons then showed a marked decrease in spine numbers by the time the animal was adult. Since these spines are known to be sites of synaptic contact, changes in their numbers may reflect changes in synapse populations on these neurons.

This study examines quantitatively spine frequency and total dendritic development of Golgi impregnated neurons in monkeys ranging in age from 145 days gestation to adult. Four cell types were studied: spiny stellate neurons from laminae IVCα and IVCβ and pyramidal neurons with soma in either lamina IIIB or upper lamina VI. After consideration of possible sources of variation in spine numbers several conclusions are made: (1) Dendritic spine development appears to be a tightly controlled process both in terms of actual numbers of spines on a neuron at any one age and in the rate of change of spine frequency. (2) The neurons populations examined all show a gradual increase in spine numbers up to eight weeks of age. (3) At least two different trends are found in spine population maturation after the eight week point: (A)‐the spine population may remain constant at the eight week level for same period of time or (B)‐there may be a rapid decline in spine numbers following the eight week peak. (4) There is a suggestion that those neurons associated with direct input, or early stages in the relays, from the parvocellular geniculate laminae show trend B, while those associated with magnocellular input, or later order combined relays within the cortex, show trend A. (5) Different parts of a single pyramidal neuron dendrite may show either trend A or trend B, depending on the lamina location of the dendritic segment considered. (6) All neurons show spine population decreases between nine months of age and adult (5–7 years) suggesting continuing long term maturational changes.
Origin and organization of brainstem catecholamine innervation in the rat
Authors: Levitt Pat , Moore Robert Y.
Published: January 2005

The catecholamine (CA) innervation of the rat brainstem was studied by biochemical analysis of discrete nuclei or areas and by glyoxylic acid‐formaldehyde freeze dry fluorescence histochemistry. CA assays demonstrate that the highest norepinephrine (NE) content in brainstem is present in the trigeminal motor nucleu, nucleus tractus solitarius, dorsal motor nucleus of the vagus and nucleus raphe dorsalis. Bilateral locus coeruleus (LC) lesions do not significantly alter NE content in these nuclei but do decrease NE content in the superior and inferior colliculi, medial geniculate body, interpeduncular nucleus, pontine nuclei and the main sensory trigeminal nucleus (60–75%). Dopamine (DA) and epinephrine (E) are found in significant concentration in only a few of the nuclei examined.

Fluorescence histochemical analysis indicates that two groups of NE axons innervate rat brainstem. LC neuron axons with a distinctive morphology principally innervate sensory and association nuclei of the brainstem. These disappear completely after bilateral LC lesions. The second group of axons originates from lateral and dorsal tegmental NE cell groups. Primary motor and visceral nuclei are densely innervated by fine and thick axons from these groups. Lesions of LC do not alter the NE innervation in any of the nuclei which contain axons of the second group.

These results indicate that the brainstem NE innervation is divided into two major systems. The locus coeruleus complex innervates mainly primary sensory and association nuclei whereas the lateral tegmental NE neurons innervate primary motor and visceral nuclei. Although some overlap is present, the LC and lateral tegmental NE system predominantly innervate separate and functionally distinct areas of the brainstem. DA and E neurons provide a very minor component of the brainstem CA innervation.
Terminal proliferation in the partially deafferented dentate gyrus: Time coureses for the appearance and removal of degeneration and the replacement of lost terminals
Authors: McWilliams Randall , Lynch Gary
Published: January 2005

The time courese for the appearance and removal of degenerating terminals and the loss and reappearance of intact terminals were investigated in the partially denervated inner molecular layer of the dentate gyrus of the adult rat. Dense degeneration was evident in the neuropil within 26 hours following contralateral hippocampectomy. These profiles increased rapidly in number until the maximal degree was reached at two to tree days postlesion, after which the degenerating terminals were quickly removed from the neuropil. A more rapid rate of removal occurred during the 3‐ to 5‐ day survival period than from 6 to 50 days postlesion.

The intact terminal population dropped by 35% within two days of the lesion and remained at this level until six to eight days postlesion when the number began to steadily increase. The time course for this reappearance cat be divided into two phases: a period of rapid terminal addition from 6 to 15 days followed by a phase of slower acquisition. This recovery continued until the normal synaptic density was regained by 50 to 65 days postlesion.

These results indicate that a substantial proportion of degenerating endings are removed well in advance of the time at which terminal proliferation begins, suggesting that certain changes other than merely the removal of competitive inputs must take place prior to the gowth of new terminals. Possible explanations suggested by the present results for the delay in the onset of sprouting in clude: (1) an absence of appropriate postsynaptic targes during the 2‐ to 5‐ day postlesion period and (2) inhibition of axonal growth by the glial cells which are phagocytizing the degenerating products.

Beyond the sixth postlesion day the rate at which new terminals appear does correlate with the rate at which degeneration is removed. This suggests that once underway the time course for sprouting may be determined by the availability of postsynaptic sites.
Afferent connections to the amygdaloid complex of the rat and cat. I. Projections from the thalamus
Authors: Ottersen Ole P. , Ben‐Ari Y.
Published: January 2005

By the use of the retrograde transport of horseradish peroxidase (HRP), the projections from the thalamus to the amygdala were investigated in the rat and cat, with main emphasis on the former species. HRP was injected stereotactically by microiontophoresis in the various amygdaloid nuclei. Several control procedures including the use of different approaches for the introduction of the micropipette were undertaken to eliminate the possibility of misinterpretation due to uptake of the protein by adjacent structures or fibers en passant.

The paraventricular and parataenial nuclei of the thalamus were found to project throughout the entire amygdaloid complex. The medial geniculate complex and the basal nucleus of the ventromedial complex (the thalamic taste relay) mainly project to the centromedial part of the amygdala. The basolateral nucleus is the main recipient of a hitherto undescribed bilateral thalamo‐amygdaloid pathway originating in the interanteromedial nucleus. The parafascicular nucleus projects to the central nucleus of the amygdala; in the cat mainly to the lateral subdivision of the central nucleus.

The findings are discussed in relation to previous anatomical and electrophysiological studies centered on the amygdaloid complex. Special reference is made to the possible role of the thalamo‐amygdaloid connections in the conveyance of sensory information to the amygdala.