摘要:

AbstractEfferents revealed by degeneration staining following tectal lesions in goldfish are presented. Four major projections were found.Ascending ipsilateral projections to pretectal‐diencephalic areas exit the tectum rostrally and laterally and terminate in the area pretectalis (AP), lateral geniculate (LGN), nucleus pretectalis (NP), and nucleus rotundus (NR). Ascending contralateral projections exit rostrally and possibly laterally, enter the posterior and postoptic commissures and terminate in the contralateral AP, LGN, NP, NR and rostral tectum. A medially directed projection enters the intertectal commissure, and some of these fibers may terminate sparsely in an area of the contralateral tectum homotopic to the lesion. A descending projection exits the tectum laterally and projects ipsilaterally to a dorsolateral tegmental nucleus (DLT) and the lateral reticular formation of the tegmentum and pons, and contralaterally to the medial reticular formation of the tegmentum and pon

ISSN:0092-7317    

DOI:10.1002/cne.901840302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe central distributions of primary afferent axons in cranial nerves V, VII, IX, and X have been re‐examined autoradiographically after3H‐proline injections into their peripheral ganglia. Fiber‐labeling after subtotal injections of the trigeminal ganglion, besides confirming earlier classical descriptions, suggests that trigeminal fibers of the ophthalmic and mandibular (but not maxillary) branches enter the ventrolateral part of the nucleus of the solitary tract (NST). Injection of VII's geniculate ganglion labels fibers which both ascend and descend upon reaching NST. The ascending fibers distribute in a compact and circumscribed zone immediately dorsal to the spinal V nucleus as far rostral as the caudal pole of the principal trigeminal nucleus. The descending fibers distribute to the lateral NST rostral to the level at which X joins the solitary tract. For a short distance caudal to this level, sparse label is confined to a small part of lateral NST ventral to the solitary tract, which corresponds to the zone receiving direct trigeminal afferents. Fiber‐labeling after injections of the ganglia of nerves IX and X suggest the following. Although, upon reaching NST, a few fibers of either IX or X ascend as far rostrally as had those of VII, both have a much larger descending component which distributes to more caudal levels of NST. Most of IX's axons appear to end in the lateral NST; only a few travel as far as the obex. Fibers of X, on the other hand, are abundant in the medial and commissural parts of NST. Moreover, only X appears to have a crossed projection in the commissural nucleus and caudal portion of the contralateral NST. A few fibers of vagal origin also appear to enter the area postrema. Whereas fibers of X appear to constitute the solitary tract, few if any fibers of VII or IX travel within that fascicle. A significant descending components of labeled fibers appears in the spinal V tract when the superior ganglion of either IX or X is injected. These fibers distribute mainly in the pars caudalis of the spinal V nucleus and, to a lesser degree, the cuneate

ISSN:0092-7317    

DOI:10.1002/cne.901840303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractMicroelectrode mapping methods were used to determine the organization of the second somatosensory representation, SmII, in grey squirrels. A systematic representation of the contralateral body surface was found in lateral parietal cortex adjoining the first somatosensory representation, SmI (Sur et al., '78a). The representation of the body in SmII was found to be much less distorted than in SmI. Under our recording conditions, almost all recording sites were activated from strictly contralateral body locations. The most important finding was that the basic orientation of the body representation in SmIi is “erect” rather than “inverted.” This orientation allows SmII and SmI to be adjoined along a common border representing the top of the head and face. This type of border has been called congruent (Allman and Kaas, '75; Kaas, '77), and it may have significance in the development of sensory represen

ISSN:0092-7317    

DOI:10.1002/cne.901840304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractSynaptogenesis in the cervical cord was studied by light and electron microscopy in human embryos ranging from four to seven weeks of ovulation age. The stage of embryonic development was estimated on the basis of external morphology of embryos and histology of the eye ball with reference to Streeter's horizon. No synapses were found in the cervical cord of the embryo at Streeter's horizon XIV (8 mm; estimated ovulation age, 28‐30 days). A small number of axodendritic synapses appear in the motor neuropil of the cervical cord at Streeter's horizon XVII (14 mm; estimated ovulation age, 34‐36 days). Since no primary afferents are demonstrated to reach the motor neuropil at this stage (the premotile period), these synapses are considered to be formed between interneurons and motor neurons. On the other hand, the formation of synapses outside the motor neuropil of the cervical cord was recognized at Streeter's horizon XX (22 mm; estimated ovulation age, 40‐42 days), which corresponded to the period of onset of the precocious reflex, but not by horizon XIX (18 mm; estimated ovulation age, 38‐40 days). The first axosomatic synapses were found in the motor neuropil at Streeter's horizon XVII (estimated ovulation age, 34‐36 days). The present study suggests that the formation of synapses between interneurons and dendrites of spinal motor neurons precedes that of synapses between interneurons and collaterals of primary afferents. This sequence of synaptogenesis is in agreement with that reported in earlier studies with silver stai

ISSN:0092-7317    

DOI:10.1002/cne.901840305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractWe have made a SEM study of the basal intercellular spaces of the retina in chick embryos of different developmental stages. Since this is the environment where optic axons grow, the structural characteristics of this region might play some role in the orientation of axonal migration towards the choroid fissure. The basal region of undifferentiated retinas is formed by the vitreal expansions of neuroepithelial cells. In pre‐axonal stages, the intercellular spaces between these expansions do not show any preferential orientation towards the fissure. The growth cones of ganglion cell axons appear in an apicobasal direction and turn towards the fissure immediately beneath the vitreal surface. Fasciculation is an early event during development and, in the more advanced stages, the vitreal expansions from retinal cells are placed in rows following the same orientation as the axon bundles. These observations are discussed in relationship to current hypotheses on axonal migration and orientatio

ISSN:0092-7317    

DOI:10.1002/cne.901840306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe sensory fibers of the facial nerve inLacerta viridishave been studied with a silver impregnation method to follow the course of axonal degeneration. Destruction of the geniculate ganglion demonstrated the degenerated sensory component of the facial nerve adjacent to the anterior vestibular root. Within the lateral vestibular area the facial sensory fibers consist of numerous rootlets separated by vestibular fibers and cells. These rootlets may join to form a main or paired sensory tract that passes through the vestibular nuclei to enter the tractus solitarius and divide into a small ascending prefacial component and a major descending prevagal division. A few fibers continue into the postvagal part of tractus solitarius and extend caudally to terminate in the nucleus commissura infima. Prefacial fibers terminate along the periventricular gray while prevagal fibers terminate within the tractus solitarius on the dendrites of cells of nucleus tractus solitarius and near the periphery of the dorsal motor nucleus of X. There was no noticeable degeneration in the descendens tractus trigemini. Terminal degeneration to descendens nucleus trigemini and motor nucleus of VII followed the tractus solitarius course. Most facial sensory fibers are probably related to taste and other visceral information.

ISSN:0092-7317    

DOI:10.1002/cne.901840307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractSome 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 corte

ISSN:0092-7317    

DOI:10.1002/cne.901840308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractProjections from the spinal (Vsp) and the principal sensory (Vp) nuclei of the trigeminal nerve to the cerebellar cortex were studied by means of retrograde transport of horseradish peroxidase in the cat.Neurons projecting to the simple lobule and the dorsal part of the paramedian lobule (PMD) were located mainly in the dorsal part of the nucleus interpolaris (Vi) and of the caudal one third of the nucleus oralis (Vo) and in the rostralmost part of the Vo. Neurons projecting to the medial part of the posterior folia of crus II (crus IIp) were located in the dorsal to ventral parts of the Vi and of the caudal one third of the Vo and in the rostralmost part of the Vo, while those projecting to the lateral part of crus IIp were confined to the ventral part of the Vi and of the caudal one third of the Vo. Neurons of the Vp also projected to all of these cortical areas. They were relatively confined to the ventral part of this nucleus. These trigeminocerebellar projections were exclusively ipsilateral to the cell origin. There were sparse projections from the Vi and Vo to lobules V to VIIIa. In addition, a small group of neurons in the subnucleus magnocellularis of the nucleus caudalis of the Vsp also projected to the above cortical areas. No projections were, however, observed to the anterior portion of the anterior lobe, crus I, the anterior folia of crus II, paraflocculus, flocculus and the ventral part of the PMD. The majority of these cerebellar pojection neurons were medium‐sized and triangular, fusiform or ovoid in shape. There were small neurons of similar types and large multipolar neurons as wel

ISSN:0092-7317    

DOI:10.1002/cne.901840309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractMore than two‐thirds of the axons in the tract of Lissauer at mid‐thoracic and lumbosacral levels of the rat spinal cord are primary afferent fibers. The proportions of primary afferents in the tract are approximately the same at the two spinal levels. A slightly higher percentage of the unmyelinated, as opposed to the myelinated, fibers are primary afferents. There is a somewhat greater percentage of primary afferent axons in medial parts of the tract in mid‐thoracic levels, but all areas of the tract that were examined contain a majority of primary afferent fibers. The primary afferent axons appear to travel less than a segment in the tract at mid‐thoracic levels but for several segments in the tract at lumbo‐sacral levels. These data indicate that the tract of Lissauer is predominately a primary afferent fiber system in these segments o

ISSN:0092-7317    

DOI:10.1002/cne.901840310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901840301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY