摘要:

AbstractThe central visual pathways of the rat have been used as a model for investigating the significance of axonal interactions in mammalian neural development. Attention is restricted largely to the aberrant distribution of optic axons to the ipsilateral side of the brain and their distribution in the superior colliculus after early unilateral eye damage.The normal ipsilateral retinotectal pathway in pigmented rats appears as a series of patches located anteriorly and laterally in the stratum opticum, whereas in albino animals it is a small area lying anteromedially. In both, a few axons are often found at the extreme posterior border of the superior colliculus.After unilateral eye enucleation at birth, an aberrant ipsilateral pathway from the remaining eye arises at the optic chiasm. It originates from all parts of the retina and terminates in the ipsilateral superior colliculus in a topographic fashion such that the upper retina projects laterally and the lower retina, medially. The pathway is heaviest anteromedially (from lower temporal retina) and lightest posterolaterally (from upper nasal retina). There is always a heavy projection to the extreme posterior border of the superior colliculus. In only two animals of a large series was direct intertectal sprouting found.After partial retinal lesions, there is again an ipsilateral pathway from the unlesioned eye which fills the projection area of the lesion. As after total enucleation, the pathway arises from most of the ipsilateral retina, not just that region homotypic to the lesion site, being heaviest from the lower temporal and lightest (or deficient) from the upper retina. There is suggestion of ordering of the projection into the deafferented region in that the ipsilateral degeneration after lesions in the intact eye is compact but does not fill the gap in the crossed projection completely. There is also indication that some intact parts of the retina lesioned at birth may also project in an inappropriate retinotopic fashion to the deafferented region. The corticotectal pathway shows a normal map. Study of the ipsilateral retinotectal pathway indicates that the axons terminating at the extreme posterior border of the superior colliculus arise from the lower temporal retina.The results are interpreted as indicating that the aberrant uncrossed pathways after complete or local retinal lesions, compare very closely in most features. Both distribute to the deafferented area of the superior colliculus – in one, this is the whole surface, while in the other it is a small area. The fact that in the latter case axons are ending in quite inappropriate parts of the tectal map, may be explained more simply in terms of interactions between adjacent axons in the optic pathway rather than by an hypothesis involving a change in the cell labels across the tectal ma

ISSN:0092-7317    

DOI:10.1002/cne.901690202

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

年代:1976

数据来源: WILEY

摘要:

AbstractAn electron microscopic examination of two cat optic nerves indicates a mean total count of 193,000 fibres ranging from 0.5μ to 13.5μin diameter. This count, although nearly double any previously reported, supports recent minimum estimates of the retinal ganglion cell population of the cat eye. A radial gradient of packing density exists across the nerve close to the globe; a high density “core” with a unimodal fibre diameter spectrum may be identified as the area centralis outflow and a peripheral low density region with a trimodal diameter spectrum contains the projection of the peripheral retina. Division of the peripheral fibre spectrum suggests the percentages of α,βandγ ganglion cells in the peripheral retina to be 5%, 42% and 53% resp

ISSN:0092-7317    

DOI:10.1002/cne.901690204

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

年代:1976

数据来源: WILEY

摘要:

AbstractEfferent projections from the medial and periventricular preoptic area, bed nucleus of the stria terminalis and nuclei of the diagonal band were traced using tritiated amino acid autoradiography in albino rats.Medial and periventricular preoptic area efferents were not restricted to shortaxon projections. Ascending projections from the medial preoptic area (mPOA) were traced through the diagonal band into the septum. Descending mPOA axons coursed in the medial parts of the medial forebrain bundle. Projections to most hypothalamic nuclei, including the arcuate nucleus and median eminence, were observed. In the midbrain, mPOA efferents were distributed in the central grey, raphe nuclei, ventral tegmental area and reticular formation. Projections from the mPOA were also observed to the amygdala through the stria terminalis, to the lateral habenula through the stria medullaris, and to the periventricular thalamus.Axons of the most medial and periventricular preoptic area (pvPOA) neurons had a distribution similar to more lateral mPOA neurons but their longest‐axoned projections were weaker. The pvPOA did not send axons through the stria medullaris but did project more heavily than the more lateral mPOA to the arcuate nucleus and median eminence.Projections from the bed nucleus of the stria terminalis (nST) were in most respects similar to those from the medial preoptic area, with the major addition of a projection to the accessory olfactory bulb.The nuclei of the diagonal band of Broca (nDBB) gave a different pattern of projections than mPOA or nST, projecting, for instance, to the medial septum and hippocampus. Descending nDBB efferents ran in the ventral portion of the medial forebrain bundle. Among hypothalamic cell groups, only the medial mammillary nuclei received nDBB projections. nDBB efferents also distributed in the medial and lateral habenular nuclei and the mediodorsal thalamic nucleu

ISSN:0092-7317    

DOI:10.1002/cne.901690205

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

年代:1976

数据来源: WILEY

摘要:

AbstractUsing tritiated amino acid autoradiography, the efferent projections of the anterior hypothalamic area (AHA) were studied in albino rats.Axons from AHA neurons were not confined to local projections in the hypothalamus. Ascending AHA axons ran through the preoptic region, joined the diagonal band and distributed in the lateral septum. Descending AHA efferents within the hypothalamus coursed in a bundle ventromedial to the fornix. Projections were observed to the dorsomedial, ventromedial, arcuate and dorsal premammillary nuclei, and to the median eminence. Sweeping dorsomedially in the posterior hypothalamus, some AHA axons distributed in the central grey. AHA axons staying ventral projected to the supramammillary region, ventral tegmental area, raphe nuclei and midbrain reticular formation. Other AHA efferents distributed to the periventricular thalamus, to the medial amygdala via the stria terminalis or supraoptic commissure, and to the lateral habenula through the stria medullaris.For comparison with the AHA, efferent projections from the paraventricular nucleus (PVN) and from the ventromedial nucleus and adjacent basal hypothalamus (VMR) were studied. Projections from PVN neurons were not restricted to the median eminence and neurohypophysis. PVN efferents also distributed to many of the same regions as did those of the AHA but had somewhat different fiber trajectories and longer descending projections. VMR efferents were more widespread than those of the AHA, with projections extending into the lateral zona incerta and pontine reticular formation.Projections from the AHA were distinct from those of the medial preoptic area (mPOA). For example, while AHA axons descended in a bundle ventromedial to the fornix, mPOA axons ran in the medial forebrain bundle. Such anatomical differences may underlie experimentally demonstrated functional differences between the mPOA and AHA, for instance, in mediation of male and female sex behaviors.

ISSN:0092-7317    

DOI:10.1002/cne.901690206

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

年代:1976

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901690201

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

年代:1976

数据来源: WILEY