摘要:

Cytoarchitectural analysis of the octavolateralis area of the goldfish, Carassius auratus, reveals that as in other teleosts, five first-order octaval nuclei are present: the anterior octaval, magnocellular, descending, tangential, and posterior octaval nuclei. The descending nucleus appears to be anatomically specialized relative to that of the halecomorph Amia calva and many teleosts in that a large dorsomedial subpopulation of the nucleus lies medial to nucleus medialis, a first-order lateral line nucleus. In addition to this dorsomedial zone, the descending nucleus is made up of an intermediate and a ventral zone.Application of horseradish peroxidase (HRP) to individual inner ear endorgans reveals that the distribution of these afferents to the octaval nuclei is generally similar to that in another otophysan, Ictalurus punctatus [McCormick and Braford, 1993]. Nucleus magnocellularis receives a diffuse projection from all of the endorgans. The semicircular canals project heavily to the nucleus tangentialis, the entire ventral zone and portions of the intermediate zone of the descending nucleus, the ventral portion of the caudal anterior nucleus, and the bulk of the rostral anterior nucleus. The macula neglecta projects to the intermediate zone of the descending nucleus and to ventral locations within the dorsal half of the caudal anterior nucleus. The otolithic endorgans - the saccule, lagena, and utricle - project, in an overlapping manner, to the dorsal half of the caudal anterior nucleus and minimally to the rostral anterior nucleus. The inputs of the otolithic endorgans to the intermediate zone of the descending nucleus are more segregated, though a given region is sometimes supplied by more than one endorgan. The projections of the saccule tend to be concentrated more medially than those of the other two endorgans. The dorsomedial zone of the descending nucleus receives the majority of its primary input from the saccule, and a much smaller input from the lagena, over most of its rostrocaudal extent. At caudal-most levels of the dorsomedial zone, afferents from the three otolithic endorgans overlap.

ISSN:0006-8977    

DOI:10.1159/000113634

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The piriform cortex in homing pigeons receives a projection from the olfactory bulb and is necessary for the operation of those aspects of the navigational map based on olfactory stimuli in these animals. The afferent and efferent projections of the piriform cortex were studied using retrograde migration of wheat-germ agglutinin horseradish peroxidase (WGA-HRP) and Fast Blue, and anterograde migration of WGA-HRP. The piriform cortex was found to receive projections from, and send projections to, numerous regions and nuclei in the telencephalon, diencephalon and lower brainstem. A reciprocal connection with the parahippocampal region suggests that the piriform cortex and hippocampal formation may be part of a neural system that regulates navigational map learning. The piriform cortex also connects reciprocally with a large portion of the anterior telencephalon, including the cortex prepiriformis and hyperstriatum dorsale. In general, the pathway connections of the piriform cortex in homing pigeons are similar to those of the piriform cortex in mammals.

ISSN:0006-8977    

DOI:10.1159/000113635

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Color vision in rainbow trout was studied by characterizing the spectral sensitivity of single units in three areas of visual processing: optic nerve; optic tectum; and torus semicircularis. Sensitivity to medium wavelength stimuli was a common feature of all single units examined. Additionally, long wavelength sensitivity was found in all units that were not medium wavelength-only or monophasic. Ultraviolet and short-wavelength sensitivity was common in small, juvenile trout, with ultraviolet sensitive units found in the optic nerve and torus, and short wavelength sensitivity found in the optic nerve and tectum. The shorter wavelength inputs were excitatory and, if found in the same unit, synergistic. The most common type of unit in the trout tectum and optic nerve is trichromatic, with ON inputs from the long and short cone mechanisms and an OFF input from the medium mechanism. In contrast, goldfish color vision is dominated by L and M opponent units without S input. The segregation of ultraviolet sensitivity in the torus but not in the tectum relates to functional differences of these two areas. While the tectum serves the function of wavelength discrimination, ultraviolet inputs to the torus may contribute to prey detection and orientation.

ISSN:0006-8977    

DOI:10.1159/000113636

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The presence of a postsynaptic dorsal column system was investigated in reptiles, Caiman crocodilus. Several experiments were undertaken. First, a cytoarchitectonic analysis of the spinal cord was performed to identify its laminar organization. Second, the termination of dorsal root fibers in the dorsal horn of the upper cervical cord, brachial enlargement, and lumbar intumescence was studied utilizing anterograde tracing techniques. Third, placement of retrograde tracers into the dorsal column nucleus identified spinal cord neurons that projected to the dorsal column nucleus. These experiments document that, in addition to direct primary dorsal root input, a second pathway exists whereby non-facial somatosensory information can reach the dorsal column nucleus in this reptilian group. This neural path arises primarily from neurons in the ipsilateral lamina V and, to a much lesser extent, from lamina IV in the cervical area and, to a far smaller degree, from the thoracic and lumbar dorsal horn. Each of these laminae whose neurons project to the dorsal column nucleus receive direct dorsal root input. This neural circuit in Caiman is similar to a neural pathway described in pigeons and several mammalian groups. These observations suggest that a postsynaptic dorsal column system is phylogenetically ancient and may well be a feature common to all amniotes.

ISSN:0006-8977    

DOI:10.1159/000113637

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The development of a number of sensorimotor reflexes was studied in the Brazilian opossum Monodelphis domestica. At birth, an opossum's forelimbs execute rhythmic, alternate movements which resemble swimming, whereas the hindlimbs are little more than embryonic buds that do not move independent of the trunk. It is possible, therefore, to witness the entire development of hindlimb motility, the advent of coordination between forelimbs and hindlimbs, and the development of ambulation. The following sequence in the appearance and maturation of the reflexes was observed: rooting, an innate reflex in mammals which disappears over time; withdrawal of the forelimbs followed by withdrawal of the hindlimbs; crossed extension of the forelimbs and then of the hindlimbs; grasp, the forelimbs preceding the hindlimbs; body righting on a surface; forward hopping of the forelimbs followed by the hindlimbs; lateral and medial hopping of the forelimbs, then the hindlimbs; chin tactile placing; body righting in the air, and, finally, visual placing. Limb tactile placing is not significantly expressed, even in the adult. This behavioral sequence generally matches the sequence of somatic (trunk, limbs, head) and neural (spinal cord and brain) structures involved in the control of these behaviors.

ISSN:0006-8977    

DOI:10.1159/000113638

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The major outputs of the tectum appear fundamentally similar in all vertebrate species, suggesting that the major types of tectal output neurons have been evolutionarily conserved across a wide variety of vertebrate species. Nonetheless, tectal lamination patterns vary dramatically among vertebrates. To explore the basis of this variation in lamination at a neuronal level, the laminar distribution of the cells of origin of the major ascending and descending tectofugal pathways was determined in turtles using retrograde HRP labeling and the results compared to those from similar studies in diverse other species. Four major tectal outputs were studied: 1) the ipsilateral ascending projection to nucleus rotundus of thalamus; 2) the ipsilateral ascending projection to the dorsal and ventral lateral geniculate nuclei of the thalamus; 3) the crossed descending projection to paramedian regions of the pons and medulla; and 4) the ipsilateral descending projection to cell groups of the ventrolateral pons and medulla. The projection to nucleus rotundus was found to arise exclusively from multipolar neurons of the stratum griseum centrale, while the projection to the geniculate nuclei was found to arise from radial cells with long ascending dendrites in the stratum griseum periventriculare. The crossed descending projection to the paramedian hindbrain was found to arise almost exclusively from large multipolar neurons, the majority of which were located in the stratum griseum centrale and some of which were located in the stratum griseum periventriculare. This pathway was also found to give rise to a collateral projection that ascends in the ipsilateral hypothalamus. The ipsilateral descending projection was found to arise from multipolar neurons in the stratum griseum centrale and stratum griseum periventriculare, from radial and pyramidal neurons in the stratum griseum periventriculare, and from radial neurons in stratum griseum et fibrosum superficiale. These results show that the laminar distribution of the cells of origin of tectofugal pathways in turtles does not fit the simple notion that the midbrain roof is organized into superficial layers containing neurons with ascending projections and deep layers containing neurons with descending projections. Rather, individual layers in turtles appear to give rise to both ascending and descending projections, with there being evidence that each projection arises largely from a separate set of neurons. The pattern of distribution of the cells of origin of these various pathways is different in turtles than in either birds, mammals, frogs, salamanders or teleosts. Such results suggest that considerable interspecific variation occurs in the extent to which individual homologous neuronal populations migrate superficially during tectal development.

ISSN:0006-8977    

DOI:10.1159/000113639

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The major outputs of the tectum appear fundamentally similar in all vertebrate species, suggesting that the major types of tectal output neurons have been evolutionarily conserved across a wide variety of vertebrate species. Nonetheless, tectal lamination patterns vary dramatically among vertebrates. To explore the basis of this variation in lamination at a neuronal level, the laminar distribution of the cells of origin of the major ascending and descending tectofugal pathways was determined in turtles using retrograde HRP labeling and the results compared to those from similar studies in diverse other species. Four major tectal outputs were studied: 1) the ipsilateral ascending projection to nucleus rotundus of thalamus; 2) the ipsilateral ascending projection to the dorsal and ventral lateral geniculate nuclei of the thalamus; 3) the crossed descending projection to paramedian regions of the pons and medulla; and 4) the ipsilateral descending projection to cell groups of the ventrolateral pons and medulla. The projection to nucleus rotundus was found to arise exclusively from multipolar neurons of the stratum griseum centrale, while the projection to the geniculate nuclei was found to arise from radial cells with long ascending dendrites in the stratum griseum periventriculare. The crossed descending projection to the paramedian hindbrain was found to arise almost exclusively from large multipolar neurons, the majority of which were located in the stratum griseum centrale and some of which were located in the stratum griseum periventriculare. This pathway was also found to give rise to a collateral projection that ascends in the ipsilateral hypothalamus. The ipsilateral descending projection was found to arise from multipolar neurons in the stratum griseum centrale and stratum griseum periventriculare, from radial and pyramidal neurons in the stratum griseum periventriculare, and from radial neurons in stratum griseum et fibrosum superficiale. These results show that the laminar distribution of the cells of origin of tectofugal pathways in turtles does not fit the simple notion that the midbrain roof is organized into superficial layers containing neurons with ascending projections and deep layers containing neurons with descending projections. Rather, individual layers in turtles appear to give rise to both ascending and descending projections, with there being evidence that each projection arises largely from a separate set of neurons. The pattern of distribution of the cells of origin of these various pathways is different in turtles than in either birds, mammals, frogs, salamanders or teleosts. Such results suggest that considerable interspecific variation occurs in the extent to which individual homologous neuronal populations migrate superficially during tectal development.

ISSN:0006-8977    

DOI:10.1159/000316228

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The major outputs of the tectum appear fundamentally similar in all vertebrate species, suggesting that the major types of tectal output neurons have been evolutionarily conserved across a wide variety of vertebrate species. Nonetheless, tectal lamination patterns vary dramatically among vertebrates. To explore the basis of this variation in lamination at a neuronal level, the laminar distribution of the cells of origin of the major ascending and descending tectofugal pathways was determined in turtles using retrograde HRP labeling and the results compared to those from similar studies in diverse other species. Four major tectal outputs were studied: 1) the ipsilateral ascending projection to nucleus rotundus of thalamus; 2) the ipsilateral ascending projection to the dorsal and ventral lateral geniculate nuclei of the thalamus; 3) the crossed descending projection to paramedian regions of the pons and medulla; and 4) the ipsilateral descending projection to cell groups of the ventrolateral pons and medulla. The projection to nucleus rotundus was found to arise exclusively from multipolar neurons of the stratum griseum centrale, while the projection to the geniculate nuclei was found to arise from radial cells with long ascending dendrites in the stratum griseum periventriculare. The crossed descending projection to the paramedian hindbrain was found to arise almost exclusively from large multipolar neurons, the majority of which were located in the stratum griseum centrale and some of which were located in the stratum griseum periventriculare. This pathway was also found to give rise to a collateral projection that ascends in the ipsilateral hypothalamus. The ipsilateral descending projection was found to arise from multipolar neurons in the stratum griseum centrale and stratum griseum periventriculare, from radial and pyramidal neurons in the stratum griseum periventriculare, and from radial neurons in stratum griseum et fibrosum superficiale. These results show that the laminar distribution of the cells of origin of tectofugal pathways in turtles does not fit the simple notion that the midbrain roof is organized into superficial layers containing neurons with ascending projections and deep layers containing neurons with descending projections. Rather, individual layers in turtles appear to give rise to both ascending and descending projections, with there being evidence that each projection arises largely from a separate set of neurons. The pattern of distribution of the cells of origin of these various pathways is different in turtles than in either birds, mammals, frogs, salamanders or teleosts. Such results suggest that considerable interspecific variation occurs in the extent to which individual homologous neuronal populations migrate superficially during tectal development.

ISSN:0006-8977    

DOI:10.1159/000113640

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The major outputs of the tectum appear fundamentally similar in all vertebrate species, suggesting that the major types of tectal output neurons have been evolutionarily conserved across a wide variety of vertebrate species. Nonetheless, tectal lamination patterns vary dramatically among vertebrates. To explore the basis of this variation in lamination at a neuronal level, the laminar distribution of the cells of origin of the major ascending and descending tectofugal pathways was determined in turtles using retrograde HRP labeling and the results compared to those from similar studies in diverse other species. Four major tectal outputs were studied: 1) the ipsilateral ascending projection to nucleus rotundus of thalamus; 2) the ipsilateral ascending projection to the dorsal and ventral lateral geniculate nuclei of the thalamus; 3) the crossed descending projection to paramedian regions of the pons and medulla; and 4) the ipsilateral descending projection to cell groups of the ventrolateral pons and medulla. The projection to nucleus rotundus was found to arise exclusively from multipolar neurons of the stratum griseum centrale, while the projection to the geniculate nuclei was found to arise from radial cells with long ascending dendrites in the stratum griseum periventriculare. The crossed descending projection to the paramedian hindbrain was found to arise almost exclusively from large multipolar neurons, the majority of which were located in the stratum griseum centrale and some of which were located in the stratum griseum periventriculare. This pathway was also found to give rise to a collateral projection that ascends in the ipsilateral hypothalamus. The ipsilateral descending projection was found to arise from multipolar neurons in the stratum griseum centrale and stratum griseum periventriculare, from radial and pyramidal neurons in the stratum griseum periventriculare, and from radial neurons in stratum griseum et fibrosum superficiale. These results show that the laminar distribution of the cells of origin of tectofugal pathways in turtles does not fit the simple notion that the midbrain roof is organized into superficial layers containing neurons with ascending projections and deep layers containing neurons with descending projections. Rather, individual layers in turtles appear to give rise to both ascending and descending projections, with there being evidence that each projection arises largely from a separate set of neurons. The pattern of distribution of the cells of origin of these various pathways is different in turtles than in either birds, mammals, frogs, salamanders or teleosts. Such results suggest that considerable interspecific variation occurs in the extent to which individual homologous neuronal populations migrate superficially during tectal development.

ISSN:0006-8977    

DOI:10.1159/000316229

出版商:S. Karger AG    

年代:1994

数据来源: Karger