摘要:

Cytoarchitectural analyses combined with injections of the tracer horseradish peroxidase in various structures in the brain of the goldfish, Carassius auratus, have defined some of the major components of acoustic and lateral line mechanosensory circuits between the medulla and midbrain. The main acoustic receptor in Carassius, the saccule, is known to provide a major input to the dorsomedial zone of the descending octaval nucleus. The dorsomedial zone in turn projects bilaterally to the secondary octaval population (SO) and to nucleus centralis of the torus semicircularis. The SO is composed of three major subdivisions which are also present in a related otophysan, the catfish Ictalurus punctatus. The SO in Carassius projects bilaterally to nucleus centralis and to the saccular recipient zones of the ipsilateral descending octaval nucleus. By contrast, the mechanosensory lateral line receptors are known to direct most of their input to nucleus medialis. Nucleus medialis in turn projects bilaterally to nucleus praeeminentialis, nucleus ventrolateralis of the torus semicircularis, and the optic tectum, and to the contralateral nucleus medialis. We also provide evidence for a bilateral projection of nucleus medialis to the sensory trigeminal nucleus, and for a reciprocal input from the sensory trigeminal nucleus to the ipsilateral nucleus medialis.

ISSN:0006-8977    

DOI:10.1159/000113232

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Cytoarchitectural analyses combined with injections of the tracer horseradish peroxidase in various structures in the brain of the goldfish, Carassius auratus, have defined some of the major components of acoustic and lateral line mechanosensory circuits between the medulla and midbrain. The main acoustic receptor in Carassius, the saccule, is known to provide a major input to the dorsomedial zone of the descending octaval nucleus. The dorsomedial zone in turn projects bilaterally to the secondary octaval population (SO) and to nucleus centralis of the torus semicircularis. The SO is composed of three major subdivisions which are also present in a related otophysan, the catfish Ictalurus punctatus. The SO in Carassius projects bilaterally to nucleus centralis and to the saccular recipient zones of the ipsilateral descending octaval nucleus. By contrast, the mechanosensory lateral line receptors are known to direct most of their input to nucleus medialis. Nucleus medialis in turn projects bilaterally to nucleus praeeminentialis, nucleus ventrolateralis of the torus semicircularis, and the optic tectum, and to the contralateral nucleus medialis. We also provide evidence for a bilateral projection of nucleus medialis to the sensory trigeminal nucleus, and for a reciprocal input from the sensory trigeminal nucleus to the ipsilateral nucleus medialis.

ISSN:0006-8977    

DOI:10.1159/000316274

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Interconnections between the dorsal column nucleus and the spinal cord were investigated in a reptile, Caiman crocodilus. After placement of an anterograde tracer into the dorsal column nucleus, descending fibers are seen to leave this nucleus to enter the dorsal funiculus where they course ventrally to terminate in lamina V of the spinal cord as far caudally as C2. Placement of a retrograde tracer into cut fibers of the cervical spinal cord identified the relay cells of the dorsal column nucleus that project to the spinal cord. These neurons were mainly clustered in a caudal and ventral part of this nucleus. The soma of these spinally projecting cells were small and were generally round or oval in shape. A number of these neurons had the long axis of their soma oriented dorsoventrally, with a primary dendrite extending dorsally. Fibers in the dorsal funiculus that originated from the spinal cord enter the caudal part of the dorsal column nucleus and turn ventral. In the dorsal column nucleus, these axons run parallel to the vertically oriented dendrites of these spinally projecting cells before termination in close relation to the cell bodies of these neurons. Quantitative observations (mean ± standard error) were made on well labeled neurons and included several measurements: area, perimeter, and degree of eccentricity (greatest width/greatest length) in both the transverse as well as the sagittal plane. These spinally projecting neurons in Caiman are located in the dorsal column nucleus in a position similar to that of spinally projecting cells in cats

ISSN:0006-8977    

DOI:10.1159/000113233

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Injections of horseradish peroxidase, or the carbocyanine dye Dil, into the central prosencephalic nucleus of hagfishes reveal reciprocal connections with the septum, preoptic area, habenula, thalamus and hypothalamus. Efferent projections also occur to the olfactory bulb, pallium, posterior tubercle and tegmentum and to the contralateral central prosencephalic nucleus. These connections suggest that the central prosencephalic nucleus of hagfishes may be homologous to portions of the medial pallium and ventral thalamus of other craniates.

ISSN:0006-8977    

DOI:10.1159/000113234

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

The hippocampal complex (hippocampus and parahippocampalis) is known to play a role in spatial memory in birds and is known to be larger in food-storing versus non-storing birds. In the present study, we investigated the relative volume of the hippocampal complex in four food-storing corvids: gray-breasted jays (Aphelocoma ultramarina), scrub jays (Aphelocoma coerulescens), pinyon jays (Gymnorhinus cyanocephalus), and Clark's nutcrackers (Nucifraga columbiana). The results show that Clark's nutcrackers have a larger hippocampal complex, relative to both body and total brain size, than the other three species. Clark's nutcrackers rely more extensively on stored food in the wild than the other three species. Clark's nutcrackers also perform better during cache recovery and operant tests of spatial memory than scrub jays. Thus, greater hippocampal volume is associated with better performance in laboratory tests of spatial memory and with stronger dependence on food stores in the wild.

ISSN:0006-8977    

DOI:10.1159/000113235

出版商:S. Karger AG    

年代:1996

数据来源: Karger