摘要:

The cytoarchitecture of nuclei in the diencephalon and the distribution of acetylcholinesterase (AChE) in the diencephalon and optic tectum were analyzed in the longnose gar, Lepisosteus osseus, a non-teleost actinopterygian fish. Nuclei were identified in the preoptic area, thalamus, posterior tubercle, hypothalamus, synencephalon, and pretectum which are homologous to like-named nuclei in teleosts and other non-teleost actinopterygians. Of particular note, a nucleus in the rostral diencephalon, nucleus rostrolateralis, which has previously been identified only in the osteoglossomorph Pantodon, is present in the longnose gar. The posterior pretectal nucleus, previously identified in teleosts and in the bowfin Amia, is also present in gars. The small size of the posterior pretectal nucleus in gars supports the hypothesis that this nucleus was small plesiomorphically. The distribution of AChE in the diencephalon and optic tectum corresponds in most respects to that found in teleosts. The superficial pretectal nuclei, including the posterior pretectal nucleus, are strongly positive for AChE. In contrast, most of the nuclei within the preglomerular complex are negative for AChE. Acetylcholinesterase is present in some of the fibers in the optic tracts and in most retinorecipient nuclei, as well as in some other nuclei and tracts.

ISSN:0006-8977    

DOI:10.1159/000113824

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The cytoarchitecture of nuclei in the diencephalon and the distribution of acetylcholinesterase (AChE) in the diencephalon and optic tectum were analyzed in the longnose gar, Lepisosteus osseus, a non-teleost actinopterygian fish. Nuclei were identified in the preoptic area, thalamus, posterior tubercle, hypothalamus, synencephalon, and pretectum which are homologous to like-named nuclei in teleosts and other non-teleost actinopterygians. Of particular note, a nucleus in the rostral diencephalon, nucleus rostrolateralis, which has previously been identified only in the osteoglossomorph Pantodon, is present in the longnose gar. The posterior pretectal nucleus, previously identified in teleosts and in the bowfin Amia, is also present in gars. The small size of the posterior pretectal nucleus in gars supports the hypothesis that this nucleus was small plesiomorphically. The distribution of AChE in the diencephalon and optic tectum corresponds in most respects to that found in teleosts. The superficial pretectal nuclei, including the posterior pretectal nucleus, are strongly positive for AChE. In contrast, most of the nuclei within the preglomerular complex are negative for AChE. Acetylcholinesterase is present in some of the fibers in the optic tracts and in most retinorecipient nuclei, as well as in some other nuclei and tracts.

ISSN:0006-8977    

DOI:10.1159/000316112

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The distribution of neuronal types in the six layers of the optic tectum of the small-spotted dogfish, Scyliorhinus canicula, was studied using Golgi methods. The eight types of neurons have a variable distribution, some of them represented in all six tectal layers. Most neurons of the optic tectum have a radial orientation, and a small portion are disposed horizontally. The relative ratios of the different neuronal types in the six layers indicate that about 80% of the tectal neurons are intermingled with the optic nerve axon terminals in the superficial layers of the tectum. These results corroborate previous reports that the tectum of this selachian species is more specialized than formerly supposed, in spite of the differences in degree of neuropil lamination with other non-mammalian vertebrates.

ISSN:0006-8977    

DOI:10.1159/000113825

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Do more complex brains operate on the same principles as simpler brains, merely employing more of the same; or has evolution produced new principles? A neglected research agenda is the search for relevant differences between brains of animals belonging to different major grades of complexity and cognitive capacity. More complex brains are believed to be capable of more transactions, discriminations, memory and repertoire - functional criteria of 'better' brains. While comparative cognition needs to test these expectations to verify what would be one of the major consequences of evolution, comparative neurobiology needs to discover what, in detail, by all the methods and measures of neuroanatomy, neurophysiology and neurochemistry, is different in more complex brains and which of these differences are relevant to behavioral differences. Formerly it was fashionable to deny differences in the dimension that might be called higher and lower. The criterion of complexity, defined as the number of different parts, processes, interactions and behaviors, may be a useful index of advancement. Unequivocal advancement has occurred between some major taxa, although it is not inevitable. Anatomically, it is clear that novelties have evolved and complexity is more than size or number of the same components. Physiologically, new types of cells, local and larger circuits and emergent properties of assemblies have increased the complexity of operations and organization. It needs to be reasserted that more complex brains have evolved repeatedly, both among invertebrates and among vertebrates, because similar assertions have been incorrectly labeled as 'intuitive scaling' and anthropocentric or moral statements. None of these or any necessary implications about tendencies or causation need be involved. The main thrust of this essay is to underline three propositions as steps toward a plan of action: (1) We are deeply ignorant of the exact ways in which the more and the less complex brains differ - emphasizing those from higher taxonomic categories clearly different in grades of complexity. (2) The needed comparisons require the methods of natural history prior to mechanistic analysis, since unfamiliar traits must be uncovered. (3) Especially to include the higher nervous functions in these comparisons, new approaches are needed. I perceive a major frontier of new insights about brains. Pursuit of this large agenda of research will be profoundly significant both for neurobiology and general biology.

ISSN:0006-8977    

DOI:10.1159/000113826

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The connections of a higher order auditory area in the neostriatum intermedium pars ventrolateralis (NTVL) were mapped with pathway tracing techniques in order to elucidate possible pathways by which auditory feedback may influence vocal learning in the budgerigar (Melopsittacus undulatus). Previous research has shown that NTVL receives projections from Field 'L' as well as adjacent portions of the dorsolateral neostriatum intermedium (NIDL) and hyperstriatum ventrale (HV) and, therefore, may be homologous to previously described auditory centers in the dorsal and lateral portions of the auditory neostriatum of songbirds. The efferent connections of NTVL terminate within a small portion of the rostromedial archistriatum as well as a more rostrally situated area within the medial neostriatum intermedium (NI) and HV. Near by (but not overlapping) fields in NI and HV receive input from the nucleus dorsomedialis posterior thalami (DMP), the archistriatum and ectostriatum. Interestingly, only the DMP projection field overlaps a neural field known to be related to the vocal motor system. The DMP projection field corresponds to that previously described as the magnocellular nucleus of the anterior neostriatum; this nucleus is known to project to the higher vocal center in the budgerigar. In addition to projections from NIVL to medial NI and HV, auditory information is relayed to the anterolateral telencephalon directly from the brainstem via the ventrolateral nucleus of the lateral lemniscus (VLV). This latter pathway appears comparable to that described in pigeons derived from the intermediate nucleus of the lateral lemniscus. The projection field of VLV overlaps a restricted portion of the caudal and medial aspect of nucleus basalis. These results support the notion that many aspects of telencephalic auditory pathways in birds are primitive characters, although a direct connection between auditory and vocal motor circuits was not found in the present study.

ISSN:0006-8977    

DOI:10.1159/000113827

出版商:S. Karger AG    

年代:1993

数据来源: Karger