摘要:

Numerous scientists have sought a homologue of mammalian isocortex in sauropsids (reptiles and birds) and a homologue of sauropsid dorsal ventricular ridge in mammals. Although some of the proposed theories were enormously influential, alternative theories continued to coexist, primarily because the striking differences in pallial organization between adult mammals, sauropsids, and amphibians enabled different authors to enlist different subsets of similarity data in support of different hypotheses of putative homology. A phylogenetic analysis based on parsimony cannot discriminate between such alternative hypotheses of putative homology, because sauropsids and mammals are sister groups. One solution to this dilemma is to include embryological patterns of telencephalic organization in the comparative analysis. Because early developmental stages in different taxa tend to resemble each other more than the adults do, the embryological data may reveal intermediate patterns of organization that provide unambiguous support for a single hypothesis of putative homology. The validity of this putative homology may then be supported by means of a phylogenetic analysis based on parsimony. A comparative analysis of pallial organization that includes embryological data suggests the following set of homologies. The lateral cortex in reptiles is homologous to the piriform cortex in birds and mammals. The anterior dorsal ventricular ridge in reptiles is probably homologous to the neostriatum and ventral hyperstriatum in birds and to the endopiriform nucleus in mammals. The posterior dorsal ventricular ridge in reptiles is most likely homologous to the archistriatum in birds and to the pallial amygdala in mammals. The pallial thickening in reptiles is probably homologous to the dorsal and intercalated portions of the hyperstriatum in birds and to the claustrum proper in mammals. Finally, the dorsal cortex in reptiles is probably homologous to the accessory hyperstriatum and parahippocampal area in birds and to the isocortex in mammals. These hypotheses of homology imply relatively minor evolutionary changes in development but major changes in neuronal connections. Most significantly, they imply the independent elaboration of thalamic sensory projections to derivatives of the lateral and dorsal pallia in sauropsids and mammals, respectively. They also imply the independent evolution of lamination in the pallium of birds and mammals.

ISSN:0006-8977    

DOI:10.1159/000112991

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Numerous scientists have sought a homologue of mammalian isocortex in sauropsids (reptiles and birds) and a homologue of sauropsid dorsal ventricular ridge in mammals. Although some of the proposed theories were enormously influential, alternative theories continued to coexist, primarily because the striking differences in pallial organization between adult mammals, sauropsids, and amphibians enabled different authors to enlist different subsets of similarity data in support of different hypotheses of putative homology. A phylogenetic analysis based on parsimony cannot discriminate between such alternative hypotheses of putative homology, because sauropsids and mammals are sister groups. One solution to this dilemma is to include embryological patterns of telencephalic organization in the comparative analysis. Because early developmental stages in different taxa tend to resemble each other more than the adults do, the embryological data may reveal intermediate patterns of organization that provide unambiguous support for a single hypothesis of putative homology. The validity of this putative homology may then be supported by means of a phylogenetic analysis based on parsimony. A comparative analysis of pallial organization that includes embryological data suggests the following set of homologies. The lateral cortex in reptiles is homologous to the piriform cortex in birds and mammals. The anterior dorsal ventricular ridge in reptiles is probably homologous to the neostriatum and ventral hyperstriatum in birds and to the endopiriform nucleus in mammals. The posterior dorsal ventricular ridge in reptiles is most likely homologous to the archistriatum in birds and to the pallial amygdala in mammals. The pallial thickening in reptiles is probably homologous to the dorsal and intercalated portions of the hyperstriatum in birds and to the claustrum proper in mammals. Finally, the dorsal cortex in reptiles is probably homologous to the accessory hyperstriatum and parahippocampal area in birds and to the isocortex in mammals. These hypotheses of homology imply relatively minor evolutionary changes in development but major changes in neuronal connections. Most significantly, they imply the independent elaboration of thalamic sensory projections to derivatives of the lateral and dorsal pallia in sauropsids and mammals, respectively. They also imply the independent evolution of lamination in the pallium of birds and mammals.

ISSN:0006-8977    

DOI:10.1159/000105936

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Numerous scientists have sought a homologue of mammalian isocortex in sauropsids (reptiles and birds) and a homologue of sauropsid dorsal ventricular ridge in mammals. Although some of the proposed theories were enormously influential, alternative theories continued to coexist, primarily because the striking differences in pallial organization between adult mammals, sauropsids, and amphibians enabled different authors to enlist different subsets of similarity data in support of different hypotheses of putative homology. A phylogenetic analysis based on parsimony cannot discriminate between such alternative hypotheses of putative homology, because sauropsids and mammals are sister groups. One solution to this dilemma is to include embryological patterns of telencephalic organization in the comparative analysis. Because early developmental stages in different taxa tend to resemble each other more than the adults do, the embryological data may reveal intermediate patterns of organization that provide unambiguous support for a single hypothesis of putative homology. The validity of this putative homology may then be supported by means of a phylogenetic analysis based on parsimony. A comparative analysis of pallial organization that includes embryological data suggests the following set of homologies. The lateral cortex in reptiles is homologous to the piriform cortex in birds and mammals. The anterior dorsal ventricular ridge in reptiles is probably homologous to the neostriatum and ventral hyperstriatum in birds and to the endopiriform nucleus in mammals. The posterior dorsal ventricular ridge in reptiles is most likely homologous to the archistriatum in birds and to the pallial amygdala in mammals. The pallial thickening in reptiles is probably homologous to the dorsal and intercalated portions of the hyperstriatum in birds and to the claustrum proper in mammals. Finally, the dorsal cortex in reptiles is probably homologous to the accessory hyperstriatum and parahippocampal area in birds and to the isocortex in mammals. These hypotheses of homology imply relatively minor evolutionary changes in development but major changes in neuronal connections. Most significantly, they imply the independent elaboration of thalamic sensory projections to derivatives of the lateral and dorsal pallia in sauropsids and mammals, respectively. They also imply the independent evolution of lamination in the pallium of birds and mammals.

ISSN:0006-8977    

DOI:10.1159/000112992

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

This report describes the dynamics of the horizontal optokinetic response of the goldfish and compares them with those of other species. Eye rotational velocity in response to step and sinusoidal rotations of the visual surround was tested using goldfish that had both eyes free to view the surround and to rotate with it. The step response was tested by switching on a visual surround display that was rotating at constant velocity, and then switching off the display, leaving the goldfish in the dark. The step-onset response was characterized by rapid and gradual components; the latter rose with an almost linear trajectory for higher surround velocities. The response was more rapid at step-offset than at step-onset. The step-offset response overshot baseline eye velocity for most goldfish and was oscillatory for the others. The steady-state response increased with constant velocity surround rotation within the range ±40 deg/sec but saturated outside that range. Steady-state response gain was higher for nasally-directed than for temporally-directed surround rotations. The frequency response was essentially low-pass, with gain decreasing from about 0.9 and phase lag increasing from zero to 90 deg as surround rotational frequency increased from 0.01 to 3.0 Hz. Sinusoidal response gain decreased as a function of surround peak acceleration. The results indicate that the horizontal optokinetic response of the goldfish is nonlinear and resembles in many respects that of mammals. Models developed to simulate the dynamics of the optokinetic response of mammals can be applied to that of goldfish and reproduce its nonlinear features.

ISSN:0006-8977    

DOI:10.1159/000112993

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

In Haplochromis burtoni, an African cichlid fish, male sexual maturation is regulated via social interactions, and these effects are mediated by gonadotropin-releasing-hormone (GnRH)-containing neurons in the preoptic area of the brain. Since brain monoaminergic systems are known to be involved in the regulation of GnRH release, and the activity of these systems is influenced by agonistic interactions, we analyzed the effect of social status on brain monoaminergic activity in H. burtoni. Animals were either (1) in normal social groups consisting of two males and four females or (2) in groups of one male and five females. Quantitative behavioral observations were made on each group of animals and, following sacrifice several physiological measurements were made. Concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA, the main 5-HT metabolite) and tryptophan (TRP, the amino acid precursor of 5-HT), dopamine (DA) and 3, 4-dihydroxyphenylacetic acid (DOPAC, the main DA metabolite) were measured. The 5-HIAA/5-HT and DOPAC/DA ratios were calculated and used as indexes of 5-HT and DA activity, respectively. In addition, the gonado-somatic index was calculated from body and gonadal weights and used as an index of reproductive status. Concentrates of 5-HIAA as well as 5-HLAA/5-HT ratios were significantly higher in brainstem of non-territorial males than in that of territorial males, and similar trends were seen in the telencephalon and hypothalamus. Moreover, TRP concentrations in the telencephalon and brainstem were significantly lower in non-territorial males. In this species, sexual maturation in females is not socially regulated, and there was no significant correlation between measured antagonistic behavior and biochemical indices. These results suggest a fundamental difference in the neurochemical responses between male and female H. burtoni.

ISSN:0006-8977    

DOI:10.1159/000112994

出版商:S. Karger AG    

年代:1997

数据来源: Karger