摘要:

Principles of phylogenetic reconstruction are reviewed and the Wagner algorithm for building trees from many characters simultaneously is described. An example worked by hand is presented using five brain characters of four species.

ISSN:0006-8977    

DOI:10.1159/000121506

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Phylogenetic trees were computed by the Wagner algorithm from data on up to 15 brain characters scored on 154 specimens of 134 mammalian species. Because the data were not complete on all specimens, only one tree, of 18 taxa, was generated on all 15 features: a tree of 99 species was computed from 10 characters, and trees of 38 species from 10 and 12. The 38-taxon trees were considered best because they preserved most completely the integrity of mammalian orders. All trees consistently separated the subclasses of mammals and suggested that rodents, insectivores, and the tree shrew were most derived on the basis of brain characters. The trees' shapes are sensitive to small alterations in character scorings, largely because of the relatively few characters available and small differences in the number of states among them.

ISSN:0006-8977    

DOI:10.1159/000121507

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Wagner trees based on the analysis of 15 brain characters scored on 154 specimens of 134 mammalian species show consistent patterns of relationship among the taxa, i.e. (1) monotremes are the primitive complement of the group uniting marsupials and placentals; (2) among marsupials, diprotodont Australian forms are more derived; (3) placental mammals divide into two groups of orders, roughly the ferungulates (carnivores, ungulates, and subungulates) and the unguiculates-plus-gliroids (chiropterans, dermopterans, lagomorphs, rodents, primates, and insectivores including elephant shrews); (4) edentates sit at the base of or just before the placental dichotomy; (5) the tree shrew and tarsier show the same pattern of distribution of brain traits as some rodents, as do prosimians and New World monkeys.

ISSN:0006-8977    

DOI:10.1159/000121508

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The afferent connections of the auditory cortex of the acallosal marsupial Trichosurus vulpecula have been studied using the retrograde transport of horseradish peroxidase. The enzyme was applied by electrophoresis from a micropipette previously used to define physiologically the organization of the auditory cortex. Three major (lateral, dorsomedial and ventromedial) sectors of the medial geniculate contribute axons to the ipsilateral auditory cortex; the connections from at least the lateral sector are topographically arranged. Axons reach the auditory field from the contralateral cortex by way of the anterior commissure and fasciculus aberrans.

ISSN:0006-8977    

DOI:10.1159/000121509

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

An average field response to electrical stimulation in the hippocampus has been recorded in dorsomedial rat midbrain. The fully developed response is triphasic. Latencies of the three components and their behavior during repetitive stimulation are compatible with the assumption that they are antidromic and originate, respectively, in proximal axons, cell bodies and dendrites. Conduction velocity is estimated to be 5 m/s. Reversal in polarity of the response at different recording points within a distance of 1 mm and abolition by small midbrain lesions confirm location of the active neural elements in that region. Lesions in the white matter of posterior cingulum and in the thalamocortical radiation abolish the response. Latencies of the response recorded in the thalamocortical radiation are in accord with the conclusion that the fibers pass in this location. The findings support results of an earlier study suggesting that visual information is transmitted without a synapse from dorsomedial midbrain to dentate gyrus by a pathway that reaches the cerebral hemisphere in the thalamocortical radiation and enters hippocampus from white matter in the posterior cingulum. A study of visual responses in the medial and dorsal wall of the cerebral hemisphere in lizards may help to evaluate the hypothesis that in these regions are the ancestral homologues for dentate gyrus and cornu ammonis, respectively, in mammalian hippocampus.

ISSN:0006-8977    

DOI:10.1159/000121510

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

An average field response to electrical stimulation in the hippocampus has been recorded in dorsomedial rat midbrain. The fully developed response is triphasic. Latencies of the three components and their behavior during repetitive stimulation are compatible with the assumption that they are antidromic and originate, respectively, in proximal axons, cell bodies and dendrites. Conduction velocity is estimated to be 5 m/s. Reversal in polarity of the response at different recording points within a distance of 1 mm and abolition by small midbrain lesions confirm location of the active neural elements in that region. Lesions in the white matter of posterior cingulum and in the thalamocortical radiation abolish the response. Latencies of the response recorded in the thalamocortical radiation are in accord with the conclusion that the fibers pass in this location. The findings support results of an earlier study suggesting that visual information is transmitted without a synapse from dorsomedial midbrain to dentate gyrus by a pathway that reaches the cerebral hemisphere in the thalamocortical radiation and enters hippocampus from white matter in the posterior cingulum. A study of visual responses in the medial and dorsal wall of the cerebral hemisphere in lizards may help to evaluate the hypothesis that in these regions are the ancestral homologues for dentate gyrus and cornu ammonis, respectively, in mammalian hippocampus.

ISSN:0006-8977    

DOI:10.1159/000315989

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

A progressive enlargement of the hominid brain started 3–2 million years ago, probably from a gracile australopithecine form. Since then, three major transitions in degree of encephalization have taken place, leading to modern Homo sapiens. In the present study it is shown that these transitions must have occurred in rapid bursts, interspersed with long periods of little or no evolutionary change (stasis). This stepwise mode of encephalization is in accordance with the model of punctuated evolutionary change. A further inquiry has been made into the size of the cerebral cortex of hominids and into the number of cortical neurons based on estimates which were derived from allometric equations in extant mammals.

ISSN:0006-8977    

DOI:10.1159/000121511

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The course and terminal distribution of cervical primary afferents in the dorsal column nuclei were studied in the fox squirrel, Sciurus niger. Unilateral rhizotomies were performed at cervical levels C3, C4, C5, C6 and C8. For all spinal levels studied except C8, degeneration in the medullary cuneate fasciculus was present within two distinct groups. They included a large oblique lateral lamina and a small superficial group of degeneration. The superficial group was horizontal, located medial to the large lamina and appeared to be formed by the medial shifting of fibers away from the initial larger group. Fibers in the large primary lamina appeared to terminate primarily in the ventrolateral areas of the cuneate nucleus. Fibers from the superficial group, however, appeared to project mostly to dorsal cuneate nuclear areas. Hence, the dual transverse terminal patterns for cervical fibers in the cuneate nucleus appeared to be related directly to a fiber sorting process that involved the formation of two often separate ascending fiber groups in the cuneate fasciculus. The results of this study are compared with the mechanosensory mapping of the dorsal column nuclei in the squirrel.

ISSN:0006-8977    

DOI:10.1159/000121512

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The olivocerebellar projection has been studied in the rat using the horseradish peroxidase (HRP) retrograde tracing technique. All regions of the cerebellum, except for the flocculonodular lobe, were injected with small volumes of HRP. The overall organization of the rat olivocerebellar projection is similar in all major respects to that found in other mammals. For example, in the rat Crus 1 and Crus 2 receive afferents from the principal olive, medial part of the rostral dorsal olive, the rostral medial olive, the dorsal cap and the ventrolateral outgrowth which agrees with studies in the cat. The most notable difference between the present study and studies in other mammals is the finding of a projection in the rat from the dorsomedial cell column to all regions of the cerebellar hemispheres, except for the paraflocculus.

ISSN:0006-8977    

DOI:10.1159/000121513

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The olivocerebellar projection has been studied in the rat using the horseradish peroxidase (HRP) retrograde tracing technique. All regions of the cerebellum, except for the flocculonodular lobe, were injected with small volumes of HRP. The overall organization of the rat olivocerebellar projection is similar in all major respects to that found in other mammals. For example, in the rat Crus 1 and Crus 2 receive afferents from the principal olive, medial part of the rostral dorsal olive, the rostral medial olive, the dorsal cap and the ventrolateral outgrowth which agrees with studies in the cat. The most notable difference between the present study and studies in other mammals is the finding of a projection in the rat from the dorsomedial cell column to all regions of the cerebellar hemispheres, except for the paraflocculus.

ISSN:0006-8977    

DOI:10.1159/000315990

出版商:S. Karger AG    

年代:1983

数据来源: Karger