摘要:

Single-unit recordings in the frog''s optic tectum have demonstrated the existence of a systematic spatial separation between the direct contralateral and indirect ipsilateral excitatory receptive fields. Marked differences in this spatial organization were found between paralyzed and anesthesized animals.Significant latency differences were found between sustained (class I/II) and transient (class III) contralateral fibers. Corresponding latency differences were also seen in ipsilaterally driven responses. It is suggested that there may be at least two different classes of ipsilateral fibers.The existence of binocular interaction at the level of the afferent terminal arborizations was investigated, utilizing temporally asynchronous dichoptic stimulation. No such phenomena were seen in curarized animals. These findings are discussed in terms of possible velocity and direction sensitivity mechanisms.

ISSN:0006-8977    

DOI:10.1159/000123631

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

This paper attempts to investigate taxonomic and phylogenetic relationships through an analysis of the distribution of mass within the brain. A multivariate analysis was performed on encephalization ratios for various divisions of the brain, employing volume measurements reported for 63 species by Stephan et al. [1970]. The ratios for each brain region were considered to lie along one of the dimensions of eight dimensional ''brain space'', and distances between all species were calculated and employed in the determination of ''family trees''. It was assumed that modern species have, in many cases, brains representative of different stages of an evolutionary progression towards higher encephalization, and it was assumed that no ''backwards evolution'' occurred. The family trees based on these data and assumptions were rigidly determined and do not represent mere opinion but, rather, inescapable conclusions if one accepts the premises. Most of the findings were in very good agreement with traditional or popular ideas, and this includes conclusions that tree shrews were ancestral to prosimians and that simians are derived from a tarsioid ancestor. Other findings, however, were just as strikingly deviant from current popular and expert thought. Present methods demanded, for example, that man must have a platyrrhine ancestry. While one may reject this particular conclusion it remains true that by present measures the human brain is much more like that of an American wooley or spider monkey than like that of either the chimpanzee or the gorilla.

ISSN:0006-8977    

DOI:10.1159/000123632

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

This paper attempts to investigate taxonomic and phylogenetic relationships through an analysis of the distribution of mass within the brain. A multivariate analysis was performed on encephalization ratios for various divisions of the brain, employing volume measurements reported for 63 species by Stephan et al. [1970]. The ratios for each brain region were considered to lie along one of the dimensions of eight dimensional ''brain space'', and distances between all species were calculated and employed in the determination of ''family trees''. It was assumed that modern species have, in many cases, brains representative of different stages of an evolutionary progression towards higher encephalization, and it was assumed that no ''backwards evolution'' occurred. The family trees based on these data and assumptions were rigidly determined and do not represent mere opinion but, rather, inescapable conclusions if one accepts the premises. Most of the findings were in very good agreement with traditional or popular ideas, and this includes conclusions that tree shrews were ancestral to prosimians and that simians are derived from a tarsioid ancestor. Other findings, however, were just as strikingly deviant from current popular and expert thought. Present methods demanded, for example, that man must have a platyrrhine ancestry. While one may reject this particular conclusion it remains true that by present measures the human brain is much more like that of an American wooley or spider monkey than like that of either the chimpanzee or the gorilla.

ISSN:0006-8977    

DOI:10.1159/000123633

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Endocranial casts of 15 genera of fossil felids provide a record of felid brain evolution over the past 35 million years. Brains of the earliest felids, known as paleofelids, had coronolateral, suprasylvian and variably developed ectosylvian sulci as their only neocortical sulci. The last paleofelids, which became extinct around 8 million years ago, show little change in external brain morphology except for the addition of a presylvian sulcus. The other group of felids, the neofelids, appears about 25 million years ago, with coronolateral and suprasylvian sulci their main neocortical sulci,plus a discontinuous ectosylvian sulcus and small postlateral, sylvian and presylvian sulci. The posterior cerebellar vermis was straight and unexpanded. Beginnings of expansion of the sigmoid gyri and development of the cruciate sulcus are evident in neofelids 15–20 million years ago, and by 5–9 million years ago neofelids had brains that appear modern in external morphology. Endocasts of four genera of Pleistocene saber-toothed felids are similar in sulcal pattern to those of modern felids, except for Dinobastis, which had a unique expansion of visual cortex. Endocasts of 27 species of modern felids, representing the six commonly recognized genera, are strikingly similar in external morphology, although the brains of a few species, such as cheetahs, lynxes and jagouarundis, display distinguishing features. Modern felid brains average about the same size relative to body weight as do those of viverrids, but are about 25% smaller in relative size than those of canids. Olfactory bulbs are relatively smaller in felids than in canids or viverr

ISSN:0006-8977    

DOI:10.1159/000123634

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Endocranial casts of 15 genera of fossil felids provide a record of felid brain evolution over the past 35 million years. Brains of the earliest felids, known as paleofelids, had coronolateral, suprasylvian and variably developed ectosylvian sulci as their only neocortical sulci. The last paleofelids, which became extinct around 8 million years ago, show little change in external brain morphology except for the addition of a presylvian sulcus. The other group of felids, the neofelids, appears about 25 million years ago, with coronolateral and suprasylvian sulci their main neocortical sulci, plus a discontinuous ectosylvian sulcus and small postlateral, sylvian and presylvian sulci. The posterior cerebellar vermis was straight and unexpanded. Beginnings of expansion of the sigmoid gyri and development of the cruciate sulcus are evident in neofelids 15–20 million years ago, and by 5–9 million years ago neofelids had brains that appear modern in external morphology. Endocasts of four genera of Pleistocene saber-toothed felids are similar in sulcal pattern to those of modern felids, except for Dinobastis, which had a unique expansion of visual cortex. Endocasts of 27 species of modern felids, representing the six commonly recognized genera, are strikingly similar in external morphology, although the brains of a few species, such as cheetahs, lynxes and jagouarundis, display distinguishing features. Modern felid brains average about the same size relative to body weight as do those of viverrids, but are about 25% smaller in relative size than those of canids. Olfactory bulbs are relatively smaller in felids than in canids or viverr

ISSN:0006-8977    

DOI:10.1159/000123635

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Endocranial casts of 15 genera of fossil felids provide a record of felid brain evolution over the past 35 million years. Brains of the earliest felids, known as paleofelids, had coronolateral, suprasylvian and variably developed ectosylvian sulci as their only neocortical sulci. The last paleofelids, which became extinct around 8 million years ago, show little change in external brain morphology except for the addition of a presylvian sulcus. The other group of felids, the neofelids, appears about 25 million years ago, with coronolateral and suprasylvian sulci their main neocortical sulci, plus a discontinuous ectosylvian sulcus and small postlateral, sylvian and presylvian sulci. The posterior cerebellar vermis was straight and unexpanded. Beginnings of expansion of the sigmoid gyri and development of the cruciate sulcus are evident in neofelids 15–20 million years ago, and by 5–9 million years ago neofelids had brains that appear modern in external morphology. Endocasts of four genera of Pleistocene saber-toothed felids are similar in sulcal pattern to those of modern felids, except for Dinobastis, which had a unique expansion of visual cortex. Endocasts of 27 species of modern felids, representing the six commonly recognized genera, are strikingly similar in external morphology, although the brains of a few species, such as cheetahs, lynxes and jagouarundis, display distinguishing features. Modern felid brains average about the same size relative to body weight as do those of viverrids, but are about 25% smaller in relative size than those of canids. Olfactory bulbs are relatively smaller in felids than in canids or viverr

ISSN:0006-8977    

DOI:10.1159/000123636

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000123637

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000123638

出版商:S. Karger AG    

年代:1975

数据来源: Karger