ISSN:0006-8977    

DOI:10.1159/000124343

出版商:S. Karger AG    

年代:1973

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:10.1159/000124390

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Studies of decerebrate and spinal cats and monkeys as carried out by the authors over a number of years are reviewed. Factors responsible for early and late changes in reflex activity are considered. Hyperreflexia, as a late event, in chronic spinal animals is chiefly attributed to sprouting from afferent axons.

ISSN:0006-8977    

DOI:10.1159/000124345

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Axonal sprouting of the ipsilateral retinal projections in the adult rat was evaluated as a consequence of contralateral eye removal. In all experimental animals a generalized axonal sprouting was present at each region of normal termination represented by increased quantity and granule size of preterminal degeneration. Increased distribution occurred unequivocally only in the superior colliculus. For partial injury of a single neuron system in the adult brain, axonal sprouting is postulated as a mechanism of internal system reorganization in which system repair and possible recovery or maintenance of function can occur.

ISSN:0006-8977    

DOI:10.1159/000124346

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The removal of an eye in newborn ratsresults in an increased uncrossed optic projection from the intact eye to subcortical visual centers. The additional uncrossed projection arises from areas of retina which would normally project only contralaterally and terminates in regions of geniculate and colliculus which would normally receive only crossed optic axons. The increased projection does not occur in animals enucleated at 10 days or older. It is suggested that the abnormal projection is due largely to axons which have not reached the optic chiasm at the time of the lesion being rerouted to the 'wrong' side of the brain.

ISSN:0006-8977    

DOI:10.1159/000124347

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The longest fibers of the main optic tract reach the upper layers of the superior colliculus (SC) of the midbrain. Destruction of this terminal area in newborn hamsters caused striking anomalies in the distribution of the optic tract, studied after the animals were fully grown. Evidence of termination was found in areas normally devoid of such termination: in the remaining tissue of the colliculus and in the thalamic nucleus lateralis posterior (LP). An abnormally high density of termination was found in part of the ventral nucleus of the lateral geniculate body. These thalamic regions normally receive connections from SC. Retinofugal axons could also be induced to terminate in the medial geniculate body of the thalamus if the brachium of the inferior colliculus, which normally carries auditory information to this cell group, was ablated at birth together with the lesion of SC.If the superficial layers of SC were destroyed unilaterally at birth, axons from the eye contralateral to the lesion not only reached the area of early damage, but also formed an abnormal decussation, crossing the tectal midline to terminate in the medial zone of the undamaged colliculus. Axons from the two eyes competed for terminal space in this intact colliculus, for they terminated in a nonoverlapping manner, and if the axons from the eye contralateral to the remaining SC were eliminated at birth, the anomalously recrossing axons increased in quantity and spread across the entire SC on the 'wrong' side of the midbrain. Hamsters with such an anomaly showed wrong-direction turning in response to visual stimuli in a large part of the visual field.The less the amount of termination found in SC, the greater was the amount in LP. Thus, optic tract axons showed a 'pruning effect' which may be attributed to a tendency for axons to conserve the quantity of their terminal arborizations. The pruning effect alone may account for the hypertrophy we found, after early SC lesions, of the dorsal terminal nucleus of the accessory optic tract. The tendency to invade vacated terminal space may be sufficient to account for an effect of early unilateral eye removal, namely, a pronounced increase in an ipsilateral retinal projection to the medial terminal nucleus of the accessory optic tract.The greatest alterations in axonal projections were seen when the two effects, competition and pruning, seemed to act jointly. Additional factors may have to be considered in fully explaining such neuroplasticity; some of these have been suggested.

ISSN:0006-8977    

DOI:10.1159/000124348

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

The longest fibers of the main optic tract reach the upper layers of the superior colliculus (SC) of the midbrain. Destruction of this terminal area in newborn hamsters caused striking anomalies in the distribution of the optic tract, studied after the animals were fully grown. Evidence of termination was found in areas normally devoid of such termination: in the remaining tissue of the colliculus and in the thalamic nucleus lateralis posterior (LP). An abnormally high density of termination was found in part of the ventral nucleus of the lateral geniculate body. These thalamic regions normally receive connections from SC. Retinofugal axons could also be induced to terminate in the medial geniculate body of the thalamus if the brachium of the inferior colliculus, which normally carries auditory information to this cell group, was ablated at birth together with the lesion of SC.If the superficial layers of SC were destroyed unilaterally at birth, axons from the eye contralateral to the lesion not only reached the area of early damage, but also formed an abnormal decussation, crossing the tectal midline to terminate in the medial zone of the undamaged colliculus. Axons from the two eyes competed for terminal space in this intact colliculus, for they terminated in a nonoverlapping manner, and if the axons from the eye contralateral to the remaining SC were eliminated at birth, the anomalously recrossing axons increased in quantity and spread across the entire SC on the 'wrong' side of the midbrain. Hamsters with such an anomaly showed wrong-direction turning in response to visual stimuli in a large part of the visual field.The less the amount of termination found in SC, the greater was the amount in LP. Thus, optic tract axons showed a 'pruning effect' which may be attributed to a tendency for axons to conserve the quantity of their terminal arborizations. The pruning effect alone may account for the hypertrophy we found, after early SC lesions, of the dorsal terminal nucleus of the accessory optic tract. The tendency to invade vacated terminal space may be sufficient to account for an effect of early unilateral eye removal, namely, a pronounced increase in an ipsilateral retinal projection to the medial terminal nucleus of the accessory optic tract.The greatest alterations in axonal projections were seen when the two effects, competition and pruning, seemed to act jointly. Additional factors may have to be considered in fully explaining such neuroplasticity; some of these have been suggested.

ISSN:0006-8977    

DOI:10.1159/000124349

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Adrenergic neurons are widely distributed in themammalian central nervous system. There are three situations in which these neurons exhibit morphological plasticity; during ontogenetic growth, as an expression of a response to a functional adaptation in the mature nervous system, and as a regenerative response to injury. Only the latter situation, regeneration, has been studied extensively. Transected axons of central adrenergic neurons exhibit vigorous regenerative sprouting. In some situations anomalous innervation patterns are formed whereas in others, such as the reinnervation of transplants of peripheral tissue, an apparently normal and, presumably, functional innervation pattern is formed. The reinnervation of transplants is promoted by nerve growth factor administration. Intact adrenergic axons also are capable of exhibiting marked collateral sprouting in response to removal of other afferents innervating the same area. The factors controlling the latter response and its functional implications are considered.

ISSN:0006-8977    

DOI:10.1159/000124350

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Recent findings have shown that the spinalcord of mammals is capable of limited regeneration. The reparative process involves very limited regeneration of severed nerve fibers and growth of axonal sprouts. In addition, partially deafferented neurons proximal to the site of spinal cord lesion undergo morphological alteration. Following hemisection of the spinal cord nerve fibers reinnervate the morphologically altered neurons proximal to the site of lesion. The present paper reports an investigation of the process in rat, monkey, and man.

ISSN:0006-8977    

DOI:10.1159/000124351

出版商:S. Karger AG    

年代:1973

数据来源: Karger

摘要:

Recent findings have shown that the spinalcord of mammals is capable of limited regeneration. The reparative process involves very limited regeneration of severed nerve fibers and growth of axonal sprouts. In addition, partially deafferented neurons proximal to the site of spinal cord lesion undergo morphological alteration. Following hemisection of the spinal cord nerve fibers reinnervate the morphologically altered neurons proximal to the site of lesion. The present paper reports an investigation of the process in rat, monkey, and man.

ISSN:0006-8977    

DOI:10.1159/000315979

出版商:S. Karger AG    

年代:1973

数据来源: Karger