摘要:

In rats with pons transection photic or optic nerve stimulation elicits a response in dorsal hippocampus with approximately the same latency, amplitude and time course as the response in striate cortex. After optic nerve stimulation a positive polyphasic deflection with the last peak at 10 ms is followed by a larger biphasic major deflection with peaks at 15 and 25 ms and later, slower deflections at intervals of 125 ms. The polyphasic deflection is maximal in the inferior part of the hippocampus but does not reverse polarity; the other deflections reverse above and below an isoelectric point in the hilum of the dentate gyrus, a distribution attributable to depolarization in the molecular layers, perhaps also cell bodies, of that structure. The major deflection is more sensitive to changes in optic nerve stimulus strength than the response in striate cortex and is more resistant to reduction in amplitude during repetitive stimulation, following frequencies up to 50/s. The pathway between retina and hippocampus for all parts of the response is interrupted by lesions in the tectum. The major deflection is abolished by lesions in the posterior cingulum. In the posterior cingulum the pathway has fast and slow components in the lower and upper portions, respectively, associated with the first and second parts, respectively, of the major deflection. The pathway is not interrupted by lesions in the fornix, septal nuclei, anterior cingulum, anterior medial thalamus or medial midbrain ventral to the superficial tectum. There are complex interactions, up to several hundred milliseconds in duration, between the response to optic nerve stimulation and those elicited by stimulation in the cingulum, midbrain and thalamus. Tonic influences on the dentate gyrus from cingulum and tectum are described.

ISSN:0006-8977    

DOI:10.1159/000121577

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The topographic organization of the facial nucleus motoneurons in the rat was investigated with the horseradish peroxidase retrograde tracing method using tetramethyl benzidine as a chromogen. Facial muscles were ''represented'' on the facial nucleus in an orderly fashion. For example, the motoneurons supplying the rostral (nasolabial) muscles are laterally placed, whereas those supplying the caudal (auricular) muscles are medially placed. Notable findings in this study are: (i) the relatively unremarkable size of the nasolabial (vibrissal) muscle representation; there does not seem to be an increase in size of this part of the nucleus, commensurate with the specialized sensory functions of the vibrissal area of the face and (ii) the neurons supplying the posterior belly of the digastric are found in the suprafacial nucleus winch lies about 1 mm dorsal to the main facial nucleus.

ISSN:0006-8977    

DOI:10.1159/000121578

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Marine turtle hatchlings orient seaward by responding to photic cues that guide them toward the brightest horizon. Earlier research has suggested that they have a positive phototropotactic reaction to light but the behaviour must be more complex than this because circling both toward the uncovered and the covered eye has been observed in unilaterally blindfolded turtles. The present work resolved some of these problems by studying circling direction as a function of how long one eye had been covered prior to testing. Different groups of neonate loggerhead turtles (Caretta caretta) were tested from 10 s to 19 h after the application of a unilateral blindfold. The longer this had been on, the less the turtle circled, but beyond 1 h further changes were slight. Initially, circling was predominantly toward the uncovered eye but after the blindfold had been on for 1 h circling toward the covered eye occurred equally often.The time course of circling was also examined in asynchronously, bilaterally blind-folded turtles. One eye was covered 6 h before the other, and tests were made at various times after the second eye had been covered. Asynchronous bilateral blindfolding caused more intense circling and disrupted seaward orientation more severely than unilateral blindfolding. The time course of the decline in circling showed similarities between both treatments, suggesting that they were activating the same mechanism. Dark adaptation was examined as a possible explanation of such transient turning tendencies and previous models of sea-finding were elaborated.

ISSN:0006-8977    

DOI:10.1159/000121579

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Cortical afferents to the prefrontal cortex were studied in 10 bush babies (Galago senegalensis) by means of somatopetal transport of horseradish peroxidase. The lateral injections invariably labeled neurons in the temporal cortex and in most cases also in the insular and parietal regions. In some of these brains the cingulate and retrosplenial areas contained labeled perikarya. Injections into the medial cortex, on the other hand, consistently labeled cell bodies in the cingulate cortex, but not in the insular, temporal and parietal regions. When both lateral and medial sites of the bush baby''s prefrontal cortex are considered together, apparently fewer cortical areas (as defined by Brodmann''s cytoarchitectonic maps) project to the prefrontal cortex in the bush baby than in the rhesus monkey. This statement holds for both ipsi- and contralateral projections.

ISSN:0006-8977    

DOI:10.1159/000121580

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Growth characteristics of the tammar wallaby brain have been determined from 143 animals at various stages of growth from birth to adulthood, with particular emphasis on the 250 days of pouch life. The macroscopic anatomy of the brain is also described for pouch young at days 3,5,88 and 190 days after birth, and for the adult.The transition from the rapid to mature growth phases of each brain structure occurs between days 120 and 180 after birth, and coincides with the appearance of previously described developmental characters or behaviour. The allometric relationships of brain and body growth described in this marsupial resemble those described for primates.Because of the accessibility of the pouch young during the critical period of brain differentiation, this marsupial may provide a useful laboratory model for the study of brain development.

ISSN:0006-8977    

DOI:10.1159/000121581

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Fifteen characters of brain organization are identified for which primitive and derived states can be distinguished, and which are thus useful in reconstructing mammalian phylogeny. The states of the characters are numerically coded in sequence from most primitive to most derived, to facilitate reciprocal comparisons in comprehensive genealogical analyses. The characters include certain features of cerebral circulation, cytoarchitecture, fiber pathways, and sensory projections. Seven characters are shared with nonmammals, a fact which makes them particularly useful for establishing their primitive vs. derived states; the other eight characters are features peculiar to mammals. Ten characters provide impressive reinforcement for traditional major groupings of the species, while five provide bases for new ideas about mammalian relationships.

ISSN:0006-8977    

DOI:10.1159/000121582

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

A new index of encephalization has been proposed based on a reanalysis of the brain-body weight relationship in mammals. The new index, c, is related to the volume of the whole brain as well as to the surface and volume of the cerebral cortex. From an evolutionary point of view the index-cortex relationship is particularly interesting, since the structure of the brain which contributes most to its evolutionary progression is the cerebral cortex. A theory of corticalization has been developed in which the surface of the cerebral cortex is analyzed into two components, Sb, determined by the size of the animal, and Se, associated with an increase in the information-processing capacity. An analogue division has been performed for the cortical volume. Furthermore, an inquiry has been made into the brain structure which can serve as an estimator of body weight. The medulla oblongata appears to be such a structure.

ISSN:0006-8977    

DOI:10.1159/000121583

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The varying states of 15 characters of the central neural organization are tabulated as they occur in each of 147 mammalian species. For each character and species, scores are entered designating the primitive or derived state of the character as it is observed in that species. This tabulation provides data in numerically ordered form for multiple analyses of possible phylogenetic relationships which take into account variations in several different characters simultaneously.

ISSN:0006-8977    

DOI:10.1159/000121584

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Electrophysiological and light microscopical studies were made on the dogfish vestibulocerebellum. The cell types, estimates of their numbers, and the organization of this part of the cerebellum are described and compared with the other lobes of the elasmobranch cerebellum. Electrophysiological study of the inputs to this region from the VIIIth nerves indicates that primary afferent fibres from the VIIIth nerve project to the ipsilateral granule cell layer.

ISSN:0006-8977    

DOI:10.1159/000121585

出版商:S. Karger AG    

年代:1982

数据来源: Karger