摘要:

Electrophysiological and light microscopical studies were made on the vestibular area of the dogfish hindbrain. Three vestibular nuclei were distinguished: the superior nucleus (VES), the magnocellularis nucleus (VEM), and the ventral nucleus (VEV). The distribution of field potentials evoked in the hindbrain by stimulation of nerve VIII confirms the location and extent of the vestibular nuclei. It also raises the possibility of a direct contralateral projection of vestibular nerve fibres. Unit studies confirm the interpretation of the field potentials and provide evidence of mono- and polysynaptic activation of vestibular nuclear neurons by vestibular afferents.

ISSN:0006-8977    

DOI:10.1159/000121829

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

About 2 weeks after metamorphosis, midwife toads Alytes obstetricans judge the size of a prey object mainly in scales of visual angle. For distant objects they show a tendency to respond to absolute object size. About 6 months later the juvenile animals are able to judge absolute prey size in relation to the stimulus distance (''size constancy'' phenomenon). This ability is not necessarily based on learning or previous experience.

ISSN:0006-8977    

DOI:10.1159/000121830

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Autoradiographic labelling has been employed to analyze the morphogenesis of the neostriatum. Pregnant rabbits received a single intraperitoneal injection of tritiated thymidine at different stages of gestation. Careful microscopical observation of the autoradiographs shows that cellular components of the neostriatum originate between days 15 and 18 of the intrauterine life from a layer of proliferating matrix cells that lies on the floor of the anterior part of the lateral ventricle (ganglionic eminence). From this proliferating layer, precursor cells migrate outwards to reach the developing neostriatum in a sequential fashion according to two gradients of histogenesis. Thus, it was found that neurons formed at early stages occupy a ventromedial position in the neostriatum, while those formed at later stages occupy a dorsolateral position (ventromedial to dorsolateral gradient). Furthermore, the present study indicates that the rostral regions of the neostriatum arise somewhat later than the caudal ones, demonstrating the existence of a caudo-cephalic gradient of cytogenesis.

ISSN:0006-8977    

DOI:10.1159/000121831

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The phenomenon of ''transfer'' is used to draw attention to the point that whereas the brain stem animal can solve a variety of individual problems ad hoc, only the intact animal appears to be able to use the result of one problem to solve a closely related problem. It is suggested that this is because information is organized in the cortex as objects and concepts, rather than as a set of more or less elaborate features. The shortcomings of a hierarchical system of feature detectors as a model of cortical organization are examined, and compared with a distributive model. It is pointed out that our ways of thinking about complex tones – e.g. their pitch and harmonic structure – is related to the fact that sound suffers a Fourier transform at the cochlea, and it is this transform which is represented in the brain stem. It is suggested that an analogous integral transform may equally naturally represent the data as ''objects'' in the cortex. The resistance of such transforms to degradation by ablation, and the implications for single neurone behaviour are discus

ISSN:0006-8977    

DOI:10.1159/000121832

出版商:S. Karger AG    

年代:1979

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000121833

出版商:S. Karger AG    

年代:1979

数据来源: Karger