摘要:

Using both binocular and monocular viewing conditions, optokinetic nystagmus (OKN) frequency-velocity functions were measured before and after ophthalmic laser-produced retinal lesions. With binocular viewing conditions, the range of effective pattern velocities and the upper velocity threshold increased by 20–30°/sec in subjects with both foveas lesioned, and by 12°/sec in a subject with only a single foveal lesion. Subjects with parafoveal lesions showed no change in postlesion binocular OKN response functions.Prelesion monocular OKN functions were obtained for both temporal-to-nasal (T-N) and nasal-to-temporal (N-T) directions of pattern movement. T-N OKN functions were similar to those obtained with binocular viewing but N-T movement elicited OKN over a much narrower range of stimulus velocities. Lesions of the foveal area appeared to have little effect on N-T OKN functions, although an increase in N-T upper velocity thresholds was obtained from at least one eye in 4 of 5 animals. Thus, lesions of the foveal and parafoveal area do not impair, and may actually facilitate, OKN in the pig

ISSN:0006-8977    

DOI:10.1159/000121792

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Two major conceptual approaches to the study of visual receptive field physiology can be identified; one, here termed the ''parametric'' approach, which considers all the properties of a cell to be potentially related to that cell''s functional role, and a second, here termed the ''feature extraction'' approach, which regards a particular receptive field property as defining a cell''s role in the visual system. The parametric approach seems most compatible with network theories of visual information processing, while the feature extraction approach suggests a localized single-cell form of visual representation. In this paper we trace the growth and development of these two approaches, from 1938 to the present, by dividing this period into four segments: 1938–1953, during which the foundations of both approaches were laid; 1953–1966, the major period of growth for feature-extraction analyses; 1966–1975, the major period of growth for parametric analyses; and 1975 to the present, during which the parametric approach has been expanded by the incorporation of principles of systematics and population biology to enable groups of neurones to be studied from a biological perspe

ISSN:0006-8977    

DOI:10.1159/000121793

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Within any biological population there is considerable variation in the physical characteristics of individual members, and the understanding and classification of such populations always depends on the interpretation of this variation. A major point of this paper is that groups of neurones can also be regarded as biological populations, and that at least three distinct types of variation can be found within any neural population: role-indicating variation, which enables different cells or groups of cells to perform different functions; systematic variation, which allows different cells (or sometimes the same cell) to perform a particular function under varying conditions; and residual variation, which is principally related to mechanisms of evolution and provides the population with its biological adaptability. Examples of these three types of variation are suggested for a number of properties of retinal ganglion cell populations.A second major point is that any functional classification of nerve cells should contain multiple taxonomic levels, corresponding to different levels of complexity and interaction within the nervous system. Thus, individual cells can belong to more than one group, each at a different taxonomic level, and these groups of cells can be viewed as interacting with each other rather than as operating in isolation. A multiple-level classification of cat retinal ganglion cells is presented with two broad groups, each subdivided into two lower-level groups, and an attempt is made to identify the categories of visual function to which these groups are related.

ISSN:0006-8977    

DOI:10.1159/000121794

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

In 22 adult sharks representing eight species, the mesencephalic trigeminal nucleus (Mes V) was examined employing the Romanes reduced silver method. Morphological evidence is presented of extensive development of neurites and intranuclear communication among Mes V cells of sharks, as well as their apparent innervation by extranuclear neurons. Species differences and the possible significance of the morphology of the Mes V in sharks to certain aspects of their behavior are discussed. A brief comparison of the Mes V of elasmobranchs and those of reptiles and mammals is included.

ISSN:0006-8977    

DOI:10.1159/000121795

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Scanning electron microscopic observations reveal cerebrospinal fluid contacting and supraependymal cell bodies of the mesencephalic trigeminal (Mes V) nucleus in adult specimens of mako and blue sharks, but not in very young specimens of the smooth dogfish shark. Possible functional roles are discussed in terms of participation of cerebrospinal fluid contacting Mes V cells in a neuroendocrine regulatory system. Comparisons are made with light microscopic observations of the relationship of Mes V cells with the ventricular wall. General features of the scanning electron microscopic appearance of the roof of the ventricle of the optic tectum in sharks are described and compared to similar general features found in the third ventricle of a variety of vertebrates.

ISSN:0006-8977    

DOI:10.1159/000121796

出版商:S. Karger AG    

年代:1980

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000121797

出版商:S. Karger AG    

年代:1980

数据来源: Karger