摘要:

AbstractWe used intracellular dye injections in lightly fixed cortical slices to examine the distribution and morphology of area 17 neurons that project to extrastriate cortex. Both the projection to the medial bank of the posterior lateral suprasylvian sulcus (PMLS) and the projection to area 18 arise from a number of different morphological types distributed throughout layers 2–6. The majority are found in the superficial layers and include large, medium, and small pyramidal neurons. Some are also found in the deep layers and they include very large, pyramidal neurons as well as some heretofore undescribed, fusiform neurons. The projection to area 18 contains two types not found in the projection to PMLS: Spinous stellate neurons in layer 4 and inverted pyramidal neurons in layer 3. Finding that a variety of morphological types contribute projections to a single cortical area raises the possibility that corticocortical projections, like retinogeniculate and geniculocortical projections, comprise multiple parallel pathways with different physiological properties and patterns of termination. Finding that the projection to area 18 contains morphological types that do not project to PMLS indicates that the projections from area 17 are likely to contribute to the functional specialization of extrastriate visual area

ISSN:0092-7317    

DOI:10.1002/cne.903030112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractIn hot and dry weather, terrestrial snails withdraw into their shells and remain inactive for long periods of time. This phenomenon, known as aestivation, is the basis for our investigation of the effects of behavioral inactivity on neuronal structure. Several recent studies have shown that the level of afferent electrical activity is an important modifier of structure, even in adult animals. During aestivation, sensory stimulation (and therefore presumably afferent activity) is greatly reduced. We have tested the hypothesis that long‐term behavioral inactivity causes a regression of dendrites. Two identified neurons ofAchatina fulicawere selected for study, the giant cerebral neuron (GCN) and RPall. The cells were viewed on 10‐μm‐thick sections after intracellular injection of hexamminecobalt chloride. They were reconstructed by using a video camera attached to a light microscope and a digitizing board resident in a microcomputer. Snails in the aestivated group were completely inactive for 8 weeks beginning at age 23 weeks. A quantitative analysis showed that there were no significant differences in either cell, in either the total mass of material or its distribution, comparing cells from the Aestivated snails and cells from the Younger snails (age 23 weeks) and the Older snails (age 33 weeks). These results suggest limits to the modifiability of neuronal str

ISSN:0092-7317    

DOI:10.1002/cne.903030113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractIn order to determine whether the developing central gustatory system responds to altered sensory experience, terminal fields of the chorda tympani nerve (CT) within the nucleus of the solitary tract (NTS) in control, NaCl deprived, and rats in which CT taste responses “recovered” from NaCl deprivation were investigated via anterograde transport of HRP. Rats fed a low sodium diet (0.03% NaCl) from the third day of gestation to at least 35 days postnatal exhibited both abnormally distributed and irregularly shaped CT terminal fields. Specifically, the dorsal zone of the field was the smallest in controls whereas it was the largest in deprived rats, occupying more medial and caudal territory within the nucleus. The portion of the field immediately ventral to the dorsalmost zone was characterized by a compact, oval shape in control rats and an irregular, broad configuration in deprived rats. Although it has been observed that deprivation‐induced changes in the neurophysiology of the CT are reversible, the central morphological alterations reported here remain abnormal. Restoration of 1.0% NaCl in the diet at 28 days postnatally, for at least 60 days, did not result in normal CT terminal fields. The pattern of the field in rats “recovered” from NaCl deprivation was comparable to that found in deprived rats, and the size of the field was three times that found in control and deprived rats.The terminal fields of another nerve containing gustatory afferents, the lingual‐tonsilar branch of the glossopharyngeal nerve (LT‐IX), were studied for comparison. Interestingly, the pattern of the LT‐IX field was not altered by sodium deprivation. The relative size and topography of the LT‐IX fields in deprived rats were similar to controls. Thus, sodium deprivation appears to alter selectively the anatomical organization of the CT. Differences in vulnerability between the CT and LT‐IX terminal fields may derive from differences in the responsiveness of these nerves to NaCl, and/or to differences in the timing of

ISSN:0092-7317    

DOI:10.1002/cne.903030114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903030101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY