摘要:

The ultrastructure of the dorsal lateral geniculate complex in the turtles Pseudemys scripta elegans and Chrysemys picta belli has been studied. The majority of neurons have somata situated in a cell plate that forms the medial face of the complex. Relatively few synaptic contacts occur on the somata of cell plate neurons, but three types of axon terminals contact their proximal dendrites as they course through the cell plate. The most frequent are terminals with clear, round synaptic vesicles that form asymmetric junctional complexes. A second type has both clear and round, and dense-cored vesicles and forms asymmetric junctional complexes. The third type has clear, pleomorphic vesicles and forms symmetric junctional complexes. The same three types of terminals are presynaptic to the dendrites of cell plate neurons as they proceed through the inner half of the geniculate neuropile that is interposed between the cell plate and optic tract. These dendrites branch into varicose, finger-like distal dendrites within the outer half of the neuropile. The finger-like processes contain clear, pleomorphic vesicles and are linked with each other via dendrodendritic synapses with symmetric junctional complexes. The distal dendrites are postsynaptic to axon terminals with clear, round synaptic vesicles and asymmetric junctional complexes.Cell plate neurons thus comprise three regions, each with a distinct synaptic organization. The first region is formed by the somata of cell plate neurons and receives few synaptic contacts. The second region is formed by the proximal dendrites both in the cell plate and the inner half of the neuropile. It receives a moderate contingent of axodendritic terminals. The last region is formed by the distal dendrites of the cell plate neurons. They participate in dendrodendritic synapses and are postsynaptic to axon terminals with clear, round synaptic vesicles.

ISSN:0006-8977    

DOI:10.1159/000118676

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The ultrastructure of the dorsal lateral geniculate complex in the turtles Pseudemys scripta elegans and Chrysemys picta belli has been studied. The majority of neurons have somata situated in a cell plate that forms the medial face of the complex. Relatively few synaptic contacts occur on the somata of cell plate neurons, but three types of axon terminals contact their proximal dendrites as they course through the cell plate. The most frequent are terminals with clear, round synaptic vesicles that form asymmetric junctional complexes. A second type has both clear and round, and dense-cored vesicles and forms asymmetric junctional complexes. The third type has clear, pleomorphic vesicles and forms symmetric junctional complexes. The same three types of terminals are presynaptic to the dendrites of cell plate neurons as they proceed through the inner half of the geniculate neuropile that is interposed between the cell plate and optic tract. These dendrites branch into varicose, finger-like distal dendrites within the outer half of the neuropile. The finger-like processes contain clear, pleomorphic vesicles and are linked with each other via dendrodendritic synapses with symmetric junctional complexes. The distal dendrites are postsynaptic to axon terminals with clear, round synaptic vesicles and asymmetric junctional complexes.Cell plate neurons thus comprise three regions, each with a distinct synaptic organization. The first region is formed by the somata of cell plate neurons and receives few synaptic contacts. The second region is formed by the proximal dendrites both in the cell plate and the inner half of the neuropile. It receives a moderate contingent of axodendritic terminals. The last region is formed by the distal dendrites of the cell plate neurons. They participate in dendrodendritic synapses and are postsynaptic to axon terminals with clear, round synaptic vesicles.

ISSN:0006-8977    

DOI:10.1159/000316009

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The response evoked in the cerebral cortex of laboratory rats after stimulation of the medullary pyramid is surface-positive. It begins 0.9–1.6 ms after the stimulus, attains peak amplitude (up to 2 mV) in 0.8–1.2 ms and lasts 2–4 ms. It occurs throughout the anterior two-thirds of the dorsal cortex and is largest lateral to bregma, with a secondary maximum in the somatosensory area II. Although it depends on antidromic conduction in pyramidal tract fibers for its production, it varies in amplitude, configuration and latency at different recording sites and at the same sites on repeated trials. It reverses polarity deep in the cortex to become a large, negative wave deep in layer V, and maintains that polarity into the white matter. Current source density analysis reveals a strong sink in layer V, with a strong source just superficial to that sink and a weaker source in layer VI. The antidromic response disappears during spreading depression, but recovers more rapidly than the primary response evoked by skin stimulation. It decreases progressively in amplitude with continuous 200-Hz iterative stimulation, and recovers slowly at the end of stimulation. The primary response evoked by contralateral forepaw and hindpaw stimulation is highly localized, being entirely within the antidromic response distribution. The antidromic response in laboratory rats consists of a small, surface-positive component analogous to the pure antidromic response of cats, and of a large, surface-positive response analogous to that found in wood-chucks, rabbits, opossums and slow lorises. It is argued that this latter response results from synaptic action in pyramidal tract axon collaterals, probably onto cells in layer V, rather than being a purely antidromic event.

ISSN:0006-8977    

DOI:10.1159/000118677

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The response evoked in the cerebral cortex of laboratory rats after stimulation of the medullary pyramid is surface-positive. It begins 0.9–1.6 ms after the stimulus, attains peak amplitude (up to 2 mV) in 0.8–1.2 ms and lasts 2–4 ms. It occurs throughout the anterior two-thirds of the dorsal cortex and is largest lateral to bregma, with a secondary maximum in the somatosensory area II. Although it depends on antidromic conduction in pyramidal tract fibers for its production, it varies in amplitude, configuration and latency at different recording sites and at the same sites on repeated trials. It reverses polarity deep in the cortex to become a large, negative wave deep in layer V, and maintains that polarity into the white matter. Current source density analysis reveals a strong sink in layer V, with a strong source just superficial to that sink and a weaker source in layer VI. The antidromic response disappears during spreading depression, but recovers more rapidly than the primary response evoked by skin stimulation. It decreases progressively in amplitude with continuous 200-Hz iterative stimulation, and recovers slowly at the end of stimulation. The primary response evoked by contralateral forepaw and hindpaw stimulation is highly localized, being entirely within the antidromic response distribution. The antidromic response in laboratory rats consists of a small, surface-positive component analogous to the pure antidromic response of cats, and of a large, surface-positive response analogous to that found in wood-chucks, rabbits, opossums and slow lorises. It is argued that this latter response results from synaptic action in pyramidal tract axon collaterals, probably onto cells in layer V, rather than being a purely antidromic event.

ISSN:0006-8977    

DOI:10.1159/000316010

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Cerebellar afferents in 3-week-old normal and homozygous Weaver mutant mice were investigated using retrograde transport of horseradish peroxidase. Almost all afferents found in other mammals were demonstrated in both normal and mutant mice of this age. Labelling in the trigeminal nuclei in both mutants and normals was found only in cases in which the ansoparamedian or uvular lobules were included in the injection site, indicating that the projection domains of mossy fiber afferent systems retain their normal boundaries in the mutants despite a lack of normal synaptic partners. Thus the neurological signs which the Weaver exhibits from about the 10th postnatal day are unlikely to depend on primary or seondary losses of cerebellar afferents or on a breakdown of the gross topographic organization of these afferents.

ISSN:0006-8977    

DOI:10.1159/000118678

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Antiserum prepared against rat renal calcium-binding protein (CaBP) was used with the unlabeled antibody peroxidase-antiperoxidase (PAP) technique to localize the 28,000 molecular weight CaBP in the cerebellum of the bullfrog, Rana catesbeiana. Whole brains of premetamorphic tadpoles and adults were fixed in Bouin's solution for 2 or 24 h and embedded in paraffin. 8-μm parasagittal sections were prepared and treated by the PAP method. Purkinje cells of the cerebellum in tadpoles and adults were specifically stained for CaBP. In the premetamorphic corpus cerebelli, the stained Purkinje cells corresponded to the precociously developed Purkinje cells described previously. In the auricular lobe region of the cerebellum mature Purkinje cells were stained. In addition, smaller stained cells were seen. The latter were presumed to be immature Purkinje cells that would mature at the time of metamorphosis. Immunoblot procedure demonstrated cross-reactivity for the ranid brains in the 28,000 molecular weight region. This immunoreactive band comigrated with the immunoreactive band observed with purified rat renal CaBP. Although the exact functional significance of CaBP is unknown at this time, our immunocytochemical and immunological findings indicate that CaBP is an excellent marker for studies of Purkinje cell maturation.

ISSN:0006-8977    

DOI:10.1159/000118679

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Pigeons were trained to perform intensity, color and pattern tasks monocularly. After their training was completed, a unilateral electrolytic lesion was made either in the nucleus rotundus or in the nucleus opticus principalis thalami (OPT). The lesion was made in the trained hemisphere (contralateral to the trained eye) in half of the subjects and in the untrained hemisphere in the other half. After a 7-day recovery period the birds were retrained on the same tasks with the previously untrained eye. A rotundal lesion, on either side, resulted in the loss of interocular transfer of discrimination, whereas neither contralateral nor ipsilateral OPT lesions affected discrimination. These results suggest that the tectofugal visual pathway plays a crucial role in the interhemispheric transfer of visual information in pigeons.

ISSN:0006-8977    

DOI:10.1159/000118680

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

A neotropical treefrog, Smilisca sila, exhibits an unusual ability to synchronize its calling with that of neighbors such that calls often overlap temporally. Call playback experiments measured the latency to evoked calling in response to one-note and two-note mating calls. Approximately one-half of the responses overlapped the one-note stimulus call, while 20% overlapped the two-note stimulus call. Minimum response latencies were 55 ms and 78 ms in response to the one-note and two-note calls, respectively. These data were used to evaluate the efficacy of proposed neural pathways involved in call recognition and production. Based on neural and behavioral latencies presented in those studies, it is suggested that the proposed pathways for call recognition and production might not accommodate the short behavioral latencies in S. sila. One possible explanation for this discrepancy is that call detection is decoupled from call recognition, the former requiring a shorter neural pathway thus permitting a shorter behavioral latency.

ISSN:0006-8977    

DOI:10.1159/000118681

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Nine pigeons were trained to perform a simultaneous discrimination task with stimuli that were lateral mirror images, vertical mirror images and nonmirror images. All subjects acquired the discriminations rapidly and at approximately equal rates. Following training, bilateral stereotaxic lesions were made in either the visual wulst or ectostriatum, which are telencephalic components of the thalamofugal and tectofugal visual pathways, respectively. After surgery both groups were retrained to their preoperative performance levels or for a maximum of 140 sessions. The performance of the four subjects that received visual wulst lesions was only mildly and transiently impaired and was equally disrupted on each pattern discrimination. The performance of the five subjects that received ectostriatal lesions, however, was markedly and persistently impaired on all pattern discriminations. The impairment was most severe and sustained on the lateral mirror-image discrimination problem in all subjects. Only three of the five subjects with ectostriatal lesions reached their preoperative performance levels on the lateral mirror-image problem, whereas all subjects returned to their preoperative performance levels on the other problems. Possible reasons for this selective deficit in lateral mirror-image pattern discrimination are discussed in relation to interhemispheric pathways and the relative importance of the thalamofugal and tectofugal visual pathways in birds and in mammals.

ISSN:0006-8977    

DOI:10.1159/000118682

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000118683

出版商:S. Karger AG    

年代:1986

数据来源: Karger