摘要:

Recent studies of the albino rat revealed extensive cutaneous somatosensory projections to the granule cell (GC) layer of the cerebellar hemispheres and the caudal vermis. These projections are organized asomatotopically in patchy mosaics. To determine whether similar projections exist in a marsupial, we explored the GC layer of the cerebellar cortex of anesthetized Virginia opossums using in-depth microelectrode micromapping and juxtathreshold cutaneous natural stimulation techniques.We found: (1) Somatosensory projections to the GC layer exist throughout the medio-lateral extent of the folia of the posterior lobe. The anterior lobe was not explored. (2) The submodality of most receptive fields was 'gentle-touch' cutaneous, but some were located in muscle, joint, or other deep-lying structures. (3) Peripheral projections to the GC layer are organized asomatotopically. (4) Adjacent body parts project disjunctively to nonadjacent GC regions, and the overall pattern of peripheral projections forms a patchy columnar mosaic. (5) Many body parts send projections to multiple loci. (6) Ipsilateral projections predominate. (7) Mechanoreceptors from face, snout, mouth and teeth activate the bulk of GC loci on crus I and crus II. The paramedian lobule receives projections from the entire ipsilateral body; the pyramis is activated from hindlimb and forelimb; the uvula from the upper arm and vibrissae. (8) Different folia have different combinations and arrangements of disjunctive patchy peripheral projections. (9) Individual differences in pattern of foliation and body representation occur.Except for differences in mosaic pattern and relative size of different projections, these findings are similar to those in rats and cats. These data suggest that somatosensory (especially cutaneous) inputs to the cerebellum are not only functionally significant, but that they exist widely among mammals.

ISSN:0006-8977    

DOI:10.1159/000118721

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Recent studies of the albino rat revealed extensive cutaneous somatosensory projections to the granule cell (GC) layer of the cerebellar hemispheres and the caudal vermis. These projections are organized asomatotopically in patchy mosaics. To determine whether similar projections exist in a marsupial, we explored the GC layer of the cerebellar cortex of anesthetized Virginia opossums using in-depth microelectrode micromapping and juxtathreshold cutaneous natural stimulation techniques.We found: (1) Somatosensory projections to the GC layer exist throughout the medio-lateral extent of the folia of the posterior lobe. The anterior lobe was not explored. (2) The submodality of most receptive fields was 'gentle-touch' cutaneous, but some were located in muscle, joint, or other deep-lying structures. (3) Peripheral projections to the GC layer are organized asomatotopically. (4) Adjacent body parts project disjunctively to nonadjacent GC regions, and the overall pattern of peripheral projections forms a patchy columnar mosaic. (5) Many body parts send projections to multiple loci. (6) Ipsilateral projections predominate. (7) Mechanoreceptors from face, snout, mouth and teeth activate the bulk of GC loci on crus I and crus II. The paramedian lobule receives projections from the entire ipsilateral body; the pyramis is activated from hindlimb and forelimb; the uvula from the upper arm and vibrissae. (8) Different folia have different combinations and arrangements of disjunctive patchy peripheral projections. (9) Individual differences in pattern of foliation and body representation occur.Except for differences in mosaic pattern and relative size of different projections, these findings are similar to those in rats and cats. These data suggest that somatosensory (especially cutaneous) inputs to the cerebellum are not only functionally significant, but that they exist widely among mammals.

ISSN:0006-8977    

DOI:10.1159/000316006

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The appearance of the fundus of the eye varies among the families of osteoglossomorph teleosts. In this study, four different fundal patterns were observed: (i) an anteroposterior (or horizontal) embryonic fissure with a septal falciform process (family Osteoglossidae); (ii) an embryonic fissure from the optic disc nasoventrally with a falciform process (family Arapaimidae); (iii) an embryonic fissure nasoventrally from the optic disc without a falciform process (family Hiodontidae); and (iv) neither an embryonic fissure nor a falciform process (families Notopteridae and Mormyridae). The distribution of these various forms among the osteoglossomorph fishes is consistent with the recent cladogram for the Osteoglossomorpha [Lauder and Liem, 1983] which was based on many characters. The embryonic fissure in adult Amia calva was also examined. Its existence in adult Amia, in most Osteoglossomorpha, and in many non-euteleostean bony fishes suggests that its persistence in the adult stage is a primitive trait of bony fishes, and its absence in the Notopteroidei (with the exception of Hiodon) is a derived condition.

ISSN:0006-8977    

DOI:10.1159/000118722

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Brains of western European hedgehogs, common tree shrews and common marmosets were perfused and stained according to Timm's method. The volumes of hippocampal components were determined with semiautomated quantitative techniques and compared by allometric methods. The results support previous findings that the size of the hippocampus in marmosets and tree shrews is about twice that of the hippocampus of the European hedgehogs of the same body weight. Three hippocampal substructures account for most of this progression. These are the hilus, the deep zone of the molecular layer of the area dentata, and CA1 (especially the cellular layer) of Ammon's horn.

ISSN:0006-8977    

DOI:10.1159/000118723

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

A lateral and a medial motoneuron in the brachial spinal cord of the leopard frog, Rana pipiens, were labeled by horseradish peroxidase applied to the ventral root. Their dendritic trees were traced, analyzed, and plotted using a computer-microscope system. Some dendrites of the medial motoneuron crossed the midline of the spinal cord, but no dendrites of the lateral motoneuron crossed the midline. Nevertheless, the total dendritic length of the lateral motoneuron exceeded that of the medial motoneuron. The peak number of dendritic branch segments of the medial motoneuron was located at a greater distance from its soma than that of the lateral motoneuron. Three-dimensional reconstruction and rotation of the dendritic trees revealed that the dendrites of the medial motoneuron had a greater rostrocaudal extent than those of the lateral motoneuron. When compared to reports of Golgi-impregnated motoneurons our results suggest that the HRP technique labels dendrites more completely. However, use of the HRP technique may introduce greater errors in the subsequent measurement of dendritic segments due to nonuniform tissue shrinkage.

ISSN:0006-8977    

DOI:10.1159/000118724

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Among marine teleost fishes, one neuroeffector pathway for sonic communication consists of two components: a peripheral effector organ that consists of a swimbladder with associated 'drum' muscles, and a swimbladder or 'sonic' motor nucleus (SMN) located at the junction of the spinal cord and the medulla oblongata. Here, the organization of the SMN is compared in two unrelated groups of teleosts, the midshipmen, Porichthys notatus and P. myriaster, and the sea robin, Prionotus carolinus. Horseradish peroxidase (HRP), used as a retrograde tracer, revealed the position of the SMN in each species. While the SMN is a fused midline structure in midshipmen, it is bilateral in sea robins. The functional significance of these two contrasting patterns of organization remains to be explored. A third study group included mormyrid freshwater electric fish, which are also sonic. Mormyrids were included in part because an earlier study identified androgen-binding cells at a brain level comparable to that of the SMN of marine fishes. Using HRP methods, a swimbladder motor nucleus was identified at the caudal pole of the vagal motor column. However, the nucleus in mormyrids lies dorsal to the fourth ventricle and central canal, not ventral as it does in midshipmen and sea robins. Its position corresponds to the steroid-concentrating cells identified in a previous study.

ISSN:0006-8977    

DOI:10.1159/000118725

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The command concept is the prevalent explanation for initiation of behavioral acts. We review the theory and methods used to show the existence of neurons mediating command function according to a major approach, which we call the Command Neuron Experiment (CNE). The CNE claims that command neurons are the cause of, or are necessary and sufficient for, the execution of behavioral acts. In the CNE, command function is unequivocally localized to a structure, the command neuron. However, findings from an archetypal command neuron, the Mauthner cell, produce anomalous interpretations in the context of this theory. This conflict is the cumulative result of faulty causal, operational and behavioral themes in the CNE. These themes readily lead to false-positive or false-negative conclusions when its operational procedures are applied. We conclude that this concept must be abandoned. In a companion paper we propose a re-formulation of command as a dynamic system property that is intermediate to neurophysiological and behavioral contexts and independent of methods, structures, or preconceived causal schemes.

ISSN:0006-8977    

DOI:10.1159/000118726

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The command concept is the prevalent explanation for initiation of behavioral acts. We review the theory and methods used to show the existence of neurons mediating command function according to a major approach, which we call the Command Neuron Experiment (CNE). The CNE claims that command neurons are the cause of, or are necessary and sufficient for, the execution of behavioral acts. In the CNE, command function is unequivocally localized to a structure, the command neuron. However, findings from an archetypal command neuron, the Mauthner cell, produce anomalous interpretations in the context of this theory. This conflict is the cumulative result of faulty causal, operational and behavioral themes in the CNE. These themes readily lead to false-positive or false-negative conclusions when its operational procedures are applied. We conclude that this concept must be abandoned. In a companion paper we propose a re-formulation of command as a dynamic system property that is intermediate to neurophysiological and behavioral contexts and independent of methods, structures, or preconceived causal schemes.

ISSN:0006-8977    

DOI:10.1159/000118727

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Action potentials of single afferent optic-nerve fibers were recorded in the superficial layers of the optic tectum of frogs. Horizontally moving chromatic stimuli were applied. A large range of stimulus velocities and 2 or 3 different wavelengths (450, 500 or 580 nm) of the moving monochromatic light spots were applied. The velocity functions of class 3 neurons varied only slightly with different chromatic stimuli. About half of the neurons of our sample exhibited directional selectivity to one or two of the wavelengths investigated. In some of these neurons the directional selectivity was found over the entire velocity range studied (0.046–18.4 degrees • s–1), while in others it was also dependent upon the angular velocity of the moving chromatic spot. Thus, a new principle of chromatic-signal processing exists in frogs which has so far not been described in other animals: an interrelation between :directional selectivity, chromatic composition of the stimulus and angular velocity. We concluded from these findings that the analytic properties of tectal cells, with respect to their possible function in pattern recognition, might receive insufficient description when the stimuli are restricted to the achromatic grey scale. On the other hand, we would like to stress that the peculiar properties of the retinal color channels in frogs, directional selectivity and different time constants of the recovery functions, contribute to the processing of black/white stimuli according to their shape, size and velocity, since the response to the leading edge and the trailing edge traversing the receptive field depends on these factors.

ISSN:0006-8977    

DOI:10.1159/000118728

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Completely aquatic marine mammals of the order Cetacea such as whales and dolphins have a reduced or absent olfactory system and neither a vomeronasal organ nor an accessory olfactory bulb. In comparison, seals, which are only partially aquatic, have olfactory and accessory olfactory systems including the vomeronasal organ. Thus, there seems to be a strong relation between the degree of adaptation to an aquatic environment and the degree of reduction in olfactory structures. Sirenians, such as manatees and dugongs, are another family of marine mammals which have secondarily adapted to a fully aquatic existence, yet there is dispute about the status of their olfactory structures. In the present study there was no evidence for a vomeronasal organ in the adult West Indian Manatee, Trichechus manatus. Additionally, the main olfactory system appeared quite rudimentary. These observations support the hypothesis that, in mammals, secondary adaptation to an aquatic environment leads to the reduction or loss of the olfactory senses.

ISSN:0006-8977    

DOI:10.1159/000118729

出版商:S. Karger AG    

年代:1985

数据来源: Karger