摘要:

AbstractGanglion cells were counted and measured in whole mounts of the hamster's retina, stained with methylene blue. Their density varies between about 1,000/mm2at the edge of the retina to about 5–6,000/mm2in a broadarea centraliscentred about 1.9 mm (39 deg) directly temporal to the optic disk. Maps of cell density show a long horizontal extension of the dense area in the nasal direction. The sizes of ganglion cell somata fall into two main groups—small cells (5–11 μm diameter) and large cells (>11 μm), the latter including a small proportion of giant cells (>17 μm). All three classes of cells are maximal in density in the area centralis, although the small cells are relatively more numerous there. The total number of cells is about 114,000 with about 63,000 small cells and about 51,000 large. The optic nerve contains about 69,000 unmyelinated axons and about 50,000 myelinated axons, suggesting that the latter are the fibres of the larger ganglion cells. It is likely that the projections of the centres of the areae centrales of the two eyes are normally divergent in space; they are therefore not on “corresponding retin

ISSN:0092-7317    

DOI:10.1002/cne.901680402

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe visual cortex of the golden hamster was studied by means of multi‐unit and single unit recording, which revealed three separate retinotopic maps of the visual field in the posterior cortex. V1, corresponding to cytoarchitectonic area 17, has the contralateral temporal field represented medially, the central visual field (extending about 10 deg ipsilateral) represented laterally and the lower field anteriorly. The borders of the map, especially for the upper field, seem to be more restricted than the whole visual field available to the contralateral hemiretina: V1 probably does not represent the extreme periphery of the field. A large fraction of V1 has binocular input, for up to about 50 deg lateral to the vertical midline. There is a retinotopic reversal near the representation of the vertical midline where V1 meets V2 (corresponding to the more lateral “area 18a”). There is another retinotopic reversal at the extremity of the contralateral field representation, where V1 meets Vm (the medial visual area, corresponding to “area 18”) V2 and Vm each contain a reduced mirror image version of the map in V1. Almost all isolated single units in V1 have receptive fields that can be classified asradially symmetrical(60%) orasymmetrical(35%) Symmetrical fields have ON (13%) OFF (4%) ON‐OFF (30%) or “SILENT” (12%) central areas when plotted with flashing spots. There are minor but not striking differences between these groups in their field sizes, velocity preferences and so on. They almost invariably prefer moving to stationary stimuli but are not selective for orientation or direction of movement. Asymmetrical fields are of four types, three of which (type 1, 11% type 2, 17% and type 3, 2%) are orientation selective and resemble simple, complex and hypercomplex cells in the cat cortex. Some of these have direction as well as orientation preference. Axial movement detectors (5%) have a selectivity for one axis of motion, and thus prefer one orientation of edge, but respond equally well to movement of a spot. Vertical and horizontal orientation preferences, especially the latter, are much the most common. There is some evidence of clustering of cells according to receptive field type and, possibly, preferred orientation. Asymmetrical cells are, relatively, somewhat rarer in the deeper cortical layers. Within the binocular segment, fully 89%of cells are binocularly driven and the receptive fields are similar in the two eyes. Receptive fields tend to increase in size away from the area centralis representation and, in a complementary fashion, the magnification factor decreases from up to 0.1 mm/deg at the area centralis representation to about 0.02 mm/deg for the p

ISSN:0092-7317    

DOI:10.1002/cne.901680403

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe superior colliculus of the golden hamster was investigated by means of multi‐unit and single unit recording. The retinotopic map, which probably embraces a projection from the entire retina of the contralateral eye, is organized as in other vertebrates, with the central field represented in the anterior colliculus, the upper field medially. Magnification factor is fairly uniform and is about 0.02 mm/deg. There is a small binocular segment (where almost half of all neurones have input from the ipsilateral eye) in the anterior colliculus, representing the area of field around the area centralis and the anterior pole of the field. In the more superficial layers, units have small (about 10 deg diameter) receptive fields, which can be classified assymmetrical, responding to slow movement(80%)very fast movement detectors(6%)directional movement detectors(13%) andaxial movement detectors(%) In the deeper layers, below the stratum opticum, receptive field size increases dramatically and many cells habituate rapidly, making them sensitive only to new events. Receptive fields can be classified asmovement detectors(89%)directional movement detectors(10%) andaxial movement detectors(2%). All directional receptive fields, at least in the upper visual field, have an upward component in their directional preferences. About 42% of deeper layer cells have somatic sensory input, responding to light touch on the fur or whiskers of the contralateral half of the body. Some 5% of cells respond to complex sounds on the contralateral side of the animal. Many of these somatic and auditory cells also have visual receptive fields and, throughout the colliculus, there is general correspondence between the maps of visual space, auditory space and the body surface. This correlation may be important in the regulation of orienting behaviour towards novel peripheral stimul

ISSN:0092-7317    

DOI:10.1002/cne.901680404

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe dorsal openings in the myelin sheath of the median giant fiber (MGF) of the earthworm (Lumbricus terrestris L.) have been studied with electronmicroscopical and electrophysiological methods. The fine structure of the dorsal nodes (DN) resembles in many aspects the Ranvier nodes in vertebrate and crustacean nerve fibers. The nodal membrane directly faces the extracellular collagenous capsule of the ventral cord and displays a conspicuous electrondense undercoat. The myelin sheath of the paranode shows a characteristic differentiation into large desmosomal contacts.Recordings of the transmembrane and longitudinal surface currents along the dorsal side of the MGF during spike propagation support the view that an active inward current is restricted there to the DN. The inward current density in the DN reaches outstandingly high values similar to those measured in vertebrate nodes of Ranvier. The nodal activity can be blocked by application of tetrodotoxin and local anaesthetics. Local electrical stimulation of only one DN may suffice to elicit propagated actions potentials up and down the MGF. It is concluded that the dorsal nodes of the median giant fiber of the earthworm are highly specialized excitable structures mediating saltatory impulse conduction in these fibers.

ISSN:0092-7317    

DOI:10.1002/cne.901680405

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

年代:1976

数据来源: WILEY

摘要:

AbstractA topographic mapping of dopamine (DA)‐containing neurons and fibers was done mainly in the mesencephalon of the dog using the fluorescent histochemical technique of Falck and Hillarp. The extensive DA neuron system was found to be located in the ventral and medial regions of the mesencephalon; the pars compacta of the substantia nigra, the area almost corresponding to the ventral tegmental area of Tsai (hich consists of three groups, a caudal, the nucleus parabrachialis pigmentosus, a ventral, the nucleus paranigralis and a rostral, the caudal part of the nucleus tegmentalis gventralis of Tsai), the nucleus linearis of the raphe, and the mesencephalic reticular formation.The nigro‐neostriatal projection can be traced in the non‐treated or nialamide plus L‐dopa treated puppies without the lesion‐degeneration technique. Most fibers arising from these DA cell groups assemble at the prerubral area and ascend just dorsal to the medial forebrain bundle. Most fibers turn laterally at the lateral hypothalamus and enter the neostriatum via the dorsal part of the subthalamic nucleus, the zona incerta and the capsula interna. These findings show that the distribution of DA neurons and the nigro‐neostriatal pathway are fundamentally similar to those in other mammals. In this study, the processes of the nigral and paranigral DA neurons have been demonstrated to project into the pars reticulata

ISSN:0092-7317    

DOI:10.1002/cne.901680406

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe regeneration of large unmyelinated axons following transection of the spinal cord was studied in small larval sea lampreys (Petromyzon marinus) Individual Müller and Mauthner axons normally occur in a characteristic pattern in the spinal cord, but their positions were altered in the first several segments caudal to the lesion following regeneration. Müller axons grew out of the ventral tracts and sometimes looped back towards the brain or crossed the midline; maximum misdirection of axons occurred near the site of transection. Mauthner axons frequently bifurcated. Despite the aberrant and incomplete regeneration of axons, the larvae exhibited normal coordinated swimming, crawling, and coiling behavio

ISSN:0092-7317    

DOI:10.1002/cne.901680407

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

年代:1976

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901680401

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

年代:1976

数据来源: WILEY