摘要:

AbstractTwenty‐seven medial lemniscal axons were traced to their terminations in the thalamic ventrobasal complex of monkeys, following injection of horseradish peroxidase into the lemniscus at midbrain levels.Most axons had terminal ramifications at one horizontal level in the ventrobasal complex. All terminations were focal, many were anteropos‐teriorly elongated, though none were sufficiently long to occupy more than one‐third to one‐half of the anteroposterior extent of the VPLc nucleus. All terminal ramifications were compressed sagittally into a slab 200–300 μm wide. There was modest overlap in the terminal territories of adjacent labelled axons and, as judged light microscopically, only a small amount of convergence onto the vicinities of single cells.Axons terminating selectively in the anterodorsal shell or central core of VPLc could be identified. In the anterodorsal shell (of neurons responding to stimulation of deep tissues) axons tended to terminate either in the part projecting to area 3a or in that projecting to areas 3a and 2 of the cortex. In the central core (of neurons responding to cutuneous stimulation and projecting to areas 3b and 1) larger ramifications were present in its center and smaller ramifications in its ventral part.A few axons had terminal ramifications at two dorsoventral levels in the cutaneous core; others had terminations in both the dorsal deep shell and the cutaneous core. In both cases, one ramification was always smaller than the other.The termination of lemniscal axons at defined foci instead of along the dorsoventral extent of the representational lamellae of the ventrobasal complex has implications for the nature of the body representation in the nuclei. Their tendency to be focal implies that not all members of an anteropos‐teriorly elongated rod of place‐and‐modality‐specific ventrobasal cells that project their axon to a single column in the somatic sensory cortex receive afferent inputs from the sam

ISSN:0092-7317    

DOI:10.1002/cne.902150102

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

年代:1983

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase was injected into various levels of the spinal cord of turtles(Pseudemys and Chrysemys), lizards(Tupinambis, Iquana, Gekko, Sauromelus, and Gerrhonotus), and a crocodilian(Caiman).The results suggest that brainstem reticulospinal projections in limbed reptiles rival mammalian reticulospinal systems in complexity. The reptilian mye‐lencephalic reticular formation can be divided into four distinct reticulospinal nuclei. Reticularis inferior pars dorsalis (RID) contains multipolar neurons which project bilaterally to the spinal cord. Reticularis inferior pars ventralis (RIV), which is only found in lizards and crocodilians, contains fusiform neurons with horizontally running dendrites and it projects ipsi‐laterally to the spinal cord. Reticularis ventrolateralis (RVL), which is found only in teiid lizards, contains triangular neurons whose dendrites parallel the ventrolateral edge of the brainstem and it projects ipsilaterally to the spinal cord. The myelencephalic raphe (Ral) varies considerably. Ral of turtles contains large reticulospinal neurons which form a continuous population with more laterally situated RID cells. Ral of lizards contains a few small reticulospinal neurons. Ral of the crocodilianCaimancontains giant reticulospinal neurons with laterally directed dendrites.The caudal metencephalic reticular formation of reptiles can be divided into two distinct reticulospinal nuclei. Reticularis medius (RM) contains large neurons with long, ventrally directed dendrites; it projects ipsilaterally to the spinal cord. Reticularis medius pars lateralis (RML) contains small neurons with laterally directed dendrites; it projects contralaterally to the spinal cord.The rostral metencephalic and caudal mesencephalic reticular formation of reptiles can be divided into three distinct reticulospinal nuclei. Reticularis superior pars medialis (RSM) consists mostly of small, spindle‐shaped neurons which project bilaterally to the spinal cord. In the lizardTupinambis, however, large multipolar, ipsilaterally projecting neurons are occasionally seen in RSM. Reticularis superior pars lateralis (RSL) contains large, bilaterally projecting neurons with long, ventrolaterally directed dendrites. RSL in lizards can be divided into a dorsomedial portion, which projects ipsilaterally to the spinal cord, and a ventrolateral portion which projects contralaterally. The locus ceruleus‐subceruleus field (LC‐SC) contains small spindle‐shaped neurons which project bilaterally to the spinal cord.Labeled reticulospinal neurons were also observed in the rostral metencephalic raphe (RaS) of the turtle brainstem. These cells are small, spindle‐shaped neurons which resemble the small cells of the adjac

ISSN:0092-7317    

DOI:10.1002/cne.902150103

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe organization and functional properties of interneurons in the flight system of the locust,Locusta migratoria, were investigated by using intra‐cellular recording and staining techniques. Interneurons were found to be distributed within the three thoracic and the first three abdominal ganglia, and they could be subdivided into three organizational categories: (1) members of one of two serially homologous groups controlling either the forewing or the hindwing, (2) unique individuals with no known homologues in other ganglia, and (3) members of a set of serial homologues in the metathoracic and first three abdominal ganglia. Interneurons in the last two categories influenced both forewing and hindwing motoneurons in a similar manner. Thus interneuronal organization is not characterized by two distinct homologous groups of interneurons for the separate control of forewing and hindwing motor activity.Flight interneurons may also form two separate functional categories: (1) those making short latency connections to motoneurons (premotor interneurons), and (2) those which reset the flight rhythm when depolarized by brief current pulses (pattern generator interneurons). None of the ten premotor interneurons we identified influenced the flight rhythm when depolarized and none of the three groups of pattern generator interneurons were found to form short latency connections with motoneurons. This separation of function may allow phase‐shifts in motor output for flight control without changes in wingbeat frequency. Pattern generator interneurons influence motor output to both forewings and hindwings. Thus we conclude that the flight rhythm is generated in a distributed neuronal oscillator driving both pairs of wings.The organization of flight interneurons is considerably more complex than predicted from existing models of the flight system, or anticipated from the relative simplicity of the motor output. Our finding of homologous sets of interneurons in the abdominal ganglia supports the notion that insect flight evolved from a behavior using appendages distributed along the thorax and the abdomen. Thus the organization of flight interneurons may reflect an interneuronal system which controlled the behavior from which flight evol

ISSN:0092-7317    

DOI:10.1002/cne.902150104

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

年代:1983

数据来源: WILEY

摘要:

AbstractEarlier studies have shown that visual function in skate is subserved solely by the rod mechanism and that the retina of this elasmobranch contains only rod photoreceptors. Nevertheless, the skate retina is capable of responding to levels of illumination that extend well into the photopic range, and we have detected in histological sections (usually from younger animals) small, proximally displaced, conelike photoreceptors which possibly represent another class of visual cell. However, ultrastructural and histochem‐ical studies showed that the membranous discs of the outer segments of these cells were isolated from the plasma membrane, and that their synaptic terminals appeared immature and unlike those usually associated with cone receptors. In addition, the pattern of incorporation of3H‐fucose, as revealed by radioautography, was similar for both the rods and the smaller visual cells; i.e., the label was concentrated along the basal discs of the outer segment. When we examined the disc‐shedding behavior of the visual cells in skates entrained for 2 weeks or longer to a 12‐hour light: 12‐hour dark cycle, enhanced phagocytic activity was seen only following light onset; there was no significant increase following light offset. On the available evidence, it seems reasonable to conclude that the small visual cells are rods that have recently differentiated, and are growing and being incorporated into the photoreceptor layer of t

ISSN:0092-7317    

DOI:10.1002/cne.902150105

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

年代:1983

数据来源: WILEY

摘要:

AbstractA combination of electrophysiological and anatomical techniques was used to determine the sites of termination of olfactory projections to the thalamus and the distribution of the cells of origin of these projections within the olfactory cortex. Following electrical stimulation of the olfactory bulb, short‐latency unit responses were recorded not only in the central segment of the mediodorsal thalamic nucleus but also in the ventral and anterior parts of the submedial thalamic nucleus. Responses were not obtained in the ventral or lateral parts of the mediodorsal nucleus, in the dorsal part of the submedial nucleus, or in the intralaminar nuclei between the mediodorsal and submedial nuclei.The cells of origin of the projection were identified by making injections of horseradish peroxidase conjugated to wheat germ agglutinin (HRP*WGA) into the thalamus and examining the olfactory cortex for retrogradely labeled cells. Following injections into the mediodorsal nucleus, labeled cells were found in the polymorphic cell zone deep to the olfactory tubercle, in the ventral endopiriform nucleus deep to the piriform cortex, and in an equivalent position deep to the periamygdaloid and lateral entorhinal cortices. After injections into the submedial nucleus, a smaller number of labeled cells were found in similar locations, except that they were restricted to the rostral olfactory cortical areas and were not found deep to the lateral part of the piriform cortex. Retrogradely labeled cells and anterogradely labeled axons were also found in the lateral orbital and ventral agranular insular areas of the prefrontal cortex with injections into the mediodorsal nucleus, and in the ventrolateral orbital area with injections into the sub‐medial nucleus.Anterograde tracing experiments, using the autoradiographic method, have confirmed these results. Injections of 3H‐leucine deep to the junction between the anterior piriform cortex and the olfactory tubercle label axons in both the central segment of the mediodorsal nucleus and the ventral part of the submedial nucleus, while injections deep to the posterior piriform cortex label axons in the mediodorsal nucleus only. Within the mediodorsal nucleus, the projection also appears to be organized so that fibers which arise more rostrally terminate ventrolaterally in the central segment, while fibers which arise more caudally terminate more dorsomedially.These results indicate that there is a substantial and possibly dual thalamocortical mechanism available for processing of olfactory st

ISSN:0092-7317    

DOI:10.1002/cne.902150106

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

年代:1983

数据来源: WILEY

摘要:

AbstractSuperior vestibular neurons were penetrated with horseradish perox‐idase (HRP)‐loaded glass microelectrodes in anesthetized cats. Responses to electrical stimulation of the oculomotor complex and the vestibular nerves were characterized and selected neurons were injected with HRP. Neurons antidromically activated by oculomotor complex stimulation were generally monosynaptically excited by the ipsilateral vestibular nerve. Notable was the absence of strong commissural inhibition by stimulation of the contra‐lateral vestibular nerve. Light microscopy of antidromically identified injected cells demonstrated that these cells are predominantly located at the central levels of the superior vestibular nucleus along the incoming vestibular nerve fibers but a few are found at more caudal levels. Cell bodies, elongated or pyramidal, are mainly medium‐sized to large (30–50 μm). Dendritic trees extend in a plane at an acute angle to the collaterals of the vestibular nerve fibers. Dendrites remain within the nuclear territory and generally display an isodendritic branching pattern. Dendritic spines and appendages are mainly distributed on secondary and distal dendrites. A few terminal enlargements similar to growth cones are observed in these neurons.Axons of these neurons project rostrally via the medial longitudinal fasciculus, while a minor projection via the brachium conjunctivum is also found. Axon collaterals, when present, originate in the nucleus itself and in the pontine reticular

ISSN:0092-7317    

DOI:10.1002/cne.902150107

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

年代:1983

数据来源: WILEY

摘要:

AbstractSuperior vestibular neurons were penetrated with horseradish perox‐idase (HRP)‐loaded glass microelectrodes in anesthetized cats and identified electrophysiologically following electrical stimulation of the vestibular nerves and oculomotor complex. Neurons that were not antidromically activated from the oculomotor complex were stained by intracellular injection of horseradish peroxidase.Three types of neurons are identified according to their initial axonal trajectories into the cerebellum, the dorsal pontine reticular formation, or the brachium conjunctivum. Ipsilateral vestibular nerve input to all neurons is primarily monosynaptic and excitatory, whereas the contralateral is inhibitory.The neurons are located in the periphery of the superior vestibular nucleus. Soma diameters range from 20.5 μm to 44 μm. Most neurons exhibit globular and ovoid cell bodies. The dendritic arbors are intermediate between iso‐ and allodendritic branching patterns. The few spines and dendritic appendages present are distributed mainly distally on the dendrites. Soma size does not correlate with axon diameter, number of dendrites, or dendritic terr

ISSN:0092-7317    

DOI:10.1002/cne.902150108

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

年代:1983

数据来源: WILEY

摘要:

AbstractTectal projection neurons were labeled by retrograde transport of horseradish peroxidase (HRP) or cobaltic‐lysine. The tracer substances were delivered iontophoretically or by pressure injection or diffusion into various regions of the brain or spinal cord. Histochemical procedures allowed identification of labeled cells projecting to the injected regions. Many neurons were filled with cobaltic‐lysine, resulting in a Golgi‐like staining.After cobalt injections in the diencephalon most of the labeled cells, identified as small piriform neurons, were located in layer 8 of the tectum. Two types of small piriform neurons were distinguished. Type 1 neurons have flat dendritic arborizations confined to lamina D, while the dendrites of type 2 cells may span all of the superficial tectal strata. In smaller numbers large piriform, pyramidal, and ganglionic cells of the periventricular tectal layers were labeled after diencephalic injections.Rhombencephalic cobalt and HRP injections labeled cells whose axons form the tectobulbospinal tract. The neurons most frequently labeled were large ganglionic cells. Ipsilaterally, the majority of their somata were located in layer 7, and their dendrites arborized mainly in lamina F. Con‐tralaterally, labeled ganglionic cell somata occupied the top of layer 6, and most of their dendritic end‐branches entered lamina B. The possible functional significance of this anatomical arrangement is discussed.After tectal cobalt injections the topography of the tectoisthmic projection and the terminals of tectal efferent fibers in the diencephalon and brainstem were observed. It is concluded that the organization of frog tec‐tofugal pathways is very similar to that

ISSN:0092-7317    

DOI:10.1002/cne.902150109

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

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902150101

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

年代:1983

数据来源: WILEY