摘要:

AbstractInputs from the somatosensory cortex to the motor cortex have been proposed to function in learning of motor skills. In an attempt to analyze how these somatosensory inputs were processed in the motor cortex, neurons in the superficial layer of the cat motor cortex were classified into three groups on the basis of synaptic responses elicited by intracortical microstimulation (ICMS) of area 2. ICMS was delivered through seven electrodes implanted in area 2. When ICMS through one of the sevn sites produced a response that was greater than 50% of the response produced by stimulating the seven sites at time, the site was called a “dominant” site. Type I cells were those that had a dominant stimulation site and showed a constant response latency when examined by a double shock test. Type II cells were those that had a dominant site but displayed a variable latency. Type III cells had no dominant site and showed a variable latency. Latency of type I responses was 1.2–2.6 milliseconds, which was much shorter than that of type II and type III responses.Seventy‐nine neurons in layers II/III of the motor cortex, which responded to ICMS in area 2, were stained by intracellular injection of biocytin. From the presence of an apical dendrite and rich spines on the dendrites, 23 type I, 21 type II, and 15 type III cells were classified as pyramidal cells. Type II pyramidal cells were located more superficially than type I and type III pyramidal cells. On the basis of the absence or sparseness of dendritic spines, three type I and four type II cells in layers II/III were classified as nonpyramidal cells. These cells consisted of five small multipolar cells in layer II and a large multipolar cell and a small bitufted cell in layer III. The remaining 11 cells were not classified because of insufficient staining.Since type I and type II cells are considered to represent monosynaptic and polysynaptic responses to stimulation of area 2, respectively, information flow from type I cells to more superficially located type II cells is presumed in layers II/III of the motor cortex. Type III responses suggest tye presence of a convergent flow of impulses inside of and/or between areas 2 and 4. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903450202

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractConnections between motor cortical neurons receiving somatosensory inputs from area 2 and large pyramidal cells in layer V were examined in the cat via intracellular injection of biocytin and immunohistochemistry of nonphosphorylated neurofilament proteins (npNFP). Biocytin was injected into pyramidal cells in layers II/III of the motor cortex that responded monosynaptically and polysynaptically to microstimulation of the somatosensory cortex and subsequently stained black by the avidin‐biotinylated preoxidase complex method with diaminobenzidine (DAB) and nickel. By using a monoclonal antibody SMI‐32 and a modified peroxidase‐antiperoxidase method with Tris‐aminophenylmethane (TAPM) andp‐cresol as a chromogen, pyramidal cells in layers III and V of the motor cortex were stained red for npNFP. In particular, all the large pyramidal cells in layer V, Betz cells, displayed intense npNFP immunoreactivity not only in the perikarya but also in the dendrites.Double staining with DAB/nickel and TAPM/p‐cresol showed that biocytin‐filled axon varicosities of the pyramidal cells, which were thought to receive monosynaptic inputs from area 2, made contacts with npNFP‐positive dendrites in layers I‐III around the biocytininjected cell and in layers V‐VI beneath the cell. The present results suggest that the corticocortical input from area 2 to pyramidal cells in layers II/III of the motor cortex is transferred to layer V pyramidal cells, including Betz cells, as well as to neighboring layer II/ III pyramidal cells. Since tetanic stimulation of the somatosensory cortex reportedly produces long‐term potentiation in layer II/III cells of the motor cortex, it seems reasonable to assume that a given area of the somatosensory cortex can produce a long‐lasting change in the activity of a given group of output cells in the motor cortex.

ISSN:0092-7317    

DOI:10.1002/cne.903450203

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe goal of the present study was to clarify whether the primary motor cortex (Ml) and the supplementary motor cortex (SMA) both receive, via the motor thalamus, input from cerebellar and basal ganglia output nuclei. This is the first investigation that explores the problem by direct comparison, in the same animal, of thalamic zones that (1) project to M1 and SMA and (2) receive cerebellar‐nuclear (CN) and pallidal (GP) afferents. These four zones were mapped in two monkeys by means of two retrograde tracers for M1 and SMA injections and of two anterograde tracers for CN and GP injections. All injections were performed under electrophysiological control (microstimulation and multiunit recordings). Injections in cortical areas were restricted to the hand/arm representation; in the SMA, the tracer deposit was within the “SMA‐proper” (or “area F3”) and did not include its rostral extension (“pre‐SMA” or “area F6”). It was found that zones of all four types formed a number of highly complex patches of labeling that were usually not confined to one cytoarchitectonically defined thalamic nucleus. The overlap of clusters of labeled terminals and perikarya was evaluated morphometrically (area measurements) on a number of coronal sections along the anteroposterior extent of the motor thalamus. In line with previous studies, the thalamic territories innervated by CN and GP afferents rarely overlapped. However, zones projecting to M1 and/or to SMA included thalamic regions receiving CN as well as GP projections, providing the first evidence of such overlap from individual animals. The present observations support the previous conclusion from this laboratory (based on transsynaptic labeling) that the SMA receives, apart from its strong pallidal transthalamic input, a CN transthalamic input. These present findings that both M1 and SMA are recipients of transthalamic inputs from GP and CN thus support the concept that a mixed subcortical input consisting of weighted contributions from cerebellum, basal ganglia, substantia nigra, and spinothalamic tract is directed to each functional component of the sensorimotor cortex.

ISSN:0092-7317    

DOI:10.1002/cne.903450204

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThis report describes the distribution of thyrotropin‐releasing hormone (TRH) immunoreactivity in the brain of juvenile chinook salmon. TRH‐positive cell bodies are observed in the preoptic region of the diencephalon, in the supracommissural nucleus of the ventral telencephalon, and in the internal cellular layer of the olfactory bulb. Immunoreactive fibers occur in the olfactory bulb, the dorsal and ventral telencephalon and were particularly extensive in hypothalamic regions. TRH‐positive fibers also are observed in the optic tectum, posterior pituitary and the brainstem.The cell bodies in the preoptic area reside in the magnocellular preoptic nucleus. The position of these cell bodies along with the location of fibers in the hypothalamus and pituitary is consistent with the role of TRH as a hypothalamic releasing hormone. TRH‐positive cell bodies also occur in the supracommissural nucleus of the ventral telencephalon and in the internal cellular layer of the olfactory bulb. The cell bodies in the olfactory bulb may account for some of the fibers in the telencephalon, as there are TRH fibers in the olfactory tracts. The presence of TRH‐positive, fibers with bouton‐like swellings raise the possibility that the TRH peptide may act as a central neurotransmitter of neuromodulator. The results of this study suggest that TRH functions as a modulator of the pituitary activity in salmonids and that TRH is used as a transmitter or modulator in the olfactory system. The presence of TRH‐positive somata in the olfactory bulb and ventral telencephalon provides new insights into the comparative anatomy of the salmon telencephalon. © 1994 W

ISSN:0092-7317    

DOI:10.1002/cne.903450205

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractElectric fish generate an electric field, which they sense with cutaneous electroreceptors. Electroreceptors project topographically onto the medullary electrosensory lateral line lobe (ELL). The ELL of gymnotiform electric fish is divided into four segments specialized to detect different aspects of the electrosensory input; it is also laminated with separate laminae devoted to electroreceptive input, interneurons, projection neurons, and feedback input. We have utilized antisera to glutamic acid decarboxylase (GAD) and γ‐aminobutyric acid (GABA) to map the distribution of GABAergic cells and fibers in the ELL of the gymnotiform fish,Apteronotus leptorhynchus.Six types of GABAergic interneurons are found in ELL: Type 2 granular cells (granular layer) project to pyramidal cells; polymorphic cells (pyramidal cell layer) project to the non‐GABAergic type 1 granular cells; ovoid cells (deep neuropil layer) project bilaterally upon basilar dendrites of pyramidal cells; multipolar cells (deep neuropil layer) project bilaterally, probably to dendrites and neurons within the deep neuropil layer; and neurons of the ventral molecular layer and stellate cells (molecular layer) project to apical dendrites of pyramidal cells. GABAergic bipolar cells in the nucleus praeminentialis, a rhombencephalic structure devoted to feedback in the electrosepsory system, project in relatively diffuse fashion to pyramidal cells.We hypothesize that the various GABAergic circuits of the ELL can be correlated with specific functions: type 2 granular cells with adaptation, size of receptive field center, and gain; polymorphic cells and type 1 granular cells with regulation of surround inhibition; ovoid cells with common mode rejection; and neurons of the ventral molecular layer with adaptive gain control. The feedback GABAergic input from bipolar cells of n. praeminentialis to pyramidal cells may be part of a searchlight mechanism similar to the one postulated for thalamocortical systems. © 1994, Wiley‐Li

ISSN:0092-7317    

DOI:10.1002/cne.903450206

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractRetinal arbors in the tectum of living adult goldfish were imaged to determine whether the structural remodelling and refinement that occurs during development continues in adulthood. Individual optic fibers were labelled by making small injections of the lipophilic fluorescent dye DiI into ventral retina and viewing the exposed tectum through a fluorescence microscope equipped with a cooled CCD camera. Arbors were imaged in the living fish every 30–60 minutes for up to 7 hours.Normal adult goldfish showed no evidence of arbor remodelling during this period, though dynamic movements of varicosities present along axon segments were observed. For comparison, regenerating optic fibers were similarly imaged in fish that had undergone optic nerve crush 2–6 weeks previously. In these fish, dynamic structural changes were seen, including branch remodelling, extension and retraction of growth cones, and movement of varicosities. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903450207

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractUp to four morphologically distinct types of cross‐link are found between the stereocilia in the hair bundles of avian hair cells. These links are involved in mechanotransduction, force transmission across the bundle, and maintenance of hair bundle structure. They appear to be specialisations of the cell coat, but very little is known about their molecular composition. Chick inner ear tissues were therefore screened with a number of different lectins to find markers for specialisations of the hair bundle surface. One lectin, peanut agglutinin (PNA), which recognises the dissacharide Galβ1‐3GalNAc, was found to be a fairly selective marker for vestibular hair bundles, but it does not stain the stereocilia of auditory hair cells. The staining patterns observed with PNA in the vestibular system closely resemble those seen with a monoclonal antibody (mab) directed against a 275 kD component of the hair cell's apical surface known as the hair‐cell antigen (HCA). However, unlike PNA, the mab recognises both vestibular and auditory hair cells. A detailed comparison of the fluorescence staining patterns observed with PNA and the anti‐HCA mab indicates that binding sites for both ligands spatially codistribute on the surface of vestibular hair cells. The lectin and the anti‐HCA mab binding sites are both sensitive to trypsin treatment, and, with sections of the vestibular system, PNA pretreatment blocks subsequent anti‐HCA mab staining. Immunoelectron microscopy of vestibular hair bundles shows that PNA and the anti‐HCA mab both label a type of cross‐link known as the shaft connector. This link type is present on both auditory and vestibular hair bundles but reacts with PNA only in the vestibular system. The lectin jacalin, which has greater specificity for Galβ1‐3GalNAc than does PNA, also only labels vestibular and not auditory hair bundles. Although terminal sialic acid residues can block both PNA and jacalin binding, neuraminidase treatment does not unmask cryptic binding sites for these lectins on auditory hair cells but does reveal PNA and jacalin staining at a number of other locations in the inner ear. The results obtained with the lectins PNA and jacalin indicate that either the HCA or other components of the shaft links are differentially glycosylated in the vestibular and auditory epithelia of the bird. The functional significance for such a difference in glycosylation remains to be determined, but auditory and vestibular hair cells operate over different frequency ranges, and variations in glycosylation might confer different micromechanical properties on the hair bundles in these two systems. ©

ISSN:0092-7317    

DOI:10.1002/cne.903450208

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPrevious studies have shown that mammalian neuronal excitability increases with age, and this excitability may be related to development of Na+channels. In addition, evidence suggests that Na+channels are involved in the neuronal response to O2deprivation. Because of this, we wished to examine the pharmacologic properties and neuroanatomical distribution of the Na+channels in newborn brain and as a function of age. In this study, we used ligand‐binding techniques and autoradiography with3H‐saxitoxin (STX) to investigate Na+‐channel distribution in brains of rats at postnatal days 0, 3, 10, 21, 35, and 120. We found that (1) in each area examined, the Scatchard plots for STX binding were linear in both immature and mature brains in a ligand concentration range of 0.4–64 nM; the slopes, however, were different between areas or ages, with Kd values ranging between 1 and 5 nM; (2) STX‐binding density was more than tenfold lower in the rostral brain and cerebellum at birth than in the adult and increased with age; (3) binding density in the newborn brainstem was higher than in other areas such as the cortex and cerebellum, which is opposite to the distribution in the adult; and (d) the brainstem had a different developing pattern with an early‐peak density level (P10–21) and a lower adult level. We conclude that (1) there is a major type of STX‐binding site in specific brain areas in the developing brain; (2) binding affinity is higher, but density lower, at birth than in the adult, especially in the rostral brain; and (3) developmental profiles of Na+channels vary among brain areas with an early developmental time table in the brainstem and a later one in the cerebellum and rostral brain. © 1994

ISSN:0092-7317    

DOI:10.1002/cne.903450209

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe fiber course of the spinocerebellar tracts in the ventral and lateral funiculi of the cat spinal cord were studied by a new approach, making cordotomies at different spinal levels or lesions of the restiform body followed by injections of HRP or WGA‐HRP into the anterior cerebellar lobe. The retrogradely labeled axons showed characteristic distribution patterns related to the level and extent of the lesions. The results show the following. (1) The dorsal spinocerebellar tract (DSCT) originating ipsilaterally from the thoracic and upper lumbar segments, ascends in the dorsolateral fasciculus. It undergoes a dorsal shift during its rostral course. The tract is topically arranged and passes through the restiform body. (2) The ventral spinocerebellar tract (VSCT) arising contralaterally from lower thoracic, lumbar, and more caudal segments passes via the ventral funiculus and ascends in the ventrolateral fasciculus. This tract is also topically arranged. It makes a lateral and then a dorsal shift during its ascending course. The main portion of the VSCT enters the cerebellum via the superior cerebellar peduncle. A minor portion originating from the sacrococcygeal region enters via the restiform body. (3) The spinocerebellar fibers originating ipsilaterally from the cervical enlargement ascend in the lateralmost part of the lateral funiculus in the area between the dorsolateral and ventrolateral fasciculi. These fibers form two groups, one passing through the restiform body, the other through the superior cerebellar peduncle. (4) The spinocerebellar fibers originating contralaterally from the central cervical nucleus pass through the ventral funiculus and ascend in the lateralmost part of the lateral funiculus, mainly in the ventrolateral fasciculus. Most of the fibers seem to pass through the superior cerebellar peduncle. © 1994 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903450210

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPrevious studies from this laboratory have demonstrated that prenatal damage to vibrissae follicles results in significant increases in the brainstem representations of the remaining vibrissae as demonstrated by staining for the mitochondrial enzyme cytochrome oxidase (CO). Because CO is primarily a postsynaptic marker, these results do not directly address the question of whether there were changes in the projections of primary afferent fibers. To address this issue, we made intra‐axonal recordings from individual vibrissa‐related primary afferents in rats that sustained damage to vibrissae follicles oil embryonic day 17, and then injected horseradish peroxidase (HRP) into these axons to visualize their terminal arbors in the brainstem at the level of trigeminal subnucleus interpolaris (SpI). All vibrissae‐related primary afferents responded to deflection of one and only one vibrissa, and the terminal arbors of axons (N = 47) recovered from animals that sustained fetal peripheral lesions were significantly larger than those (N = 23) from normal rats. Fibers from fetally damaged animals had increased total fiber lengths and numbers of branch points. These results indicate that reduced competition among primary afferent axons results in increases in the terminal arbors that remain. These increases occur without any significant alteration in their peripheral receptive fields. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903450211

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY