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  • 1
    Electronic Resource
    Electronic Resource
    Intrinsic inter- and intralaminar connections and their relationship to the tonotopic map in cat primary auditory cortex (1991)
    Springer
    Experimental brain research 86 (1991), S. 527-544 
    Details
    ISSN: 1432-1106
    Keywords: Auditory cortex ; Interlaminar connections ; Isofrequency bands ; Corticocortical connections ; Biotinylated PHA-L ; Anterograde tracing ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Small iontophoretic injections of the lectin, Phaseolus vulgaris leucoagglutinin (PHA-L), were made into different layers of the primary auditory cortex (AI) of cats. Injections in layer I labeled two types of morphologically distinct fibers in layer I as well as a smaller number of axons in layers II and III. Layer II injections labeled descending axons that produced a dense plexus of terminal fibers in layers I–III of both AI and adjacent auditory fields. Injections in layer III also labeled a dense plexus of axon collaterals at the junction of layers V and VI and labeled patches of terminal fibers in both AI and adjacent auditory fields. These were densest in layers I–III but usually extended into layers IV and V as well. The patches were partly formed by axon collaterals of layer III pyramidal cells that traveled for over 4 mm in the gray matter. Injections confined to layer IV labeled axons in all layers of the cortex but none of these axons appeared to reach the white matter. The axons spread laterally in layer IV and up into the superficial layers and ramified especially layer I. Injections in layers V and VI labeled axons in all layers of the cortex but these were densest in the deep layers where labeling was fairly homogeneous. In the upper layers the labeling was arranged in semi-discrete patches. Large injections involving layers I–III were studied in tangential sections. Between 3 and 8 patches of terminal labeling were observed in AI and these were mainly arranged in a band with its long axis aligned approximately in the dorsoventral direction. However dense patches of terminal labeling also occurred both anterior and posterior to the injection site. In selected experiments portions of the tonotopic map in AI were mapped by single unit recording and subsequently the map was related to patches of anterogradely labeled fibers that surrounded injections of PHA-L. Rows of dorsoventrally oriented patches were among cells with a similar best frequency to those in the injection site. However patches located anterior or posterior to the injection site were among cells with higher or lower best frequencies. Two injections of PHA-L close together produce different patterns of labeling. One of the injections usually produces one or more patches that has no correlate among the patches of fibers labeled by the adjacent injection. This is clearest when one of the injections is made with biotinylated PHA-L that can be visualized directly without the use of primary antibodies. Thus the intrinsic connections of AI arising from nearby cylinders of neurons are not homogenous and clusters of cells can be identified by their unique pattern of connections within AI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230526
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Callosal connections of the ferret primary auditory cortex (1997)
    Springer
    Experimental brain research 116 (1997), S. 367-374 
    Details
    ISSN: 1432-1106
    Keywords: Key words Binaural bands ; Wheat germ agglutinin-horseradish peroxidase ; Cortical columns ; Auditory system ; Corpus callosum ; Ferret
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The callosal connections of ferret auditory cortex were studied by making multiple injections of wheat germ agglutinin-horseradish peroxidase into the middle ectosylvian gyrus or by packing crystals of horseradish peroxidase into the transected corpus callosum. The primary area (AI) had strong callosal connections that arose from somata mainly located in layer III. Other layers contained sparsely distributed cells that projected across the midline. The projecting cells occurred over the whole extent of AI but were not homogeneously distributed in layer III. The axons from these cells terminated mainly in the upper layers of the contralateral cortex, where they converged onto three discrete bands. The three elongated bands lay in a dorsoventral orientation, parallel to the tonotopic axis. They were slightly curved and had a fairly uniform width. The posterior band had a width of about 200 μm, while the anterior and middle bands were more variable and had widths of 300–800 μm. The centre-to-centre distance between the posterior and middle bands was 520 ± 60 μm and for the anterior to middle bands was 620 ± 210 μm. The retrograde labelling produced by the same injections showed that the cell bodies had a higher density in the terminal bands than in the intervening spaces. The bands of dense callosal connections appear to correspond to the binaural summation columns, which have been clearly demonstrated in the ferret, but direct evidence of this will need to be sought in a future study. The discrete nature of the callosal bands in the ferret appears to make it a suitable species for studying the relationship between callosal terminals and those arising in other areas of the brain and for clarifying the possible existence of separate functional systems within the auditory cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005764
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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