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  • 1
    Electronic Resource
    Electronic Resource
    Topographic refinement of the regenerating retinotectal projection of the goldfish in standard laboratory conditions: a quantitative WGA-HRP study (1986)
    Springer
    Experimental brain research 63 (1986), S. 409-420 
    Details
    ISSN: 1432-1106
    Keywords: Retinotectal projection ; Regeneration ; Topography ; Goldfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The topographic precision of the regenerating retinotectal projection of the goldfish was studied between 18 and 524 days (at 20° C) after optic nerve cut, using retrograde transport of wheatgerm agglutinin conjugated to horseradish peroxidase (WGA-HRP) from one of two standardized tectal injection sites. All labelled ganglion cells in each flat-mounted retina were plotted individually, and their degree of dispersion was assessed by a statistical method based on distance to nearest neighbour. Labelled cells in normal fish were clustered tightly, covering on average only 1.3% of the retina. Early in regeneration (18–28 days) they were widely dispersed, covering up to 75.2%, and they did not begin to form recognizable clusters at appropriate sites until about 35 days after nerve cut. Between 18 and 70 days, the proportion of retina covered by labelled cells fell dramatically, halving about every 14 days. Between 70 and 524 days, no further reduction could be demonstrated: overall, clusters remained significantly larger than normal, though a few individual retinae were virtually normal. Several others, labelled from similar single injections between 56 and 524 days after nerve cut, showed pairs of cell clusters; a sign that persistent errors in topography are common. The very wide initial scatter of labelled cells reflects a striking lack of ‘goal-directedness’ in regenerative axon growth. Extensive branching in the optic nerve, tract and tectum, for which there is already evidence, must contribute to this. Though uptake of some WGA-HRP by non-synaptic growth cones cannot be ruled out, other evidence for mislocated functional synapses at early stages encourages us to favour ‘trial and error’ synapse formation as the likely basis of map refinement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236860
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Impaired refinement of the regenerated retinotectal projection of the goldfish in stroboscopic light: a quantitative WGA-HRP study (1986)
    Springer
    Experimental brain research 63 (1986), S. 421-430 
    Details
    ISSN: 1432-1106
    Keywords: Retinotectal projection ; Topography ; Correlated activity ; Goldfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The retinotectal projection of the goldfish was studied after regeneration of a cut optic nerve in stroboscopic light, constant light or diurnal light, with the lens removed to blur the retinal image. Retrograde transport of wheatgerm agglutinin, conjugated to horseradish peroxidase, from a standard tectal injection site was used to measure the topographic precision of the projection. The dispersion of labelled retinal ganglion cells, which reflects this precision, was assessed by a method based on distance to nearest neighbour. In normal fish treated similarly, these cells are known to be clustered into about 1% of the retinal area. Early in regeneration, however, they are widely dispersed. The projection map then re-acquires its precision over two or three months. In diurnal light, lens ablation had no effect on refinement of the regenerated map. Constant light increased the number of labelled cells but also had no significant effect on the map. But in stroboscopic light with a continuous pseudorandom pattern of flash intervals (average rate 4.8 Hz), much less refinement was seen. Even after 70–98 days of regeneration, labelled cells remained scattered, on average, over 20% of the retinal area. These retinae were indistinguishable by several criteria from those obtained in diurnal light after only 32–39 days. Mislocated axon terminals, which are largely eliminated during the second and third months of regeneration in diurnal light, evidently persist much longer in stroboscopic light that synchronizes ganglion cell activity across the retina. These results, like previous ones obtained by blocking the transmission of activity to the tectum, support a model of map refinement based on correlation in the firing of neighbouring neurons, which may have wide application within the nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236861
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A sharp retinal image increases the topographic precision of the goldfish retinotectal projection during optic nerve regeneration in stroboscopic light (1987)
    Springer
    Experimental brain research 68 (1987), S. 319-328 
    Details
    ISSN: 1432-1106
    Keywords: Retinotectal projection ; Topography ; Correlated activity ; Goldfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Locally-correlated neural activity appears to play a key role in refining topographically mapped projections. The retinotectal projection of the goldfish normally regains a high degree of spatial precision after regeneration of a cut optic nerve, but it fails to do so if retinal ganglion cell activity is blocked by tetrodotoxin, or if local correlations in activity are masked by the synchronizing effect of stroboscopic light. A sharp retinal image is not normally needed for a sharp map because local correlation occurs even in darkness or diffuse light, but the possibility that a sharp image might restore local correlation and sharpen the map in stroboscopic light, though taken into account in earlier experiments, has not previously been tested. The precision of the retinotectal map was therefore studied, by retrograde transport of WGA-HRP from a standard tectal injection site and quantitative analysis of the labelled ganglion cell distribution, after regeneration of a cut optic nerve for 83–84 days in either continuous stroboscopic light or normal diurnal light. The lens of the eye was either ablated to blur the retinal image or sham-operated. Two different strobe flash patterns used in previous experiments were also compared. With the lens ablated, stroboscopic light impaired map refinement significantly, confirming previous results. A rapid, irregular flash pattern averaging about 5 Hz was rather more effective than a regular 1 Hz pattern. With the lens intact, however, neither pattern had any detectable effect. The significant gain in precision resulting from a sharp retinal image in these circumstances suggests that common mechanisms could underlie both the internal refinement of the retinotectal map and such directly experience-sensitive processes as the experimental realignment of binocular maps in the frog Xenopus, and of auditory and visual maps in the barn owl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248798
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    Paper (German National Licenses)
    Fulltext
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