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  • 1
    Electronic Resource
    Electronic Resource
    Segregation of functionally distinct axons in the monkey's optic tract (1988)
    [s.l.] : Nature Publishing Group
    Nature 331 (1988), S. 350-351 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Implants of dried gel-foam that had been previously saturated with horseradish peroxidase (HRP) were surgically inserted into one optic tract of five old-world monkeys, at varying deep-to-superficial locations (that is, removed from or near to the outer, pial, surface) within the optic tract. Such ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/331350a0
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  • 2
    Electronic Resource
    Electronic Resource
    Projection patterns of surviving neurons in the dorsal lateral geniculate nucleus following discrete lesions of striate cortex: implications for residual vision (1989)
    Springer
    Experimental brain research 75 (1989), S. 631-638 
    Details
    ISSN: 1432-1106
    Keywords: LGN ; Striate cortex ; Residual vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In four monkeys with long-standing partial ablation of the striate cortex pellets of horseradish peroxidase were placed in either the striate cortex immediately adjacent to the ablation, or in the extrastriate cortex of the ventral prelunate gyrus, i.e. in visual area V4. We examined the dorsal lateral geniculate nucleus to see whether surviving neurons, within the region that shows retrograde degeneration as a result of the cortical lesion, project to remaining striate cortex and/or to extrastriate cortex. Neurons labelled from extrastriate cortex were found throughout the degenerated region, whereas neurons labelled from striate cortex were confined to the border between the normal and degenerated region of the nucleus. This shows that isolated neurons found within the degenerated region survive striate cortex damage because they project to an extrastriate visual area, and not because their terminals depart from the otherwise strict topographic representation of the lateral geniculate nucleus on to striate cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249914
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  • 3
    Electronic Resource
    Electronic Resource
    Rearrangements in the retino-geniculate projections of rats following ablation of the superior colliculus in infancy (1985)
    Springer
    Experimental brain research 59 (1985), S. 372-381 
    Details
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Dorsal lateral geniculate nucleus ; Aberrant retinal projections ; Early brain damage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The superior colliculus was bilaterally or unilaterally ablated at different early postnatal ages in rats. When adult, each rat received a unilateral eye injection of Horesradish peroxidase to reveal the crossed and uncrossed retinal terminal fields within the dorsal lateral geniculate nucleus. Collicular ablation in the first seven days after birth, but not thereafter, produced a small hole or vacancy within the contralateral retinal terminal field which was occupied by an aberrant ipsilateral retinal terminal field. These rearrangements in the retino-geniculate projections occurred in the caudal quarter of the nucleus dorso-laterally just beneath the optic tract, solely ipsilateral to the ablated colliculus. Possible causes of the formation of these rearrangements are discussed, and similarities with other aberrant retinal projections following early damage to the visual system are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230917
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  • 4
    Electronic Resource
    Electronic Resource
    The relationship between GABA immunoreactivity and labelling by local uptake of [3H]GABA in the striate cortex of monkey (1986)
    Springer
    Experimental brain research 62 (1986), S. 89-98 
    Details
    ISSN: 1432-1106
    Keywords: [3H]GABA accumulation ; GABA immunostaining ; Co-localisation ; Visual cortex ; Inhibitory circuits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An antiserum to GABA was used in the macaque monkey to determine whether neurons that accumulate exogenously applied [3H]GABA in vivo are also immunoreactive for GABA. Following the injection of [3H]GABA into different laminae of striate cortex in two untreated animals and in one animal treated with amino-oxyacetic acid, selective accumulation of the labelled amino acid was demonstrated in perikarya by autoradiography. Radiographically labelled neurons (n, 519) and their unlabelled neighbours were tested in consecutive 0.5 μm thick sections by immunocytochemistry for GABA immunoreacitivity. Injection of [3H]GABA did not increase the number of neurons showing GABA immunoreactivity. On the contrary many of the cells that accumulated [3H]GABA were immunonegative. These neurons were mostly located in layers IVC and VA following [3H]GABA injection into layers II–III, and in layers upper III and II following injection into layers V and VI. A comparison of the position of these neurons with known local projection patterns in the striate cortex of monkey suggests that GABA-immunonegative neurons may nevertheless become labelled by [3H]GABA if most of their local axon terminals fall within the injection site. The interlaminar projection of GABA-immunopositive neurons, which probably contain endogenous GABA, could be deduced from the position of the [3H]GABA injection site that leads to their autoradiographic labelling. Although the present study confirmed our previous results on the interlaminar connections of neurons that accumulate [3H]GABA, it demonstrated that [3H]GABA labelling alone may not be a sufficient criterion to assess the GABAergic nature of neurons in the striate cortex of monkey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237405
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  • 5
    Electronic Resource
    Electronic Resource
    Large retinal ganglion cells in the rat: their distribution and laterality of projection (1986)
    Springer
    Experimental brain research 61 (1986), S. 375-385 
    Details
    ISSN: 1432-1106
    Keywords: Retinal ganglion cell ; Alpha cell ; Decussation ; Rodent visual system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distributions of the ipsilaterally and contralaterally projecting large ganglion cells in the retina of the rat were determined, using the retrograde transport of Horseradish peroxidase (HRP) following injections into one optic tract. Labelled large retinal ganglion cells occur throughout the contralateral retina and throughout the temporal crescent of the ipsilateral retina, but there is a noticeable decrease in their density in the contralateral retina's temporal crescent. This retinal region was identified in these same retinae by injecting a retrogradely transported flourescent tracer into the optic tract opposite that receiving the HRP. The density of large retinal ganglion cells increases in both the contralateral retina and the ipsilateral temporal crescent in the upper temporal periphery such that, together, these two populations of large cells combine to produce a peak density centred on the retinal representation of the visual field's vertical midline. This peak density of large retinal ganglion cells must therefore be further peripheral than the peak density for the total population of retinal ganglion cells, since all evidence indicates that the latter is positioned nasal to the vertical midline's representation. This was verified in one rat, in which the density distribution of the total population of retinal ganglion cells was determined and compared with the distribution of the large cell population. The results suggest that the rat possesses a specialized retinal focus of large ganglion cells for viewing the visual field directly in front of the animal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239526
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of pretectal and superior collicular lesions on binocular vision (1986)
    Springer
    Experimental brain research 63 (1986), S. 402-408 
    Details
    ISSN: 1432-1106
    Keywords: Mid-brain ; Binocular fixation ; Diplopia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Monkeys with mid-brain lesions involving the pre-tectum and superior colliculi often have an odd stare, as if the visual axes were parallel and the animal was looking into the distance. Such a visuo-motor abnormality could lead to double-vision for objects close to the animal. The experiments reported here were designed to test this hypothesis of diplopia in monkeys with combined bilateral ablations of the colliculi and frontal eye-fields (area 8). These animals performed better on a task of visually-guided reaching, and in a series of visual pattern discriminations, when they viewed stimuli monocularly rather than binocularly. Monkeys with other cortical lesions showed no such monocular superiority. We propose that an abnormality of vergence eye movements provides a simple explanation for some of the so-called perceptual impairments that follow damage to the mid-brain visual pathways in monkeys
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236859
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  • 7
    Electronic Resource
    Electronic Resource
    Contrast sensitivity in rats with increased or decreased numbers of retinal ganglion cells (1988)
    Springer
    Experimental brain research 70 (1988), S. 513-526 
    Details
    ISSN: 1432-1106
    Keywords: Rats ; Superior colliculus ; Enucleation ; Contrast sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Contrast thresholds were measured electrophysiologically on striate cortex in normal rats and in rats in which either the superior colliculi were removed bilaterally or unilaterally at 5 days of age, or one eye was removed on the day of birth. Despite the fact that the collicular ablation leads to the degeneration of more than half the retinal ganglion cells, contrast sensitivity was normal in this group, with the possible exception of sensitivity at very low spatial frequencies below 0.1 c/deg. The result is strong evidence that retinal ganglion cells which project to thalamus as well as to mid-brain escape the degenerative effects of neonatal mid-brain lesions. The contrast sensitivity of neonatally operated one-eyed rats was significantly and substantially better than that of normal rats tested monocularly. The increased sensitivity was greatest in the cortex ipsilateral to the remaining eye. This supernormal sensitivity is presumably related to the increase in the number of ganglion cells in the remaining eye, especially those projecting ipsilaterally from the temporal retina and which show a five-fold expansion of their terminal zone in the thalamus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00247599
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  • 8
    Electronic Resource
    Electronic Resource
    The nature of the visual discrimination impairment after neonatal or adult ablation of superior colliculi in rats (1986)
    Springer
    Experimental brain research 61 (1986), S. 403-412 
    Details
    ISSN: 1432-1106
    Keywords: Rats ; Superior colliculus ; Infant vs adult lesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The superior colliculi were removed in rats at either one or five days of age or in adulthood. Seven months later they were tested on four successively presented two-choice intensity discriminations. The intensity difference between the discriminanda was reduced across the four problems to encourage choice by comparison. The purpose was to establish whether impoverished scanning is a feature of rats with collicular lesions and whether the age at which the lesion is incurred is important. The number of door-push and approach errors made in reaching criterion were used as measures of performance and the number of head-scans during acquisition was counted. The results provide no evidence that either one- or five-day operated rats exhibit sparing or recovery of the ability to scan discriminanda since all operated animals were impaired. Furthermore, novel retinal projections, present in one-day operated animals, fail to mediate such sparing. Finally, the results did not demonstrate a selective increase in approach errors following collicular lesions and were therefore inconsistent with the view that the impairment is one of visually-guided locomotion. It is concluded that visual discrimination learning is impaired following collicular lesions in circumstances where scanning of discriminanda is required for efficient performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239529
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  • 9
    Electronic Resource
    Electronic Resource
    A comparison of the effects of superior collicular ablation in infant and adult rats (1985)
    Springer
    Experimental brain research 59 (1985), S. 302-312 
    Details
    ISSN: 1432-1106
    Keywords: Rats ; Infant vs. adult lesions ; Tectum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rats sustaining damage to the superior colliculus in infancy or adulthood and sham-operated controls were tested on two tasks requiring visual orienting to ‘unexpected’ and ‘expected’ stimuli, respectively. Experiment 1 measured the distracting effect of novel visual and auditory stimuli presented while the animals traversed a familiar runway. Control rats oriented to the distracting stimulus and had lengthened running times on the trials where it was presented. Rats with lesions of the superior colliculus were less distracted by the appearance of unexpected stimuli than sham operated controls but the severity of this effect depended on modality, and on age at operation. Experiment 2 examined the same animals' ability to detect and respond to a small and expected light that appeared at randomly determined positions around the perimeter of a chamber while the rat was at the centre. Filmed records and analyses of response latencies and errors showed that at low stimulus intensities, the active exploration shown particularly by infant-operated animals resulted in performance that was superior to that of adult-operated animals and, at least in terms of error rate, sham-operated controls. It is concluded that unusual behavioural strategies can explain all the differences between the animals operated at different ages. There was no evidence that novel projections from the retina were responsible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230910
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  • 10
    Electronic Resource
    Electronic Resource
    Effects on visual search of lesions of the superior colliculus in infant or adult rats (1987)
    Springer
    Experimental brain research 65 (1987), S. 465-470 
    Details
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Lesion ; Visual search ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The superior colliculus was removed from rats at either one or five days of age or in maturity. Four months later they were tested on two versions of a visual search task. Experiment 1 required animals to retrieve food pellets concealed in a depression in the top of identical narrow pillars arranged in an arena. Rats with lesions of the superior colliculus, regardless of the age at operation, showed a large number of ‘return’ errors compared with sham-operated controls. Return errors were defined as occasions on which the animal returned to pillars that had previously been visited on that trial, before every pillar had been visited at least once. Experiment 2 compared the ability of infantand adult-operated animals to detect and locate a single, baited white pillar in an array of black ones. There were no group differences in response latencies to targets presented in the rostral visual field (within 40° of the midline). However, animals operated on in adulthood or at 5 days of age were slower than both sham-operated animals and animals operated on at one day of age in their responses to more peripheral targets. The latter two groups were indistinguishable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236320
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