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  • 1
    Electronic Resource
    Electronic Resource
    Visual analysis and image motion in locomoting cats (2001)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 13 (2001), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: During locomotion, observers see a characteristic pattern of motion referred to as an optic flow field. To investigate how they make use of this pattern, we have developed a paradigm for testing visual function during locomotion. Foot placement was recorded while cats walked down an alley cluttered with a high density of small objects; the task was to avoid stepping on any object. In the experiments reported here, motion cues were eliminated by the use of low-frequency strobe lighting. In bright continuous light cats performed with great accuracy, and likewise at scotopic light levels. However, in strobe lighting their error rates increased more than threefold. This deterioration could not be attributed to lower acuity, since the cats' performance remained excellent when the light level was reduced well below that afforded by the strobe light. When very dim continuous light was combined with low-frequency strobe lighting, performance was substantially better than under strobe light alone. We conclude that motion-sensitive neurons make a major contribution to visual guidance of foot placement during locomotion. When strobe lighting is combined with very dim continuous light, even the minimal motion information available in the intervals between bright strobe flashes improves performance significantly. Cats were also trained to discriminate between complex patterns, and this discrimination was not affected by strobe lighting, suggesting that motion-sensitive neurons are not critical for this analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0953-816x.2001.01493.x
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of magnification functions in area 19 and the lateral suprasylvian visual area in the cat (1993)
    Springer
    Experimental brain research 97 (1993), S. 195-208 
    Details
    ISSN: 1432-1106
    Keywords: Extrastriate cortex ; Visual cortex ; Lateral suprasylvian area ; Receptive field size ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A retinotopic map can be described by a magnification function that relates magnification factor to visual field eccentricity. Magnification factor for primary visual cortex (VI) in both the cat and the macaque monkey is directly proportional to retinal ganglion cell density. However, among those extrastriate areas for which a magnification function has been described, this is often not the case. Deviations from the pattern established in V1 are of considerable interest because they may provide insight into an extrastriate area's role in visual processing. The present study explored the magnification function for the lateral suprasylvian area (LS) in the cat. Because of its complex retinotopic organization, magnification was calculated indirectly using the known magnification function for area 19. Small tracer injections were made in area 17, and the extent of anterograde label in LS and in area 19 was measured. Using the ratio of cortical area labeled in LS to that in area 19, and the known magnification factor for area 19 at the corresponding retinotopic location, we were able to calculate magnification factor for LS. We found that the magnification function for LS differed substantially from that for area 19: central visual field was expanded, and peripheral field compressed in LS compared with area 19. Additionally, we found that the lower vertical meridian's representation was compressed relative to that of the horizontal meridian. We also examined receptive field size in areas 17, 19, and LS and found that, for all three areas, receptive field size was inversely proportional to magnification factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228689
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  • 3
    Electronic Resource
    Electronic Resource
    Retinotopic order is surprisingly good within cell columns in the cat's lateral suprasylvian cortex (1992)
    Springer
    Experimental brain research 91 (1992), S. 46-60 
    Details
    ISSN: 1432-1106
    Keywords: Receptive field scatter ; Retinotopic scatter ; Visual cortex ; Extrastriate cortex ; Lateral suprasylvian cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The retinotopic map in the striate-recipient region of the cat's lateral suprasylvian cortex (referred to here as the lateral suprasylvian area (LS)) has generally been described as quite disorderly. The disorder is commonly attributed to receptive field scatter within cell columns, reflecting the very large size of receptive fields. However, scatter within columns has never been investigated. In the experiments reported here, we examined the receptive field scatter of cells in columns, and also the scatter of a limited sample of their afferents arising from areas 17 and 18. To measure post-synaptic receptive field scatter, electrode penetrations were made parallel to columns in LS, with the electrode approaching from the medial side, traversing the suprasylvian gyrus and emerging into the suprasylvian sulcus. In all 13 such penetrations, receptive fields were clustered together despite their large size. Their centers were scattered over a region that occupied on average less than 20% of the largest field in the column. In contrast, in columns in areas 17 and 18 receptive field centers reportedly are dispersed over regions about equal to the largest of the fields (Hubel and Wiesel 1962, 1965, 1974). The scatter of afferents' receptive fields was assessed anatomically by measuring the overlap between patches of different anterograde tracers in LS. These patches represented terminal labeling from two adjacent or overlapping tracer injections in area 17. While a large degree of overlap would be predicted if afferents have substantial scatter, we found the overlap to be small unless the two injection sites themselves were highly overlapping. Scatter in afferents' receptive fields was measured more directly by physiological recording. In previous experiments, cells in LS were silenced by the local injection of kainic acid, and responses were recorded from axon terminals arising from areas 17 and 18 (Sherk 1989). We examined the receptive field scatter in three penetrations made approximately normal to the cortical surface. Scatter was modest, much less than predicted by the size of post-synaptic receptive fields. Because the degree of receptive field scatter for postsynaptic cells in LS was similar to that of inputs from areas 17 and 18, the scatter of these inputs might be entirely responsible for that seen postsynaptically. Postsynaptic receptive field scatter, on the other hand, was too small to explain the reported disorder in the map in LS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230012
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  • 4
    Electronic Resource
    Electronic Resource
    Sources of subcortical afferents to the macaque's dorsal lateral geniculate nucleus (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 242 (1995), S. 566-574 
    Details
    ISSN: 0003-276X
    Keywords: Primate ; Thalamus ; Mesencephalon ; Visual pathways ; Horseradish peroxidase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: The dorsal lateral geniculate nucleus (dLGN) is the thalamic region responsible for transmitting retina signals to cortex. Brainstem pathways to this nucleus have been described in several species and are believed to control the retinocortical pathway depending on the state of the animal (awake, asleep, drowsy, etc.). The purpose of this study was to determine all of the subcortical sources of afferents to the dLGN in a higher primate, the macaque monkey, whose visual system is similar to that of humans.Methods: Injections of horseradish peroxidase (HRP), with or without conjugation to wheat germ agglutinin, were made into the dLGNs of seven macaque monkeys, followed by perfusion, brain sectioning, and analyses of neurons in the brainstem, thalamus, and hypothalamus that contained the retrogradely transported marker.Results: The reticular nucleus of the thalamus, pedunculopontine nucleus, parabigeminal nucleus, pretectal nucleus of the optic tract, superior colliculus, dorsal raphe nucleus, and tuberomammillary region of the hypothalamus contained many retrogradely labeled neurons ipsilateral to the injections. In the contralateral brainstem, HRP-labeled cells were found only in the pedunculopontine nucleus, nucleus of the optic tract, and dorsal raphe nucleus. The number of labeled neurons on the contralateral side was about one-half of that in corresponding ipsilateral nuclei. The locus coeruleus contained no labeled neurons in four of the macaques that had injections limited to the dLGN.Conclusion: There are seven subcortical regions that send afferents to the dLGNs of macaque monkeys. Except for the locus coeruleus, these are the same as observed for other species, such as the cat and rat, and indicate the possible sources of subcortical control over the dLGNs of humans. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092420413
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