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  • 1
    Electronic Resource
    Electronic Resource
    Central core control of developmental plasticity in the kitten visual cortex: II. Electrical activation of mesencephalic and diencephalic projections (1982)
    Springer
    Experimental brain research 47 (1982), S. 223-233 
    Details
    ISSN: 1432-1106
    Keywords: Visual cortex ; Development ; Plasticity ; Central core ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fifteen dark-reared, 4- to 5-week-old kittens were stimulated monocularly with patterned light while they were anesthetized and paralyzed. Six of these kittens were exposed to the light stimuli only, in four kittens the light stimuli were paired with electric stimulation of the mesencephalic reticular formation and in five kittens with electric activation of the medial thalamic nuclei. Throughout the conditioning period, the ocular dominance of neurons in the visual cortex was determined from evoked potentials that were elicited either with electric stimulation of the optic nerves or with phase reversing gratings of variable spatial frequencies. In two kittens, ocular dominance changes were assessed after the end of the conditioning period by analyzing single unit receptive fields. Monocular stimulation with patterned light induced a marked shift of ocular dominance toward the stimulated eye, when the light stimulus was paired with electric activation of either the mesencephalic reticular formation or of the medial thalamus. Moreover, a substantial fraction of cells acquired mature receptive fields. No such changes occurred with light or electric stimulation alone. It is concluded that central core projections which modulate cortical excitability gate experience-dependent modifications of connections in the kitten visual cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239381
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  • 2
    Electronic Resource
    Electronic Resource
    Auditory compensation of the effects of visual deprivation in the cat's superior colliculus (1983)
    Springer
    Experimental brain research 50 (1983), S. 69-83 
    Details
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Visual deprivation ; Auditory responses ; Multisensory convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurones in the superior colliculus of normal and visually deprived cats were analyzed for their responses to visual, auditory and somatosensory stimuli. The percentage of auditory-responsive cells throughout all layers had increased from 11% to 42% after binocular deprivation. Some auditory responses were found even in superficial layers. The number of somatosensory responses, though not systematically tested, was also higher in the visually deprived animals. Visually responsive units did not significantly decrease in number, thus resulting in an increased proportion of multisensory neurones. The vigour of auditory responses had increased after visual deprivation, while the vigour of visual responses had decreased significantly. In addition to the auditory effects of visual deprivation found, our study confirms previous findings on the visual effects of visual deprivation in the superior colliculus. Since only qualitative changes of visual responses, but no suppression of visual by non-visual activity was found, the neuronal mechanisms responsible for these changes may be different from competition as present in the visual cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238233
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Natural strabismus in non-siamese cats: Lack of binocularity in the striate cortex (1983)
    Springer
    Experimental brain research 52 (1983), S. 307-310 
    Details
    ISSN: 1432-1106
    Keywords: Strabismus ; Ocular dominance ; Visual cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cats with a natural convergent squint were discovered within a colony of normal Mill Hill cats. In two of them single unit recording was undertaken in area 17. The ocular dominance distribution showed a clear disruption of binocularity in both hemispheres. This lack of binocular units was comparable to cats with artificial, surgically-induced strabismus and differed significantly from the ocular dominance distribution of a normal control group. The existence of these natural, non-albino squinters strengthens the use of cats as an animal model for strabismic amblyopia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236640
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  • 4
    Electronic Resource
    Electronic Resource
    Instructive changes in the kitten's visual cortex and their limitation (1982)
    Springer
    Experimental brain research 48 (1982), S. 301-305 
    Details
    ISSN: 1432-1106
    Keywords: Visual deprivation ; Synaptic plasticity ; Orientation selectivity ; Visual cortex ; Kitten
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Kittens were reared wearing masks that contained strong cylindrical lenses, which allowed them to see only contours of one orientation. Selective exposure was alternated between the two eyes on successive days, while each time the other eye was covered by the mask. The total duration of exposure was different in the two eyes, amounting to 50 h for one eye and at least 100 h for the other. This resulted in asymmetric distributions of ocular dominance: neurones preferring precisely the experienced orientation favoured the eye with longer exposure, whereas neurones preferring oblique orientations adjacent to the experienced one surprisingly were dominated by the eye with shorter exposure. Thus neurones originally belonging to this group and dominated by the longer exposed eye must have tuned their orientation preference to the experienced orientation as a result of the longer exposure. Such instructive changes seem to be limited by the original response borders of the cortical neurones, as predicted by Hebb's rules for synaptic plasticity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237227
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of monocular strobe rearing on kitten striate cortex (1987)
    Springer
    Experimental brain research 68 (1987), S. 525-532 
    Details
    ISSN: 1432-1106
    Keywords: Cat ; Visual cortex ; Stroboscopic exposure ; Monocular experience ; Motion deprivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Monocular deprivation in kittens does not lead to an ocular dominance shift in striate cortex if the visual stimuli do not contain contours. In the present study we sought to find out whether an ocular dominance shift is produced if the visual environment does contain contours but is devoid of motion. Six kittens were reared with one eye occluded in a visual environment that was lit only by the light of a stroboscope (2 flashes per sec). Exposure was started at 5–6 weeks of age after dark-rearing from birth and extended until 8–12 weeks of age for 8 h per day. The rest of the time was spent in total darkness. Thus, the animals were completely deprived of vision in one eye, while the other eye experienced only stationary flashing contours. Single units in area 17 of these animals were studied and compared to normally reared cats. In all six animals ocular dominance was clearly shifted towards the eye with strobe experience. The ocular dominance shift showed, however, the following interdependencies with other parameters: neurones that responded to stationary flashing test stimuli were nearly always dominated by the strobe eye; neurones that responded only to moving bars or edges remained binocular. In the normal control animals the ocular dominance distribution was similar for both groups of cells. Track analysis according to cortical lamination revealed that neurones in infragranular layers consistently showed a weaker OD shift towards the strobe eye than neurones in supragranular layers (including layer 4). Response latencies to stationary flashing stimuli were significantly shorter in the strobe-reared animals than in the normal controls. Orientation tuning was normal in all animals. Directional tuning was reduced after monocular strobe experience, but not by the same amount as described after binocular strobe rearing. The present results demonstrate that monocular visual experience reduced to stationary flashing contours is sufficient to produce on ocular dominance shift in striate cortex. This adds further support to existing notions about the role of nervous activity for changes in cortical connections. Cortical responses to afferent stimulation and the resulting correlated activation of pre- and postsynaptic neurones seem to be a prerequisite for a stabilization of synaptic connections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249796
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Temporal Integration in Visual Cortex of Cats with Surgically Induced Strabismus (1993)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 5 (1993), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Single unit response latencies in striate cortex after visual stimulation with stationary flashed bars were measured and interocularly compared in anaesthetized cats with surgically induced strabismus, in order to elucidate the neural basis of strabismic amblyopia. Four unilateral esotropic and two exotropic cats were studied. The visual onset latencies of cortical neurons ranged from 30 to 170 ms after stimulation of the non-deviating eye at a contrast of 82%. Responses after visual stimulation of the deviating eye were consistently delayed by ∼10 ms. The latency increase was independent of the direction and absolute angle of squint in the different animals. Peak latencies of cortical neurons ranged from 43 to 245 ms. Median peak latency was 85 ms for the non-deviating and 95 ms for the deviating eye. The rise time of cortical flash responses, as determined from onset - peak differences, ranged between 2 and 170 ms. Direct interocular comparison of response latencies in the remaining binocular neurons revealed an invariable advantage for the non-deviating eye. Supragranular neurons showed a greater interocular latency difference than neurons in layer IV. Visual latencies were contrast-dependent. However, the latency reduction with increasing contrast was less pronounced for the deviating eye. We discuss the possibility that central integration times, especially within cortex, are prolonged in strabismic cats, affecting temporal coincidence of signal processing in the visual cortex. The resulting disturbance of spatio-temporal integration, as caused by a scrambling of geniculo-striate and intracortical connections, may be the substrate of binocular suppression and strabismic amblyopia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1993.tb00218.x
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  • 7
    Electronic Resource
    Electronic Resource
    Changes in the circuitry of the kitten visual cortex are gated by postsynaptic activity (1979)
    [s.l.] : Nature Publishing Group
    Nature 280 (1979), S. 58-60 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Three kittens were dark reared until the age of 5 weeks and then, with one eye closed, exposed to a normal environment for 9 consecutive days. Control experiments and a number of previous studies have shown that by this time most cortical cells have become dominated by the open eye and display ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/280058a0
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Thalamo-cortical connections and their correlation with receptive field properties in the cat's lateral suprasylvian visual cortex (1987)
    Springer
    Experimental brain research 67 (1987), S. 100-112 
    Details
    ISSN: 1432-1106
    Keywords: Visual system ; Lateral suprasylvian cortex ; Electrical stimulation ; Thalamo-cortical connections ; Direction selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Areas PMLS and PLLS of the cat's lateral suprasylvian visual cortex display an interesting global organization of local features in their single unit response properties: direction preference is centrifugally organized and velocity preference increases with eccentricity. In addition it has previously been shown that binocular interactions are strongest around the visual field center. This characterizes the LS areas as apt for the analysis of optic flow fields and for visual processing in various kinds of visuomotor tasks (Rauschecker et al. 1987). In the present study we analysed the types of input to LS from the optic chiasm, the corpus callosum and from two thalamic relay nuclei (lateral posterior and lateral geniculate) that constitute important sources of afferent information to the LS areas. We were interested in learning how the afferent (and efferent) connections between LS and these structures relate to the response properties of LS neurons. Overlap of an RF into the ipsilateral hemifield was virtually always associated with callosal input. Latency differences between responses to electrical stimulation of the optic chiasm and the thalamic sites indicated almost exclusively fast-conducting Y-input to LS. Correlation of response latencies with receptive field properties revealed the following correspondences: A positive correlation was found between LP-latency and RF-size matching the dependence of RF size on laminar origin. The type of correlation found between LP-latency and directional tuning of LS cells suggests that an interaction between thalamic and other inputs may be responsible for direction selectivity in LS. Finally, correlation of LP-latencies with centrifugal direction preference suggests that this specific property is generated by intracortical wiring rather than by thalamic input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00269458
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