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  • 1
    Electronic Resource
    Electronic Resource
    Corticofugal influence on evoked activity of lateral geniculate neurons in the rabbit (1977)
    Springer
    Experimental brain research 29 (1977), S. 527-530 
    Details
    ISSN: 1432-1106
    Keywords: Lateral geniculate nucleus ; Cortical depression ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Corticofugal influence upon lateral geniculate units was eveluated by inactivating the visual cortex with a topical application of 3 M KCL in rabbits. The results revealed a decrease of spontaneous firing in slow P cells following cortical depression suggesting a tonic corticofugal influence. The most consistently observed alteration was an enhancement of the ON response with a decrease of the response to the opposite stimulus (OFF); and vice versa: the short latency excitation being augmented. It is suggested that the visual cortex exerts a powerful influence on intra-geniculate inhibitory processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236189
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects on binocular activation of cells in visual cortex of the cat following the transection of the optic tract (1983)
    Springer
    Experimental brain research 50 (1983), S. 392-396 
    Details
    ISSN: 1432-1106
    Keywords: Corpus callosum ; Visual cortex ; Optic tract section ; Binocular cells ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cells in area 17 of the cortex are generally activated either directly through a retino-thalamic pathway or indirectly via a contralateral hemispherecallosal pathway. The aim of the present experiment was to evaluate the effects of eliminating this second pathway on the binocular activation of cells in the primary visual cortex. The optic tract was sectioned on one side in 18 cats and unit activity was recorded in the contralateral hemisphere. This hemisphere should receive normal thalamo-cortical inputs but no visual callosal input. These animals were compared to 21 normal cats. Extracellular electrophysiological recordings were carried out in the conventional way using tungsten microelectrodes and N2O anaesthesia. Results indicated that the proportion of binocular cells found in the cortex of tract sectioned animals was lower than that found in normal animals. However, this decrease in binocularity could be essentially attributed to cells having receptive fields situated to within 4 ° of the vertical meridian of the visual field. These results are interpreted as being congruent with the demonstrated anatomo-physiological projections of the callosal system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239205
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The role of the visual cortex in response properties of lateral geniculate cells in rats (1984)
    Springer
    Experimental brain research 53 (1984), S. 223-232 
    Details
    ISSN: 1432-1106
    Keywords: Cortico-geniculate influence ; Lateral geniculate nucleus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unitary discharges of the lateral geniculate nucleus (LGN) were analyzed in anesthetized and paralyzed rats after inactivation of visual cortical areas (VC) by cryoblockade or by depositing a cotton wick soaked in KCl (3 M). The receptive fields were mapped prior to and following the interruption of the cortico-geniculate feedback. The responsiveness of the VC was controlled by monitoring evoked potentials and the EEG. In most off-center and about half on-center cells the surround excitatory responses were markedly reduced and even totally abolished. In contrast, the center excitation remained unchanged or increased suggesting a parallel decline of the inhibitory surround. This differential influence of cortical blockade on on- or off-responses failed to appear in on-off cells whose receptive field was nonconcentrically organized. It is proposed that the VC exerts a complex influence upon geniculate physiology while the spatial center-surround relationships are under the control of the VC. The results of this investigation are comparable to those obtained in rabbits and cats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238152
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of the superior colliculus on visual responses of cells in the rabbit's lateral posterior nucleus (1990)
    Springer
    Experimental brain research 80 (1990), S. 387-396 
    Details
    ISSN: 1432-1106
    Keywords: Lateral posterior nucleus ; Pulvinar ; Superior colliculus ; Tecto-LP pathway ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The lateral posterior-pulvinar (LP-P) complex of mammals receives a major input from the superior colliculus (SC). We have studied the response properties of LP cells and investigated the effects of reversible inactivation of the colliculus on the visual responses of LP units in anesthetized and paralyzed rabbits. Cells in LP had large receptive fields responsive to either stationary or moving stimuli. One third of the motion-sensitive cells were direction selective. The size of the receptive fields increased with eccentricity and there was a retinotopic organization along the dorso-ventral axis. Comparison of the LP and superior colliculus properties revealed substantial differences in visual response characteristics of these two structures such as the size of the receptive fields and the number of direction-selective cells. Electrical stimulation of the LP evoked antidromic action potentials in tectal cells that were motion sensitive. We found a dorsoventral gradient in the projections of collicular cells. Units located more dorsally in the colliculus sent their axons to LP while cells lying more ventrally sent axons toward the region lying posterior to LP. A micropipette filled with lidocaine hydrochloride was lowered into the superficial layers of the superior colliculus in order to reversibly inactivate a small population of collicular cells. Rendering the superior colliculus inactive produced a sharp attenuation of visual responses in the majority of LP cells. Some neurons ceased all stimulus-driven activity after collicular blockade while a few cells exhibited increased excitability following collicular inactivation. These experiments also indicate that the tecto-LP path is topographically organized. An injection in the colliculus failed to influence the thalamic response when it was not in retinotopic register with the LP cells being recorded. Our results demonstrate that the superior colliculus input to LP is mainly excitatory in nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228166
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    Paper (German National Licenses)
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