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  • 1
    ISSN: 1432-1106
    Keywords: Cat LGN ; Monocular Deprivation ; Visual Acuity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The visual acuity (spatial resolving power) and the relative incidence of X- and Y-cells in laminae A and A1 of the dorsal lateral geniculate nucleus (LGN) with receptive fields within 10 ° visual angle to the area centralis have been determined in normal and monocularly deprived cats, using a square-wave grating with logarithmically varying spatial frequencies (0.05–8 c/deg). In the normal cat's LGN the incidence of Y-cells is 1.6 times higher in A1 (48% of the relay-cells) than in A (29%). The mean spatial resolution of all cells is 1.3 times higher in A (2.5 ± 1.2 c/deg) than in A1 (1.8 ± 1.0 c/deg). Mean acuity of Y-cells is equal in both laminae (1.1 ± 0.5 c/deg), but for X-cells it is higher in lamina A (2.9 ± 1.0 c/deg in A, vs. 2.5 ± 0.7 c/deg in A1). After early monocular deprivation, visual acuity is reduced in the deprived lamina A1 (X-cells: 1.7 ± 0.9 c/deg in A1 vs. 2.6 ± 0.7 c/deg in A; Y-cells: 0.9 ± 0.4 c/deg in A1 vs. 1.3 ± 0.4 c/deg in A). This confirms the results of Maffei and Fiorentini (1976). However, visual acuity of X-cells is still higher in the deprived lamina A (3.1 ± 1.0 c/deg) than in the non-deprived lamina A1 (2.7 ± 0.7 c/deg). For Y-cells, visual acuity is equal in both laminae (1.3 ± 0.5 c/deg). Thus the loss of visual acuity is only significant in lamina A1. This loss was equally strong in the area centralis and up to 10 ° eccentricity. Ipsilateral to the early deprived eye only 37% of all recorded Y-cells were located in the deprived lamina A1 (this is 1.7 times less than in the normal A1). Contralateral to the deprived eye 29% of the Y-cells were recorded in the deprived lamina A (1.3 times less than in the normal A). In conclusion, both the impairment of mean visual acuity and the reduction in the recording probability of Y-cells were more pronounced in lamina A1 (receiving uncrossed inputs from the deprived eye) than in lamina A (crossed inputs).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 59 (1985), S. 395-403 
    ISSN: 1432-1106
    Keywords: Nucleus of the optic tract ; Direction-selective retinal ganglion cells ; Optokinetic reflex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the physiological properties of ganglion cells in the retina of the cat. The experiments were designed to identify those ganglion cells which project to direction-selective cells in the nucleus of the optic tract (NOT), by demonstrating their antidromic activation at low threshold from an electrode in the NOT. These ganglion cells presumably provide the retinal drive to the optokinetic reflex. Altogether, 11 such ganglion cells were identified in a population of 578 cells studied. All 11 were W-cells, with slow-conducting axons. Five of the 11 had on-centre direction-selective receptive fields; the other 6 had a variety of receptive field patterns. Thus, on centre-selective cells form a much higher proportion of the retinal input to direction-selective cells in the NOT than of the overall ganglion cell population. However, their receptive field properties were too varied fully to account for the selectivity of NOT cells for horizontal stimulus movement. In summary the retinal input to the NOT appears to be formed principally or entirely by W-class ganglion cells, including many which are direction selective. It still seems necessary, however, to postulate, some non-retinal mechanism to account for all the receptive field properties of direction-selective NOT cells.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 66 (1987), S. 440-444 
    ISSN: 1432-1106
    Keywords: Optokinetic reflex ; Light rearing ; Dark rearing ; Israelian gerbil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Israelian gerbils (Meriones tristrami) reared in the dark from birth to 7–13 weeks of age show a clear optokinetic reflex in both horizontal directions under monocular viewing conditions. This is very different from gerbils reared in the light, which like many other mammals with lateral eyes show a clear monocular optokinetic reflex only in response to stimuli moving from temporal to nasal in the visual field. It is concluded that exposure to day light during the first postnatal weeks prevents the development of the naso-temporal component of the optokinetic reflex in the Israelian gerbil.
    Type of Medium: Electronic Resource
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