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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 35 (1979), S. 559-582 
    ISSN: 1432-1106
    Keywords: Strabismus ; Amblyopia ; Retinal ganglion cells ; Visual acuity ; Contrast sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The spatial resolving power, contrast sensitivity, and receptive field properties of retinal ganglion cells were studied in cats reared with either convergent or divergent squint in one eye. Sustained-X cells in the area centralis of the squinting eye of the cats with esotropia without alternating fixation showed significantly poorer spatial resolution, and reduced contrast sensitivity compared with cells in the area centralis of the normal eye. These amblyopic sustained-X cells in the area centralis of the squinting eye had receptive field characteristics similar to those found in immature cells of young kittens. They had a shallow sensitivity gradient within a relatively widespread centre zone and a weak and widespread inhibitory surround. In contrast, the sustained cells in the area centralis of the normal eye revealed a typical, well defined, small centre zone with its sensitivity gradient extremely steep and its inhibitory surround strong and confined. A minor degree of amblyopia was also found in transient Y-cells in the area centralis of the squinting eye of these cats. However, no loss of resolving power was found in the cells in the area centralis of the squinting eye of the cats with esotropia or exotropia which showed alternating fixation. Thus, amblyopia occurs in those eyes which have lost the use of the area centralis as the normal visual axis during early postnatal development, and its organic lesion is already apparent in the retinal ganglion cells — the third order neurone in the afferent visual system. It is suggested that the loss of the ability to fixate results in inadequate stimulation of the central retinal ganglion cells due to the habitual presence of blurred images at the area centralis which prevents their full development during the critical period.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 25 (1976), S. 63-77 
    ISSN: 1432-1106
    Keywords: Kitten LGN ; Single cell ; Convergent squint ; Visual acuity ; Amblyopia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The spatial resolution of LGN cells has been studied in 4–5 month old kittens raised with convergent squint surgically produced in one eye at the age of 3–4 weeks. The ‘sustained’ cells which received inputs from the central retina of the squint eye showed significantly poorer spatial resolution (determined by the highest spatial frequency of a sinusoidal grating to which a cell responded with modulated firing) than those which received inputs from the central retina of the normal eye. The spatial resolution of cells which received inputs from the peripheral retina of the squint eye was not different from that of cells receiving inputs from the peripheral retina of the normal eye. The visual latency of ‘sustained’ cells which received an input from the area centralis of the squint eye was considerably lengthened and the response showed a sluggish onset. Thus the most important clinical symptom of amblyopia, namely the reduction of foveal visual acuity, has been demonstrated in kittens raised with unilateral vonvergent squint. The results suggest that the lesion responsible for amblyopia due to squint might be a functional degeneration of the high spatial frequency tuning cells in the pathway prior to the visual cortex, i.e. in the retina or LGN.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 34 (1979), S. 11-26 
    ISSN: 1432-1106
    Keywords: Convergent squint ; Amblyopia ; Spatial vision in cat ; Contrast sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Visual acuity and contrast sensitivity were measured behaviourally in normal adult cats and cats reared with monocular convergent squint from 3, 6, 8, 12, and 24 weeks of age. The visual acuity of the squinting eye was significantly lower than that of the non-squinting eye in cats with squint from 3, 6, and 8 weeks of age. No significant difference in acuity between eyes was found in the 12- and 24-week squinting cats and in the controls. Contrast thresholds at all spatial frequencies tested (range 0.13–2.0 c/ °) were higher in the squinting eye than in the non-squinting eye of cats with squint from 3 and 6 weeks of age, but differences were greater at the higher spatial frequencies. In the 8-week squinting cat, contrast thresholds were increased only at higher spatial frequencies. No significant differences in contrast sensitivity were found in the cat with squint from 24 weeks of age and in the controls. The degree of disturbance of spatial vision in squinting cats was most related to the age at onset of the squint, i.e., the earlier the onset, the more profound the amblyopia. The period of susceptibility extended from about 3 to 12 weeks of age. When compared with data on the development of visual acuity in kittens, the pattern of results from the present study suggests that convergent squint can arrest the development of spatial vision.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 31 (1978), S. 193-206 
    ISSN: 1432-1106
    Keywords: Kitten LGN ; Development ; Visual acuity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The spatial resolving power and receptive field properties of ‘sustained’ cells in layers A and A1 of the lateral geniculate nucleus (LGN), which received inputs from the area centralis of the retina in kittens of 3–16 weeks of age had been studied. The basic concentric organisation of receptive fields of ‘sustained’ LGN cells receiving inputs from the area centralis appeared to be already laid out at 3 weeks in kittens. Spatial resolving power of the cells determined using the highest spatial frequency of a sinusoidal grating resolved by cells as a measure of cellular visual acuity, however, developed gradually to the level of adult LGN cells during the sensitive period (3–12 weeks). Although this development occurred alongside the process of maturation of ocular alignment and the refractive state of the eyes, following the clearing of the embryonic vasculature of the ocular media from the 4th week onward, it depended on the enhancement of distinct inhibitory surround mechanisms taking place during the 6th–11th week. The course of development of spatial resolution of ‘sustained’ LGN cells receiving inputs from the area centralis of the retina runs parallel with the developmental curve of visual acuity in kittens obtained by visually evoked responses or by behavioural techniques by previous workers. The neural mechanisms which subserve high visual acuity are therefore already determined at the LGN before the inputs of the two eyes are mixed at the visual cortex.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Kitten LGN ; Convergent squint ; Visual development ; Amblyopia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In twelve kittens, convergent squint was surgically produced at either 3, 6, 8, 10, 13, or 16 weeks. When these kittens reached the age of 4–8 months, the spatial resolution of ‘sustained’ cells which received inputs from the area centralis in layers A and A1 of both the left and right lateral geniculate nucleus (LGN) was measured under nitrous oxide/halothane anaesthesia, using the highest spatial frequency of a sinusoidal grating resolved by cells as a measure of cellular visual acuity. Spatial resolution of cells fed by the squinting eye's area centralis was poorest in the kittens in which the squint was produced at 3 weeks. The resolution of the cells driven by the area centralis of the squinting eye gradually improved for the kittens in which the squint was produced at progressively later stages. There was no effect of convergent squint on the resolving power of cells in the kittens in which squint was produced at 13 weeks and 16 weeks. The developmental curve of spatial resolution of LGN cells obtained from normal kittens of different ages was found to fit very closely with a plot of the spatial resolution of cells driven by the squinting eye against age at squint production. These results suggest that the loss of spatial resolution (amblyopia) in the eye with convergent squint is due to the arrest of development of spatial resolution during the sensitive period in early postnatal life. Clinical implications are discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 142 (2000), S. 1317-1318 
    ISSN: 0942-0940
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0942-0940
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 6 (1979), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Ten inbred strains of mice were administrated with dinitrophenyl-bovine serum albumin (DNP-BSA) at a dose of 30 or 300 μg/day by continuous infusion technique. Anti-DNP plaque-forming cells (PFC) in their spleens were assayed 10 to 12 days after the beginning of the infusion. NZB, BALB/c, C3H/He and NC strains were high responders to both doses of DNP-BSA. KK, SII and TES strains were low responders: the antibody response was low to the dose of 30 μg/day, and high to the dose of 300 μg/day. Breeding tests between high responder BALB/c and intermediate responder DDD mice indicated that the immune response was largely controlled by a gene linked to the H-2 complex. Similar studies with high responder NZB and low responder TES mice suggested an involvement of a few genes: at least one of the controlling genes may be linked to the H-2 complex.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4637-4645 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method for evaluating localized grain boundary (GB) trap states in polycrystalline–silicon thin-film transistors (poly-Si TFTs) is proposed. Field effects in poly-Si TFTs are analyzed by decomposition of the two-dimensional Poisson's equation. This analysis gives the theoretical basis for evaluating the localized GB trap state density. The trap states are evaluated with the GB barrier potential given by the activation energy of the effective mobility and with the surface potential calculated from the capacitance–voltage characteristics in poly-Si TFTs. This evaluating method was applied to several different types of poly-Si TFTs fabricated with excimer laser annealing crystallization processes. This method has succeeded experimentally in eliminating the error effects related to oxide–semiconductor interface trap states and in clarifying that the GB barrier potential has a peak in its gate bias dependence. This method has also elucidated that the GB trap state density has almost the same value independent of the grain size when the hydrogenation efficiency in poly-Si is in the same level between TFTs. The good agreement of the simulated and the measured drain currents confirm the validity of this method. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3259-3261 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photon-induced current (Iph) in polycrystalline-silicon thin-film transistors (poly-Si TFTs) has been investigated using a line-shaped light beam scanning method. In the off-state region, photon-excited carriers in the channel region diffuse to the drain with the diffusion length independent of the poly-Si grain size. The diffusion length is also independent whether poly-Si is hydrogenated or not. This phenomenon is observed in both n-channel and p-channel TFTs. In the subthreshold region, Iph follows the general transport equation in poly-Si. In the inversion region, Iph is proportional only to the total amount of excited carriers in the channel. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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