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  • Contrast sensitivity  (3)
  • Striate cortex  (2)
  • Triticum aestivum  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Meridional amblyopia in monkeys (1980)
    Springer
    Experimental brain research 39 (1980), S. 351-356 
    Details
    ISSN: 1432-1106
    Keywords: Oblique effect ; Meridional amblyopia ; Contrast sensitivity ; Animal psychophysics ; Reaction time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Contrast sensitivity as a function of the orientation of a grating stimulus was determined by behavioral methods for four rhesus monkeys. Two of the monkeys had been reared with normal binocular experience, had spherical refractive errors, and showed a normal oblique effect. The other two monkeys which had been reared with one eyelid sutured (which was still sutured during these experiments), showed astigmatic refractive errors in the non-deprived eye and grating contrast sensitivity as a function of orientation that was correlated with the principal meridians of their astigmatism. Control experiments showed that the meridional amblyopia was not due to an uncorrected refractive error. Reaction time measures of contrast sensitivity for suprathreshold grating patterns showed that meridional amblyopia was not present for high contrast gratings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237124
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of reverse monocular deprivation in monkeys I. Psychophysical experiments (1989)
    Springer
    Experimental brain research 74 (1989), S. 327-337 
    Details
    ISSN: 1432-1106
    Keywords: Amblyopia ; Stimulus deprivation ; Reverse deprivation ; Psychophysics ; Contrast sensitivity ; Spectral sensitivity ; Oblique effects ; Rhesus monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Monkeys had one eye closed at about 30 days of age for 14, 30, 60, or 90 days, then opened, and the fellow eye closed for another 120 days. The animals then had at least 10 months of binocular visual experience before behavioral training and testing were begun. All subjects were used in a series of psychophysical investigations during the next two years. The results of the behavioral studies indicated that the initially deprived eyes (IDE) of the two monkeys that were subjected to initial deprivation periods of 14 or 30 days recovered normal or nearnormal spatial contrast sensitivity. In contrast, the two animals which underwent longer periods of initial deprivation showed incomplete recovery, especially for high spatial frequency stimuli. All of the monkeys exhibited a reduction in spatial contrast sensitivity for their reverse deprived eyes (RDE); the earlier the onset of the reverse-deprivation procedures (i.e., the, shorter the initial period of deprivation), the greater the deficit in the RDE's spatial contrast sensitivity. Measurements of temporal contrast sensitivity showed that all of the subjects' IDEs had normal or near-normal sensitivity levels. However, the reverse-deprivation procedures initiated at 90 days of age or earlier produced a frequency dependent reduction in the RDE's temporal modulation sensitivity. The measures of increment-threshold spectral sensitivity revealed that only the RDE of the monkey that had the shortest initial deprivation period had an abnormal spectral sensitivity function. The results demonstrate that many of the severe behavioral deficits produced by early monocular form deprivation can be recovered via reverse deprivation procedures. However, depending upon the length of the initial deprivation period and the age at which the reversal procedure is initiated, the second deprivation period can also adversely affect the functional capacity of the RDE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248866
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  • 3
    Electronic Resource
    Electronic Resource
    The critical period for corpus callosum section to affect cortical binocularity (1985)
    Springer
    Experimental brain research 57 (1985), S. 213-223 
    Details
    ISSN: 1432-1106
    Keywords: Corpus callosum ; Binocularity ; Critical period ; Striate cortex ; Ocular dominance ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The period of time during which surgical section of the corpus callosum (CC) is effective in altering the physiological properties of cells in cat striate cortex was investigated. Cats which had the CC transected between 13 days and 24 weeks of age were studied using extracellular, single-unit recording procedures. Analysis of the results from 1,747 cortical units indicate that when the CC was sectioned prior to 19 days of age there was a reduction in the encounter rate of binocularly activated neurons and an increase in the proportion of neurons dominated by the contralateral eye. The decrease in cortical binocularity was observed in both simple and complex cell populations, and at all receptive field eccentricities studied (0–39°). However, when the CC was sectioned after 19 postnatal days, no physiological changes were detected. Thus, in contrast with previous studies (Payne et al. 1980a, b) no changes were found following CC section in adult cats. The results therefore define a critical period which ends before 3 weeks of age during which corpus callosum section reduces striate cortex binocularity. Although the corpus callosum critical period is much shorter than the critical period for experiential alterations in cortical binocularity, the physiologically determined limits of the callosal critical period agree with the behaviorally determined limits previously found for the callosal critical period (Elberger 1984).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236526
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of reverse monocular deprivation in monkeys II. Electrophysiological and anatomical studies (1989)
    Springer
    Experimental brain research 74 (1989), S. 338-347 
    Details
    ISSN: 1432-1106
    Keywords: Amblyopia ; Stimulus deprivation ; Reverse deprivation ; Lateral geniculate nucleus ; Striate cortex ; Cytochrome oxidase ; Rhesus monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Monkeys had one eye closed at about 30 days of age for 14, 30, 60, or 90 days, then opened, and the fellow eye closed for another 120 days. The animals then had at least 10 months of binocular visual experience before extensive behavioral training and testing were carried out. In terminal experiments concluded more than 18 months later, microelectrode investigations of the striate cortex demonstrated that there was almost a complete absence of binocular neurons in all animals. The initially deprived eyes (IDEs) dominated the majority of cortical neurons, even when soma size measurements of lateral geniculate neurons indicated that the LGN cells driven by the IDE had not regained their normal size. The monkeys which had significant interocular differences in spatial vision also exhibited abnormalities in the distribution of the metabolic enzyme, cytochrome oxidase (CO), within the striate cortex. These results demonstrate that many of the severe alterations in cortical physiology and eye dominance produced by early monocular form deprivation can be reversed, with recovery of normal cortical function, via the reverse-deprivation procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248867
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  • 5
    Electronic Resource
    Electronic Resource
    Binocular interactions in normal and anomalous binocular vision (1980)
    Springer
    Documenta ophthalmologica 49 (1980), S. 303-324 
    Details
    ISSN: 1573-2622
    Keywords: Binocular interactions ; Psychophysics ; Amblyopia and strabismus ; Dichoptic masking ; Binocular vision ; Contrast sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Binocular interactions for grating patterns were investigated in humans with normal binocular vision and in humans with abnormal binocular visual experience due to strabismus and/or amblyopia via 1) comparison of monocular and binocular contrast thresholds; 2) interocular transfer of the threshold elevation aftereffect; and 3) dichoptic masking. Whereas the normal observers showed improved binocular over monocular contrast sensitivity (i.e., binocular summation) and substantial interocular transfer of the threshold elevation aftereffect, the abnormal observers showed an absence of binocular summation and no significant interocular transfer. The dichoptic masking experiments showed that a suprathreshold masking grating presented to one eye elevated the contrast threshold for gratings presented to the fellow eye, within a narrow range of spatial frequencies (about 1 octave wide at half height) and orientations, centered about the spatial frequency and orientation of the mask. The magnitude and bandwidth of this masking effect was similar in subjects with normal and abnormal binocular vision, occurring even when the masking grating was presented to the amblyopic eye. These effects depend upon the contrast of the masking grating. In individuals with normal binocular vision, a grating with subthreshold contrast presented to one eye reduces the contrast threshold for detection of gratings of similar spatial frequency and orientation presented to the fellow eye. No such subthreshold summation is evident in the amblyopic observers. We conclude that while strabismus and/or amblyopia disrupted the normal excitatory interactions between the two eyes, cortical inhibitory binocular connections were not disrupted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01886623
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  • 6
    Electronic Resource
    Electronic Resource
    Inheritance of biotype E greenbug resistance in bread wheat CI 17882 and its relationship with wheat streak mosaic virus resistance (1986)
    Springer
    Euphytica 35 (1986), S. 615-620 
    Details
    ISSN: 1573-5060
    Keywords: Triticum speltoides ; Aegilops speltoides ; Triticum aestivum ; wheat ; Schizaphis graminum ; greenbug ; wheat streak mosaic virus ; insect biotypes ; host plant resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Genetic studies were conducted to determine the inheritance of biotype E greenbug resistance in CI 17882 (CI 15092/T. speltoides//Fletcher/3/4* Centurk), a wheat germplasm line previously released as resistant to wheat streak mosaic virus (WSMV). In addition, the association of greenbug and WSMV resistance in CI 17882 was examined. Results indicated that biotype E greenbug resistance in CI 17882 is conditioned by a single dominant gene that is not linked with the WSMV resistance gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021870
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  • 7
    Electronic Resource
    Electronic Resource
    Combining ability analysis for harvest index in winter wheat (1991)
    Springer
    Euphytica 55 (1991), S. 229-234 
    Details
    ISSN: 1573-5060
    Keywords: Triticum aestivum ; wheat ; harvest index ; diallel analysis ; genotypic and phenotypic correlations ; assimilate partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Cereal breeders have used harvest index (HI) as a selection criterion in segregating generations to identify physiologically superior lines with improved partitioning of total assimilate into grain. Information on combining ability for HI of the hard red winter wheat (Triticum aestivum L.) cultivars of the Southern Great Plains is not available. A study was undertaken to examine HI of seven genetically diverse winter wheat parents, evaluate their general combining ability (GCA) and specific combining ability (SCA) effects, and study correlations of HI with several agronomic traits. The seven parents were crossed in a half-diallel mating design to produce 21 crosses. The F1's, their F2 progenies, and the parents were evaluated in replicated field tests at Stillwater and at Lahoma, OK. The combining ability analysis was performed using Griffing's Method 4, Model 1. The results showed significant variation among parents for HI. The GCA and the SCA effects were mostly inconsistent between generations and between environments. However, parents with consistently high HI and positive GCA estimates were identified. The progeny with high HI mostly resulted from parents with high GCA estimates. The correlations between HI and agronomic traits indicated that improvement in HI should also result in high grain yield, early maturity, and short plant height.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021243
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