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Strasburger H.,Ludwig Maximilians University of Munich | Malania M.,Agricultural University of Georgia
Journal of Vision

The loss of positional information for whole letters is one of the most important factors contributing to impaired letter and word recognition. Here we study the quantitative characteristics of flanker confusions in a crowding paradigm and test whether transient spatial attention relieves the crowding effect by reducing flanker confusions. We examined the crowding effect at three eccentricities for a range of flanker distances and attentional cue sizes. The effects of flanker distance confirm earlier findings that errors of both content and position are highest with flankers close by. However, the cue has no effect on flanker confusions and affects content information only, by enhancing target contrast sensitivity independent of cue size.Confusions with the inward, but not the outward, flanker increase linearly with eccentricity.Inward-flanker confusions dominate unlike reported asymmetries for masking. Our results are a psychophysical counterpart to separate neural coding of what and where in pattern recognition.The dependencies of cue effect and confusions on flanker distance scale with eccentricity and can be described by a generalized Bouma critical-separation rule. That rule shows a formal analogy to M scaling, from which the critical crowding distances on a cortical map can be derive as a logarithmic function. The perceptual results are visualized in a "doughnut" model. © 2013 ARVO. Source

Ratajova A.,Agricultural University of Georgia
Environmental Science and Pollution Research

Urban sprawl and increasing economical pressure on agricultural production raises new unprecedented environmental questions. The presented study proved that higher level of fertilization of the urban vegetation significantly increases the concentration of male microgametophytes in the air during the flowering season. The levels of fertilization had no significant effect on the pollen grain size, nor on the profile and content of the phenolic compounds, however, the content of tryptophan (protein with a key role in allergies) was significantly influenced. The metabolism of tryptophan and its role in human imunilogy is not yet completely understood, however, it is recommended to avoid unnecessary fertilization in urbanized areas. © 2014 Springer-Verlag Berlin Heidelberg. Source

Kunchulia M.,Agricultural University of Georgia | Pilz K.S.,University of Aberdeen | Herzog M.H.,Ecole Polytechnique Federale de Lausanne
Scientific Reports

Nicotine is an important stimulant that is involved in modulating many neuronal processes, including those related to vision. Nicotine is also thought to play a key role in schizophrenia: A genetic variation of the cholinergic nicotine receptor gene, alpha-7 subunit (CHRNA7) has been shown to be associated with stronger backward masking deficits in schizophrenic patients. In this study, we tested visual backward masking in healthy smokers and non-smokers to further understand the effects of nicotine on spatiotemporal vision. In the first study, we tested 48 participants, a group of non-smokers (n = 12) and three groups of regular smokers that were either nicotine deprived (n = 12), non-deprived (n = 12) or deprived but were allowed to smoke a cigarette directly before the start of the experiment (n = 12). Performance was similar across groups, except for some small negative effects in nicotine-deprived participants. In the second study, we compared backward masking performance between regular smokers and non-smokers for older (n = 37, 13 smokers) and younger (n = 67, 21 smokers) adults. Older adults performed generally worse than younger adults but there were no significant differences in performance between smokers and non-smokers. Taken together, these findings indicate that nicotine has no long-term negative effects on visual spatiotemporal processing as determined by visual backward masking. Source

Parasitoids of coccoids were surveyed using malaise traps at the Golcuk Natural Park (Isparta Province), Turkey, in 2009 and 2010. More than 40 species of parasitoids were collected, with twelve being new records for Turkey, of which five, Anagyrus descriptus sp. n., A. alienus sp. n., Aschitus golcukus sp. n., Charitopus bulentyasari sp. n., and Ch. ismailkaracai sp. n. (Hymenoptera: Encyrtidae), are described as new species. © Entomológica Fennica. Source

Betsiashvili M.,Boyce Thompson Institute for Plant Research | Betsiashvili M.,Agricultural University of Georgia | Ahern K.R.,Boyce Thompson Institute for Plant Research | Jander G.,Boyce Thompson Institute for Plant Research
Journal of Experimental Botany

Plants show considerable within-species variation in their resistance to insect herbivores. In the case of Zea mays (cultivated maize), Rhopalosiphum maidis (corn leaf aphids) produce approximately twenty times more progeny on inbred line B73 than on inbred line Mo17. Genetic mapping of this difference in maize aphid resistance identified quantitative trait loci (QTL) on chromosomes 4 and 6, with the Mo17 allele reducing aphid reproduction in each case. The chromosome 4 QTL mapping interval includes several genes involved in the biosynthesis of DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one), a maize defensive metabolite that also is required for callose accumulation in response to aphid feeding. Consistent with the known association of callose with plant defence against aphids, R. maidis reproduction on B73×Mo17 recombinant inbred lines was negatively correlated with both DIMBOA content and callose formation. Further genetic mapping, as well as experiments with near-isogenic lines, confirmed that the Mo17 allele causes increased DIMBOA accumulation relative to the B73 allele. The chromosome 6 aphid resistance QTL functions independently of DIMBOA accumulation and has an effect that is additive to that of the chromosome 4 QTL. Thus, at least two separate defence mechanisms account for the higher level of R. maidis resistance in Mo17 compared with B73. © 2014 The Author. Source

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