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27 result(s) for "Vidal, J.R"
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A real-time marker of object-based attention in the human brain. A possible component of a “gate-keeping mechanism” performing late attentional selection in the Ventro-Lateral Prefrontal Cortex
The decision to process an incoming stimulus attentively - and to trigger a follow-up cascade of high-level processes - is strategic for the human brain as it becomes transiently unavailable to subsequent stimulus processing. In this study, we set to identify brain networks that carry out such evaluations. We therefore assessed the time-course of neural responses with intracerebral EEG in human patients during an attentional reading task, contrasting to-be-attended vs. to-be-ignored items. We measured High-Frequency Activity [50–150 ​Hz] as a proxy of population-level spiking activity and we identified a crucial component of a Gate-Keeping Mechanism bilateral in the mid-Ventro-Lateral Prefrontal Cortex (VLPFC), at the interplay of the Ventral and Dorsal Attention Networks, that selectively reacts before domain specialized cortical regions that engage in full stimulus analysis according to task demands. •We identified a “gate-keeping mechanism”.•IFS is a central component of late attentional selection.•IFS involved in real-time monitoring object-based attention.
Post-depositional processes of elemental enrichment inside dark nodular masses of an ancient aeolian dune from A Coruña, Northwest Spain
This paper focuses on a residual ancient aeolian climbing dune from Punta Penaboa (A Coruña, Northwest Spain) showing evidence of post-depositional weathering, particularly the presence of dark brown nodular masses. The partitioning of trace elements between nodular masses and host sand during post-depositional weathering of the dune is investigated in this work, with the main objective of studying the elemental enrichment patterns in the dark masses. Data of the concentrations of chemical elements were obtained by instrumental neutron activation analysis (INAA) and complemented by mineralogical and microchemical studies, using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) / energy dispersive X-ray spectrometry (EDS). The dune was dated by optically stimulated luminescence (OSL) , yielding an age of 300ka B.P.. The dark nodular masses preserved the dune sand structure, without defined concentric layers, suggesting an early stage of formation. They consist mainly of quartz grains cemented by clay materials enriched in the majority of the elements studied, especially in Mn, Co, Ba, Sb, Ce, Tb, Th, As, Zr and Hf. The post-depositional transformations of the dune were most likely influenced by migration of chemical compounds from the surrounding slope deposits and granitic rocks, as well as microbial activity that promoted metals concentration in the solutions percolating through the pore network of the dune. Seasonal changes in the redox potential were required to produce the accumulation of Mn and other trace elements in the dune pore network and to promote the fractionation between Ce4+ and trivalent rare earth elements that was observed in the geochemical patterns.
Geochemical and geochronological constraints on the geologic evolution of the western Sonobari Complex, northwestern Mexico
In the southern Sierra Sonobari, NW Mexico, U-Pb and 40Ar/39Ar geochronology studies allowed to define the provenance and maximum depositional age of the Francisco Gneiss basement of the Sonobari terrane, and to establish the age of some magmatic events in that area. The youngest zircon cluster in paragneisses of the Francisco Gneiss indicates a maximum depositional age of 509 ± 29Ma. The main peaks of the relative probability plot yield ages of 1690 and 1404Ma with minor peaks at 1156, 921, and 517Ma. Major peaks suggest that the main source of sediments was the Paleo- and Mesoproterozoic crust of Laurentia. Orthogneiss from the Francisco Gneiss yields a U-Pb zircon upper intercept age of 248 ± 28Ma, which is interpreted as the crystallization age. Crosscutting dykes of metabasite yield an 40Ar/39Ar age of 67 ± 5Ma, which is interpreted as indicating cooling after either a latest Early Cretaceous orogenic event or Late Cretaceous contact metamorphism. Granodiorite intruding the Francisco Gneiss yields a U-Pb age of 64 ± 1Ma, which is interpreted as a magmatic age. The hornblende-plagioclase Macochin Gabbro yields 40Ar/39Ar isochron ages of 54 ± 10Ma and 47 ± 5Ma, which are interpreted as cooling ages after the gabbro intrusion. Geochemical data indicate that the mafic rocks of the Francisco Gneiss correspond to subalkaline basalts of tholeiitic affinity with concentrations of high field strength elements similar to oceanic basalts, suggesting an asthenospheric upper mantle source. However, according to the variation in Th/Yb and U/Yb, the amphibolites display a significant influence of the upper continental crust. The Macochin Gabbro also has a geochemical signature characteristic of subalkaline basalt with tholeiitic affinity, and high field strength elements similar to oceanic basalts. Tectonic discrimination diagrams and elemental distribution suggest that the mafic rocks of both the Francisco Gneiss and Macochin Gabbro were emplaced during rifting in a back-arc setting.
Turning visual shapes into sounds: Early stages of reading acquisition revealed in the ventral occipitotemporal cortex
The exact role of the left ventral occipitotemporal cortex (VOTC) during the initial stages of reading acquisition is a hotly debated issue, especially regarding the comparative effect of learning on early stimulus-dependent vs. later task-dependent processes. We show that this controversy can be solved with high-temporal resolution intracerebral EEG recordings of the VOTC. We measured High-Frequency Activity (50–150Hz) as a proxy of population-level spiking activity while participants learned Japanese Katakana symbols, and found that learning primarily affects top-down/task-dependent neural processing, after a few minutes only. In contrast, adaptation of early bottom-up/stimulus-dependent processing takes several days to adapt and provides the basis for fluent reading. Such evidence that two consecutive stages of neural processing, stimulus- and task-dependent are differentially affected by learning, can reconcile seemingly opposite hypotheses on the role of the VOTC during reading acquisition. •Fine neural dynamics of reading acquisition revealed in the VOTC.•Dissociation between early stimulus- and late task-dependent neural processing.•Early reading acquisition affects primarily task-dependent neural processing.•Reconciliation between the two influential theories of the VOTC role during reading.
Multidisciplinary study of the quaternary deposits of the Vila Nova de Gaia, NW Portugal, and its climate significance
Palynological, geochronological, and sedimentological analyses were conducted on samples from different depositional units of well-preserved marine, fluvial and palustrine sedimentary deposits from Vila Nova de Gaia located at the northwestern Portuguese coast. The studied deposits occur on two terraces: Terrace A—Lavadores (18 m to 33 m) and Terrace B—Canidelo (50 m). Chronological and sedimentological features allowed to date the deposits to the Upper Pleistocene until the last glacial period, being observed an evolution from a depositional setting in a marine intertidal zone, passing to a fluvial environment and ending in a palustrine/lagunar environment with possible periglacial influence. Pollen assemblages collected in the fluvial sedimentary horizons also suggested changes in the environmental conditions. A pollen content with good representation of arboreal species ( Quercus , Pinus , Castanea , Fraxinus, Salix , Betula and Corylus ), changed to a vegetation environment dominated by non-arboreal species, such as Poaceae, Plantago and Asteraceae. The top horizons, corresponding to a palustrine/lagunar environment, presented a pollen profile completely dominated by non-arboreal species, with minimal tree representation ( Prunus , Quercus , Pinus and Castanea ) which, combined with sedimentological characteristics may point to a more dry and cold climate than nowadays.
Evaluation of Transgenic 'Chardonnay' (Vitis vinifera) Containing Magainin Genes for Resistance to Crown Gall and Powdery Mildew
Magainins, short peptides with broad-spectrum antimicrobial activity in vitro, were assayed for their ability to confer resistance to pathogens in transgenic grapevines. Embryogenic cell suspensions of 'Chardonnay' (Vitis vinifera L.) were co-transformed by microprojectile bombardment with a plasmid carrying the npt-II gene and a second plasmid harboring either a natural magainin-2 (mag2) or a synthetic derivative (MSI99) gene. Magainin genes and the marker gene were driven by Arabidopsis ubiquitin-3 and ubiquitin-11 promoters, respectively. A total of 10 mag2 and 9 MSI99 regenerated lines were studied by Southern blot hybridization, which showed 1-6 transgene integration events into the plant genome. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed a variable range in transcription levels among mag2 and MSI99 lines. A positive correlation between number of integration events and transcription level was observed (p<0.05). Plants were acclimated and challenged in the greenhouse with either Agrobacterium vitis strains (bacterial crown gall pathogen) at 10(8) cfu/ml or Uncinula necator (fungal powdery mildew pathogen) at 10(5) conidia/ml for evaluation of disease resistance. A total of 6 mag2 and 5 MSI99 lines expressing the antimicrobial genes exhibited significant reductions of crown gall symptoms as compared to non-transformed controls. However, only two mag2 lines showed measurable symptom reductions in response to U. necator, but not strong resistance. Our results suggest that the expression of magainin-type genes in grapevines may be more effective against bacteria than fungi. Additional strategies to enhance transgene expression and the spectrum of resistance to grape diseases are suggested.
Biolistic transformation of grapevine using minimal gene cassette technology
The use of minimal gene cassettes (MCs), which are linear DNA fragments (promoter+open reading frame+terminator) lacking the vector backbone sequence, was compared to the traditional use of whole circular plasmids (CPs) for transformation of grapevine. Embryogenic cell suspensions of 'Chardonnay' (Vitis vinifera L.) were transformed via particle co-bombardment using two nonlinked genes in either MCs or CPs. One construct contained the npt-II selectable marker and the second construct contained the MSI99 antimicrobial peptide gene. A total of five lines each from MC and CP treatments that showed positive signals by PCR for both the npt-II and MSI99 genes were selected. Southern blot analyses revealed up to five integration events in the DNA treatments. Transcription levels determined by semi-quantitative RT-PCR varied among transgenic lines. No significant differences were found in transgene transcription between lines from MC and CP transformation. The correlation between npt-II and MSI99 transcription levels was positive (P<0.05), however, no correlation between the transcription level and the number of integration events was observed. Transgenic lines presented a similar phenotype in leaf morphology and plant vigor compared to non-transgenic lines. Moreover, transgenic lines from both MC and CP DNA treatments produced fruit as did the non-transgenic lines in the third year of growth in the greenhouse. Our data confirm the effectiveness of the minimal cassette technology for genetic transformation of grapevine cultivars.
Joint Use of GPR and ERI to Image the Subsoil Structure in a Sandy Coastal Environment
In the present work we show a study carried out in a coastal sandy environment in NW Spain with the main aim of imaging the shallow subsoil structure. The goals of the study included the detection of the water table and bedrock, but also a description of the aeolian dunes and progradating sand layers. With these objectives two independent but complementary geophysical techniques were jointly used: ground-penetrating radar (GPR) and electrical resistivity imaging (ERI). Regarding GPR, shielded antennas of 200 & 250 MHz from two different manufacturers were used in the study; it also allowed us to make a comparative study between them. To obtain a more detailed image of the sand layers structure it was also used a shielded 500 MHz antenna. 100 & 200 MHz unshielded antennas were also used to apply the CMP method in order to obtain a precise estimation of the velocity of the electromagnetic waves into the subsoil. ERI was carried out in order to obtain independent estimations of both water table and bedrock depths, as well as the resistivity values of the groundwater water that are useful to determine the occurrence -or not- of fresh water on marine water. Although the resolution of ERI is low comparing with GPR, the penetration depth is greater. The results show that the bedrock is clearly identified in ERI profiles at about 8-9 m depth, whereas the water table is located at 5-6 m depth in good agreement with the GPR profiles. Resistivity values in the most external ERI profiles show that the water table is constituted by fresh water. In addition to this, the high resolution of both 200-250 and 500 Mhz antennae has allowed to obtain a clear image of the internal structure of the sand deposits. This information has been used to infer the dynamic of progradation of the coastal system.
Fluvial terraces of the northwest Iberian lower Miño River
A new fluvial terrace map with a tectonic framework for the northwest Iberian lower Miño River is presented. It is the first integrated map to cover the entire lower, 67-km reach of the Miño River, and to cover both the Spanish and Portuguese side of the river. The map is presented at a scale of 1:200,000, although its features were mapped at a scale of 1:5000. Various map layers can be viewed, such as a digital elevation model (DEM), fluvial sediment thickness layers, a palaeoflow direction layer, a lineament and fault layer, and two terrace and tectonic basin layers, showing up to 10 fluvial terraces and a floodplain level. Interpretation of the map shows that next to regional tectonic uplift and glacioeustacy, local basin subsidence and small-scale block movement are very important for the fluvial network, localised fluvial terrace formation, and preservation.