BOLD signal response in primary visual cortex to flickering checkerboard increases with stimulus temporal frequency in older adults

Many older adults have difficulty seeing brief visual stimuli which younger adults can easily recognize. The primary visual cortex (V1) may induce this difficulty. However, in neuroimaging studies, the V1 response change to the increase of temporal frequency of visual stimulus in older adults was unclear. Here we investigated the association between the temporal frequency of flickering stimuli and the BOLD activity within V1 in older adults, using surface-based fMRI analysis. The fMRI data from 29 healthy older participants stimulated by contrast-reversing checkerboard at temporal flicker frequencies of 2, 4, and 8 Hz were obtained. The participants also performed a useful field of view (UFOV) test. The slope coefficient of BOLD activity regarding the temporal frequency of the visual stimulus averaged within V1 regions of interest was positive and significantly different from zero. Group analysis in the V1 showed significant clusters with positive slope and no significant clusters with a negative slope. The correlation coefficient between the slope coefficient and UFOV performance was not significant. The results indicated that V1 BOLD response to a flickering visual stimulus increases as the stimulus temporal frequency increases from 2 to 8 Hz in older adults.

Does Timbre Modulate Visual Perception? Exploring Crossmodal Interactions

Musical timbre is often described using terms from non-auditory senses, mainly vision and touch; but it is not clear whether crossmodality in timbre semantics reflects multisensory processing or simply linguistic convention. If multisensory processing is involved in timbre perception, the mechanism governing the interaction remains unknown. To investigate whether timbres commonly perceived as “bright-dark” facilitate or interfere with visual perception (darkness-brightness), we designed two speeded classification experiments. Participants were presented consecutive images of slightly varying (or the same) brightness along with task-irrelevant auditory primes (“bright” or “dark” tones) and asked to quickly identify whether the second image was brighter/darker than the first. Incongruent prime-stimulus combinations produced significantly more response errors compared to congruent combinations but choice reaction time was unaffected. Furthermore, responses in a deceptive identical-image condition indicated subtle semantically congruent response bias. Additionally, in Experiment 2 (which also incorporated a spatial texture task), measures of reaction time (RT) and accuracy were used to construct speed-accuracy tradeoff functions (SATFs) in order to critically compare two hypothesized mechanisms for timbre-based crossmodal interactions, sensory response change vs. shift in response criterion. Results of the SATF analysis are largely consistent with the response criterion hypothesis, although without conclusively ruling out sensory change.

Anaplerotic flux into the Calvin-Benson cycle. Isotope evidence for in vivo occurrence in Helianthus annuus

As the central carbon uptake pathway in photosynthetic cells, the Calvin-Benson cycle is among the most important biochemical cycles for life on Earth. Recently, anaplerotic carbon flux (through the chloroplast-localised oxidative branch of the pentose phosphate pathway) into this cycle was proposed. Here, we measured intramolecular deuterium abundances in leaf starch of Helianthus annuus grown at varying ambient CO2 concentrations, Ca. Additionally, we modelled deuterium fractionations expected for the anaplerotic pathway and compared modelled with measured fractionations. We report deuterium fractionation signals at starch glucose H1 and H2. Below a response change point, these signals increase with decreasing Ca consistent with modelled fractionations by anaplerotic flux. Under normal growth conditions (Ca≥450 ppm corresponding to intercellular CO2 concentrations, Ci, ≥328 ppm), we estimate negligible anaplerotic flux. At Ca=180 ppm (Ci=140 ppm), we estimate that of the glucose 6-phosphate entering the starch biosynthesis pathway more than 11.5% is diverted into the anaplerotic pathway. In conclusion, we report evidence consistent with anaplerotic carbon flux into the Calvin-Benson cycle in vivo. We propose the flux may help to (i) maintain high levels of ribulose 1,5-bisphosphate under source-limited growth conditions to facilitate photorespiratory nitrogen assimilation required to build-up source strength and (ii) counteract oxidative stress.

Metabolism is the major driver of hydrogen isotope fractionation recorded in tree-ring glucose of Pinus nigra

- Stable isotope abundances convey valuable information about plant physiological processes and underlying environmental controls. Central gaps in our mechanistic understanding of hydrogen isotope abundances impede their widespread application within the plant and Earth sciences. - To close these gaps, we analysed intramolecular deuterium abundances in glucose of Pinus nigra extracted from an annually resolved tree-ring series (1961 to 1995). - We found fractionation signals at glucose H1 and H2 introduced by closely related metabolic processes. These signals (and thus metabolism) respond to drought and atmospheric CO2 concentration beyond a response change point. They explain ≈60% of the whole-molecule deuterium variability. Altered metabolism is associated with below-average yet not exceptionally low growth. - We propose the signals are introduced at the leaf-level by changes in sucrose-to-starch carbon partitioning and anaplerotic carbon flux into the Calvin-Benson cycle. In conclusion, metabolism can be the main driver of hydrogen isotope variation in plant glucose.

Leaf vs. Whole-Plant Biotic Attack: Does Vine Physiological Response Change?

Phylloxera is one of the most invasive and widespread insects in viticulture. An increase in populations feeding on leaves and/or roots of formerly resistant grapevines has been observed, but information on leaf and whole plant phylloxera infestation effects is lacking. We monitored the water and carbon metabolism of vines (one rootstock x scion combination) inoculated with insects’ eggs on leaves (L) or both leaves and roots (R+L). Nonstructural carbohydrates (NSC) in infested and noninfested tissue of different organs and plant biomass were measured at the end of the experiment. At the peak of the biotic stress treatment, the plants reduced transpiration by about 30% compared to control, while photosynthesis remained unaffected. Lower soluble NSC were measured in infested than in the nearby noninfested tissue of both L and R+L groups, suggesting sugar consumption by the insect, while infested roots increased starch content by fivefold. NSC were depleted in noninfested roots of R+L plants as well, giving strength to the hypothesis of intense metabolites translocation in favor of the insect. A more distinct physiological depression in R+L vines compared to L was highlighted, even if the total biomass reduction was more marked in L plants. Our preliminary results suggest that the insect reprograms plant metabolism stimulating a more conservative water use, while competing with the host plant for carbon resources. Further studies should validate current results and quantify the NSC invested in the plant’s defense against the pest.

Antioxidant increase by response surface optimization and Bayesian neural network modelling of pumpkin (Cucurbita moschata Duch) freezing

Pumpkin antioxidants have been found to benefit diabetics. This current study was attempted to optimize slow freezing treatment for a pumpkin to obtain maximum antioxidant gain using response surface methodology (RSM) and Bayesian regularized neural network (BRANN) approaches. A central composite design was used to generate the freezing experiment and to examine response change as a function of temperature and freezing time. Feedforward neural networks with a 2-15-1 structure were developed and trained using the Bayesian regularization algorithm. The results showed that the freezing data were well fitted to quadratic models generating R2 for total phenolic compounds (TPC), flavonoid of 0.850 and 0.857 respectively. The RSM optimized freezing of -20oC for 9 hrs were well confirmed to produce an increase in TPC and flavonoid by 54.44% and 60.4% respectively. The BRANN performances were found to be similar to that of RSM. While overfitting was mitigated during the supervised training, the BRANN model served excellent predictive and confirmatory tool for the optimization. In conclusion, slow freezing at -20oC for 9 hrs significantly increases TPC and flavonoid of pumpkin. This novel process may be adopted to provide healthier pumpkins food products for targeted consumers.

Increase in Free Hepatic Venous Pressure Response to Beta-Blockers Predicts Variceal Bleeding in Cirrhotic Patients

Background and Aims. Nonselective beta-blockers (NSBBs) are the main drug to prevent portal hypertension. It could alter free hepatic venous pressure (FHVP); however, the significance is unknown. This prospective study was to explore the change of FHVP after use of NSBBs and its predictive value for gastroesophageal varices (GOV) bleeding in cirrhotic patients. Patients and Methods. Cirrhotic patients with medium-large GOV between September 2014 and January 2019 were enrolled. After initial hepatic venous pressure gradient (HVPG) measurement, patients received oral NSBBs. Seven days later, the secondary HVPG was examined to evaluate the FHVP alteration and hemodynamic response. The variceal bleeding between patients with FHVP increased and decreased/unchanged was compared. Results. A total of 74 patients were enrolled, and 62 patients completed the secondary HVPG measurement and was followed up. The cumulative bleeding rate was significantly higher in patients with FHVP increased ≥ 1.75 mmHg than those with FHVP decreased/unchanged (54.5% vs. 22.5%, p = 0.021 ), while there was no significant difference in bleeding between HVPG responders and nonresponders (32.6% vs. 37.5%, p = 0.520 ). For HVPG responders, variceal bleeding in patients with FHVP increased ≥ 1.75 mmHg was significantly more than that in patients with FHVP decreased/unchanged (57.9% vs. 28.6%, p = 0.041 ). Cox regression analysis showed that change of FHVP was an independent predictor of variceal bleeding. Conclusion. Increase ≥ 1.75 mmHg in FHVP responding to beta-blockers in cirrhotic patients with GOV indicates high risk of variceal bleeding. Besides HVPG response, change of FHVP should also be valued in hemodynamic evaluation to beta-blockers. This trial is registered with Chinese Clinical Trial Registry ChiCTR-IPR-17012836.

Free neighborhood choice boosts socially optimal outcomes in stag-hunt coordination problem

Situations where independent agents need to align their activities to achieve individually and socially beneficial outcomes are abundant, reaching from everyday situations like fixing a time for a meeting to global problems like climate change agreements. Often such situations can be described as stag-hunt games, where coordinating on the socially efficient outcome is individually optimal but also entails a risk of losing out. Previous work has shown that in fixed interaction neighborhoods agents’ behavior mostly converges to the collectively inefficient outcome. However, in the field, interaction neighborhoods often can be self-determined. Theoretical work investigating such circumstances is ambiguous in whether the efficient or inefficient outcome will prevail. We performed an experiment with human subjects exploring how free neighborhood choice affects coordination. In a fixed interaction treatment, a vast majority of subjects quickly coordinates on the inefficient outcome. In a treatment with neighborhood choice, the outcome is dramatically different: behavior quickly converges to the socially desirable outcome leading to welfare gains 2.5 times higher than in the environment without neighborhood choice. Participants playing efficiently exclude those playing inefficiently who in response change their behavior and are subsequently included again. Importantly, this mechanism is effective despite that only few exclusions actually occur.