Shift In Dominance Research Articles

Tree mycorrhizal type controls over soil water-extractable organic matter quantity and biodegradation in a subtropical forest of southern China

Tree mycorrhizal type is believed to be a key factor controlling soil organic matter dynamics in forests, yet its effects on soil dissolved organic matter (DOM) quantity and biodegradation remain unknown, especially in sub/tropical forests. Here, we used soil water-extractable organic matter (WEOM) as a proxy for soil DOM, and measured water-extractable organic carbon (WEOC), total nitrogen (WETN), and total phosphorus (WETP) concentrations, and WEOM chemical composition (i.e., aromaticity and molecular weight) in the 0–10 cm and 10–30 cm mineral soil depths along the gradient ranging from arbuscular mycorrhizal (AM)- to ectomycorrhizal (ECM)-associated tree dominance in a subtropical secondary forest of southern China. Subsequently, we assessed soil WEOM biodegradation using a 42-day aerobic incubation experiment. At each soil depth, WEOC concentration and WEOC:WETN ratio increased with increasing ECM tree dominance, whereas WEOM aromaticity and molecular weight exhibited an opposite changing trend. Moreover, WEOC concentration correlated positively with soil organic C, total N, total P, and sand content, but correlated negatively with soil pH and clay and silt contents. Soil WEOM biodegradation did not change with ECM tree dominance in 0–10 cm depth but decreased with increasing ECM tree dominance in 10–30 cm depth. Soil WEOM biodegradation was negatively related to WEOC:WETP and WETN:WETP ratios, but was positively related to WEOM aromaticity and molecular weight. These findings suggested that tree mycorrhizal type is a potential indicator of soil DOM concentration and biodegradation, and highlight that the shifts in dominance of AM- and ECM-associated trees will influence soil DOM dynamics by altering soil texture, C:N:P stoichiometry, and C quality in subtropical forests.

Ecological divergence of syntopic marine bacterial species is shaped by gene content and expression

Identifying mechanisms by which bacterial species evolve and maintain genomic diversity is particularly challenging for the uncultured lineages that dominate the surface ocean. A longitudinal analysis of bacterial genes, genomes, and transcripts during a coastal phytoplankton bloom revealed two co-occurring, highly related Rhodobacteraceae species from the deeply branching and uncultured NAC11-7 lineage. These have identical 16S rRNA gene amplicon sequences, yet their genome contents assembled from metagenomes and single cells indicate species-level divergence. Moreover, shifts in relative dominance of the species during dynamic bloom conditions over 7 weeks confirmed the syntopic species’ divergent responses to the same microenvironment at the same time. Genes unique to each species and genes shared but divergent in per-cell inventories of mRNAs accounted for 5% of the species’ pangenome content. These analyses uncover physiological and ecological features that differentiate the species, including capacities for organic carbon utilization, attributes of the cell surface, metal requirements, and vitamin biosynthesis. Such insights into the coexistence of highly related and ecologically similar bacterial species in their shared natural habitat are rare.

NNOS-induced tyrosine nitration of TRKB impairs BDNF signaling and restrains neuronal plasticity.

Nitric oxide (NO) has been long recognized as an important modulator of neural plasticity, but characterization of the molecular mechanisms involved - specially the guanylyl cyclase-independent ones - has been challenging. There is evidence that NO could modify BDNF-TRKB signaling, a key mediator of neuronal plasticity. However, the mechanism underlying the interplay of NO and TRKB remains unclear. Here we show that NO induces nitration of the tyrosine 816 in the TRKB receptor in vivo and in vitro, and that post-translational modification inhibits TRKB phosphorylation and binding of phospholipase Cγ1 (PLCγ1) to this same tyrosine residue. Additionally, nitration triggers clathrin-dependent endocytosis of TRKB through the adaptor protein AP-2 and ubiquitination, thereby increasing translocation of TRKB away from the neuronal surface and directing it towards lysosomal degradation. Accordingly, inhibition of nitric oxide increases TRKB phosphorylation and TRKB-dependent neurite branching in neuronal cultures. In vivo, chronic inhibition of neuronal nitric oxide synthase (nNOS) dramatically reduced TRKB nitration and facilitated TRKB signaling in the visual cortex, and promoted a shift in ocular dominance upon monocular deprivation - an indicator of increased plasticity. Altogether, our data describe and characterize a new molecular brake on plasticity, namely nitration of TRKB receptors.

Competition in a changing world: invasive aquatic plant is limited by saltwater encroachment

AbstractCompetitive interactions between native and nonindigenous species occur under conditions of ongoing environmental alterations related to urbanization and climate change, presenting a challenge to understanding invasiveness. Indigenous submerged aquatic vegetation species have been negatively impacted by nutrient enrichment and saltwater intrusion, while simultaneously experiencing a rapid spread in nonindigenous competitors. To better predict future shifts in freshwater macrophyte community dominance, investigations need to consider how these multiscale disturbances influence competitiveness of nonindigenous macrophytes. Using an outdoor greenhouse mesocosm setup for approximately 19 weeks over the course of subtropical winter, we experimentally examined how nutrient enrichment, salinity, and the interaction of both factors influence the competitive interactions between a native macrophyte with moderate salinity tolerance, wild celery (Vallisneria americana), and a highly invasive macrophyte with lower salinity tolerance, hydrilla (Hydrilla verticillata). We tested the factors of macrophyte composition (hydrilla monoculture, wild celery monoculture, or biculture), salinity (0, 4, or 8), and fertilization (ambient or fertilized) on biomass production, biomass allocation, and morphological metrics as responses to environmental condition and interspecific competition. Fertilizer enhanced wild celery leaf area (more than twofold) and shifted allocation toward aboveground biomass, but did not enhance hydrilla competitiveness. Salinity negatively affected wild celery leaf area (by 7.5%–67.8%) and biomass (by 4%–15%) and also reduced hydrilla belowground biomass production (by 6%–25%) but did not influence competition. An interaction effect of fertilizer and salinity negatively influenced hydrilla growth, however the combined factors did not influence competitive outcomes. The lack of evidence for a competitive advantage by hydrilla in this study demonstrates that salinity exposure sufficiently limits a highly invasive plant's competitive abilities and subsequent suppression of a native species.

Advancing interdisciplinary science for disrupting wildlife trafficking networks

Wildlife trafficking, whether local or transnational in scope, undermines sustainable development efforts, degrades cultural resources, endangers species, erodes the local and global economy, and facilitates the spread of zoonotic diseases. Wildlife trafficking networks (WTNs) occupy a unique gray space in supply chains—straddling licit and illicit networks, supporting legitimate and criminal workforces, and often demonstrating high resilience in their sourcing flexibility and adaptability. Authorities in different sectors desire, but frequently lack knowledge about how to allocate resources to disrupt illicit wildlife supply networks and prevent negative collateral impacts. Novel conceptualizations and a deeper scientific understanding of WTN structures are needed to help unravel the dynamics of interaction between disruption and resilience while accommodating socioenvironmental context. We use the case of ploughshare tortoise trafficking to help illustrate the potential of key advancements in interdisciplinary thinking. Insights herein suggest a significant need and opportunity for scientists to generate new science-based recommendations for WTN-related data collection and analysis for supply chain visibility, shifts in illicit supply chain dominance, network resilience, or limits of the supplier base.

Potential effects of future climate change on global reptile distributions and diversity

AbstractAimUntil recently, complete information on global reptile distributions has not been widely available. Here, we provide the first comprehensive climate impact assessment for reptiles on a global scale.LocationGlobal, excluding Antarctica.Time period1995, 2050 and 2080.Major taxa studiedReptiles.MethodsWe modelled the distribution of 6296 reptile species and assessed potential global and realm‐specific changes in species richness, the change in global species richness across climate space, and species‐specific changes in range extent, overlap and position under future climate change. To assess the future climatic impact on 3768 range‐restricted species, which could not be modelled, we compared the future change in climatic conditions between both modelled and non‐modelled species.ResultsReptile richness was projected to decline significantly over time, globally but also for most zoogeographical realms, with the greatest decreases in Brazil, Australia and South Africa. Species richness was highest in warm and moist regions, with these regions being projected to shift further towards climate extremes in the future. Range extents were projected to decline considerably in the future, with a low overlap between current and future ranges. Shifts in range centroids differed among realms and taxa, with a dominant global poleward shift. Non‐modelled species were significantly stronger affected by projected climatic changes than modelled species.Main conclusionsWith ongoing future climate change, reptile richness is likely to decrease significantly across most parts of the world. This effect, in addition to considerable impacts on species range extent, overlap and position, was visible across lizards, snakes and turtles alike. Together with other anthropogenic impacts, such as habitat loss and harvesting of species, this is a cause for concern. Given the historical lack of global reptile distributions, this calls for a re‐assessment of global reptile conservation efforts, with a specific focus on anticipated future climate change.

Ketamine and its metabolite 2R,6R-hydroxynorketamine promote ocular dominance plasticity and release tropomyosin-related kinase B from inhibitory control without reducing perineuronal nets enwrapping parvalbumin interneurons.

Ketamine has been described as a fast-acting antidepressant, exerting effects in depressed patients and in preclinical models with a rapid onset of action. The typical antidepressant fluoxetine is known to induce plasticity in the adult rodent visual cortex, as assessed by a shift in ocular dominance, a classical model of brain plasticity, and a similar effect has been described for ketamine and its metabolite 2R,6R-hydroxynorketamine (R,R-HNK). Here, we demonstrate that ketamine (at 3 or 20 mg/kg) and R,R-HNK facilitated the shift in ocular dominance in monocularly deprived mice, after three injections, throughout the 7-day monocular deprivation regimen. Notably, the comparison between the treatments indicates a higher effect size of R,R-HNK compared with ketamine. Treatment with ketamine or R,R-HNK failed to influence the levels of perineuronal nets (PNNs) surrounding parvalbumin-positive interneurons. However, we observed in vitro that both ketamine and R,R-HNK are able to disrupt the tropomyosin-related kinase B (TRKB) interaction with the protein tyrosine phosphatase sigma (PTPσ), which upon binding to PNNs dephosphorylates TRKB. These results support a model where diverse drugs promote the reinstatement of juvenile-like plasticity by directly binding TRKB and releasing it from PTPσ regulation, without necessarily reducing PNNs deposits.

The Renaissance of Mixed Forests? New Insights Into Shifts in Tree Dominance and Composition Following Centuries of Human-induced Simplification of Iberian Forests

Anthropic activities have modelled and simplified southern European forest landscapes for centuries. Over recent decades, new drivers related to human-mediated global change have induced the redistribution of tree species and an increase in more complex forests. However, the current large-scale patterns and drivers of these changes are yet to be fully described for the Mediterranean Basin. In this frame, this work identifies and examines changes in dominance and composition from pure to mixed forests across bioclimatic gradients and forest types in Iberian forests over recent decades based on data from the Spanish National Forest Inventory from 1960 to 2020. Then, considering different environmental, anthropic, and disturbance variables we also identify some of the most important drivers associated with the shifts observed from 1986 to 2020. Our results confirm an ongoing increase in mixed forests involving the replacement of conifers by broadleaved species. These shifts are greater in the Atlantic biogeoregion and in pure broadleaved deciduous forests. Climate warming-associated disturbances such as drought severity together with land use legacies and forest types showed the strongest relationships with the observed changes in the studied forests. Our results support the premise put forward by palaeoecologists which states that the increase in tree mixtures is a natural process reversing the historical human-induced simplification of Iberian forests. The increasing importance of mixed forest in southern Europe makes decisive the revision of forest classifications as well as forest management and conservation plans in order to include these increasingly abundant novel stands in forest policies.

Internal neural states influence the short-term effect of monocular deprivation in human adults.

The adult human visual system maintains the ability to be altered by sensory deprivation. What has not been considered is whether the internal neural states modulate visual sensitivity to short-term monocular deprivation. In this study we manipulated the internal neural state and reported changes in intrinsic neural oscillations with a patched eye open or closed. We investigated the influence of eye open/eye closure on the unpatched eye's contrast sensitivity and ocular dominance (OD) shifts induced by short-term monocular deprivation. The results demonstrate that internal neural states influence not only baseline contrast sensitivity but also the extent to which the adult visual system can undergo changes in ocular dominance.

Inconsistent stoichiometry and growth responses of two coexisting dominant species to various N and P supplies in a supratidal wetland of the Yellow River Delta

The availability and stoichiometry ratio of nitrogen (N) and phosphorus (P) play vital roles in plant trophic dynamics and primary production. However, the responses of these plant traits to varying N and P supplies remain largely unclear for supratidal wetland herbs. Here, we conducted a 4-year field manipulation experiment in a supratidal wetland in the Yellow River Delta. The changes in aboveground biomass, leaf N and P concentrations and N:P ratios of two dominant herbs (Suaeda glauca and Phragmites australis) were examined at 3 overall nutrient supply levels (low, medium and high) combined with 3 N:P supply ratios (5:1, 15:1 and 45:1). The results showed that the leaf trophic dynamics of the two dominant species rely on the overall supply level as well as on the N:P supply ratio, while the aboveground biomass of both species was only significantly influenced by the overall supply level. With the increase in supply level, S. glauca gained an advantage over P. australis in aboveground biomass competition. The leaf N and P concentrations of both species raised with the respective increasing nutrient inputs, and N:P improved with the increasing supply ratio. The leaf stoichiometry of S. glauca was more strongly influenced by the various N and P supplies than that of P. australis. Specifically, the gap of nutrient contents between the two species widened as nutrient availability improved, with the dominance of S. glauca increasing while that of P. australis decreasing. This species-specific response may explain the altered aboveground biomass of the two species. Our findings suggested that changing the N and P supply can potentially influence primary productivity by changing leaf nutrient status, indirectly affecting the shifts in plant dominance and community composition in supratidal wetland ecosystems.

Effect of Plankton Composition Shifts in the North Atlantic on Atmospheric pCO2

AbstractMarine carbon cycle processes are important for taking up atmospheric CO2 thereby reducing climate change. Net primary and export production are important pathways of carbon from the surface to the deep ocean where it is stored for millennia. Climate change can interact with marine ecosystems via changes in the ocean stratification and ocean circulation. In this study we use results from the Community Earth System Model version 2 (CESM2) to assess the effect of a changing climate on biological production and phytoplankton composition in the high latitude North Atlantic Ocean. We find a shift in phytoplankton type dominance from diatoms to small phytoplankton which reduces net primary and export productivity. Using a conceptual carbon‐cycle model forced with CESM2 results, we give a rough estimate of a positive phytoplankton composition‐atmospheric CO2 feedback of approximately 60 GtCO2/°C warming in the North Atlantic which lowers the 1.5° and 2.0°C warming safe carbon budgets.

Dominant source areas shift seasonally from longitudinal to lateral contributions in a montane headwater stream

Montane ecoregions are important vehicles for downstream hydrologic function, but their dynamics are relatively understudied compared to alpine and subalpine catchments in the western United States. Montane catchments experience shifts in precipitation inputs seasonally, which results in spatiotemporal differences in source area contributions to the stream. We collected hydrometric and geochemical data between 2018 and 2021 from a 2.65 km2 semi-arid headwater catchment in the Front Range of Colorado, USA. Using a combined approach of hydrometric monitoring, geochemical characterization, and end-member mixing analysis (EMMA), we assess hydrologic connectivity between areas with high upslope accumulation and the stream. Within our study area, high upslope accumulation area corresponded to alluvial/ colluvial fans wherein we focused instrumentation and water sample collection. Using observed rainfall, and multiyear measurements of groundwater levels, soil moisture, and streamflow, we observed distinct hydrologic seasons within our catchment characterized by snowmelt during the spring, rainstorms during the summer, and a return to baseflow during the fall. Within this framework, we found that source areas to streamflow shift with longitudinal distance downstream, and among hydrologic seasons. Notably, our EMMA results indicate that contributions from upstream source areas become less important than lateral inputs from spring snowmelt into the fall return to baseflow. This was most pronounced at the upper catchment where upstream contributions to streamflow decreased up to 33.3% between spring and fall. These results suggest that streamflow is maintained by local source areas contributing laterally and vertically. Our results reflect dynamic shifts in hydrologic connectivity in space and in time, which are increasingly important to land and water resource management given rapid climate changes within the western United States.

Biofloc colors as an assessment tool for water quality in shrimp farming with BFT systems

In shrimp farming using biofloc technology it is common to observe a gradual swap in the biofloc colors from green to brown along with shifts in water quality throughout the culture cycle. This change reflects a dominance shift from an autotrophic to a heterotrophic microbial community, resulting mainly from changes in system C:N and N:P ratios. Notwithstanding the ease of the direct analysis of biofloc color, no assessment of its potential as a proxy of water quality has been done so far. Therefore, our aim was to develop a standardized protocol to determine the potential of using the microbial community color index (MCCI) to develop an easy, fast, and low-cost assessment of water quality of intensive marine shrimp farming using biofloc systems. In this study, water quality data were collected from 17 tanks and the biofloc color was obtained from images after filtering with the help of an apparatus built with materials accessible to shrimp producers. We developed and standardized a methodology for reading the average RGB (Red, Green, and Blue) values from pixels of bioflocs images and used this methodology to calculate their average MCCIs. Based on this quantification of colors, it was possible to calculate a correlation matrix among MCCI and several water quality variables. The MCCI was positively correlated with the concentration of carbon, nitrogen, and phosphorus concentration in the bioflocs, total suspended solids, settleable solids and total phosphorus and negatively correlated with water transparency and G (green) values. The MCCI association with important water quality variables was expected for this type of system, in which the dominance by heterotrophic bacteria occurs at the final stages of biofloc succession, during which the system undergoes nutrient accumulation, shifting the bioflocs color from green to brown shades. Thus, it was observed that the water quality variables correlated with the MCCI were those that varied according to the culture stage. Another important result was that artificial images generated from images’ average RGB yielded satisfactory results regarding the similarity to the original images. Therefore, since it is possible to estimate water quality variables from the biofloc colors, this method lays the foundation for the future development of a practical tool (color scale or mobile app) for water quality evaluation. Shrimp farmers can use it to conduct a cheap and fast assessment of water quality of their tanks and take better decisions about critical aspects such as fertilization, water renewal or mechanical removal of excessive concentration of bioflocs.

Technological Leadership in Industry 4.0: A Comparison Between Manufacturing and ICT Sectors Among Korean Firms

This paper examines the technological structures of the manufacturing and the ICT sectors in Korea to examine the potential shift of dominant technological sectors in the era of the Fourth Industrial Revolution (4IR). By using patent data of Korean firms from 1990 to 2021, we find that the manufacturing sector has been the dominant technological leader in Korea in terms of both the number of patents and the diversity of technologies, even in the era of 4IR. Although the ICT sector has shown an increasing focus on Industry 4.0 (I4) technologies after the 2000s, indicating the potential for a shift in dominance in the future, the gap between the two sectors is still significant. The study also reveals that the manufacturing sector tends to diversify technologies, while the ICT sector specializes in several target technologies. Our analysis also suggests that both sectors exhibit path-dependency, with the ICT sector exhibiting stronger characteristics, and firms in both sectors exhibit the tendency of intensive and extensive margin in their patenting activities, but this tendency is stronger for firms in the manufacturing sector.

Performance Improvement of Mechanically Beam-Steerable Transmitarray Antennas by Using Offset Unifocal Phase Symmetry

This communication presents the concept of offset unifocal phase symmetry to improve the performance (gain, gain roll-off, sidelobe level, etc.,) of mechanically beam-steerable transmitarray (TA) antennas. The phase shifts are initially determined from an offset feed source to make the corresponding TA antenna radiate a tilted beam with high gain. The phase shifts are asymmetric and can be broadly divided into dominant and ordinary phase shifts with respect to the offset feed source. By mirroring the dominant phase shifts to make the phase shifts symmetric, it can enable symmetric radiation beams for symmetric offset feed sources and improve phase error. When the offset feed source is moving inward to steer the main beam, the phase error of the phase-shifting surface with respect to the feed source starts to occur, while the electric-field spillover/illumination from the feed source is improved, which can maintain the gains of scanning beams. To verify the validity of the concept, the performance of a beam-steerable TA antenna enabled by the offset unifocal phase symmetry has been simulated and compared with the counterparts of unifocal and bifocal beam-steerable TA antennas. The measured results agree well with the simulated ones, revealing that the beam-steerable TA antenna enabled by the offset unifocal phase symmetry can maintain realized gains of scanning beams, suppress sidelobe levels, and reduce gain roll-off within the beam-scanning coverage. The offset unifocal phase symmetry, in principle, is a generalized approach and applicable to reflectarray antennas to improve the beam-steerable performance as well.

Mesozooplankton community responses to a large-scale harmful algal bloom induced by the non-indigenous dinoflagellate Lingulodinium polyedra

Our understanding of how zooplankton community composition varies in relation to harmful algal blooms remains limited, particularly in ecosystems where toxin-producing algae may have been introduced through anthropogenic activities. Harmful algal blooms (HABs) naturally occur on the coast of southern Africa, where they are predominantly associated with the cold Benguela region. In the warm-temperate waters east of Cape Agulhas, HABs occur rarely and red tides are mostly associated with the non-toxin producing dinoflagellate Noctiluca scintillans. Blooms of N. scintillans may cause water discolouration, but this is generally short-lived with limited impact on the ecosystem. However, in December 2013 the eastern Agulhas region experienced an extensive HAB, which persisted for ca. 4 months and affected >500 km of coastline, from Wilderness to East London. This unprecedented event was caused by the non-indigenous toxin-producing dinoflagellate, Lingulodinium polyedra. The impact on the coastal seas was widespread and severe, with instances of low dissolved O2 levels and fish kills being reported at the time in the broader Algoa Bay area. This study investigated the impact of the L. polyedra bloom on the mesozooplankton of Algoa Bay and reports the successive changes in zooplankton community composition and biomass observed from July 2013 to July 2014. The bloom impacted species diversity and richness, with a marked shift in dominance from a calanoid copepod dominated community to one dominated by microzooplankton (specifically cyclopoid copepods, tintinnids and cladocerans), over the period November 2013–March 2014. Calanoid copepod abundance was significantly reduced throughout Algoa Bay with the progression of the bloom, and this significantly impacted the total zooplankton biomass of the region. The results of the study suggest that harmful algal blooms have a negative impact on zooplankton communities, with notable implications for the higher trophic levels of the coastal pelagic ecosystem.

Non-invasive optical characterization and detection of CA 15-3 breast cancer biomarker in blood serum using monoclonal antibody-conjugated gold nanourchin and surface-enhanced Raman scattering.

A proof-of-concept of colloidal surface-enhanced Raman scattering (SERS) substrate for rapid selective detection of overexpressed CA 15-3 biomarker in breast cancer serum (BCS) is suggested using PEGylated gold nanourchins (GNUs) conjugated with anti-CA 15-3 monoclonal antibody (mAb). UV-vis spectroscopy provided conformational information about mAb where the initial aromatic amino acid peak was red-shifted from 271 to 291nm. The fluorescence peak of tyrosine in mAb was reduced by ≈ 77%, and red-shifted by ≈ 3nm after incubation in BCS. Fourier transform near-infrared spectroscopy and SERS were used to study the composition and the molecular structure of the mAb and BCS. Some of the most dominant Raman shifts after GNU-PEG-mAb interaction with BCS are 498, 736, 818, 1397, 1484, 2028, 2271, and 3227cm-1 mainly corresponding to C-N-C in amines, vibrational modes of amino acids, C-H out-of-plane bend, C-O stretching carboxylic acid, the vibrational mode in phospholipids, NH3+ amine salt, C≡N stretching in nitriles, and O-H stretching. The intensity of SERS signals varied per trial due to the statistical behavior of GNU in BCS, agglomeration, laser power, and the heating effect. Despite very small amount of plasmonic heating, the result of the ANOVA test demonstrated that under our experimental conditions, the heating effect on signal variation is negligible and that the differences in the laser power are insignificant for all SERS observations (p > 0.6); thus, other parameters are responsible. The absorbance of mAb-conjugated GNU was decreased after five minutes of irradiation at 8 mW in the BCS.

Luminance Contrast Shifts Dominance Balance between ON and OFF Pathways in Human Vision.

Human vision processes light and dark stimuli in visual scenes with separate ON and OFF neuronal pathways. In nature, stimuli lighter or darker than their local surround have different spatial properties and contrast distributions (Ratliff et al., 2010; Cooper and Norcia, 2015; Rahimi-Nasrabadi et al., 2021). Similarly, in human vision, we show that luminance contrast affects the perception of lights and darks differently. At high contrast, human subjects of both sexes locate dark stimuli faster and more accurately than light stimuli, which is consistent with a visual system dominated by the OFF pathway. However, at low contrast, they locate light stimuli faster and more accurately than dark stimuli, which is consistent with a visual system dominated by the ON pathway. Luminance contrast was strongly correlated with multiple ON/OFF dominance ratios estimated from light/dark ratios of performance errors, missed targets, or reaction times (RTs). All correlations could be demonstrated at multiple eccentricities of the central visual field with an ON-OFF perimetry test implemented in a head-mounted visual display. We conclude that high-contrast stimuli are processed faster and more accurately by OFF pathways than ON pathways. However, the OFF dominance shifts toward ON dominance when stimulus contrast decreases, as expected from the higher-contrast sensitivity of ON cortical pathways (Kremkow et al., 2014; Rahimi-Nasrabadi et al., 2021). The results highlight the importance of contrast polarity in visual field measurements and predict a loss of low-contrast vision in humans with ON pathway deficits, as demonstrated in animal models (Sarnaik et al., 2014).SIGNIFICANCE STATEMENT ON and OFF retino-thalamo-cortical pathways respond differently to luminance contrast. In both animal models and humans, low contrasts drive stronger responses from ON pathways, whereas high contrasts drive stronger responses from OFF pathways. We demonstrate that these ON-OFF pathway differences have a correlate in human vision. At low contrast, humans locate light targets faster and more accurately than dark targets but, as contrast increases, dark targets become more visible than light targets. We also demonstrate that contrast is strongly correlated with multiple light/dark ratios of visual performance in central vision. These results provide a link between neuronal physiology and human vision while emphasizing the importance of stimulus polarity in measurements of visual fields and contrast sensitivity.

Effect of fasting on short-term visual plasticity in adult humans.

Brain plasticity and function is impaired in conditions of metabolic dysregulation, such as obesity. Less is known on whether brain function is also affected by transient and physiological metabolic changes, such as the alternation between fasting and fed state. Here we asked whether these changes affect the transient shift of ocular dominance that follows short-term monocular deprivation, a form of homeostatic plasticity. We further asked whether variations in three of the main metabolic and hormonal pathways affected in obesity (glucose metabolism, leptin signalling and fatty acid metabolism) correlate with plasticity changes. We measured the effects of 2 h monocular deprivation in three conditions: post-absorptive state (fasting), after ingestion of a standardised meal and during infusion of glucagon-like peptide-1 (GLP-1), an incretin physiologically released upon meal ingestion that plays a key role in glucose metabolism. We found that short-term plasticity was less manifest in fasting than in fed state, whereas GLP-1 infusion did not elicit reliable changes compared to fasting. Although we confirmed a positive association between plasticity and supraphysiological GLP-1 levels, achieved by GLP-1 infusion, we found that none of the parameters linked to glucose metabolism could predict the plasticity reduction in the fasting versus fed state. Instead, this was selectively associated with the increase in plasma beta-hydroxybutyrate (B-OH) levels during fasting, which suggests a link between neural function and energy substrates alternative to glucose. These results reveal a previously unexplored link between homeostatic brain plasticity and the physiological changes associated with the daily fast-fed cycle.

Macroalgae Abundance And Cover As Ecological Indicators Of Coral Reef Management In The Waters Of Katapang Village, West Seram Regency, Maluku Province

Macroalgae are the main competitors for coral reefs in fighting for aquatic ecological space in coral reef ecosystems. The purpose of this research; Knowing the condition of the aquatic environment, the abundance and cover of macroalgae, and the potential of macroalgae for indicators of coral reef management in the coastal waters of Katapang Village. Data on the physical condition of the waters were measured in situ while macroalgae data for each research station were obtained using the LIT (Line Intercept Transect Method). Macroalgae taxa were identified using an identification guide book from FAO (1998). The distribution of each type of macroalgae was mapped spatially based on the distribution conditions of the macroalgae at each study station. The results showed that the condition of the waters of the coral reef ecosystem in Katapang Village was supportive for the growth of macroalgae. The macroalgae found came from 3 orders, 4 families, 5 genera and 8 species. The results also indicate that the abundance and cover of macroalgae determines the shift in dominance in reef ecosystems so that these two factors can be used as indicators of coral reef management.