Three heads are better than one: cooperative learning brains wire together when a consensus is reached.

Theories of human learning converge on the view that individuals working together learn better than do those working independently. Little is known, however, about the neural mechanisms of learning through cooperation. We addressed this research gap by leveraging functional near-infrared spectroscopy to record the brain activity of triad members in a group simultaneously. Triads were instructed to analyze an ancient Chinese poem either cooperatively or independently. Four main findings emerged. First, we observed significant within-group neural synchronization (GNS) in the left superior temporal cortex, supramarginal gyrus, and postcentral gyrus during cooperative learning compared with independent learning. Second, the enhancement of GNS in triads was amplified when a consensus was reached (vs. elaboration or argument) during cooperative learning. Third, GNS was predictive of learning outcome at an early stage (156-170 s after learning was initiated). Fourth, social factors such as social closeness (e.g. how much learners liked one other) were reflected in GNS and co-varied with learning engagement. These results provide neuroscientific support for Piaget's theory of cognitive development and favor the notion that successful learning through cooperation involves dynamic consensus-building, which is captured in neural patterns shared across learners in a group.

Improving the Output Efficiency of Triboelectric Nanogenerator by a Power Regulation Circuit.

Triboelectric nanogenerator (TENG) is a promising technology for harvesting energy from various sources, such as human motion, wind and vibration. At the same time, a matching backend management circuit is essential to improve the energy utilization efficiency of TENG. Therefore, this work proposes a power regulation circuit (PRC) suitable for TENG, which is composed of a valley-filling circuit and a switching step-down circuit. The experimental results indicate that after incorporating a PRC, the conduction time of each cycle of the rectifier circuit doubles, increasing the number of current pulses in the TENG output and resulting in an output charge that is 1.6 fold that of the original circuit. Compared with the initial output signal, the charging rate of the output capacitor increased significantly by 75% with a PRC at a rotational speed of 120 rpm, significantly improving the utilization efficiency of the TENG's output energy. At the same time, when the TENG powers LEDs, the flickering frequency of LEDs is reduced after adding a PRC, and the light emission is more stable, which further verifies the test results. The PRC proposed in this study can enable the energy harvested by the TENG to be utilized more efficiently, which has a certain promoting effect on the development and application of TENG technology.

Interpersonal coordination enhances brain-to-brain synchronization and influences responsibility attribution and reward allocation in social cooperation.

Fair distribution of resources matters to both individual interests and group harmony during social cooperation. Different allocation rules, including equity- and equality-based rules, have been widely discussed in reward allocation research; however, it remains unclear whether and how individuals' cooperative manner, such as interpersonal coordination, influence their subsequent responsibility attribution and reward allocation. Here, 46 dyads conducted a time estimation task-either synergistically (the coordination group) or solely (the control group)-while their brain activities were measured using a functional near-infrared spectroscopy hyperscanning approach. Dyads in the coordination group showed higher behavioral synchrony and higher interpersonal brain synchronization (IBS) in the dorsal lateral prefrontal cortex (DLPFC) during the time estimation task than those in the control group. They also showed a more egalitarian tendency of responsibility attribution for the task outcome. More importantly, dyads in the coordination group who had higher IBS in the dorsal medial prefrontal cortex (DMPFC) were more inclined to make egalitarian reward allocations, and this effect was mediated by responsibility attribution. Our findings elucidate the influence of interpersonal coordination on reward allocation and the critical role of the prefrontal cortex in these processes.

Integration of social status and trust through interpersonal brain synchronization.

Trust can be a dynamic social process, during which the social identity of the interacting agents (e.g., an investor and a trustee) can bias trust outcomes. Here, we investigated how social status modulates trust and the neural mechanisms underlying this process. An investor and a trustee performed a 10-round repeated trust game while their brain activity was being simultaneously recorded using functional near-infrared spectroscopy. The social status (either high or low) of both investors and trustees was manipulated via a math competition task. The behavioral results showed that in the initial round, individuals invested more in low-status partners. However, the investment ratio increased faster as the number of rounds increased during trust interaction when individuals were paired with a high-status partner. This increasing trend was particularly prominent in the low (investor)-high (trustee) status group. Moreover, the low-high group showed increased investor-trustee brain synchronization in the right temporoparietal junction as the number of rounds increased, while brain activation in the right dorsolateral prefrontal cortex of the investor decreased as the number of rounds increased. Both interpersonal brain synchronization and brain activation predicted investment performance at the early stage; furthermore, two-brain data provided earlier predictions than did single-brain data. These effects were detectable in the investment phase in the low-high group only; no comparable effects were observed in the repayment phase or other groups. Overall, this study demonstrated a multi-brain mechanism for the integration of social status and trust.

Factors associated with blood lead levels in children in Shenyang, China: a cross-sectional study.

BACKGROUND: Although blood lead levels (BLLs) in children are gradually decreasing, low-concentration lead exposure can still exert adverse effects. We studied the factors that affect BLLs in children in Shenyang, China. METHODS: We conducted a cross-sectional study by administering structured questionnaires on family demographics and food intake. The concentrations of lead in venous blood were determined by graphite furnace atomic absorption spectrometry. RESULTS: A total of 273 children aged 1-6 years were enrolled. The geometric mean (geometric standard deviation) of BLLs was 24.94 (12.70) µg/L in boys and 23.75 (11.34) µg/L in girls. The prevalence of BLLs of ≥35 µg/L was 22.7% and was mainly observed in children aged under 3 years. Often hand washing before meals was protective against BLLs ≥20 µg/L (adjusted OR: 0.427, 95%CI: 0.238-0.767, p = 0.004). Consumption of puffed grains and eggs had an adjusted OR (95%CI) for BLLs ≥20 µg/L of 1.714 (1.012-2.901) (p = 0.045) and 1.787 (1.000-3.192) (p = 0.050), respectively. CONCLUSIONS: BLLs of children in Shenyang are still higher than in developed countries. Consumption of puffed grains and eggs is associated with higher BLLs. Often hand washing before meals may be protective against high BLLs.

Functional divergence of two duplicated Fertilization Independent Endosperm genes in rice with respect to seed development.

Fertilization Independent Endosperm (FIE) is an essential member of Polycomb Repressive Complex 2 (PRC2) that plays important roles in the developmental regulation of plants. OsFIE1 and OsFIE2 are two FIE homologs in the rice genome. Here, we showed that OsFIE1 probably duplicated from OsFIE2 after the origin of the tribe Oryzeae, but has a specific expression pattern and methylation landscape. During evolution, OsFIE1 underwent a less intensive purifying selection than did OsFIE2. The mutant osfie1 produced smaller seeds and displayed reduced dormancy, indicating that OsFIE1 predominantly functions in late seed development. Ectopic expression of OsFIE1, but not OsFIE2, was deleterious to vegetative growth in a dose-dependent manner. The newly evolved N-terminal tail of OsFIE1 was probably not the cause of the adverse effects on vegetative growth. The CRISPR/Cas9-derived mutant osfie2 exhibited impaired cellularization of the endosperm, which suggested that OsFIE2 is indispensable for early seed development as a positive regulator of cellularization. Autonomous endosperm was observed in both OsFIE2+- and osfie1/OsFIE2+- but at a very low frequency. Although OsFIE1-PRC2 exhibited H3K27me3 methyltransferase ability in plants, OsFIE1-PRC2 is likely to be less important for development in rice than is OsFIE2-PRC2. Our findings revealed the functional divergence of OsFIE1 and OsFIE2 and shed light on their distinct evolution following duplication.

Various Novel Colistin Resistance Mechanisms Interact To Facilitate Adaptation of Aeromonas hydrophila to Complex Colistin Environments.

Aeromonas hydrophila, a heterotrophic and Gram-negative bacterium, has attracted considerable attention owing to the increasing prevalence of reported infections. Colistin is a last-resort antibiotic that can treat life-threatening infections caused by multidrug-resistant Gram-negative bacteria. However, the mechanisms underlying colistin resistance in A. hydrophila remain unclear. The present study reveals four novel colistin resistance mechanisms in A. hydrophila: (i) EnvZ/OmpR upregulates the expression of the arnBCADTEF operon to mediate lipopolysaccharide (LPS) modification by 4-amino-4-deoxy-l-arabinose, (ii) EnvZ/OmpR regulates the expression of the autotransporter gene3832 to decrease outer membrane permeability in response to colistin, (iii) deletion of envZ/ompR activates PhoP/PhoQ, which functions as a substitute two-component system to mediate the addition of phosphoethanolamine to lipid A via pmrC, and (iv) the mlaFD173A mutant confers high-level colistin resistance via upregulation of the Mla pathway. The EnvZ/OmpR two-component system-mediated resistance mechanism is the leading form of colistin resistance in A. hydrophila, which enables it to rapidly generate low- to medium-level colistin resistance. As colistin concentrations in the environment continue to rise, antibiotic resistance mediated by EnvZ/OmpR becomes insufficient to ensure bacterial survival. Consequently, A. hydrophila has developed an mlaF mutation that results in high-level colistin resistance. Our findings indicate that A. hydrophila can thrive in a complex environment through various colistin resistance mechanisms.

Mathematical synthesis of the cortical circulation for the whole mouse brain-part II: Microcirculatory closure.

Recent advancements in multiphoton imaging and vascular reconstruction algorithms have increased the amount of data on cerebrovascular circulation for statistical analysis and hemodynamic simulations. Experimental observations offer fundamental insights into capillary network topology but mainly within a narrow field of view typically spanning a small fraction of the cortical surface (less than 2%). In contrast, larger-resolution imaging modalities, such as computed tomography (CT) or magnetic resonance imaging (MRI), have whole-brain coverage but capture only larger blood vessels, overlooking the microscopic capillary bed. To integrate data acquired at multiple length scales with different neuroimaging modalities and to reconcile brain-wide macroscale information with microscale multiphoton data, we developed a method for synthesizing hemodynamically equivalent vascular networks for the entire cerebral circulation. This computational approach is intended to aid in the quantification of patterns of cerebral blood flow and metabolism for the entire brain. In part I, we described the mathematical framework for image-guided generation of synthetic vascular networks covering the large cerebral arteries from the circle of Willis through the pial surface network leading back to the venous sinuses. Here in part II, we introduce novel procedures for creating microcirculatory closure that mimics a realistic capillary bed. We demonstrate our capability to synthesize synthetic vascular networks whose morphometrics match empirical network graphs from three independent state-of-the-art imaging laboratories using different image acquisition and reconstruction protocols. We also successfully synthesized twelve vascular networks of a complete mouse brain hemisphere suitable for performing whole-brain blood flow simulations. Synthetic arterial and venous networks with microvascular closure allow whole-brain hemodynamic predictions. Simulations across all length scales will potentially illuminate organ-wide supply and metabolic functions that are inaccessible to models reconstructed from image data with limited spatial coverage.

Choosing an optimal wavelength to detect brain activity in functional near-infrared spectroscopy.

Functional near-infrared spectroscopy (fNIRS) measures human brain function noninvasively. The optical response to oxy- and deoxy-hemoglobin concentration variations during brain activation is wavelength dependent because of the differing spectral shapes of the extinction coefficients of the two hemoglobin species. Choosing the optimal wavelength in fNIRS measurements is crucial to improving the performance of the technique. Here we report on a framework to estimate the spectral response to neural activation in a pre-defined local region. We found that the wavelength that exhibits the largest fractional change in the detected fluence with respect to the baseline value is around 830 nm.

Imaging localized fast optical signals of neural activation with optical coherence tomography in awake mice.

We report optical coherence tomography (OCT) imaging of localized fast optical signals (FOSs) arising from whisker stimulation in awake mice. The activated voxels were identified by fitting the OCT intensity signal time course with a response function over a time scale of a few hundred milliseconds after the whisker stimulation. The significantly activated voxels were shown to be localized to the expected brain region for whisker stimulation. The ability to detect functional stimulus-evoked, depth-resolved FOS with intrinsic contrast from the cortex provides a new tool for neural activity studies.

Comparing the fundamental imaging depth limit of two-photon, three-photon, and non-degenerate two-photon microscopy.

We have systematically characterized the degradation of imaging quality with depth in deep brain multi-photon microscopy, utilizing our recently developed numerical model that computes wave propagation in scattering media. The signal-to-background ratio (SBR) and the resolution determined by the width of the point spread function are obtained as functions of depth. We compare the imaging quality of two-photon (2PM), three-photon (3PM), and non-degenerate two-photon microscopy (ND-2PM) for mouse brain imaging. We show that the imaging depth of 2PM and ND-2PM are fundamentally limited by the SBR, while the SBR remains approximately invariant with imaging depth for 3PM. Instead, the imaging depth of 3PM is limited by the degradation of the resolution, if there is sufficient laser power to maintain the signal level at large depth. The roles of the concentration of dye molecules, the numerical aperture of the input light, the anisotropy factor g, noise level, input laser power, and the effect of temporal broadening are also discussed.

Dependence of the MR signal on the magnetic susceptibility of blood studied with models based on real microvascular networks.

PURPOSE: The primary goal of this study was to estimate the value of ß , the exponent in the power law relating changes of the transverse relaxation rate and intra-extravascular local magnetic susceptibility differences as ΔR2∗∝(Δχ)ß . The secondary objective was to evaluate any differences that might exist in the value of ß obtained using a deoxyhemoglobin-weighted Δχ distribution versus a constant Δχ distribution assumed in earlier computations. The third objective was to estimate the value of ß that is relevant for methods based on susceptibility contrast agents with a concentration of Δχ higher than that used for BOLD fMRI calculations. METHODS: Our recently developed model of real microvascular anatomical networks is used to extend the original simplified Monte-Carlo simulations to compute ß from the first principles. RESULTS: Our results show that ß=1 for most BOLD fMRI measurements of real vascular networks, as opposed to earlier predictions of ß=1 .5 using uniform Δχ distributions. For perfusion or fMRI methods based on contrast agents, which generate larger values for Δχ , ß=1 for B0≤ 9.4 T, whereas at 14 T ß can drop below 1 and the variation across subjects is large, indicating that a lower concentration of contrast agent with a lower value of Δχ is desired for experiments at high B0 . CONCLUSION: These results improve our understanding of the relationship between R2* and the underlying microvascular properties. The findings will help to infer the cerebral metabolic rate of oxygen and cerebral blood volume from BOLD and perfusion MRI, respectively.

Development of a beam propagation method to simulate the point spread function degradation in scattering media.

Scattering is one of the main issues that limit the imaging depth in deep tissue optical imaging. To characterize the role of scattering, we have developed a forward model based on the beam propagation method and established the link between the macroscopic optical properties of the media and the statistical parameters of the phase masks applied to the wavefront. Using this model, we have analyzed the degradation of the point-spread function of the illumination beam in the transition regime from ballistic to diffusive light transport. Our method provides a wave-optic simulation toolkit to analyze the effects of scattering on image quality degradation in scanning microscopy. Our open-source implementation is available at https://github.com/BUNPC/Beam-Propagation-Method.

Time domain diffuse correlation spectroscopy: modeling the effects of laser coherence length and instrument response function.

Diffuse correlation spectroscopy (DCS) is an optical technique that non-invasively quantifies an index of blood flow (BFi) by measuring the temporal autocorrelation function of the intensity fluctuations of light diffusely remitted from the tissue. Traditional DCS measurements use continuous wave (CW) lasers with coherence lengths longer than the photon path lengths in the sample to ensure that the diffusely remitted light is coherent and generates a speckle pattern. Recently, we proposed time domain DCS (TD-DCS) to allow measurements of the speckle fluctuations for specific path lengths of light through the tissue, which has the distinct advantage of permitting an analysis of selected long path lengths of light to improve the depth sensitivity of the measurement. However, compared to CW-DCS, factors including the instrument response function (IRF), the detection gate width, and the finite coherence length need to be considered in the model analysis of the experimental data. Here we present a TD-DCS model describing how the intensity autocorrelation functions measured for different path lengths of light depend on the coherence length, pulse width of the laser, detection gate width, IRF, BFi, and optical properties of the scattering sample. Predictions of the model are compared with experimental results using a homogeneous liquid phantom sample that mimics human tissue optical properties. The BFis obtained from the TD-DCS model for different path lengths of light agree with the BFi obtained from CW-DCS measurements, while the standard simplified model underestimates the BFi by a factor of ∼2. This Letter establishes the theoretical foundation of the TD-DCS technique and provides guidance for future BFi measurements in tissue.

Comparison of Different Feature Sets for TLS Point Cloud Classification.

Point cloud classification is an essential requirement for effectively utilizing point cloud data acquired by Terrestrial laser scanning (TLS). Neighborhood selection, feature selection and extraction, and classification of points based on the respective features constitute the commonly used workflow of point cloud classification. Feature selection and extraction has been the focus of many studies, and the choice of different features has had a great impact on classification results. In previous studies, geometric features were widely used for TLS point cloud classification, and only a few studies investigated the potential of both intensity and color on classification using TLS point cloud. In this paper, the geometric features, color features, and intensity features were extracted based on a supervoxel neighborhood. In addition, the original intensity was also corrected for range effect, which is why the corrected intensity features were also extracted. The different combinations of these features were tested on four real-world data sets. Experimental results demonstrate that both color and intensity features can complement the geometric features to help improve the classification results. Furthermore, the combination of geometric features, color features, and corrected intensity features together achieves the highest accuracy in our test.

Cooperation in lovers: An fNIRS-based hyperscanning study.

This study investigated interactive exchange in lovers and the associated interpersonal brain synchronization (IBS) using functional near-infrared spectroscopy (fNIRS)-based hyperscanning. Three types of female-male dyads, lovers, friends, and strangers, performed a cooperation task during which brain activity was recorded in right frontoparietal regions. We measured better cooperative behavior in lover dyads compared with friend and stranger dyads. Lover dyads demonstrated increased IBS in right superior frontal cortex, which also covaried with their task performance. Granger causality analyses in lover dyads revealed stronger directional synchronization from females to males than from males to females, suggesting different roles for females and males during cooperation. Our study refines the theoretical explanation of romantic interaction between lovers. Hum Brain Mapp 38:831-841, 2017. © 2016 Wiley Periodicals, Inc.

Robust reconfigurable electromagnetic pathways within a photonic topological insulator.

The discovery of topological photonic states has revolutionized our understanding of electromagnetic propagation and scattering. Endowed with topological robustness, photonic edge modes are not reflected from structural imperfections and disordered regions. Here we demonstrate robust propagation along reconfigurable pathways defined by synthetic gauge fields within a topological photonic metacrystal. The flow of microwave radiation in helical edge modes following arbitrary contours of the synthetic gauge field between bianisotropic metacrystal domains is unimpeded. This is demonstrated in measurements of the spectrum of transmission and time delay along the topological domain walls. These results provide a framework for freely steering electromagnetic radiation within photonic structures.

Memory skills mediating superior memory in a world-class memorist.

Laboratory studies have investigated how individuals with normal memory spans attained digit spans over 80 digits after hundreds of hours of practice. Experimental analyses of their memory skills suggested that their attained memory spans were constrained by the encoding time, for the time needed will increase if the length of digit sequences to be memorised becomes longer. These constraints seemed to be violated by a world-class memorist, Feng Wang (FW), who won the World Memory Championship by recalling 300 digits presented at 1 digit/s. In several studies we examined FW's memory skills underlying his exceptional performance. First FW reproduced his superior memory span of 200 digits under laboratory condition, and we obtained his retrospective reports describing his encoding/retrieval processes (Experiment 1). Further experiments used self-paced memorisation to identify temporal characteristics of encoding of digits in 4-digit clusters (Experiment 2), and explored memory encoding at presentation speeds much faster than 1 digit/s (Experiment 3). FW's superiority over previous digit span experts is explained by his acquisition of well-known mnemonic techniques and his training that focused on rapid memorisation. His memory performance supports the feasibility of acquiring memory skills for improved working memory based on storage in long-term memory.

Modeling hemispherical reflectance for natural surfaces based on terrestrial laser scanning backscattered intensity data.

Independent of instrumental properties and scanning geometry, target reflectance is significantly important for terrestrial laser scanning (TLS) data processing and utilization, especially in multi-temporal and multi-sensor cases. In addition to the 3D topographic coordinates, TLS systems also record the backscattered intensity value of each point that provides additional information on the reflectance characteristics of the scanned surface. However, a number of confounding variables, particularly the distance and incidence angle, distort the ability of the original intensity to directly retrieve the target reflectance. This study proposes a new method to model the hemispherical reflectance of natural surfaces from the TLS intensity data by eliminating the effects of incidence angle and distance. The incidence angle effect is corrected by the Oren-Nayar reflectance model which takes individual surface roughness into account whereas the irregular distance effect is eliminated by reference targets without estimating the specific distance-intensity function. The Faro Focus3D 120 terrestrial scanner is utilized in the case study. Six typical natural surfaces are chosen as the experimental objects. Results imply that the proposed method exhibits high accuracy in retrieving reflectance values. The deviation of the retrieved reflectance values from that measured by a spectrometer is approximately 4.29% and the root mean square error (RMSE) is approximately 0.0562.

Surface reflectance retrieval from the intensity data of a terrestrial laser scanner.

The intensity data recorded by terrestrial laser scanning systems are considered significant measures of the spectral property of scanned objects. These data can be used in an extensive range of object-based applications. However, the direct retrieval of reflectance from intensity information is infeasible because intensity data are influenced by multiple variables, particularly distance and incidence angle. This study proposes a new method to recover the absolute reflectance value of the scanned surface by eliminating the effects of distance and incidence angle. The Faro Focus3D 120 terrestrial scanner is utilized in the case study. Two sets of experiments are designed to estimate the parameters of the developed model by using Lambertian targets at different reflectance values. With the estimated parameters, the proposed method is applied to recover the reflectance values of natural surfaces. The deviation of the retrieved reflectance values of natural surfaces from the reflectance values measured by a spectrometer is approximately 2.64%. Results show that the proposed method exhibits high accuracy in retrieving reflectance values and can be utilized for actual mapping tasks and geological applications.