Floral-promoting GmFT homologs trigger photoperiodic after-effects: An important mechanism for early-maturing soybean varieties to regulate reproductive development and adapt to high latitudes.

Soybean (Glycine max) is a typical short-day plant, but has been widely cultivated in high-latitude long-day (LD) regions because of the development of early-maturing genotypes which are photoperiod-insensitive. However, some early-maturing varieties exhibit significant responses to maturity under different daylengths but not for flowering, depicting an evident photoperiodic after-effect, a poorly understood mechanism. In this study, we investigated the postflowering responses of 11 early-maturing soybean varieties to various preflowering photoperiodic treatments. We confirmed that preflowering SD conditions greatly promoted maturity and other postflowering developmental stages. Soybean homologs of FLOWERING LOCUS T (FT), including GmFT2a, GmFT3a, GmFT3b and GmFT5a, were highly accumulated in leaves under preflowering SD treatment. More importantly, they maintained a high expression level after flowering even under LD conditions. E1 RNAi and GmFT2a overexpression lines showed extremely early maturity regardless of preflowering SD and LD treatments due to constitutively high levels of floral-promoting GmFT homolog expression throughout their life cycle. Collectively, our data indicate that high and stable expression of floral-promoting GmFT homologs play key roles in the maintenance of photoperiodic induction to promote postflowering reproductive development, which confers early-maturing varieties with appropriate vegetative growth and shortened reproductive growth periods for adaptation to high latitudes.

The FLOWERING LOCUS T 5b positively regulates photoperiodic flowering and improves the geographical adaptation of soybean.

Plants can sense the photoperiod to flower at the right time. As a sensitive short-day crop, soybean (Glycine max) flowering varies greatly depending on photoperiods, affecting yields. Adaptive changes in soybeans rely on variable genetic loci such as E1 and FLOWERING LOCUS T orthologs. However, the precise coordination and control of these molecular components remain largely unknown. In this study, we demonstrate that GmFT5b functions as a crucial factor for soybean flowering. Overexpressed or mutated GmFT5b resulted in significantly early or later flowering, altering expression profiles for several downstream flowering-related genes under a long-day photoperiod. GmFT5b interacts with the transcription factor GmFDL15, suggesting transcriptional tuning of flowering time regulatory genes via the GmFT5b/GmFDL15 complex. Notably, GmFT5a partially compensated for GmFT5b function, as ft5a ft5b double mutants exhibited an enhanced late-flowering phenotype. Association mapping revealed that GmFT5b was associated with flowering time, maturity, and geographical distribution of soybean accessions, all associated with the E1 locus. Therefore, GmFT5b is a valuable target for enhancing regional adaptability. Natural variants or multiple mutants in this region can be utilized to generate optimized soybean varieties with precise flowering times.

Abnormal interlimb coordination of motor developmental delay during infant crawling based on kinematic synergy analysis.

BACKGROUND: Previous studies have reported that abnormal interlimb coordination is a typical characteristic of motor developmental delay (MDD) during human movement, which can be visually manifested as abnormal motor postures. Clinically, the scale assessments are usually used to evaluate interlimb coordination, but they rely heavily on the subjective judgements of therapists and lack quantitative analysis. In addition, although abnormal interlimb coordination of MDD have been studied, it is still unclear how this abnormality is manifested in physiology-related kinematic features. OBJECTIVES: This study aimed to evaluate how abnormal interlimb coordination of MDD during infant crawling was manifested in the stability of joints and limbs, activation levels of synergies and intrasubject consistency from the kinematic synergies of tangential velocities of joints perspective. METHODS: Tangential velocities of bilateral shoulder, elbow, wrist, hip, knee and ankle over time were computed from recorded three-dimensional joint trajectories in 40 infants with MDD [16 infants at risk of developmental delay, 11 infants at high risk of developmental delay, 13 infants with confirmed developmental delay (CDD group)] and 20 typically developing infants during hands-and-knees crawling. Kinematic synergies and corresponding activation coefficients were derived from those joint velocities using the non-negative matrix factorization algorithm. The variability accounted for yielded by those synergies and activation coefficients, and the synergy weightings in those synergies were used to measure the stability of joints and limbs. To quantify the activation levels of those synergies, the full width at half maximum and center of activity of activation coefficients were calculated. In addition, the intrasubject consistency was measured by the cosine similarity of those synergies and activation coefficients. RESULTS: Interlimb coordination patterns during infant crawling were the combinations of four types of single-limb movements, which represent the dominance of each of the four limbs. MDD mainly reduced the stability of joints and limbs, and induced the abnormal activation levels of those synergies. Meanwhile, MDD generally reduced the intrasubject consistency, especially in CDD group. CONCLUSIONS: These features have the potential for quantitatively evaluating abnormal interlimb coordination in assisting the clinical diagnosis and motor rehabilitation of MDD.

GmNF-YC4 delays soybean flowering and maturation by directly repressing GmFT2a and GmFT5a expression.

Flowering time and growth period are key agronomic traits which directly affect soybean (Glycine max (L.) Merr.) adaptation to diverse latitudes and farming systems. The FLOWERING LOCUS T (FT) homologs GmFT2a and GmFT5a integrate multiple flowering regulation pathways and significantly advance flowering and maturity in soybean. Pinpointing the genes responsible for regulating GmFT2a and GmFT5a will improve our understanding of the molecular mechanisms governing growth period in soybean. In this study, we identified the Nuclear Factor Y-C (NFY-C) protein GmNF-YC4 as a novel flowering suppressor in soybean under long-day (LD) conditions. GmNF-YC4 delays flowering and maturation by directly repressing the expression of GmFT2a and GmFT5a. In addition, we found that a strong selective sweep event occurred in the chromosomal region harboring the GmNF-YC4 gene during soybean domestication. The GmNF-YC4Hap3 allele was mainly found in wild soybean (Glycine soja Siebold & Zucc.) and has been eliminated from G. max landraces and improved cultivars, which predominantly contain the GmNF-YC4Hap1 allele. Furthermore, the Gmnf-yc4 mutants displayed notably accelerated flowering and maturation under LD conditions. These alleles may prove to be valuable genetic resources for enhancing soybean adaptability to higher latitudes.

Transcriptional profiling reveals a critical role of GmFT2a in soybean staygreen syndrome caused by the pest Riptortus pedestris.

Soybean staygreen syndrome, characterized by delayed leaf and stem senescence, abnormal pods, and aborted seeds, has recently become a serious and prominent problem in soybean production. Although the pest Riptortus pedestris has received increasing attention as the possible cause of staygreen syndrome, the mechanism remains unknown. Here, we clarify that direct feeding by R. pedestris, not transmission of a pathogen by this pest, is the primary cause of typical soybean staygreen syndrome and that critical feeding damage occurs at the early pod stage. Transcriptome profiling of soybean indicated that many signal transduction pathways, including photoperiod, hormone, defense response, and photosynthesis, respond to R. pedestris infestation. Importantly, we discovered that members of the FLOWERING LOCUS T (FT) gene family were suppressed by R. pedestris infestation, and overexpression of floral inducer GmFT2a attenuates staygreen symptoms by mediating soybean defense response and photosynthesis. Together, our findings systematically illustrate the association between pest infestation and soybean staygreen syndrome and provide the basis for establishing a targeted soybean pest prevention and control system.

Molecular breeding for improvement of photothermal adaptability in soybean.

Soybean (Glycine max (L.) Merr.) is a typical short-day and temperate crop that is sensitive to photoperiod and temperature. Responses of soybean to photothermal conditions determine plant growth and development, which affect its architecture, yield formation, and capacity for geographic adaptation. Flowering time, maturity, and other traits associated with photothermal adaptability are controlled by multiple major-effect and minor-effect genes and genotype-by-environment interactions. Genetic studies have identified at least 11 loci (E1-E4, E6-E11, and J) that participate in photoperiodic regulation of flowering time and maturity in soybean. Molecular cloning and characterization of major-effect flowering genes have clarified the photoperiod-dependent flowering pathway, in which the photoreceptor gene phytochrome A, circadian evening complex (EC) components, central flowering repressor E1, and FLOWERING LOCUS T family genes play key roles in regulation of flowering time, maturity, and adaptability to photothermal conditions. Here, we provide an overview of recent progress in genetic and molecular analysis of traits associated with photothermal adaptability, summarizing advances in molecular breeding practices and tools for improving these traits. Furthermore, we discuss methods for breeding soybean varieties with better adaptability to specific ecological regions, with emphasis on a novel strategy, the Potalaization model, which allows breeding of widely adapted soybean varieties through the use of multiple molecular tools in existing elite widely adapted varieties. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01406-z.

QTL analyses of soybean root system architecture revealed genetic relationships with shoot-related traits.

KEY MESSAGE: The genetic basis of soybean root system architecture (RSA) and the genetic relationship between shoot and RSA were revealed by integrating data from recombinant inbred population grafting and QTL mapping. Variations in root system architecture (RSA) affect the functions of roots and thus play vital roles in plant adaptations and agricultural productivity. The aim of this study was to unravel the genetic relationship between RSA traits and shoot-related traits in soybean. This study characterized RSA variability at seedling stage in a recombinant inbred population, derived from a cross between cultivated soybean C08 and wild soybean W05, and performed high-resolution quantitative trait locus (QTL) mapping. In total, 34 and 41 QTLs were detected for RSA-related and shoot-related traits, respectively, constituting eight QTL clusters. Significant QTL correspondence was found between shoot biomass and RSA-related traits, consistent with significant correlations between these phenotypes. RSA-related QTLs also overlapped with selection regions in the genome, suggesting the cultivar RSA could be a partial consequence of domestication. Using reciprocal grafting, we confirmed that shoot-derived signals affected root development and the effects were controlled by multiple loci. Meanwhile, RSA-related QTLs were found to co-localize with four soybean flowering-time loci. Consistent with the phenotypes of the parental lines of our RI population, diminishing the function of flowering controlling E1 family through RNA interference (RNAi) led to reduced root growth. This implies that the flowering time-related genes within the RSA-related QTLs are actually contributing to RSA. To conclude, this study identified the QTLs that determine RSA through controlling root growth indirectly via regulating shoot functions, and discovered superior alleles from wild soybean that could be used to improve the root structure in existing soybean cultivars.

Using Staphylococcus aureus Cas9 to Expand the Scope of Potential Gene Targets for Genome Editing in Soybean.

The CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) is a revolutionary genome editing technology that has been used to achieve site-specific gene knock-out, large fragment deletion, or base editing in many plant species including soybean (Glycinemax). The Streptococcuspyogenes Cas9 (SpCas9) is widely used in plants at present, although there are some reports describing the application of CRISPR/Cpf1 in soybean. Therefore, the selection range of PAM (protospacer adjacent motif) sequences for soybean is currently limited to 5'-NGG-3' (SpCas9) or 5'-TTTN-3' (Cpf1), which in turn limits the number of genes that can be mutated. Another Cas9 enzyme from Staphylococcus aureus (SaCas9) recognizes the PAM sequence 5'-NNGRRT-3' (where R represents A or G), which can provide a wider range of potential target sequences. In this study, we developed a CRISPR/SaCas9 system and used this tool to specifically induce targeted mutations at five target sites in the GmFT2a (Glyma.16G150700) and GmFT5a (Glyma.16G044100) genes in soybean hairy roots. We demonstrated that this tool can recognize the PAM sequences 5'-AAGGGT-3', 5'-GGGGAT-3', 5'-TTGAAT-3', and 5'-TAGGGT-3' in soybean, and it achieved mutation rates ranging from 34.5% to 73.3%. Our results show that we have established a highly efficient CRISPR/SaCas9 tool that is as suitable as SpCas9 for genome editing in soybean, and it will be useful for expanding the range of target sequences for genome editing.

Functional Redundancy of FLOWERING LOCUS T 3b in Soybean Flowering Time Regulation.

Photoperiodic flowering is an important agronomic trait that determines adaptability and yield in soybean and is strongly influenced by FLOWERING LOCUS T (FT) genes. Due to the presence of multiple FT homologs in the genome, their functions in soybean are not fully understood. Here, we show that GmFT3b exhibits functional redundancy in regulating soybean photoperiodic flowering. Bioinformatic analysis revealed that GmFT3b is a typical floral inducer FT homolog and that the protein is localized to the nucleus. Moreover, GmFT3b expression was induced by photoperiod and circadian rhythm and was more responsive to long-day (LD) conditions. We generated a homozygous ft3b knockout and three GmFT3b-overexpressing soybean lines for evaluation under different photoperiods. There were no significant differences in flowering time between the wild-type, the GmFT3b overexpressors, and the ft3b knockouts under natural long-day, short-day, or LD conditions. Although the downstream flowering-related genes GmFUL1 (a, b), GmAP1d, and GmLFY1 were slightly down-regulated in ft3b plants, the floral inducers GmFT5a and GmFT5b were highly expressed, indicating potential compensation for the loss of GmFT3b. We suggest that GmFT3b acts redundantly in flowering time regulation and may be compensated by other FT homologs in soybean.

Genomic Dissection and Diurnal Expression Analysis Reveal the Essential Roles of the PRR Gene Family in Geographical Adaptation of Soybean.

Pseudo-response regulator (PRR) family members serve as key components of the core clock of the circadian clock, and play important roles in photoperiodic flowering, stress tolerance, growth, and the development of plants. In this study, 14 soybean PRR genes were identified, and classified into three groups according to phylogenetic analysis and structural characteristics. Real-time quantitative PCR analysis revealed that 13 GmPRRs exhibited obvious rhythmic expression under long-day (LD) and short-day (SD) conditions, and the expression of 12 GmPRRs was higher under LD in leaves. To evaluate the effects of natural variations in GmPRR alleles on soybean adaptation, we examined the sequences of GmPRRs among 207 varieties collected across China and the US, investigated the flowering phenotypes in six environments, and analyzed the geographical distributions of the major haplotypes. The results showed that a majority of non-synonymous mutations in the coding region were associated with flowering time, and we found that the nonsense mutations resulting in deletion of the CCT domain were related to early flowering. Haplotype analysis demonstrated that the haplotypes associated with early flowering were mostly distributed in Northeast China, while the haplotypes associated with late flowering were mostly cultivated in the lower latitudes of China. Our study of PRR family genes in soybean provides not only an important guide for characterizing the circadian clock-controlled flowering pathway but also a theoretical basis and opportunities to breed varieties with adaptation to specific regions and farming systems.

Cotyledons facilitate the adaptation of early-maturing soybean varieties to high-latitude long-day environments.

Soybean (Glycine max), a typical short-day plant (SDP) domesticated in temperate regions, has expanded to high latitudes where daylengths are long from soybean emergence to bloom, but rapidly decrease from seed filling to maturity. Cotyledons are well known as the major storage organs in seeds, but it is unclear whether developing cotyledons store flowering substances at filling stage in SD for upcoming seedlings, or instead respond to photoperiod for floral induction after emergence of matured seeds in long-day (LD). Here, we report that cotyledons accelerate flowering of early-maturing varieties not resulting from stored floral stimuli but by perceiving photoperiod after emergence. We found that light signal is indispensable to activate cotyledons for floral induction, and flowering promoting gene GmFT2a is required for cotyledon-dependent floral induction via upregulation of floral identity gene GmAP1. Interestingly, cotyledons are competent to support the entire life cycle of a cotyledon-only plant to produce seeds, underlying a new photoperiod study system in soybean and other dicots. Taken together, these results demonstrate a substantial role for cotyledons in flowering process, whereby we propose a 'cotyledon-based self-reliance' model highlighting floral induction from emergence as a key ecological adaptation for rapid flowering of SDPs grown in LD environments at high latitudes.

Enhancing Detection of SSMVEP Induced by Action Observation Stimuli Based on Task-Related Component Analysis.

Action observation (AO)-based brain-computer interface (BCI) is an important technology in stroke rehabilitation training. It has the advantage of simultaneously inducing steady-state motion visual evoked potential (SSMVEP) and activating sensorimotor rhythm. Moreover, SSMVEP could be utilized to perform classification. However, SSMVEP is composed of complex modulation frequencies. Traditional canonical correlation analysis (CCA) suffers from poor recognition performance in identifying those modulation frequencies at short stimulus duration. To address this issue, task-related component analysis (TRCA) was utilized to deal with SSMVEP for the first time. An interesting phenomenon was found: different modulated frequencies in SSMVEP distributed in different task-related components. On this basis, a multi-component TRCA method was proposed. All the significant task-related components were utilized to construct multiple spatial filters to enhance the detection of SSMVEP. Further, a combination of TRCA and CCA was proposed to utilize both advantages. Results showed that the accuracies using the proposed methods were significant higher than that using CCA at all window lengths and significantly higher than that using ensemble-TRCA at short window lengths (≤2 s). Therefore, the proposed methods further validate the induced modulation frequencies and will speed up the application of the AO-based BCI in rehabilitation.

Natural variation and CRISPR/Cas9-mediated mutation in GmPRR37 affect photoperiodic flowering and contribute to regional adaptation of soybean.

Flowering time is a critical determinant of the geographic distribution and regional adaptability of soybean (Glycine max) and is strongly regulated by photoperiod and temperature. In this study, quantitative trait locus (QTL) mapping and subsequent candidate gene analysis revealed that GmPRR37, encoding a pseudo-response regulator protein, is responsible for the major QTL qFT12-2, which was identified from a population of 308 recombinant inbred lines (RILs) derived from a cross between a very late-flowering soybean cultivar, 'Zigongdongdou (ZGDD)', and an extremely early-flowering cultivar, 'Heihe27 (HH27)', in multiple environments. Comparative analysis of parental sequencing data confirmed that HH27 contains a non-sense mutation that causes the loss of the CCT domain in the GmPRR37 protein. CRISPR/Cas9-induced Gmprr37-ZGDD mutants in soybean exhibited early flowering under natural long-day (NLD) conditions. Overexpression of GmPRR37 significantly delayed the flowering of transgenic soybean plants compared with wild-type under long photoperiod conditions. In addition, both the knockout and overexpression of GmPRR37 in soybean showed no significant phenotypic alterations in flowering time under short-day (SD) conditions. Furthermore, GmPRR37 down-regulated the expression of the flowering-promoting FT homologues GmFT2a and GmFT5a, and up-regulated flowering-inhibiting FT homologue GmFT1a expression under long-day (LD) conditions. We analysed haplotypes of GmPRR37 among 180 cultivars collected across China and found natural Gmprr37 mutants flower earlier and enable soybean to be cultivated at higher latitudes. This study demonstrates that GmPRR37 controls soybean photoperiodic flowering and provides opportunities to breed optimized cultivars with adaptation to specific regions and farming systems.

Mutagenesis of GmFT2a and GmFT5a mediated by CRISPR/Cas9 contributes for expanding the regional adaptability of soybean.

Flowering time is a key agronomic trait that directly influences the successful adaptation of soybean (Glycine max) to diverse latitudes and farming systems. GmFT2a and GmFT5a have been extensively identified as flowering activators and integrators in soybean. Here, we identified two quantitative trait loci (QTLs) regions harbouring GmFT2a and GmFT5a, respectively, associated with different genetic effects on flowering under different photoperiods. We analysed the flowering time of transgenic plants overexpressing GmFT2a or GmFT5a, ft2a mutants, ft5a mutants and ft2aft5a double mutants under long-day (LD) and short-day (SD) conditions. We confirmed that GmFT2a and GmFT5a are not redundant, they collectively regulate flowering time, and the effect of GmFT2a is more prominent than that of GmFT5a under SD conditions whereas GmFT5a has more significant effects than GmFT2a under LD conditions. GmFT5a, not GmFT2a, was essential for soybean to adapt to high latitude regions. The ft2aft5a double mutants showed late flowering by about 31.3 days under SD conditions and produced significantly increased numbers of pods and seeds per plant compared to the wild type. We speculate that these mutants may have enormous yield potential for the tropics. In addition, we examined the sequences of these two loci in 202 soybean accessions and investigated the flowering phenotypes, geographical distributions and maturity groups within major haplotypes. These results will contribute to soybean breeding and regional adaptability.

Soybean adaption to high-latitude regions is associated with natural variations of GmFT2b, an ortholog of FLOWERING LOCUS T.

Day length has an important influence on flowering and growth habit in many plant species. In crops such as soybean, photoperiod sensitivity determines the geographical range over which a given cultivar can grow and flower. The soybean genome contains ~10 genes homologous to FT, a central regulator of flowering from Arabidopsis thaliana. However, the precise roles of these soybean FTs are not clearly. Here we show that one such gene, GmFT2b, promotes flowering under long-days (LDs). Overexpression of GmFT2b upregulates expression of flowering-related genes which are important in regulating flowering time. We propose a 'weight' model for soybean flowering under short-day (SD) and LD conditions. Furthermore, we examine GmFT2b sequences in 195 soybean cultivars, as well as flowering phenotypes, geographical distributions and maturity groups. We found that Hap3, a major GmFT2b haplotype, is associated with significantly earlier flowering at higher latitudes. We anticipate our assay to provide important resources for the genetic improvement of soybean, including new germplasm for soybean breeding, and also increase our understanding of functional diversity in the soybean FT gene family.

Burst-modulated wide-pulse neuromuscular electrical stimulation enhances H-reflex recruitment in rats.

INTRODUCTION: In this study we investigated whether burst-modulated wide-pulse neuromuscular electrical stimulation (NMES) can improve the H-reflex and activation efficiency of sensory fibers. METHODS: NMES-induced electromyography (EMG) was recorded from hindpaw plantar muscles in 11 anesthetized rats. A burst-modulated wide pulse (mWP) with three carrier frequencies (2 kHz, 5 kHz, and 10 kHz) and a continuous wide-pulse (WP) were delivered to the tibial nerve of each rat. The evoked Hoffman (H)-reflexes were measured to evaluate nerve activation efficiency using the H-reflex recruitment curve (HRC). RESULTS: Relative to WP simulation, mWP stimulation required less electrical charge to excite sensory fibers and improved the H-reflex recruitment. Greater electrical charge and smaller recruitment gains were obtained with increased carrier frequency of mWP. DISCUSSION: mWP NMES can improve stimulation efficiency and improve recruitment of sensory fibers on tibial nerve stimulation, which may help to optimize NMES stimulus parameters.

Prolonged post-stimulation response induced by 980-nm infrared neural stimulation in the rat primary motor cortex.

The post-stimulation response of neural activities plays an important role to evaluate the effectiveness and safety of neural modulation techniques. Previous studies have established the capability of infrared neural modulation (INM) on neural firing regulation in the central nervous system (CNS); however, the dynamic neural activity after the laser offset has not been well characterized yet. We applied 980-nm infrared diode laser light to irradiate the primary motor cortex of rats, and tungsten electrode was inserted to record the single-unit activity of neurons at the depth of 800-1000 µm (layer V of primary motor cortex). The neural activities were assessed through the change of neural firing rate and firing pattern pre- and post-stimulation with various radiant exposures. The results showed that the 980-nm laser could modulate the firing properties of neurons in the deep layer of the cortex. More neurons with post-stimulation response (78% vs. 83%) were observed at higher stimulation intensity (0.803 J/cm2 vs. 1.071 J/cm2, respectively). The change of firing rate also increased with radiant exposures increasing, and the response lasted up to 4.5 s at 1.071 J/cm2, which was significantly longer than the theoretical thermal relaxation time. Moreover, the increasing Fano factors indicated the irregularity firing pattern of post-stimulation response. Our results confirmed that neural activity maintained a prolonged post-stimulation response after INM, which may provide necessary measurable data for optimization of INM applications in CNS.

After-effects of repetitive anodal transcranial direct current stimulation on learning and memory in a rat model of Alzheimer's disease.

Repetitive anodal transcranial direct current stimulation (tDCS) in a rat model of Alzheimer's disease (AD) has been shown to have distinct neuroprotective effects. Moreover, the effects of anodal tDCS not only occur during the stimulation but also persist after the stimulation has ended (after-effects). Here, the duration of the after-effects induced by repetitive anodal tDCS was investigated based on our previous studies. Adult male Sprague-Dawley rats were divided into three groups: a sham group, a ß-amyloid (Aß) group (AD group) and a stimulation group (ATD group). Aß was injected into the bilateral hippocampi of the rats in the AD and ATD groups to produce the AD model. Rats in the ATD group underwent 10 sessions of anodal tDCS, and the after-effects of repetitive anodal tDCS were evaluated by behavioral and histological analyses. A Morris water maze (MWM) was utilized on a monthly basis to assess spatial learning and memory abilities. The ATD group showed shorter escape latencies and more platform region crossings than the AD group. Hippocampal choline acetyltransferase (ChAT) and glial fibrillary acidic protein (GFAP) immunohistochemical analyses were carried out after the last MWM assessment. The immunohistochemistry results showed notable differences among the groups, particularly between the AD and ATD groups. This study reveals that repetitive anodal tDCS can not only improve cognitive function and memory performance but also has long-term after-effects that persist for 2 months.

Synergistic Myoelectrical Activities of Forearm Muscles Improving Robust Recognition of Multi-Fingered Gestures.

Currently, surface electromyography (sEMG) features of the forearm multi-tendon muscles are widely used in gesture recognition, however, there are few investigations on the inherent physiological mechanism of muscle synergies. We aimed to study whether the muscle synergies could be used for gesture recognition. Five healthy participants executed five gestures of daily life (pinch, fist, open hand, grip, and extension) and the sEMG activity was acquired from six forearm muscles. A non-negative matrix factorization (NMF) algorithm was employed to decompose the pre-treated six-channel sEMG data to obtain the muscle synergy matrixes, in which the weights of each muscle channel determined the feature set for hand gesture classification. The results showed that the synergistic features of forearm muscles could be successfully clustered in the feature space, which enabled hand gestures to be recognized with high efficiency. By augmenting the number of participants, the mean recognition rate remained at more than 96% and reflected high robustness. We showed that muscle synergies can be well applied to gesture recognition.

Spatial Reorganization of Myoelectric Activities in Extensor Digitorum for Sustained Finger Force Production.

The study aims to explore the spatial distribution of multi-tendinous muscle modulated by central nervous system (CNS) during sustained contraction. Nine subjects were recruited to trace constant target forces with right index finger extension. Surface electromyography (sEMG) of extensor digitorum (ED) were recorded with a 32-channel electrode array. Nine successive topographic maps (TM) were obtained. Pixel wise analysis was utilized to extract subtracted topographic maps (STM), which exhibited inhomogeneous distribution. STMs were characterized into hot, warm, and cool regions corresponding to higher, moderate, and lower change ranges, respectively. The relative normalized area (normalized to the first phase) of these regions demonstrated different changing trends as rising, plateauing, and falling over time, respectively. Moreover, the duration of these trends were found to be affected by force level. The rising/falling periods were longer at lower force levels, while the plateau can be achieved from the initial phase for higher force output (45% maximal voluntary contraction). The results suggested muscle activity reorganization in ED plays a role to maintain sustained contraction. Furthermore, the decreased dynamical regulation ability to spatial reorganization may be prone to induce fatigue. This finding implied that spatial reorganization of muscle activity as a regulation mechanism contribute to maintain constant force production.