Beta Changes Induced by Acute Hand Loss Model during NMES.

Neuromuscular electrical stimulation (NMES) has been demonstrated to effectively modulate cortical activities by evoking muscle contraction in upper limb and generating joint movements, which showed an excellent performance in motor rehabilitation. However, due to hand loss and cortical function reorganization induced by hand amputation, how neural activities in sensorimotor cortex response to NMES-evoked muscle contraction in the end of an amputation stump is not clear. In this paper, Ischemic nerve block (INB) technique was used to build an acute hand loss model, and 64-channel EEG signals were recorded from 11 healthy subjects to perform a 2×2 factorial design protocol, with the INB state and the current intensity as factors. The changes of NMES-evoked sensorimotor cortical activities were quantified by computing Beta-band event-related desynchronization (Beta ERD) patterns and the time-varying functional connectivity using adaptive directed transfer function (ADTF) before and during INB. The acute hand "loss" resulted in ipsilateral dominance of Beta ERD induced by NMES with two current intensities in the topographic maps, that is, ipsilateral Beta ERD was significantly higher than that the contralateral one (p<0.05). However, before INB, Beta ERD in the contralateral sensorimotor cortex induced by NMES above motor threshold was significantly higher than that in the ipsilateral area (p< 0.01). Meanwhile, whatever before or during INB, clustering coefficients of the ADTF network in sensorimotor cortex showed temporal dynamics during two NMES tasks. During INB, NMES above motor threshold-evoked lower clustering coefficients of the time-varying network in sensorimotor cortex than that before INB (p<0.05). The present results suggest that the loss of the hand proprioception will degrade cortical activities in the contralateral area, and increase cortical activities in the ipsilateral area compensatively responding to NMES. This finding may be particularly important to improve the reconstruction of the proprioception function of hand prosthesis.

The Kinematic-Muscle Synergies during Infant Crawling: A Pilot Study.

Many feature extraction algorithms have been separately used for kinematic or muscle synergy analysis during human movement. However, very few studies focus on the co-extraction of kinematic and muscle synergies. Therefore, the aim of this study was to propose a novel and efficient approach for extracting the kinematic-muscle synergies during infant crawling. Surface electromyography signals and three-dimensional joint trajectories were collected from 20 typically developing infants during self-paced hands-and-knees crawling. Angular accelerations of shoulder, elbow, hip and knee flexion/extension computing from those joint trajectories were divided into two independent directional positive degrees-of-freedom. The kinematic-muscle synergies and corresponding activation coefficients were extracted using the non-negative matrix factorization algorithm based on two selection criteria of synergy number (i.e., criterion 1: the total constraint, criterion 2: a combination of the total constraint and a local constraint for each joint/muscle). Then, the data of each joint/muscle were reconstructed by those synergies and corresponding activation coefficients. Our results indicated that the minimum number of kinematic-muscle synergies based on criterion 1 is less than that based on criterion 2. The data reconstruction of joint flexion/extension based on criterion 2 is better than that based on criterion 1, whereas the data reconstruction of muscles is similar between criterion 1 and 2. These promising results show the feasibility of applying the proposed approach to clinical assessments of motor function for infants.Clinical Relevance- Extracting kinematic-muscle synergies during infant crawling has the potential for professional therapists or rehabilitation physicians to conduct the early assessment and rehabilitation treatment of infants with the central nervous system disorders.

Impacts of Motor Developmental Delay on the Inter-Joint Coordination Using Kinematic Synergies of Joint Angles During Infant Crawling.

Motor developmental delay (MDD) usually affects the inter-joint coordination for limb movement. However, the mechanism between the abnormal inter-joint coordination and MDD is still unclear, which poses a challenge for clinical diagnosis and motor rehabilitation of MDD in infant's early life. This study aimed to explore whether the joint activities of limbs during infant crawling are represented with kinematic synergies of joint angles, and evaluate the impacts of MDD on the inter-joint coordination using those synergies. 20 typically developing infants, 16 infants at risk of developmental delay, 11 infants at high risk of developmental delay and 13 infants with confirmed developmental delay were recruited for self-paced crawling on hands and knees. A motion capture system was employed to trace infants' limbs in space, and angles of shoulder, elbow, hip and knee over time were computed. Kinematic synergies were derived from joint angles using principal component analysis. Sample entropy and Spearman's rank correlation coefficients were calculated among those synergies to evaluate the crawling complexity and the symmetry of bilateral limbs, respectively. We found that the first two synergies with different contributions to the crawling movements sufficiently represented the joint angular profiles of limbs. MDD further delayed the development of motor function for lower limbs and mainly increased the crawling complexity of joint flexion/extension to some extent, but did not obviously change the symmetry of bilateral limbs. These results suggest that the time-varying kinematic synergy of joint angles is a potential index for objectively evaluating the abnormal inter-joint coordination affected by MDD.

Multiple Sessions of Entorhinal Cortex Deep Brain Stimulation in C57BL/6J Mice Increases Exploratory Behavior and Hippocampal Neurogenesis.

Deep brain stimulation (DBS) has been a medical intervention for a variety of nervous system diseases and mental diseases. The input of DBS in the entorhinal cortex (EC) regulates the neurophysiological activities in its downstream regions, such as the dentate gyrus (DG) area. EC DBS may play a role in the treatment of diseases through hippocampal neurogenesis. This study we examined the effect of multiple sessions of EC DBS on the regulation of hippocampal neurogenesis. 4-month-old male C57BL/6J mice received bilateral multiple sessions of EC DBS (130 Hz, 90 µs, 100 µA, 1 h/d, 21 days), and the DBS parameters used are close to the high-frequency DBS parameters in clinical studies. The open field test (OFT) was used to test the exploratory behavior of mice, and hippocampal neurogenesis was detected by immunofluorescence staining with anti-doublecortin (DCX). We found that multiple sessions of EC DBS were tolerated in C57BL/6J mice, significantly increased exploratory behavior and the number of DCX-positive neurons in the DG area.Clinical Relevance- Hippocampal neurogenesis may be part of the reason for DBS to improve memory, and the results of this study show that multiple sessions of EC DBS increases exploratory behavior and hippocampal neurogenesis, which is conducive to the application of DBS in nervous system diseases and mental diseases related to memory impairment.

Angular Velocity Profiles of Upper Limb Joint Synergies in Reaching Movements: a pilot study.

The spatiotemporal kinematic synergy, a coupling of multiple degrees of freedom (DoF), runs through human activities of daily living (ADL). And it is an entry point for exploring the central nervous system's (CNS) control process of musculoskeletal system by analyzing the time-varying kinematic synergy. The aim of this study was to find more physiological properties from the angular velocity profiles of synergy. Ten healthy right-handed subjects were asked to reach target button at different locations. During reaching movement, the motion data of five right upper limb joints were recorded, and the synergistic patterns were extracted by PCA algorithm. Our results showed that the combinations of the first four synergies were sufficient to explain raw data. As far as possible to exclude the effects of individual and information differences, we found shoulder flexion/extension and elbow flexion/extension made distinct contribution in a period of time to the control procedure performed by CNS after targets were confirmed. Our preliminary results implied that reaching movements required comparatively constant scheduling of shoulder horizontal abduction/adduction, shoulder internal/external rotation and wrist ulnar/radial deviation by CNS, while scheduling of SFE and EFE depends on the objectives.Clinical relevance- The findings of this paper may provide a novel dynamic control evidence based on CNS for realizing near-natural control of assistive devices in motor rehabilitation area.

Study on the Establishment Process of Muscle Synergy Based on Cosine Similarity.

Muscle synergy is an important method for motor intention recognition in rehabilitation exoskeleton control. The use of the non-negative matrix factorization (NMF) to extract muscle synergy patterns often results in long calculation time due to the amount of data, which makes the effectiveness of synergy extraction low. In this paper, synergy matrices of the complete single-cycle signal while stretching and its segmented ones were extracted respectively. By studying the cosine similarity variation of synergy matrices between each continuous segment and the complete single-cycle EMG signals, it is found that there is a "building-stability-weakening" process on muscle synergy establishment. It is proposed to extract synergy mode with partial data from the "stable" segment, rather than using the complete single-cycle one, as similar result to single-cycle data synergy extraction could be obtained. The calculation time of NMF could be optimized by reducing the amount of data and the real-time characteristics of the synergy mode extraction could be improved at the same time. It is of great significance to use synergy matrix of NMF for motion intention recognition and exoskeleton control.Clinical Relevance- This paper studies the establishment process of the synergy mode, and proposes a method for quickly extracting the synergy mode, which can improve the effectiveness of the recognition of motion intention and is of great significance for the real-time control of the rehabilitation exoskeleton.

Measurement and Analysis of Human Infant Crawling for Rehabilitation: A Narrative Review.

When a child shows signs of potential motor developmental disorders, early diagnosis of central nervous system (CNS) impairment is beneficial. Known as the first CNS-controlled mobility for most of infants, mobility during crawling usually has been used in clinical assessments to identify motor development disorders. The current clinical scales of motor development during crawling stage are relatively subjective. Objective and quantitative measures of infant crawling afford the possibilities to identify those infants who might benefit from early intervention, as well as the evaluation of intervention progress. Thus, increasing researchers have explored objective measurements of infant crawling in typical and atypical developing infants. However, there is a lack of comprehensive review on infant-crawling measurement and analysis toward bridging the gap between research crawling analysis and potential clinical applications. In this narrative review, we provide a practical overview of the most relevant measurements in human infant crawling, including acquisition techniques, data processing methods, features extraction, and the potential value in objective assessment of motor function in infancy; meanwhile, the possibilities to develop crawling training as early intervention to promote the locomotor function for infants with locomotor delays are also discussed.

3D MR image denoising using a modified adaptive high order singular value decomposition method.

Magnetic resonance (MR) images are generally degraded by random noise governed by Rician distributions. In this study, we developed a modified adaptive high order singular value decomposition (HOSVD) method, taking consideration of the nonlocal self-similarity and weighted Schatten p-norm. We extracted 3D cubes from noise images and classified the similar cubes by the Euclidean distance between cubes to construction a fourth-order tensor. Each rank of unfolding matrices was adaptively determined by weighted Schatten p-norm regularization. The latent noise-free 3D MR images can be obtained by an adaptive HOSVD. Denoising experiments were tested on both synthetic and clinical 3D MR images, and the results showed the proposed method outperformed several existing methods for Rician noise removal in 3D MR images.

Cerebral blood microcirculation measurement in APP/PS1 double transgenic mice at the preclinical stage of Alzheimer's disease: preliminary data on the early intervention of anodal transcranial direct current stimulation.

Anodal transcranial direct current stimulation (AtDCS) can improve memory and cognitive dysfunction in patients with Alzheimer's disease (AD), which has been proven in basic and clinical studies. Intervention of AD in preclinical stage is important to prevent progression of AD in the aging society. At the same time, there is increasing evidence that a close link exists between cerebrovascular dysfunction and AD disease. Here we investigated the changes of local cerebral blood microcirculation in preclinical AD mouse model after AtDCS based on the previous studies. Twenty-four 6-month-old male APP/PS1 double transgenic mice were randomly divided into three groups: a model group (AD), a model sham stimulation (ADST) group and a model stimulation group (ATD). Eight 6-month-old male C57 wild-type mice served as a control group (CTL). Mice in the ATD group received 10 AtDCS sessions. Two months after the end of AtDCS in the ATD group, the microcirculation parameters of the frontal cortex of the mice in each group, including cerebral blood flow (CBF), blood flow velocity (Velo), oxygen saturation (SO2) and relative hemoglobin content (rHb), were obtained by the non-invasive laser-Doppler spectrophotometry system "Oxygen-to-See (O2C)". The results showed that AtDCS increased CBF, Velo and SO2, and reduce rHb in APP/PS1 double transgenic mice at the preclinical stage of AD.Clinical Relevance-This shows the positive effect of AtDCS on preclinical AD in cerebrovascular function, and provides effective basic research facts for AtDCS to intervene and delay the clinical application of AD disease.

A Modified Higher-Order Singular Value Decomposition Framework With Adaptive Multilinear Tensor Rank Approximation for Three-Dimensional Magnetic Resonance Rician Noise Removal.

The magnetic resonance (MR) images are acknowledged to be inevitably corrupted by Rician distributed noise, which adversely affected the image quality for diagnosis purpose. However, the traditional denoising methods may recover the images from corruptions with severe loss of detailed structure and edge information, which would affect the lesion detections and diagnostic decision making. In this study, we challenged improving the Rician noise removal from three-dimensional (3D) MR volumetric data through a modified higher-order singular value decomposition (MHOSVD) method. The proposed framework of MHOSVD involved a parameterized logarithmic nonconvex penalty function for low-rank tensor approximation (LRTA) algorithm optimization to suppress the image noise in MR dataset. Reference cubes were extracted from the noisy image volume, and block matching was performed according to nonlocal similarity for a fourth-order tensor construction. Then the LRTA problem was implemented by tensor factorization approaches, and the ranks of unfolding matrices along different modes of the tensor were estimated utilizing an adaptive nonconvex low-rank method. The denoised MR images were finally restored through aggregating all recovered cubes. We investigated the proposed algorithm MHOSVD on both the synthetic and real clinic 3D MR images for Rician noise removal, and relative results demonstrated that the MHOSVD can recover images with fine structures and detailed edge preservation with heavy noise even as high as 15% of the maximum intensity. The experimental results were also compared along with several classical denoising methods; the MHOSVD exhibited a sufficient improvement in noise-removal performance at various noise conditions in terms of different measurement indices such as peak signal-to-noise ratio and structural similarity index metrics. Based upon the comparison, the proposed MHOSVD has proved a relative state-of-the-art performance with excellent detailed structure reservation.

Analysis of the Inter-Joints Synergistic Patterns of Limbs in Infant Crawling.

Hands and knees crawling is an important motor developmental milestone, which is characterized by diagonal coordination between upper and lower limbs. However, the features of inter-joint synergy within each limb in infant crawling is still not clear. Therefore, the aim of this study was to extract the inter-joint synergistic patterns during infant crawling and to test the possibilities of using the extracted inter-joint synergy to distinguish developmental delayed (DD) infants from typical developing (TD) infants. In this paper, kinematic data were collected from the shoulder, elbow, wrist, hip, knee, and ankle joints when 9 TD infants and 9 DD infants were crawling on hands and knees at their self-selected velocity. Tangential velocity was firstly calculated from the three-dimensional (3D) trajectory of each joint. Then, the non-negative matrix factorization (NMF) method was used to extract the joints synergistic patterns of each limb from the tangential velocity data. Our preliminary results showed that the crawling movement could be represented by a joint synergistic pattern, which consisted of three joints' data. In addition, we observed that the distal joint had a greater impact than the proximal joints during infant crawling. Moreover, it was found that the DD infants could be preliminarily distinguished from the TD infants by the features of inter-joint synergy during their crawling stage.

Infrared Laser Pulses Excite Action Potentials in Primary Cortex Neurons In Vitro.

Infrared neural modulation (INM) has been well studied in the peripheral nervous system (PNS) for potential clinical applications. However, limited research has been conducted on the central nervous systems (CNS). In this study, we aimed at investigating the feasibility of using pulsed infrared (IR) laser with a wavelength of 1940 nm to excite network activity of cultivated rat cortex neurons.We cultured rat cortex neurons, forming neural networks with spontaneous neural activity, on glass multi-electrode arrays (MEAs). Laser at a power of 600 mW and a pulse rate of 10 Hz were used to stimulate the neural networks using the optics of an inverted microscope. Pulse durations were varied from 200 µs to 1 ms. The spike rate was calculated to evaluate the change of the neural network activity during the IR stimuli and the corresponding frequency components of neural response were calculated to examine whether recorded spikes were evoked by the IR pulse or not. A temperature model was adapted from a previous study to estimate the temperature rise during laser pulsing.We observed that the IR irradiation with a pulse duration of 800 µs and 1 ms could excite neuronal action potentials. The temperature rose 18.5 and 23.9 °C, for pulse durations of 800 µs and 1 ms, respectively. Thus, in addition to previously shown inhibition of IR irradiation with a wavelength of 1550 nm, we demonstrate an optical method that can modulate neural network activity in vitro. The preliminary results from this paper also suggested that MEA recording technology coupled with a laser and microscope systems can be exploited as a new approach for future studies to understand mechanisms and characterize laser parameters of INM for CNS neurons.

Inter-Limb Muscle Synergies and Kinematic Analysis of Hands-and-Knees Crawling in Typically Developing Infants and Infants With Developmental Delay.

Hands-and-knees-crawling is an important motor developmental milestone and a unique window into the development of central nervous system (CNS). Mobility during crawling is regularly used in clinical assessments to identify delays in motor development. However, possible contribution from CNS impairments to motor development delay is still unknown. The aim of this study was to quantify and compare inter-limb muscle synergy and kinematics during crawling among infants at a similar developmental age, however, clinically determined to be typically developing (TD, N = 20) infants, infants at risk of developmental delay (ARDD, N = 33), or infants with confirmed developmental delay (CDD, N = 13). We hypothesized that even though all of the groups are at a similar developmental age, there would be differences in kinematic measures during crawling, and such differences would be associated with CNS impairment as measured by electromyography (EMG) features. Surface EMG of eight arm and leg muscles and the corresponding joint kinematic data were collected while participants crawled on hands and knees at their self-selected velocity. Temporal-spatial parameters and normalized Jerk-Cost (JC) function (i.e., smoothness of movement) were computed from the measured kinematics. The inter-limb muscle synergy and the number of co-activating muscles per synergy were measured using EMGs. We found that the infants with CDD demonstrated higher normalized JC values (less movement smoothness), fewer muscle synergies, and more co-activating muscles per synergy, compared to infants with TD (p < 0.05) and ARDD (p < 0.05). Furthermore, the normalized JC values were correlated (p < 0.05) with the number of co-activation muscles per synergy. Our results suggest a constrained neuromuscular control strategy due to neurological injury in infants with CDD, and such constrain may contribute to the reduced movement smoothness in infant crawling.

Inter-Limb Muscle Synergy of Hands-and-Knees Crawling in Typical Developing Infants and Infants with Developmental Delay.

The aim of this study was to quantify and compare the inter-limb muscle coordination during crawling between typically developing infants and infants with developmental delay. Typically developing (TD, $\text{N}=$20) infants and infants with at risk of developmental delay (ARDD, $\textbf{N}=$33) or confirmed developmental delayCDD, N=14) participated in this study. Surface electromyography of eight muscles from arms and legs and the corresponding joint kinematic data were collected while they were crawling on hands and knees at their self-selected velocity. The number of used inter-limb muscle synergies during crawling was identified by nonnegative matrix factorization algorithm. Our results showed that there was no significant difference in the number of used muscle synergies between ARDD and TD infants during crawling. However, a reduced number of synergies were identified in infants with CDD, as compared to that in TD and ARDD infants, indicating constrained neuromuscular control strategy during crawling in developmental delayed infants. The absence of inter-limb muscle synergies may be one of the mechanisms underlying the impairments of crawling in developmental delayed infants, who are at high risk of cerebral palsy. This result also suggests that the metrics of muscle synergy during infant crawling, such as the number of synergy, may be feasible as a biomarker for early diagnosis of infants with cerebral palsy.

Synergistic recruitment of multi-scale myoelectric oscillations of upper limb during infant crawling.

It has been widely accepted that the central nervous system (CNS) modulates muscle synergies to simplify motion control. However, it is still unclear that if there is a synergistic recruitment strategy to organize oscillation components of surface electromyography (sEMG) signals for limb movement. The sEMG signals were recorded from bilateral biceps brachii (BB) and triceps brachii (TB) muscles during infant crawling. The multivariate empirical mode decomposition (MEMD) was applied to decompose multi-channel sEMG signals into multi-scale oscillations. Then, non-negative matrix factorization (NMF) method was employed to extract oscillation synergy patterns. The results indicated that there were three stable oscillation synergies in sEMG signals for crawling movement, and the recruitment coefficient curves reflected the role of muscle during crawling movement. Our preliminary work suggested that synergistic recruitment of multi-scale oscillation components maybe a new way to understand the organization of MU recruitment strategy by the CNS.

Neuromuscular Electrical Stimulation with Kilohertz Frequency Alternating Current to Enhance Sensorimotor Cortical Excitability.

Enhancement of cortical excitability has been demonstrated to be beneficial for neural recovery of motor dysfunction, such as stroke and spinal cord injury. Neuromuscular electrical stimulation (NMES) has been widely used to evoke limb movements, resulting in the increasing cortical excitability. Due to the advantages of low skin impedance and less discomfort, an alternative NMES of kilohertz frequency alternating current (KFAC) has been proposed, and the effects of current parameters on evoked torque has been studied. However, few studies concerned cortical excitability effects during KFAC-evoked limb movement. In this paper, we utilized the event-related spectral estimation (ERSP) to calculate the beta ERD values to investigate the effects of KFAC-evoked elbow flexion movement on cortical excitability and compared them with that of passive movement. Firstly, averaged ERSP values were extracted in beta band during elbow flexion movements by sliding a 2Hz wide window for all trails of each subject. And then the minimal value was chosen as the representative value of beta ERD. Finally, the absolute ERD values and the descending slopes of all subjects were both calculated for statistical analysis by one-way repeated measures ANOVA. The results showed KFAC can increase cortical excitability, especially with long pulse duration. Moreover, beta cortical activities during KFAC500-evoked movement are significantly activated than those during passive movement. Therefore, our study may provide a new NMES rehabilitation method to enhance cortical excitability for motor dysfunction patients.

Motor Skill Development Alters Kinematics and Co-Activation Between Flexors and Extensors of Limbs in Human Infant Crawling.

Hands and knees crawling is an important motor developmental milestone but the current clinical measures of motor function during crawling stage are relatively subjective. Objective metrics using kinematics and electromyography (EMG) in infant crawling may provide more stable and accurate measures of such developmental milestone, demonstrating changes in locomotion during age span. The purpose of this paper was to determine whether joint kinematics and the underlying co-activation between flexor and extensor in infant crawling are different for arms and legs across the infant age span. Surface EMG of two pairs of flexors and extensors from arms and legs and the corresponding joint kinematic data were collected in twenty health infants (11 males and 9 females, range 8-15 months), while they were crawling on hands and knees. Co-activation index of averaged EMG was used to quantify the simultaneous contractions between flexor and extensor muscles. Coefficient of variation of joint's maximum vertical acceleration from multiple cycles was used to quantify the repeatability of kinematics during crawling. Our results indicated that the arm exhibited significantly higher co-activation and higher repeatability of joint movement than the leg, suggesting earlier development of arm compared to leg. Moreover, elder age groups, who had stronger walking ability developed, showed increased co-activation of the leg and significant increase in repeatability of the knee movement. These results were consistent with the rapid reinforcement of the leg during motor development from quadrupeds to bipedal walking. Furthermore, the EMG and kinematic parameters were significantly correlated with clinical variables. These results suggest that the EMG and kinematic analysis of infant crawling are useful in building effective assessment of infant's motor function before independent walking.

Auditory responses to short-wavelength infrared neural stimulation of the rat cochlear nucleus.

Pulsed Infrared laser is well-known for its high spatial resolution and contact-free stimulation mode. In order to improve the current auditory brainstem implants (ABI), 980 nm-short-wavelength infrared light was applied to stimulate the cochlear nucleus of rats. Single neural activity from contralateral inferior colliculus was recorded during laser stimulation. Animal experimental results showed that 980 nm laser could not directly activate neurons in cochlear nucleus and a photo-acoustic response was observed during stimulation, however, 980 nm laser produces an inhibitory effect on neural responses to sounds; After we added carbon nanoparticles onto the surface of animal cochlear nucleus, 980 nm laser could directly stimulate neurons and no interference between adjacent recording channels was observed. These findings indicated that with the enhancement of carbon nanoparticles, short-wavelength infrared neural stimulation (SW-INS) might be an effective method to overcome the defects of current ABIs. With this method, a new type of optical ABI with transcutaneous stimulating method is quite promising.

The variability of co-activation pattern of antagonist muscles in human infant crawling.

Infant crawling is part of normal human gross motor development, and a 4-beat gait that involves rhythmical flexion and extension of limbs and the underlying muscle co-activation of antagonist muscle around the joint. However, detection the co-activation pattern of antagonist muscle are sparse due to the general difficulty of measuring locomotion in human infants. In this paper, sEMG of antagonist muscles and the corresponding kinematics data of limbs were collected when infants were crawling on hands and knees at their self-selected speed. The infant's gross motor developmental status was assessed by the global Gross Motor Function Measure Scale (GMFM-88) as well. The method based on EMG-EMG plots was used to quantify the variability of co-activation pattern of antagonist muscle. After that, we observed that antagonist muscles of upper limb (triceps brachii and biceps brachii) showed less variability of co-activation pattern of muscles than lower limb(quadriceps femoris and hamstrings) during crawling, and this variability was also varied in different crawling phases (stance and swing). Furthermore, we found some varied behaviors in the co-activation patterns of antagonist muscles when gross motor developmental level increased. The preliminary work suggests that such adaptive changes may be related to the adjustment of neuromuscular in the early stage of gross motor development.

Neural representation of different mandarin tones in the inferior colliculus of the guinea pig.

Mandarin speech has four different tones and the coding mechanism underlying tone identification still remain unclear. Here in the inferior colliculus (IC) of anesthetized guinea pigs, we recorded single neuron activities to one word with four tones using tungsten electrode. Peri-stimulus time histograms (PSTHs) and inter-spike-interval (ISI) were used to evaluate the neural response. The results showed that PSTHs grouped into frequency band reflected the spectrotemporal patterns of different tones; average population PSTHs matched envelops of different tones; and the peaks of histogram of ISIs in three time segments exhibited a displacement which reflected the profile of fundamental frequency (F0). These preliminary results suggested IC neurons could encode the spectrotemporal acoustic features of different Mandarin tones.