基于大脑神经元放电的脑-机接口技术

基于大脑运动皮层神经元放电的脑-机接口通过记录大脑运动皮层神经元的放电信号控制瘫痪肢体或假肢运动,其软硬件核心为神经元群体解码和神经元放电活动的检测。解码方法分为推理算法和分类器方法,检测方法通过在大脑运动皮层区植入长效电极记录单个或群体神经元的放电活动。分析表明,脑-机接口技术应在更多脑区域上植入长效电极达到更好控制设备的目的,各类解码算法应通过联合并加入反馈信号提高对神经元信号的解码效果。     

基于Monte Carlo在体生物光学成像的光子传输模型

随着分子标记技术和光学成像技术的发展,在体生物光学成像倍受关注,并广泛应用于对生物组织的生理或病理过程的无损实时动态成像.研究生物组织中的光子传输模型和光子传输规律,是开展在体生物光学成像研究的两个关键环节.提出了一种基于Monte Carlo方法的在体生物光学成像中的光子传输模型.已知荧光光源参数、生物组织参数和探测器参数,建立荧光光源发射光子、光子在生物组织中传输的数学模型,并利用Monte Carlo方法实现这些模型.最后做了对比实验,实验结果表明了该算法的正确性和有效性.     

多光子激发随机扫描显微成像软件系统仿真

多光子激发随机扫描显微成像系统将为神经功能成像提供一个有效工具而成为研究热点,但成像软件系统的研制是其难点之一。分析了多光子激发随机扫描显微成像的实验流程,在VC6.0开发平台下,对飞秒激光扫描控制和荧光信号采集,全视场图像重构,感兴趣区域选取,图像和信号曲线动态同步显示等主要功能进行了软件仿真,对开发完整的多光子激发随机扫描显微成像软件系统具有重要的参考价值。     

在体生物光学成像技术的研究进展

在体生物发光成像和在体荧光成像是近年来新兴的在体生物光学成像技术, 能够无损实时动态监测被标记细胞在活体小动物体内的活动及反应, 在肿瘤检测、基因表达、蛋白质分子检测、药物受体定位、药物筛选和药物疗效评价等方面具有很大的应用潜力. 本文详细介绍了在体生物发光成像和在体荧光成像的特点、系统及应用, 比较了它们的异同, 综述了在体生物光学成像技术的基本原理和应用领域, 讨论了将其应用于临床的进一步发展方向.     

基于多类最小二乘支持向量机的神经元信号识别

针对大脑运动皮层群体神经元信号与运动行为关系的分析,提出一种基于二叉树的最小二乘支持向量机多类分类算法.在对猴子进行三维空间中8个方向手臂运动实验记录的多通道神经元信号的分析中,通过与标准支持向量机和学习矢量量化神经网络的比较,说明该方法不仅与标准支持向量机同样具有比学习矢量量化方法更强的学习能力和预测能力,而且运算时间比标准支持向量机更短.比较结果表明最小二乘支持向量机对于神经元信号分析的有效性和优越性,进而有利于实现性能更高的用于神经康复的脑机接口系统.     

无线光刺激与神经传感系统

光遗传神经调控正在向闭环技术发展,针对实验动物可自由活动的需求,研发具有大范围光刺激、神经信号同步记录、无线程控等功能的无线光刺激与神经传感系统。该系统包括光刺激—电记录神经接口、刺激传感模块、无线收发模块以及上位机软件。可无线实时调节光刺激频率、幅度和占空比等参数,并同步采集神经信号。给予小鼠刺激运动皮层30Hz光刺激,小鼠运动明显增强,同时记录到刺激诱发的脑电信号。系统为光遗传技术提供多功能神经调控平台,有助于神经环路和神经疾病的长时程研究。     

研发动态

正美开发出皮下植入式碳纳米管传感器美国麻省理工学院的研究人员开发出一种碳纳米管传感器,被植入皮肤下后,可全年实时监测活体动物体内的分子活动,如炎症反应即产生一氧化氮(NO)的过程,或监测血糖或胰岛素水平,而无需再像传统方式那样采取血样.一氧化氮是活细胞中最重要的信号分子,具有在大脑内运送信息及调整免疫系统的功能.在     

基于Actor-Critic和神经网络的闭环脑机接口控制器设计

在皮层神经元放电活动模型的基础上进行单关节自发运动的研究,从控制理论的角度分析闭环脑机接口的工作原理.使用卡尔曼滤波器和人工神经网络设计系统的解码器替代原系统的脊髓电流,并且比较这两种解码器的优劣.由于在无感知反馈的信号下,解码器的性能下降得比较明显,使用强化学习中Actor-Critic算法结合人工神经网络设计PID控制器,用以产生刺激信号来刺激大脑皮层神经元,使其能够跟踪有感知反馈信号时皮层神经元的放电活动,从而恢复解码器的性能.最后,通过与其他控制算法对比,验证了基于强化学习算法的人工感知反馈信号设计的有效性.     

时滞对化学突触耦合的神经元网络放电节律的影响

大脑中许多功能区可以呈现出不同形式的神经网络振荡活动,它们反映群体神经元的同步活动以及大脑的不同功能状态。高频节律反映的是大脑局部区域较快的信息处理,低频节律则能够反映外部的感觉输入和内部的认知事件的动态驱动在不同脑区的传播过程。这些不同形式的振荡活动分别在大脑处理、传递和整合感觉信息,巩固记忆,以及一些高级认知活动(如注意行为)中发挥重要的作用。其中,调整神经网络活动的振荡特性是实现这些脑功能的可能机制之一。本文发现突触的连接强度增大,可以加强同步。随着时滞的增大,在初始周期T的整数倍处,簇中spiking的个数会逐渐增加。神经元的频率会属于不同波段,且会出现混合振荡的状态。对于小的时滞,振荡是低频的。当时滞超过一定的值之后,网络从低频变为高频低频共存的状态,出现了混合振荡状态,并且这种转换快速且稳定。     

软件刺激系统 助残疾人康复一臂之力

正你能想像一个瘫痪的老鼠用它两条后腿,在计算机的控制下迈着精准的步伐走路吗?"这真有点儿科学怪人的感觉,"Gregoire Courtine说道,他是瑞士洛桑联邦理工大学的一名神经科学家。他在近期一篇论文中,阐述了利用电子学让瘫痪动物恢复正常运动。这项研究的研究人员希望尝试用电子脉冲刺激瘫痪患者的脊髓,继而帮助他们重新恢复行走的能力,这些信号可以替代那些通过脊髓传递给大脑的普通命令,因为脊椎受伤后,传递到大脑的行走命令也因此被中断。     

Differences in low back load between kneeling and seated working at ground level

The effects of the load on the low back when working in a kneeling posture were compared to those when working on a chair designed to alleviate work load in harvesting radish. In 10 male subjects data regarding back muscle fatigue and length changes of the spine, and estimates of experienced discomfort were collected. The results show that for all three effects of back load working on the chair leads to lower levels as compared to working kneeling. However, back load and discomfort were lower when working on the chair, back discomfort still increased substantially during the work on the chair. It is thus a sub-optimal solution from an ergonomic point of view, but at present it could be recommended to allow for variation with the conventional working method.     

Electromyography as a measure of peak and cumulative workload in intermediate care and its relationship to musculoskeletal injury: an exploratory ergonomic study

Injury rates in Intermediate Care (IC) facilities are high and the factors related to these injuries are unclear. The objectives of this exploratory sub-study, which is part of a large multi-faceted study in 8 IC facilities are to: (1) evaluate EMG measured over a full-shift in the back and shoulders of 32 care aides (CAs) as an indicator of peak and cumulative workload (n = 4 x 8 facilities); investigate the relationship between EMG measures and injury indicators; and explore the relationship between EMG measures and other workload measurements. Lumbar EMG was converted to predicted cumulative spinal compression and ranged in CAs from 11.7 to 22.8 MNs with a mean of 16.4 MNs. Average compression was significantly different during different periods of the day (p < 0.001) with highest compression during pre-breakfast when CAs assist most with activities of daily living. Significant differences were found in average compression between low and high injury facilities for 3 of 5 periods of the day (p < 0.010). Peak compressions exceeding 3400 N occurred for very little of the workday (e.g. 11.25s during the 75 min period pre-breakfast). Peak neck/shoulder muscle activity is low (99% APDF ranged from 8.33% to 28% MVC). Peak and cumulative spinal compression were significantly correlated with lost-time and musculoskeletal injury rates as well as with total tasks observed in the CAs (p < 0.01). Perceived exertion was only correlated with peak compressions (p < 0.01). Facilities with low injury rates provided significantly more CAs (p < 0.01) to meet resident needs, and subsequently CAs performed fewer tasks, resulting in less peak and cumulative spinal loading over the day.     

School furniture and the user population: an anthropometric perspective

The purpose of this study was to determine the relationship between reported spinal symptoms in an adolescent student population, and the match between their individual anthropometric dimensions and their school furniture. The hypothesis was that students who were too large or too small for their school furniture, i.e. with anthropometric measurements furthest from the group whose anthropometry was the ‘best fit’ with the furniture, would have a higher frequency of reported symptoms. From data collected from 1269 schoolchildren, reported spinal symptoms and anthropometric measures were examined. Stature measures were divided into quartiles. A standard government issue school chair and desk was measured and the anthropometric quartile of the population having the ‘best fit’ with the furniture was identified using standard ergonomics recommendations. Odds ratios were calculated for spinal symptoms reported within each quartile group. The first quartile group (the smallest students) was identified as having the ‘best fit’ with the school furniture. An overall higher odds of reporting low back pain was noted in students with anthropometric dimensions in the fourth quartile (the tallest students). While it is acknowledged that there is a multifactorial nature of causality of adolescent spinal symptoms, it is contended that the degree of mis-match between child anthropometry and school furniture set-up should be further examined as a strong and plausible associate of adolescent low back pain.     

Predictive discomfort of supine humans in whole-body vibration and shock environments

This work presents a predictive model to evaluate discomfort associated with supine humans during transportation, where whole-body vibration and repeated shock are predominant. The proposed model consists of two parts: (i) static discomfort resulting from body posture, joint limits and ambient discomfort; and (ii) dynamic discomfort resulting from the relative motion between the body segments as a result of transmitted vibration. Twelve supine subjects were exposed to single and 3D random vibrations and 3D shocks mixed with vibrations. The subjects’ reported discomfort and biodynamic response were analysed under different support conditions, including a rigid surface, a stretcher and a stretcher with a spinal backboard. The results demonstrated good correlations between the predictive discomfort and the reported discomfort for the different conditions under consideration, with R² = 0.69–0.94 for individual subjects and R² = 0.94 for the group mean. The results also indicated a strong relationship between the head-neck and trunk angular velocities and discomfort during supine transportation.

Practitioner Summary: The quantification of discomfort of supine humans under vibration and shocks by using a predictive model is an important contribution to this field, whereby the efficacy of different transport systems can be compared. The predictive discomfort model can be used as design criteria for ergonomic enhancement in supine transportation of humans.     

A validation of a posture matching approach for the determination of 3D cumulative back loads

The purpose of this project was to investigate the amount of error in calculating cumulative lumbar spine kinetics using a posture matching approach (3DMatch) compared to a 3D coordinate electromagnetic tracking approach (FASTRAK). Six subjects were required to perform five repeats each of two symmetrical and two asymmetrical lifts while being simultaneously recorded from 4 camera views at viewing angles of 0 degrees , 45 degrees , 60 degrees and 90 degrees to the sagittal plane while wearing eight FASTRAK sensors to define an 8 segment rigid link model (RLM) of the head, arms, and trunk. Four hundred and eighty lifts (6 subjects x20 lifts x4 camera views) were analyzed using the 3DMatch posture-matching program to calculate the following cumulative loads at the L4/L5 joint: compression, anterior shear, posterior shear, reaction shear and extension moment. The errors in cumulative load calculation were determined as the difference between the values calculated for the same lifts using a 3D RLM that used electromagnetic motion tracking sensors (FASTRAK) positioned at the segment center of masses as model inputs. No significant difference (p<0.05) in the relative error for any of the cumulative loading variables between the four camera views and the 3D RLM approach was found. Furthermore the relative errors for cumulative compression, joint anterior shear, reaction anterior shear and extension moment were all below 12%. These results suggest that posture matching by trained users can provide reasonable 3D data to calculate cumulative low back loads with a biomechanical model.     

Spine as an engine: effect of spine morphology on spine-driven quadruped locomotion

In quadruped animals, spinal movements contribute to locomotion in terms of controlling body posture and integrating limb and trunk actions. In this paper, we develop quadruped models with different numbers of spinal joints to demonstrate the spine-driven locomotion. Actuated spinal joint(s) are exclusively employed to these models with a minimalistic control strategy. We choose some typical individuals from two models and analyze them on gait properties. Results show that employing the spine morphology with two joints can greatly enhance the stability and speed of locomotion by readjusting the center of mass, increasing the stride length, and generating double flight phases similar to running cheetahs’ gait, which makes significant difference in the speed and the gait. Furthermore, we explore and compare models with more spinal joints. Results show that all gaits emerged from them can be categorized into three types (bounding, bounding with double flight phase, and stotting gaits). Overall, bounding gait with double flight phases is a more biologically inspired locomotive behavior; model with two spinal joints could be sufficient to emulate biological spine-driven locomotive behaviors.     

Three-dimensional spinal motion and risk of low back injury during sheep shearing

Sheep shearers are known to work in sustained flexed postures and have a high prevalence of low back pain (LBP). As sustained posture and spinal movement asymmetry under substantial loads are known risk factors for back injury our aim was to describe the 3D spinal movement of shearers while working. We hypothesised that thoraco-lumbar and lumbo-sacral movement would be tri-axial, asymmetric, and task specific. Sufficient retro-reflective markers were placed on the trunk of 12 shearers to define thoraco-lumbar and lumbo-sacral 3D motion during three tasks. Thoraco-lumbar movement consistently involved flexion, left lateral flexion, and right rotation. Lumbo-sacral movement consistently involved right lateral flexion in flexion with minimal rotation. Shearers therefore work in sustained spinal flexion where concurrent, asymmetric spinal movements into both lateral flexion and rotation occur. These asymmetric movements combined with repetitive loading may be risk factors leading to the high incidence of LBP in this occupational group.     

基于基准点的蚂蚁算法在胎儿脊柱裂超声图像边缘检测中的应用

胎儿脊柱裂超声图像一般较为模糊不易判断识别,该文基于蚁群算法,提出了一种新的胎儿脊柱裂超声图像边沿检测方法。针对超声图像特点,算法对信息素及食物源的设置进行了改进,阐述了该算法,同时将检测结果与Sobel算法的结果进行了比较,实验证明该改进的蚂蚁算法提取出了清晰的胎儿脊柱裂的边沿。     

Effect of work-rest schedules on spinal shrinkage in the sedentary worker

The relationship between duration and frequency of rest intervals and spinal shrinkage was investigated. The objective was to determine whether the amount of spinal shrinkage can be significantly reduced by rest breaks during which the individual is either walking or standing rather than sitting.

Seven subjects were studied during 4-h sessions for four consecutive days. During each session the subject sat and typed for a total of 3 h 20 min. Forty minutes of rest breaks were dispersed throughout the 4-h period. One condition was administered during each day with either eight breaks of 5 min, four breaks of 10 min, two breaks of 20 min or a single break of 40 min at the end of the work session.

Using a stadiometer, changes in stature were measured with an accuracy of about 0·2 mm. Measurements were taken at the beginning of each work period and before and after each rest break. For the conditions with rest breaks of 20 or 40 min, there was significantly less shrinkage at the end of the 4-h work session.     

Continuous assessment of back and upper arm postures by long-term inclinometry in carpet weavers

Awkward back and shoulder postures have been suggested to be a cause of back and shoulder discomfort in carpet weavers. This study aimed at continuous assessment of the upper arm and back postures and estimation of biomechanical load subtasks using inclinometers during 4 h.Median of trunk flexion angle in weavers was 18° and 13° during knotting and compacting subtasks, respectively. The weavers worked with arms elevated greater than 45° for %4.5 of the work time. The average cumulative compression load for males and females were estimated at 22 MN-S and 13 MN-S, respectively.In addition to poor workstation design, constrained posture of the trunk and low elevation and velocity for both arms may be the main risk factors for developing fatigue and disorders in the back and shoulder regions among carpet weavers. Therefore, any ergonomic interventions should be focused on reducing trunk flexion and the constrained postures of weavers.