大鼠脊髓不同平面双侧半横切损伤模型的建立及评价

目的建立一种新型大鼠脊髓切割损伤模型,为临床脊髓不同平面损伤研究提供适宜的动物模型。方法45只SD大鼠随机分为脊髓不同平面双侧半横切组(A组,n=15)、脊髓全横切组(B组,n=15)和假手术组(C组,n=15)。术后观察、记录各组大鼠活动、进食水、排尿排便、切口感染等并发症和死亡情况,采用BBB运动功能评分和斜板试验评价大鼠行为学功能。结果术后A组大鼠活动、进食水量减少,53.33%大鼠出现尿潴留,40.00%大鼠于术后1~4周死亡;B组大鼠活动、进食水量明显减少,66.67%大鼠出现尿潴留,60.00%大鼠于术后1~4周死亡;C组大鼠活动、进食水量无明显变化,无并发症及死亡发生。BBB运动功能评分及斜板维持最大角度值检测显示,A、B组均低于C组(P0.05),而这些评价指标在A组和B组之间无显著差异。结论脊髓不同平面双侧半横切损伤模型大鼠尿潴留及死亡率低,行为学评价与脊髓全横切损伤模型类似,适于脊髓不同平面双侧损伤修复的研究。     

体育功能锻炼对截瘫患者康复影响及评价分析

目的:探讨体育功能锻炼对截瘫患者后期康复治疗的影响及康复评价.方法:76例在脊髓损伤后出现截瘫患者,进行体育功能锻炼的康复治疗,追踪记录,采用美国脊髓损伤学会(ASIA)脊髓损伤神经功能分类国际标准评价康复效果.结果:经统计,胸腰髓不完全损害者康复锻炼前后ASIA损伤评分运动、感觉评分均有显著意义(P<0.05).胸腰髓完全损伤者运动、感觉ASIA评分好转较明显(P<0.05).结论:体育功能锻炼能帮助截瘫患者后期恢复,显著改善和提高患者的综合功能.     

NT3-壳聚糖支架诱导内源性神经发生修复脊髓损伤

通常情况下,脊髓损伤后损伤区的微环境是抑制的并充满炎性的,有限激活的内源性神经干/祖细胞几乎全部分化为了参与瘢痕形成的星形胶质细胞。我们的研究表明,生物材料系统可以激活成年哺乳动物中枢神经系统(CNS)内源性神经发生,并促进其迁移和向神经元定向分化。同时,这些新生神经元能够与宿主建立功能性神经网络,最终导致功能恢复,这为脑和脊髓损伤的治疗提供了新的策略和希望。为了进一步阐述其机制,我们采用加权基因共表达网络分析(Weighted gene co-expression network analysis,WGCNA)建立脊髓损伤后不同时空各类事件相应的基因模块/程序分析。这些客观的基因模块表达指标提示,生物材料系统在激活内源性神经发生的同时促进血管发生并降低了炎症反应。     

大鼠脊髓楔型半切空洞模型的建立及评估

摘要: 目的建立一种新型大鼠脊髓半切模型,为临床脊髓空洞损伤研究提供适宜的动物模型。方法25 只SD 大鼠随机分为脊髓楔型块状半切组( A 组,n = 10) 、假手术组( B 组,n = 10) 和正常对照组( C 组,n = 5) 。术后采用 BBB 运动功能评分、斜板试验、HE 染色和核磁共振( MRI) 检测综合评价脊髓半切模型的稳定性。结果术后A 组 大鼠伤侧后肢BBB 运动功能评分及斜板维持最大角度值显著低于B 组和C 组( P ＜ 0. 05) ,而这些指标在B 组和C 组之间没有明显差异; 术后28 d HE 和MRI 检测显示脊髓损伤区( A 组) 灰质和白质发生明显的形态学改变。结论 通过该方法建立的脊髓半切模型稳定、可靠,适于脊髓空洞性损伤的研究。     

脑运动神经系统的非线性建模与辨识

针对大脑运动皮层群体神经元信号与运动轨迹关系的辨识,分别建立了基于人工神经网络(ANN)和基于最小二乘支持向量机(LS-SVM)的非线性具有外部输入的自回归NARX模型.在三维虚拟空间中对猴子手臂运动实验记录的多通道神经元信号进行分析,通过与线性ARX模型的比较,说明非线性模型比线性模型能够更好地描述脑运动神经系统,并且用最小二乘支持向量机建立的模型比人工神经网络建立模型的预测精度更高,泛化能力更强,适用于大脑皮层神经元信号的分析,有利于实现性能更高的脑机接口系统.     

中华大蟾蜍胚后原始大脑皮层神经元自发电活动的发育变化

应用微电极电生理技术对中华大蟾蜍(Bufo bufo gargarizans)胚后端脑原始大脑皮层神经元的自发放电活动进行在体胞外记录,探讨其胚后端脑原始大脑皮层神经元自发电活的电生理学特性的发育变化。结果表明原始大脑皮层神经元的自发放电有5种形式。胚后发育的早期为4种放电类型,以簇状放电和连续放电为主;胚后发育的后期为5种放电类型,以簇状和连续簇状放电为主。随着原始大脑皮层的发育,单个放电的动作电位时程缩短,连续单个放电和连续簇状放电频率降低,连续放电、簇状放电和连续簇状放电的持续时间延长。随着端脑原始大脑皮层的发育,神经元的兴奋性逐步提高,神经元电活动形式逐渐呈现多样化。     

Complexin蛋白通过C端序列加速突触形成

为探究complexin对小鼠大脑皮层神经元生长的影响,将过表达的complexin及突变体导入小鼠大脑皮层神经元.利用共聚焦显微镜对神经元进行免疫荧光成像并利用Image J对突触的密度及平均大小进行分析.结果表明:过表达complexin后,突触密度上升而平均大小无明显变化;去除complexin的C末端后,能明显抑制由其带来的突触密度上升,但去除N末端却没有相同的效果;改变complexin的定位与过表达complexin的作用相同.说明complexin能促进小鼠大脑皮层神经元的生长,这种功能可能来自于它的C末端本身,与complexin的定位无关.     

野木瓜注射液及其提取物对脊髓神经元的氧化保护和生长促进

研究野木瓜注射液(IS)及其提取物(AI)对氧化损伤脊髓神经元的保护和对未损伤脊髓神经元生长的影响.方法:通过MTT法和细胞外液LDH漏出量的测定检测IS对未损伤的脊髓神经元细胞存活率的影响;建立H2O2氧化损伤模型,通过MTT法、胞内SOD活力和细胞外液LDH漏出量的测定研究IS对H2O2氧化损伤脊髓神经元的细胞保护作用;运用激光共聚焦显微镜研究氧化受损及IS保护对脊髓神经元胞浆内Ca2+浓度变化的影响.结果表明:当浓度为100～200 mg/L时,IS能显著地促进离体培养的小鼠脊髓神经元氧化受损的修复,神经元存活率得到显著的提高,胞内SOD活力显著地增加和LDH漏出量显著地减少,同时胞内Ca2+超载显著地被抑制;未受损的脊髓神经元在200 mg/L IS作用下LDH漏出量显著地减少,细胞存活率显著地提高;AI3对能显著地提高氧化受损脊髓神经元的存活率.     

川芎嗪对缺氧缺糖损伤大脑皮层神经元的保护作用及初步机制研究

目的:研究川芎嗪(TMP)对缺氧缺糖(OGD)损伤大脑皮层神经元的保护作用,探讨TMP神经保护作用的可能机制.方法:建立体外原代大脑皮层神经元OGD模型,利用MTT法和LDH试剂盒分别检测细胞存活率及细胞毒性;Hoechst染色法检测细胞凋亡;流式细胞仪检测细胞内ROS的含量;实时-PCR检测细胞内线粒体生物合成相关mRAN(PGC-1α,TFAM)的表达量.结果:经OGD损伤4 h后,细胞活力明显下降,细胞释放的LDH含量升高;细胞凋亡形态学特征明显,细胞凋亡率增加;细胞内ROS含量增加,同时PGC-1α和TFAM mRNA的表达量明显减少.TMP预保护后,可以明显提高OGD损伤后细胞的存活率,降低LDH的释放,改善细胞核形态变化,并且减少细胞凋亡率,抑制细胞内ROS的产生,提高PGC-1α和TFAM的表达.结论:TMP对OGD损伤的神经元具有神经保护作用,其机制可能与抗氧化,抗凋亡和增加线粒体生物合成相关因子(PGC-1α,TFAM)的表达有关.     

5-HT在青年和老年猫腰髓中分布的比较研究

用免疫组织化学方法观察了5-HT(5-羟色胺)在青年猫与老年猫腰髓中的表达,比较其表达的差异性,探讨该差异的原因及可能的生理影响.在青年猫与老年猫L6段脊髓灰质中,5-HT能神经元与神经纤维分布广泛,多个Rexed板层均可见5-HT阳性神经元,主要分布于RexedⅠ、Ⅱ、Ⅶ、Ⅸ区.5-HT能神经纤维阳性较强的区域有RexedⅠ、Ⅱ区及RexedⅦ、Ⅷ区.RexedⅩ区未见阳性标记.经比较,老年组腰髓中5-HT能神经元的数量及免疫反应性均明显低于青年组.表明猫腰髓中的5-HT表达有明显的年龄相关变化,该变化与脊髓中5-HT的合成、重摄取及代谢分解功能的变化有关,可能对脊髓水平伤害性信息的调制有重要影响.     

Cortical ensemble activity increasingly predicts behaviour outcomes during learning of a motor task

When an animal learns to make movements in response to different stimuli, changes in activity in the motor cortex seem to accompany and underlie this learning. The precise nature of modifications in cortical motor areas during the initial stages of motor learning, however, is largely unknown. Here we address this issue by chronically recording from neuronal ensembles located in the rat motor cortex, throughout the period required for rats to learn a reaction-time task. Motor learning was demonstrated by a decrease in the variance of the rats' reaction times and an increase in the time the animals were able to wait for a trigger stimulus. These behavioural changes were correlated with a significant increase in our ability to predict the correct or incorrect outcome of single trials based on three measures of neuronal ensemble activity: average firing rate, temporal patterns of firing, and correlated firing. This increase in prediction indicates that an association between sensory cues and movement emerged in the motor cortex as the task was learned. Such modifications in cortical ensemble activity may be critical for the initial learning of motor tasks.     

Receptive field dynamics in adult primary visual cortex.

The adult brain has a remarkable ability to adjust to changes in sensory input. Removal of afferent input to the somatosensory, auditory, motor or visual cortex results in a marked change of cortical topography. Changes in sensory activity can, over a period of months, alter receptive field size and cortical topography. Here we remove visual input by focal binocular retinal lesions and record from the same cortical sites before and within minutes after making the lesion and find immediate striking increases in receptive field size for cortical cells with receptive fields near the edge of the retinal scotoma. After a few months even the cortical areas that were initially silenced by the lesion recover visual activity, representing retinotopic loci surrounding the lesion. At the level of the lateral geniculate nucleus, which provides the visual input to the striate cortex, a large silent region remains. Furthermore, anatomical studies show that the spread of geniculocortical afferents is insufficient to account for the cortical recovery. The results indicate that the topographic reorganization within the cortex was largely due to synaptic changes intrinsic to the cortex, perhaps through the plexus of long-range horizontal connections.     

Neuroscience: rewiring the adult brain

Any analysis of plastic reorganization at a neuronal locus needs a veridical measure of changes in the functional output--that is, spiking responses of the neurons in question. In a study of the effect of retinal lesions on adult primary visual cortex (V1), Smirnakis et al. propose that there is no cortical reorganization. Their results are based, however, on BOLD (blood-oxygen-level-dependent) fMRI (functional magnetic resonance imaging), which provides an unreliable gauge of spiking activity. We therefore question their criterion for lack of plasticity, particularly in the light of the large body of earlier work that demonstrates cortical plasticity.     

Long-term motor cortex plasticity induced by an electronic neural implant

It has been proposed that the efficacy of neuronal connections is strengthened when there is a persistent causal relationship between presynaptic and postsynaptic activity. Such activity-dependent plasticity may underlie the reorganization of cortical representations during learning, although direct in vivo evidence is lacking. Here we show that stable reorganization of motor output can be induced by an artificial connection between two sites in the motor cortex of freely behaving primates. An autonomously operating electronic implant used action potentials recorded on one electrode to trigger electrical stimuli delivered at another location. Over one or more days of continuous operation, the output evoked from the recording site shifted to resemble the output from the corresponding stimulation site, in a manner consistent with the potentiation of synaptic connections between the artificially synchronized populations of neurons. Changes persisted in some cases for more than one week, whereas the output from sites not incorporated in the connection was unaffected. This method for inducing functional reorganization in vivo by using physiologically derived stimulus trains may have practical application in neurorehabilitation after injury.     

Real-time prediction of hand trajectory by ensembles of cortical neurons in primates

Signals derived from the rat motor cortex can be used for controlling one-dimensional movements of a robot arm. It remains unknown, however, whether real-time processing of cortical signals can be employed to reproduce, in a robotic device, the kind of complex arm movements used by primates to reach objects in space. Here we recorded the simultaneous activity of large populations of neurons, distributed in the premotor, primary motor and posterior parietal cortical areas, as non-human primates performed two distinct motor tasks. Accurate real-time predictions of one- and three-dimensional arm movement trajectories were obtained by applying both linear and nonlinear algorithms to cortical neuronal ensemble activity recorded from each animal. In addition, cortically derived signals were successfully used for real-time control of robotic devices, both locally and through the Internet. These results suggest that long-term control of complex prosthetic robot arm movements can be achieved by simple real-time transformations of neuronal population signals derived from multiple cortical areas in primates.     

Functional imaging with cellular resolution reveals precise micro-architecture in visual cortex

Neurons in the cerebral cortex are organized into anatomical columns, with ensembles of cells arranged from the surface to the white matter. Within a column, neurons often share functional properties, such as selectivity for stimulus orientation; columns with distinct properties, such as different preferred orientations, tile the cortical surface in orderly patterns. This functional architecture was discovered with the relatively sparse sampling of microelectrode recordings. Optical imaging of membrane voltage or metabolic activity elucidated the overall geometry of functional maps, but is averaged over many cells (resolution >100 microm). Consequently, the purity of functional domains and the precision of the borders between them could not be resolved. Here, we labelled thousands of neurons of the visual cortex with a calcium-sensitive indicator in vivo. We then imaged the activity of neuronal populations at single-cell resolution with two-photon microscopy up to a depth of 400 microm. In rat primary visual cortex, neurons had robust orientation selectivity but there was no discernible local structure; neighbouring neurons often responded to different orientations. In area 18 of cat visual cortex, functional maps were organized at a fine scale. Neurons with opposite preferences for stimulus direction were segregated with extraordinary spatial precision in three dimensions, with columnar borders one to two cells wide. These results indicate that cortical maps can be built with single-cell precision.     

Optical imaging of epileptiform and functional activity in human cerebral cortex.

Optical imaging of animal somatosensory, olfactory and visual cortices has revealed maps of functional activity. In non-human primates, high-resolution maps of the visual cortex have been obtained using only an intrinsic reflection signal. Although the time course of the signal is slower than membrane potential changes, the maximum optical changes correspond to the maximal neuronal activity. The intrinsic optical signal may represent the flow of ionic currents, oxygen delivery, changes in blood volume, potassium accumulation or glial swelling. Here we use similar techniques to obtain maps from human cortex during stimulation-evoked epileptiform afterdischarges and cognitively evoked functional activity. Optical changes increased in magnitude as the intensity and duration of the afterdischarges increased. In areas surrounding the afterdischarge activity, optical changes were in the opposite direction and possibly represent an inhibitory surround. Large optical changes were found in the sensory cortex during tongue movement and in Broca's and Wernicke's language areas during naming exercises. The adaptation of high-resolution optical imaging for use on human cortex provides a new technique for investigation of the organization of the sensory and motor cortices, language, and other cognitive processes.     

Early motor activity drives spindle bursts in the developing somatosensory cortex

Sensorimotor coordination emerges early in development. The maturation period is characterized by the establishment of somatotopic cortical maps, the emergence of long-range cortical connections, heightened experience-dependent plasticity and spontaneous uncoordinated skeletal movement. How these various processes cooperate to allow the somatosensory system to form a three-dimensional representation of the body is not known. In the visual system, interactions between spontaneous network patterns and afferent activity have been suggested to be vital for normal development. Although several intrinsic cortical patterns of correlated neuronal activity have been described in developing somatosensory cortex in vitro, the in vivo patterns in the critical developmental period and the influence of physiological sensory inputs on these patterns remain unknown. We report here that in the intact somatosensory cortex of the newborn rat in vivo, spatially confined spindle bursts represent the first and only organized network pattern. The localized spindles are selectively triggered in a somatotopic manner by spontaneous muscle twitches, motor patterns analogous to human fetal movements. We suggest that the interaction between movement-triggered sensory feedback signals and self-organized spindle oscillations shapes the formation of cortical connections required for sensorimotor coordination.     

Sensory experience modifies the short-term dynamics of neocortical synapses.

Many representations of sensory stimuli in the neocortex are arranged as topographic maps. These cortical maps are not fixed, but show experience-dependent plasticity. For instance, sensory deprivation causes the cortical area representing the deprived sensory input to shrink, and neighbouring spared representations to enlarge, in somatosensory, auditory or visual cortex. In adolescent and adult animals, changes in cortical maps are most noticeable in the supragranular layers at the junction of deprived and spared cortex. However, the cellular mechanisms of this experience-dependent plasticity are unclear. Long-term potentiation and depression have been implicated, but have not been proven to be necessary or sufficient for cortical map reorganization. Short-term synaptic dynamics have not been considered. We developed a brain slice preparation involving rat whisker barrel cortex in vitro. Here we report that sensory deprivation alters short-term synaptic dynamics in both vertical and horizontal excitatory pathways within the supragranular cortex. Moreover, modifications of horizontal pathways amplify changes in the vertical inputs. Our findings help to explain the functional cortical reorganization that follows persistent changes of sensory experience.     

Time-dependent reorganization of brain circuitry underlying long-term memory storage.

Retrograde amnesia observed following hippocampal lesions in humans and animals is typically temporally graded, with recent memory being impaired while remote memories remain intact, indicating that the hippocampal formation has a time-limited role in memory storage. However, this claim remains controversial because studies involving hippocampal lesions tell us nothing about the contribution of the hippocampus to memory storage if this region was present at the time of memory retrieval. We therefore used non-invasive functional brain imaging using (14C)2-deoxyglucose uptake to examine how the brain circuitry underlying long-term memory storage is reorganized over time in an intact brain. Regional metabolic activity in the brain was mapped in mice tested at different times for retention of a spatial discrimination task. Here we report that increasing the retention interval from 5 days to 25 days resulted in both decreased hippocampal metabolic activity during retention testing and a loss of correlation between hippocampal metabolic activity and memory performance. Concomitantly, a recruitment of certain cortical areas was observed. These results indicate that there is a time-dependent reorganization of the neuronal circuitry underlying long-term memory storage, in which a transitory interaction between the hippocampal formation and the neocortex would mediate the establishment of long-lived cortical memory representations.