虚拟视觉刺激引起幼年斑马鱼捕食行为放弃的研究

目的 当动物重复某种行为以逃避危险或获取奖励而无法成功时，会产生放弃。放弃是一种常见且基本的行为，在小鼠等模式动物中已经被广泛研究，但是其部分神经机制仍未被阐明。幼年斑马鱼适合进行全脑光学成像，是神经科学领域的重要模式生物。已经有研究者通过持续电击等消极刺激诱发斑马鱼放弃行为，然而奖励刺激能否引起斑马鱼放弃尚无报道。本文对奖励刺激引起的斑马鱼放弃行为进行了探究。方法 通过给予斑马鱼虚拟的食物视觉刺激，检验斑马鱼对虚拟食物的捕食情况，比较斑马鱼捕食频率和单次捕食时长随时间的变化。结果 虚拟的食物视觉刺激可以引起斑马鱼的捕食行为，接受25 min虚拟刺激后，8日龄以上斑马鱼的捕食频率和单次捕食时长均出现显著下降。结论 此研究丰富了斑马鱼放弃行为的研究范式，实验结果表明，缺失真实奖励的虚拟食物刺激可以诱导斑马鱼放弃捕食行为，这将进一步加深对动物放弃行为的理解，推动对其神经机制的研究。     

揭秘大脑里的“开关”

动物对不同的感觉刺激产生不同的行为反应,这对动物生存至关重要。关于其神经机制的研究,之前的工作多集中在感觉系统信息处理方面。但视觉刺激所包含的行为意义是怎样被大脑处理的,大脑处理后又如何根据刺激的行为意义调控行为的发生尚不清楚。为了更好地解析行为选择的神经机制,中国科学院神经科学研究所杜久林组姚园园等利用斑马鱼的逃跑环路为模型,研究了不同行为意义的视觉刺激引起不同行为反应的神经机制。首先,他们发现斑马鱼仅对危险性而非非危险性视觉刺激产生逃跑行为,且这一行为控制发生在视觉信息由视觉中枢向逃跑命令神经元传递的阶段(即视觉-运动信息转换阶段)。其次,发现下丘脑多巴胺能神经元和后脑甘氨酸能抑制性神经元组成"开关"样功能模块控制这一行为选择。进而,他们发现这一"开关"样功能模块对危险性和非危险性视觉刺激的不同控制是由这些神经元的视觉反应特性实现的。这一工作揭示了神经调质系统在行为选择中的作用,增加了人们对感觉–运动信息转换控制的认识。该工作发现的神经调质系统响应感觉刺激这一功能特点可能是大脑中一种普遍存在的神经机制,即神经调质系统接受和处理感觉刺激所携带的行为意义,进而通过调节感觉-运动神经通路,帮助动物作出相应的行为选择。这一工作为课题组提出的"Bi-modal Brain Function Hypothesis"提供了进一步的实验证据。     

采用GCaMP活体钙成像解析神经环路调控机制的研究策略及意义

大脑中的神经元通过集体行为建立相互连接,构成多种神经环路进而执行不同的功能。神经环路的研究方向即寻找构成各神经环路的神经元细胞,研究这些神经元是如何产生通讯互动以此构成特定的环路及环路本身在中枢神经系统行使的生命活动。众多研究已经证实,在解析生理或病理条件下神经环路调控机制过程中,通过实时监测神经元内重要生物传感器钙离子的变化可精确反映大脑组织内神经元活动。GCaMP活体钙成像方法有助于从单细胞水平揭示生理或病理状态下不同环路的调控机制。本文系统综述了GCaMP活体钙成像作为一种示踪技术在神经环路研究中的应用及进展,为神经环路和神经药理学的研究提供了参考依据。     

斑马鱼依托咪酯麻醉模型的建立北大核心CSCD

全身麻醉药广泛应用于临床,但其引起全身麻醉状态的神经机制至今仍不清楚。脊椎动物斑马鱼具有保守而简单的脑结构,近几年来已应用于神经机理基础性的研究。在本工作中,我们从行为和电生理水平上,首次建立了斑马鱼麻醉模型。在细胞外液中施加静脉麻醉药依托咪酯(etomidate),可以浓度依赖性地抑制斑马鱼的运动。在体细胞外电生理记录显示,依托咪酯可有效阻断斑马鱼脊髓运动神经元的电活动。运用在体局部场电位和全细胞记录技术,进一步发现依托咪酯可显著抑制大脑群体神经元的活动,并阻断视觉信号的传递。本工作表明,斑马鱼可以作为一种合适的动物模型,应用于全身麻醉药神经机制的研究。     

大脑神经联接图谱的研究进展

脑科学旨在阐明神经系统结构和功能,揭示大脑工作的神经机制.由于大脑中神经元数量庞大,神经元形态和功能种类多样,神经元之间的结构与功能联接错综复杂,使得研究脑工作原理尤具挑战.因而,在全脑尺度上绘制神经元之间的联接,即神经联接图谱,揭示大脑各脑区、核团、神经元之间的功能和结构联系,是全面理解脑工作原理的基础.近几年,多维度多模态成像、神经环路示踪与功能调控、图像处理等技术的进步,推动了神经联接图谱研究的迅速发展,使人们得以在局部脑区乃至全脑尺度上观察神经元的形态、联接与活动.本文总结近年来宏观、介观、微观脑神经联接图谱相关技术的进步和神经环路结构与功能研究的进展,对脑联接图谱研究领域面临的挑战与发展趋势加以探讨,并提出斑马鱼(Danio rerio)是目前在全脑尺度上阐释脑结构和功能神经联接图谱的理想动物模型.     

脊髓损伤后神经环路重建的研究进展

成年哺乳类脊髓损伤后的修复与再生是一项复杂且尚未解决的挑战.随着全球经济的增长,脊髓损伤的发生率呈上升趋势.脊髓损伤可能导致永久性的运动功能障碍和感觉丧失,给患者及其家属带来极大的经济压力和心理负担.因此,迫切需要开发有效的治疗脊髓损伤的新策略.近年来,应用外源性或内源性神经元中继的治疗手段为脊髓损伤后环路重建提供了新的思路.将干细胞或生物材料等移植物作用于脊髓损伤区,可改善损伤区局部微环境,诱导神经干细胞定向分化为神经元,促进脊髓环路重建和功能恢复,因此成为较有临床应用前景的方法.本综述主要介绍细胞移植治疗、组织工程策略和基因调控等方法在修复受损脊髓的神经网络中的应用,并讨论了脊髓损伤后新生神经元是否具有潜在的功能整合,重建受损神经环路,并恢复其运动和感觉功能等问题.     

斑马鱼依托咪酯麻醉模型的建立

全身麻醉药广泛应用于临床,但其引起全身麻醉状态的神经机制至今仍不清楚。脊椎动物斑马鱼具有保守而简单的脑结构,近几年来已应用于神经机理基础性的研究。在本工作中,我们从行为和电生理水平上,首次建立了斑马鱼麻醉模型。在细胞外液中施加静脉麻醉药依托咪酯(etomidate),可以浓度依赖性地抑制斑马鱼的运动。在体细胞外电生理记录显示,依托咪酯可有效阻断斑马鱼脊髓运动神经元的电活动。运用在体局部场电位和全细胞记录技术,进一步发现依托咪酯可显著抑制大脑群体神经元的活动,并阻断视觉信号的传递。本工作表明,斑马鱼可以作为一种合适的动物模型,应用于全身麻醉药神经机制的研究。     

以透明脑,观澄明心——斑马鱼神经功能研究进展

斑马鱼是一种相对新颖的模式脊椎动物,具有脊椎动物保守的神经系统构造和丰富的行为模式.近年来随着在体电生理、光学成像、遗传工程等方法的建立和完善,幼龄斑马鱼因其脑部透明、结构简单的特点,日益成为从突触、神经元、环路到行为等多层次,在全脑尺度上探究神经系统功能机制的理想动物模型.本文综述了近年来利用斑马鱼在感觉信息处理、运动控制、学习与神经可塑性等方向上所取得的重要研究进展,并对新技术的开发提出了展望.随着研究思路的深化和实验手段的推陈出新,斑马鱼模式动物必将成为探索脑工作原理之利器,为神经科学研究带来更多的突破.     

痒觉的中枢环路机制

痒觉是一种诱发抓挠行为的不愉快的感受。近年来,我们对痒觉信息在脊髓水平处理的分子和细胞机制已经有了较为深入的认识。然而,痒觉信息如何从脊髓传递到大脑并不清楚。我们发现,在痒觉诱发抓挠的过程中,脊髓中投射到臂旁核的神经元被激活,光遗传学抑制这条环路的活性可以减少痒觉诱发的抓挠行为。脊髓中痒觉特异的胃泌素释放肽受体阳性神经元与投射到臂旁核的脊髓投射神经元形成兴奋性突触连接。我们进一步研究了臂旁核在痒觉行为过程中的活性变化和功能。我们发现,臂旁核神经元的兴奋性与痒觉诱发的抓挠过程具有很强的相关性。整体抑制臂旁核神经元的活性或者选择性阻断兴奋性神经元的突触传递可以显著降低急性痒引起的抓挠行为,并减缓慢性痒模型的建立。我们的工作揭示了痒觉从脊髓传递到大脑的一条重要环路,并且提示臂旁核是参与痒觉信息处理的重要脑区。该研究为深入阐明痒觉信息加工的脑内环路机制提供了重要基础。     

脑成像与脑网络

揭示脑的奥秘是人类面临的最大挑战之一。神经元是构成神经系统结构与功能的基本单位。神经元与神经元之间通过突触实现信息交互,并构成神经环路或神经网络。神经环路有局部的,也有跨脑区或长程的,甚至全脑尺度的。神经环路则是脑实现神经信息处理的基本单元。若干神经环路构成脑网络。脑网络研究已经成为脑功能与脑疾病研究领域的热点。     

From neuron to behavior: Sensory‐motor coordination of zebrafish turning behavior

Recent development of optogenetics brought non‐invasive neural activation in living organisms. Transparent zebrafish larva is one of the suitable animal models for this technique, which enables us to investigate neural circuits for behaviors based on a whole individual nervous system. In this article we review our recent finding that suggests sensory‐motor coordination in larval zebrafish escape behavior. When water vibration stimulates mechanosensory Rohon‐Beard (RB) neurons, intra‐spinal reflex circuit launches contralateral trunk muscle contraction that makes rapid body curvature for turning. In addition, positional information of the stimulus is conveyed to supra‐spinal circuits, and then regulates the curvature strength for appropriate escape pathway from the threat. Sensory‐motor coordination is a fundamental feature to adapt behaviors to environment, and zebrafish larvae would be an excellent model for elucidating its neural backbones.     

Neural circuit models for computations in early visual cortex

Some cortical circuit models study the mechanisms of the transforms from visual inputs to neural responses. They model neural properties such as feature tunings, pattern sensitivities, and how they depend on intracortical connections and contextual inputs. Other cortical circuit models are more concerned with computational goals of the transform from visual inputs to neural responses, or the roles of the neural responses in the visual behavior. The appropriate complexity of a cortical circuit model depends on the question asked. Modeling neural circuits of many interacting hypercolumns is a necessary challenge, which is providing insights to cortical computations, such as visual saliency computation, and linking physiology with global visual cognitive behavior such as bottom-up attentional selection.     

趋流行为下斑马鱼幼鱼的全脑成像

目的 趋流,意即在水中调整身体方向并逆流而上的能力,是一种在大多数鱼类与两栖类动物中存在的保守行为。虽然关于趋流的研究已有一段很长的历史,并且近年来斑马鱼幼鱼趋流行为的理论机制也被提出,但是分布式的神经环路是如何整合多感知信息、做出决策、并实现行为控制仍然是个未知数。对自由运动的斑马鱼进行全脑神经活动成像为理解这一困难的问题提供了特殊的机会。方法 本文开发了一种微流控装置精确控制环境水流并激发斑马鱼的趋流行为。将该微流控芯片与扩增视野光场显微镜以及追踪系统整合,从而记录自由行为下斑马鱼全脑的神经活动。结果 在整合的微流控装置中稳定观察到了斑马鱼在水流中保持自身位置不变、逆流而上等刻板的趋流行为现象。与此同时,实现了对斑马鱼幼鱼趋流行为过程中的全脑钙活动记录。本文初步发现了几个脑区的神经活动与趋流行为相关。结论 本研究第一次展示了在斑马鱼幼鱼趋流行为的同时记录全脑神经活动的技术。接下来对神经活动和行为数据的分析与建模将有助于更好地理解一种重要自然行为背后的感觉运动转换机制。     

Transgenic technology for visualization and manipulation of the neural circuits controlling behavior in zebrafish

The vertebrate brain is innately equipped with neural circuits that make quick behavioral decisions possible. Elucidating these neural circuits, determining how their master plans are encoded in the genome, and revealing how they can be modified by postnatal experiences will facilitate our understanding of how nature and nurture interact to establish an animal's behavior. In this review, we explain how transgenic zebrafish can cast insights into the developmental mechanisms and functional roles of the neural circuits that directly and indirectly control visuomotor behavior, by taking as an example a transgenic line Tg( brn3a-hsp70:GFP ) enabling visualization of the tectobulbar and habenulo-interpeduncular tracts. These insights emphasize the benefits of applying advanced transgenic technology in zebrafish to future research into this area.     

Eye movements and target fixation during dragonfly prey-interception flights

The capture of flying insects by foraging dragonflies is a highly accurate, visually guided behavior. Rather than simply aiming at the prey’s position, the dragonfly aims at a point in front of the prey, so that the prey is intercepted with a relatively straight flight trajectory. To better understand the neural mechanisms underlying this behavior, we used high-speed video to quantify the head and body orientation of dragonflies (female Erythemis simplicicollis flying in an outdoor flight cage) relative to an artificial prey object before and during pursuit. The results of our frame-by-frame analysis showed that during prey pursuit, the dragonfly adjusts its head orientation to maintain the image of the prey centered on the “crosshairs” formed by the visual midline and the dorsal fovea, a high acuity streak that crosses midline at right angles about 60° above the horizon. The visual response latencies to drifting of the prey image are remarkably short, ca. 25 ms for the head and 30 ms for the wing responses. Our results imply that the control of the prey-interception flight must include a neural pathway that takes head position into account.     

Behavioral genetics in larval zebrafish: learning from the young

Deciphering the genetic code that determines how the vertebrate nervous system assembles into neural circuits that ultimately control behavior is a fascinating and challenging question in modern neurobiology. Because of the complexity of this problem, successful strategies require a simple yet focused experimental approach without limiting the scope of the discovery. Unbiased, large-scale forward genetic screens in invertebrate organisms have yielded great insight into the genetic regulation of neural circuit assembly and function. For many reasons, this highly successful approach has been difficult to recapitulate in the behavioral neuroscience field's classic vertebrate model organisms-rodents. Here, we discuss how larval zebrafish provide a promising model system to which we can apply the design of invertebrate behavior-based screens to reveal the genetic mechanisms critical for neural circuit assembly and function in vertebrates.     

Activity-induced long-term potentiation of excitatory synapses in developing zebrafish retina in vivo

Neural activity-induced long-term potentiation (LTP) of synaptic transmission is believed to be one of the cellular mechanisms underlying experience-dependent developmental refinement of neural circuits. Although it is well established that visual experience and neural activity are critical for the refinement of retinal circuits, whether and how LTP occurs in the retina remain unknown. Using in?vivo perforated whole-cell recording and two-photon calcium imaging, we find that both repeated electrical and visual stimulations can induce LTP at excitatory synapses formed by bipolar cells on retinal ganglion cells in larval but not juvenile zebrafish. LTP induction requires the activation of postsynaptic N-methyl-D-aspartate receptors, and its expression involves arachidonic acid-dependent presynaptic changes in calcium dynamics and neurotransmitter release. Physiologically, both electrical and visual stimulation-induced LTP can enhance visual responses of retinal ganglion cells. Thus, LTP exists in developing retinae with a presynaptic locus and may serve for visual experience-dependent refinement of retinal circuits.     

Neurogenetics and the "fly-stampede": dissecting neural circuits involved in visual behaviors

A central goal of systems neuroscience is to understand how neural circuits represent quantitative aspects of the outside world and transform these signals into the motor code for behavior. By contrast to olfactory perception in which odors are encoded by a population of ligand-binding receptors at the input stage, the visual system extracts complex information about color, form and movement from just a few types of photoreceptor inputs. The algorithms for many of these transformations are poorly understood. We designed a high throughput real-time quantitative testing system, the "fly-stampede", to evaluate behavioral responses to light and motion cues in Drosophila. With this system, we identified a neural circuit that does not participate in sensing light but is crucial for computing visual motion. When neurons of this circuit are genetically inactivated, the flies show normal walking phototaxis, but are completely motion blind. Using neurogenetics to study the circuits mediating sophisticated animal behaviors is currently a field of intense study. This extra view attempts to summarize our work within historical background of fly biocybernetics and other recent advances.