家鸽前脑声反应神经元的分布及其特性的研究

实验在61只家鸽上完成。动物用三碘季胺酚麻痹,记录了前脑36个神经元的电活动。实验结果表明,对短声刺激具有反应的前脑神经元分散地分布在旧纹状体、上纹状体以及新纹状体内,但是大多数听神经元集聚在相当于Karten和Hodos氏鸽脑立体定位图谱P_(1-3),L或R_(1-3)以及H_(2-6)的坐标范围之内。这些对声刺激有反应的听神经元的潜伏期为5～42msec。在正常情况下,神经元的潜伏期很少变化。前脑听神经元既可以接受对侧耳的信息,也可以接受同侧耳的信息。在旧纹状体内来自双耳信息的聚合可能引起相互抑制的结果。     

尼古丁剂量依赖性降低大鼠纹状体内多巴胺的释放

利用碳纤维电极在体(invivo)恒压伏安法检测大鼠纹状体(CPu)内由电刺激前脑内侧束(mfb)所引起的DA释放,探讨急性腹腔注射尼古丁对纹状体内多巴胺(DA)动态释放的影响.结果发现,尼古丁可导致CPu内的DA刺激-释放呈剂量依赖性降低,其中0.6mg/kg的尼古丁可明显降低DA的释放量,与生理盐水组相比差异显著.     

鸽上纹状体神经元对桡神经和坐骨神经传入冲动的反应

在61只家鸽上纹状体中,用玻璃微电极共记录到138个对电刺激桡神经和坐骨神经发生反应的单位.根据诱发反应放电型式,可分为三类:①单个或短串放电反应.②长串放电反应.③抑制性反应.其中①类细胞有116个.上纹状体神经元对躯体神经刺激反应的潜伏期差异较大,多数桡神经传入的诱发反应具有长潜伏期特征.结合解剖学资料对潜伏期差异的原因进行了讨论.认为,短潜伏期反应可能是由DIVA-Wulst通路直接传入引起,长潜伏期反应可能是经DLP-NI/NC-Wulst通路间接传入引起.     

前额叶皮层和纹状体间功能性连接的量化分析

奖励预测对于大脑的学习记忆、行为决策等高级认知功能具有至关重要的意义。前额叶皮层(Prefrontal Cortex,PFC)和纹状体(Striatum)是大脑中的两个重要脑区,以往的研究发现,前额叶皮层和纹状体中的神经元都参与了对奖励信息的编码,然而,对于这两个脑区之间信息交流、相互影响的具体方式仍然不够明确。为了研究这一问题,在对猴子进行非对称奖励预测实验的过程中,用多通道电极同时记录了其前额叶皮层和纹状体两个部位的局域场电位(Local Field Potentials, LFP)信号。通过计算非线性相互依赖性(Nonlinear Interdependence,NLI)来量化分析前额叶皮层和纹状体之间功能性连接的强度。结果显示,在β频段(15～30 Hz),小水奖励条件下前额叶皮层和纹状体间的功能性连接强度显著高于大水奖励条件下的结果,同时,前额叶皮层和纹状体间不同方向的连接强度也有显著差别。实验结果表明,前额叶皮层中LFP的β频段可能与纹状体神经元的活动有关,并在一定程度上调节猴子在奖励预测过程中的行为。     

刺激大鼠杏仁外侧核对听皮层神经元调频声反应的影响

采用在体细胞外单细胞记录方法,研究电刺激杏仁外侧核对调频声所诱发的听皮层神经元反应的影响.实验在34只乌拉坦麻醉的SD大鼠上进行,在皮层41区记录了113个对调频声有反应的细胞电活动.观察发现,这些神经元对调频声刺激的反应可分为ON反应,OFF反应,ON-OFF反应,持续性反应和给声抑制反应几种类型.在观察对其中42个神经元的声反应时给予了杏仁外侧核电刺激,其中22%的神经元反应被易化,48%的神经元反应受到了抑制,另外30%神经元的声反应未受杏仁外侧核刺激的影响.这些影响进一步表明,杏仁复合体可在皮层水平参与听觉上传信息的处理,包括听觉信息的加工与整合.同时也表明杏仁核在上传听觉信息的筛选中可能具有重要的作用.     

6-羟基多巴胺所致急性帕金森病大鼠模型的复制

采用6-羟基多巴胺(6-OHDA)纹状体内注射法制作急性帕金森病大鼠模型,为抗帕金森病药物的快速药效学研究提供新的方法.方法10只大鼠随机分为对照组和模型组.给对照组大鼠脑纹状体内注射等量生理盐水、模型组同一部位注射6-OHDA 4μL(12μg/4μL)制作大鼠多巴胺(DA)能神经元损伤的急性模型,术后第7d进行微透析试验,将透析液注入高效液相一电化学检测器(HPLC-ECD)测定各组纹状体细胞外液中DA、3,4-二羟基苯乙酸(DOPA C)和高香草酸(HVA)的含量.结果与对照组相比,模型组动物纹状体细胞外液中DA、DOPAC和 HVA含量均显著性降低,具有统计学差异(P<0.05,P<0.01或P<0.001).采用6-OHDA纹状体内注射法可以复制急性帕金森病大鼠模型.     

鼠耳蝠下丘听神经元对超声刺激的反应特性

实验在５只鼠耳蜗上进行，共观察了２２７个对超声刺激发生反应的下丘听神经元。这些神经元听反应的最佳频率在１４．３－７６．２ｋＨｚ之间；潜伏期在３．０－１２．０毫秒之间，多数神经元（７９．３％）为５．０－７．０毫秒；最低阈值位于－２０．０－７０．０ｄＢ ＳＰＬ之间；多数神经元（８２．０５％）的调谐曲线为宽阔型，少数（１７．９５％）为狭窄型；反应最佳频率沿下丘背腹轴呈明显有序地排列。     

刺激扣带皮层前部对大鼠初级体感皮层神经元诱发放电活动的影响

用细胞外记录单位放电的方法观察了刺激大鼠扣带皮层前部(ACC)对初级体感皮层(Sm．Ⅰ)接受触压觉传入神经元诱发放电的影响，神经元的鉴别方法是外周神经碰撞试验和自然触压觉刺激验证，在所鉴别的45个神经元中，14个神经元的诱发放电受到了易化性影响，9个神经元的诱发放电受到了抑制性影响，扣带皮层前部影响的潜伏期为6～25ms，作用时程为50～150ms，上述结果提示，扣带皮层前部在皮层触压觉信息的整合中具有一定作用。     

鸣禽鸣啭控制核团内GABA能神经元的分布研究

应用免疫组化方法对鸣禽粟鹀(Emberiza rutila)鸣啭控制核团内GABA能神经元的分布进行了研究，在高级发声中枢(HVC，high vocal center)，古纹状体粗核(RA，the robust nucleus of the archistrialum)，X区(Arca X)3个前脑核团内有GABA样免疫反应出现．HVC和RA中GABA能神经元胞体大小存在性别和季节间的差异．结果提示GABA能神经元可能参与了鸣禽鸣啭的产生和鸣啭学习。     

兔内膝体神经元声反应的观察

实验在10只三碘季胺酚麻痹的新西兰兔上进行.采用记录单个神经元放电的方法,观察了短纯音引起的内膝体(MGB)神经元的声反应.实验结果表明:兔MGB神经元的声反应类型与猫、鼠等类似;并且声反应型式随纯音刺激频率、强度、时程的变化而变化.     

Sustained firing in auditory cortex evoked by preferred stimuli

It has been well documented that neurons in the auditory cortex of anaesthetized animals generally display transient responses to acoustic stimulation, and typically respond to a brief stimulus with one or fewer action potentials. The number of action potentials evoked by each stimulus usually does not increase with increasing stimulus duration. Such observations have long puzzled researchers across disciplines and raised serious questions regarding the role of the auditory cortex in encoding ongoing acoustic signals. Contrary to these long-held views, here we show that single neurons in both primary (area A1) and lateral belt areas of the auditory cortex of awake marmoset monkeys (Callithrix jacchus) are capable of firing in a sustained manner over a prolonged period of time, especially when they are driven by their preferred stimuli. In contrast, responses become more transient or phasic when auditory cortex neurons respond to non-preferred stimuli. These findings suggest that when the auditory cortex is stimulated by a sound, a particular population of neurons fire maximally throughout the duration of the sound. Responses of other, less optimally driven neurons fade away quickly after stimulus onset. This results in a selective representation of the sound across both neuronal population and time.     

Linear processing of spatial cues in primary auditory cortex.

To determine the direction of a sound source in space, animals must process a variety of auditory spatial cues, including interaural level and time differences, as well as changes in the sound spectrum caused by the direction-dependent filtering of sound by the outer ear. Behavioural deficits observed when primary auditory cortex (A1) is damaged have led to the widespread view that A1 may have an essential role in this complex computational task. Here we show, however, that the spatial selectivity exhibited by the large majority of A1 neurons is well predicted by a simple linear model, which assumes that neurons additively integrate sound levels in each frequency band and ear. The success of this linear model is surprising, given that computing sound source direction is a necessarily nonlinear operation. However, because linear operations preserve information, our results are consistent with the hypothesis that A1 may also form a gateway to higher, more specialized cortical areas.     

脑对双耳听觉信息整合的神经机制

综述近60 a来有关脑对双耳听觉信息整合的神经机制的研究进展.首先介绍了脑处理双耳信息的神经解剖学基础，双耳神经元的分类及其生理特性，以及双耳神经元在听觉系统的拓扑学分布研究；然后对脑处理双耳听觉信息研究的热点领域进行了重点探讨，综述了上橄榄复合体、下丘和听皮层双耳神经元对双耳时间差和双耳强度差的编码方式，以及脑通过对这些参数的编码来分析声源方位的神经生理学研究进展；最后对该领域未来研究方向作展望.     

Cortical remodelling induced by activity of ventral tegmental dopamine neurons.

Representations of sensory stimuli in the cerebral cortex can undergo progressive remodelling according to the behavioural importance of the stimuli. The cortex receives widespread projections from dopamine neurons in the ventral tegmental area (VTA), which are activated by new stimuli or unpredicted rewards, and are believed to provide a reinforcement signal for such learning-related cortical reorganization. In the primary auditory cortex (AI) dopamine release has been observed during auditory learning that remodels the sound-frequency representations. Furthermore, dopamine modulates long-term potentiation, a putative cellular mechanism underlying plasticity. Here we show that stimulating the VTA together with an auditory stimulus of a particular tone increases the cortical area and selectivity of the neural responses to that sound stimulus in AI. Conversely, the AI representations of nearby sound frequencies are selectively decreased. Strong, sharply tuned responses to the paired tones also emerge in a second cortical area, whereas the same stimuli evoke only poor or non-selective responses in this second cortical field in naive animals. In addition, we found that strong long-range coherence of neuronal discharge emerges between AI and this secondary auditory cortical area.     

Top-down gain control of the auditory space map by gaze control circuitry in the barn owl

High-level circuits in the brain that control the direction of gaze are intimately linked with the control of visual spatial attention. Immediately before an animal directs its gaze towards a stimulus, both psychophysical sensitivity to that visual stimulus and the responsiveness of high-order neurons in the cerebral cortex that represent the stimulus increase dramatically. Equivalent effects on behavioural sensitivity and neuronal responsiveness to visual stimuli result from focal electrical microstimulation of gaze control centres in monkeys. Whether the gaze control system modulates neuronal responsiveness in sensory modalities other than vision is unknown. Here we show that electrical microstimulation applied to gaze control circuitry in the forebrain of barn owls regulates the gain of midbrain auditory responses in an attention-like manner. When the forebrain circuit was activated, midbrain responses to auditory stimuli at the location encoded by the forebrain site were enhanced and spatial selectivity was sharpened. The same stimulation suppressed responses to auditory stimuli represented at other locations in the midbrain map. Such space-specific, top-down regulation of auditory responses by gaze control circuitry in the barn owl suggests that the central nervous system uses a common strategy for dynamically regulating sensory gain that applies across modalities, brain areas and classes of vertebrate species. This approach provides a path for discovering mechanisms that underlie top-down gain control in the central nervous system.     

A corollary discharge maintains auditory sensitivity during sound production

Speaking and singing present the auditory system of the caller with two fundamental problems: discriminating between self-generated and external auditory signals and preventing desensitization. In humans and many other vertebrates, auditory neurons in the brain are inhibited during vocalization but little is known about the nature of the inhibition. Here we show, using intracellular recordings of auditory neurons in the singing cricket, that presynaptic inhibition of auditory afferents and postsynaptic inhibition of an identified auditory interneuron occur in phase with the song pattern. Presynaptic and postsynaptic inhibition persist in a fictively singing, isolated cricket central nervous system and are therefore the result of a corollary discharge from the singing motor network. Mimicking inhibition in the interneuron by injecting hyperpolarizing current suppresses its spiking response to a 100-dB sound pressure level (SPL) acoustic stimulus and maintains its response to subsequent, quieter stimuli. Inhibition by the corollary discharge reduces the neural response to self-generated sound and protects the cricket's auditory pathway from self-induced desensitization.     

Precise auditory-vocal mirroring in neurons for learned vocal communication

Brain mechanisms for communication must establish a correspondence between sensory and motor codes used to represent the signal. One idea is that this correspondence is established at the level of single neurons that are active when the individual performs a particular gesture or observes a similar gesture performed by another individual. Although neurons that display a precise auditory-vocal correspondence could facilitate vocal communication, they have yet to be identified. Here we report that a certain class of neurons in the swamp sparrow forebrain displays a precise auditory-vocal correspondence. We show that these neurons respond in a temporally precise fashion to auditory presentation of certain note sequences in this songbird's repertoire and to similar note sequences in other birds' songs. These neurons display nearly identical patterns of activity when the bird sings the same sequence, and disrupting auditory feedback does not alter this singing-related activity, indicating it is motor in nature. Furthermore, these neurons innervate striatal structures important for song learning, raising the possibility that singing-related activity in these cells is compared to auditory feedback to guide vocal learning.