无尾两栖类蟾蜍和鸣禽锡嘴雀听觉中枢及其神经通赂的比较研究

本研究采用HRP示踪技术对无尾两栖类蟾蜍（Bufogargarizans）和鸣禽锡嘴雀（Ooccothraustescoccothraustes）从外周到听觉中枢的通路逐级进行了追踪比较研究.结果表明（1）无尾两栖类内耳囊听觉神经纤维上行投射到延髓同侧的背侧前庭核,它是听觉上行通路的第一级中枢,由此核中继后再投射到上橄榄核．以对侧为主;上橄榄核再发出纤维投射到中脑同侧的半环隆枕,后者是第三级中枢,此结果说明：无尾两栖类从外周到中脑听觉中枢的神经通路已较完整地形成;（2）鸣禽锡嘴雀的耳蜗听神经上行投射到听觉通路的第一级中队即延脑同侧的前庭外则核和角核,角核又发出纤维通过外侧丘系直接投射到对侧的中脑背外侧核．说明鸣禽鸟除了具备两栖类的听觉中枢及神经通路外．已进化形成独特的听觉神经通路即延脑的角核至中脑的背外侧核。     

锡嘴雀、家鸽发声控制核团的定位和比较

应用辣根过氧化物酶(HRP)逆行轴突示踪法,对鸣禽锡嘴雀、非鸣禽家鸽的发声控制核团,从外用至中枢,逐级进行了追踪定位,以确定鸟类发声控制神经通路。结果表明,鸣禽与非鸣禽中脑水平以下的发声控制核团相同,均由中脑丘间核经延髓中间核支配鸣肌;但前脑核团二者差异明显,鸣禽为上纹状体腹侧尾端和原纹状体粗核,非鸣禽为原纹状体腹侧。这种差异可能是造成不同鸟类鸣叫能力差异的结构基础。     

无尾两栖类蟾蜍和鸣禽锡嘴雀听觉中枢及其神经通路的比较研究

本研究采用ＨＲＰ示踪技术对无尾两栖类蟾蜍和鸣禽锡嘴雀从外周到听觉中枢的通路逐级进行了追踪比较研究。结果表明（１）无尾两栖类内耳囊听觉神经纤维上行投射到延髓同侧的背侧前庭核,它是听觉上行通路的第一级中枢,由此核中继后再投射到上橄榄核,     

鸣禽和无尾两栖类控制发声核团及神经通路的比较研究

为从种是化角度对鸣禽和无尾两栖类控制发声的核团和神经通路作比较研究，用ＨＲＰ顺、逆行追踪的方法，地锡嘴雀（Ｃｏｃｃｏｔｈｒａｕｓｔｅｓ）和蛙（Ｒａｎａ ｍｉｇｒｏｍａｌａｔａ，Ｒａｎａ ｃｈｅｎｓｉｎｅｎｅｎｉｓｉｓ）、蟾蜍（Ｂｕｆｏｇａｒｇａｒｉｚａｎｓ）控制发的神经核团及神经通路，从外周到至中枢逐级追踪比较研究，结果表明，Ｉ．鸣禽锡嘴雀中间核（ＩＭ）是鸣禽延髓中支配发重要实级运动神经核团，２．     

黄雀(carduelis spinus)耳蜗神经元至延髓耳蜗主核的投射——HRP法研究

将HRP溶液注入鸣禽黄雀的耳蜗内,顺行追踪了耳蜗神经元至延髓听觉核团的上行投射。①在同侧的听神经(NⅧ)有密集标记的神经纤维束并分别投射至延髓的巨细胞杉和角状核;②在巨细胞核和角状核出现大量密集的标记终末,表明:黄雀的耳蜗神经元发出的纤维组成听神经后分别投射至同侧的巨细胞核和角状核做为听觉通路的第一级换元站的延髓耳蜗主核只由此二亚核组成,延髓的层状核并不接受耳蜗纤维的直接投射。     

黄雀丘脑卵圆核的中枢联系—HRP法研究

<正> 我们最近的工作证实了黄雀(Carduelis Sipnus)中脑的听性核团投射至丘脑卵圆核(Nucleus ovoidalis,pars centralis,OV),提示OV可能是丘脑内的听觉中继核团。为了逐级追踪鸣禽类的听觉上行通路,我们用HRP顺、逆行示踪方法,研究了黄雀OV的中枢联系。选成年黄雀28只,麻醉后置鸟头定位仪上,通过微玻管将30%HRP(Sigma)溶液微电泳泳入OV。术后存活2天,按常规方法灌注固定,取脑作冰冻连续切片,片厚40μm,HRP     

黄喉鹀延髓听觉核团的定位研究

用HRP顺行轴突传递法研究鸣禽黄喉鵐的耳蜗神经元向延髓听觉核团的上行投射和定位.将HRP分别注入左右侧耳蜗内,1.在同侧听神经有束状的标记纤维并分别投射至延髓的角状核和巨细胞核;2.在角状核内有密集成簇的标记终末;3.在巨细胞核内有中等量的标记终末.结果表明:耳蜗纤维分别投射至巨细胞核和角状核,由这两对亚核组成延髓的耳蜗核,它是听觉上行通路中在脑内的第一级中继站,延髓的层状核并不接受耳蜗纤维的直接投射.     

鸽中脑半圆隆枕传出投射的研究

应用ＰＨＡ－Ｌ和Ｂｉｏｃｙｔｉｎ两种神经示踪物对非鸣禽环鸽（Ｓｔｒｅｐｔｏｐｅｌｉａｒｉｓｏｒｉａ）中脑半圆隆枕（ｔｏｒｕｓｓｅｍｉｃｉｒｃｕｌａｒｉｓ）的传出投射进行了分区研究。结果发现半圆隆枕丘间核内缘（ＩＣＭ）发出两束纤维分别向尾端投射至外侧丘系背核腹侧（ＬＬＤｖ）周围和向首端投射至丘脑卵形壳（Ｏｖ－ｓｈｅｌｌ）；丘间核（ＩＣｏ）发出的纤维直接投射至下丘脑前内侧核（ＡＭ）。从脑桥至听丘各级听神经核周围，均存在疏松网状神经纤维结构区，它们相互连接形成了一条与经典听觉神经通路相平行的旁听觉神经通路。这是首次关于鸟类发声、听觉和内分泌三维系统存在直接神经环路联系的较为完正的报道。     

黄雀中脑下丘中央核的纤维联系

<正> 鸟类中脑下丘中央核(central nucleus of the inferior colliculus,ICc)是重要的听觉中继核团。我们曾证明黄雀(Carduelis sipnus)延髓的角状核和层状核投射至ICc。但对鸣禽类黄雀ICc的中枢联系,尚未见报道。由于它是连接延髓至丘脑的重要一环,了解它的纤维联系对理解听觉功能有重要意义。为此我们用HRP顺、逆行示踪方法,研究了黄雀ICc的纤维联系。     

鸣禽发声控制核团古纹状体粗核壳区的投射研究

目的　研究鸣禽端脑古纹状体粗核（ＲＡ）壳区的神经联系。　方法　ＨＲＰ和生物素结合的葡聚糖胺（ＢＤＡ）的神经示踪技术。　结果　鸣禽古纹状体粗核壳区的传入纤维来自新纹状体听区Ｌ１、Ｌ３ 和高级发声中枢壳区（ＨＶＣ ｓｈｅｌｆ）；传出纤维投向间脑卵圆核壳（Ｏｖ ｓｈｅｌｌ）、中脑背外侧核与丘间核之间的界面区（ＭＬｄ／ＩＣｏｉｎｔｅｒｆａｃｅ）。鸣禽古纹状体粗核壳区与高级发声中枢壳区间与已报道的非鸣禽相应脑区一样存在喙－尾投射关系。　结论　鸣禽古纹状体粗核壳区及与其有联系的其他听觉－发声核团壳区可能具有多种生理功能。鸣禽壳区在进化上较为保守。     

gamma-Aminobutyric acid immunoreactivity in brainstem auditory nuclei of the chicken

Using an antiserum directed against gamma-aminobutyric acid (GABA), the presence of presumed GABAergic neurons is demonstrated in the chicken auditory brainstem nuclei: nucleus laminaris, nucleus angularis, superior olive, and the ventral nuclei of the lateral lemniscus. Nucleus magnocellularis contains no immunopositive neurons but numerous GABA-positive terminals surrounding the cells. Terminal labeling is also present in the other auditory nuclei, though scarcer and not always associated with cell bodies. These data suggest an involvement of GABAergic inhibition in auditory processing in the lower auditory pathway of birds.     

Medial auditory thalamic nuclei are necessary for eyeblink conditioning

The auditory conditioned stimulus (CS) pathway that is necessary for delay eyeblink conditioning was investigated with induced lesions of the medial auditory thalamus contralateral to the trained eye in rats. Rats were given unilateral lesions of the medial auditory thalamus or a control surgery followed by twenty 100-trial sessions of delay eyeblink conditioning with a tone CS and then five sessions of delay conditioning with a light CS. Rats that had complete lesions of the contralateral medial auditory thalamic nuclei, including the medial division of the medial geniculate, suprageniculate, and posterior intralaminar nucleus, showed a severe deficit in conditioning with the tone CS. Rats with complete lesions also showed no cross-modal facilitation (savings) when switched to the light CS. The medial auditory thalamic nuclei may modulate activity in a short-latency auditory CS pathway or serve as part of a longer latency auditory CS pathway that is necessary for eyeblink conditioning.     

雄性黄雀与白腰文鸟发声和听觉中枢脑啡肽的分布差异

目的:比较脑啡肽(ENK)在雄性黄雀与白腰文鸟发声核团和听觉中枢内的分布差异。方法:免疫组织化学方法测定ENK的分布,结合计算机图像分析仪检测免疫阳性细胞和末梢的灰度值。结果:(1)黄雀发声核团中ENK的阳性标记物明显比白腰文鸟丰富,差异显著。(2)在黄雀发声学习中枢X区的ENK阳性标记最多,发声高级中枢次之,发声运动中枢古纹状体栎核较少。(3)ENK在两类鸟的听觉中枢丘脑卵圆核壳区、中脑背外侧核壳区、耳蜗核等的分布相似。结论:ENK广泛分布于发声核团和主要听觉中枢内,可能对发声和听觉有一定的调制作用。黄雀比白腰文鸟善于鸣啭,发声核团内的ENK更丰富,提示ENK的丰富程度可能与鸣唱的复杂程度有关。     

Neuropathological changes in auditory brainstem nuclei in cattle with experimentally induced bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE) is characterized by the appearance of spongy lesions in the brain, particularly in the brainstem nuclei. This study evaluated the degenerative changes observed in the central auditory brainstem of BSE-challenged cattle. The neuropathological changes in the auditory brainstem nuclei were assessed by determining the severity of vacuolation and the presence of disease-associated prion protein (PrP(Sc)). Sixteen female Holstein-Friesian calves, 2-4 months of age, were inoculated intracerebrally with BSE agent. BSE-challenged animals developed the characteristic clinical signs of BSE approximately 18 months post inoculation (mpi) and advanced neurological signs after 22 mpi. Before the appearance of clinical signs (i.e. at 3, 10, 12 and 16 mpi), vacuolar change was absent or mild and PrP(Sc) deposition was minimal in the auditory brainstem nuclei. The two cattle sacrificed at 18 and 19 mpi had no clinical signs and showed mild vacuolar degeneration and moderate amounts of PrP(Sc) accumulation in the auditory brainstem pathway. In the animals challenged with BSE agent that developed clinical sings (i.e. after 20 mpi), spongy changes were more prominent in the nucleus of the inferior colliculus compared with the other nuclei of the auditory brainstem and the medial geniculate body. Neuropathological changes characterized by spongy lesions accompanied by PrP(Sc) accumulation in the auditory brainstem nuclei of BSE-infected cattle may be associated with hyperacusia.     

白眉 （Emberiza tristrami Swinhoe）听觉中继核团上橄榄核的神经联系──HRP法研究

采用ＨＲＰ顺逆行示踪技术对白眉　延脑听觉中继核团上橄榄核的纤维联系进行了研究。结果表明：上橄榄核接受双侧角状核的传入投射，并发出纤维上行投射至双侧外侧丘系核和中脑背外侧核。上橄榄核与角状核的联系以同侧为主，与外侧丘系核的联系以对侧为主。上橄榄核还发出纤维下行投射至巨细胞核。双侧上橄榄核之间还存在着交叉投射。     

Extracortical descending projections to the rat inferior colliculus

Feedback controlling is an important element in the sensory processing in the auditory system. It has been long recognized that the inferior colliculus (IC) sends direct ascending projections to the medial geniculate body (MGB), but receives feedback regulation from the auditory cortex. In the present study we probed the shorter extracortical projections to the IC, including the direct descending pathway from the MGB. In the rat, the fluorescence retrograde tracers Fluorogold, True Blue or Rhodamine latex microspheres were injected into the IC, and the auditory thalamus and surrounding regions were examined for fluorescent neurones. We did not find any retrograde labelling in the ventral division of the MGB. However, retrogradely labelled neurones were found in the medial and suprageniculate nuclei of the MGB. We also observed densely packed groups of fluorescent neurones in the peripeduncular nucleus and numerous labelled neurones in the nucleus of the brachium of the IC. The existence of a direct descending pathway to the IC from at least some auditory thalamic nuclei challenges the perception of the colliculo-thalamic relationship as one-way traffic and suggests more direct involvement of the auditory thalamus in the feedback regulation of the incoming acoustic signals.     

GABA immunoreactivity in auditory and song control brain areas of zebra finches

Inhibitory transmission is critical to sensory and motor processing and is believed to play a role in experience-dependent plasticity. The main inhibitory neurotransmitter in vertebrates, GABA, has been implicated in both sensory and motor aspects of vocalizations in songbirds. To understand the role of GABAergic mechanisms in vocal communication, GABAergic elements must be characterized fully. Hence, we investigated GABA immunohistochemistry in the zebra finch brain, emphasizing auditory areas and song control nuclei. Several nuclei of the ascending auditory pathway showed a moderate to high density of GABAergic neurons including the cochlear nuclei, nucleus laminaris, superior olivary nucleus, mesencephalic nucleus lateralis pars dorsalis, and nucleus ovoidalis. Telencephalic auditory areas, including field L subfields L1, L2a and L3, as well as the caudomedial nidopallium (NCM) and mesopallium (CMM), contained GABAergic cells at particularly high densities. Considerable GABA labeling was also seen in the shelf area of caudodorsal nidopallium, and the cup area in the arcopallium, as well as in area X, the lateral magnocellular nucleus of the anterior nidopallium, the robust nucleus of the arcopallium and nidopallial nucleus HVC. GABAergic cells were typically small, most likely local inhibitory interneurons, although large GABA-positive cells that were sparsely distributed were also identified. GABA-positive neurites and puncta were identified in most nuclei of the ascending auditory pathway and in song control nuclei. Our data are in accordance with a prominent role of GABAergic mechanisms in regulating the neural circuits involved in song perceptual processing, motor production, and vocal learning in songbirds.     

Synaptic physiology in the cochlear nucleus angularis of the chick

Nucleus angularis (NA), one of the two cochlear nuclei in birds, is important for processing sound intensity for localization and most likely has role in sound recognition and other auditory tasks. Because the synaptic properties of auditory nerve inputs to the cochlear nuclei are fundamental to the transformation of auditory information, we studied the properties of these synapses onto NA neurons using whole cell patch-clamp recordings from auditory brain stem slices from embryonic chickens (E16-E20). We measured spontaneous excitatory postsynaptic currents (EPSCs), and evoked EPSCs and excitatory postsynaptic potentials (EPSPs) by using extracellular stimulation of the auditory nerve. These excitatory EPSCs were mediated by AMPA and N-methyl-D-aspartate (NMDA) receptors. The spontaneous EPSCs mediated by AMPA receptors had submillisecond decay kinetics (556 micros at E19), comparable with those of other auditory brain stem areas. The spontaneous EPSCs increased in amplitude and became faster with developmental age. Evoked EPSC and EPSP amplitudes were graded with stimulus intensity. The average amplitude of the EPSC evoked by minimal stimulation was twice as large as the average spontaneous EPSC amplitude (approximately 110 vs. approximately 55 pA), suggesting that single fibers make multiple contacts onto each postsynaptic NA neuron. Because of their small size, minimal EPSPs were subthreshold, and we estimate at least three to five inputs were required to reach threshold. In contrast to the fast EPSCs, EPSPs in NA had a decay time constant of approximately 12.5 ms, which was heavily influenced by the membrane time constant. Thus NA neurons spatially and temporally integrate auditory information arriving from multiple auditory nerve afferents.     

Preservation of spectrotemporal tuning between the nucleus laminaris and the inferior colliculus of the barn owl

Performing sound recognition is a task that requires an encoding of the time-varying spectral structure of the auditory stimulus. Similarly, computation of the interaural time difference (ITD) requires knowledge of the precise timing of the stimulus. Consistent with this, low-level nuclei of birds and mammals implicated in ITD processing encode the ongoing phase of a stimulus. However, the brain areas that follow the binaural convergence for the computation of ITD show a reduced capacity for phase locking. In addition, we have shown that in the barn owl there is a pooling of ITD-responsive neurons to improve the reliability of ITD coding. Here we demonstrate that despite two stages of convergence and an effective loss of phase information, the auditory system of the anesthetized barn owl displays a graceful transition to an envelope coding that preserves the spectrotemporal information throughout the ITD pathway to the neurons of the core of the central nucleus of the inferior colliculus.