鸣禽前脑发声控制核团的雌雄差别

本文应用尼氏染色组织学方法,对黄喉鹀(Emberiza elegans)、黄雀(Carduclis spinus)和燕雀(Fringilla montifringilla)三种鸣禽的前脑发声控制核团(HVc,RA,Area X)进行了观察和比较。结果表明,这些核团的体积存在着显著的性双形性。雄鸟的核团体积均大于雌鸟(P<0.001)。说明鸟类鸣啭行为的性别差异是由其神经结构的形态不同所造成的。     

10种鸣禽控制鸣啭神经核团大小与鸣唱复杂性的相关性

为进一步揭示鸣禽鸣唱行为的神经生物学机制 ,本实验先对 8个科 10种鸣禽的鸣唱行为进行了观察和录音 ,并借助声谱软件分析了每种鸣禽的鸣唱复杂性。鸣唱语句复杂性的评价指标包括 :短语总数、每个短语中所含的平均音节数及音节种类数、所有短语的总音节数及音节种类数、最长短语的音节数及音节种类数。然后 ,测定了前脑三个鸣啭学习控制核团和一个与发声无关的视觉参考核团体积 ,分析了鸣唱语句复杂性和这些核团大小间的相关关系。结果表明 :1)HVC和HVC/Rt与 7种鸣唱语句复杂性指标无关 ;RA和RA/Rt与总音节种类数相关 ;AreaX与总音节数及音节种类数相关 ;2 )HVC/RA和HVC/X比值与多个鸣唱语句复杂性指标相关。结果提示 :鸣禽鸣唱复杂性不同特征可能受不同神经控制     

白腰文鸟发声行为的神经发育

本文研究了 5～ 15 0日龄雄性白腰文鸟 (Lonchurastriataswinhoei)不同年龄段的声谱变化以及这种变化的神经调制机制。结果如下 :(1)HVC、RA和AreaX三个发声核团的神经联系基本接近成年鸟的水平后 ,幼鸟才开始学习鸣叫 (约 45日龄 ) ;(2 )HVC、RA和AreaX达到成年核团体积时 (约 80日龄 ) ,幼鸟才具有成年雄鸟的鸣叫模式 ;(3)发声控制核团的发育与核团间的神经支配有关 ,而基本不受鸣唱行为的影响 ,HVC、RA和AreaX的最快增长时间段各不相同 ,三个核团随年龄增长而呈现体积增长的显著变化 (one wayANOVA ,P <0 0 5 ) ,但各核团在任意两个时间段的体积差异并不都显著。结果提示 :发声行为产生的时间和发展与发声控制核团的发育、核团间的神经联系有关 ,最终的体积发育程度受内在遗传力的作用 ,同时可能还受神经核团建立正常神经联系时间的影响     

白腰文鸟发声相关核团体积在发育中的变化及神经机制

首先研究了5-120日龄雌雄白腰文鸟（Lonchura striata swinhoei)4个主要发声核团（RA,LMAN,AreaX和HVC）的体积变化,再通过神经示踪技术研究这些核团与其他核团神经联系的建立时间,以了解发声核团发育及性别分化的神经机制,结果表明：（1）雌雄RA体积均在20,30日龄前后表现出急剧的变化和雌雄差异;雌雄RA在15和25日龄分别接受LMAN和HVC的神经支配,（2）雌雄LMAN体积分别在20,30日龄前先增长,之后均缩小,雌雄LMAN的神经元大小均在15和20日龄间急剧增长,但在该时段之后,不再发生明显变化,雌雄LMAN均在15日龄接受RA的神经支配。（3）AreaX核体积,神经元大小最明显的变化位于20-25日龄间;雌雄AreaX核均在15日龄时接受HVC的神经支配,（4）AreaX核体积,神经元大小最明显的变化位于20-25日龄间;雌雄AreaX核均在15日龄时接受HVC的神经支配,（4）雌雄HVC体积变化的最大值在20和30日龄前后,雄乌HVC的神经元大小在20,30日龄前后,雌鸟在15-20日龄发生较大的变化,其余组间变化小或不明显,雌雄HVC分别在15,25日龄同AreaX核,RA建立神经联系,因此,4个发声核团组织学的明显变化与核团间神经联系的建立相关,说明发声核团间的神经联系可能影响和决定了核团体积在发育中的变化。     

两种鸣禽发声控制核团体积的比较研究

用焦油紫染色,图像分析及统计学方法比较研究了两种鸣禽栗巫鸟和燕雀发声控制核团的体积差异．结果表明,在发声活动中起重要作用的核团前脑ＨＶｃ、ＲＡ 和Ｘ区的体积存在显著的种间差异：发声技巧较高的雄性栗巫鸟的相应核团均相对大于雄性燕雀;而在发声中作用较小的ｎⅫｔｓ及雌性鸣禽的相应所有核团均无显著种间差异． 这一结果表明,发声能力的高低与前脑发声核团的体积直接相关．     

不同生长发育期的虎皮鹦鹉发声行为与发声控制神经核团的研究

鸟类的鸣叫依赖于发育完善的鸣管并接受各级发声中枢组成的机能控制系统的调控,善鸣唱的鸟类前脑控制发声的神经核团发达.用石蜡切片法和生物信号采集处理系统对不同生长发育期的虎皮鹦鹉的发声控制神经核团的体积和声音进行了比较性研究.结果发现:(1)随着虎皮鹦鹉的成长,核团体积逐渐增大,核团轮廓逐渐清晰,而且雄鸟的核团明显大于雌鸟;(2)在鸟类成长的过程中,鸟的叫声越来越复杂,幅度越来越高,雄鸟的叫声比雌鸟更复杂,雌鸟的叫声比雄鸟的叫声幅度更高;(3)鸟类鸣叫的复杂程度和发声控制神经核团的体积呈相关性.     

鸣禽鸣叫学习的神经生物学机制

鸣禽鸣叫具有复杂的神经生理和生化基础,表现为一种复杂的学习过程。鸣啭控制系统是研究神经系统与学习、行为和发育关系的重要模型。而鸣禽鸣叫学习行为与鸣啭控制系统内长时程增强效应、神经元超微结构的改变和神经核团内的电活动、激素水平高低及其周期性变化、神经元再生或改变、即早基因的表达等方面密切相关。对鸣禽鸣叫的神经生物学机制进行了综述。     

蛤蚧视觉神经核团的细胞形态结构及功能的研究

本研究发现,蛤蚧视觉神经核团有视顶盖（OT）、峡核（NI）、基底视束核（nBOR）、豆状核（LM）、中脑深部核（NPM）、圆核（NR）、前背侧室嵴（ADVR）和皮质加厚区（Pth）等,其中NI和ADVR两核团的体积最大。视觉核团中有各种形状的细胞形态,其中梨形和梭形细胞占的比例较大。神经核团的细胞直径为6～30μm,其中以15～28μm最多。在ADVR和Pth核团中有细胞丛簇存在,其它核团尚未发现有这样的结构。各神经核团问和核团内有广泛而复杂的纤维联系。蛤蚧有关视觉神经核团除具有视觉功能外,可能还与听觉、触觉、嗅觉和平衡感觉等功能有关。     

血清性激素在白腰文鸟前脑发声控制核团神经元早期性双态分化中的作用

本文究了雌、雄白腰文鸟(Lonchura striata swinhoei)不同发育时期前脑四个控制发声重要核团古纹状体栎核(RA)、新纹状体前部巨细胞核外侧部(LMAN)、X区(Area X)和高级发声中枢(HVC)中神经元数量、体积和体内雌二醇(E2)和睾酮(T)浓度的变化,以揭示性激素对鸣禽发声核团性双态性分化的影响。结果发现：(1)HVC、LMAN和X区在发育早期神经元数量和体积均呈显著性双态性差异,而RA神经元直至30日龄(P30)后才显示出明显性别差异(P＜0．05);(2)除RA外,HVC、LMAN和X区神经元体积的显著性双态性差异均发生在P20左右,P20后雌、雄核团内的神经元体积仅有较小范围的波动;(3)RA和LMAN神经元数量随年龄增长而逐渐减少;雌、雄鸟HVC和雄鸟X区的神经元数量在P20—30间均增长,雄鸟HVC的增长幅度显著大于雌鸟。P30后HVC和X区的神经元数量不再增加,开始小幅度减少;(4)四个发声核团的神经元数量和体积在P5-120期间均出现1—2个急剧变化期,此变化期与体内雌激素水平开始出现显著性差异的临界期及核团间神经联系开始建立的时期相对应;(5)雌、雄鸟血清中E2的水平在核团发育初期(P5)差异显著,雌鸟为雄鸟的7．45倍,P5后则呈相反方向变化趋势,在P15时雄鸟中的E2水平反超过雌鸟,差异显著(P＜0．05)。睾酮仅在发育P50后的雄鸟体内被检测出,雌鸟中始终未能检测出T的存在。结果提示：雌、雄白腰文鸟发育早期体内E2浓度的变化启动了HVC、LMAN和X区早期神经元性双态性的分化和持续发育;睾酮对雌、雄鸣禽发声控制核团中早期神经元的性双态性分化作用较小[动物学报49(3)：353—361,2003]。     

白腰文鸟发声行为的性别差异及其机制

通过声谱分析,研究了５－１２０日龄雌、雄白腰文鸟（Lonchura striata swinhoei)的声谱变化,及该时段３个主要发声控制核团）ＨＶＣ、ＲＡ、Ａrea X)体积、睾丸（睾酮）的相应改变。结果如下：①４５日龄以前,雌雄鸟只能发出简单鸣叫（call),鸣声基本不会鸣唱。②雄性ＨＶＣ,ＲＡ,ＡreaX体积均比雌性大２－６部。３个核团的大小发育不完全一致。各核团的快速生长期与鸣唱学习的主要时段（６０－１２０日龄）不同步,说明核团的个体发育可能不完全受发声行为的影响。③睾丸的充分发育（１２０日龄后）及血液中具有较高的睾酮水平是雄鸟发出成熟鸣唱语句的重要条件。     

Age- and behavior-related variation in volumes of song control nuclei in male European starlings

There is considerable interindividual variation in the volumes of song control nuclei. Sex and physiological condition appear to contribute to these differences; however, these factors alone do not account for all of the variation. Studies have attempted to relate differences in song behavior (i.e., song repertoire size) to variation in song nucleus volume, but have met with mixed success. In this article, two studies are presented that used male European starlings (Sturnus vulgaris) to explore the relationship between song nuclei volumes and age-related differences in song behavior and interindividual variation in song behavior in adults. The results of the first study showed that song repertoire size and song bout length were significantly greater in older adult than in yearling males. In addition, the volumes of the high vocal center (HVC) and nucleus robustus archistriatalis (RA) were significantly larger in older adults than yearlings. Area X of the parolfactory lobe did not differ significantly in volume between the two age classes. In the second study, both HVC and RA volume correlated positively with song bout length but not repertoire size among adult birds. Based on these results a new hypothesis is presented that states that variation in song nuclei volumes in starlings relates more to the amount of song produced than to the number of song types stored in memory. © 1996 John Wiley & Sons, Inc.     

Androgens and estrogens induce seasonal-like growth of song nuclei in the adult songbird brain

In seasonally breeding songbirds, the brain regions that control song behavior undergo dramatic structural changes at the onset of each annual breeding season. As spring approaches and days get longer, gonadal testosterone (T) secretion increases and triggers the growth of several song control nuclei. T can be converted to androgenic and estrogenic metabolites by enzymes expressed in the brain. This opens the possibility that the effects of T may be mediated via the androgen receptor, the estrogen receptor, or both. To test this hypothesis, we examined the effects of two bioactive T metabolites on song nucleus growth and song behavior in adult male white-crowned sparrows. Castrated sparrows with regressed song control nuclei were implanted with silastic capsules containing either crystalline T, 5alpha-dihydrotestosterone (DHT), estradiol (E(2)), or a combination of DHT+E(2). Control animals received empty implants. Song production was highly variable within treatment groups. Only one of seven birds treated with E(2) alone was observed singing, whereas a majority of birds with T or DHT sang. After 37 days of exposure to sex steroids, we measured the volumes of the forebrain song nucleus HVc, the robust nucleus of the archistriatum (RA), and a basal ganglia homolog (area X). All three steroid treatments increased the volumes of these three song nuclei when compared to blank-implanted controls. These data demonstrate that androgen and estrogen receptor binding are sufficient to trigger seasonal song nucleus growth. These data also suggest that T's effects on seasonal song nucleus growth may depend, in part, upon enzymatic conversion of T to bioactive metabolites.     

Androgens and estrogens induce seasonal‐like growth of song nuclei in the adult songbird brain

In seasonally breeding songbirds, the brain regions that control song behavior undergo dramatic structural changes at the onset of each annual breeding season. As spring approaches and days get longer, gonadal testosterone (T) secretion increases and triggers the growth of several song control nuclei. T can be converted to androgenic and estrogenic metabolites by enzymes expressed in the brain. This opens the possibility that the effects of T may be mediated via the androgen receptor, the estrogen receptor, or both. To test this hypothesis, we examined the effects of two bioactive T metabolites on song nucleus growth and song behavior in adult male white‐crowned sparrows. Castrated sparrows with regressed song control nuclei were implanted with silastic capsules containing either crystalline T, 5α‐dihydrotestosterone (DHT), estradiol (E₂), or a combination of DHT+E₂. Control animals received empty implants. Song production was highly variable within treatment groups. Only one of seven birds treated with E₂ alone was observed singing, whereas a majority of birds with T or DHT sang. After 37 days of exposure to sex steroids, we measured the volumes of the forebrain song nucleus HVc, the robust nucleus of the archistriatum (RA), and a basal ganglia homolog (area X). All three steroid treatments increased the volumes of these three song nuclei when compared to blank‐implanted controls. These data demonstrate that androgen and estrogen receptor binding are sufficient to trigger seasonal song nucleus growth. These data also suggest that T's effects on seasonal song nucleus growth may depend, in part, upon enzymatic conversion of T to bioactive metabolites. © 2003 Wiley Periodicals, Inc. J Neurobiol 57:130–140, 2003     

Lesions of HVc block the developmental masculinizing effects of estradiol in the female zebra finch song system

The neural song control system of female zebra finches is permanently masculinized if the females are given estradiol within 1 month after hatching. One hypothesis is that estradiol acts on neurons in the caudal nucleus of the ventral hyperstriatum (HVc) to cause developmental changes that lead to masculinizing influences in other song control regions. To test whether lesions of HVc block the masculinizing effects of estradiol elsewhere in the song system, we gave 20-day-old females either a Silastic pellet containing estradiol or no implant, and they received either a unilateral lesion of HVc or no lesion. At 60 days of age, they were sacrificed. The volumes of brain regions and sizes of neurons were measured in four song nuclei: HVc, robust nucleus of the archistriatum (RA), lateral magnocellular nucleus of the neostriatum (lMAN), and Area X. Lesions of HVc blocked the masculinizing effects of estradiol on RA and Area X on the side of the lesion. Thus, HVc must be intact in order for estradiol to masculinize these two nuclei. This observation is compatible with the hypothesis that estradiol acts on or near HVc to masculinize several song nuclei, although other interpretations are also possible.     

Neural correlates of singing behavior in male zebra finches (Taeniopygia guttata)

This study examined the relationship between the volumes of four song control nuclei: the high vocal center (HVC), the lateral part of the magnocellular nucleus of the anterior neostriatum (lMAN), Area X, and the robust nucleus of the archistriatum (RA), as well as syrinx mass, with several measures of song output and song complexity in male zebra finches (Taeniopygia guttata). Male zebra finches' songs were recorded in standardized recording sessions. The syrinx and brain were subsequently collected from each bird. Volumes of the song control nuclei were reconstructed by measuring the cross-sectional area of serial sections. Syrinx mass was positively correlated with RA volume. The volume of lMAN was negatively related to element repertoire size and the number of elements per phrase. We found no other correlations between brain and behavioral measures. This study, combined with others, indicates that the evidence for a general relationship among songbirds between HVC volume and song complexity is equivocal. There are clear species differences in this brain-behavior correlation. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 421–430, 1998     

Early condition, song learning, and the volume of song brain nuclei in the zebra finch (Taeniopygia guttata)

Songbirds are an important model system for the study of the neurological bases of song learning, but variation in song learning accuracy and adult song complexity remains poorly understood. Current models of sexual selection predict that signals such as song must be costly to develop or maintain to constitute honest indicators of male quality. It has been proposed that reductions of nestling condition during song development might limit the expression of song learning. Adult song could thus act as an indicator of early stress as only males that enjoy good condition during development could learn accurately and sing long songs or large repertoires. We tested this hypothesis in the zebra finch by modifying early condition through cross-fostering chicks to small, medium, and large broods. Song learning was very accurate and was found to reflect very closely tutor song characteristics and to depend on the number of males in the tutoring group. Although the brood size manipulation strongly affected several measures of nestling condition and adult biometry, we found no relationship between early condition and song learning scores or song characteristics. Similarly, brain mass and high vocal center (HVC), robust nucleus of the arcopallium (RA), and lateral magnocellular nucleus of the anterior nidopallium (LMAN) volumes did not covary with nestling condition and growth measurements. We found no significant relationship between song repertoire size and HVC and RA volumes, although there was a nonsignificant trend for HVC to increase with increasing proportion of learnt elements in a song. In conclusion, the results provide no evidence for song learning to be limited by nestling condition during the period of nutritional dependence from the parents in this species.     

Photoperiodic differences in a forebrain nucleus involved in vocal plasticity: Enkephalin immunoreactivity reveals volumetric variation in song nucleus lMAN but not NIf in male European starlings (Sturnus vulgaris)

Seasonal variation in the volume of various song control nuclei in many passerine species remains one of the best examples of naturally occurring adult neuroplasticity among vertebrates. The lateral portion of the magnocellular nucleus of the anterior nidopallium (lMAN) is a song nucleus that is important for song learning and seems to be critical for inducing variability in the song structure that is later pruned via a feedback process to produce adult crystallized song. To date, lMAN has not been shown to exhibit seasonal changes in volume, probably because it is difficult to resolve the boundaries of lMAN when employing histological methods based on Nissl staining. Here, lMAN_core volumes were examined in intact photostimulated (i.e., breeding), castrated photostimulated and photorefractory (i.e., nonbreeding) male starlings (Sturnus vulgaris) to investigate the degree of seasonal variation in brain morphology. We present data demonstrating that the volumes of the total MAN and lMAN_core delineated by enkephalin immunoreactivity are greater in photostimulated male starlings as compared to photorefractory males. Moreover, two other regions associated with the song system that have not been investigated previously in the context of seasonal plasticity namely (i) the medial portion of MAN (mMAN), and (ii) the nucleus interfacialis (NIf) did not display significant volumetric variation. We propose that greater lMAN_core volumes are associated with the increase in vocal plasticity that is generally observed prior to production of stereotyped song. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 751–763, 2010