Sex difference in the size of the neural song control regions in a dueting songbird with similar song repertoire size of males and females

Previous studies have suggested a causal relation between sex differences in behavior such as singing and sex differences in the size of brain areas such as the forebrain song control areas of songbirds. In the present study we show that the size of the forebrain vocal control areas nucleus hyperstriatalis ventrale pars caudale (HVC) and nucleus robustus archistriatalis (RA) and its neuron numbers are about twice as large in males as in females of the African dueting bush shrike Laniarius funebris. However, song types are of similar complexity (number of elements per song type, physical properties of elements) in both sexes, and repertoire size does not differ between males and females. Furthermore, in captivity male and female shrikes are able to learn the same song types. This demonstrates for the shrike that sex differences in the size of vocal control areas and in its neuron numbers do not predict the type of sex-typical vocal behavior. This result is supported by a statistical comparison of the sex differences in HVC size, RA size, and song repertoire size of all songbird species studied to date. Sex differences in species in which only the males sing are indeed larger than in species in which the females also sing; in songbird species with singing females, however, the sex differences in HVC and RA volume appear to be independent of the vocal repertoire size of females. The songbird model therefore does not support the notion that sex differences in area size and neuron number explain sex differences in a behavior that occurs in both sexes. Furthermore, in the shrike, neuron soma size is similar in males and females in the song motonucleus hypoglossus pars tracheosyringealis (nXIIts) and in the premotor nucleus RA, but is sexually dimorphic in the higher vocal center HVC. Thus, male and female shrikes produce songs of similar complexity with different neuron phenotypes.     

Selective expression of insulin-like growth factor II in the songbird brain

Neuronal replacement occurs in the forebrain of juvenile and adult songbirds. To address the molecular processes that govern this replacement, we cloned the zebra finch insulin-like growth factor II (IGF-II) cDNA, a factor known to regulate neuronal development and survival in other systems, and examined its expression pattern by in situ hybridization and immunocytochemistry in juvenile and adult songbird brains. The highest levels of IGF-II mRNA expression occurred in three nuclei of the song system: in the high vocal center (HVC), in the medial magnocellular nucleus of the neostriatum (mMAN), which projects to HVC, and to a lesser extent in the robust nucleus of the archistriatum (RA), which receives projections from HVC. IGF-II mRNA expression was developmentally regulated in zebra finches. In canary HVC, monthly changes in IGF-II mRNA expression covaried with previously reported monthly differences in neuron incorporation. Combining retrograde tracers with in situ hybridization and immunocytochemistry, we determined that the HVC neurons that project to area X synthesize the IGF-II mRNA, whereas the adjacent RA-projecting neurons accumulate the IGF-II peptide. Our findings raise the possibility that within HVC IGF-II acts as a paracrine signal between nonreplaceable area X-projecting neurons and replaceable RA-projecting neurons, a mode of action that is compatible with the involvement of IGF-II with the replacement of neurons. Additional roles for IGF-II expression in songbird brain are likely, because expression also occurs in some brain areas outside the song system, among them the cerebellar Purkinje cells in which neurogenesis is not known to occur.     

Syllable chunking in zebra finch (Taeniopygia guttata) song.

Examined how 61 young zebra finch males copied song from 5 adult tutors. Zebra finch song consists of a string of 5–25 distinct syllables, and these syllables were copied as chunks, or strings of consecutive syllables (modal length?=?3). The silent interval between 2 syllables was copied as part of the syllable after the silence. Copied chunks had boundaries that fell at consistent locations within the tutor's song, marked by a relatively long intersyllable silent period, a transition between call-like and noncall-like syllables, and a tendency for the tutor male to stop his song short. Young males also tended to break their songs off at the bondaries of the chunks they had copied. Chunks appear to be an intermediate level of hierarchy in song organization and to have both perceptual (syllables were learned as part of a chunk) and motor (song delivery was broken almost exclusively at chunk boundaries) aspects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired beta-adrenergic receptor stimulation of cyclic adenosine monophosphate in human septic shock: association with myocardial hyporesponsiveness to catecholamines

Birdsong is believed to provide the most adequate model for studying the learning process of human language. Songbirds require external song models after birth to learn their songs which contain highly complicated acoustic variables. They memorize their song models as 'templates' in their brains during a particular phase (sensitive phase), whereas vocalization starts in a subsequent step (sensorimotor phase). There may be two song templates: one innate and the other learned. A different nucleus in the song control system of the songbird brain may be responsible for each template. These nuclei are probably analogous to discrete cerebral nuclei of the human language system, including Broca's area.     

Characterization of four toxins from Buthus martensi scorpion venom, which act on apamin-sensitive Ca2+-activated K+ channels

What are the relative roles of imitation, improvisation and invention in the development of large song repertoires in species of the songbird family Mimidae? This question was addressed in a laboratory study of the vocal development of young grey catbirds, Dumetella carolinensiscollected from western Massachusetts. Two groups heard a repeated 10-s, tape-tutored segment of catbird song, two other groups heard a repeated 16-min segment and a fifth group heard no tape-tutored songs. One male selected for study from each group developed a large repertoire of seemingly normal songs, and wild males responded strongly to songs of the male that had heard no tape-tutored song. Relying little on precise imitation and largely on improvising or inventing, each male developed a highly unique repertoire. A geographical survey of catbird song revealed little to no evidence of song sharing or microgeographical variation, which is consistent with the idea that imitation plays a relatively minor role in song development. Perhaps simultaneous selection for large repertoires and reduced geographical variation has led to such an emphasis on song individuality and non-imitative developmental processes.     

Birdsong.

Vocalizations used by birds for territory defense, mate attraction, or both are often referred to as a given species' song. Birdsong refers to the often complex vocalizations produced most frequently by males of species that are members of the songbird order (passeriformes). Unlike most species-typical vocalizations produced by nonhuman animals, some songbird vocalizations are learned. Studies of birdsong learning, production, and perception address issues of fundamental interest to psychologists and others interested in behavior and its physiological underpinnings and provide the basis for this review. This article highlights recent advances in knowledge as illustrations of the utility of birdsong as an arena for significant new developments in experimental psychology and behavioral neuroscience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Song structure and song development as potential contributors to reproductive isolation in cowbirds (Molothrus ater).

Two experiments studied the songs of 2 subspecies of the brown-headed cowbird, Molothrus ater ater (22 Ss) and Molothrus ater obscurus (32 Ss), in 3 ways: by comparisons of song variation, by developmental analyses of the role of species-typical stimulation in M. a. ater, and by playback to captive females. Results indicate the presence of intraspecific variation. The songs of adult M. a. obscurus contained a song element not present in the songs of adult M. a. ater. This element did occur, however, in the songs of juvenile M. a. ater reared either in isolation from conspecifics or in contact with M. a. obscurus adults. In addition, it was found that captive female cowbirds responded differentially to songs from their own geographic area. Findings suggest that song can act as a mechanism of selective mating and thus has the potential to affect reproductive isolation. They also indicate the importance of juvenile experience and learning in the song development of an entirely parasitic species. (52 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Early experience and plasticity of song in adult male zebra finches (Taeniopygia guttata).

Zebra finches (Taeniopygia guttata) learn song primarily at 35–65 days of age, but birds deprived of experience at that stage may modify their songs later. Experiments on 5 groups examined the effect of varying early social experience on the plasticity of adult song. Major changes of song in adulthood were rare, and new syllables were memorized only in the more socially impoverished groups. Most songs underwent minor changes, in syllable structure or stereotypy, as well as in the addition or deletion of syllables. Two factors appeared to be important in determining the amount of change: the extent of social deprivation that the bird had experienced and, in the case of group-reared birds, the degree of song matching between social companions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Song Perception During the Sensitive Period of Song Learning in Zebra Finches (Taeniopygia guttata).

The sensitive period is a special time for auditory learning in songbirds. However, little is known about perception and discrimination of song during this period of development. The authors used a go/no-go operant task to compare discrimination of conspecific song from reversed song in juvenile and adult zebra finches (Taeniopygia guttata), and to test for possible developmental changes in perception of syllable structure and syllable syntax. In Experiment 1, there were no age or sex differences in the ability to learn the discrimination, and the birds discriminated the forward from reversed song primarily on the basis of local syllable structure. Similar results were found in Experiment 2 with juvenile birds reared in isolation from song. Experiment 3 found that juvenile zebra finches could discriminate songs on the basis of syllable order alone, although this discrimination was more difficult than one based on syllable structure. The results reveal well-developed song discrimination and song perception in juvenile zebra finches, even in birds with little experience with song. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do stimulus–stimulus contingencies affect song learning in zebra finches (Taeniopygia guttata)?

In many songbird species, song learning is enhanced by live interaction with a tutor. The authors investigated whether this effect results from a sensitivity of the song learning process to a contingency between tutor song and visual stimulation. To this end, 3 groups of zebra finches (Taeniopygia guttata) were exposed to played-back tutor song. In 2 groups, the song was contingent with the presentation of a stuffed adult male, in one group before and in the other group after the song. A 3rd (control) group was exposed to tutor song only. There was evidence of song copying in all groups, but there was no difference in copying among the groups. Thus, there was no evidence that contingencies between tutor song and visual stimulation had a facilitating effect on song learning in zebra finches. There was also no evidence that song learning was facilitated by the possibility of anticipating tutor song, nor did the presence of a visual stimulus with a potential social meaning have an effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual differentiation of the zebra finch song system: positive evidence, negative evidence, null hypotheses, and a paradigm shift

Permanent sex differences in the brain are found in many vertebrates, and are thought to be induced by sex differences in secretion of gonadal steroid hormones during critical periods of early development. This theory has received support primarily from many experiments conducted on mammals, but also from studies on other vertebrate classes, including birds. The only avian neural dimorphism that has allowed extensive tests of this hypothesis is the neural circuit for song in passerine birds, which is much larger in males than in females. Experiments in zebra finches have yielded contradictory results. Although it is relatively easy to induce masculine patterns of development in genetic females with estrogen, it has not been possible to induce feminine patterns of development in males with any treatments, including antiestrogens and inhibitors of estrogen synthesis. Moreover, genetic females that develop with large amounts of functional testicular tissue but with virtually no ovarian tissue nevertheless have a feminine song circuit. The latter studies fail to support the idea of steroid induction of sexual differentiation. An alternative to the steroidal control hypothesis is that nonhormonal gene products expressed in the brain early in development trigger sexually dimorphic patterns of development. Although current evidence in several neural and nonneural systems indicates that sexual differentiation of some somatic phenotypes cannot be explained by the actions of gonadal steroids, the idea of direct genetic (nonhormonal) induction of sexual differentiation has yet to be proved.     

Perception of temporal properties in self-generated songs by Bengalese finches (Lonchura striata var. domestica).

In the songbird forebrain, neuronal selectivity for temporal properties of each bird's self-generated song has been well described, but the behavioral and perceptual correlates of this selectivity are not known. By operant procedures, the authors trained Bengalese finches (Lonchura striata var. domestica) to discriminate between songs that were played normally and in reverse. Male Bengalese finches learned the discrimination quicker when their self-generated song was used as a stimulus than when a song of another conspecific bird was used. When the global note order was retained but each note was locally reversed, the song was more likely to be regarded as a forward song by the singer himself, but not by other birds. These results provide psychophysical evidence that the special processing of the self-generated song observed at the neural level might reflect an individual's perception of his self-produced song. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermotolerance in Saccharomyces cerevisiae: the Yin and Yang of trehalose

What is neuroinformatics? What is the Human Brain Project? Why should you care? Supported by a consortium of US funding agencies, the Human Brain Project aims to bring to the analysis of brain function the same advantages of Internet-accessible databases and database tools that have been crucial to the development of molecular biology and the Human Genome Project. The much greater complexity of neural data, however, makes this a far more challenging task. As a pilot project in this new initiative, we review some of the progress that has been made and indicate some of the problems, challenges and opportunities that lie ahead.     

Developmental determinants of structure in zebra finch song.

Zebra finches (Taeniopygia guttata) possess highly organized species-uniform song structure. The present author explored song determinants by a series of 5 studies in which a total of 85 young Ss were (a) reared in social contact with zebra finch adults, (b) reared in isolation from adult song, (c) deafened early in life, (d) tutored by zebra finch males they could not see, or (e) tutored with sounds other than zebra finch song. The main song determinants appear to be (a) learning, which probably determines song structure accurately for a limited number of generations; (b) inherited neuromotor constraints that specify basic temporal patterning within song; and (c) infusion of developmentally conservative calls and noncall isolate note types into song. Limitations on song development imposed by effector organs are relatively permissive, and the role of inherited auditory specifications (template) is uncertain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vocal syntax development in the white-crowned sparrow (Zonotrichia leucophrys).

Birdsong development exemplifies the interplay between experience and predisposition that occurs during behavioral ontogeny. Songbirds must hear song models to develop normal song, yet they preferentially learn conspecific song when given a choice in the laboratory. To the extent that features guiding this selective learning are pre-encoded in the brain, such features should also develop in the song of young birds not exposed to them in tutor models. To investigate whether song syntax—phrase number and order—is such a feature in the white-crowned sparrow (Zonatrichia leucophrys), the authors tutored males of this species with separate phrase models. Birds learned and assembled these into songs of species-typical sequence, suggesting that syntax is to some degree pre-encoded in white-crowned sparrows. Birds also learned heterospecific phrases, confirming previous evidence that note phonology is not the primary cue for selective song learning in this species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transient expression and transport of brain-derived neurotrophic factor in the male zebra finch's song system during vocal development

The distribution of brain-derived neurotrophic factor (BDNF) in the song system of male zebra finches changes with posthatching age. At day 20, the hyperstriatum ventrale, pars caudale is the only song nucleus in which neurons showed BDNF immunoreactivity. At day 45, the staining in hyperstriatum ventrale, pars caudale was denser than at day 20 and the robust nucleus of the archistriatum, another song nucleus, showed BDNF labeling. By day 65, two additional song nuclei, area X and the lateral magnocellular nucleus of the anterior neostriatum, have become immunoreactive. In the adult, however, the amount of BDNF labeling in all of these brain nuclei is sharply reduced. These sequential events, the anatomical connections between these song nuclei, and the labeling of relevant axons and terminals suggest anterograde transport of BDNF. Furthermore, the timing of BDNF expression coincident with the development of singing behavior suggests that this neurotrophin may be directly involved with the differentiation of the song system.     

Harnessing Brain Plasticity through Behavioral Techniques to Produce New Treatments in Neurorehabilitation.

Basic behavioral neuroscience research with monkeys has given rise to an efficacious new approach to the rehabilitation of movement after stroke, cerebral palsy, traumatic brain injury, and other types of neurological injury in humans termed Constraint-Induced Movement therapy or CI therapy. For the upper extremity, the treatment involves intensive training of the more affected arm by "shaping," the application of a number of other behavioral techniques, and prolonged constraint of use of the less affected arm. CI therapy has been shown to produce large changes in the organization and function of the brain. This result points to the fact that behavior can have a profound effect on the nervous system that is greater than is generally recognized, and harnessing this brain plasticity by behavioral means has promise for the development of new treatments in the field of rehabilitation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of video images by zebra finches (Taeniopygia guttata): Direct evidence from song performance.

Adult male zebra finches (Taeniopygia guttata) were found to work for the reward of viewing silent video images. In addition, birds that were exposed either passively or contingently upon key pecking to an array of moving images randomly displayed on a video monitor responded with song, depending on the content of the images. In both Experiment 1 (with full-screen images) and Experiment 2 (with sections of images), the subjects clearly discriminated between bird and nonbird pictures. Stimulus movement was found to affect the response only when bird pictures were presented, thus ruling out the evidence for species recognition. The methodology offers a new behavioral assay for investigating categorical perception of pictorial stimuli by songbirds. It has also the potential to provide further insights into the role of visual cues in song learning and social interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sustained long term potentiation and anxiety in mice lacking the Mas protooncogene

The Mas protooncogene is a maternally imprinted gene encoding an orphan G protein-coupled receptor expressed mainly in forebrain and testis. Here, we provide evidence for a function of Mas in the central nervous system. Targeted disruption of the Mas protooncogene leads to an increased durability of long term potentiation in the dentate gyrus, without affecting hippocampal morphology, basal synaptic transmission, and presynaptic function. In addition, Mas-/- mice show alterations in the onset of depotentiation. The permissive influence of Mas ablation on hippocampal synaptic plasticity is paralleled by behavioral changes. While spatial learning in the Morris water maze is not significantly influenced, Mas-deficient animals display an increased anxiety as assessed in the elevated-plus maze. Thus, Mas is an important modulating factor in the electrophysiology of the hippocampus and is involved in behavioral pathways in the adult brain.