High Vocal Center Research Articles

Resilience of A Learned Motor Behavior After Chronic Disruption of Inhibitory Circuits.

Maintaining motor behaviors throughout life is crucial for an individual's survival and reproductive success. The neuronal mechanisms that preserve behavior are poorly understood. To address this question, we focused on the zebra finch, a bird that produces a highly stereotypical song after learning it as a juvenile. Using cell-specific viral vectors, we chronically silenced inhibitory neurons in the pre-motor song nucleus called the high vocal center (HVC), which caused drastic song degradation. However, after producing severely degraded vocalizations for around 2 months, the song rapidly improved, and animals could sing songs that highly resembled the original. In adult birds, single-cell RNA sequencing of HVC revealed that silencing interneurons elevated markers for microglia and increased expression of the Major Histocompatibility Complex I (MHC I), mirroring changes observed in juveniles during song learning. Interestingly, adults could restore their songs despite lesioning the lateral magnocellular nucleus of the anterior neostriatum (LMAN), a brain nucleus crucial for juvenile song learning. This suggests that while molecular mechanisms may overlap, adults utilize different neuronal mechanisms for song recovery. Chronic and acute electrophysiological recordings within HVC and its downstream target, the robust nucleus of the archistriatum (RA), revealed that neuronal activity in the circuit permanently altered with higher spontaneous firing in RA and lower in HVC compared to control even after the song had fully recovered. Together, our findings show that a complex learned behavior can recover despite extended periods of perturbed behavior and permanently altered neuronal dynamics. These results show that loss of inhibitory tone can be compensated for by recovery mechanisms partly local to the perturbed nucleus and do not require circuits necessary for learning.

Notch1 is involved in cell proliferation and neuronal differentiation in the HVC of zebra finch (Taeniopygia guttata)

Significant sex differences are found in songbirds’ song control nuclei and their controlled song behaviors. To elucidate the underlying mechanisms, we explored the role of Notch1 during the development of the high vocal centre (HVC) and song learning in zebra finch. Our study first found that Notch1 positive cells were distributed in HVC with female-biased densities at posthatching day (PHD) 15, but male-biased at PHD 45 and adult. There were about 60 putative oestrogen-responsive elements within 2.5 kb upstream of Notch1, and Notch1 mRNA in the explants that contained the developing male HVC was significantly increased after estrogen addition into the cultured medium for 48 h. After injecting Notch1-interfering lentivirus into the male or female HVC at PHD 15, cell proliferation was significantly promoted in the ventricle zone overlying the HVC at PHD 23. In addition, neuronal differentiation towards Hu+ /BrdU+ at PHD 31, mature neurons (NeuN+/BrdU+) including those projecting to RA in HVC and the sizes of HVC and RA at adult increased significantly after Notch1-interfering lentiviruses were injected into the male HVC at PHD 15. However, the above measurements decreased, following the injection of the lentiviruses expressing Notch intracellular domain (NICD). Finally, the repeat numbers of syllables ‘b′ or ‘c′ of learned songs changed after the injection of Notch1-interfering or NICD-expressing lentiviruses into the HVC at PHD15. Our study suggests that Notch1 is related to the development of HVC and song learning in the zebra finch.

The effects of Wnt, BMP, and Notch signaling pathways on cell proliferation and neural differentiation in a song control nucleus (HVC) of Lonchura striata.

There is obvious sexual dimorphism in the song control system of songbirds. In the higher vocal center (HVC), cell proliferation and neuronal differentiation contribute to the net addition of neurons. However, the mechanism underlying these changes is unclear. Given that Wnt, Bmp, and Notch pathways are involved in cell proliferation and neuronal differentiation, no reports are available to study the role of the three pathways in the song control system. To address the issue, we studied cell proliferation in the ventricle zone overlying the developing HVC and neural differentiation within the HVC of Bengalese finches (Lonchura striata) at posthatching day 15 when HVC progenitor cells are generated on a large scale and differentiate into neurons, after Wnt and Bmp pathways were activated by using a pharmacological agonist (LiCl) or Bmp4, respectively, and the Notch pathway was inhibited by an inhibitor (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester), DAPT). The results indicated that both cell proliferation and neural differentiation toward HVC neurons increased significantly after activation of the Wnt signaling pathway or inhibition of the Notch signaling pathway. Although cell proliferation was increased, neural differentiation was inhibited after treatment with Bmp4. There was obvious synergetic enhancement in the number of proliferating cells after the coregulation of two or three signaling pathways. In addition, synergetic enhancement was also found in the Wnt and Notch pathways in neural differentiation toward neurons within HVC. These results suggest that the three signaling pathways are involved in cell proliferation and neural differentiation of HVC.

Inflammation Induced by Natural Neuronal Death and LPS Regulates Neural Progenitor Cell Proliferation in the Healthy Adult Brain.

Inflammation is typically considered a negative response to injury or insult; however, recent advances demonstrate that inflammatory cells regulate development, plasticity, and homeostasis through anticytotoxic, progenerative responses. Here, we extend analyses of neuroinflammation to natural neurodegenerative and homeostatic states by exploiting seasonal plasticity in cytoarchitecture of the avian telencephalic song control nucleus, high vocal center [HVC (proper name)], in the songbird Gambel’s white-crowned sparrow (Zonotrichia leucophrys gambelii). We report that local injection of the endotoxin lipopolysaccharide into HVC of birds in both breeding (high circulating testosterone level) and nonbreeding (low circulating testosterone level) conditions increased neural progenitor cell proliferation in the nearby but distinct ventricular zone. Additionally, we found that oral administration of the anti-inflammatory drug minocycline during seasonal regression of HVC reduced microglia activation in HVC and prevented the normal proliferative response in the ventricular zone to apoptosis in HVC. Our results suggest that local neuroinflammation positively regulates neural progenitor cell proliferation and, in turn, contributes to the previously described repatterning of HVC cytoarchitecture following seasonally induced neuronal loss.

Acute neuroestrogen blockade attenuates song-induced immediate early gene expression in auditory regions of male and female zebra finches.

Neuron-derived estrogens are synthesized by aromatase and act through membrane receptors to modulate neuronal physiology. In many systems, long-lasting hormone treatments can alter sensory-evoked neuronal activation. However, the significance of acute neuroestrogen production is less understood. Both sexes of zebra finches can synthesize estrogens rapidly in the auditory cortex, yet it is unclear how this modulates neuronal cell signaling. We examined whether acute estrogen synthesis blockade attenuates auditory-induced expression of early growth response 1 (Egr-1) in the auditory cortex of both sexes. cAMP response element-binding protein phosphorylation (pCREB) induction by song stimuli and acute estrogen synthesis was also examined. We administered the aromatase inhibitor fadrozole prior to song exposure and measured Egr-1 across several auditory regions. Fadrozole attenuated Egr-1 in the auditory cortex greater in males than females. Females had greater expression and clustering of aromatase cells than males in high vocal center (HVC) shelf. Auditory-induced Egr-1 expression exhibited a large sex difference following fadrozole treatment. We did not observe changes in pCREB expression with song presentation or aromatase blockade. These findings are consistent with the hypothesis that acute neuroestrogen synthesis can drive downstream transcriptional responses in several cortical auditory regions, and that this mechanism is more prominent in males.

Seasonal changes in the song control nuclei of the Rufous‐bellied Thrush, Turdus rufiventris (Oscine, Passeriformes, and Turdidae)

In vocal learning birds, memorization and song production rely on a set of telencephalic nuclei referred to as the song control system. Seasonal changes in song production are correlated with changes in the volume of the song control nuclei and are influenced by photoperiodic conditions and hormonal cues. The seasonal volume changes in the avian brain that controls singing are thought to involve regulation of neuronal replacement, which is a striking example of neuronal plasticity. The Rufous-bellied Thrush (Turdus rufiventris) is a seasonally breeding bird that actively sings during the spring and summer (breeding season) and is relatively silent in the fall, yet possible mechanisms behind the periodic changes in song production remain unknown. Here, we have examined two song control nuclei: High vocal center (HVC) and robust nucleus of arcopallium (RA) in fall males, spring males, and fall females of Rufous-bellied Thrush. The cytoarchitectonic organization was analyzed and quantified from Nissl-stained sections, and gene expression of song nuclei markers was examined by in situ hybridization during breeding and nonbreeding seasons. We observed a reduction in HVC volume and reductions in parvalbumin, and RGS4 expression in HVC and RA in males during the nonbreeding season. These findings provide evidence of seasonal changes in the song system of a representative tropical-breeding Turdidae species that does not maintain territories or mate bonding, setting the histological and molecular groundwork for future studies aimed at better understanding of song nuclei changes in seasonally breeding songbirds.

Simulation of the song motor pathway in birds: A single neuron initiates a chain of events that produces birdsong with realistic spectra properties.

Birdsong is a complex learned behavior regulated by Neuromuscular coordination of different muscle sets necessary for producing relevant sounds. We developed a heterogeneous and stochastically connected neural network representing the pathway from the high vocal center (HVC) to the robust nucleus of the arcopallium (RA) neurons that drive the muscles to generate sounds. We show that a single active neuron is sufficient to initiate a chain of spiking events that results to excite the entire network system. The network could synthesize realistic bird sounds spectra, with spontaneous generation of intermittent sound bursts typical of birdsong (song syllables). This study confirms experiments on animals and on humans, where results have shown that single neurons are responsible for the activation of complex behavior or are associated with high-level perception events.

Exploring sex differences in the adult zebra finch brain: In vivo diffusion tensor imaging and ex vivo super-resolution track density imaging

Zebra finches are an excellent model to study the process of vocal learning, a complex socially-learned tool of communication that forms the basis of spoken human language. So far, structural investigation of the zebra finch brain has been performed ex vivo using invasive methods such as histology. These methods are highly specific, however, they strongly interfere with performing whole-brain analyses and exclude longitudinal studies aimed at establishing causal correlations between neuroplastic events and specific behavioral performances. Therefore, the aim of the current study was to implement an in vivo Diffusion Tensor Imaging (DTI) protocol sensitive enough to detect structural sex differences in the adult zebra finch brain. Voxel-wise comparison of male and female DTI parameter maps shows clear differences in several components of the song control system (i.e. Area X surroundings, the high vocal center (HVC) and the lateral magnocellular nucleus of the anterior nidopallium (LMAN)), which corroborate previous findings and are in line with the clear behavioral difference as only males sing. Furthermore, to obtain additional insights into the 3-dimensional organization of the zebra finch brain and clarify findings obtained by the in vivo study, ex vivo DTI data of the male and female brain were acquired as well, using a recently established super-resolution reconstruction (SRR) imaging strategy. Interestingly, the SRR-DTI approach led to a marked reduction in acquisition time without interfering with the (spatial and angular) resolution and SNR which enabled to acquire a data set characterized by a 78μm isotropic resolution including 90 diffusion gradient directions within 44h of scanning time. Based on the reconstructed SRR-DTI maps, whole brain probabilistic Track Density Imaging (TDI) was performed for the purpose of super resolved track density imaging, further pushing the resolution up to 40μm isotropic. The DTI and TDI maps realized atlas-quality anatomical maps that enable a clear delineation of most components of the song control and auditory systems. In conclusion, this study paves the way for longitudinal in vivo and high-resolution ex vivo experiments aimed at disentangling neuroplastic events that characterize the critical period for vocal learning in zebra finch ontogeny.

Resonances and Spectral Characteristics of a Neural Network for the Song Motor Pathway in Birds

Birdsong is a complex learned behavior regulated in an intricate way. Neuromuscular coordination of different muscular sets is necessary for producing high quality and consistent songs. We developed a realistic neural network that emulates neurons from the High Vocal centre (HVc) and the robust nucleus of the archistriatum (RA) neurons that drive the muscles to generate birdsong sounds. We used modern computational tools and neural architecture to simulate the entire motor pathway up to the physical oscillator muscle system and its spectral characteristics. Several network parameter dependences were analysed and elucidated. An optimal network size within 10 to 25 neurons within which minimal and smooth frequency variations occur, was found. Beyond that range we observe, instead, strong frequency dependence. Moreover, response frequency is influenced by the pathway input current; also in this case frequency response keeps smooth within a certain range of current, but shows interesting resonant values where negative peaks are observed. Resonant values are found in respect to the non-linear dissipation constant of the equation of motion for the bird's labial oscillation and also in respect of the network background noise level (stochastic resonance). This work demonstrate that is possible to achieve a realistic computational model for the motor pathway leading to generation of sounds in birds, which contributes to the understanding of its spectral and dynamical fundamental properties and characteristics.

Testosterone Mediates Seasonal Growth of the Song Control Nuclei in a Tropical Bird

In mid- to high-latitude songbirds, seasonal reproduction is stimulated by increasing day length accompanied by elevated plasma sex steroid levels, increased singing, and growth of the song control nuclei (SCN). Plasticity of the SCN and song behavior are primarily mediated by testosterone (T) and its metabolites in most species studied thus far. However, the majority of bird species are tropical and have less pronounced seasonal reproductive cycles. We have previously documented that equatorial rufous-collared sparrows (Zonotrichia capensis) exhibit seasonal neuroplasticity in the SCN. Manipulating T in these birds, however, did not alter singing behavior. In the current study, we investigated whether T mediates plasticity of the SCN in a similar manner to temperate songbirds. In the first experiment, we treated captive male birds with T or blank implants during the nonbreeding season. In a second experiment, we treated captive male birds with either blank implants, T-filled implants, T with flutamide (FLU; an androgen receptor antagonist) or T with FLU and 1,4,6-androstatriene-3,17-dione (ATD; an estrogen synthesis inhibitor) during the breeding season. In both experiments, the volumes of the brain areas high vocal center (HVC), Area X, and robust nucleus of the arcopallium (RA) were measured along with singing behavior. In summary, T stimulated growth of HVC and RA, and the combined effect of FLU and ATD reversed this effect in HVC. Area X was not affected by T treatment in either experiment. Neither T-treated birds nor controls sang in captivity during either experiment. Together, these data indicate that T mediates seasonal changes in the HVC and RA of both tropical and higher- latitude bird species even if the environmental signals differ. However, unlike most higher-latitude songbirds, we found no evidence that motivation to sing or growth of Area X are stimulated by T under captive conditions.

Sexual Differences in Cell Loss during the Post-Hatch Development of Song Control Nuclei in the Bengalese Finch

Birdsongs and the regions of their brain that control song exhibit obvious sexual differences. However, the mechanisms underlying these sexual dimorphisms remain unknown. To address this issue, we first examined apoptotic cells labeled with caspase-3 or TUNEL in Bengalese finch song control nuclei - the robust nucleus of the archopallium (RA), the lateral magnocellular nucleus of the anterior nidopallium (LMAN), the high vocal center (HVC) and Area X from post-hatch day (P) 15 to 120. Next, we investigated the expression dynamics of pro-apoptotic (Bid, Bad and Bax) and anti-apoptotic (Bcl-2 and Bcl-xL) genes in the aforementioned nuclei. Our results revealed that the female RA at P45 exhibited marked cell apoptosis, confirmed by low densities of Bcl-xL and Bcl-2. Both the male and female LMAN exhibited apoptotic peaks at P35 and P45, respectively, and the observed cell loss was more extensive in males. A corresponding sharp decrease in the density of Bcl-2 after P35 was observed in both sexes, and a greater density of Bid was noted at P45 in males. In addition, we observed that RA volume and the total number of BDNF-expressing cells decreased significantly after unilateral lesion of the LMAN or HVC (two areas that innervate the RA) and that greater numbers of RA-projecting cells were immunoreactive for BDNF in the LMAN than in the HVC. We reasoned that a decrease in the amount of BDNF transported via HVC afferent fibers might result in an increase in cell apoptosis in the female RA. Our data indicate that cell apoptosis resulting from different pro- and anti-apoptotic agents is involved in generating the differences between male and female song control nuclei.

Activation of D1-like dopamine receptors increases the NMDA-induced gain modulation through a PKA-dependent pathway in the premotor nucleus of adult zebra finches

Interaction between dopamine (DA) and N-methyl-d-aspartate (NMDA) in the brain plays an important role in learning and memory. In the songbirds, the premotor robust nucleus of the arcopallium (RA) receives excitatory glutamatergic inputs from the high vocal center (HVC) and lateral magnocellular nucleus of the anterior nidopallium (LMAN), as well as dopaminergic inputs mostly from the periaqueductal gray (PAG) and ventral tegmental area (VTA). In zebra finch, DA potentiates the excitability of projection neurons in the RA through activation of D1-like dopamine receptors (D1 receptors). The relationship between D1 receptors and NMDA in the RA projection neurons is essentially unknown. Our previous work showed that NMDA can induce gain modulation in the RA projection neurons. Here, using the whole-cell current-clamp recording from brain slices of male zebra finches, we observed whether D1 receptors regulate the NMDA-induced gain modulation in the RA projection neurons. Our results showed that activation of D1 receptors further increased the slope (gain) of the firing frequency–injected current (f–I) relationship induced by NMDA in the RA projection neurons. Blocking D1 receptors had no effect on the NMDA-induced gain modulation in the RA projection neurons. The enhanced effects of D1 receptors agonists were blocked by protein kinase A (PKA) inhibitors. Our results suggest that activation of D1 receptors can increase the NMDA-induced gain modulation through a PKA-dependent pathway.

Duration of melatonin regulates seasonal plasticity in subtropical Indian weaver bird, Ploceus philippinus

Day length regulates seasonal plasticity connected with reproduction in birds. Rhythmic pineal melatonin secretion is a reliable indicator of the night length, hence day length. Removal of rhythmic melatonin secretion by exposure to constant bright light (LLbright) or by pinealectomy renders several species of songbirds including Indian weaver bird (Ploceus philippinus) arrhythmic. Present study investigated whether rhythmic melatonin is involved in the regulation of key reproductive neuropeptides (GnRH I and GnIH) and reproduction linked neural changes, viz. song control nuclei, in Indian weaver birds. Two experiments were performed using birds in an arrhythmic condition with low (under LLbright) or no (in the absence of pineal gland) endogenous melatonin. In experiment I, three groups of birds (n=5 each) entrained to 12L:12D were exposed to LLbright (25lux) for two weeks. Beginning on day 15 of LLbright, a control group received vehicle for 16h and two treatment groups were given melatonin in drinking water for 8h or 16h. In experiment II, one group of sham-operated and three groups of pinealectomized birds (n=5 each) entrained to 12L:12D were exposed to constant dim light (LLdim, 0.5lux). Beginning on day 15 of LLdim, three groups received similar treatment as in experiment I. Birds were perfused after thirty cycles of the melatonin treatment, and brain sections were immunohistochemically double-labeled for GnRH I and GnIH or Nissl stained. Activity was recorded throughout the experiments, while body mass and testes were measured at the beginning and end of the experiment. Birds were synchronized with melatonin cycles and measured the duration of melatonin as “night”. Pinealectomized birds that received 16h of melatonin had significantly higher GnIH-ir cells than those received 8h melatonin; there was no difference in the GnRH I immunoreactivity between two treatment groups however. Intact birds that received long duration melatonin cycles exhibited small song control nuclei, specifically the high vocal center (HVC) and the robust nucleus of the arcopallium (RA), while birds that received short duration melatonin or no melatonin exhibited large HVC and RA. Thus, melatonin possibly regulates seasonal reproduction via GnIH secretion, and also controls seasonal neuroplasticity in the song control system in songbirds.

Right Side Dominance of Song Control in High Vocal Center in Adult Male Zebra Finches

Right Side Dominance of Song Control in High Vocal Center in Adult Male Zebra Finches

Lateral differences in the forebrain and midbrain control of learned vocalizations in adult male Zebra Finch ( Taeniopygia guttata )

Learned vocalizations (long call and song) of adult male songbirds start from the high vocal center (HVC), and are integrated and output by the robust nucleus of the arcopallium (RA), which connects synaptic relationships with the dorsomedial nucleus of the intercollicular complex (DM). To determine the effect on learned vocalization of the unilateral forebrain and midbrain in adult male zebra finch, electrolytic lesions and acoustic analysis technology were used. The results indicated that RA and DM nuclei are involved in the control of learned vocalization, and the right side is dominant in the forebrain and midbrain.

Comparative aspects of adult neural stem cell activity in vertebrates

At birth or after hatching from the egg, vertebrate brains still contain neural stem cells which reside in specialized niches. In some cases, these stem cells are deployed for further postnatal development of parts of the brain until the final structure is reached. In other cases, postnatal neurogenesis continues as constitutive neurogenesis into adulthood leading to a net increase of the number of neurons with age. Yet, in other cases, stem cells fuel neuronal turnover. An example is protracted development of the cerebellar granular layer in mammals and birds, where neurogenesis continues for a few weeks postnatally until the granular layer has reached its definitive size and stem cells are used up. Cerebellar growth also provides an example of continued neurogenesis during adulthood in teleosts. Again, it is the granular layer that grows as neurogenesis continues and no definite adult cerebellar size is reached. Neuronal turnover is most clearly seen in the telencephalon of male canaries, where projection neurons are replaced in nucleus high vocal centre each year before the start of a new mating season--circuitry reconstruction to achieve changes of the song repertoire in these birds? In this review, we describe these and other examples of adult neurogenesis in different vertebrate taxa. We also compare the structure of the stem cell niches to find common themes in their organization despite different functions adult neurogenesis serves in different species. Finally, we report on regeneration of the zebrafish telencephalon after injury to highlight similarities and differences of constitutive neurogenesis and neuronal regeneration.

Changes in ultra-structures and electrophysiological properties in HVC of untutored and deafened Bengalese finches relation to normally reared birds: Implications for song learning

Songbirds are increasingly used as an experimentally tractable system to study the neurobiological underpinnings of vocal learning. To gain additional insights into how birdsongs are learned, we compared the size of HVC, the high vocal center for song production, and its ultrastructural or electrophysiological properties between the normally reared Bengalese finches, and the untutored or deafened ones before the onset of sensory learning (around post-hatching day 20). Our results showed that HVC had more synapses and concave synaptic curvature, but fewer perforated synapse, in the untutored or deafened birds in comparison with those in the normally reared birds. Although there was no significant difference of the ratio of straight or compound synapses, there was an increasing tendency for the untutored and deafened birds to possess more straight and compound synapses. These data revealed that synapses in the isolated or deafened birds had lower synapse activity in relation to those with normal hearing. This was confirmed by our electrophysiological results to show significant decreases in the firing rates of spike or burst in the isolated or deafened birds in the three types of HVC neurons i.e., putative X-projecting neurons, RA-projecting neurons and interneurons. In addition, low firing frequency (<10Hz) occurred much more in the above three types of HVC neurons in the tutored or deafened birds than in the normally reared birds. These data suggest that all the three putative types of neurons in HVC might be involved in the activity of the production of adult normal songs.

Morphology of axonal projections from the high vocal center to vocal motor cortex in songbirds

Only birds that learn complex vocalizations have telencephalic brain regions that control vocal learning and production, including HVC (high vocal center), a cortical nucleus that encodes vocal motor output in adult songbirds. HVC projects to RA (robust nucleus of the arcopallium), a nucleus in motor cortex that in turn projects topographically onto hindbrain neurons innervating vocal muscles. Individual neurons projecting from HVC to RA (HVC(RA) ) fire sparsely to drive RA activity during song production. To advance understanding of how individual HVC neurons encode production of learned vocalizations, we reconstructed single HVC axons innervating RA in adult male zebra finches. Individual HVC(RA) axons were not topographically organized within RA: 1) axon arbors of HVC cell bodies located near each other sent branches to different subregions of RA, and 2) branches of single HVC axons terminated in different locations within RA. HVC(RA) axons also had a simple, sparse morphology, suggesting that a single HVC neuron activates a limited population of postsynaptic RA neurons. These morphological data are consistent with previous work showing that single HVC(RA) neurons burst sparsely for a brief period of time during the production of a song, indicating that ensembles of HVC(RA) neurons fire simultaneously to drive small temporal segments of song behavior. We also examined the morphology of axons projecting from HVC to RA cup, a region surrounding RA that receives input from auditory cortex. Axons projecting to RA cup also sent some branches into RA, suggesting direct integration between the sensory and motor circuits for song control.

The Zebra Finch Paradox: Song Is Little Changed, But Number of Neurons Doubles

New neurons are added to the high vocal center (HVC) of adult males in seasonally breeding songbirds such as the canary (Serinus canaria) that learns new songs in adulthood, and the song sparrow (Melospiza melodia) that does not. In both cases, the new neurons numerically replace others that have died, resulting in a seasonal fluctuation in HVC volume and neuron number. Peaks in neuronal replacement in both species occur in the fall when breeding is over and song is variable. New neurons are added, too, to the HVC of zebra finches (Taeniopygia guttata) that do not learn new songs in adulthood and whose song remains stereotyped throughout the year. Here, we show that, in contrast to the observations in seasonal songbirds, neurons added to the zebra finch HVC are not part of a replacement process. Rather, they lead to a doubling in the number of neurons that project from HVC to the robust nucleus of the arcopallium (RA). As this happens, HVC volume remains constant and the packing density of its neurons increases. The HVC-RA neurons are part of a descending pathway that carries the pattern of learned song; some HVC-RA neurons are also responsive to song playback. The addition of HVC-RA neurons happens in zebra finches housed singly, but becomes more acute if the birds are housed communally. We speculate that new neurons added to the adult HVC may help with the production or perception of learned song, or both.

Syntax, synfire, and synaptic plasticity: Modeling the generation of structure in birdsong and neuronal networks

Event Abstract Back to Event Syntax, synfire, and synaptic plasticity: Modeling the generation of structure in birdsong and neuronal networks Abigail Morrison1, 2* 1 Bernstein Center Freiburg, Germany 2 University of Freiburg, Faculty of Biology, Germany Adult Bengalese finches generate a variable song that obeys a distinct and individual syntax. The syntax is gradually lost over a period of days after deafening and is recovered when hearing is restored. In the first part of this talk I will present a spiking neuronal network model of the song syntax generation and its loss, based on the assumption that the syntax is stored in reafferent connections from the auditory to the motor control area. Propagating synfire activity in the HVC (high vocal center) codes for individual syllables of the song and priming signals from the auditory network reduce the competition between syllables to allow only those transitions that are permitted by the syntax. Both imprinting of song syntax within HVC and the interaction of the reafferent signal with an efference copy of the motor command are sufficient to explain the gradual loss of syntax in the absence of auditory feedback. In the second part of this talk I will consider how the synfire chains assumed in the first part could develop. It has long been though that spike-timing dependent plasticity (STDP) provides an answer to the question of how the brain can develop functional structure in response to repeated stimuli. However, convincing demonstrations of this capacity in large, initially random networks have not been forthcoming; such demonstrations as there are typically rely on constraining the problem artificially. I will present a theoretical analysis based on a mean field approach of the development of feed-forward structure in random networks. An unstable fixed point in the recruitment dynamics prevents the stable propagation of structure in recurrent networks with weight-dependent STDP. The key theoretical predictions can be confirmed in large-scale simulations. The theory provides insight into the reasons why such development does not take place in unconstrained systems and enables the identification of candidate biologically motivated adaptations to the balanced random network model that might resolve the issue. Keywords: Plasticity and Learning Conference: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011. Presentation Type: Keynote Topic: other Citation: Morrison A (2011). Syntax, synfire, and synaptic plasticity: Modeling the generation of structure in birdsong and neuronal networks. Front. Comput. Neurosci. Conference Abstract: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011. doi: 10.3389/conf.fncom.2011.53.00021 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Sep 2011; Published Online: 04 Oct 2011. * Correspondence: Prof. Abigail Morrison, Bernstein Center Freiburg, Freiburg, Germany, morrison@fz-juelich.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Abigail Morrison Google Abigail Morrison Google Scholar Abigail Morrison PubMed Abigail Morrison Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.