Perineuronal nets in HVC and plasticity in male canary song

peer reviewedSongbirds learn their vocalizations during developmental sensitive periods of song memorization and sensorimotor learning. Some seasonal songbirds, called open-ended learners, recapitulate transitions from sensorimotor learning and song crystallization on a seasonal basis during adulthood. In adult male canaries, sensorimotor learning occurs each year in autumn and leads to modifications of the syllable repertoire during successive breeding seasons. We previously showed that perineuronal nets (PNN) expression in song control nuclei decreases during this sensorimotor learning period. Here we explored the causal link between PNN expression in adult canaries and song modification by enzymatically degrading PNN in HVC, a key song control system nucleus. Three independent experiments identified limited effects of the PNN degradation in HVC on the song structure of male canaries. They clearly establish that presence of PNN in HVC is not required to maintain general features of crystallized song. Some suggestion was collected that PNN are implicated in the stability of song repertoires but this evidence is too preliminary to draw firm conclusions and additional investigations should consider producing PNN degradations at specified time points of the seasonal cycle. It also remains possible that once song has been crystallized at the beginning of the first breeding season, PNN no longer play a key role in determining song structure; this could be tested by treatments with chondroitinase ABC at key steps in ontogeny. It would in this context be important to develop multiple stereotaxic procedures allowing the simultaneous bilateral degradation of PNN in several song control nuclei for extended periods

Role of perineuronal nets in the regulation of sensitive periods for vocal learning in songbirds.

Les oiseaux chanteurs constituent un excellent modèle pour étudier les mécanismes impliqués dans l’apprentissage vocal car, comme l’humain, ils doivent apprendre leurs vocalisations pendant une période sensible, durant laquelle ils sont exposés à un tuteur adulte, pour pouvoir chanter normalement à l’âge adulte. L’apprentissage du chant est rendu possible grâce à la plasticité du cerveau pendant le développement mais aussi à l’âge adulte chez certaines espèces. Dans cette thèse, nous explorons un aspect particulier de cette neuroplastité: les filets périneuronaux (PNN). Bien qu’ils jouent un rôle majeur dans la régulation des périodes sensibles de divers apprentissages, leur rôle dans l’apprentissage vocal était très peu connu. Ce travail a permis de montrer que l’expression des PNN dans le cerveau est impliquée dans l’apprentissage vocal. Nous avons d’abord montré qu’ils se développent dans les régions cérébrales impliquées dans l’apprentissage du chant spécifiquement à la fin de la période de l’apprentissage sensorimoteur du chant chez le canari et le diamant mandarin. Nous avons également montré qu’ils se trouvent systématiquement en plus grande densité et plus grand nombre chez les mâles adultes par rapport aux mâles juvéniles et aux femelles qui ne chantent pas, quelle que soit l’espèce étudiée. Ensuite, nous avons pu montrer que leur diminution à l’âge adulte se produit lors de la modification saisonnière du chant chez le canari. Enfin, nous avons mis en évidence que les différences de densité de PNN entre espèces étaient corrélées avec les capacités d’apprentissage vocal à l’âge adulte

Variations saisonnières et modulation par la testostérone des filets périneuronaux dans le système de contrôle du chant chez les oiseaux chanteurs

Les oiseaux chanteurs sont largement utilisés pour étudier la neuroplasticité induite par l’apprentissage. Non seulement leurs vocalisations nécessitent un apprentissage pendant une période sensible pour être produites normalement à l’âge adulte, mais ils disposent de structures cérébrales spécifiques, appelée le système de contrôle du chant, qui permettent l’apprentissage et la production des chants. Il a été démontré que la plasticité observée dans le système de contrôle du chant évolue au cours du développement des juvéniles pendant la période sensible d’apprentissage du chant mais aussi à l’âge adulte chez les espèces saisonnières qui ont la capacité d’apprendre de nouveaux chants entre chaque saison de reproduction. La production du chant et la plasticité dans le système de contrôle du chant sont principalement influencées par les modifications de la durée d’illumination quotidienne au cours des saisons (la photopériode). Cette influence est souvent le résultat de l’action de la testostérone dans le cerveau. Lors de la saison de reproduction, les testicules des mâles sont plus volumineux et produisent plus de testostérone, ce qui affecte les caractéristiques du chant ainsi que la plasticité du système de contrôle du chant. Bien que cette plasticité ait déjà été beaucoup étudiée, certains marqueurs de la neuroplasticité ont été très peu utilisés chez les oiseaux chanteurs; c’est le cas notamment des PNN se trouvant le plus souvent autour des interneurones GABAergiques exprimant la parvalbumine. Il a déjà été démontré que ceux-ci étaient liés aux apprentissages sensoriels chez les mammifères. Tandis que la parvalbumine apparaît progressivement au cours du développement du cerveau, les PNN ne sont complètement formés qu’à la fin des périodes sensibles d’apprentissage dans les aires cérébrales correspondantes. Ces PNN associés à la parvalbumine sont donc des indicateurs de la neuroplasticité particulièrement intéressants à étudier chez les oiseaux chanteurs chez qui l’apprentissage du chant dépend également des expériences sensorielles. Ils ont été étudiés dans quelques expériences avec des diamants mandarins (espèce non-saisonnière), mais jamais chez des espèces saisonnières. C’est pourquoi nous avons choisi de réaliser notre travail de fin d’étude dans ce domaine de recherches encore inexploré

Sex differences in perineuronal nets and parvalbumin expression in the zebra finch (taeniopygia guttata) song system.

Songbirds including zebra nches (Taeniopygia guttata) have been widely used as a model for studying vocal learning and the associated neural plasticity. Recently, two neural markers for critical periods in brain plasticity were suggested to be related to song learning in males: parvalbumin (PV) expression would be associated with the onset of experience-dependent plasticity whereas perineuronal nets (PNN, chondroitin sulfate proteoglycans surrounding neurons) would limit potential plasticity at the end of sensitive phases (Balmer et al., 2009). Here we explored sex differences in PNN in the zebra finch song system

Comparing perineuronal nets and parvalbumin development between black bird species with differences in early developmental song exposure

Brood parasitic songbirds are a natural system in which developing birds are isolated from species-typical song and therefore present a unique opportunity to compare neural plasticity in song learners raised with and without conspecific tutors. We compared perineuronal nets (PNN) and parvalbumin (PV) in song control nuclei in juveniles and adults of two closely related icterid species (i.e. blackbirds): brown-headed cowbirds (Molothrus ater; brood parasite) and red-winged blackbirds (Agelaius phoeniceus; non-parasite). The number of PV cells per nucleus was significantly higher in adults compared with juveniles in the nucleus HVC and the robust nucleus of the arcopallium (RA), whereas no significant species difference appeared in any region of interest. The number of PNN per nuclei was significantly higher in adults compared with juveniles in HVC, RA and Area X, but only RA exhibited a significant difference between species. PV cells surrounded by PNN (PV+PNN) also exhibited age-related differences in HVC, RA and Area X, but RA was the only region in which PV+PNN exhibited significant species differences. Furthermore, a significant interaction existed in RA between age and species with respect to PNN and PV+PNN, revealing RA as a region displaying differing plasticity patterns across age and species. Additional comparisons of PNN and PV between adult male and female cowbirds revealed that males have greater numbers of all three measures in RA compared with females. Species-, sex- and age-related differences in RA suggest that species differences in neural plasticity are related to differences in song production rather than sensitivity to song learning, despite a stark contrast in early exposure to conspecific male tutors

Seasonal changes of perineuronal nets and song learning in adult canaries (Serinus canaria)

peer reviewedSongbirds learn their song during a sensitive period of development associated with enhanced neural plasticity. In addition, in open-ended learners such as canaries, a sensitive period for sensorimotor vocal learning reopens each year in the fall and leads to song modifications between successive breeding seasons. The variability observed in song production across seasons in adult canaries correlates with seasonal fluctuations of testosterone concentrations and with morphological changes in nuclei of the song control system (SCS). The sensitive periods for song learning during ontogeny and then again in adulthood could be controlled by the development of perineuronal nets (PNN) around parvalbumin-expressing interneurones (PV) which limits learning-induced neuroplasticity. However, this relationship has never been investigated in the context of adult vocal learning in adult songbirds. Here we explored PNN and PV expression in the SCS of adult male Fife Fancy canaries in relation to the seasonal variations of their singing behaviour. We found a clear pattern of seasonal variation in testosterone concentrations and song production. Furthermore, PNN expression was significantly higher in two specific song control nuclei, the robust nucleus of the arcopallium (RA) and the Area X of the basal ganglia, during the breeding season and during the later stages of sensorimotor song development compared to birds in an earlier stage of sensorimotor development during the fall. These data provide the first evidence that changes in PNN expression could represent a mechanism regulating the closing-reopening of sensitive periods for vocal learning across seasons in adult songbird

The fuzzy-logic control of active suspensions without suspension-gap degeneration

V tem prispevku uporabljamo model vozila s štirimi prostostnimi stopnjami z željo, da načrtamo in preverimo zmogljivosti aktivnega vzmetenja, ki ga logično mehko krmilimo, ne da bi kakorkoli zmanjšali delovno področje vzmetenja. Težnja k ničnemu premiku vzmetene mase utegne izničiti delovno razdaljo vzmetenja. Zato v tej raziskavi predlagamo nov pristop. Silostne izvršilnike vgradimo vzporedno z vzmetenjem. Osnovna zamisel, da predlagamo logično mehki krmilnik, izhaja iz dejstva, da je uspesen, iz moznosti, da taksen krmilnik uporabimo v vozilnih sistemih in iz moznosti, da s pomočjo logično mehkega algoritma premagamo upadanje zračnosti vzmetenja.Udobnost vožnje izboljšamo, tako da znižamo velikost gibov karoserije vozila. Poskakovanje karoserije in zibanje vozila modeliramo tako v časovnem (v primeru potovanja po nagnjeni stopničasti poti) kot v frekvenčnem prostoru. Rezultate simulacije primerjamo z rezultati pasivnega vzmetenja. Na koncu raziskave razpravljamo o zmogljivosti krmilnika s stalisča udobnosti voznje, o prednosti predlaganega pristopa in o izboljšanju zmogljivosti sistema.In this paper a four-degrees-of-freedom vehicle model is used in order to design and check the performance of fuzzy-logic-controlled (FLC) active suspensions without causing any degeneration in the suspensions\u27 working limits. Aiming at a zero displacement for a sprung mass might finish the suspensionsć working distance. Therefore, in this paper a new approach is proposed. The force actuators are mounted parallel to the suspensions. The main idea behind proposing a fuzzy-logic controller is its success, the ability to use these types of controllers on vehicle systems and the ability to overcome the suspension-gap degeneration problem within the fuzzy-control algorithm. The improvement in the ride comfort is achieved by decreasing the amplitudes of the motions of the vehicle body. The body bounce and the pitch motions of the vehicle are simulated in both the time domain, in the case of travelling over a ramp-step road profile, and in the frequency domain. The simulation results are compared with the results from passive suspensions. At the end of the paper , the performance of the controller, the advantage of theproposed approach and the improvement in the system performance are discussed in terms of the ride comfort

Testosterone stimulates perineuronal nets development around parvalbumin cells in the adult canary brain in parallel with song crystallization.

Perineuronal nets (PNN) of the extracellular matrix are dense aggregations of chondroitin-sulfate proteoglycans that usually surround fast-spiking parvalbumin-expressing inhibitory interneurons (PV). The development of PNN around PV appears specifically at the end of sensitive periods of visual learning and limits the synaptic plasticity in the visual cortex of mammals. Seasonal songbirds display a high level of adult neuroplasticity associated with vocal learning, which is regulated by fluctuations of circulating testosterone concentrations. Seasonal changes in testosterone concentrations and in neuroplasticity are associated with vocal changes between the non-breeding and breeding seasons. Increases in blood testosterone concentrations in the spring lead to the annual crystallization of song so that song becomes more stereotyped. Here we explore whether testosterone also regulates PNN expression in the song control system of male and female canaries. We show that, in both males and females, testosterone increases the number of PNN and of PV neurons in the three main telencephalic song control nuclei HVC, RA (nucleus robustus arcopallialis) and Area X and increases the PNN localization around PV interneurons. Singing activity was recorded in males and quantitative analyses demonstrated that testosterone also increased male singing rate, song duration and song energy while decreasing song entropy. Together, these data suggest that the development of PNN could provide the synaptic stability required to maintain the stability of the testosterone-induced crystallized song. This provides the new evidence for a role of PNN in the regulation of adult seasonal plasticity in seasonal songbird

Correlation between song learning and perineuronal nets development in song control system nuclei of juvenile canaries

Perineuronal nets (PNN) are aggregations of extracellular matrix components surrounding the soma of specific neurons, mainly GABAergic interneurons expressing the calcium binding protein parvalbumin (PV+). In mammals, the development of PNN limits synaptogenesis around PV+ neurons and PNNs have been identified as a marker of the end of sensitive periods for brain plasticity in several neuronal systems. In songbirds, vocal learning requires exposure to conspecific vocalizations by male tutors during a sensitive period. This is followed by a sensorimotor period when birds progressively match their vocalizations with the memorized tutor’s song until the fully mature song is crystallized. In a closed-ended learner, the zebra finch, PNN expression in select song nuclei is higher in males than in females and higher in adults than in juvenile males. The timing of PNN appearance in the developing zebra finch brain correlates with the timing of sensitive periods for song learning. We also showed that PNN are more densely expressed in the song control system of zebra finches than in two open-ended learners, the European starling and the canary and that testosterone (T) induces song crystallization in early spring and increases the number of PNN in castrated canaries. Together these data suggest that PNN might regulate the end of the sensitive period(s) for vocal learning during ontogeny. To elucidate this question further, we quantified PNN expression at critical time points during the first year of life in canaries and correlated these data with their song development. Brains were collected from groups of males (n=6-8/group) at time points corresponding to specific vocal developmental stages: first spring (subsong), summer (early plastic song), fall (plastic song), winter (ongoing song crystallization), and second spring (fully crystallized song/adults). In winter, one additional group received T implants to test whether this accelerates PNN development and song crystallization. The number of PNN reached their maximum in the fall in HVC but only in the winter in RA and Area X. In the group treated with T there was no further enhancement of PNN expression over what was observed in untreated birds at the same age. Total song duration and song developmental score only reached their maximum in the spring and were enhanced by T in the winter. Other song characteristics such as the energy or bandwidth were already at the adult levels during the winter. Most of these song measurements correlated with the number of PNN in the song nuclei suggesting that PNN contribute to song crystallization that starts in the winter and is completed at the onset of spring

Data from: Timing of perineuronal nets development in the zebra finch song control system correlates with developmental song learning

The appearance of perineuronal nets (PNN) represents one of the mechanisms that contribute to the closing of sensitive periods for neural plasticity. This relationship has mostly been studied in the ocular dominance model in rodents. Previous studies also indicated that PNN might control neural plasticity in the song control system (SCS) of songbirds. To further elucidate this relationship, we quantified PNN expression and their localization around parvalbumin interneurons at key time-points during ontogeny in both male and female zebra finches and correlated these data with the well-described development of song in this species. We also extended these analyses to the auditory system. The development of PNN during ontogeny correlated with song crystallization although the timing of PNN appearance in the four main telencephalic song control nuclei slightly varied between nuclei in agreement with the established role these nuclei play during song learning. Our data also indicate that very few PNN develop in the secondary auditory forebrain areas even in adult birds, which may allow constant adaptation to a changing acoustic environment by allowing synaptic reorganization during adulthood