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See detailPerineuronal nets and song learning-related neuroplasticity in the songbird brain
Cornez, Gilles ULg; Jonckers, Elisabeth; Schevchouk, Olesya et al

Conference (2017, May 22)

Perineuronal nets (PNN) are aggregations of extracellular matrix components surrounding the soma of some neurons, mainly GABAergic interneurons expressing the calcium binding protein parvalbumin (PV+). In ... [more ▼]

Perineuronal nets (PNN) are aggregations of extracellular matrix components surrounding the soma of some neurons, mainly GABAergic interneurons expressing the calcium binding protein parvalbumin (PV+). In mammals, the development of PNN limits synaptogenesis around PV+ neurons and PNN have been validated as a marker characterizing the end of critical periods for visual learning. In songbirds, song learning is limited to critical periods during ontogeny in close-ended learners such as zebra finches and to specific phases of the annual cycle in open-ended learners such as canaries that are able to modify their song seasonally. Sensitive periods for song learning are associated with neuroplasticity including morphological changes due to neurogenesis and synaptic reorganization in the song control nuclei during development and adult seasonal song modifications. The hormonal control of developmental and seasonal neuroplasticity is well documented in songbirds but little is known about the possible regulation of sensitive periods for vocal learning by PNN. First, to explore the expression of PNN throughout the development, we used zebra finches brains collected at different key ages in the song learning process (10, 20, 30, 40, 50, 60, 90, 120 days post-hatch, dph) and we quantified PNN expression and their colocalization around PV+ interneurons. The number of PNN and the % of PNN around PV+ interneurons increased progressively during developmental song learning in 3 of the main song control nuclei (HVC, RA and Area X). Moreover, we confirmed that females that never sing have fewer PNN than males in HVC and RA, two song nuclei involved in song production, at all ages after the peak in PNN numbers seen in males between 50 and 90 dph. Secondly we used adult male and female canaries (in 2 different experiments) treated with a subcutaneous implant filled with testosterone or left empty in control subjects to mimic what happens in the spring when the seasonal modification of the song ends and the song crystallizes. Testosterone significantly increased the number of PNN in the main song control nuclei in both sexes. Together these data suggest that increased expression of PNN in the songbird brain might limit neuroplasticity at the end of developmental and seasonal vocal learning [less ▲]

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See detailTopography and Lateralized Effect of Acute Aromatase Inhibition on Auditory Processing in a Seasonal Songbird
de groof, Geert; Balthazart, Jacques ULg; Cornil, Charlotte ULg et al

in Journal of Neuroscience (2017), 37(16), 4243-4254

It is increasingly recognized that brain-derived estrogens (neuroestrogens) can regulate brain physiology and behavior much faster than what was previously known from the transcriptional action of ... [more ▼]

It is increasingly recognized that brain-derived estrogens (neuroestrogens) can regulate brain physiology and behavior much faster than what was previously known from the transcriptional action of estrogens on nuclear receptors. One of the best examples of such neuro- modulation by neuroestrogens concerns the acute regulation of sensory coding by the auditory cortex as demonstrated by electrophys- iological studies of selected neurons in zebra finches. Yet, the spatial extent of such modulation by neuroestrogens is not known. Using functional magnetic resonance imaging, we demonstrate here that acute estrogen depletion alters within minutes auditory processing in male European starlings. These effects are confined to very specific but large areas of the auditory cortex. They are also specifically lateralized to the left hemisphere. Interestingly, the modulation of auditory responses by estrogens was much larger (both in amplitude and in topography) in March than in December or May/June. This effect was presumably independent from changes in circulating testosterone concentrations since levels of the steroid were controlled by subcutaneous implants, thus suggesting actions related to other aspects of the seasonal cycle or photoperiodic manipulations. Finally, we also show that estrogen production specifically modulates selectivity for behaviorally relevant vocalizations in a specific part of the caudomedial nidopallium. These findings confirm and extend previous conclusions that had been obtained by electrophysiological techniques. This approach provides a new very powerful tool to investigate auditory responsiveness in songbirds and its fast modulation by sex steroids. [less ▲]

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See detailSeasonal changes and steroid control of perineuronal nets in the song control system
Cornez, Gilles ULg; Shevchouk, Olesya ULg; Madison, Farrah et al

Conference (2016, October 14)

Perineuronal nets (PNNs) are aggregations of extracellular matrix components surrounding the soma of some neurons, mainly GABAergic interneurons expressing the calcium binding protein parvalbumin (PV ... [more ▼]

Perineuronal nets (PNNs) are aggregations of extracellular matrix components surrounding the soma of some neurons, mainly GABAergic interneurons expressing the calcium binding protein parvalbumin (PV+). In mammals, the development of PNNs limits synaptogenesis around PV+ neurons and PNNs have been validated as a marker characterizing the end of critical periods for some types of learning. In oscines, song learning is limited to critical periods either during ontogeny in close-ended learners such as zebra finches or during specific phases of the annual cycle in open-ended learners such as canaries or starlings. In zebra finches, PNN expression increases when the song crystalizes and this increase is markedly inhibited if juveniles are deprived from a tutor, which is known to delay the closure of the critical period for song learning. Nothing is known however about a possible role of PNNs in adult seasonal plasticity of open-ended learners. We compared PNNs expression and their colocalization with PV+ neurons in photosensitive, photostimulated, and photorefractory starlings. Although this treatment affected as expected the testes volumes, testosterone concentrations and volumes of song control nuclei, it did not markedly change the expression of PNNs or PV+ neurons in song control or auditory nuclei. In a second experiment, brains of female canaries implanted with testosterone for 1, 2, 9, or 21 days displayed an increase of the total numbers of PV+ neurons and PNNs in HVC, the total number of PNNs in nucleus robustusarcopallialis (RA), the density of PNNs in Area X and the %PV+ neurons surrounded by PNNs in RA and Area X. Interestingly the density of PNNs in song control nuclei progressively decreases from zebra finches to canaries to starlings in parallel with the increased song plasticity in these species supporting the notion that PNNs may limit brain and thus song plasticity in a species-typical manner. [less ▲]

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See detailOwn song selectivity in the songbird auditory pathway: Suppression by norepinephrine
Poirier, Colline; Boumans, Tiny; Vellema, Michiel et al

in PLoS ONE (2011), 6(5), 20131

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See detailOwn song selectivity in the songbird auditory pathway: suppression by norepinephrine
Poirier, Colline; Boumans, Tiny; Vellema, Michiel et al

Poster (2010)

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See detailOwn-song recognition in the songbird auditory pathway: selectivity and lateralization.
Poirier, Colline; Boumans, Tiny; Verhoye, Marleen et al

in Journal of Neuroscience (2009), 29(7), 2252-8

The songbird brain is able to discriminate between the bird's own song and other conspecific songs. Determining where in the brain own- song selectivity emerges is of great importance because experience ... [more ▼]

The songbird brain is able to discriminate between the bird's own song and other conspecific songs. Determining where in the brain own- song selectivity emerges is of great importance because experience-dependent mechanisms are necessarily involved and because brain regions sensitive to self-generated vocalizations could mediate auditory feedback that is necessary for song learning and maintenance. Using functional MRI, here we show that this selectivity is present at the midbrain level. Surprisingly, the selectivity was found to be lateralized toward the right side, a finding reminiscent of the potential right lateralization of song production in zebra finches but also of own-face and own-voice recognition in human beings. These results indicate that a midbrain structure can process subtle information about the identity of a subject through experience-dependent mechanisms, challenging the classical perception of subcortical regions as primitive and nonplastic structures. They also open questions about the evolution of the cognitive skills and lateralization in vertebrates. [less ▲]

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See detailA three-dimensional MRI atlas of the zebra finch brain in stereotaxic coordinates.
Poirier, Colline; Vellema, Michiel; Verhoye, Marleen et al

in NeuroImage (2008), 41(1), 1-6

The neurobiology of birdsong, as a model for human speech, is a fast growing area of research in the neurosciences and involves electrophysiological, histological and more recently magnetic resonance ... [more ▼]

The neurobiology of birdsong, as a model for human speech, is a fast growing area of research in the neurosciences and involves electrophysiological, histological and more recently magnetic resonance imaging (MRI) approaches. Many of these studies require the identification and localization of different brain areas (nuclei) involved in the sensory and motor control of song. Until now, the only published atlases of songbird brains consisted in drawings based on histological slices of the canary and of the zebra finch brain. Taking advantage of high-magnetic field (7 Tesla) MRI technique, we present the first high-resolution (80 x 160 x 160 microm) 3-D digital atlas in stereotaxic coordinates of a male zebra finch brain, the most widely used species in the study of birdsong neurobiology. Image quality allowed us to discern most of the song control, auditory and visual nuclei. The atlas can be freely downloaded from our Web site and can be interactively explored with MRIcro. This zebra finch MRI atlas should become a very useful tool for neuroscientists working on birdsong, especially for co-registrating MRI data but also for determining accurately the optimal coordinates and angular approach for injections or electrophysiological recordings. [less ▲]

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See detailSeasonal rewiring of the songbird brain: an in vivo MRI study.
De Groof, Geert; Verhoye, Marleen; Van Meir, Vincent et al

in European Journal of Neuroscience (2008), 28(12), 2475-852474

The song control system (SCS) of songbirds displays a remarkable plasticity in species where song output changes seasonally. The mechanisms underlying this plasticity are barely understood and research ... [more ▼]

The song control system (SCS) of songbirds displays a remarkable plasticity in species where song output changes seasonally. The mechanisms underlying this plasticity are barely understood and research has primarily been focused on the song nuclei themselves, largely neglecting their interconnections and connections with other brain regions. We investigated seasonal changes in the entire brain, including the song nuclei and their connections, of nine male starlings (Sturnus vulgaris). At two times of the year, during the breeding (April) and nonbreeding (July) seasons, we measured in the same subjects cellular attributes of brain regions using in vivo high-resolution diffusion tensor imaging (DTI) at 7 T. An increased fractional anisotropy in the HVC-RA pathway that correlates with an increase in axonal density (and myelination) was found during the breeding season, confirming multiple previous histological reports. Other parts of the SCS, namely the occipitomesencephalic axonal pathway, which contains fiber tracts important for song production, showed increased fractional anisotropy due to myelination during the breeding season and the connection between HVC and Area X showed an increase in axonal connectivity. Beyond the SCS we discerned fractional anisotropy changes that correlate with myelination changes in the optic chiasm and axonal organization changes in an interhemispheric connection, the posterior commissure. These results demonstrate an unexpectedly broad plasticity in the connectivity of the avian brain that might be involved in preparing subjects for the competitive and demanding behavioral tasks that are associated with successful reproduction. [less ▲]

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See detailRapid testosterone-induced apparent diffusion coefficient (ADC) changes in the sexually dimorphic medial preoptic nucleus of male Japanese quail.
Van Der Linden, Annemie; De Groof, Geert; Charlier, Thierry ULg et al

Poster (2006)

Testosterone (T) influences the volume and cellular characteristics of a variety of steroid-dependent brain nuclei in many vertebrates. In castrated quail, the volume of the sexually dimorphic (males ... [more ▼]

Testosterone (T) influences the volume and cellular characteristics of a variety of steroid-dependent brain nuclei in many vertebrates. In castrated quail, the volume of the sexually dimorphic (males > females) medial preoptic nucleus (POM), a key area in the control of male sexual behavior, is markedly increased by T but previous studies always assessed this effect after a period of 8-14 days and its specific time-course was unknown. We recently found that following treatment with T, the POM volume increases in a time-dependent fashion: a significant increase was already detected after only one day and the response reached it maximum (volume doubling) after 14 days of treatment. This however raised the question of the cellular mechanism underlying such a rapid brain plasticity (increase in cell size, neuropil volume, dendritic branching, extracellular space?). To research whether a change in extra- vs. intra-cellular space could be responsible for the rapid T-induced increase in POM volume, we repeatedly analyzed by in vivo diffusion-weighted magnetic resonance imaging (DW-MRI) the brain of castrated male quail before as well as after 1, 2, 7 and 14 days of T implantation. MRI was performed on a 7T-system (Bruker) using a multislice diffusion weighted-spin echo sequence. Coronal slices with an image resolution of 100*100*500µm³ were obtained covering the whole telencephalon. Images were accurately coregistered allowing voxel-wise paired comparisons of the ADC data between the different time periods. The ADC significantly increased after one day of T treatment (696±16 vs 758±30 µm²/s, p=0.011, N=5) in POM and this effect apparently persisted during the whole experiment. By contrast, T insensitive regions like the nucleus rotundus (586±170 vs 511±26 µm²/s, p-value=0.24) and nucleus mesencephalicus lateralis, pars dorsalis (934±107 vs 911±64 µm²/s, p=0.68) were not affected after the first day nor later in the experiment. These data indicate that T increases the extracellular water volume in POM specifically, either as a result of cell shrinkage or of an increase in the space between cells, and that changes in the ratio of extra- to intra-cellular water mediate, at least in part, the fast plasticity of the POM volume observed after exposure to T. [less ▲]

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