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The songbird syrinx morphome: a three-dimensional, high-resolution, interactive morphological map of the zebra finch vocal organ.

Düring DN, Ziegler A, Thompson CK, Ziegler A, Faber C, Müller J, Scharff C, Elemans CP - BMC Biol. (2013)

Bottom Line: Our results show that the syringeal skeleton is optimized for low weight driven by physiological constraints on song production.The present refinement of muscle organization and identity elucidates how apposed muscles actuate different syringeal elements.In addition, we identify a cartilaginous structure suited to play a crucial role in the uncoupling of sound frequency and amplitude control, which permits a novel explanation of the evolutionary success of songbirds.

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Affiliation: Verhaltensbiologie, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.

ABSTRACT

Background: Like human infants, songbirds learn their species-specific vocalizations through imitation learning. The birdsong system has emerged as a widely used experimental animal model for understanding the underlying neural mechanisms responsible for vocal production learning. However, how neural impulses are translated into the precise motor behavior of the complex vocal organ (syrinx) to create song is poorly understood. First and foremost, we lack a detailed understanding of syringeal morphology.

Results: To fill this gap we combined non-invasive (high-field magnetic resonance imaging and micro-computed tomography) and invasive techniques (histology and micro-dissection) to construct the annotated high-resolution three-dimensional dataset, or morphome, of the zebra finch (Taeniopygia guttata) syrinx. We identified and annotated syringeal cartilage, bone and musculature in situ in unprecedented detail. We provide interactive three-dimensional models that greatly improve the communication of complex morphological data and our understanding of syringeal function in general.

Conclusions: Our results show that the syringeal skeleton is optimized for low weight driven by physiological constraints on song production. The present refinement of muscle organization and identity elucidates how apposed muscles actuate different syringeal elements. Our dataset allows for more precise predictions about muscle co-activation and synergies and has important implications for muscle activity and stimulation experiments. We also demonstrate how the syrinx can be stabilized during song to reduce mechanical noise and, as such, enhance repetitive execution of stereotypic motor patterns. In addition, we identify a cartilaginous structure suited to play a crucial role in the uncoupling of sound frequency and amplitude control, which permits a novel explanation of the evolutionary success of songbirds.

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Direct comparison of syringeal soft tissue imaging techniques reveals advantages of μCT. (A) Frontal section of a male zebra finch syrinx prepared with conventional histology and stained with hematoxylin and eosin. Muscles appear as bright red, cartilage as speckled blue/purple. (B) Virtual frontal section through a 3D MRI dataset of a Magnevist-contrasted male zebra finch syrinx with isotropic voxel resolution of 23 μm. (C) Virtual frontal section through a 3D μCT dataset of an iodine-contrasted male zebra finch syrinx with an isotropic voxel resolution of 5 μm. The non-destructiveness, high resolution and relatively short scanning times of contrasted samples made μCT the optimal technique for the construction of the syrinx morphome. (D) Volume rendering of an iodine-contrasted μCT scan. (E-G) Virtual horizontal sections through the 3D μCT dataset at different positions as shown in D. Special effort was made to fix and scan the syrinx in situ, with surrounding tissues remaining intact. Abbreviations as listed in Table 1. Scale bars: 1 mm.
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Figure 6: Direct comparison of syringeal soft tissue imaging techniques reveals advantages of μCT. (A) Frontal section of a male zebra finch syrinx prepared with conventional histology and stained with hematoxylin and eosin. Muscles appear as bright red, cartilage as speckled blue/purple. (B) Virtual frontal section through a 3D MRI dataset of a Magnevist-contrasted male zebra finch syrinx with isotropic voxel resolution of 23 μm. (C) Virtual frontal section through a 3D μCT dataset of an iodine-contrasted male zebra finch syrinx with an isotropic voxel resolution of 5 μm. The non-destructiveness, high resolution and relatively short scanning times of contrasted samples made μCT the optimal technique for the construction of the syrinx morphome. (D) Volume rendering of an iodine-contrasted μCT scan. (E-G) Virtual horizontal sections through the 3D μCT dataset at different positions as shown in D. Special effort was made to fix and scan the syrinx in situ, with surrounding tissues remaining intact. Abbreviations as listed in Table 1. Scale bars: 1 mm.

Mentions: To image soft tissues in 3D at high resolution, we compared results derived from three methods: high-field (17.6 T) MRI with added contrast agent; μCT with two different types of staining; and conventional histology. Figure 6A-C shows a histological section next to two virtual sections through datasets based on MRI and μCT. With classical histology it is rather problematic to construct accurate 3D datasets, because of section alignment inaccuracies as well as unavoidable tissue distortions resulting from fixation, embedding, cutting and staining. The μCT technique provided the highest resolution (5 μm) datasets and was therefore used to generate 3D datasets for further study and annotation. Additional iodine-based staining (see Methods) provided sufficient contrast for unambiguous distinction of all syringeal soft tissues (Figure 6C). We took special care to scan the excised syrinx in situ by leaving all surrounding tissues, such as the lungs, esophagus, crop and large blood vessels, attached and intact (Figure 6D-G).


The songbird syrinx morphome: a three-dimensional, high-resolution, interactive morphological map of the zebra finch vocal organ.

Düring DN, Ziegler A, Thompson CK, Ziegler A, Faber C, Müller J, Scharff C, Elemans CP - BMC Biol. (2013)

Direct comparison of syringeal soft tissue imaging techniques reveals advantages of μCT. (A) Frontal section of a male zebra finch syrinx prepared with conventional histology and stained with hematoxylin and eosin. Muscles appear as bright red, cartilage as speckled blue/purple. (B) Virtual frontal section through a 3D MRI dataset of a Magnevist-contrasted male zebra finch syrinx with isotropic voxel resolution of 23 μm. (C) Virtual frontal section through a 3D μCT dataset of an iodine-contrasted male zebra finch syrinx with an isotropic voxel resolution of 5 μm. The non-destructiveness, high resolution and relatively short scanning times of contrasted samples made μCT the optimal technique for the construction of the syrinx morphome. (D) Volume rendering of an iodine-contrasted μCT scan. (E-G) Virtual horizontal sections through the 3D μCT dataset at different positions as shown in D. Special effort was made to fix and scan the syrinx in situ, with surrounding tissues remaining intact. Abbreviations as listed in Table 1. Scale bars: 1 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539882&req=5

Figure 6: Direct comparison of syringeal soft tissue imaging techniques reveals advantages of μCT. (A) Frontal section of a male zebra finch syrinx prepared with conventional histology and stained with hematoxylin and eosin. Muscles appear as bright red, cartilage as speckled blue/purple. (B) Virtual frontal section through a 3D MRI dataset of a Magnevist-contrasted male zebra finch syrinx with isotropic voxel resolution of 23 μm. (C) Virtual frontal section through a 3D μCT dataset of an iodine-contrasted male zebra finch syrinx with an isotropic voxel resolution of 5 μm. The non-destructiveness, high resolution and relatively short scanning times of contrasted samples made μCT the optimal technique for the construction of the syrinx morphome. (D) Volume rendering of an iodine-contrasted μCT scan. (E-G) Virtual horizontal sections through the 3D μCT dataset at different positions as shown in D. Special effort was made to fix and scan the syrinx in situ, with surrounding tissues remaining intact. Abbreviations as listed in Table 1. Scale bars: 1 mm.
Mentions: To image soft tissues in 3D at high resolution, we compared results derived from three methods: high-field (17.6 T) MRI with added contrast agent; μCT with two different types of staining; and conventional histology. Figure 6A-C shows a histological section next to two virtual sections through datasets based on MRI and μCT. With classical histology it is rather problematic to construct accurate 3D datasets, because of section alignment inaccuracies as well as unavoidable tissue distortions resulting from fixation, embedding, cutting and staining. The μCT technique provided the highest resolution (5 μm) datasets and was therefore used to generate 3D datasets for further study and annotation. Additional iodine-based staining (see Methods) provided sufficient contrast for unambiguous distinction of all syringeal soft tissues (Figure 6C). We took special care to scan the excised syrinx in situ by leaving all surrounding tissues, such as the lungs, esophagus, crop and large blood vessels, attached and intact (Figure 6D-G).

Bottom Line: Our results show that the syringeal skeleton is optimized for low weight driven by physiological constraints on song production.The present refinement of muscle organization and identity elucidates how apposed muscles actuate different syringeal elements.In addition, we identify a cartilaginous structure suited to play a crucial role in the uncoupling of sound frequency and amplitude control, which permits a novel explanation of the evolutionary success of songbirds.

View Article: PubMed Central - HTML - PubMed

Affiliation: Verhaltensbiologie, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.

ABSTRACT

Background: Like human infants, songbirds learn their species-specific vocalizations through imitation learning. The birdsong system has emerged as a widely used experimental animal model for understanding the underlying neural mechanisms responsible for vocal production learning. However, how neural impulses are translated into the precise motor behavior of the complex vocal organ (syrinx) to create song is poorly understood. First and foremost, we lack a detailed understanding of syringeal morphology.

Results: To fill this gap we combined non-invasive (high-field magnetic resonance imaging and micro-computed tomography) and invasive techniques (histology and micro-dissection) to construct the annotated high-resolution three-dimensional dataset, or morphome, of the zebra finch (Taeniopygia guttata) syrinx. We identified and annotated syringeal cartilage, bone and musculature in situ in unprecedented detail. We provide interactive three-dimensional models that greatly improve the communication of complex morphological data and our understanding of syringeal function in general.

Conclusions: Our results show that the syringeal skeleton is optimized for low weight driven by physiological constraints on song production. The present refinement of muscle organization and identity elucidates how apposed muscles actuate different syringeal elements. Our dataset allows for more precise predictions about muscle co-activation and synergies and has important implications for muscle activity and stimulation experiments. We also demonstrate how the syrinx can be stabilized during song to reduce mechanical noise and, as such, enhance repetitive execution of stereotypic motor patterns. In addition, we identify a cartilaginous structure suited to play a crucial role in the uncoupling of sound frequency and amplitude control, which permits a novel explanation of the evolutionary success of songbirds.

Show MeSH
Related in: MedlinePlus