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Selective Tracing of Auditory Fibers in the Avian Embryonic Vestibulocochlear Nerve
Published on: March 18, 2013
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Evolution of mammalian sound localization circuits: A developmental perspective.
1Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany; Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany.
Progress in Neurobiology
|April 2, 2016
Summary
Mammals evolved specialized high-frequency sound localization neurons from common ancestral cells. These VGlut2(+) neurons in the brainstem show homologous development, aiding 3D sound detection.
Area of Science:
- Neuroscience
- Evolutionary Biology
- Auditory Processing
Background:
- Mammalian high-frequency (HF) hearing above 10kHz is unique and likely drove the evolution of new sound localization mechanisms.
- The central auditory system's adaptation to these HF changes remains unclear.
Purpose of the Study:
- To propose that key excitatory projection neurons in sound localization circuits are homologous structures (paramorphs) with modifications.
- To explore the evolutionary origins and convergence of sound localization circuits across vertebrates.
Main Methods:
- Comparative analysis of embryonic origin, cell birth, morphology, genetic components (Lhx2, Lhx9), and projection patterns of VGlut2(+) neurons.
- Review of genetic analyses of auditory nuclei contributions from progenitor lineages in fish, birds, and mammals.
Main Results:
- VGlut2(+) excitatory projection neurons in the dorsal cochlear nucleus (DCN), lateral superior olive (LSO), and medial superior olive (MSO) share a common embryonic origin and developmental features.
- These neurons are proposed as serial homologs, suggesting a parsimonious evolutionary path for 3D sound localization.
- While progenitor lineages are conserved, independent evolution of auditory systems suggests convergent circuit evolution in tetrapods.
Conclusions:
- The VGlut2(+) neurons in mammalian sound localization circuits likely evolved through modification of homologous precursors.
- Convergent evolution shaped sound localization circuits in tetrapods, facilitated by hindbrain genetic architecture.
- Further research into vertebrate auditory neuron development is needed to fully understand neuronal homology and convergent evolution.
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