Hearing - the Brain and Auditory Communication in Marsupials

1 Introduction.- 1.1 Why Study Marsupials?.- 1.2 Evolutionary Considerations.- 1.3 Taxonomic Considerations.- 1.4 Ecological Considerations.- 1.5 The Approach of this Volume.- 2 The Design of the Mammalian Auditory System: A Brief Overview.- 2.1 Structure and Function of the Organ of Corti.- 2.2 Cochlear Potentials.- 2.3 Anatomy of Auditory Nerve and Brainstem.- 2.4 Anatomy of Thalamocortical Auditory System.- 2.4.1 Auditory Cortical Fields.- 2.4.2 Connections of Cortical Fields.- 3 Hearing of Marsupials.- 3.1 Behavioral Measurements.- 3.2 Electrophysiological Measures.- 3.2.1 Cochlear Potential Thresholds.- 3.2.2 Single-Unit Thresholds.- 3.2.3 Auditory Brain Stem Response (ABR).- 3.3 Future Research Directions.- 4 What Do Marsupials Listen To?.- 4.1 Vocalizations and Speech.- 4.2 Vocal Behavior of Adult Marsupials.- 4.3 Hearing Sensitivity and Vocal Spectra of Adults.- 4.4 Adult and Neonatal Hearing and Vocal Relationships.- 4.5 Hearing Sensitivity and the Sounds of Prey and Predators.- 4.6 Future Research Directions.- 5 Auditory Periphery of Marsupials.- 5.1 The Outer Ear.- 5.2 Middle Ear Structures.- 5.2.1 Evolution of Middle Ear Bones.- 5.2.2 Middle Ear of Marsupials.- 5.3 Cochlea.- 5.3.1 Evolution of Sound Reception.- 5.3.2 The Cochlea of Marsupials.- 5.3.3 Cochlear Potentials in Marsupials.- 5.4 Future Research Directions.- 6 Auditory Structures of the Brainstem.- 6.1The Marsupial Brain.- 6.2 Auditory Nuclei of the Medulla.- 6.2.1 Cochlear Nuclear Complex.- 6.2.2 Superior Olivary Complex.- 6.3 The Auditory Midbrain.- 6.3.1 Cytoarchitecture of the Inferior Colliculus.- 6.3.2 Afferent Connections of the Inferior Colliculus.- 6.3.3 Efferents from the Inferior Colliculus.- 6.4 Physiological Studies of the Auditory Midbrain.- 6.4.1 Tonotopic Organization of the Central Nucleus of the Inferior Colliculus and Frequency Selectivity of Single Units.- 6.4.2 Auditory Midbrain and Sound Localization.- 6.4.3 Auditory Midbrain and Acoustic Reflexes.- 6.5 Future Research Directions.- 7 Thalamocortical Auditory System.- 7.1 Medial Geniculate Body.- 7.1.1 Structure.- 7.1.2 Afferent Co0nnections.- 7.1.3 Comparisons with Lateral Geniculate Nucleus (LG) of Marsupials.- 7.2 Evolution of the Neocortex.- 7.3 Auditory Cortical Fields in Marsupials.- 7.4 Auditory 0Cortical Connections of Marsupials.- 7.5 Effects of Lesions of Cortical Areas on Behavior.- 7.6 Future Research Directions.- 8 Development of the Auditory System.- 8.1 Why Marsupials Are Important to the Developmental Biologist.- 8.2 Embryogenesis of the Auditory System and Growth of Young Marsupials.- 8.3 Physiological Measures of the Onset of Hearing in Marsupials.- 8.4 Development of the Auditory Periphery.- 8.4.1 Mechanical Structures.- 8.4.2 Ultrastructural Development of the Cochlea in Eutherians.- 8.4.3 Ultrastructural Development of the Cochlea in Monodelphis.- 8.5 Anatomical Changes in the Brain.- 8.5.1 Cytogenesis, Migration and Formation of Nuclei.- 8.5.2 Development of Dendrites in the Inferior Colliculus.- 8.5.3 Development of Connections and Synapses in the Inferior Colliculus.- 8.5.4 Concerning the Determinants of Synaptogenesis.- 8.6 Future Research Directions.- 9 Conclusions.- 9.1 Hearing Sensitivity.- 9.2 Relationship Between Hearing Range and Vocal Behavior.- 9.3 The Marsupial Auditory Pathway.- References.