reflected in the motor output system as well. Many studies of motor output
have focused on how the morphology of the vocal apparatus limits the types
of signals that can be produced (Bass and Clark, Chapter 2; Fitch and
Hauser, Chapter 3). Fitch and Hauser describe how the morphological
diversity of vocal tracts in nonaquatic vertebrates is related to the types of
signals used in different environments and for different communicative
functions. Using an ontogenetic perspective, Boughman and Moss (Chapter
4) describe how body morphology influences the structure and development of vocalizations over an animal’s lifetime. Yamaguchi and Kelley
(Chapter 6) analyze vocal production from a mechanistic perspective, focusing on the influence of gonadal hormones on the vocal organs. Finally,
responses of motor output cells in the central auditory and vocal systems
of the songbird, and how these are related to sensory processing mechanisms, are examined by Gentner and Margoliash (Chapter 7).
3. Future Directions
Neuroethological studies of acoustic communication have generated
insights into behavior on proximate and ultimate levels. However, much
remains to be done before a complete, integrated analysis of sound communication is achieved in any species. We know a great deal about certain
aspects of communication in particular species, but very little is known in
others. For example, links between production and perception are best
understood in some species of orthopteran insects and oscine birds but are
much less well-studied in other vocalizing species. This is partially due to
the neuroethological reliance on popular model systems (songbirds, frogs,
bats) while ignoring other animals (most mammals) that also use sounds
for communication. This limits the generalizability of the neuroethological
approach and opens the work to criticisms that it applies only to highly specialized or unusual animals.
3.1. Neural Processing Mechanisms
On the proximate level, much of our knowledge of perceptual mechanisms
remains at the level of the receptor organs and their direct neural innervation. The basic structure and response properties of the auditory periphery
in relation to sound communication have been described in a variety of
species. With several exceptions (Gentner and Margoliash, Chapter 7),
much less is known about responses of central auditory neurons to complex
communication signals. A great deal of our knowledge of central response
properties in the vertebrate brain is based on experiments in which spike
activity is recorded to pure tones presented in isolation or in two-tone pairs.
These stimulus conditions, although essential for parametric control and
basic descriptions of response properties, do not mimic the conditions under
1. Acoustic Communication
9
have focused on how the morphology of the vocal apparatus limits the types
of signals that can be produced (Bass and Clark, Chapter 2; Fitch and
Hauser, Chapter 3). Fitch and Hauser describe how the morphological
diversity of vocal tracts in nonaquatic vertebrates is related to the types of
signals used in different environments and for different communicative
functions. Using an ontogenetic perspective, Boughman and Moss (Chapter
4) describe how body morphology influences the structure and development of vocalizations over an animal’s lifetime. Yamaguchi and Kelley
(Chapter 6) analyze vocal production from a mechanistic perspective, focusing on the influence of gonadal hormones on the vocal organs. Finally,
responses of motor output cells in the central auditory and vocal systems
of the songbird, and how these are related to sensory processing mechanisms, are examined by Gentner and Margoliash (Chapter 7).
3. Future Directions
Neuroethological studies of acoustic communication have generated
insights into behavior on proximate and ultimate levels. However, much
remains to be done before a complete, integrated analysis of sound communication is achieved in any species. We know a great deal about certain
aspects of communication in particular species, but very little is known in
others. For example, links between production and perception are best
understood in some species of orthopteran insects and oscine birds but are
much less well-studied in other vocalizing species. This is partially due to
the neuroethological reliance on popular model systems (songbirds, frogs,
bats) while ignoring other animals (most mammals) that also use sounds
for communication. This limits the generalizability of the neuroethological
approach and opens the work to criticisms that it applies only to highly specialized or unusual animals.
3.1. Neural Processing Mechanisms
On the proximate level, much of our knowledge of perceptual mechanisms
remains at the level of the receptor organs and their direct neural innervation. The basic structure and response properties of the auditory periphery
in relation to sound communication have been described in a variety of
species. With several exceptions (Gentner and Margoliash, Chapter 7),
much less is known about responses of central auditory neurons to complex
communication signals. A great deal of our knowledge of central response
properties in the vertebrate brain is based on experiments in which spike
activity is recorded to pure tones presented in isolation or in two-tone pairs.
These stimulus conditions, although essential for parametric control and
basic descriptions of response properties, do not mimic the conditions under
1. Acoustic Communication
9