ISSN:0006-8977    

DOI:10.1159/000118686

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000118687

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

A neuroeffector pathway for communication consists of at least two elements: a peripheral effector organ and a central motor nucleus. Two communication systems are discussed here: the sonic motor and electromotor systems of fish. The electromotor system is used to illustrate species diversity of a peripheral effector, the electric organ. The sonic motor system is discussed in the context of species differences in the organization of a central motor nucleus for communication. Both systems share several anatomical and physiological features related to the generation of a stereotyped communication signal. Moreover, both systems appear to be sensitive to the influences of gonadal steroid hormones in the development of sexually dimorphic communication signals.

ISSN:0006-8977    

DOI:10.1159/000118688

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Sex differences in the neural song system in oscine song birds develop in response to estradiol secreted during early periods of development. Estradiol produces sex differences in cell number and in the proportion of cells which are steroid targets. The pattern of development of these sex differences varies in different brain regions, suggesting that the mechanisms of estradiol regulation of neural development may also vary. The magnitude of sexual dimorphism in the neural song system varies across species, and is generally correlated with the magnitude of sexual dimorphism in vocal ability. Large species differences in neural structure can potentially be explained by small differences in the ontogenetic pattern of estradiol secretion, as is suggested by studies of neural development.

ISSN:0006-8977    

DOI:10.1159/000118689

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Animal communication in any sensory modality is influenced by environmental constraints on signal transmission and detection. Acoustic signals are subject to frequency-dependent attenuation, temporal degradation, and masking by environmental noise; these factors constrain the spectral and temporal structures of long-range sound signals. Signals produced by electric fish are largely free of such physical environmental constraints on their spectral and temporal structures, but experience severe attenuation due to geometrical spreading. This effectively limits electric communication to short ranges, whereas acoustic signals are more flexible in the range over which they are effective.

ISSN:0006-8977    

DOI:10.1159/000118690

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Acoustic and electric communication differ in one important respect: while acoustic communication signals propagate through air or water as a wave, electric signals do not propagate, but exist instead as electrostatic fields. As a result of propagation, acoustic signals are distorted during transmission in a largely unpredictable way. Sound receivers, therefore, may not be able to recognize fine details in the waveform of an acoustic signal, but may have to rely instead upon time intervals between repetitions of a waveform, on the frequency of a signal, or on frequency modulations. By contrast, non-propagating electric communication signals are immune to many sources of signal distortion that affect sounds. Consequently, electric signal receivers may reliably use waveform cues to recognize a sender''s identity and discriminate between signals. As examples, mormyrid electric fish encode species and sex differences in the fine structure of the electric organ discharge waveform and sense the differences using temporal cues. Gymnotiform pulse-discharging electric fish may employ scan-sampling for waveform analysis: a specialized mechanism analogous to a digital sampling oscilloscope for slowly scanning a repetitive waveform.

ISSN:0006-8977    

DOI:10.1159/000118691

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Repetitive spontaneous calling in frogs and electric signalling in pulse-type electric fishes are driven by neural pacemakers. Minimization of signal overlap between neighbors is achieved in frogs and certain electric fishes by mutual entrainment, requiring cycle-by-cycle adjustment of pacemaker interval. Other fishes, which require a regular electric organ discharge, are more constrained in their ability to avoid jamming. Entrainment may also serve to reciprocally place signals in a temporal ''blindspot'' of the receiver, the period of elevated sensory threshold following signal production, to reduce aggressive interactions.

ISSN:0006-8977    

DOI:10.1159/000118692

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Numerous studies have investigated selective forces that appear to influence the evolution of acoustic communication systems. I review a number of constraints on evolution in these systems. A species'' history is of undeniable importance in the analysis of any trait. However, studies have given little or no attention to phylogenetic patterns of acoustic signals. This precludes the identification of phylogenetic constraints, and should be viewed as a serious constraint on our ability to understand how communication systems evolve. Morphological constraints influence the energetic efficiency of acoustic communication. To maximize transmission distance of signals used in long-range communication, the animal''s morphology favors signals with high frequencies. Thus morphology acts in opposition to properties of the environment, which favor low frequencies for use in long-range communication. Sensory receptors also play an important role in the evolution of acoustic signals. There is significant variation in the frequency range to which an inner-ear organ of the frog is sensitive. Different lineages of frogs are characterized by ear organs with different ranges of sensitivity. This variation should influence the frequency range over which calls evolved and, as a consequence, might have influenced the rate at which different lineages of anurans speciate.

ISSN:0006-8977    

DOI:10.1159/000118693

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Sexual differences in receptor tuning are found in the auditory system in at least two species of anuran amphibians and are common in electric fish. Since the boundary of a communication signal''s active space is defined in terms of the sensitivity of the receptors to that signal, such sexual differences might result in active-space differences between males and females. In spring peepers, the sexual difference in the auditory system clearly results in a significantly larger active space in females. Among electric fish, however, sexual differences in the spectral tuning of the electroreceptors may not always result in sexual differences in active space.

ISSN:0006-8977    

DOI:10.1159/000118694

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

This presentation reviews behavioral and physiological evidence suggesting that the perceived power spectrum of a sound, as modified by the external ears, provides important cues for horizontal and vertical sound localization. This spatial information is mostly likely encoded by the relative levels of excitation among the tonotopically organized hair cells of the cochlea. This suggests that the preservation of the cochlear frequency map within the central auditory system contributes an anatomical substrate for the localization of sound.

ISSN:0006-8977    

DOI:10.1159/000118695

出版商:S. Karger AG    

年代:1986

数据来源: Karger