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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 174 (1994), S. 173-185 
    ISSN: 1432-1351
    Keywords: Electrical stimulation of the brain ; Fish ; Forebrain ; Preoptic area ; Sound production ; Sexual behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In mammals, birds and amphibians the neural pathways controlling sound production descend from higher centers in the forebrain, whereas in fishes only brainstem and spinal centers have been explicitly implicated in sound production. We now report that electrical stimulation of the forebrain of the oyster toadfish (Opsanus tau) readily evokes both the agonistic grunt and the courtship boatwhistle. Boatwhistles are more realistic than ones previously evoked from lower centers. Positive stimulation sites are localized in the preoptic area (nucleus preopticus parvocellularis anterior) and the supracommissural nucleus of the ventral telencephalon, a likely homologue of the amygdala. Both sites contain gonadal steroid-concentrating neurons and play a central role in fish courtship behavior. Evoked sounds form a continuum from knock grunts, burst grunts, transition boatwhistles to complete boatwhistles; sound pressure level (SPL), fundamental frequency and duration increase consistently within the continuum. For all sound types, SPLs exhibit the smallest variation (coefficients of variation of 2.7 to 5.7%), fundamental frequency is intermediate (5 to 13%) and durations vary most widely (18 to 60%). Boatwhistles, with the smallest variation and greatest amplitude, are likely generated by a maximal output of the CNS and sonic muscles. Grunt SPLs however, vary over a range of 26 dB for all fish and by as much as 18 dB in an individual, suggesting recruitment of variable numbers of motor units despite electrical coupling within the sonic motor nucleus.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 186 (2000), S. 435-445 
    ISSN: 1432-1351
    Keywords: Key words Fish ; Hearing ; Evoked potentials ; Ear ; Gasbladder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The teleost gasbladder is believed to aid in fish audition by transferring pressure components of incoming sound to the inner ears. This idea is primarily based on both anatomical observations of the mechanical connection between the gasbladder and the ear, followed by physiological experiments by various researchers. The gasbladder movement has been modeled mathematically as a pulsating bubble. This study is extending the previous work on fish with a physical coupling of the gasbladder and ear by investigating hearing in two species (the blue gourami Trichogaster trichopterus, and the oyster toadfish Opsanus tau) without a mechanical linkage. An otophysan specialist (the goldfish Carassius auratus) with mechanical coupling, is used as the control. Audiograms were obtained with acoustically evoked potentials (e.g., auditory brainstem response) from intact fish and from the same individuals with their gasbladders deflated. In blue gourami and oyster toadfish, removal of gas did not significantly change thresholds, and evoked potentials had similar waveforms. In goldfish thresholds increased by 33–55 dB (frequency dependent) after deflation, and major changes in evoked potentials were observed. These results suggest that the gasbladder may not serve an auditory enhancement function in teleost fishes that lack mechanical coupling between the gasbladder and the inner ear.
    Type of Medium: Electronic Resource
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