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For over 50 years, Richard R. (Dick) Fay made major contributions to our understanding of vertebrate hearing. Much of Dick's work focused on hearing in fishes and, particularly, goldfish, as well as a few other species, in a substantial body of work on sound localization mechanisms. However, Dick's focus was always on using his studies to try and understand bigger issues of vertebrate hearing and its evolution. This article is slightly adapted from an article that Dick wrote in 2010 on the closure of the Parmly Hearing Institute at Loyola University Chicago. Except for small modifications and minor updates, the words and ideas herein are those of Dick.

Combined, we have known Peter Narins for well over 120 years. We take great pleasure in honoring an “old” and greatly valued colleague and friend. We start by pointing out that none of us have done research with Peter, but that each off us knows, admires, and greatly values his work. For over 40 years, Peter's interdisciplinary blend of acoustics, psychophysics, physiology, and anatomy, often conducted in exotic places, has held us all in awe. Moreover, one of the most important part of Peter's work is that its impact extends far beyond amphibians. His work has helped us think about the bioacoustics of birds and fishes, and about the evolution of vertebrate hearing. His work has also stimulated research questions and how we understand research results for non-amphibian species. And, most importantly, it is not only the three of us who have benefitted from Peter's work – his contributions permeate all of animal bioacoustics and will do so for decades. Our talk will focus on how Peter's work has, and continues, to contribute to our own research, and that of many others. [Funded by three old guys.]

The SilverMedal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.

The masking effects of white and amplitude comodulated noise were studied with respect to simple signal detection and sound source determination in goldfish. A stimulus generalization method was used to determine the signal-to-noise ratio required to completely determine the signal’s characteristics. It was found that the S/N required for this determination is about 4 dB greater than that required for signal detection, or was about 4 dB greater than the critical masking ratio. This means that the potential harm to fish of a given masking noise is at least 4 dB greater than previously thought, based on critical masking ratios. However, for amplitude comodulated noise between 10 and 50 Hz modulation rate, the potential harmful effects are up to 5.3 dB less than would be predicted from the critical masking ratio for unmodulated noise.

The perception of two simultaneous tones was investigated in goldfish using classical respiratory conditioning and a stimulus generalization paradigm. Pairs of tones were used to make up a mixture of 150 Hz and a higher harmonic or a mistuned harmonic. Fish were conditioned to the two-tone mixture and then tested for generalization to several pure tones. The simultaneous tones tended to be segregated in perception, with the generalization gradient for single tones having two peaks corresponding to the frequencies of the tone pairs. There were no consistent differences in the generalization gradients following conditioning to harmonic or inharmonic tone pairs. In addition, experiments were carried out in which the two tones of the pair were heard on alternate trials, always as single tones, followed by generalization tests to single tones. There was more generalization in this experiment, reflecting the fact that conditioning and generalization test stimuli were both single tones. However, the shapes of the generalization gradients were similar to those in which fish were conditioned to two simultaneous tones, indicating that the simultaneity of the tones did not make them harder to segregate. As the frequency separation between the two components narrowed, segregation tended to fail.

A conditioned feeding response of the mottled sculpin was used to measure level discrimination by the lateral line system as a function of source level, frequency, and distance. Level discrimination limens (LDLs) were determined with a 6‐mm‐diam, sinusoidally vibrating sphere placed in front of the trunk lateral line system at varying distances from the trunk of the fish. LDLs were relatively independent of frequency over most of the detection bandwidth, with mean values ranging from 5–6 dB from 10 to 50 Hz at a fish‐to‐source distance of 15 mm. The mean LDL at 100 Hz, near the upper end of the frequency range of the lateral line system was 8–9 dB at the same source distance. Mean LDLs at 10 and 20 dB above detection threshold were not significantly different, nor were mean LDLs at distances ranging from 7.5 to 30 mm for a 50‐Hz, 10‐dB SL source. The level‐encoding features of posterior lateral line fibers innervating the trunk were also determined from data previously collected under stimulus conditions nearly identical to those used for behavioral studies. Afferent fibers responded to level increments with increases in both spike rate and phase‐locking over most of the conditions used in behavioral experiments. Although it was impossible to eliminate spike rate as a level‐encoding mechanism at any stimulus condition, phase‐locking appeared to be a strong candidate at low source levels and vibration frequencies. These results show that level discrimination abilities by the sculpin lateral line system are within the range of capabilities of vertebrate auditory systems and that phase‐locking in peripheral fibers may be important for encoding stimulus level by the lateral line.

The aim of this study was to use plainfin midshipman fish (Porichthys notatus) as a general model to explore how fishes localize an underwater sound source in the relatively simple geometry of a monopole sound field. The robust phonotaxic responses displayed by gravid females toward a monopole sound projector (J-9) broadcasting a low-frequency (90 Hz) tone similar to the fundamental frequency of the male's advertisement call were examined. The projector's sound field was mapped at 5 cm resolution azimuth using an eight-hydrophone array. Acoustic pressure was measured with the array and acoustic particle motion was calculated from pressure gradients between hydrophones. The response pathways of the fish were analyzed from video recordings and compared to the sound field. Gravid females at initial release were directed toward the sound source, and the majority (73%) swam to the playback projector with straight to slightly curved tracks in the direction of the source and in line with local particle motion vectors. In contrast, the initial direction of the control (sound-off) group did not differ from random. This paper reports on a comparison of fish localization behavior with directional cues available in the form of local particle motion vectors.

Classical conditioning of respiration was used to obtain psychometric functions for pulsed tone level discrimination in the goldfish (Carassius auratus). Conditioned respiratory suppression is a graded response that has some properties of a confidence rating measure. These properties were used to obtain receiver operating characteristics (ROC) and psychometric functions using a blocked method of constant stimuli. Empirical ROCs and neurometric functions were also obtained for single auditory-nerve fibers using spike count as the decision variable in order to evaluate a simple rate code for level discrimination. Psychometric and neurometric functions for level discrimination are similar in showing the same general form (summarized by Weibull functions) that is independent of signal duration. The lower slope of neurometric functions compared with behavioral functions for level discrimination is in accord with similar data on sound detection and vision in nonhuman mammals. Both neural and psychophysical level discrimination thresholds decline with increasing duration (20 to 320 ms), with similar slopes except at short signal durations (20 to 50 ms). At these durations, the animal's use of a channel-selection strategy and neural information following stimulus offset could reduce the difference between neural and psychophysical thresholds. The slopes of the neural and psychophysical duration functions are similar to those for human observers, but the majority of auditory-nerve fibers sampled have lower level discrimination thresholds than the behaving animal. Since human observers perform better than the majority of neurons in level discrimination, well-trained human listeners may be able to select channels with superior information, or to combine information across channels in ways that the goldfish and other animals do not. In general, one is encouraged to believe that neural mechanisms need not be more complex or sensitive than those considered here to account for pure-tone level discrimination in fishes, humans, and other vertebrates.

A series of experiments was undertaken to investigate methods of sound source localization by fish. In these experiments, positive phonotaxic responses of gravid female plainfin midshipman fish (Porichthys notatus) to low-frequency, playback tones (80–90 Hz) were studied as they approached sound sources. The sound fields for simple (monopole) and relatively complex (dipole) sources within the behavioral arena were measured and characterized in terms of pressure and particle motion. Results indicate that female midshipman fish are able to locate sound sources in the near field using acoustic cues alone, and that they used the particle motion vectors to locate the source in both the monopole and dipole sound fields. The tank acoustics were modeled and compared to the measured pressure and particle motion sound fields. [This work was supported by the National Science Foundation.]

Glenis and I were psychology graduate students together in 1970-1971. She was interested in auditory psychophysics, but soon developed an interest in comparative psychophysics which she pursued in a post-doc and a faculty position in Germany, where she obtained a behavioral audiogram for the horseshoe bat and later studied masking in the same species. This audiogram was one of the very first psychophysical investigations of hearing in any bat and the very first for the horseshoe bat. It confirmed a rather complex frequency response function with sensitivity peaks at about 20 kHz and 60 kHz, and a very sharp peak at about 80 kHz. The masked thresholds indicated rather normal critical masking ratios (CR) except in a narrow region at about 80 kHz where the CRs are up to 15 dB lower than expected, suggesting a critical band of about 300 Hz at 80 kHz that is presumably used in Doppler-shift compensation. In 1981-1983, Glenis went on to investigate frequency and rate modulation discrimination in the chinchilla, for the first time, and to study tone-on-tone masking in the chinchilla. Since these early works, Glenis has maintained her comparative interests with studies on birds, kangaroo rats, frogs, and fleas on cats.

Although a number of previous behavioral studies have demonstrated that elasmobranch fishes can detect and are attracted to low frequency sounds, few physiological studies have characterized the auditory response properties of the elasmobranch inner ear to such low frequency sounds. In this study, we examined the directional and frequency responses of the inner ear saccule in the little skate, Raja erinacea to low frequency stimuli. Evoked microphonic potentials were recorded from the middle region of the saccule while sound was generated using a shaker table designed to mimic the particle motion vector component of sound. 8 test frequencies (50, 64, 84, 100, 140, 185, 243, and 303 Hz) and 11 directions were used to characterize the displacement sensitivity, frequency response and directional response properties of the skate saccule. Saccular potentials were evoked and measured at twice the stimulus frequency in vivo using a wave analyzer while stimuli were generated via the shaker table system. The right...

A series of experiments was undertaken to investigate methods of sound source localization by fish. In these experiments, positive phonotaxic responses of gravid female plainfin midshipman fish (Porichthys notatus) to low‐frequency, playback tones (80–90 Hz) were studied as they approached sound sources. The sound fields for simple (monopole) and relatively complex (dipole) sources within the behavioral arena were measured and characterized in terms of pressure and particle motion. Results indicate that female midshipman fish are able to locate sound sources in the near field using acoustic cues alone, and that they used the particle motion vectors to locate the source in both the monopole and dipole sound fields. It was also found that neither the lateral line nor the swim bladder was necessary for localization behavior, and that the fish were able to solve the 180 deg ambiguity inherent in the particle motion vectors. [Work was supported by the National Science Foundation.]

Twelve recently determined evoked potential (EP) audiograms were compared to six behavioral (BEH) audiograms for the goldfish. There are no theories possible on the relationships between these two very different measurements of auditory response; nevertheless many workers desire to know how they compare so that the EP audiograms can possibly “stand in” for the BEH measures. The data from the many audiograms indicate that they are only very roughly similar in terms of sensitivity (variation ranging from 45 to 60 dB) and best frequency (variation ranging from 300 to 1500 Hz). This variation among audiograms, within and between measurement methods used, is discomforting. There are no trends indicating that this variation is due to a single factor such as near field acoustics (all audiograms were determined in the near field of the sound source), threshold definition, ambient noise levels, conditioning method, or type of sound source. The averaged audiograms differ in best frequency (EP=525 Hz; BEH=725 Hz) an...

Localization of a dipole sound source was studied in female plainfin midshipman fish (Porichthys notatus). Experiments were conducted and videotaped in a 3.65‐m‐diameter tank using a dipole underwater speaker system placed near the center of the tank. The sound was a 90‐Hz tone, approximately the fundamental frequency of the male’s advertisement call. Pressure and particle motion components of the sound field were mapped with 9‐cm resolution. Pressure was measured using an eight‐hydrophone array, and particle motion vectors calculated from the pressure gradients. Mapping confirmed that the projector was operating as a dipole. Gravid fish were released 70 cm from the sound source at two different positions relative to the dipole axis: one near the dipole axis and one near the pressure null axis. Twenty‐five positive responses were recorded from each release site. The phonotactic response pathways along the dipole axis consisted of slightly curved tracks to the sound source, whereas pathways from the null axis consisted of greatly curved tracks to the source that followed the particle motion vectors. Results confirm that fish can locate a dipole sound source and are sensitive to the direction of acoustic particle motion. [Work supported by NSF.]

In 1993 (Brain, Behav. Evol. 41, 14–38 (1993)] we evaluated changes in our knowledge of fish bioacoustics since our 1973 review and proposed ten issues that still needed to be answered. This presentation asks whether we have have made progress on these issues since 1993 and poses questions for future fish bioacoustics research. Many of the topics suggested in 1993, such as sound localization mechanism, the roles of the swim bladder’ and other peripheral structures in hearing, and the contributions of pressure and particle motion in hearing are still open. There are also “newer” questions not apparent in 1993, such as mechanisms of ultrasound detection and the effects of increased human‐generated noise on fish. The usefulness of thinking of fish as “hearing specialists” and “hearing generalists” still needs to be assessed. Finally, an overriding question related to the significance of the diversity of fishes and diversity in ear structure, has not been resolved. Indeed, we still do not know whether the div...

Previous behavioral studies have shown that elasmobranch fishes can be attracted to low‐frequency sound sources (< 80 Hz) in their natural habitat, but relatively few studies have characterized the auditory response properties of the elasmobranch inner ear to low‐frequency sounds. Here, we examine the response properties of evoked saccular potentials from the skate inner ear to determine the auditory threshold sensitivity and frequency response of saccular hair cells to low‐frequency stimuli. Saccular potentials were recorded from the medial region of the saccule while sound was generated using a shaker table designed to mimic the particle motion component of sound. Four test frequencies (50, 64, 84, and 100 Hz) and 11 directions were used to characterize the displacement sensitivity, frequency response, and directional response properties of the skate saccule. Saccular potentials were evoked and measured at twice the stimulus frequency in vivo using a wave analyzer, while stimuli were generated via the s...

Coding mechanisms for spectral analysis and sound source location were investigated in Acipenser fulvescens, the lake sturgeon. A. fulvescens belongs to one of the few extant nonteleost ray‐finned fishes, with a phylogenetic history that dates back about 200 million years. A shaker system was used to simulate the particle motion component of sound during electrophysiological recordings of isolated single units from the eighth nerve. Data were compared to teleosts and land vertebrates. Peripheral coding strategies for spectral analysis and sound source location in A. fulvescens resembled those found in teleosts. Frequency characteristics generally resembled that of low‐frequency afferents of other fishes and land vertebrates and the auditory periphery in A. fulvescens appears to be well suited to encode the intensity of sound. Eighth nerve afferents responded to directional stimuli in a cosinelike manner (as in teleosts). However, differences from teleosts were found that may have implications for the mech...

In 1973, we wrote a review in J. Acoust. Soc. Am. that summarized our view of fish hearing and bioacoustics. This presentation looks back on the the major questions we had at the time and how the field has dealt with them, or not, to the present. Some of the issues identified included: (1) the roles of the various otolith organs for hearing; (2) lateral line function and its relation to hearing; (3) sound source localization; and (4) how sound stimulation works for fishes without obvious specializations for pressure reception. There have been major advances in these and other aspects of fish sound reception, but in every case, there are significant unanswered questions. For example, it is still controversial whether the utricle plays a role in hearing in most species, and the functional role of the lagena remains an enigma. However, we now have a much better understanding of lateral line stimulation and function, and we now understand that it is not an “accessory auditory organ,” as was widely assumed initially. Many questions of sound localization are now thought to be answered theoretically, and in some cases empirically, but many critical and fundamental experiments on localization remain to be done.

Although binaural processing is known to be critical for sound source localization in terrestrial vertebrates, binaural processing for sound source localization in fishes has not been demonstrated. Previous physiological and neuroanatomical studies have indicated that interaural convergence is present in auditory pathway of oyster toadfish (Opsanus tau). In this study, we introduce a reversible method, otolith tipping, to evaluate the presence of binaural inputs. The normal directional response pattern (DRP) was recorded extracellularly for auditory cells in the first‐order descending octaval nucleus (DON) or the midbrain torus semicircularis (TS) using directional stimuli in the horizontal and midsagittal planes. The DRP was re‐evaluated while gently tipping the ipsilateral or contralateral otolith of the saccule to alter the normal relationship with the auditory epithelium. The DRP was also evaluated post‐tipping to ensure no damage had occurred. In the DON, ipsilateral or contralateral tipping most oft...

Auditory scene analysis (ASA) is a capacity of auditory perception that results in the hearing out or segregating of sound sources as individual objects or events when heard in the presence of other, simultaneous sources. Fish, humans, starlings, and nonhuman primates have been shown to have this capacity. I argue that any animal that hears probably has this capacity, and that it is not restricted to large‐brained animals, nor to the perception of species‐specific communication sounds. The demonstrations of ASA in goldfish include the capacity to hear out the frequency of pure tones when heard as a mixture of tones, and the hearing out of two, simultaneous pulse trains based on temporal and spectral differences, analagous to hearing out different musical instruments playing the same note. So far, harmonicity has been ruled out as a factor in ASA in goldfish, and spectral resolution has been shown to be necessary. ASA is a powerful phenomenon of human and animal hearing, and probably determines what we mea...

Responses of cells in the toadfish medulla (descending octaval nucleus: DON) and midbrain (torus semicircularis: TS) were studied to investigate binaural interaction and processing. Normally, the two ears of fish cannot be stimulated independently. A method was developed to temporarily inactivate one ear by slightly displacing the saccular otolith on one side (tipping) to change its orientation in space and, therefore, alter the responsiveness of the hair cells. Brain cells were evaluated for directional characteristics and frequency response (1) before otolith tipping, (2) with the otolith tipped, and (3) post‐tipping. For DON cells (n=14), contralateral saccular otolith tipping most often resulted in subtle effects consisting of an overall change in responsiveness (±spikes/sec); significant changes in the preferred direction were rare. In the TS (n=20), most cells exhibited changes in responsiveness and in directionality. These experiments demonstrate the existence of excitatory and inhibitory binaural ...

Art Myrberg was trained to study behavior from an ethological perspective. When it came to studying the hearing of the vocal and communicating damselfish species of the genus Eupomacentrus, he surprisingly decided to use conditioning methods in combination with the best technology then known to produce an excellently designed animal psychoacoustic (laboratory) study that remains today, 26 years later, an exemplary model for students in this field [A. A. Myrberg and J. Y. Spires, J. Comp. Physiol. 140, 135–144 (1980)]. First, Myrberg well understood that sensitivity to acoustic particle motion was possible for these species, so he produced or simulated sound in the far, free field using a long tube with sound absorbers at the opposite end, and measured both sound pressure and acoustic particle motion. He documented that Eupomacentrus was sensitive to particle motion at 100 Hz, but was sound‐pressure‐sensitive at higher frequencies. He also understood that ambient noise was an important issue in hearing studies, and he did all that he could to measure and reduce it. The result was a ‘‘V’’‐shaped audiogram with greatest sensitivity at 500 Hz, and almost no interspecific variation. We can have great confidence in these audiograms today as valid measurements of hearing ability.

Interest in fish sound production and hearing dates back to the writings of Aristotle (384–322 BCE) and Pliny the Elder (23–79 CE), both of whom noted not only that fish make sounds, but also speculated that fish must be able to hear despite their not having apparent ears. The fact that fish could hear was first demonstrated with the work of G. H. Parker in 1903 and later by Karl von Frisch. Studies on sound production were sporadic in the early part of the 20th century and often based on anecdotes until technology derived from antisubmarine warfare became available after World War II. This equipment enabled investigators to listen to fish and correlate sounds with behavior. It was not until the early 1960s that intensive investigations started on fish hearing. This paper will review the history of the study of fish bioacoustics and discuss the contributions of a large number of investigators including those of Arthur Myrberg. Indeed, Art’s research stands as a landmark in the field, as well as a fine example of true scholarship. Furthermore, his charismatic presentations of his work were instrumental in stimulating the investigations of other scientists.Interest in fish sound production and hearing dates back to the writings of Aristotle (384–322 BCE) and Pliny the Elder (23–79 CE), both of whom noted not only that fish make sounds, but also speculated that fish must be able to hear despite their not having apparent ears. The fact that fish could hear was first demonstrated with the work of G. H. Parker in 1903 and later by Karl von Frisch. Studies on sound production were sporadic in the early part of the 20th century and often based on anecdotes until technology derived from antisubmarine warfare became available after World War II. This equipment enabled investigators to listen to fish and correlate sounds with behavior. It was not until the early 1960s that intensive investigations started on fish hearing. This paper will review the history of the study of fish bioacoustics and discuss the contributions of a large number of investigators including those of Arthur Myrberg. Indeed, Art’s research stands as a landmark in the field, as well as a fine exa...

It has been hypothesized that hearing arose early in vertebrate evolution to use sound to glean information about the environment, including the presence of predators and prey. The importance of sound to sense the acoustic scene is especially true underwater where the visual horizon is limited. To create an acoustic scene from sound, an animal needs to localize and identify sound sources. We hypothesize that the sound localization capabilities of primitive bony fishes such as sturgeon are as capable as those of modern bony fishes such as goldfish and, perhaps, many terrestrial vertebrates. We present results from experiments investigating the neural mechanisms of directional hearing and frequency analysis in the auditory periphery of the sturgeon. Extracellular single units were recorded from the eighth nerve during stimulation with a three‐axis shaker system that subjects the fish ear to linear accelerations in known directions at various frequencies. This system enables the characterization of both spatial and frequency tuning of the afferents innervating the ear. The results show that similar neural mechanisms for encoding sound direction and frequency exist in the periphery of modern and primitive bony fish, thereby supporting the hypothesis that basic auditory functions arose very early in vertebrate history.

In order to develop acoustic exposure criteria for fish and marine turtles based on scientific evidence, an ASA Standards Working Group was formed with a membership that includes basic scientists expert on fish and turtle bioacoustics, physical acousticians with special expertise in marine bioacoustics, and several individuals with expertise on effects of anthropogenic sound in the marine environment. This presentation is a summary of the group’s progress to date. One of the Working Group’s goals is to publish several papers, one on what is known about damage risks due to exposure to underwater noise (e.g., from pile driving, seismic exploration, sonar systems), and one assessing the efficacy of various measures to mitigate adverse effects of noise exposure. The working group has tentatively decided that the fish potentially affected should be categorized with respect to their hearing sensitivity (potential for auditory system damage) and whether the species is known to detect sound pressure or acoustic particle motion. Over the next year to 18 months, the Working Group will be evaluating the known effects of sound sources on fish and turtles, identifying areas in which further research is needed, and beginning to develop noise exposure criteria for both turtles and fish.

Interest in anthropogenic sound in the marine environment has been directed at concerns about the effects of sound on marine mammals. However, fish make up a far larger and more diverse portion of the oceans than do marine mammals, and they hold considerable economic importance internationally. This has led to a growing interest in the effect of anthropogenic sounds on fish in environments ranging from shallow waters near in‐shore shipping lanes to the deep sea. Concerns for effects on fish are parallel to those for marine mammals, and include issues ranging from the death of individual animals to the potential for behavioral changes that could lead to impacts on the survival of populations or species. While the body of data on the effects of anthropogenic sounds on fish is still small, and much of the work is not in the peer‐reviewed literature, the number of peer‐reviewed studies is growing. The purpose of this special session is to provide an overview of what we currently know about the effects of anthropogenic sound on fish, help define the major outstanding questions on these effects, and to provide the basis for discussion of current and future research in order to help resolve these questions.

The saccule mediates the sense of hearing for many fish species, goldfish (Carassius auratus) in particular. Motions of the swim bladder in response to pressure fluctuations impinge on the saccule of each ear, where auditory‐nerve fibers project to medullar, midbrain, and forebrain nuclei in a circuit analogous to the ascending auditory system of tetrapods. It has been repeatedly shown over the past 40 years that the sense of hearing mediated by the saccule has many fundamental features in common with the sense of hearing of tetrapods. Detection and discrimination thresholds for goldfish are in the vertebrate range quantitatively, and are of the same sorts of simple and complex discriminations that mammals and other tetrapods can perform. Furthermore, goldfish behave as if the perceptual dimensions of spectral pitch, complex musical pitch, timbre, and roughness exist for them. Although goldfish do not vocalize, many fish species that hear using saccular input do vocalize (e.g., mormyrids), and have special adaptations for responding to vocalizations, like many tetrapods. Finally, goldfish have been shown capable of simultaneous stream segregation based on the same principles known for humans and other species. Thus, otolith organs can participate in a sense of hearing that is typical for vertebrates.

Among many mammals and birds, frequency‐place cochlear maps have a similar form and differ primarily with respect to the length of the cochlea or basilar papilla, and with respect to the frequency range of hearing. This is remarkable, especially given the differences in anatomical organization and evolutionary history between mammals and birds. This is a striking example of convergent or parallel evolution. With few exceptions, the cochleae of mammals and birds are indeed scale models of one another. One of the primary functions of the frequency‐place map is in frequency analysis. Whether this function is defined by frequency discrimination thresholds, critical masking ratios, critical bands or auditory filters in general, frequency analytic performance, behaviorally‐defined, can be laid out on the basilar membrane and a critical basilar membrane distance can be associated with a given performance criterion. In general, these critical distances differ according to the function (e.g., frequency delta Fs versus critical bandwidths), but are remarkably similar functions of frequency within and between species (they tend to be constant). It seems likely that evolution has selected the consequences of frequency analytic mechanisms for perception rather than the mechanisms themselves. [Work supported by NIH.]

The perception of harmonic complexes was studied in goldfish using classical respiratory conditioning and a stimulus generalization paradigm. Groups of animals were initially conditioned to several harmonic complexes with a fundamental frequency (f0) of 100 Hz. ln some cases the f0 component was present, and in other cases, the f0 component was absent. After conditioning, animals were tested for generalization to novel harmonic complexes having different f0’s, some with f0 present and some with f0 absent. Generalization gradients always peaked at 100 Hz, indicating that the pitch value of the conditioning complexes was consistent with the f0, whether or not f0 was present in the conditioning or test complexes. Thus, goldfish do not miss the fundmental with respect to a pitch‐like perceptual dimension. However, generalization gradients tended to have different skirt slopes for the f0‐present and f0‐absent conditioning and test stimuli. This suggests that goldfish distinguish between f0 present/absent stimu...

The Springer Handbook of Auditory Research presents a series of comprehensive and synthetic reviews of the fundamental topics in modern auditory research. It is aimed at all individuals with interests in hearing research including advanced graduate students, post-doctoral researchers, and clinical investigators. The volumes will introduce new investigators to important aspects of hearing science and help established investigators to better understand the fundamental theories and data in fields of hearing that they may not normally follow closely. Each volume is intended to present a particular topic comprehensively, and each chapter will serve as a synthetic overview and guide to the literature. As such, the chapters present neither exhaustive data reviews nor original research that has not appeared in peer-reviewed journals. The series focuses on topics that have developed a solid data and conceptual foundation rather than on those for which a literature is only beginning to develop. New research areas will be covered on a timely basis in the series as they begin to mature. Each volume in the series consists of five to eight substantial chapters on a particular topic. In some cases the topics will be ones of traditional interest for which there is a solid body of data and theory, such as auditory neuroanatomy (Vol. 1) and neurophysiology (Vol. 2).

Coding of frequency and particle motion directionality is described for two fishes; goldfish (a sound‐pressure specialist), and oyster toadfish (a hearing generalist). The goldfish hears in a wide bandwidth (>2 kHz) and the toadfish in a narrower one (

Psychophysical experiments have helped define the sense of hearing of goldfish with respect to detection and discrimination thresholds within many acoustic dimensions. Generally, these data reveal aspects of peripheral and early brain processing that are qualitatively, and sometimes quantitatively, indistinguishable from those of most other vertebrates. This correspondence suggests that goldfish share an essentially common sense of hearing with other vertebrates, and motivated new experiments that investigate more complex aspects of sound perception in goldfish using the phenomenon of stimulus generalization to study perceived similarities among simple and complex sounds. We have found that goldfish listen analytically to simultaneous tones, have perceptual dimensions analogous to pitch, timbre, and roughness in human listeners, and can segregate simultaneous, complex sources in perception. Several of these processes will be illustrated. These results are in accord with the hypothesis that the sense of he...

Neurophysiological experiments on toadfish indicate the different strategies by which toadfish localize sources in azimuth and elevation. The saccules of the toadfish respond with great sensitivity to acoustic particle motion in the manner of inertial accelerometers. The directional response properties of otolithic afferents were studied in the horizontal and mid‐sagittal planes using a 3‐D shaker system. Most primary afferents have a cosine directionality response pattern. In the horizontal plane, an afferent’s best azimuthal direction is determined primarily by the orientation of the otolith organ in the head, and azimuth could be encoded as interaural response differences deriving from each organ’s gross directionality. The elevation of the axis of particle motion could be represented by a within‐organ pattern of response magnitude over the afferent array that is determined by the patterns of hair cell orientation. In humans, source elevation can be estimated from the head‐related transfer function, a monaural computation based on tonotopy. In toadfish, the saccule is not organized tonotopically, but directly with respect to the elevation of most effective particle motion. Thus, sound localization in fishes could be based on mechanisms of monaural and binaural computation substantially similar to those operating in other vertebrates. [Work supported by NIH and NIDCD.]

Male toadfish vocalize (e.g., the ‘‘boatwhistle’’ ‐f0 from 100 to 250 Hz) to attract females during mating season. This experiment investigates whether the frequency response of primary saccular afferents is adequate to encode these vocalizations. Whole‐body oscillation (0.1–300 nm displacements) was delivered by a three‐dimensional shaker system driven by noise with a flat spectrum between 50 and 1000 Hz. Stimuli were presented along three orthogonal axes (side–side, front–back, and up–down). Spikes were time stamped with 0.1‐ms resolution. REVCOR functions were averaged accelerometer recordings of the noise triggered by spikes for 51.2 ms before and after each spike. This estimated the impulse response of the linear filtering that preceded spike generation. An FFT of the impulse responses estimated an afferent’s filter shape. Impulse responses obtained were damped oscillations having a major peak indicating the magnitude and direction of excitatory acceleration. In general, filter shapes are low‐pass wi...

This experiment characterized the directional responses of cells of the auditory midbrain of goldfish. Single units in the midbrain were characterized by their response to whole‐body vibratory stimuli of various directions and amplitudes. The animal’s head was fixed in a rigid dish that was accelerated using two orthogonal pairs of shakers in the horizontal plane, and one shaker oriented vertically. Three orthogonally oriented accelerometers resolved the dish’s motion in azimuth and elevation. Computer‐synthesized sinusoids activated the shaker channels with relative phases and amplitudes required to produce linear motion along 12 axes equally spaced over 180° in each of the horizontal, midsagittal, and frontal planes. Spike rate was plotted as a function of stimulation axis angle in both Cartesian and polar coordinates. Most cells showed strongly directional response patterns with a primarily vertical orientation. Response patterns were classified with respect to the symmetry, sharpness, and the amplitude dependence of these directional features. Models were developed to give possible explanations for the observed responses. Many of the response shapes can be explained by combinations of simple peripheral effects (threshold and saturation) and inhibitory interaction. [Work supported by a Program Project Grant (NIH, NIDCD) to the Parmly Hearing Institute.]

How goldfish perceive temporal patterns of acoustic clicks was investigated using a stimulus generalization paradigm with classical respiratory conditioning. Fish were conditioned to suppress respiration to trains of high‐pass‐filtered clicks with periodic inter click intervals (ICI). Five groups of animals were conditioned using ICIs between 4 and 25 ms, and then tested for response to eight novel ICIs between 4 and 25 ms. Response magnitude to novel ICIs (generalization) is a monotonic decreasing function of the difference between the conditioning and test ICIs. In further experiments, test stimuli consisted of temporally jittered periodic ICIs, and various pseudorandom ICI distributions. A model predicting the magnitude of generalization to these patterns was developed assuming that generalization is proportional to the number of ICIs common to conditioning and testing stimuli, and that the internal representation of ICIs has a variance predicted from discrimination data. Evidence was obtained that ICIs are analyzed, but that ICI representation is not necessarily congruent with that for pure tones of the same period. [Work supported by a Center Grant from the NIH NIDCD.]

The temporal evolution of masking and frequency selectivity was studied in the goldfish using classical respiratory conditioning and a tracking psychophysical procedure. The temporal position of a brief tonal signal within a longer duration, tonal masker has little or no effect on signal detectability when the frequency of the masker is less than or equal to that of the signal. For masker frequencies above that of the signal, signal detectability improves as the signal onset is delayed relative to that of the masker. These patterns of tone-on-tone masking are quite similar to those observed for humans. These temporal masking patterns are qualitatively similar in shape to the peristimulus-time histogram profiles of the low-frequency saccular fibers thought to be used in this task. Frequency- and time-dependent changes in signal detectability result in specific changes in the sharpness of psychophysical tuning curves (PTC). In general, PTCs determined for signals occurring at masker onset are the most broadly tuned, and PTCs determined in forward masking are the most sharply tuned. The PTCs for signals temporally centered in the masker are intermediate. These results suggest that temporal tone-on-tone masking patterns and the temporal evolution of psychophysical tuning curves result from the response properties of peripheral auditory-nerve fibers.

Averaged evoked potentials (AEPs) recorded in and near the torus semicircularis of the goldfish midbrain using multiple electrodes were used to measure relative sensitivity to low (head vibrations) and high (loudspeaker stimulation) impedance acoustic signals before and after swimbladder deflation. The peak‐peak voltage of AEPs elicited by 100 ms tone bursts (5 ms rise‐fall times) were measured as a function of stimulus amplitude and frequency between 0.07 and 1 kHz. Swimbladder deflation caused a loss in sound pressure sensitivity (20–50 dB) which occurred across all frequencies tested approximately equally, and a small increase in vibration sensitivity particularly at low frequencies. Variation in sensitivity, frequency response, the slopes of input‐output functions, the ratios between pressure and vibratory sensitivity, and changes in sensitivity following swimbladder deflation varied with electrode location. The goldfish midbrain is clearly not homogeneous with respect to auditory response. Several li...

The acoustic frequency selectivity of over 500 saccular nerve fibers of the goldfish was studied using automated threshold tracking based on spike rate increments defined statistically. Saccular fibers of the goldfish show great variation in (1) best sensitivity (-26 to + 35 dB re: 1 dyn/cm2), (2) best frequency (below 100 to 1770 Hz), (3) spontaneous rate (0 to over 200 spikes/s), (4) spontaneous type (silent, regular, irregular, burst), and (5) degree of tuning (Q 10 dB from less than 0.1 to 2). Saccular fibers may be grouped into four nonoverlapping categories based on tuning and best frequency: (1) untuned (less than 10-dB variation in sensitivity between 100 and 1000 Hz), (2) low frequency (BF from below 120 to 290 Hz), (3) midfrequency (BF between 330 and 670 Hz), and (4) high frequency (BF between 790 and 1770 Hz). Within each category, all spontaneous rates and types, and all degrees of tuning can be observed. The least sensitive fibers within each group have zero spontaneous rates. The goldfish is like all other vertebrates studied in that the peripheral auditory system is adapted for frequency selectivity throughout the animal's entire frequency range of hearing. Peripheral tuning most likely accounts for behavioral determinations of the "auditory filter" and for the detectability of signals masked by noise. The signal-to-noise ratio enhancement provided by these peripheral filters is likely to be of primary biological significance. A "place principle" of sound quality analysis based on lines "labeled" according to best frequency in the brain cannot be ruled out on the basis of the peripheral physiology.

The behavioral responses of goldfish to a variety of amplitude‐modulated (AM) acoustic signals were studied using a stimulus generalization paradigm in combination with a classical conditioning method. Measurements were thus allowed of the equivalence among various complex and simple signals in controlling the conditioned respiration response. The goldfish's conditioned response to AM signals were found to be controlled by carrier frequency, modulation depth, and to a lesser extent, by modulation frequency in the 40‐Hz range. On the other hand, pure‐tone frequency exerted minimal behavioral control for subjects conditioned to AM signals. Subjects conditioned to a 40‐Hz pure tone tended to generalize maximally to an AM signal having a 40‐Hz modulation rate. The results indicate the degree to which the goldfish can use much of the information present in complex periodic acoustic signals and suggest the existence of periodicity pitch in fish.

The ability of goldfish to detect a change in the frequency of 400-Hz pure-tone bursts was studied using classical respiratory conditioning. The frequency discrimination threshold was measured at 15-, 35-, and 55-dB sensation level (SL), under conditions of (1) constant intensity, (2) roving intensity (plus and minus 6-dB burst-to-burst variation in intensity), (3) upward frequency change, and (4) downward frequency change. There was no overall effect of SL on frequency discrimination, but roving the intensity elevated thresholds by about 6 Hz (33%) and increased variability. Upward shifts in frequency elevated thresholds slightly (by 2 Hz or 10%) relative to downward shifts. These relatively small and statistically insignificant effects suggest that earlier measures of frequency discrimination in the goldfish are not due to the detection of simple changes in spike rate within individual peripheral channels.

The capacities of the goldfish to detect changes in sound burst repetition rate were studied using classical respiratory conditioning. In experiment I, the just detectable amount of an instantaneous random jitter of burst period was measured as a function of mean period. In experiment II, the just detectable amount of slow sinusoidal jitter of burst period was measured for three burst types having different spectral and waveform characteristics. In experiment III, sinusoidal jitter detection thresholds were measured in the presence of varying degrees of random jitter. The data show that (1) rms sinusoidal and random jitter in a periodic train of bursts are approximately equally detectable. (2) Sinusoidal jitter detection depends upon burst period duration and the short‐term envelope definition and not upon frequency‐domain information. (3) For a given burst period, stimulus jitter and an internal temporal noise appear to add independently to determine period discriminability. (4) Psychophysical estimates of internal temporal noise are 0.160 and 0.710 msec at periods of 5 and 10 msec, respectively. The data are consistent with the hypothesis that the burst period discrimination task is based upon a measurement of the time interval (duration) between spikes in auditory neurons.

Capacities of the goldfish for intensity discrimination were studied using classical respiratory conditioning and a staircase psychophysical procedure. Physiological studies on single saccular (auditory) nerve fibers under similar stimulus conditions helped characterize the dimensions of neural activity used in intensity discrimination. Incremental intensity difference limens (IDLs in dB) for 160‐ms increments in continuous noise, 500‐ms noise bursts, and 500‐ms, 800‐Hz tone bursts are 2 to 3 dB, are independent of overall level, and vary with signal duration according to a power function with a slope averaging −0.33. Noise decrements are relatively poorly detected and the silent gap detection threshold is about 35 ms. The IDLs for increments and decrements in an 800‐Hz continuous tone are about 0.13 dB, are independent of duration, and are level dependent. Unlike mammalian auditory nerve fibers, some goldfish saccular fibers show variation in recovery time to tonal increments and decrements, and adaptation to a zero rate. Unit responses to tone increments and decrements show rate effects generally in accord with previous observations on intracellular epsp’s in goldfish saccular fibers. Neurophysiological correlates of psychophysical intensity discrimination data suggest the following: (1) noise gap detection may be based on spike rate increments which follow gap offset; (2) detection of increments and decrements in continuous tones may be determined by steep low‐pass filtering in peripheral neural channels which enhance the effects of spectral ‘‘splatter’’ toward the lower frequencies; (3) IDLs for pulsed signals of different duration can be predicted from the slopes of rate–intensity functions and spike rate variability in individual auditory nerve fibers; and (4) at different sound pressure levels, different populations of peripheral fibers provide the information used in intensity discrimination.

Patterns of activity in single fibers of the saccular branch of the auditory nerve of goldfish were analyzed in response to acoustic stimulation. Neurons were categorized on the basis of differences in spontaneous activity patterns, rates of adaptation, and frequency response areas. The sensitivity and responsiveness of neurons are presented both in terms of impulse rate and synchronization (phase locking). Nonspontaneous neurons fall into two clear frequency response area categories based upon impulse rate criteria. Spontaneously active neurons have continuously distributed frequency response characteristics based upon synchronization criteria. Functions relating impulse rate responsiveness to frequency indicate that frequency is coded only crudely as an across‐fiber pattern of impulse rates. Synchronization responsiveness functions show that frequency is coded temporally with the same precision in the goldfish auditory nerve that it is in mammals, at 1000 Hz and below.