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Classical conditioning of respiration has been used to study many aspects of hearing in the goldfish, including absolute and masked thresholds, frequency, intensity, and time discrimination thresholds. A restrained fish is presented with a 7-s auditory signal that ends with a brief electric shock across the body. Shock causes an unconditioned suppression of respiration lasting several seconds. Several pairings of the auditory signal with the shock results in respiratory suppression during the signal. Initial conditioning is rapid (conditioned responses appear within the first 10 to 20 trials), several thresholds can be obtained in one day, and thresholds can be obtained for individual animals for several years. Critical factors for success with this method include the measurement of respiration (using a thermistor), method of animal restraint, levels of electric shock, intertrial intervals, false alarm estimation, overall respiratory rate, subject selection, and water conditioning. Details of the methods and procedures that have been found useful in conditioning and threshold definition will be given along with illustrative data on threshold values and stability in masking and intensity discrimination experiments. [ABSTRACT FROM AUTHOR]

Earlier studies on the ability of goldfish to detect amplitude-modulated (AM) noise signals [R. R. Fay, J. Neurophysiol. 44, 312-332 (1982)] suggested that goldfish were fundamentally different from other animals, including humans, in showing a flat modulation sensitivity function and no drop-off in sensitivity out to modulation rates of 400 Hz. To re-examine this anomaly, modulation sensitivity was measured in the goldfish at different sensation levels, using several experimental procedures and an improved technique for specifying the underwater acoustic stimulus at high modulation rates. Modulation sensitivity was found to be independent of sensation level at 10- and 100-Hz modulation. Sensitivity functions were relatively flat at modulation rates below 50-100 Hz with thresholds of AM detection occurring between 30% and 40% modulation. Greater than 60%-70% modulation was required for detection at 400 Hz. Randomly varying the overall intensity of unmodulated comparison noises and modulated noise signals produced little change in sensitivity or in the overall shape of the modulation function. These results show that the ability of goldfish to detect amplitude-modulated noise is not heavily dependent on intensity cues, nor fundamentally different from that of other species. [ABSTRACT FROM AUTHOR]

An in-depth analysis of hearing sensitivity for the jewel cichlid, Hemichromis bimaculatus was made using neurophysiological techniques to measure sensitivity at various levels of the auditory system and psychophysical techniques to measure whole-system sensitivity. For physiological studies, fish were stimulated by sinusoids generated by a loudspeaker or by direct vibration of the fish's head. Microphonic potentials were recorded from the sacculus of the inner ear and evoked potentials were recorded at several depths from the forebrain, midbrain, cerebellum, and medulla. For psychophysical studies, shock avoidance techniques were used in training fish to respond to tones generated by a loudspeaker. While audiograms based on the various neurophysiological and behavioral measures differed in detail, they showed in general that the auditory system of the jewel cichlid responds to sounds between 70 and 600 Hz, with best sensitivity in the region of 100 to 300 Hz. Evidence exists that within the frequency region of best sensitivity, the auditory system responds to both sound pressure and particle motion. The methodological difficulties in obtaining independent measures of sensitivity to pressure and particle motion will be discussed. [Supported by grants from NSF and NIH to R.F. and A.P.] [ABSTRACT FROM AUTHOR]

Behavorial audiograms have been obtained from two different species of squirrelfishes (Family: Holocentridae). Lowest thresholds measured for Myripristis kuntee were -50 dB re dyn/cm2 for frequencies extending from 300 to 2000 Hz, whereas best sensitivity measured for Adioryx xantherythrus was -28 dB at 500 Hz. While the low frequency end of the auditory range was at least 100 Hz for both species, the high end extended up to 800 Hz for A. xantherythrus and to 3000 Hz for M. kuntee. The two species tested can be taxonomically distinguished by anatomical differences in their peripheral auditory system. The genus Myripristis is characterized by anterior projections of the swimbladder which abut against the inner ear cavity, whereas in the genus Adioryx, the swimbladder lacks projections and is situated some distance away from the inner ear cavity [E. M. Nelson, Fieldiana: Zool. 37, 121-130 (1955)]. It is hypothesized that these anatomical variations affect the way sound reaches the inner ear, resulting in the reported differences in thresholds and frequency range of hearing. [Supported by NIH grant NS-15090.] [ABSTRACT FROM AUTHOR]

Old World monkeys were exposed to octave-band or wide-band noise at 117-120 dB SPL, 8 hours daily, five days per week for four weeks. The octave bands were centered at 500, 2000, 4000, or 8000 Hz. Thresholds for frequencies 63-40 000 Hz were measured daily before, during, and for one month after exposure, by the staircase method, using operant conditioning procedures with positive reinforcement. After the final threshold measurements the temporal bones were fixed and the inner ears examined by microdissection and phase-contrast microscopy. Maximum TTS, usually attained on the first day of exposure, ranged from 60 to 100 dB; PTS, from 40 to 60 dB. Both temporary and permanent loss involved at least two or three octaves and for the most part were greatest at, or within the octave above, the center of the exposure band. Hair cell counts showed reasonable correspondence between the location, severity, and extent (5-12 mm) of outer hair cell loss and the degree of PTS, in accordance with the place principle. In addition, most animals showed complete loss of outer and inner hair cells at the extreme basal end, usually correlated with a hearing loss for the highest frequencies. [Research supported by grants from NIH.] [ABSTRACT FROM AUTHOR]

This paper gives a brief synopsis of the research career of S.C. in fish bioacoustics with an emphasis on dipole near fields. The hydroacoustic nature of the dipole near field and the effective stimuli to lateral line and auditory systems combine to produce a multisensory, range-fractionated region that is critically important to many fish behaviors. The mottled sculpin and goldfish lateral lines encode the spatial complexities of the near field as spatial excitation patterns along the body surface to provide instantaneous snapshots of various source features such as distance, orientation, and direction of movement. In contrast, the pressure-sensitive channel of the goldfish auditory system [the anterior swim bladder (SB)-saccule complex] encodes the spatial complexities in a temporal fashion whenever the position or orientation of the source changes with respect to the anterior SB. A full appreciation for how these somatotopic and egocentric representations guide fish behavior requires an understanding of how multisensory information, including vision, is combined in sensorimotor regions of the brain to effect behavior. A brief overview of vertebrate brain organization indicates that behaviors directed to or away from hydroacoustic sources likely involve a variety of mechanisms, behavioral strategies, and brain regions., (© 2023 Acoustical Society of America.)

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.

Mottled sculpin (Cottus bairdi) are small, benthic fish that avoid being swept downstream by orienting their bodies upstream and extending their large pectoral fins laterally to generate negative lift. Digital particle image velocimetry was used to determine the effects of these behaviors on the spatial and temporal characteristics of the near-body flow field as a function of current velocity. Flow around the fish's head was typical for that around the leading end of a rigid body. Flow separated around the edges of pectoral fin, forming a wake similar to that observed for a flat plate perpendicular to the flow. A recirculation region formed behind the pectoral fin and extended caudally along the trunk to the approximate position of the caudal peduncle. In this region, the time-averaged velocity was approximately one order of magnitude lower than that in the freestream region and flow direction varied over time, resembling the periodic shedding of vortices from the edge of a flat plate. These results show that the mottled sculpin pectoral fin significantly alters the ambient flow noise in the vicinity of trunk lateral line sensors, while simultaneously creating a hydrodynamic footprint of the fish's presence that may be detected by the lateral line of nearby fish.

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.(ABSTRACT TRUNCATED AT 250 WORDS)

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 hot-film anemometer system has been calibrated and evaluated for the measurement of sinusoidal water motions used in stimulating the mechanosensory lateral line system of a teleost fish. The response of the anemometer system to water motions created by a vibrating sphere was measured over a wide range of frequencies, intensities, and distances from the sphere. The amplitude response of the system to signals along the axis of sphere vibration was found to be linear over a 50-dB range for frequencies from 10-200 Hz, with the lowest end of the dynamic range (between 10(-8) and 10(-9) m) corresponding to physiological measures of best sensitivity in the lateral line system of the mottled sculpin, Cottus bairdi. The measured attenuation of the signal with distance was also linear over this frequency range out to distances of six times the radius ( = 3 mm) of the sphere and followed the predicted falloff rate for a dipolar source. The linear response of the anemometer system over a wide dynamic range encompassing the detection range of the lateral line system, and the match between predicted and measured motions at varying distances from a dipolar source, indicates that hot-film anemometry is a useful technique for measuring low-level, low-frequency signals likely to stimulate the lateral line system and other hydrodynamic detectors.

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.

The effects of stimulus frequency and intensity on response patterns (PST histograms) to tone burst stimulation were examined in differently tuned saccular fibers of the goldfish. In addition, the sensitivity of these fibers to amplitude-modulated (AM) signals of different carrier frequencies was measured. The response patterns evoked by unmodulated signals were a complex function of tuning, spontaneous activity and sensitivity of the fiber, and the frequency and intensity of the signal. Frequency-dependent response patterns were found in low-frequency fibers with best frequencies (BF) below 200 Hz. Responses in these fibers ranged from tonic to phasic in nonspontaneous fibers and included more complex patterns in spontaneously active fibers, such as suppression of evoked activity below spontaneous levels. Midfrequency fibers (BF = 500-600 Hz) showed responses similar to those in low-frequency fibers, but with less dependence on frequency. In contrast, both high-frequency (BF = 800-1000 Hz) and wideband, untuned fibers showed frequency-invariant patterns of adaptation. High-frequency fibers were equally sensitive to AM signals at all frequencies tested. The sensitivity of low-frequency fibers to AM, however, increased as a function of carrier frequency and corresponded to the degree of adaptation in response to unmodulated tones. In general, the AM sensitivity of a fiber could be predicted more by its pattern of response to unmodulated signals than by its tuning characteristics.