Search PubMed⌕ Search

Biomedical subjects

R R Fay

Publications and source records attributed to R R Fay.

At least 55 records · Page 3Linked to original sources
PubMed1987

Response dynamics of goldfish saccular fibers: effects of stimulus frequency and intensity on fibers with different tuning, sensitivity, and spontaneous activity.

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.

Acoustic Stimulation↗
PubMed1986

Acoustic response and tuning in saccular nerve fibers of the goldfish (Carassius auratus).

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.

Acoustic Stimulation↗
PubMed1985

Adaptation effects on amplitude modulation detection: behavioral and neurophysiological assessment in the goldfish auditory system.

The ability of goldfish to detect the presence of amplitude modulations (AM) impressed on 200, 570 and 800 Hz tones was measured under stimulus conditions producing intermittent, short-term adaptation and continuous, long-term adaptation. Sensitivity to AM under intermittent conditions increased as a function of modulation rate, with thresholds of AM detection occurring between 10 and 25% modulation at 10 Hz and around 2% modulation at 100 Hz. AM sensitivity was independent of carrier frequency and did not change under randomly varying intensity changes. Under long-term adaptation, thresholds of AM detection ranged from 1.3% at 100 Hz to 2.1% at 10 Hz, showing increased sensitivity and less dependence on modulation rate. The effects of overall intensity on AM sensitivity were the same for both conditions, with sensitivity being relatively independent of overall signal level at 10 Hz modulation and dependent on level at 100 Hz. The responses of goldfish auditory neurons to modulated and unmodulated signals were measured under stimulus conditions similar to those for behavioral studies. Single saccular neurons responded to modulated signals with both an increase in average rate above that evoked by the unmodulated signal and with phase-locking to the AM envelope. Rate increments and phase-locking responses were observed in neurons showing significant short-term adaptation to the unmodulated signal, whereas neurons showing no increase in rate or synchronization to the AM envelope showed little or no adaptation to the unmodulated signal. The effects of overall intensity, modulation rate and adaptation duration on neural responses were similar to behaviorally measured effects. These results show that adaptation affects AM detection and that phase-locking to the AM envelope is the most likely basis for behavioral detection.

Acoustic Stimulation↗
PubMed1985

Sound intensity processing by the goldfish.

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.

Acoustic Stimulation↗
PubMed1984

The goldfish ear codes the axis of acoustic particle motion in three dimensions.

Auditory and vestibular nerve fibers of the goldfish are strongly directionally sensitive to whole-body acceleration at audio frequencies. The three-dimensional pattern of sensitivity shows that input from a receptor ensemble (hair cells) is essentially equivalent to that expected from a single hair cell having a given three-dimensional orientation of best sensitivity. Fibers from the sacculus, lagena, and utriculus differ with respect to distributions of directional orientation, but are similar in best threshold (less than 1 nanometer, root mean square, at 140 hertz). In combination with other mechanisms for detection of sound pressure, this directionality is a likely basis for directional hearing in fishes, and it could allow the determination of underwater acoustic intensity.

Acoustic Stimulation↗
PubMed1983

Neural mechanisms in sound detection and temporal summation.

The psychophysics and neurophysiology of sound detection in quiet and under noise masking were studied in goldfish. Psychophysical masking is a linear function of masker level. For long duration signals, signal-to-noise ratios (S/N) at threshold are 15.5, 19, and 22.5 dB for 200, 400 and 800 Hz signals, respectively, and is -5 dB for a noise signal. Threshold declines with signal duration to about 700 ms. The slopes of the masked temporal summation functions are about unity, indicating that energy is constant at threshold. In quiet however, the slopes are generally less than 0.5, indicating that shorter signals are detected at lower energy. Neural correlates of the masked S/Ns and the slopes of temporal summation functions were sought in the response patterns of single saccular neurons. Rate- and synchronization-intensity functions were obtained for tone and noise signals in quiet and in noise. S/Ns at behavioral threshold correspond closely to those required to raise spike rate just above that evoked by the masker alone, but are well above those required to cause clear synchronization. Therefore, sound detection is probably based on spike rate and not synchronization criteria. The equivalence of behavioral and neural thresholds indicates that the filters used in behavioral sound detection are simply the bandwidths of saccular fibers. A model outlined by Zwislocki which predicts the rate of temporal summation from the rate of growth of neural activity with intensity accounts quite well for the observed slopes of temporal summation functions both in quiet and in noise.

Action Potentials↗
PubMed1983

Psychophysics and neurophysiology of repetition noise processing in a vertebrate auditory system.

The psychophysics and neurophysiology of repetition noise (RN) processing was studied in the goldfish. RN is the sum of a noise waveform with its delayed (by T s) repetition, which may be attenuated (by A dB), and inverted relative to the undelayed signal. Such a signal has a periodic spectrum with peaks separated by 1/T Hz, and a prominence in its autocorrelation function at T s. In usual environments, RN contains information about sound-reflecting surfaces. Delays in the range of 0.5-20 ms create pitch sensations in man. Psychophysical experiments using classical respiratory conditioning investigated the masking effectiveness of RN on tones, the detection of changes in delay (T) at various values of T, A and overall noise level, and the values of A required to bring a 20% delay discrimination to threshold. While the masking data define detection filters quite broadly tuned compared with man, various measures of delay discrimination are comparable to those for man. Unit responses from the auditory nerve are consistent with broadly tuned psychophysical filters, but in all cells studied show prominent inter-spike-interval (ISI) peaks which predict the delay values used to generate the RN. We conclude that the qualitative features of RN are coded in ISIs, and are processed by the CNS in the time domain. Similar mechanisms may be used by other vertebrate species in processing repetition noise.

Animals↗
PubMed1982

Temporal discrimination in the goldfish.

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.

Animals↗
PubMed1978

Coding of information in single auditory-nerve fibers of the goldfish.

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.

Action Potentials↗
PubMed1978

Auditory masking patterns in the goldfish (Carassius auratus): psychophysical tuning curves.

The masking effects of tones on the detection auditory signals were studied in goldfish using the psychophysical tuning-curve paradigm. For signals below 350 Hz, masking is an inverse function of the frequency separation between masker and signal; a finding consistent with previous masking studies on fishes, birds and mammals. For signals above 350 Hz, masking peaks occur both in the 350 Hz region and at the frequency of the signal. Quantitative comparisons with recent neural tuning curves for goldfish saccular neurones suggest that the filtering observed may be determined by mechanical frequency selectivity below 350 Hz, but by a neural analysis of temporal patterns above this range.

Animals↗
PubMed1978

Psychophysical tuning curves in vibrotaction.

The frequency-response characteristics of channels used in human vibrotaction were studied by using a psychophysical tuning-curve paradigm derived from auditory research. Sinusodial 200-msec vibratory bursts delivered to the thenar eminence of the hand were detected in the presence of sinusodial maskers delivered to the same skin area either continuously or pulsed in forward masking. Psychophysical tuning curves were obtained by determining the intensity of maskers of varied frequency necessary to mask a 10-dB SL test stimulus of fixed frequency. The results support the notion that at least two independent channels operate in human vibrotaction. There was no evidence for frequency selective mechanisms other than those at the periphery. Psychophysical tuning curves were similar to neural tuning curves for individual cutaneous mechanoreceptors.

Adult↗
PubMed1975

Modes of stimulation of the teleost ear.

Microphonic potentials were recorded from the inner ears of a catfish (Ictalurus punctatus) and an African mouthbreeder (Tilapia macrocephala) in response to underwater sound stimulation and direct vibration of the head. The shape of the vibratory isopotential functions of frequency was similar in both species up to 600 HZ. Above 600 HZ, the sensitivity of Ictalurus continued to increase to 4000 HZ while the sensitivity of Tilapia declined. Deflation of the swim bladder did not affect the response to vibration in either species, the response of Tilapia to the underwater sound stimulus being minimal and unaffected by removal of the swim bladder. Ictalurus was pressure-sensitive to above 4000 HZ, ther being a significant dedline in the response with deflation of the swimbladder.

Acoustic Stimulation↗