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PubMed1989

Age differences in discrimination of simulated single-formant frequency transitions.

We studied auditory discrimination of simulated single-formant frequency transitions that resembled portions of certain speech consonants. Significant age differences in transition discrimination occurred; both children and older adults required larger acoustic differences between transitions for discrimination than did teenagers/young adults. Longer transitions were more easily discriminated than shorter transitions by all listeners, and there were no differences between discriminations of rising and falling transitions. Teens/young adults and older adults, but not children, required larger frequency differences to discriminate frequency transitions followed by a steady-state sound than for transitions alone. There were also age differences in discrimination of steady-state sounds. These developmental-perceptual differences may help explain why children and older adults who have good pure-tone sensitivity may experience difficulty in understanding speech.

Adolescent↗
PubMed2004

Patterns of deficit in auditory temporal processing among dyslexic adults.

We characterized temporal psychoacoustic performance in a group of adult dyslexics with excellent cognitive abilities. These individuals performed adequately on a two-tone frequency discrimination task when inter-stimulus intervals were long ( > or =1 s or more). However, their performance gradually deteriorated as interval duration was shortened (0.7- 0.1 s). Dyslexics with similar reading abilities, but with average cognitive abilities, performed poorly at all intervals. These findings show that, though both groups suffer from non-phonological deficits in auditory discrimination, the nature of their deficits differs. Dyslexics with excellent cognitive abilities seem to have slow, yet adequate, stimulus identification and comparison mechanisms. The fundamental impairment of the other dyslexic group is difficult to determine because their performance was poor across all intervals.

Acoustic Stimulation↗
PubMed1985

[Hearing in advanced age: critical view of so-called presbycusis].

Presbycusis cannot be defined nosologically as an uniform disease. The computed threshold curves of the age dependent high-frequency hearing loss should not conceal the fact that the degree and form of the hearing loss vary greatly within the age groups. The pathological appearances also vary; degenerative changes vary in site and extent and are not limited to the cochlear structures, but are also found in all parts of the auditory system. The etiology of presbycusis can scarcely be attributed to the physiological senile degeneration of cochlear or central nervous structures alone because epidemiological studies suggest that without additional endogenous and exogenous noxious effects the hearing loss progresses more slowly than under the influence of these effects. Therefore, presbycusis, in the sense of a socially handicapping hearing loss, is not an invariable lesion of the auditory system (mainly of the inner ear) due to a combination of different etiological factors. There are only two possible treatments: (1) elimination of exogenous and endogenous noxious effects in the hope of delaying the progress of the hearing loss and (2) fitting of a hearing aid. The open high-tone CROS-aid seems to provide a sufficient discrimination gain which is especially valuable for the typical high tone hearing loss in aged people. The necessity for a careful follow-up is emphasised.

Aged↗
PubMed1987

Auditory filtering and the discrimination of spectral shapes by normal and hearing-impaired subjects.

A review of the literature suggests that many hearing-impaired patients suffer from sensory deficits in addition to the reduced audibility of speech signals. Poor frequency resolution, or abnormal spread of masking, is a consistently identified deficit in sensorineural hearing loss. Frequency resolution was measured in individual subjects using the input filter pattern paradigm, and the minimum detectable amplitude of a second-formant spectral peak in a spectral-shape discrimination task was also determined for each subject. The two tasks were designed to test the identical frequency regions in each subject. A nearly perfect correlation was found between the degree of frequency resolution as measured by the input filter pattern and performance on the spectral-shape discrimination task. These results suggest that measures of frequency selectivity may offer predictive value as to the degree of impairment that individual hearing-impaired patients may have in perceiving the spectral characteristics of speech, and also lead to suggestions for signal processing strategies to aid these patients.

Auditory Threshold↗
PubMed1987

Temporal changes in a complex spectral profile.

The spectral properties of a complex stimulus (rippled noise) were varied over time, and listeners were asked to discriminate between this stimulus and a flat-spectrum, stationary noise. The spacing between the spectral peaks of rippled noise was changed sinusoidally as a function of time, or the location of the spectral peaks of rippled noise was moved up and down the spectrum as a sinusoidal function of time. In most conditions, listeners were able to make the discriminations up to rates of temporal modulation of 5-10 cycles per second. Beyond 5-10 cps the rippled noise with the temporally varying peaks was indiscriminable from a flat (nonrippled) noise. The results suggest that for temporal changes in the spectral peaks of rippled noise, listeners cannot monitor the output of a single (or small number of) auditory channel(s) (critical bands), or that the mechanism used to extract the perceptual information from these stimuli is slow. Temporal variations in the spectral properties of rippled noise may relate to temporal changes in the repetition pitch of complex sounds, the temporal properties of the coloration added to sound in a reverberant environment, and the nature of spectral peak changes such as those that occur in speech-formant transitions. The results are relevant to the general issue of the auditory system's ability to extract information from a complex spectral profile.

Auditory Pathways↗
PubMed2007

Abnormal frequency discrimination in children with SLI as indexed by mismatch negativity (MMN).

For several decades, the aetiology of specific language impairment (SLI) has been associated with a central auditory processing deficit disrupting the normal language development of affected children. One important aspect for language acquisition is the discrimination of different acoustic features, such as frequency information. Concerning SLI, studies to date that examined frequency discrimination abilities have been contradictory. We hypothesized that an auditory processing deficit in children with SLI depends on the frequency range and the difference between the tones used. Using a passive mismatch negativity (MMN)-design, 13 boys with SLI and 13 age- and IQ-matched controls (7-11 years) were tested with two sine tones of different frequency (700Hz versus 750Hz). Reversed hemispheric activity between groups indicated abnormal processing in SLI. In a second time window, MMN2 was absent for the children with SLI. It can therefore be assumed that a frequency discrimination deficit in children with SLI becomes particularly apparent for tones below 750Hz and for a frequency difference of 50Hz. This finding may have important implications for future research and integration of various research approaches.

Acoustic Stimulation↗
PubMed2001

Long-lasting memory of sounds combined with reward in rats.

We investigated the effects of sound stimuli combined with reward on the subsequent sound discrimination. Water-deprived rats were exposed to one of two sounds (S+ or S-) in a trial, and licking a spout only during the presentation of S+ was rewarded with water. The percentage of trials in which licking occurred was calculated separately for S+ and S-, and sound discrimination was estimated from the difference in the percentage. S+ and S- were significantly discriminated during an 8 h period. In the second test after 1-2 weeks, sound discrimination for the same S+ and S- was significantly better than that for the S+ of the previous S- and S- of the previous S+. These findings indicate that the memory of the sounds combined with reward in the first test was maintained for 1-2 weeks.

Acoustic Stimulation↗
PubMed1998

Loudness perception and frequency discrimination in subjects with steeply sloping hearing loss: possible correlates of neural plasticity.

Loudness functions and frequency difference limens (DLFs) were measured in five subjects with steeply sloping high-frequency sensorineural hearing loss. The stimuli were pulsed pure tones encompassing a range of frequencies. Loudness data were obtained using a 2AFC matching procedure with a 500-Hz reference presented at a number of levels. DLFs were measured using a 3AFC procedure with intensities randomized within 6 dB around an equal-loudness level. Results showed significantly shallower loudness functions near the cutoff frequency of the loss than at a lower frequency, where hearing thresholds were near normal. DLFs were elevated, on average, relative to DLFs measured using the same procedure in five normally hearing subjects, but showed a local reduction near the cutoff frequency in most subjects with high-frequency loss. The loudness data are generally consistent with recent models that describe loudness perception in terms of peripheral excitation patterns that are presumably restricted by a steeply sloping hearing loss. However, the DLF data are interpreted with reference to animal experiments that have shown reorganization in the auditory cortex following the introduction of restricted cochlear lesions. Such reorganization results in an increase in the spatial representation of lesion-edge frequencies, and is comparable with the functional reorganization observed in animals following frequency-discrimination training. It is suggested that similar effects may occur in humans with steeply sloping high-frequency hearing loss, and therefore, the local reduction in DLFs in our data may reflect neural plasticity.

Acoustic Stimulation↗
PubMed1990

Timbre discrimination in zebra finch (Taeniopygia guttata) song syllables.

Zebra finch (Taeniopygia guttata) songs include syllables of a fundamental frequency and harmonics. Individual harmonics in 1 syllable can be more or less emphasized. The functional role of this variability is unknown. These experiments provide evidence of how the phenomenon is perceived. We trained 12 male and female zebra finches on a go-no-go operant procedure to discriminate between 2 song syllables that varied only in the absence of the 2nd or 5th harmonic. Training involved many thousands of trials. Both sexes used the presence or absence of the 2nd harmonic as the sole discriminative cue. Females had more difficulty learning to perform the task when the presence of the 2nd harmonic was the go stimulus, which indicates that their use of the information was biased by stimulus-response contingencies. The results are discussed in terms of a broad strategy to understand how animals perceive sounds used in communication.

Animals↗
PubMed2001

Evaluating auditory performance limits: II. One-parameter discrimination with random-level variation.

Previous studies have combined analytical models of stochastic neural responses with signal detection theory (SDT) to predict psychophysical performance limits; however, these studies have typically been limited to simple models and simple psychophysical tasks. A companion article in this issue ("Evaluating Auditory Performance Limits: I") describes an extension of the SDT approach to allow the use of computational models that provide more accurate descriptions of neural responses. This article describes an extension to more complex psychophysical tasks. A general method is presented for evaluating psychophysical performance limits for discrimination tasks in which one stimulus parameter is randomly varied. Psychophysical experiments often randomly vary a single parameter in order to restrict the cues that are available to the subject. The method is demonstrated for the auditory task of random-level frequency discrimination using a computational auditory nerve (AN) model. Performance limits based on AN discharge times (all-information) are compared to performance limits based only on discharge counts (rate place). Both decision models are successful in predicting that random-level variation has no effect on performance in quiet, which is the typical result in psychophysical tasks with random-level variation. The distribution of information across the AN population provides insight into how different types of AN information can be used to avoid the influence of random-level variation. The rate-place model relies on comparisons between fibers above and below the tone frequency (i.e., the population response), while the all-information model does not require such across-fiber comparisons. Frequency discrimination with random-level variation in the presence of high-frequency noise is also simulated. No effect is predicted for all-information, consistent with the small effect in human performance; however, a large effect is predicted for rate-place in noise with random-level variation.

Animals↗
PubMed1992

Musical duplex perception: perception of figurally good chords with subliminal distinguishing tones.

In a variant of duplex perception with speech, phoneme perception is maintained when distinguishing components are presented below intensities required for separate detection, forming the basis for the claim that a phonetic module takes precedence over nonspeech processing. This finding is replicated with music chords (C major and minor) created by mixing a piano fifth with a sinusoidal distinguishing tone (E or E flat). Individual threshold intensities for detecting E or E flat in the context of the fixed piano tones are established. Chord discrimination thresholds defined by distinguishing tone intensity were determined. Experiment 2 verified masked detection thresholds and subliminal chord identification for experienced musicians. Accurate chord perception was maintained at distinguishing tone intensities nearly 20 dB below the threshold for separate detection. Speech and music findings are argued to demonstrate general perceptual principles.

Adult↗
PubMed1992

Discrimination and identification of modulation rate using a noise carrier.

Modulation-rate perception was measured for three tasks: a fixed-standard, forced-choice discrimination task with a 500-ms interstimulus interval; a random-standard, forced-choice discrimination task with an 8-s interstimulus interval; and an identification task. Thresholds were obtained for modulation rates from 14-224 Hz using noise carriers bandpass filtered from 500-4000 Hz, 500-1600 Hz, 1700-2800 Hz, and 2900-4000 Hz. The four bands yielded similar results except for modulation rates greater than 100 Hz, where the 500- to 1600-Hz thresholds were higher. Fixed-standard discrimination thresholds were about 3 Hz for modulation rates up to 66 Hz. The increase of thresholds for modulation rates above 66 Hz could be due to temporal resolution limits with a time constant of about 2-3 ms. For modulation rates above 100 Hz, critical-band filtering may further decrease sensitivity for the 500- to 1600-Hz noise band. Resolution in the random-standard discrimination task was similar to that for the identification task. Thresholds were elevated relative to fixed-standard thresholds except at the extremes of the stimulus range. In the random-standard discrimination task, a pronounced criterion bias was present for stimuli near the extremes of the range. Durlach and Braida's model [N. I. Durlach and L. D. Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)] describes the data well and provides quantitative measures for our data in good agreement with those for intensity perception.

Adult↗
PubMedDate not supplied

Present status and future directions of the Ear Research Institute cochlear implant program.

Thirty-three adult subjects have been implanted with single-electrode cochlear implants at the Ear Research Institute. This paper outlines the current status of the subjects; the rehabilitation and testing program; results found with the implant; and future directions of the implant program. Results indicate that implant subjects can score significantly above chance on a variety of discrimination tests. Implant subjects also score significantly better than hearing aid subjects on these tests. Research is continuing on engineering and signal-processing improvements for the single-elecrode implant. Multiple-electrode implants and binaural implants are being considered for future research at the Ear Research Institute.

Adult↗
PubMed2006

Separate neural processing of timbre dimensions in auditory sensory memory.

Timbre is a multidimensional perceptual attribute of complex tones that characterizes the identity of a sound source. Our study explores the representation in auditory sensory memory of three timbre dimensions (acoustically related to attack time, spectral centroid, and spectrum fine structure), using the mismatch negativity (MMN) component of the auditory event-related potential. MMN is elicited by a discriminable change in a sound sequence and reflects the detection of the discrepancy between the current stimulus and traces in auditory sensory memory. The stimuli used in the present study were carefully controlled synthetic tones. MMNs were recorded after changes along each of the three timbre dimensions and their combinations. Additivity of unidimensional MMNs and dipole modeling results suggest partially separate MMN generators for different timbre dimensions, reflecting their mainly separate processing in auditory sensory memory. The results expand to timbre dimensions a property of separation of the representation in sensory memory that has already been reported between basic perceptual attributes (pitch, loudness, duration, and location) of sound sources.

Adult↗
PubMed1991

The P300 component of the auditory event-related potential in monozygotic and dizygotic twins.

The P300 component of the auditory event-related potential was recorded from 10 pairs of monozygotic (MZ) twins and 11 pairs of dizygotic (DZ) twins during an auditory discrimination task. The within-pair similarity of P300 latency was significantly greater in MZ than in DZ twins. The within-pair similarity of P300 amplitude was not significantly greater in MZ than in DZ twins. These results support previous findings suggesting that P300 latency is largely genetically determined.

Adolescent↗
PubMed1990

Frequency discrimination in the monkey.

This study evaluated frequency discrimination ability in 11 monkeys over an extended period of time using a repeating-standard procedure and the method of constant stimuli. The intersubject variability of the difference limens for frequency (delta F) was large, as reported by other investigators, but similar in magnitude to the variability of the difference limens for intensity (delta I) from three of the same subjects in an intensity discrimination experiment. Continued training generally resulted in a rapid decrease in delta F's, followed by a longer-term, slower decrease. For one subject delta F's slowly decreased throughout a 190-week time period. This long-term training effect was specific to frequency discrimination; a similar effect was not observed for the same subject tested in an intensity discrimination experiment. Finally, delta F's from the well-trained monkeys of this study were larger than monkey delta F's from this laboratory reported in an earlier study, and than human delta F's. An anatomical explanation for the human/monkey delta F magnitude difference is explored.

Animals↗
PubMed1994

Listeners' expectations about echoes can raise or lower echo threshold.

Echo threshold increases with exposure to redundant trains of stimuli. Three experiments were conducted to test the hypothesis that a change in the ongoing train would affect listeners' perception of the echo, but only if it signified an unusual change in room acoustics. The stimulus train was composed of 4-ms narrow-band noise bursts, with the leading sound from a loudspeaker placed 45 degrees left of midline and the lagging sound or simulated echo from 45 degrees right, delivered in an anechoic chamber. The lagging sound in the test noise, which followed the train after a 750-ms pause, came randomly from loudspeakers at 35 degrees or 55 degrees right, and the listener's task was to choose which position the echo came from on each trial. In experiment 1 the delay between onsets of the leading and lagging bursts was varied between train and test bursts, which simulated a sudden movement of the reflecting surface either toward the listener (if the delay of the test burst was shorter than the train) or away (if the delay was longer). In both cases listeners detected the echo's direction more easily, compared to trials when there was no change between train and test burst delays. In order to check whether any change between train and test bursts would increase echo discriminability, experiment 2 varied frequency and experiment 3 varied intensity. These variations were not expected to affect the echo's detectability because such changes signify that the original sound changed in these characteristics and the echo reflected these changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed2002

Top-down gain control in the auditory system: evidence from identification and discrimination experiments.

The influence of intensity range in auditory identification and intensity discrimination experiments is well documented and is usually attributed to nonsensory factors. Recent studies, however, have suggested that the stimulus range effect might be sensory in origin. To test this notion, in one set of experiments, we had listeners identify the individual tones in a set. One baseline condition consisted of identifying four 1-kHz, low-intensity tones; the other consisted of identifying four 1-kHz, high-intensity tones. In the experimental conditions, these baseline tone sets were augmented by adding a fifth tone at either 1 or 5 kHz. Added 5-kHz tones had little effect on identification accuracy for the four baseline tones. When an added 1-kHz tone differed substantially in intensity from the four baseline tones, it adversely affected performance, with the addition of a high-intensity tone to a set of low-intensity tones having a more deleterious effect than the addition of a low-intensity tone to a set of high-intensity tones. These and further results, obtained in an exploration of this asymmetrical range effect in a third identification experiment and in two intensity-discrimination experiments, were consistent with the notion of a nonlinear amplifier under top-down control whose functions include protection against sensory overload from loud sounds. The identification data were well described by a signal-detection model using equal-variance Laplace distributions instead of the usual Gaussian distributions.

Adult↗