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PubMed1994

Nonprimary auditory thalamic representation of acoustic change.

1. The mismatch response, or mismatch negativity (MMN), is a neurophysiologic response to stimulus change. In humans and other animals, the MMN may underlie the ability to discriminate acoustic differences, a fundamental aspect of auditory perception. 2. This study investigated the role of the thalamus in the generation of a tone-evoked MMN in guinea pigs. Electrodes were placed in the caudomedial (nonprimary) and ventral (primary) subdivisions of the auditory thalamus (medial geniculate nucleus). Surface epidural electrodes were placed at the midline and over the temporal lobe. The MMN was elicited by a deviant stimulus (2,450-Hz tone burst) embedded in a sequence of standard stimuli (2,300-Hz tone bursts). 3. A tone-evoked MMN was present in nonprimary thalamus but was absent in the primary thalamus. Surface-recorded MMNs were measured at the midline but not over the temporal lobe. The correspondence between nonprimary thalamic responses and midline surface potentials, and between primary thalamic responses and temporal surface potentials, is consistent with data reported for the auditory middle latency responses in guinea pigs. 4. The results demonstrate that the nonprimary auditory thalamus contributes to the generation of a tone-evoked MMN in the guinea pig. Furthermore, the data indicate that the guinea pig is a feasible model for investigating central auditory processes underlying acoustic discrimination.

Acoustic Stimulation↗
PubMedDate not supplied

Discrimination of frequency ramps in subjects with cochlear hearing loss.

The auditory sensitivity for detecting linear frequency sweeps of a continuous pure tone has been studied in ten young subjects with cochlear hearing loss. The mean thresholds were elevated by a factor of 2.8 as compared with a normal group over the whole range of ramp durations studied (10-500 msec). The results show that this elevation is most likely caused mainly by the cochlear lesion per se, other possible factors having only a minor effect. No clear correlations could be found between thresholds for frequency change and results of other pure tone audiometric tests. Such tests thus cannot predict a subject's frequency discrimination.

Acoustic Stimulation↗
PubMed1990

Categorical perception of nonspeech chirps and bleats.

Mattingly, Liberman, Syrdal, and Halwes, (1971) claimed to demonstrate that subjects cannot classify nonspeech chirp and bleat continua, but that they can classify into three categories a syllable place continuum whose variation is physically identical to the nonspeech chirp and bleat continua. This finding for F2 transitions, as well as similar findings for F3 transitions, has been cited as one source of support for theories that different modes or modules underlie the perception of speech and nonspeech acoustic stimuli. However, this pattern of finding for speech and nonspeech continua may be the result of research methods rather than a true difference in subject ability. Using tonal stimuli based on the nonspeech stimuli of Mattingly et al., we found that subjects, with appropriate practice, could classify nonspeech chirp, short bleat, and bleat continua with boundaries equivalent to the syllable place continuum of Mattingly et al. With the possible exception of the higher frequency boundary for both our bleats and the Mattingly syllables, ABX discrimination peaks were clearly present and corresponded in location to the given labeling boundary.

Animals↗
PubMed1990

Intensity discrimination and loudness for tones in broadband noise.

In two previous papers (Parker & Schneider, 1980; Schneider & Parker, 1987), we developed a model, based on Fechner's assumption, which successfully predicted the relationship between loudness and intensity discrimination for tones presented in quiet and in notched noise. In the present paper, pure-tone intensity-increment thresholds and loudness matches were determined for several levels of a standard tone in the presence of a broadband masker whose spectrum level was set to 35 dB below that of the standard tone. The model was unable to relate loudness to intensity discrimination under these conditions. Thus, the spectral composition of the masker affects the relationship between loudness and intensity discrimination in ways that cannot be accounted for by the model.

Adult↗
PubMed2006

Binaural pitch perception in normal-hearing and hearing-impaired listeners.

The effects of hearing impairment on the perception of binaural-pitch stimuli were investigated. Several experiments were performed with normal-hearing and hearing-impaired listeners, including detection and discrimination of binaural pitch, and melody recognition using different types of binaural pitches. For the normal-hearing listeners, all types of binaural pitches could be perceived immediately and were musical. The hearing-impaired listeners could be divided into three groups based on their results: (a) some perceived all types of binaural pitches, but with decreased salience or musicality compared to normal-hearing listeners; (b) some could only perceive the strongest pitch types; (c) some were unable to perceive any binaural pitch at all. The performance of the listeners was not correlated with audibility. Additional experiments investigated the correlation between performance in binaural-pitch perception and performance in measures of spectral and temporal resolution. Reduced frequency discrimination appeared to be linked to poorer melody recognition skills. Reduced frequency selectivity was also found to impede the perception of binaural-pitch stimuli. Overall, binaural-pitch stimuli might be very useful tools within clinical diagnostics for detecting specific deficiencies in the auditory system.

Adult↗
PubMed1989

Identification and discrimination of sweep formants.

Earlier identification experiments with sweep tones are repeated with rising and falling single formant (band) sweeps, with durations ranging from 15 to 40 msec and sweep rates from 0 to 40 oct/sec. Steady-state portions of 100-msec duration are then added to the sweeps. The general conclusions are that the tendency to perceive level and slightly rising tones as falling, which was such a prominent feature of the earlier results, disappears as the stimuli become more complex, and that sweep discrimination seems to be a function of the difference between the initial and the final frequency of a sweep.

Attention↗
PubMed1991

Discrimination of second-format-like frequency transitions.

Discrimination of two types of simulated single-second-format frequency transitions was studied, transitions where members of a stimulus set shared the same onset frequency and transitions where stimuli of a set shared the same offset frequency. Experiment 1 employed an adaptive procedure to measure just-noticeable differences for transitions that increased in frequency. Experiment 2 obtained complete psychometric functions, based on a three-interval, forced-choice procedure, for transitions that either increased or decreased in frequency. In both experiments, better discrimination occurred for longer stimuli, measured in hertz/millisecond, and for transitions that shared the same onset frequency. There were no differences, in Experiment 2, between discrimination of rising and falling transitions. Results are considered from several theoretical perspectives.

Adult↗
PubMed2003

Perceptual weights in auditory level discrimination.

Perceptual weights in level discrimination (also called intensity discrimination) were determined for 3-, 7-, 15-, and 24-component tone complexes with flat spectral envelopes using a correlational paradigm. Each frequency component was randomly and independently perturbed in level oneach presentation. For the target interval, frequency-component levels were additionally increased by the level increment to be detected, deltaL [= 201og10((p + deltap)/p), where p is pressure]. Weights were calculated from the across-trial correlation between the level perturbations for each frequency component and the interval chosen by the listener. Two conditions were investigated: (1) deltaL was equal across frequency components, and (2) deltaL increased progressively across frequency components. For both conditions, data for four listeners usually showed the greatest weight for the highest frequency component. The two-to-four highest frequency components generally were most important for level discrimination. The effect of increasing deltaL progressively with frequency was small and inconsistent. Additional measurements showed that flanking noise maskers designed to mask spread of excitation caused only small and generally unsystematic changes to the weights. Overall, these results indicate that listeners combine information across a wide range of auditory channels to arrive at a decision for level discrimination, but the weighting of channels appears to be suboptimal.

Adult↗
PubMed1986

Level discrimination of tones as a function of duration.

Difference limens for level [delta Ls (dB) = 20 log[p + delta p)/p), where p is the pressure] were measured as a function of duration for tones at 250, 500, and 8000 Hz. Stimulus durations ranged from 2 ms to 2 s, and the stimulus power was held constant. Rise and fall times were 1 ms. The interstimulus interval was 250 ms. At each frequency, three levels were tested: 85, 65, and approximately 40 dB SPL. An adaptive two-alternative forced-choice procedure with feedback was used. For three normal listeners, delta Ls decreased as duration increased, up to at least 2 s, except at 250 Hz. At 250 Hz, delta L stopped decreasing at durations between 0.5 and 1 s. In a double logarithmic plot of delta L versus duration, the rate of decrease is generally well fitted by a sloping line. The average slope is -0.28; it is steeper at high levels than at low levels. Because the average slope is shallower than the -0.5 slope predicted for an optimum detector, it may be that fast adaptation of auditory-nerve activity and/or memory effects interfere with level discrimination of long-duration tones. Finally, the delta Ls at 8 kHz decreased nonmonotonically with increasing level.

Adult↗
PubMed1997

[Differences in auditory frequency discrimination ability in musicians of different specialties].

The frequency discrimination capacity of 63 musicians of different specialties (singers, string players, wood and brass players, pianists and rhythm teachers) was investigated using a binaural frequency discrimination test. Statistically significant differences between the groups of musicians were found. The string players revealed the highest tuning reproducibility. The results show that frequency discrimination capacity is influenced by specific phenomena of the instrumental education.

Adult↗
PubMed2005

Towards an understanding of speech and song perception.

The human singing voice plays an important role in music of all societies. It is an extremely flexible instrument and is capable of producing a tremendous range of sounds. As such, the human voice can be hard to classify and poses a major challenge for automatic audio discrimination and classification systems. Speech/song discrimination is an implicit goal of speech/music discrimination, where a division is sought between speech and song, such that the singing voice can be grouped together with other musical instruments in the same category. However, the division between speech and song is unclear and even human attempts at speech/song discrimination can be highly subjective and open to discussion. In this paper we present the results of a test that was designed to investigate differences in auditory perception for speech and song. Twenty-four subjects were instructed to attend to either the words or pitch, or both words and pitch of context-free spoken and sung phrases. After presentation of each phrase, subjects were asked to either type the words that they recalled, or select the correct pitch contour from a choice of four graphical representations, or do both, depending on the task specified before presentation of the phrase. The results of the experiment show a decrease in the amount of linguistic information retained by subjects for sung phrases and also a decrease in accuracy of response for the sung phrases when subjects attended to both words and pitch instead of words or pitch alone.

Adult↗
PubMed1989

Frequency discrimination in the goldfish (Carassius auratus): effects of roving intensity, sensation level, and the direction of frequency change.

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.

Acoustic Stimulation↗
PubMed1992

Asymmetrical discrimination of narrow-band stimuli.

A three-interval, forced-choice procedure that obtained complete psychometric functions was used to study frequency discrimination for 13-item continua of impulse-generated, narrow-band, buzz-like, steady-state sounds. For all subjects and durations, discrimination relative to the highest center frequency (1060 Hz) stimuli was better than discrimination relative to the lowest center frequency (940 Hz). This result is not in consonance with traditional reports of pure tone frequency discrimination and is not readily explained. However, additional experiments with similar stimuli replicated these findings.

Adult↗
PubMed2006

Roles of the auditory cortex in discrimination learning by rats.

We investigated the roles of the auditory cortex in sound discrimination learning in Wistar rats. Absolute pitch or relative pitch can be used as discrimination cues in sound frequency discrimination. To clarify this, rats were trained to discriminate between rewarded (S+) and unrewarded (S-) test stimuli (S+ frequency>S- frequency). After learning was acquired by rats, performance was tested in a new test in which S+ frequency was constant but S+ frequency S- frequency but both frequencies were increased. If the discrimination cue of the first test was preserved in the new test, performance following change of testing procedures was expected to remain high. The measured performance suggested that rats used relative pitch in half octave discrimination (difference between S+ and S- frequencies, 0.5 octave), and absolute pitch in octave discrimination (difference between S+ and S- frequencies, 1.0 octave). Bilateral lesions in the auditory cortex had almost no effect on performance before procedure change. Furthermore, performance following procedure change was not affected by lesions in the auditory cortex when the discrimination cue was preserved. However, performance was impaired by lesions in the auditory cortex when a new discrimination cue was used following procedure change. Lesions in the auditory cortex also impaired multimodal discrimination between sound and sound plus light. The present findings suggest that the auditory cortex plays a role as a sensory interface of the higher cortices required for flexible learning and multimodal discrimination.

Acoustic Stimulation↗
PubMedDate not supplied

Reimplantation of a molded scala tympani electrode: impact on psychophysical and speech discrimination abilities.

Revision surgery was successfully performed on two Vienna cochlear implant patients. Twenty months and 40 months, respectively, after initial insertion into the cochleas of two bilaterally deaf patients, electrodes were removed from the scala tympanis and replaced by electrodes of the same design. Psychophysical and speech data gathered before and after the revision surgery were compared. These were thresholds, loudness scalings, amplitude difference limens, pitch scalings, frequency difference limens, and speech tests in the "stimulation only" modality. No negative changes were found. The data available demonstrate a continuous improvement in performance over many months of practice with the sound processor. This development was not impeded by the revision surgery. Thus, it was demonstrated that the removal and replacement of a molded scala tympani electrode is feasible.

Adult↗
PubMed1995

Tone discrimination performance in schizophrenic patients and normal volunteers: impact of stimulus presentation levels and frequency differences.

Psychophysical and cognitive studies carried out in schizophrenic patients show high within-group performance variance and sizable differences between patients and normal volunteers. Experimental manipulation of a target's signal-to-noise characteristics can, however, make a given task more or less difficult for a given subject. Such signal-to-noise manipulations can substantially reduce performance differences between individuals. Frequency and presentation level (volume) changes of an auditory tone can make a sound more or less difficult to recognize. This study determined how the discrimination accuracy of medicated schizophrenic patients and normal volunteers changed when the frequency difference between two tones (high frequency vs. low frequency) and the presentation levels of tones were systematically degraded. The investigators hypothesized that each group would become impaired in its discrimination accuracy when tone signals were degraded by making the frequencies more similar and the presentation levels lower. Schizophrenic patients were slower and less accurate than normal volunteers on tests using four tone levels and two frequency differences; the schizophrenic patient group showed a significant decrement in accuracy when the signal-to-noise characteristics of the target tones were degraded. The benefits of controlling stimulus discrimination difficulty in functional imaging paradigms are discussed.

Adult↗