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PubMed1996

Induction of receptive field plasticity in the auditory cortex of the guinea pig during instrumental avoidance conditioning.

Classical tone conditioning shifts frequency tuning in the auditory cortex to favor processing of the conditioned stimulus (CS) frequency versus other frequencies. This receptive field (RF) plasticity is associative, highly specific, rapidly acquired, and indefinitely retained-all important characteristics of memory. The investigators determined whether RF plasticity also develops during instrumental learning. RFs were obtained before and up to 24 hr after 1 session of successful 1-tone avoidance conditioning in guinea pigs. Long-term RF plasticity developed in all subjects (N = 6). Two-tone discrimination training also produced RF plasticity, like classical conditioning. Because avoidance responses prevent full elicitation of fear by the CS, long-term RF plasticity does not require the continual evocation of fear, suggesting that neural substrates of fear expression are not essential to RF plasticity.

Animals↗
PubMed1990

The effect of modulation coherence on signal threshold in frequency-modulated noise bands.

A series of four experiments was undertaken to ascertain whether signal threshold in frequency-modulated noise bands is dependent upon the coherence of modulation. The specific goal was to determine whether a masking release could be obtained with frequency modulation (FM), analogous to the comodulation masking release (CMR) phenomenon observed with amplitude modulation (AM). It was hypothesized that an across-frequency grouping process might give rise to such an effect. In experiments 1-3, maskers were composed of three noise bands centered on 1600, 2000, and 2400 Hz; these were either comodulated or noncomodulated with respect to both FM and AM. In experiment 1, the modulation was sinusoidal, and the signal was a 2000-Hz pure tone; in experiment 2, the modulation was random, and the signal was an FM noise band centered on 2000 Hz. The results obtained showed that, given sufficient width of modulation, thresholds were lower in a coherent FM masker than in an incoherent FM masker, regardless of the pattern of AM or signal type. However, thresholds in multiband maskers were usually elevated relative to that in a single-band masker centered on the signal. Experiment 3 demonstrated that coherent FM could be discriminated from incoherent FM. Experiment 4 gave similar patterns of results to the respective conditions of experiments 2 and 3, but for an inharmonic masker with bands centered on 1580, 2000, and 2532 Hz. While within-channel processes could not be entirely excluded from contributing to the present results, the experimental conditions were designed to be minimally conducive to such processes.

Adult↗
PubMed1994

The measurement of the lateralization of narrow bands of noise using an acoustic pointing paradigm: the effect of sound-pressure level.

The effects of varying interaural time delay (ITD) and interaural intensity difference (IID) were measured in normal-hearing subjects as a function of eleven frequencies and at sound-pressure levels (SPL) from 60 to 90 dB SPL and at 25-dB sensation level. Using an "acoustic" pointing paradigm, the IID of a 500-Hz narrow-band (100 Hz) noise (the "pointer") was varied by the subject to coincide with that of a "target" ITD stimulus. ITDs of 0, +/- 200, and +/- 400 microseconds were obtained through total waveform delays of narrow-band noise (NBN), including envelope and fine structure. The results of this experiment confirm the traditional view of binaural hearing for like stimuli: There is little perceived displacement away from 0 IID at frequencies of 1250 Hz and above. In the low frequencies, subjects required IIDs greater than the expected 10 dB to perceive a fully lateralized image, and they varied in the maximum value of IID that they required, regardless of frequency. Our subjects did not always perceive the intracranial locations of ITD targets symmetrically: When the signal was delayed to one ear, the resultant matching IID was often different in magnitude than for the same ITD target delayed to the opposite ear for the identical frequency. The results of two subjects suggested that people with asymmetric normal hearing have adapted to their asymmetry for lateralization tasks: The subjects were found to lateralize toward the ear with the greater SPL stimulus, regardless of the ear to which the signal was delayed, when signals of equal SL were presented, and toward the leading ear when signals of equal SPL were presented (unequal SL). Increasing the presentation levels above 60 dB SPL had an effect on the perception of high-frequency ITD targets: As the intensity level increased, the slopes of the IID versus ITD functions increased indicating better discrimination of ITD. This study is in agreement with other studies in providing strong evidence of individual differences in lateralization experiments. These individual differences might be attributable to differential sensitivity to ambiguous time stimulus cues, differential task sensitivity, age effects, threshold asymmetries, or criterion variability.

Adult↗
PubMed2000

Hearing threshold and frequency discrimination in the purely aquatic frog Xenopus laevis (Pipidae): measurement by means of conditioning.

Hearing threshold and frequency discrimination for underwater sound were measured in the clawed frog Xenopus laevis by means of conditioning. A go/no go discrimination procedure was used in which the test tone was presented concurrently with a wave on the surface of the water. The tone signalled whether or not the frog should respond to the wave. The hearing range of X. laevis was 200-4000 Hz. Similar thresholds of 92-96 dB re 1 microPa were found at 600 Hz, 1400-1800 Hz and 3200-3600 Hz. A high threshold at 1000-1300 Hz suggested that this was the frequency range between the sensitivities of the amphibian and basilar papillae. Relative frequency discrimination was approximately 5 % at 400-800 Hz, 45 % at 1000 Hz and 2.4-6 % at 1600-2500 Hz. This last range encompasses the dominant frequencies of the advertisement call of this species. High discrimination acuity at these frequencies may be used in distinguishing between calling males. The threshold for a one-third-octave bandpass noise centred at 600 Hz was 27.6 dB lower than that for a pure tone of 600 Hz, suggesting that sound intensity was integrated within this bandwidth, possibly by a critical-band mechanism.

Animals↗
PubMed2002

Discrimination of individual vocalizations by black-capped chickadees (Poecile atricapilla).

The auditory perceptual abilities of male black-capped chickadees (Poecile atricapilla) were examined using an operant go/no-go discrimination among 16 individual vocalizations recorded at 5 m. The birds learned to discriminate about equally well among eight male chickadee fee-bee songs and eight female zebra finch (Taeniopygia guttata) distance calls. These results do not indicate that chickadees have a species-specific advantage in individual recognition for conspecific over heterospecific vocalizations. We then transferred the chickadees to a discrimination of the same songs and calls rerecorded at a moderate distance. These results showed accurate transfer of discrimination from 16 vocalizations recorded at 5 m to novel versions of the same 16 songs and calls rerecorded at 25 m. That is, chickadees recognized individual songs and calls despite degradation produced by rerecording at 25 m. Identifying individual vocalizations despite their transformation by distance cues is here described as a biologically important example of perceptual constancy.

Animal Communication↗
PubMed1982

Detection v discrimination of brief-duration tones. Findings in patients with temporal lobe damage.

Based on earlier experiments with cats, we have developed two new hearing tests to evaluate the ability of patients with temporal lobe damage to discriminate tones of short temporal duration. Earlier published studies suggested that patients exhibit notably increased thresholds for detecting tone pulses shorter than 200 ms in length when the signals are presented to the ear located contralateral to the damaged hemisphere. Our experiments with cats indicated that auditory cortex lesions had no effect on the cats' ability to detect brief tones but did impair their ability to discriminate small changes in the frequency of such signals. In giving the brief-tone tests to seven patients with temporal lobe damage, we found a similar behavioral dissociation. All patients exhibited normal detection thresholds in conjunction with substantially elevated frequency difference limina.

Adolescent↗
PubMed1978

Categorical perception--phenomenon or epiphenomenon: evidence from experiments in the perception of melodic musical intervals.

Categorical perception was investigated in a series of experiments on the perception of melodic musical intervals (sequential frequency ratios). When procedures equivalent to those typically used in speech-perception experiments were employed, i.e., determination of identification and discrimination functions for stimuli separated by equal physical increments), musical intervals were perceived categorically by trained musicians. When a variable-step-size (adaptive) discrimination procedure was used, evidence of categorical perception (in the form of smaller interval-width DL's for ratios at identification category boundaries than for ratios within categories), although present initially, largely disappeared after subjects had reached asymptotic performance. However, equal-step-size discrimination functions obtained after observers had reached asymptotic performance in the adaptive paradigm were not substantially different from those initially obtained. The results of other experiments imply that this dependence of categorical perception on procedure may be related to differences in stimulus uncertainty between the procedures. An experiment on the perception of melodic intervals by musically untrained observers showed no evidence for the existence of "natural" categories for musical intervals.

Humans↗
PubMed1991

Auditory pattern perception: the effect of tone location on the discrimination of tonal sequences.

This study examined the effect of tonal location on the discrimination of sequences differing in the order of the tones and on their perceived grouping. The frequency range between the sequential tones was held constant. When all tones came from the same location, the sequence was rated as integrated, but when the higher frequency tones came from a different location than the lower frequency tones, the sequence was rated as segregated. Listeners discriminated the sequences in a 3IFC task. Discrimination performance was impaired when the sequence was split between two locations and tonal order was changed in only one location, even though the order of tones in different locations was changed. This result suggests that listeners have difficulty relating tones across locations or in different perceptual groups. Performance in this experiment is generally better than that observed by Barsz (1988), and it is suggested that the level of stimulus uncertainty explains this difference.

Adult↗
PubMed1991

Korsakoff amnesics are poor at judging the sequence of two tones.

Alcoholic amnesics were given a test of temporal sequencing ability devised by Efron which has practically no memory component. These amnesics were very impaired on the task. However, the extent of this impairment did not relate to the magnitude of their "target memory" deficit nor did it relate to the ability to make temporal judgements from memory. Two other groups of amnesics (3 post-encephalitis and 4 with ruptured aneurysms of the anterior communicating artery) did not show impairments on the sequencing task. Data from the amnesic patient N.A. (who was unimpaired on the task), three other amnesics (who showed a tendency to be poor at the task) and two frontally damaged patients (one of whom performed especially badly on the sequencing task but had no obvious memory difficulties) were also presented. It is argued that deficits in temporal discrimination may not be found in all amnesics but, when they are observed, are an incidental feature related to additional (possibly cortical damage. Implications of the results for the view that amnesia results from a deficit in the use of contextual information (including temporal information) are considered.

Adult↗
PubMedDate not supplied

Backward and forward masking in listeners with severe sensorineural hearing loss.

Using synthetic stimuli, backward and forward masking by a first-formant stimulus were measured for two tasks: (1) discrimination of a second-formant transition and (2) pure-tone detection. 16 listeners with moderate to severe sensorineural hearing impairment were studied. Many of the listeners showed backward and forward discrimination masking, sometimes extending as far as 200 ms before or after the first-formant interval. There were large individual differences in degree and temporal extent of masking. The masking contribution of sensitivity shifts, as indicated by pure-tone detection levels, appeared to be limited to a range of only 50 ms before or after the first-formant masker.

Acoustic Stimulation↗
PubMed1984

Detection of frequency and rate modulation by the chinchilla.

Thresholds for detection of frequency modulation were obtained from three chinchillas at seven frequencies between 320 Hz and 12.75 kHz and at three sensation levels (20, 40, 60, dB SL). These were compared with human thresholds at 40 dB SL obtained under the same conditions. Our data show no significant impact of sensation level and confirm Nelson and Kiester 's [J. Acoust. Soc. Am. 64, 114-126 (1978)] report that the chinchilla has much poorer frequency discrimination than man. In an attempt to assess separately the chinchilla's capacity for temporal coding of frequency, thresholds for detection of a change in the modulation rate of amplitude modulated noise were obtained for nine modulation frequencies between 10 and 320 Hz. The chinchillas needed a larger rate change for detection than most humans but the relative difference was less than that found for frequency modulation detection.

Animals↗
PubMedDate not supplied

Effects of awareness and motor involvement on autonomic conditioning in chronic schizophrenics.

Chronic schizophrenics under neuroleptic medication were compared with normals, matched for age and education, in two conditioning experiments. Both experiments employed a differential paradigm with long conditional stimulus--unconditional stimulus (CS-UCS) intervals. Skin resistance (SR) and finger pulse or heart rate (HR) were recorded. In Experiment 1, half of the subjects were trained in categorizing the to-be conditional stimuli. In a further step, half of the subjects were informed about the CS-UCS contingency. The UCS was an electric shock. Information improved discrimination of SR responses only of normals, and discrimination training had no effect at all on autonomic responses. In Experiment 2, only electrodermal responders were included. Each subject was tested in two sessions, using a loud tone as UCS in one, and a reaction time signal in the other. Again, half of the subjects wee informed about the contingency. Information improved discrimination of SR responses of both diagnostic groups. Decelerations of HR following CS onset showed informed schizophrenics to discriminate better with the loud tone UCS than with the reaction time signal. General autonomic responsivity seems to determine not only discriminative conditioning of schizophrenic patients but also the reports of awareness and the effects of manipulations of awareness. However, when subjects are matched for electrodermal responsivity and are equivalent in terms of SR response conditioning, patients react to information about the contingency with enhanced HR deceleration to the CSs, possibly reflecting a heightened sensitivity of the cardiovascular system.

Adult↗
PubMed1999

Effects of discrimination difficulty on cognitive event-related brain potentials in patients with cochlear implants.

Cognitive event-related brain potentials (ERPs) recorded during a 2-tone discrimination (oddball) task were examined in 8 patients with cochlear implants. The aim of this study is to investigate the effects of discrimination difficulty formed by 4 conditions of stimulus contrast: the target stimuli were set at 2000, 1500, 1200, or 1100 Hz, and nontarget stimuli were set at 1000 Hz throughout. The averaged ERPs recorded after the target stimuli revealed N100, P200, N200, and P300 peaks, whereas those after the nontarget stimuli showed only N100 and P200 peaks. The peak latencies of the ERP components of early information processings (N100 and P200) were not significantly increased among the 4 conditions. In contrast, the latencies of late cognitive components (N2b and P300, whose peak latencies were longer than 250 msec) and reaction times were significantly increased as target discriminability decreased. In conclusion, early information processings were not delayed by the discrimination difficulty, but cognitive processings were delayed in patients with cochlear implants. Because the N2b amplitude, which is considered to be associated with controlled processings, was much larger than that previously reported from subjects with normal hearing, it is suggested that patients with cochlear implants make a considerable effort to process their poor auditory information.

Adult↗
PubMed1987

Frequency discrimination in the mammalian cochlea: theory versus experiment.

A three-dimensional hydroelastic model for the motion in the cochlea is analyzed for the case of a pure-tone forcing. It is shown to agree well with experiment, including moderate intensity tuning curves and the frequency map, for a variety of mammals. In doing this, the parameters that are needed for each animal are geometric; thus the theory is easy to apply. The analysis also indicates that the fluid viscosity is the dominant dissipation mechanism, at least for moderate to high frequencies.

Animals↗
PubMed2006

Neural rate and timing cues for detection and discrimination of amplitude-modulated tones in the awake rabbit inferior colliculus.

Neural responses to amplitude-modulated (AM) tones in the unanesthetized rabbit inferior colliculus (IC) were studied in an effort to establish explicit relationships between physiological and psychophysical measures of temporal envelope processing. Specifically, responses to variations in modulation depth (m) at the cell's best modulation frequency, with and without modulation maskers, were quantified in terms of average rate and synchronization to the envelope over the entire perceptual dynamic range of depths. Statistically significant variations in the metrics were used to define neural AM detection and discrimination thresholds. Synchrony emerged at modulation depths comparable with psychophysical AM detection sensitivities in some neurons, whereas the lowest rate-based neural thresholds could not account for psychoacoustical thresholds. The majority of rate thresholds (85%) were -10 dB or higher (in 20 log m), and 16% of the population exhibited no systematic dependence of average rate on m. Neural thresholds for AM detection did not decrease systematically at higher SPLs (as observed psychophysically): thresholds remained constant or increased with level for most cells tested at multiple sound-pressure levels (SPLs). At depths higher than the rate-based detection threshold, some rate modulation-depth functions were sufficiently steep with respect to the across-trial variability of the rate to predict depth discrimination thresholds as low as 1 dB (comparable with the psychophysics). Synchrony, on the other hand, did not vary systematically with m in many cells at high modulation depths. A simple computational model was extended to reproduce several features of the modulation frequency and depth dependence of both transient and sustained pure-tone responders.

Acoustic Stimulation↗
PubMed1986

P300 and alcohol consumption in normals and individuals at risk for alcoholism. A preliminary report.

Pairs of college student subjects (36 male, 36 female) were matched on age, sex, and personal drinking history. One pair member had a parent who met the DSM III criteria of alcoholism, while the other pair member had no close alcoholic relative. The P300 event-related brain potential (ERP) was obtained from each subject with auditory stimuli in an "oddball" paradigm. Target stimuli occurred randomly on 20% of the trials in a frequency discrimination task, a relatively easy intensity discrimination task, and a more difficult intensity discrimination task. Subjects indicated when the target items occurred by moving their index finger. No significant overall effects were obtained for family history for either P300 latency or amplitude. P300 latency increased and amplitude decreased with increases in the reported amount of alcohol consumption in all subjects only for the difficult intensity task but were statistically significant only for individuals with a negative family history for alcoholism.

Adolescent↗
PubMed2006

Perception of complex sounds in budgerigars (Melopsittacus undulatus) with temporary hearing loss.

Songbirds and parrots deafened as nestlings fail to develop normal vocalizations, while birds deafened as adults show a gradual deterioration in the quality and precision of vocal production. Beyond this, little is known about the effect of hearing loss on the perception of vocalizations. Here, we induced temporary hearing loss in budgerigars with kanamycin and tested several aspects of the hearing, including the perception of complex, species-specific vocalizations. The ability of these birds to discriminate among acoustically distinct vocalizations was not impaired but the ability to make fine-grain discriminations among acoustically similar vocalizations was affected, even weeks after the basilar papilla had been repopulated with new hair cells. Interestingly, these birds were initially unable to recognize previously familiar contact calls in a classification task-suggesting that previously familiar vocalizations sounded unfamiliar with new hair cells. Eventually, in spite of slightly elevated absolute thresholds, the performance of birds on discrimination and perceptual recognition of vocalizations tasks returned to original levels. Thus, even though vocalizations may initially sound different with new hair cells, there are only minimal long-term effects of temporary hearing loss on auditory perception, recognition of species-specific vocalizations, or other aspects of acoustic communication in these birds.

Animals↗
PubMed1995

[Receptive musical aptitude using a binaural frequency discrimination test].

Musical aptitude is the most important precondition for any applicant taking up studies at a music conservatory. Thus, the applicants are tested and assessed very thoroughly by experienced music teachers. To support these subjective results by objective data a procedure was developed allowing to test both the examinee's frequency and octave discrimination capacity in a simple way. In a 1-Hz cycle the frequencies f1 and f2 are directed mutually to the right and left ear, respectively, at a defined sound level. Then the examinee is asked to syntonize e.g. frequency equality f1 = f2 (or f1 = 2 x f2). It can be shown that there is a direct correlation between the amount of deviation from nominal frequency and subjective assessment of musicality.

Adult↗