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PubMed1989

[Cholinergic innervation of the outer hair cells. Possible significance for loss of discrimination in sensorineural hearing loss].

Cochlear outer hair cells (OHC) are capable of auditory perception. In addition, they influence actively the micromechanics of the cochlea. This concept is based on the observation of motile responses induced by electrical and chemical stimuli. OHC motility is probably controlled by the efferent olivo-cochlear system. By means of two monoclonal antibodies against intra- and extracellular epitopes of ACh-receptors a transmembraneous receptor molecule was visualized in the OHC membrane. Besides morphological studies functional investigations using acetylcholine and its analogues were carried out. We observed contractile responses of OHCs that were reversible and dependent on the applied transmitter concentration. We suggest that the high frequency selectivity and sensitivity of the cochlea is modulated by the efferent innervation and the observed ACh-induced OHC motility.

Animals↗
PubMedDate not supplied

Tone duration discrimination in demented, memory-impaired, and healthy elderly.

In order to assess the diagnostic validity of a new test of tone duration discrimination (TDD), we tested elderly subjects, 32 Alzheimer-type (AD) and 11 vascular-type dementia (VAD) patients, 11 memory-impaired (MI), and 21 healthy controls with a TDD test as well as with 18 standard neuropsychological (NP) tests. The TDD test efficiently discriminated demented patients from MI, and MI from controls. As an index of cognitive impairment, the TDD test was sensitive also in comparison to NP tests. This suggests that processing of auditory duration information is impaired in dementia as well as in MI. Patients suffering from AD and VAD differed in that the VAD but not the AD patients improved their TDD performance when the interstimulus interval was lengthened. This shows that the processing of auditory temporary information involves functions sensitive to dementia diseases as well as to MI. The TDD test could add discriminatory power in diagnosis and differential diagnosis of dementia.

Aged↗
PubMed1991

Effect of time compression and expansion on the discrimination of tonal patterns.

This experiment tested how well human listeners can discriminate between temporal patterns that are compressed or expanded in time. The listener's task was to determine whether two arrhythmic, tonal sequences had the same or different temporal patterns. According to the pattern correlation model [R. D. Sorkin, J. Acoust. Soc. Am. 87, 1695-1701 (1990)], listeners perform this task by computing the correlation between the pattern of time intervals marked by the tones in each sequence. Listener performance dropped when one of the sequences was compressed or expanded in time. In order for the model to describe the observed performance, it was necessary to postulate an internal noise component that was proportional to the magnitude of the difference between the sequence transformations.

Adult↗
PubMed1983

Central auditory processing. V. Ear advantages for acoustic stimuli in baboons.

Four baboons (Papio cynocephalus) were tested using food as reward for ear advantages in the monaural discrimination of pure tones, three-tone musical chords, synthetically constructed consonant-vowels, and vowels. All four animals showed highly significant and reproducible ear advantages for each class of acoustic stimulus with marked individual differences in the direction of their ear asymmetry. The results obtained in these experiments represent the first evidence of ear asymmetries for different classes of acoustic stimuli in a nonhuman species. Further, the ear advantages found in these animals under monaural conditions resemble those obtained with dichotic presentation in human subjects and thus suggest that the baboon may be a valuable model of central auditory processing of various types of acoustic stimuli in man.

Animals↗
PubMed2006

Influence of tone duration and intertone interval on the discrimination of frequency contours in a macaque monkey.

Behavioral studies have shown that non-human primates can categorically discriminate descending from ascending frequency steps in sequences of pure tones. Here we show that the performance of a long-tail macaque remains stable in such a task when the silent interval between the tones of a frequency step is varied between 0 and 1100 ms. Our finding suggests that: (1) some monkeys can keep frequency-specific information in their short-term memory for periods >1s, which can be used to make categorical decisions on the direction of frequency steps, and that (2) their ability to categorize the direction of frequency steps may be more similar to humans than previously assumed.

Acoustic Stimulation↗
PubMed1998

Attentional disruption is enhanced by the threat of pain.

Using a primary task paradigm this study investigated whether attentional disruption to a low-intensity electrocutaneous pain stimulus is enhanced by the threat of intense pain. Healthy volunteers (n = 38) performed a tone discrimination task in the presence of two types of distractors (a low-intensity electrocutaneous stimulus and a control stimulus) which they were instructed to ignore. In some trials, tone probes were presented immediately (250 ms) after distractor onset, further on (750 ms) during the distractor, and immediately (250 ms) after distractor offset. In a threat condition half of the participants were informed that a high-intensity painful stimulus would occur. As predicted, those participants who received the threat instructions, displayed a specific larger disruption of task performance immediately after the onset of the low-intensity pain stimulus in comparison with the control group.

Adolescent↗
PubMed1991

P300 and introverted/extraverted personality types.

The P300 component of the event-related potential elicited with a two-tone auditory discrimination task and two-trial block replication procedure was obtained from 16 introverted and 16 extraverted undergraduate students. P300 demonstrated no overall significant effects for either the personality variable or the block variable. However, P300 amplitude to the target stimuli declined significantly between Block 1 and Block 2 for the extraverted subjects, but did not change across trial blocks for the introverted group. Female subjects tended to have larger P3 amplitudes than male subjects, but this factor did not interact with either the personality variable or the trial block variable. The results suggest that P3 amplitude habituates more rapidly for extraverts than for introverts.

Adult↗
PubMed1982

Hearing in the elephant (Elephas maximus): absolute sensitivity, frequency discrimination, and sound localization.

A young Indian elephant was tested to determine its absolute sensitivity, frequency-discrimination thresholds, and sound-localization thresholds. The elephant was found to have an audibility curve similar to that of other mammals but one that is more sensitive to low frequencies and less sensitive to high frequencies than any other mammalian audiogram including human's. The elephant's sensitivity to frequency differences at low frequencies was found to equal that of humans. Finally, the elephant was found to be very accurate at localizing sounds in the azimuthal plane, with thresholds around 1 degree for broad-band noise. The elephant's ability to localize pure tones suggested that it could use both binaural time- and intensity-difference cues to localize sound.

Animals↗
PubMed1990

Infants' perception of timbre: classification of complex tones by spectral structure.

Infants 7 to 8.5 months of age were tested for their discrimination of timbre or sound quality differences in the context of variable exemplars. They were familiarized with a set of complex tones with specified spectral structure; members of the set varied in fundamental frequency, intensity, or duration. Infants were then tested for their detection of tones that contrasted in spectral structure but were similar in other respects. They successfully differentiated the two spectral structures in the context of these variations, indicating that they can classify tonal stimuli on the basis of timbre. When the stimuli were organized into arbitrary categories, infants were unable to differentiate these categories, indicating that their performance with nonarbitrary categories was not attributable to memorization of the familiarized set.

Female↗
PubMed2006

Frequency and amplitude discrimination along the kinestheticcutaneous continuum in the presence of masking stimuli.

Frequency and amplitude discrimination thresholds along the kinesthetic to cutaneous continuum were evaluated on the left index fingerpad using a multifinger tactual display. Target stimuli were presented either in isolation (no-masker condition) or in the presence of masking stimuli (one- or two-masker conditions). Six reference target signals in the frequency range 2-300 Hz (two each from low-, medium-, and high-frequency regions) and at an amplitude of either 20 or 35 dB sensation levels (SL) were used. In the no-masker condition, the range of frequency Weber fraction was 0.13-0.38 and 0.14-0.28, and the range of amplitude discrimination threshold was 1.82-2.98 dB and 1.65-2.71 dB, at 20 and 35 dB SL, respectively. In the masking conditions, average frequency Weber fractions rose to 0.60 and 0.46, and average amplitude thresholds rose to 3.63 and 3.72 dB, at 20 and 35 dB SL, respectively. In general, thresholds were largest in the two-masker condition and lowest in the no-masker condition. Although the frequency and amplitude thresholds generally increased in the presence of masking stimuli, there was some indication of channel independence for low- and high-frequency target stimuli. The implications of the results for tactual communication of speech are discussed.

Acoustic Stimulation↗
PubMed2002

Auditory frequency discrimination in adult developmental dyslexics.

Developmental dyslexics reportedly discriminate auditory frequency poorly. A recent study found no such deficit. Unlike its predecessors, however, it employed multiple exposures per trial to the standard stimulus. To investigate whether this affects frequency discrimination in dyslexics, a traditional two-interval same-different paradigm (2I_1A_X) and a variant with six A-stimuli per trial (2I_6A_X) were used here. Frequency varied around 500 Hz; interstimulus interval (ISI) ranged between 0 and 1,000 msec. Under 2I_1A_X, dyslexics always had larger just noticeable differences (JNDs) than did controls. Dyslexic and control JNDs were equal at shorter ISIs under 2I_6A_X, but dyslexics became worse than controls at longer ISIs. Signal detection analysis suggests that both sensory variance and trace variance are larger in dyslexics than in controls.

Adult↗
PubMed1999

Decay of cortical pre-attentive sound discrimination in middle-age.

Ageing effects on pre-attentive cortical detection of sound change, as indexed by magnetic mismatch negativity (MMNm), were disclosed with whole-head magnetoencephalography (MEG). Seventy healthy subjects (aged 17-82 years) were presented with a sequence of homogeneous standard tones and occasional deviants of shorter duration. The MMNm elicited by the shorter tones was diminished in amplitude (r = -0.42, p < 0.001) and increased in latency in the hemisphere ipsilateral to the ear stimulated (r = 0.38, p < 0.01), these effects being significant even in middle-aged subjects. The results suggest that pre-attentive comparison of incoming stimuli to a short-lived sensory memory trace in the central auditory system is impaired, and delayed in the ipsilateral hemisphere, already by the middle-age.

Acoustic Stimulation↗
PubMed2006

Mismatch negativity elicited by tones and speech sounds: changed topographical distribution in aphasia.

This study used the event-related brain potential mismatch negativity (MMN) to investigate preconscious discrimination of harmonically rich tones (differing in duration) and consonant-vowel syllables (differing in the initial consonant) in aphasia. Eighteen Norwegian aphasic patients, examined on average 3 months after brain injury, were compared to 11 healthy controls. The main finding was a difference in topographic distribution of the MMN: the aphasia group showed a less lateralized and centralized topographic pattern especially to CV syllables, which is consistent with a reduced temporal lobe processing contribution and an increased right hemisphere activation. No correlations between MMN amplitude and aphasia test results were found.

Acoustic Stimulation↗
PubMed2001

Determination of auditory thresholds in the brushtail possum (Trichosurus vulpecula).

The auditory abilities of the brushtail possum (Trichosurus vulpecula) have been measured by cochlear potential readings, but no behavioural determinations of their auditory abilities have been published. Six experimentally naive possums were trained to perform a two-response conditional discrimination between the presence and absence of an 880-Hz tone (at 80 dB). All six possums readily learned this task. The behavioural threshold for this tone was determined using a modified tracking procedure and found to be similar to that reported using cochlear microphonic potentials. One concern with the current method was the communal nature of the experimental environment so a further threshold determination in a sound-attenuating chamber was conducted. No substantial difference was noted between the results obtained in the two threshold determinations. The success of the current method means that a full, behavioural audiogram for the brushtail possum, which would complement the existing cochlear potential data, is now possible.

Animals↗
PubMed1995

Processing of auditory deviants with changes in one versus two stimulus dimensions.

Auditory event-related potentials (ERPs) in response to 50-ms tones were recorded from the human scalp. A standard stimulus (p = .88) and three different deviants were randomly presented via earphones. There were two one-dimensional deviants (one frequency and one location deviant) and one two-dimensional deviant, with changes in both frequency and location. In one condition, subjects read a book and ignored the auditory stimuli, whereas in another condition they tried to discriminate deviants from standards. In the ignore condition, the two-dimensional deviant elicited an enhanced mismatch negativity (MMN) as compared with the MMNs elicited by the one-dimensional deviants. The temporal and the topographic distributions of the two-dimensional MMNs could be modeled by adding the one-dimensional MMNs. This activity of the MMNs probably results from the independent activity of separate neural populations generating the frequency and the location MMN. In the attend condition, the deviance-related ERP effects were not additive in the N2b and P3 range, implicating that the neural processes involved in the conscious detection of changes in location and frequency were not independent.

Adolescent↗
PubMed1991

Coding of vibrotactile stimulus frequency by Pacinian corpuscle afferents.

Psychophysical and electrophysiological techniques were used to study the encoding and processing of information about the frequency content of vibrational stimuli applied to glabrous skin in humans and cats. Trained human subjects were asked to discriminate changes in stimulus frequency and harmonic content for pairs of mono- and diharmonic sinusoidal vibrations applied to the fingertips. These psychophysical tests supplied data on what information is available to the central nervous system about the frequency components of vibratory stimuli. Electrophysiological recordings from nerves innervating the glabrous skin of the paw in cats during presentation of the same stimuli used in the psychophysical study provided data on how the peripheral nervous system encodes information about the physical parameters of cutaneous vibratory stimuli. The two sets of data indicated that the subjects derived information about the frequency of vibrotactile stimuli from the mean interval between action potentials in afferent nerve fibers activated by the stimulus.

Acoustic Stimulation↗
PubMed1992

P300, probability, and introverted/extroverted personality types.

Extreme introverted and extroverted subject groups (n = 24 each) containing equal numbers of male and females were assessed with the P300 (P3) component of the event-related potential (ERP). A two-tone auditory discrimination task in which the probability of the target stimulus varied systematically in different conditions (.20, .40, .60, .80) was used to elicit the ERPs. The P3 amplitude demonstrated a significant interaction between personality type, probability, and subject gender and was generally smaller for introverts than for extroverts. Female subjects tended to have larger overall P3 components than male subjects. P3 latency was not affected by the personality variable. The results support previous findings for ERP differences between introverts and extroverts and suggest that personality type differentially influences target stimulus probability effects. The findings are discussed in terms of individual differences in cortical activity on P3 amplitude and personality measures.

Adult↗
PubMed1999

A model of frequency coding in the central auditory nervous system.

A phenomenological model for neural coding in the central auditory system is presented. This model is based on average rate-place codes and the hypothesis is that the rate-place code present in the population of low spontaneous rate nerve fibres is adequate to account for frequency discrimination thresholds across the entire audible frequency range. The activity of a population of nerve fibres in response to an input pure tone is calculated and a neural spike train pattern is generated. An optimal central observer estimates the input frequency from the spike train pattern. The model output is the frequency difference limen at the specific input frequency, determined from the estimated input frequency. It is shown that a rate-place code can account for psychoacoustically observed frequency difference limens. The model also supports the hypothesis that a human listener does not make full use of all the information relevant to frequency that is available in auditory nerve spike trains.

Auditory Cortex↗