Hearing in American leaf-nosed bats. III: Artibeus jamaicensis [Hearing Research 184 (2003) 113-122].
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Sensory processing is a crucial underpinning of the development of social cognition, a function which is compromised in variable degree in patients with pervasive developmental disorders (PDD). In this manuscript, we review some of the most recent and relevant contributions, which have looked at auditory sensory processing derangement in PDD. The variability in the clinical characteristics of the samples studied so far, in terms of severity of the associated cognitive deficits and associated limited compliance, underlying aetiology and demographic features makes a univocal interpretation arduous. We hypothesise that, in patients with severe mental deficits, the presence of impaired auditory sensory memory as expressed by the mismatch negativity could be a non-specific indicator of more diffuse cortical deficits rather than causally related to the clinical symptomatology. More consistent findings seem to emerge from studies on less severely impaired patients, in whom increased pitch perception has been interpreted as an indicator of increased local processing, probably as compensatory mechanism for the lack of global processing (central coherence). This latter hypothesis seems extremely attractive and future trials in larger cohorts of patients, possibly standardising the characteristics of the stimuli are a much-needed development. Finally, specificity of the role of the auditory derangement as opposed to other sensory channels needs to be assessed more systematically using multimodal stimuli in the same patient group.
The case of a middle-aged professional musician with a presumed encephalitis is reported. Clinical and radiological evidence suggested a mainly right-sided lesion. He complained of a wide variety of musical symptoms which occurred in a mainly sequential manner: these are described and classified. Their relationship to a predominantly right-sided lesion is discussed.
In recent years multichannel neuroprostheses have been developed which directly stimulate the central auditory pathway. Substantially these have been used in cases of total hearing loss caused by neurofibromatosis type 2 where bilateral damage to the auditory nerve prevents more peripheral stimulation. The electrode carrier of the auditory brainstem implant (ABI) is designed to be placed on the cochlear nucleus complex residing at the lateral brainstem surface. Despite altered anatomy due to tumor growth or preceding surgery, correct electrode placement is essential to maximize the variety of pitch percept elicited during electrical stimulation with the ABI without producing side-effects. In order to assist intraoperative identification of the proximal auditory nerve and cochlear nuclei, the non-toxic fluorescent axonal tracers Fast Blue or Fluorogold were injected into the cochlea of rats and Java monkeys. Four to seven days after tracer application, labeling of the eighth cranial nerve, its entrance into the brainstem and the primary radiation of auditory fibers into the cochlear nucleus could be demonstrated as colored fluorescence on the living brain under appropriate ultraviolet illumination. Additional histological processing revealed groups of retrogradely labeled neuronal cell bodies in both species. Our results suggest that this method could also be used in humans in order to aid surgeons with the proper positioning of the electrode array.
Iterated rippled noise having infinite iterations is generated when a flat-spectrum wideband noise is delayed T ms and the delayed version is added to the undelayed noise through positive feedback. The resulting signal has a rippled spectrum, and the perceived pitch of this iterated rippled noise by human listeners corresponds to a frequency of 1/T. We have previously demonstrated that chinchillas can discriminate the rippled-spectrum noise from the flat-spectrum noise. In the present study, chinchillas discriminated a bandpass filtered rippled-spectrum noise from a bandpass flat-spectrum noise in a psychophysical task. The passbands were set to be one octave wide. Psychometric functions were obtained for 5 chinchillas and performance was measured as d'. The best behavioral performance was obtained when the center frequency of the bandpass filter generally corresponded to the 3rd 5th harmonic peak of the rippled noise (i.e., at 3/T to 5/T), but the precise location of the dominant region varied with the delay of the rippled noise such that the dominance region tended to shift to lower harmonics as 1/T increased. These results indicate that not all spectral regions are weighted equally in the discrimination task. The spectral dominance region found in chinchillas is similar to that described for human pitch perception.
Recent studies have found associations between auditory processing deficits and language disorders such as dyslexia; but whether the former cause the latter, or simply co-occur with them, is still an open question.
The attention band and response ratio hypotheses of Green and Luce (1974) and Luce and Green (1974) are discussed and some difficulties are noted. An alternative hypothesis is put forward. This is based on a Thurstonian model for magnitude estimation in which the presented stimulus intensities are subjected to a logarithmic transformation. Response criteria are then applied to the resulting quantities to select corresponding responses. The setting and maintenance of these response criteria are accounted for by a theory of criterion setting previously developed by the senior author (Treisman & Williams, 1984). A similar model is developed for cross-modality matching, and it is shown that these models can predict the V pattern for the coefficient of variation of response ratios, can predict the inverted V pattern for correlations between successive responses, and can account for some of the difficulties found in the literature.
Rhythm and pitch are the 2 primary dimensions of music. They are interesting psychologically because simple, well-defined units combine to form highly complex and varied patterns. This article brings together the major developments in research on how these dimensions are perceived and remembered, beginning with psychophysical results on time and pitch perception. Progressively larger units are considered, moving from basic psychological categories of temporal and frequency ratios, to pulse and scale, to metrical and tonal hierarchies, to the formation of musical rhythms and melodies, and finally to the cognitive representation of large-scale musical form. Interactions between the dimensions are considered, and major theoretical proposals are described. The article identifies various links between musical structure and perceptual and cognitive processes, suggesting psychological influences on how sounds are patterned in music.
Developmental changes in an unconditioned response to acoustic stimulation were observed in young chickens. Specifically, durations of distress call (peep) suppression were measured after the onsets of tones that differed in intensity and frequency in 384 newly hatched and 4-day-old chicks. Resuppression was also measured after a 6% change in the frequency of these tones, once the animals had habituated to the original tone. The data showed that the suppression varied systematically as a function of age, intensity, and frequency: (a) the duration of suppression increased with increasing stimulus intensity, as expected; (b) responsiveness to high frequencies grew more rapidly over the first 4 days than responsiveness to low frequencies, an effect indicating a developmental gradient across frequencies with age; (c) resuppression to the 6% change in frequency increased in duration with age; and (d) young birds suppressed vocalizations longer to loud tones in the range of their species' maternal assembly call than to other frequency-intensity combinations. These developmental trends indicate rapid changes in "perceived loudness" and "perceptual sharpening" over the first few days of postnatal life.
Postnatal development of absolute auditory thresholds in the kitten was behaviorally measured from birth up to 1 mo of age. Unconditioned reactions to pure tones were observed for kittens up to Day 12, and conditioned responses were used for animals from Day 10 onward. At 1 day after birth, the first noticeable responses were obtained in 4 of 11 kittens at frequencies of .5-2 kHZ. At 2 days of age, 12 of 16 kittens responded. Thresholds remained high (above 100 dB SPL) up to the sixth day, but the range of behaviorally effective frequencies extended from .2 to 6 kHZ. All conditioned response thresholds at Day 10 and most at Day 12 were significantly lower than those measured by unconditioned reactions. From 10 days onward, all threshold curves showed a characteristic sensitivity optimum at 4 kHZ. For frequencies below 1 kHZ, maximum sensitivity was reached at Day 15; for frequencies up to 20 kHZ, at Day 20; and for even higher frequencies, at Day 30. At 1 mo of age, the frequency range is adultlike. The present behavioral results on developing acoustic function in the kitten closely followed structural maturation of the acoustic pathway and demonstrated limitations of the ability for acoustical communication during the first week of life.
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Three experiments were conducted to explore the utility of magnitude estimation of loudness for hearing aid selection. In Experiment 1 the loudness discomfort level (LDL), most comfortable loudness (MCL), and magnitude estimations (MEs) of loudness were obtained from normal-hearing subjects. MCLs fell within a range of loudness that was relatively low on the loudness function. The LDLs were lower than previously published values. Experiment 2 was performed to identify the source of disparity between our LDL data and previously reported results. The effects of instructions are demonstrated and discussed. In Experiment 3 magnitude estimations of loudness were used to determine the loudness of tonal stimuli selected to represent 1/3 octave band levels of speech. Over the 500-4000 Hz range, the contributions of the various frequency regions to the loudness of speech appears to be nearly constant. Methods are proposed for (a) predicting the frequency-gain response of a hearing aid that restores normal loudness for speech for the hearing-impaired listener and (b) psychophysically evaluating the compression characteristic of a hearing aid.
The loudness of one-third octave bands of noise centered at either 1, 2, or kHz was measured in 10 normal-hearing young adults for sound levels of 50-90 dB SPL. Reaction times (RT) in response to these same stimuli were also measured in the same subjects. A moderate-to-strong correspondence was observed between the slopes for functions depicting the growth of loudness with sound level and comparable slopes for the reaction-time data. The correlation between slopes for the RT-intensity function and the loudness-growth function was comparable in magnitude to the test-retest correlation for the loudness-growth function except at 1 kHz.
Numerous studies have demonstrated that the frequency spectrum of sounds is represented in the neural code of single auditory nerve fibres both spatially and temporally, but few experiments have been designed to test which of these two representations of frequency is used in the discrimination of complex sounds such as speech and music. This paper reviews the roles of place and temporal coding of frequency in the nervous system as a basis for frequency discrimination of complex sounds such as those in speech. Animal studies based on frequency analysis in the cochlea have shown that the place code changes systematically as a function of sound intensity and therefore lacks the robustness required to explain pitch perception (in humans), which is nearly independent of sound intensity. Further indication that the place principle plays a minor role in discrimination of speech comes from observations that signs of impairment of the spectral analysis in the cochlea in some individuals are not associated with impairments in speech discrimination. The importance of temporal coding is supported by the observation that injuries to the auditory nerve, assumed to impair temporal coherence of the discharges of auditory nerve fibres, are associated with grave impairments in speech discrimination. These observations indicate that temporal coding of sounds is more important for discrimination of speech than place coding. The implications of these findings for the design of prostheses such as cochlear implants are discussed.
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The existence of an ontogenetic shift of tonotopic organization throughout the auditory pathway concomitant with cochlea maturation is a matter of controversy. Using the 2-deoxyglucose method we demonstrate here for the first time the shift phenomenon in an auditory forebrain structure, field L, the auditory cortex analogue of the chick. During the first postnatal month isofrequency contours move to positions where, in younger chicks, lower frequencies (up to half an octave) are represented. This developmentally changing place code of sound frequencies at the forebrain level is similar to the one previously reported for brain stem auditory nuclei. It raises the question of constancy of frequency-related pitch perception during development and may be a complication of early auditory learning and memory.
Cerebral blood flow (CBF) was measured with PET during rudimentary singing of a single pitch and vowel, contrasted to passive listening to complex tones. CBF increases in cortical areas related to motor control were seen in the supplementary motor area, anterior cingulate cortex, precentral gyri, anterior insula (and the adjacent inner face of the precentral operculum) and cerebellum, replicating most previously seen during speech. Increases in auditory cortex were seen within right Heschl's gyrus, and in the posterior superior temporal plane (and the immediately overlying parietal cortex). Since cortex near right Heschl's has been linked to complex pitch perception, its asymmetric activation here may be related to analyzing the fundamental frequency of one's own voice for feedback-guided modulation.