Perception of the pitch of unresolved harmonics by 3- and 7-month-old human infants

Pitch perception in school-aged children: Pure tones, resolved and unresolved harmonics

Pitch perception affects children's ability to perceive speech, appreciate music, and learn in noisy environments, such as their classrooms. Here, we investigated pitch perception for pure tones as well as resolved and unresolved complex tones with a fundamental frequency of 400 Hz in 8- to 11-year-old children and adults. Pitch perception in children was better for resolved relative to unresolved complex tones, consistent with adults. The younger 8- to 9-year-old children had elevated thresholds across all conditions, while the 10- to 11-year-old children had comparable thresholds to adults.

The Maturation of the Acoustic Change Complex in Response to Iterated Ripple Noise in 'Normal'-Hearing Infants, Toddlers, and Adults

BACKGROUND

Infants and toddlers are still being evaluated for their hearing sensitivity but not their auditory-processing skills. Iterated rippled noise (IRN) stimuli require the auditory system to utilize the temporal periodicity and autocorrelate the iterations to perceive pitch.

PURPOSE

This study investigated the acoustic change complex (ACC) elicited by IRN in "normal"-hearing infants, toddlers, and adults to determine the maturation of cortical processing of IRN stimuli.

DESIGN

Cortical responses to filtered white noise (onset) concatenated with IRN stimuli (d = 10 milliseconds, gain = 0.7 dB: 4-32 iterations) were recorded in quiet, alert participants.

STUDY SAMPLE

Participants included 25 infants (2.5-15 months), 27 toddlers (22-59 months), and 8 adults (19-25 years) with "normal" hearing sensitivity.

DATA COLLECTION AND ANALYSIS

Cortical auditory-evoked responses were recorded for each participant, including the onset response to the noise and an ACC to the transition from noise to IRN. Group differences were assessed using repeated-measures analyses of variance.

RESULTS

Most infants had a replicable onset (P) response, while only about half had a measurable ACC (P_ACC) response to the high-saliency IRN condition. Most toddlers had onset responses and showed a P-N_ACC response to the IRN16 and IRN32 conditions. Most of the toddler group had responses present to the onset and showed a P-N_ACC response to all IRN conditions. Toddlers and adults showed similar P-N_ACC amplitudes; however, adults showed an increase in N1_ACC amplitude with increase in IRN iterations (i.e., increased salience).

CONCLUSION

While cortical responses to the percept of sound as determined by the onset response (P) to a stimulus are present in most infants, ACC responses to IRN stimuli are not mature in infancy. Most toddlers as young as 22 months, however, exhibited ACC responses to the IRN stimuli even when the pitch saliency was low (e.g., IRN4). The findings of the current study have implications for future research when investigating maturational effects on ACC and the optimal choice of stimuli.

The development of auditory temporal processing during the first year of life

Objectives

The processing of auditory temporal information is important for the extraction of voice pitch, linguistic information, as well as the overall temporal structure of speech. However, many aspects of its early development remain poorly understood. This paper reviews the development of auditory temporal processing during the first year of life when infants are acquiring their native language.

Methods

First, potential mechanisms of neural immaturity are discussed in the context of neurophysiological studies. Next, what is known about infant auditory capabilities is considered with a focus on psychophysical studies involving non-speech stimuli to investigate the perception of temporal fine structure and envelope cues. This is followed by a review of studies involving speech stimuli, including those that present vocoded signals as a method of degrading the spectro-temporal information available to infant listeners.

Results/Conclusion

This review suggests that temporal resolution may be well developed in the first postnatal months, but that the ability to use and process the temporal information in an efficient way along the entire auditory pathway is longer to develop. Those findings have crucial implications for the development of language abilities, especially for infants with hearing impairment who are using cochlear implants.

Infant Pitch and Timbre Discrimination in the Presence of Variation in the Other Dimension

Adult listeners perceive pitch with fine precision, with many adults capable of discriminating less than a 1 % change in fundamental frequency (F0). Although there is variability across individuals, this precise pitch perception is an ability ascribed to cortical functions that are also important for speech and music perception. Infants display neural immaturity in the auditory cortex, suggesting that pitch discrimination may improve throughout infancy. In two experiments, we tested the limits of F0 (pitch) and spectral centroid (timbre) perception in 66 infants and 31 adults. Contrary to expectations, we found that infants at both 3 and 7 months were able to reliably detect small changes in F0 in the presence of random variations in spectral content, and vice versa, to the extent that their performance matched that of adults with musical training and exceeded that of adults without musical training. The results indicate high fidelity of F0 and spectral-envelope coding in infants, implying that fully mature cortical processing is not necessary for accurate discrimination of these features. The surprising difference in performance between infants and musically untrained adults may reflect a developmental trajectory for learning natural statistical covariations between pitch and timbre that improves coding efficiency but results in degraded performance in adults without musical training when expectations for such covariations are violated.

Developmental Effects in Children's Ability to Benefit From F0 Differences Between Target and Masker Speech

OBJECTIVES

The objectives of this study were to (1) evaluate the extent to which school-age children benefit from fundamental frequency (F0) differences between target words and competing two-talker speech, and (2) assess whether this benefit changes with age. It was predicted that while children would be more susceptible to speech-in-speech masking compared to adults, they would benefit from differences in F0 between target and masker speech. A second experiment was conducted to evaluate the relationship between frequency discrimination thresholds and the ability to benefit from target/masker differences in F0.

DESIGN

Listeners were children (5 to 15 years) and adults (20 to 36 years) with normal hearing. In the first experiment, speech reception thresholds (SRTs) for disyllabic words were measured in a continuous, 60-dB SPL two-talker speech masker. The same male talker produced both the target and masker speech (average F0 = 120 Hz). The level of the target words was adaptively varied to estimate the level associated with 71% correct identification. The procedure was a four-alternative forced-choice with a picture-pointing response. Target words either had the same mean F0 as the masker or it was shifted up by 3, 6, or 9 semitones. To determine the benefit of target/masker F0 separation on word recognition, masking release was computed by subtracting thresholds in each shifted-F0 condition from the threshold in the unshifted-F0 condition. In the second experiment, frequency discrimination thresholds were collected for a subset of listeners to determine whether sensitivity to F0 differences would be predictive of SRTs. The standard was the syllable /ba/ with an F0 of 250 Hz; the target stimuli had a higher F0. Discrimination thresholds were measured using a three-alternative, three-interval forced choice procedure.

RESULTS

Younger children (5 to 12 years) had significantly poorer SRTs than older children (13 to 15 years) and adults in the unshifted-F0 condition. The benefit of F0 separations generally increased with increasing child age and magnitude of target/masker F0 separation. For 5- to 7-year-olds, there was a small benefit of F0 separation in the 9-semitone condition only. For 8- to 12-year-olds, there was a benefit from both 6- and 9-semitone separations, but to a lesser degree than what was observed for older children (13 to 15 years) and adults, who showed a substantial benefit in the 6- and 9-semitone conditions. Examination of individual data found that children younger than 7 years of age did not benefit from any of the F0 separations tested. Results for the frequency discrimination task indicated that, while there was a trend for improved thresholds with increasing age, these thresholds were not predictive of the ability to use F0 differences in the speech-in-speech recognition task after controlling for age.

CONCLUSIONS

The overall pattern of results suggests that children's ability to benefit from F0 differences in speech-in-speech recognition follows a prolonged developmental trajectory. Younger children are less able to capitalize on differences in F0 between target and masker speech. The extent to which individual children benefitted from target/masker F0 differences was not associated with their frequency discrimination thresholds.

Impairment of the Missing Fundamental Phenomenon in Individuals with Alzheimer’s Disease: A Neuropsychological and Voxel-Based Morphometric Study

Background/Aims

The missing fundamental phenomenon (MFP) is a universal pitch perception illusion that occurs in animals and humans. In this study, we aimed to determine whether the MFP is impaired in patients with Alzheimer's disease (AD) using an auditory pitch perception experiment. We further examined anatomical correlates of the MFP in patients with AD by measuring gray matter volume (GMV) on magnetic resonance images via voxel-based morphometric analysis.

Methods

We prospectively enrolled 29 patients with AD and 20 healthy older adults. Auditory stimuli included 12 melodies of Japanese nursery songs that were expected to be familiar to participants. We constructed the melodies using pure and missing fundamental tones (MFTs).

Results

Patients with AD exhibited significantly poorer performance on the MFT task than healthy controls. MFT scores were positively correlated with GMV in the bilateral insula and temporal poles, left inferior frontal gyrus, right entorhinal cortex, and right cerebellum.

Conclusions

These results suggest that impairments in the MFP represent a manifestation of the degeneration of auditory-related brain regions in AD. Further studies are required to more fully elucidate the neural mechanisms underlying auditory impairments in patients with AD and related dementia disorders.

Infant pitch perception: Missing fundamental melody discrimination

Although recent results show that 3-month-olds can discriminate complex tones by their missing fundamental, it is arguable whether they are discriminating on the basis of a perceived pitch. A defining characteristic of pitch is that it carries melodic information. This study investigated whether 3-month-olds, 7-month-olds, and adults can detect a change in a melody composed of missing fundamental complexes. Participants heard a seven-note melody and learned to respond to a change that violated the melodic contour. To ensure that participants were responding on the basis of pitch, the notes in the melody had missing fundamentals and varied in spectral content on each presentation. In experiment I, all melodies had the same absolute pitch, while in experiment II, the melodies were randomly transposed into one of three different keys on each presentation. Almost all participants learned to ignore the spectral changes and respond to the changed note of the melody in both experiments, strengthening the argument that complex tones elicit a sense of musical pitch in infants. These results provide evidence that complex pitch perception is functional by 3 months of age.