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Background: The scalp-recorded frequency-following response (FFR) has been widely accepted in assessing the brain's processing of speech stimuli for people who speak tonal and nontonal languages. Characteristics of scalp-recorded FFRs with increasing number of sweeps have been delineated through the use of an exponential curve-fitting model in Chinese adults; however, characteristics of speech processing for people who speak a nontonal language remain unclear., Purpose: This study had two specific aims. The first was to examine the characteristics of speech processing in neonates and adults who speak a nontonal language, to evaluate the goodness of fit of an exponential model on neonatal and adult FFRs, and to determine the differences, if any, between the two groups of participants. The second aim was to assess effective recording parameters for American neonates and adults., Research Design: This investigation employed a prospective between-subject study design., Study Sample: A total of 12 American neonates (1-3 days old) and 12 American adults (24.1 ± 2.5 yr old) were recruited. Each neonate passed an automated hearing screening at birth and all adult participants had normal hearing and were native English speakers., Data Collection and Analysis: The English vowel /i/ with a rising pitch contour (117-166 Hz) was used to elicit the FFR. A total of 8,000 accepted sweeps were recorded from each participant. Three objective indices (Frequency Error, Tracking Accuracy, and Pitch Strength) were computed to estimate the frequency-tracking acuity and neural phase-locking magnitude when progressively more sweeps were included in the averaged waveform. For each objective index, the FFR trends were fit to an exponential curve-fitting model that included estimates of asymptotic amplitude, noise amplitude, and a time constant., Results: Significant differences were observed between groups for Frequency Error, Tracking Accuracy, and Pitch Strength of the FFR trends. The adult participants had significantly smaller Frequency Error (p < 0.001), better Tracking Accuracy (p = 0.001), and larger Pitch Strength (p = 0.003) values than the neonate participants. The adult participants also demonstrated a faster rate of improvement (i.e., a smaller time constant) in all three objective indices compared to the neonate participants. The smaller time constants observed in adults indicate that a larger number of sweeps will be needed to adequately assess the FFR for neonates. Furthermore, the exponential curve-fitting model provided a good fit to the FFR trends with increasing number of sweeps for American neonates (mean r 2 = 0.89) and adults (mean r 2 = 0.96)., Conclusions: Significant differences were noted between the neonatal and adult participants for Frequency Error, Tracking Accuracy, and Pitch Strength. These differences have important clinical implications in determining when to stop a recording and the number of sweeps needed to adequately assess the frequency-encoding acuity and neural phase-locking magnitude in neonates and adults. These findings lay an important foundation for establishing a normative database for American neonates and adults, and may prove to be useful in the development of diagnostic and therapeutic paradigms for neonates and adults who speak a nontonal language., (American Academy of Audiology)

Voice pitch carries important information for speech understanding. This study examines the neural representation of voice pitch at the subcortical level, as reflected by the scalp-recorded frequency-following responses from ten American and ten Chinese newborns. By utilizing a set of four distinctive Mandarin pitch contours that mimic the English vowel /yi/, the results indicate that the rising and dipping pitch contours produce significantly better tracking accuracy and larger response amplitudes than the falling pitch contour. This finding suggests a hierarchy of potential stimuli when testing neonates who are born in a tonal or non-tonal linguistic environment.

This study investigated the development of subcortical pitch processing, as reflected by the scalp-recorded frequency-following response, during early infancy. Thirteen Chinese infants who were born and raised in Mandarin-speaking households were recruited to partake in this study. Through a prospective-longitudinal study design, infants were tested twice: at 1-3 days after birth and at three months of age. A set of four contrastive Mandarin pitch contours were used to elicit frequency-following responses. Frequency Error and Pitch Strength were derived to represent the accuracy and magnitude of the elicited responses. Paired-samples t tests were conducted and demonstrated a significant decrease in Frequency Error and a significant increase in Pitch Strength at three months of age compared to 1-3 days after birth. Results indicated the developmental trajectory of subcortical pitch processing during the first three months of life., (© The Author(s) 2016.)

Objective: Previous research has shown the usefulness of utilizing auditory chimeras in assessing a listener's perception of the envelope and fine structure for an acoustic stimulus. However, research comparing and contrasting behavioral and electrophysiological responses to this stimulus type is scarce., Design: Two sets of chimeric stimuli were constructed by interchanging the envelopes and fine-structures of the rising/yi(2)/and falling/yi(4)/Mandarin pitch contours that were filtered through 1, 2, 4, 8, 16, 32, and 64 frequency banks. Behavioral pitch-perception tasks were administered through a two-alternative, forced-choice paradigm. Electrophysiological responses were measured through scalp-recorded frequency-following responses (FFRs) to the lexical-tone chimeras., Study Sample: Twenty American and twenty Chinese adults were recruited., Results: A two-way analysis of variance showed significance (p < 0.05) within and across the filter bank and language background factors for the behavioral measurements, while the frequency-following response demonstrated a significance only across the filter banks., Conclusions: Perceptual importance of envelope cues increases starting from 16 filter banks, while the FFR accuracy and magnitude decreases with increasing number of filter banks. These results can be useful in assessing experience-dependent neuroplasticity and in designing speech processing strategies for cochlear-implant users who speak tonal or non-tonal languages around the globe.

Although scalp-recorded frequency-following response (FFR) to voice pitch has shown great potential to examine pitch processing mechanisms in human participants and animals, few reports have addressed the test-retest reliability of such a response in an animal model. The purpose of this study was to investigate the feasibility and reliability of recording such a response in an animal model and to evaluate the extent to which the response could be separated from background noise. A Chinese monosyllable with a rising pitch was used to elicit the FFR to voice pitch in four guinea pigs. Four objective measures (Root-Mean-Square, Amplitude, Tracking Accuracy, Frequency Error, and Slope Error) were computed from recorded brain waves and were used to examine the phase-locking magnitude and test-retest reliability of the response. Results demonstrated that the animal model produced FFR trends that were repeatable, reliable, and significantly different from responses to the background noise.

To date, observations of the scalp-recorded frequency-following response (FFR) to voice pitch have depended on subjective interpretation of the experimenter. The purpose of this study was to develop and evaluate an automated procedure for detecting the presence of a response. Twenty American (9 boys, 1-3 days) and 20 Chinese (10 boys, 1-3 days) neonates were recruited. A Chinese monosyllable that mimicked the English vowel /i/ with a rising pitch (117-166 Hz) was used as the stimulus. Three objective indices (Frequency Error, Tracking Accuracy, and Pitch Strength) were computed from the recorded brain waves and the test results were compared with human judgments to calculate the sensitivity and specificity values. Results demonstrated that the automated procedure produced sensitivity values between 53-90% and specificity values between 80-100%, and could be used to assess the presence of an FFR for neonates who were born in a tonal or non-tonal language environment.

Objectives: Cross-language studies, as reflected by the scalp-recorded frequency-following response (FFR) to voice pitch, have shown the influence of dominant linguistic environments on the encoding of voice pitch at the brainstem level in normal-hearing adults. Research questions that remained unanswered included the characteristics of the FFR to voice pitch in neonates during their immediate postnatal period and the relative contributions of the biological capacities present at birth versus the influence of the listener's postnatal linguistic experience. The purpose of this study was to investigate the characteristics of FFR to voice pitch in neonates during their first few days of life and to examine the relative contributions of the "biological capacity" versus "linguistic experience" influences on pitch processing in the human brainstem., Design: Twelve American neonates (five males, 1-3 days old) and 12 Chinese neonates (seven males, 1-3 days old) were recruited to examine the characteristics of the FFRs during their immediate postnatal days of life. Twelve American adults (three males; age: mean ± SD = 24.6 ± 3.0 yr) and 12 Chinese adults (six males; age: mean ± SD = 25.3 ± 2.6 yr) were also recruited to determine the relative contributions of biological and linguistic influences. A Chinese monosyllable that mimics the English vowel /i/ with a rising pitch (117-166 Hz) was used to elicit the FFR to voice pitch in all participants., Results: Two-way analysis of variance (i.e., the language [English versus Chinese] and age [neonate versus adult] factors) showed a significant difference in Pitch Strength for language (p = 0.035, F = 4.716). A post hoc Tukey-Kramer analysis further demonstrated that Chinese adults had significantly larger Pitch Strength values than Chinese neonates (p = 0.024). This finding, coupled with the fact that American neonates and American adults had comparable Pitch Strength values, supported the linguistic experience model. On the other hand, Pitch Strength obtained from the American neonates, American adults, and Chinese neonates were not significantly different from each other, supporting the biological capacity model., Conclusions: This study demonstrated an early maturation of voice-pitch processing in neonates starting from 1 to 3 days after birth and a significant effect of linguistic experience on the neural processing of voice pitch at the brainstem level. These findings provide a significant conceptual advancement and a basis for further examination of developmental maturation of subcortical representation of speech features, such as pitch, timing, and harmonics. These findings can also be used to help identify neonates at risk for delays in voice-pitch perception and provide new directions for preventive and therapeutic interventions for patients with central auditory processing deficits, hearing loss, and other types of communication disorders.

Objective: Recent studies have shown that the frequency-following response (FFR) to voice pitch can be a useful method to evaluate the signal-processing mechanisms and neural plasticity in the human brainstem. The purpose of this study was to examine the quantitative properties of the FFR trends with an exponential curve-fitting model., Design: FFR trends obtained with increasing number of sweeps (up to 8000 sweeps) at three stimulus intensities (30, 45, and 60 dB nHL) were fit to an exponential model that consisted of estimates of background noise amplitude, asymptotic response amplitude, and a time constant. Five objective indices (Frequency Error, Slope Error, Tracking Accuracy, Pitch Strength and RMS Ratio) were used to represent different perspectives of pitch processing in the human brainstem., Study Sample: Twenty-three native speakers (16 males; age = 24.7 ± 2.1 years) of Mandarin Chinese were recruited., Results: The results demonstrated that the exponential model provided a good fit (r(2) = 0.89 ± 0.10) to the FFR trends with increasing number of sweeps for the five objective indices., Conclusions: The exponential model, combined with the five objective indices, can be used for difficult-to-test patients and may prove to be useful as an assessment and diagnostic method in both clinical and basic research efforts.

When the fundamental frequency (f0) is removed from a complex stimulus, the pitch of the f0 is still perceived by the listener. Through the use of the scalp-recorded frequency-following response, this study examined the relative contributions of thef0 and its harmonics in pitch processing by systematically manipulating the speech stimulus to remove component frequencies. 12 American and 12 Chinese adults were recruited. There were statistically significant effects of pitch strength and frequency error for the experimental-condition factor. There were significantly larger responses to the harmonics-only conditions than those obtained in the f0-only and control conditions. No statistically significant difference was observed between the two groups of participants. These findings indicate that neural responses associated with individual harmonics dominate the pitch processing in the human brainstem, irrespective of whether the listener's native language is nontonal or tonal.

Objective: Voice pitch carries important cues for speech perception in humans. Recent studies have shown the feasibility of recording the frequency-following response (FFR) to voice pitch in normal-hearing listeners. The presence of such a response, however, has been dependent on subjective interpretation of experimenters. The purpose of this study was to develop and test an automated procedure including a control-experimental protocol and response-threshold criteria suitable for extracting FFRs to voice pitch, and compare the results to human judgments., Design: A set of four Mandarin tones (Tone 1 flat; Tone 2 rising; Tone 3 dipping; and Tone 4 falling) were prepared to reflect the four contrastive pitch contours. Two distinctive algorithms, short-term autocorrelation in the time domain and narrow-band spectrogram in the frequency domain, were used to estimate the Frequency Error, Slope Error, Tracking Accuracy, Pitch Strength and Pitch-Noise Ratio of the recordings from individual listeners as well as the power and false-positive rates of each algorithm., Study Sample: Eleven native speakers (five males; age: mean ± SD = 31.4 ± 4.7 years) of Mandarin Chinese were recruited., Results: The results demonstrated that both algorithms were suitable for extracting FFRs and the objective measures showed comparable results to human judgments., Conclusions: The automated procedure used in this study, including the use of the control-experimental protocol and response thresholds used for each of the five objective indices, can be used for difficult-to-test patients and may prove to be useful as an assessment and diagnostic method in both clinical and basic research efforts.