Non-negative matrix factorization improves the efficiency of recording frequency-following responses in normal-hearing adults and neonates.

OBJECTIVE: One challenge in extracting the scalp-recorded frequency-following response (FFR) is related to its inherently small amplitude, which means that the response cannot be identified with confidence when only a relatively small number of recording sweeps are included in the averaging procedure. DESIGN: This study examined how the non-negative matrix factorisation (NMF) algorithm with a source separation constraint could be applied to improve the efficiency of FFR recordings. Conventional FFRs elicited by an English vowel/i/with a rising frequency contour were collected. Study sample: Fifteen normal-hearing adults and 15 normal-hearing neonates were recruited. RESULTS: The improvements of FFR recordings, defined as the correlation coefficient and root-mean-square differences across a sweep series of amplitude spectrograms before and after the application of the source separation NMF (SSNMF) algorithm, were characterised through an exponential curve fitting model. Statistical analysis of variance indicated that the SSNMF algorithm was able to enhance the FFRs recorded in both groups of participants. CONCLUSIONS: Such improvements enabled FFR extractions in a relatively small number of recording sweeps, and opened a new window to better understand how speech sounds are processed in the human brain.

Exponential Modeling of Frequency-Following Responses in American Neonates and Adults.

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 r2 = 0.89) and adults (mean r2 = 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.

Cross-linguistic comparison of frequency-following responses to voice pitch in American and Chinese neonates and adults.

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.

Prevalence and correlates of high body mass index in rural Appalachian children aged 6-11 years.

INTRODUCTION: In rural regions of the United States of America, estimates of pediatric obesity often exceed national averages. This problem may be particularly pronounced in Appalachian regions, where significant health and economic disparities abound. This study presents the findings of a body mass index (BMI) screening program for 6-11 year old children living in a rural Appalachian community. County-wide estimates of high BMI (>or=85th percentile) were obtained to understand the health status and needs of our pediatric community and to compare obesity prevalence rates with national averages. An additional aim was to identify subpopulations of children who may warrant clinical intervention due to demographic and behavioral risks factors of high BMI. METHODS: A school-based BMI screening was conducted of 6-11 year old children in southeastern Ohio. Investigators collected 3 sets of height and weight measurements from approximately 2000 elementary school students between 2006 and 2007. Caregivers for a subset of this population also completed a health behaviors questionnaire. RESULTS: Thirty-eight percent of children had high BMI, with 17% at risk for overweight and 20.9% overweight. Boys were 23% more likely than girls to be overweight (chi(2)(1) = 95% CI = 1.08, 1.40) and 11% more likely to become overweight with each year of age (OR = 1.11, 95% CI = 1.07, 1.15). Overweight children were more likely to view television, eat meals at school, and live with a caregiver who smokes. CONCLUSIONS: Consistent with expectations, prevalence of high BMI in this sample of rural Appalachian children exceeds national averages. Prevalence of overweight varied by age and sex; boys are particularly vulnerable to developing obesity, especially as they age. Preliminary survey data suggest that eating breakfast at home and at school and increased hours of television viewing may be associated with higher BMI, especially in younger boys.