The Influence of Infant Diet on Early Developmental Changes in Processing Human Voice Speech Stimuli: ERP Variations in Breast and Milk Formula-Fed Infants at 3 and 6 Months After Birth

Abstract

The purpose of this investigation was to determine if processing of language stimuli during the first half year of life in breast-fed infants differs from that of formula-fed infants. This question was addressed by examining the brain event-related potentials of healthy infants receiving breast milk (n = 15) or milk-based formula (n = 18) recorded in response to consonant vowel syllables presented in an oddball paradigm. The same infants were studied when they were 3-months and 6-months-old. The two groups were comparable on several measures relating to biological and home environment variables previously reported to influence development, including gestation period, birth weight, mother's IQ, and family socioeconomic status, and did not differ in weight or mental or motor development at the times of the visits. In general, ERP response features previously documented in studies of syllable processing in 3–6-month-old infants were observed in this study, including positive components at ∼ 190 msec (P1), ∼ 370 msec (P2), and ∼ 600 msec (P600), and negative components at ∼ 250 msec (N250), ∼ 450 msec (N450), and a late, negative going slow wave between 655 and 995 msec (LSW). For both groups there were instances where specific components were either poorly defined, e.g., P1 and N250 to the infrequent syllable at 3 months, N450 and P600 to this syllable at both ages, or not present in many infants, e.g., the P600 to the frequent syllable at 6 months. These variations appeared to be related to individual differences in development or paradigm-related features, i.e., ISI and frequency of syllable occurrence.

Developmental variations (changes from 3 to 6 months) common to both feeding groups included latency decreases for P1, decreased P2 amplitude, and increased amplitudes for N250 and LSW components. Within this framework, group differences were detected in areas involving the development of response components, the development of processing capabilities, and syllable discrimination. In all cases, these effects related to components following initial stimulus registration, i.e., to the processing of sound content rather than sound acoustic features. The pattern of these differences suggests advantages for BF infants in the development and processing of language stimuli during the first 6 months of life.