Interactive, non-speech acoustic experience modulates theta, beta and gamma oscillatory responses to speech at 9-months-of-age
Silvia Ortiz-Mantilla1, Teresa Realpe-Bonilla1, April A Benasich1; 1Center for Molecular and Behavioral Neuroscience, Rutgers University Newark, NJ, USA
To efficiently process language, infants must construct detailed phonemic representations within auditory cortex. This “phonemic mapping”, is accomplished by 12-months-of-age, via the interplay between maturation and experience. Whereas theta oscillations (4-8Hz) resolve syllabic information, high-gamma oscillations (>70Hz) support processing of specific phonemic features and represent a unique neural signature for phonemic mapping. Previously we demonstrated that interactive acoustic experience, using spectrotemporally- modulated non-speech, significantly enhanced processing of key pre-linguistic acoustic cues in 7-month-old infants, which generalized to novel non-speech stimuli. We now explore whether such experience-dependent effects also impact phonemic processing and mapping. 9-month-old, infants who had received active (AEx) or passive (PEx) non-speech acoustic experience between 4- and 6-months-of-age were presented with a consonant-vowel contrast using a passive oddball paradigm and compared to 9-month-old naïve controls (NC). Dense-array EEG/ERP was mapped onto an age-appropriate brain template. Source modeling placed dipoles in both auditory cortices. Temporal-spectral analyses were conducted on the standard stimulus in source space within the 2-90 Hz frequency range. Changes in spectral power were evaluated using TSE (temporal spectral evolution). Significant group differences were found in the theta, beta and gamma ranges. When processing the standard stimulus, AEx generated greater beta and high-gamma power than PEx and NC groups while within the theta range, less power was seen for AEx and PEx than NC. These results on phoneme mapping demonstrate that the experience-dependent effects of non-speech experience persist at 9-months-of-age and appear to confer a significant speech processing advantage, facilitating earlier establishment of phonemic cortical representations.
Topic Area: LANGUAGE: Development & aging