Abstract
Auditory cortical oscillations have been proposed to play an important role in speech perception. It is suggested that the brain may take temporal “samples” of information from the speech stream at different rates, phase resetting ongoing oscillations so that they are aligned with similar frequency bands in the input (“phase locking”). Information from these frequency bands is then bound together for speech perception. To date, there are no explorations of neural phase locking and entrainment to speech input in children. However, it is clear from studies of language acquisition that infants use both visual speech information and auditory speech information in learning. In order to study neural entrainment to speech in typically developing children, we use a rhythmic entrainment paradigm (underlying 2 Hz or delta rate) based on repetition of the syllable “ba,” presented in either the auditory modality alone, the visual modality alone, or as auditory-visual speech (via a “talking head”). To ensure attention to the task, children aged 13 years were asked to press a button as fast as possible when the “ba” stimulus violated the rhythm for each stream type. Rhythmic violation depended on delaying the occurrence of a “ba” in the isochronous stream. Neural entrainment was demonstrated for all stream types, and individual differences in standardized measures of language processing were related to auditory entrainment at the theta rate. Further, there was significant modulation of the preferred phase of auditory entrainment in the theta band when visual speech cues were present, indicating cross-modal phase resetting. The rhythmic entrainment paradigm developed here offers a method for exploring individual differences in oscillatory phase locking during development. In particular, a method for assessing neural entrainment and cross-modal phase resetting would be useful for exploring developmental learning difficulties thought to involve temporal sampling, such as dyslexia.
Highlights
The acquisition of language is a fundamental human achievement of great cognitive importance
We present here the first study of phase locking to speech in typically developing children aged 13 years, assessing phase locking to rhythmic auditory, visual, and auditory-visual (AV) stimulus streams [presentation of the syllable “ba” at a 2-Hz rate]
Our paradigm enabled us to assess whether cross-modal phase modulation of auditory entrainment by visual speech information could be measured in children, by comparing the A and (AV–V) responses
Summary
The acquisition of language is a fundamental human achievement of great cognitive importance. Language acquisition follows a protracted time course, with notable individual differences (Fenson et al, 1994), yet the learning mechanisms underlying speech perception are on-line from birth, providing sensory information about speech that is both auditory and visual (Kuhl, 2004). Once the infant is born and can watch the mother or other carers talk, visual information about speech such as lip movements and cheek/jaw movements supplements this auditory information with perfect temporal congruity (see Lewkowicz and Ghazanfar, 2011, for a recent summary). The central role of temporal AV congruence in learning may suggest a mechanistic role for oscillatory mechanisms in both the auditory and visual modalities in explaining individual differences in learning about speech, as well as a role for cross-modal phase resetting
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
