Delta- and theta-band cortical tracking and phase-amplitude coupling to sung speech by infants

Abstract

The amplitude envelope of speech carries crucial low-frequency acoustic information that assists linguistic decoding at multiple time scales. Neurophysiological signals are known to track the amplitude envelope of adult-directed speech (ADS), particularly in the theta-band. Acoustic analysis of infant-directed speech (IDS) has revealed significantly greater modulation energy than ADS in an amplitude-modulation (AM) band centered on [~]2 Hz. Accordingly, cortical tracking of IDS by delta-band neural signals may be key to language acquisition. Speech also contains acoustic information within its higher-frequency bands (beta, gamma). Adult EEG and MEG studies reveal an oscillatory hierarchy, whereby low-frequency (delta, theta) neural phase dynamics temporally organize the amplitude of high-frequency signals (phase amplitude coupling, PAC). Whilst consensus is growing around the role of PAC in the matured adult brain, its role in the development of speech processing is unexplored. Here, we examined the presence and maturation of low-frequency ( View larger version (25K): org.highwire.dtl.DTLVardef@c7c7feorg.highwire.dtl.DTLVardef@1afa39org.highwire.dtl.DTLVardef@121d616org.highwire.dtl.DTLVardef@6e7c7b_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LILongitudinal EEG study in which 4, 7- & 11-month infants listened to nursery rhymes C_LIO_LIWe demonstrate cortical speech tracking via delta & theta neural signals (mTRF) C_LIO_LIPeriodogram (PSD) analysis revealed stimulus related delta & theta PSD peaks C_LIO_LIDelta and theta driven phase amplitude coupling (PAC) was found at all ages C_LIO_LIGamma frequency amplitudes displayed stronger PAC to low frequency phases than beta C_LI