Mechanisms, Capabilities and Applications of Infant Neural and Physiological Oscillatory Entrainment

Infants entrain to a wide variety of simple rhythmic stimuli from birth and more complex stimuli during development (section 2.4). However, there is still limited understanding of infant neural and physiological entrainment mechanisms and how these compare with adult entrainment techniques. For example, there is growing evidence of internally generated and driven neural oscillatory entrainment in adults, but similar evidence is lacking in infant populations. There is also limited research that has investigated the effects of rhythm in naturalistic settings, such as the impact of rhythm in speech brain tracking, and disruption of infant rhythms caused by other external rhythmic stimuli.

This thesis assesses sub-second cognitive and physiological entrainment responses to provide new evidence in the above areas. In Chapter 3, neural entrainment data are presented discussing infant and adult entrainment preferences across stimulus frequency, along with spatial and temporal differences. In Chapter 4, neural entrainment to controlled temporally regular vs irregular stimuli and implications for mechanisms of infant and adult entrainment are explored. In Chapter 5, strength of speech-brain tracking to infant directed speech and song rhythms using continuous neural mapping investigated impacts of rhythm in infant directed language. Finally in Chapter 6, interactions between competing rhythmic infant crying and caregiver rocking in a home setting are investigated.

In brief, the results demonstrated for the first time that infant and adult entrainment preferences are different across stimulation frequencies; mechanisms of infant and adult entrainment are not the same; entrainment to infant directed speech vs song were differentiated across frequency bands and age ranges; and dynamic responses to infant crying can disturb infant rhythms to shorten cry length.

Discussion focusses on contribution to our understanding of infant entrainment capabilities and mechanisms, application of infant rhythmic entrainment to language acquisition, and dysregulation of infant rhythms with competing rhythms. Future research directions, methodological considerations and the need for more naturalistic studies are discussed.