The neural processing of sound in infants

Abstract

Early auditory abilities play an important role in infants’ ability to acquire language, appreciate music, and navigate the complex acoustic environments around them. However, the neural mechanisms that support infant sound processing are not well understood. This study used magnetoencephalography (MEG) with recent advancements in movement compensation to obtain functional measures of auditory processing in awake infants. MEG responses were recorded longitudinally at 3, 6, and 11 months of age to an English bi-syllabic word and an amplitude-modulated complex tone as a non-speech but spectro-temporally complex control stimulus. MEG recordings were made with an Elekta Neuromag® whole-head 306-channel MEG system. The neural generators of the MEG signals were determined using an equivalent current dipole (ECD) model. High quality MEG data with good signal-to-noise ratios were recorded in infants as young as 3 months of age in both conditions. ECD field maps showed focal sources in the brain confirming the ECD model is a robust source localization approach that can fit auditory neural sources in infants. Our results show that dipole modeling of MEG signals in combination with advanced movement compensation offers a temporally precise method of investigating how the cortical processing of sound changes across the first year of life.