Maturation of cortical responses to sound in the first year of life

Infants show sophisticated sound discrimination from the time they are born but the neural mechanisms that support infant auditory perception are not well understood. A central question is the discrepancy between the early onset of auditory skills and the protracted and extended maturation of the auditory cortex. To investigate the cortical processing of sound, we have been employing magnetoencephalography (MEG) with recent advancements in movement compensation to obtain functional neural measures of sound processing in awake infants. MEG responses from an Elekta Neuromag 306-channel system were recorded longitudinally at 3 (n = 27), 6 (n = 19), and 11 (n = 14) months to an ecologically salient bi-syllabic word and an amplitude-modulated complex tone pair in typically hearing infants. The neural generators of the MEG signals were determined using an equivalent current dipole (ECD) model. Our preliminary analyses have focused on two measures: cortical responses to acoustic change and the development of hemispheric lateralization to speech. Our preliminary analyses show that high quality MEG data with good signal-to-noise ratios can be obtained by 3 months and dipole modeling of MEG signals in combination with advanced movement compensation offers a temporally precise method of investigating the maturation of auditory cortical networks in infants.