The longitudinal development of intrinsic timescales in infancy and their relation to alpha brain rhythm

Brain regions differ in the intrinsic timescales over which they integrate, shaping the information they encode; and these differences change with development. Here we used EEG to investigate how intrinsic timescales develop from infancy to toddlerhood and how they compare to adults. A recent rs-fMRI study found sleeping neonates had longer timescales than awake adults. However, fMRI is affected by hemodynamics, has limited temporal resolution, and timescales may be affected by sleep. Therefore, EEG was used to measure intrinsic timescales in infants longitudinally from 6 to 16-months-old (exploratory cohort, N=45; validation cohort, N=45) and adults (N=10). Infants were awake and engaged in visual stimulation, and adults were recorded under comparable (vs. different) conditions. Six-month-olds’ timescales were longer than those of adults in comparable conditions, and they shortened from 6 to 16-months-old. Finally, in younger infants, brain timescales correlated to alpha rhythm self-predictability. Longer intrinsic timescales early in infancy, a finding which generalises across fMRI and EEG, might act as an inductive bias favouring the learning of holistic abstract representations. Delineating the mechanisms underlying brain processing timescales in infants is a crucial step towards understanding the neural mechanisms which could allow infants to extract and learn patterns from the environment.