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

Adult brain regions differ in the intrinsic timescales (INT) over which they integrate information. This spatial organization appears to emerge gradually: infants' brain activity recorded during sleep with functional magnetic resonance imaging (fMRI) shows overall longer INT and a different spatial structure. However, since fMRI is sensitive to hemodynamic confounds and is affected by arousal state, these factors may have accounted for observed age-related differences. Here, we used electroencephalography (EEG) to investigate for the first time how INT develop in infancy in a longitudinal sample from 6 to 16-months-old (exploratory cohort, n = 45; validation cohort, n = 45) and adults (n = 10). Infants were awake and engaged in baseline visual protocol, and adults were recorded under comparable (and distinct) conditions. Infant intrinsic timescales shortened from 6 to 16-months but remained longer than those of adults at all ages. Finally, INT correlated with alpha lagged coherence, a metric of self-predictability and, to lesser extent, with alpha peak frequency, suggesting that alpha oscillatory activity may contribute to the emergence of INT. Identifying the mechanisms underlying longer INT early in infancy-a finding replicated across fMRI and EEG-is a crucial step toward understanding the neural computations that allow infants to extract and learn patterns from their environment.