The sensitivity of the dominant rhythm desynchronization to visual stimuli across infancy: a study using longitudinal and cross-sectional data

The peak frequency of the infant dominant EEG rhythm (6-9 Hz) increases from 6 to 9 to 12 months across occipital, frontal, and central regions regardless of stimulus presentation (Elhamiasl et al., 2023). Desynchronization, referring to the attenuation of the dominant rhythm activity in response to visual processing is an additional neurodevelopmental marker of the dominant rhythm. However, the developmental trajectory of desynchronization is not well understood. To address this gap, longitudinal (n=19) and cross-sectional EEG data sets of 6-month-old (n=49), 9-month-old (n=32), and 12-month-old (n=30) infants were collected while infants were completing a sustained attention task in which novel computer-generated objects and female faces were floating down the screen. For the longitudinal analysis, there was significant desynchronization across ages and stimuli. However, in the larger cross-sectional data desynchronization of the dominant rhythm was present in infants as young as 6 months and desynchronization increased marginally from 6 to 9 months of age. For both the longitudinal and cross-sectional data, desynchronization was significantly greater in response to faces compared to objects, suggesting greater allocation of attention to faces throughout the first year of life. The findings, overall, demonstrated that unlike peak frequency, which was not found to be sensitive to condition differences, desynchronization of the dominant rhythm differentiates infant neural responses to faces and objects.