Xie, W., & Richards, J.E. (2017). The Relation between Infant Sustained Attention and EEG Oscillations: An EEG Power Spectrum and Cortical Source Analysis Study.(pdf )
Introduction: Infant sustained attention is characterized by a deceleration in heart rate (HR) and an increase in brain arousal (Richards, 2008). Increased brain arousal facilitates visual perception and memory encoding (Colombo, 2001). Infant EEG studies have reported alpha suppression/desynchronization in frontal electrodes during memory encoding (Bell, 2002) and in central electrodes (Mu rhythm) during action perception (Marshall et al., 2011). Infant theta synchronization was found in frontal channels during anticipatory attention (Orekhova et al., 1999). Alpha desynchronization is a robust electrical index of brain arousal in adulthood (Sadaghiani et al., 2010). Adult alpha activity has been correlated to activity in the default mode network (DMN; Knyzazev et al., 2011). The DMN shows deactivation when brain alertness increases (Mantini et al., 2007). The current study examined the potential relation between infant sustained attention (brain alertness) and alpha and theta activities using EEG and cortical source analysis.
Method: Fifty-nine infants were tested at 6 (N=15), 8 (N=17), 10 (N=14), and 12 (N=13) months of age. Participants watched Sesame Street videos that elicited different attention phases (Richards, 2010). Three attention phases were defined based on HR changes during infants’ looking. They were stimulus orienting (before HR deceleration), sustained attention (HR deceleration), and attention termination (HR acceleration). Fast Fourier Transform was applied on EEG segments (1s) and power spectrum was calculated for theta (2 – 5 Hz) and alpha (6 – 9 Hz) bands. Cortical source analysis was conducted with realistic infant MRI models and current density reconstruction (CDR) technique.
Results: Theta band: Infants at 8, 10, and 12 months showed greater theta power during sustained attention than attention termination and stimulus orienting in the frontal-pole (FP1, FP2) and occipital (O1, O2) electrodes. Cortical source analysis showed greater CDR amplitude for sustained attention in the inferior and middle temporal gyri and the orbitofrontal gyrus. Alpha band: Infants at 10 and 12 months showed lower alpha power during sustained attention in the frontal (F3, F4), central (C3, C4), and parietal (P3, P4) electrodes. Cortical source analysis showed the alpha activity was widely spread in the brain with high CDR amplitude in the occipital lobe. However, difference between attention phases (alpha suppression) was found in the posterior cingulate cortex, precuneus, and pre- and post-central gyri.
Discussion: The current study demonstrates a link between infant sustained attention and EEG oscillatory activities. The finding of alpha desynchronization during sustained attention is consistent with the alpha desynchronization found during tonic alertness in adulthood. Two cortical sources of this effect, the posterior cingulate cortex and precuneus, are major components of the adult DMN. These findings support the idea that infant sustained attention is accompanied by an increase in brain arousal. The finding of alpha suppression in the precentral gyrus suggests distinct infant Mu activity might occur during sustained attention because infants were watching videos with characters dancing. Infant theta synchronization during sustained attention is comparable to the report of theta synchronization during anticipatory attention. Theta synchronization in the orbitofrontal gyrus may reflect the activation of the anterior attention system subserving executive control.