Theta synchronization during sustained anticipatory attention in infants over the second half of the first year of life.

The neurophysiological basis of attention control has been investigated in infants during the second half of the first year of life. The marked improvement of voluntary control of attention and action is known to occur during this age period. EEG was registered in 60 infants aged 8-11 months under three experimental conditions: (1) attention to an object in the visual field (externally controlled attention or the 'baseline'); (2) anticipation of the person in the peek-a-boo game (internally controlled attention); and (3) attention to the 'reappeared' person in the peek-a-boo game ('control' condition). Spectral analysis of the data revealed sharp increase of the EEG theta activity (3.6-6.0 Hz) during internally controlled attention as compared to the 'baseline' and the 'control' conditions. The theta1 (3.6-4.8 Hz) increase was maximal at frontal electrode sites. The reactivity of the frontal theta1 during internally controlled attention differentiated subjects with different ability to maintain this type of attention. The theta2 (5.2-6.0 Hz) reactivity was maximal at right temporal electrode site and did not depend on the ability to maintain anticipatory attention. The data point to different functional significance of theta1 and theta2 rhythms in infants. It was suggested that the frontal theta1 synchronization in infants reflects activity of the anterior attention system subserving executive control of attention. The ability to maintain anticipatory attention increased, whereas the frontal theta1 synchronization decreased during the studied age period. There was the direct relationship between frontal theta1 synchronization and persistence of internally controlled attention in 8-month-olds. On the contrary, at 9 and 10 months, these variables were inversely-related. There was no link between theta1 reactivity and persistence of anticipatory attention in 11-month-olds. It was suggested that the age-dependant dynamic of the relationship between frontal theta1 reactivity and attention behaviour reflects the maturational shift in the functioning of anterior attention system. The shift leads to more economic and more efficient functioning of this system.