The theta rhythm of the infant EEG and the development of the mechanisms of voluntary control of attention in the 2nd half of the first year of life

The neurophysiological basis of attention control was studied in infants at the second half-year of life, i.e. in the period when the capability for voluntary control over behavior fundamentally improves. EEG was recorded in 60 infants aed 8-11 months in three experimental conditions: 1) attention to an object in the visual field (externally controlled attention, or the baseline state), 2) anticipation of a person in the peek-a-boo game (internally controlled attention), 3) attention to the reappeared person in the peek-a-boo game (control condition). The spectral analysis of the EEG data revealed a sharp increase in the EEG theta (3.6-6.0 Hz) during internally controlled attention as compared to the baseline and control conditions. The theta1 (3.6-4.8 Hz) increase was maximal in the frontal derivations. The reactivity of the frontal theta1 during internally controlled attention discriminated infants with different abilities to maintain this type of attention. The reactivity of the theta2 (5.2-6.0 Hz) was maximal in the right temporal derivation (T6) and did not depend on stability of the anticipatory attention. The findings point to different functional significance of the theta1 and theta2 rhythms in infants. It is suggested that synchronization of the frontal theta1 rhythm in infants reflects the activity of the anterior attention system which realizes the executive attention control. The ability to maintain anticipatory attention increased with age, whereas the frontal theta1 synchronization decreased and totally disappeared at the age of 11 months. At the age of 8 months there was a positive correlation between the frontal theta1 synchronization and behavioral index of stability of the internally controlled attention. On the contrary, this correlation was negative at the age of 9 and 10 months. It is suggested that the age-dependent dynamics of the relationship between the frontal theta1 reactivity and attention reflects a leap in maturation of the anterior attention system resulting in its more economic and efficient functioning.