Heart rate variability during attention phases in young infants.

Heart rate variability during visual attention was studied in infants who were tested cross-sectionally at 14, 20, or 26 weeks of age. They were presented with a recording of a Sesame Street program on a TV screen. After heart rate had decelerated below the prestimulus level and then returned to prestimulus level, a computer-generated pattern replaced the Sesame Street display. Heart rate variability changed throughout attention. The change consisted of a decrease in variability during attention and a return to prestimulus levels approximately five seconds following attention termination. The heart rate and variability responses are consistent with a model of parasympathetic vagal influence on the heart in which vagal firing is increased during sustained attention and is inhibited during attention termination.