The function of the frontal lobe in neonates for response to a prosodic voice.

We examined how neonates responded at the brain level to an element of acoustic stimulation using near-infrared spectroscopy (NIRS). Twenty full-term, healthy neonates were included in the study. The neonates were tested in their cribs while they slept in a silent room. First, two probe holders were placed on the left and right sides of the forehead over the eyebrows using double-sided adhesive tape. Then the neonates were exposed to the auditory stimuli from an external auditory speaker. The stimuli, readings of the first scene of "Little Red Riding Hood," were made with a digital voice. The stimuli consisted of two conditions: variably pitched speech (variable speech: VS) and monotonous flat-pitched speech (monotonous speech: MS). The analyses focused on changes in O(2)Hb because O(2)Hb is the most sensitive indicator of changes in cerebral blood flow in NIRS measurement. The O(2)Hb level promptly increased at the beginning of the VS condition, and then returned to baseline again, while O(2)Hb did not show any changes during the MS condition. Differences between baseline-stimulation relative values were used to perform a 2 (condition)x2 (recording site)x2 (gender) analysis of variance. The results show that VS (M=0.45, S.D.=1.33) produced a greater increase of oxygenated blood to the frontal area of the brain area than MS (M=-0.19, S.D.=1.28). Neonates' brain activation patterns suggest that they can discriminate differences in the prosodic patterns of utterances.