Objective: To examine the auditory perception of maternal utterances by neonates using near-infrared spectroscopy (NIRS).
Methods: Twenty full-term, healthy neonates were included in this 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. The neonates were then exposed to auditory stimuli in the form of infant-directed speech (IDS) or adult-directed speech (ADS), sampled from each of the mothers, through an external auditory speaker.
Results: A 2 (stimulus: IDS and ADS) × 2 (recording site: channel 1 (right side) and channel 2 (left side)) analysis of variance for these relative oxygenated haemoglobin values showed that IDS (Mean = 0.25) increased brain function significantly (F = 3.51) more than ADS (Mean = −0.26).
Conclusions: IDS significantly increased brain function compared with ADS. These results suggest that the emotional tone of maternal utterances could have a role in activating the brains of neonates to attend to the utterances, even while sleeping.
- ADS, adult-directed speech
- F0, fundamental frequency
- IDS, infant-directed speech
- NIRS, near-infrared spectroscopy
- oxy-Hb, oxygenated haemoglobin
- SPL, sound-pressure level
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This work was supported by a Grant-in-Aid for Scientific Research to T Toshima from the Japanese Society for the Promotion of Science (A: 14201012).
Competing interests: None declared.