Fetal auditory evoked responses to onset of amplitude modulated sounds. A fetal magnetoencephalography (fMEG) study.
Level 4 - case-series / case-control
Single-group cross-sectional physiological cohort study without a control group.
PubMed 29534830 · doi:10.1016/j.heares.2018.03.005
What was done
Researchers measured fetal auditory brain activity using fetal magnetoencephalography (fMEG) in 55 pregnant women between 31 and 40 weeks of gestation. Auditory stimuli consisted of a 500 Hz tone amplitude-modulated at low (2/s, 4/s), middle (8/s), and high (27/s, 42/s, 78/s, 91/s) modulation rates delivered to the maternal abdomen to evaluate how the fetal brain processes sound envelope slopes and onset intensity changes.
What was found
Response latencies of transient event-related responses were significantly shorter for high and middle modulation rates compared to low modulation rates. The highest fetal response detection rates occurred at 2/s (70%), 4/s (57%), and 27/s (86%). A statistically significant maturation effect (decrease in response latency with increasing gestational age) was detected only for the 4/s modulation rate. Specific numerical latency values and confidence intervals were not reported in the abstract.
Why it matters
These findings suggest that before birth, the human fetal auditory system can differentiate sound envelope onset dynamics across distinct temporal integration windows, a fundamental mechanism underpinning speech and language processing.
Limits
The study is observational and cross-sectional rather than longitudinal. The abstract does not provide exact response latency figures, standard deviations, or p-values. No postnatal auditory or language outcomes were tracked.