Fascinating new research shows that unborn children can recognize and process varying forms of speech at 29 weeks, even before speech centers appear. The processing is advanced enough, for example, to allow them to differentiate between male and female voices.
Keith Barrington, a neonatologist and clinical researcher and chief of service at Sainte Justine University Health Center in Montreal, writes more about the new study:
The message of this article is that, even at 29 weeks gestation, , the preterm brain reacts differently to different phonemes (ba versus ga) and different voices (masculine versus feminine). That’s cool.
Because at 29 weeks the neurons which will eventually form the centers involved in speech are still not at their final locations. The brain is still very immature at that point, and those parts of the brain that we usually expect to respond to speech have not been properly constituted. Language really is hard-wired into our brains.
Mahmoudzadeh M, Dehaene-Lambertz G, Fournier M, Kongolo G, Goudjil S, Dubois J, et al. Syllabic discrimination in premature human infants prior to complete formation of cortical layers. Proceedings of the National Academy of Sciences. 2013;110(12):4846-51.
If you take those preterm babies when they are adults, they seem to be processing language with different parts of the brain. Although their scores on standardized testing of language skills were the same as controls born at term, the preterm born adults were using pathways in their cerebellum to process language, but not the term born adults. Constable RT, Vohr BR, Scheinost D, Benjamin JR, Fulbright RK, Lacadie C, et al. A left cerebellar pathway mediates language in prematurely-born young adults. NeuroImage. 2013;64(0):371-8.
This seems to me to be new evidence of the plasticity of the brain, which develops differently if you are born very preterm, the average gestation of the subjects was 28 weeks.