This 2015 Harvard study found that exposing extremely premature babies to sounds of their mothers enlarged their auditory cortex.
The lead researcher stated:
“Our findings do not prove that the brains of these babies are necessarily better, and we cannot conclude that they will end up with no developmental disabilities.
We don’t know the advantages of having a bigger auditory cortex.”
It’s too bad that studies like this one have to take deprived infants and further deprive them for use as a control group. I suppose it’s possible that the control group members’ development could just be shifted, similar to the Maternal depression and antidepressants epigenetically change infant language development study.
However, given the findings of the Our early experiences are maintained and unconsciously influence us for years, if not indefinitely study, it’s also possible that the last trimester of womb life is a critical period for a child’s auditory cortex. If timely development doesn’t take place within the environment provided by the mother, there may not be another period to fully catch up on growth and learning, even given the effects of neural plasticity.
http://www.pnas.org/content/112/10/3152.full “Mother’s voice and heartbeat sounds elicit auditory plasticity in the human brain before full gestation”