|EEG patches on an infant’s head to map prenatal experiences and auditory discrimination.
Picture credit: Veikko Somerpuro, University of Helsinki, Finland
New Delhi, Aug. 26: In a Finnish hospital, scientists have spotted elements that mirror the myth of Abhimanyu, Arjuna’s warrior son in the epic Mahabharat who learnt a key battle trick while still in his mother’s womb.
A study by researchers in Finland has suggested that human foetuses can learn and retain faint memory traces of sounds they hear while in their mothers’ wombs, adding fresh evidence for prenatal influences on the brain.
While several earlier studies on laboratory animals and human foetuses have shown how prenatal exposure to specific sounds can influence foetal brain development, the new research is the first to show that neural memory traces are produced by auditory speech-like stimuli prior to birth. The findings were published today in the US journal Proceedings of the National Academy of Sciences.
“We’ve got a glimpse of how foetal learning actually influences the foetal brain,” Eino Partanen, a research scholar at the University of Helsinki, Finland, and the first author of the study, told The Telegraph.
In Mahabharat, Abhimanyu learns how to enter a strategic battle formation called the chakravyuh while in the womb, hearing his father Arjuna narrate the tactic to his mother.
While the study by Partanen and colleagues does not establish any evidence for detailed learning or recognition of sophisticated sounds or music, it has indicated that prenatal experiences of speech-like auditory stimuli can have a significant effect on auditory discrimination after birth.
Their results have emerged in the backdrop of burgeoning evidence for the influence of prenatal exposure to sounds on the brain’s auditory system gathered by other scientists, including researchers at the All India Institute of Medical Sciences, New Delhi, since the mid-1990s.
The Finnish team tracked 33 women from the 29th week of pregnancy to birth, 17 of these women several times a week listened to a pseudoword “tatata” repeated hundreds of times, occasionally with changes in the sound or the pitch of the middle syllable. The other 16 women were labelled as the control group and did not hear these sounds.
After the birth of the babies, the scientists used a technique called mismatch negativity relying on electroencephalograph analysis and detected what they say are signatures of neural memory traces for the sounds.
Their results have indicated that repeated exposure to sounds during the foetal stage leads to the development of neural memory traces for those sounds. “Thus it appears that hearing a great deal of speech before birth may have positive effects, preparing the neural apparatus for the accurate analysis and discrimination of the fine acoustic features of speech, the scientists wrote in their paper.
“But extreme caution must be taken,” Partanen said. “There is no evidence that additional foetal exposure to any auditory material enhances any aspects of cognitive performance.”
The researchers point out that their results also imply that the foetal brain is malleable to the surrounding sounds and — as select studies over the past decade have indicated — it may also be vulnerable to harmful environmental acoustic effects.
US-based neuroscience researchers Edward Chang and Michael Merzenich had in 2003 shown that even moderate background noise may prevent the normal development of the central auditory system.
Three years ago, Shashi Wadhwa and her colleagues at the AIIMS, New Delhi, showed significant differences in the brain’s auditory zones of chicks exposed to recorded vehicular noise and sitar music during foetal life from 10 days to hatching on the 21st day.
“The recorded vehicular noise appeared to induce excitotoxicity,” Wadhwa said today in an interview. “The number of cells in the auditory complexes were reduced in the chicks exposed to vehicular noise as compared to the chicks exposed to music.”
“This new (Finnish) study is another reminder that the sounds that foetuses hear may influence the development of the brain during foetal life,” said Wadhwa, who had initiated studies on foetal chick embryos in the mid-1990s.