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| Differences were seen in the brainstem (colored orange in this picture) Photo Credit: BBC.UK online |
Researchers from Northwestern University say dual language instruction is a form of brain training - a mental "work out" that fine-tunes the mind.
Speaking two languages profoundly affects the brain and changes how the nervous system responds to sound, lab tests revealed.
Experts say the work in Proceedings of the National Academy of Sciences provides "biological" evidence of this (see full title and abstract of paper at the end of this post).
For the study, the team monitored the brain responses of 48 healthy student volunteers - which included 23 who were bilingual - to different sounds.
They used scalp electrodes to trace the pattern of brainwaves.
Under quiet, laboratory conditions, both groups - the bilingual and the English-only-speaking students - responded similarly.
But against a backdrop of noisy chatter, the bilingual group were far superior at processing sounds.
They were better able to tune in to the important information - the speaker's voice - and block out other distracting noises - the background chatter.
'Powerful' benefits
And these differences were visible in the brain. The bilingualists' brainstem responses were heightened.
Prof Nina Kraus, who led the research, said: "The bilingual's enhanced experience with sound results in an auditory system that is highly efficient, flexible and focused in its automatic sound processing, especially in challenging or novel listening conditions."
Co-author Viorica Marian said: "People do crossword puzzles and other activities to keep their minds sharp. But the advantages we've discovered in dual language speakers come automatically simply from knowing and using two languages.
"It seems that the benefits of bilingualism are particularly powerful and broad, and include attention, inhibition and encoding of sound."
Musicians appear to gain a similar benefit when rehearsing, say the researchers.
Past research has also suggested that being bilingual might help ward off dementia in older subjects.
Full title of article: Subcortical encoding of sound is enhanced in bilinguals and relates to executive function advantages
Abstract
Bilingualism profoundly affects the brain, yielding functional and structural changes in cortical regions dedicated to language processing and executive function [Crinion J, et al. (2006) Science 312:1537–1540; Kim KHS, et al. (1997) Nature 388:171–174]. Comparatively, musical training, another type of sensory enrichment, translates to expertise in cognitive processing and refined biological processing of sound in both cortical and subcortical structures. Therefore, we asked whether bilingualism can also promote experience-dependent plasticity in subcortical auditory processing. We found that adolescent bilinguals, listening to the speech syllable [da], encoded the stimulus more robustly than age-matched monolinguals. Specifically, bilinguals showed enhanced encoding of the fundamental frequency, a feature known to underlie pitch perception and grouping of auditory objects. This enhancement was associated with executive function advantages. Thus, through experience-related tuning of attention, the bilingual auditory system becomes highly efficient in automatically processing sound. This study provides biological evidence for system-wide neural plasticity in auditory experts that facilitates a tight coupling of sensory and cognitive functions.
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