With the emergence of globalization, the need to learn a second language, or multiple languages, became a necessity. Globalization has led people around the world learning a multitude of languages to be able to effectively communicate with others in different regions of the world. Approximately 33 million people worldwide are bilinguals, ability to fluently speak two languages, with most of the bilinguals being individuals in their young adulthood (ages 16-24), not accounting those who speak more than two languages fluently (Gration, 2022).
Linguists and neuroscientists have produced a multitude of experimental studies looking to identity the cognitive benefits and effects of bilingualism. Their research has suggested that when bilinguals speak their targeted language, both of their languages remain “active” through a complex network of inhibition to restrict their targeted language and minimize possible interference from the other learned language (Tao et al., 2021). During a Stroop test, bilinguals demonstrated greater control when assessing irrelevant information and switching attention to goal-relevant information (Kim, 2019). The emergence of the inhibitory control mechanism found in bilinguals has raised the question if bilinguals have significant cognitive and health benefits. Yet, before examining its cognitive and health benefits, scientists needed to further understand the neurological impact of language acquisition based on language’s critical period and whether it influences the brain’s structure, intricate connectivity, and its neuroplasticity.
Previously, scientists faced grave limitations at determining such relationship between language’s critical periods and brain plasticity due to their experimental models being individuals who had learned language late in childhood and adulthood, whose brain’s maturation period had surpassed (Berken et al., 2017). Neuroimaging on premature infants and even fetuses in utero exhibited distinct recognition to different phonemes, which are a sound unit of language. Additionally, the environmental exposure has proven to play a significant role in neural activation in which monolinguals have a weaker neural activity in response to a foreign language when compared to bilinguals who have been exposed to the secondary language since birth (Kim, 2019). These findings helped neuroscientists determine that the secretion of languages starts very early in development, raising the possibility in a difference in brain structure, neuroplasticity, and function connectivity in those who learn multiple languages from birth.
With an increase of individuals learned a second language simultaneously from birth, neuroscientists and scientific researchers are using simultaneous bilinguals as their experimental models to further understand the relationship between language acquisition and language acquisition in terms of critical periods. Bilingualism has enabled scientists’ comprehension on how the brain develops at different stages of life and the environments in which they acquire the second language. The previous research studies on language, and many others, provide an insight on the manifestation of skills and language acquisition neuroplasticity, leaving scientists to wonder whether age of acquisition and proficiency are the defying and influencing variables in skill acquisition and its relationship with neuroplasticity and neural connectivity.
Influenced by Penfield and Roberts 1959’s findings that distinguished the difficulty in learning a secondary language after puberty due to significant brain maturation, Berken et al. proposed that capability to learn language was based on nested optimal periods. Their study focused on simultaneous bilinguals, those who acquired two languages at birth, and sequential bilinguals, those who acquired their second language later in life. This distinction showed a difference in neural activation rather than localization in sequential bilinguals, when compared to simultaneous bilinguals in the neuroimages. The increase activity of neural substrates in sequential bilinguals exhibit greater cognitive effort to reach native-like proficiency and retrieval of inhibitory control mechanism when speaking the secondary language. Sequential bilinguals’ brain has matured neural connectivity prior to the acquisition of the secondary language, leading to a decrease in gray matter density when compared to the simultaneous bilinguals’ neuroimages. While those who simultaneously learn both languages at birth have less significant activation in the speech production regions when speaking the secondary language due to minimal cognitive effort based on their early exposure of the languages. Even though there’s less significant neural activation in simultaneous bilinguals, there’s greater neural connectivity between the left and right inferior frontal gyrus and an increase in gray matter density in the left putamen. (Berken et al., 2017).
As shown through their complex neural connectivity and increased neuroplasticity, when two languages are acquired from birth, the individual’s brain is more effectively organized and has greater gray matter density in the language-oriented regions. An increase in gray matter density in such regions have shown to have crucial benefits to those with mild cognitive impairments and Alzheimer disease. Duncan et al. examined the cognitive reserve associated in multilinguals with Alzheimer disease. Even though multilinguals with Alzheimer have a decrease tissue density in parahyppocampal region, they were able to able to perform at similar levels as the monolinguals due to their increase cognitive reserve from managing two languages. Additionally, Duncan et al. established a relationship between bilinguals with mild cognitive impairments and increased gray matter. Bilinguals are exhibiting delays in symptom onset and diagnosis with mild changes in cognitive functions because of their ability to maintain memory functioning that are dependent on increased gray matter in the brain. These findings hypothesize that bilinguals compensate the dementia symptoms by relying on their enhanced executive control abilities used in language retrieval, when compared to monolinguals (Duncan et al., 2018).
The impact of multiple language acquisition is still being investigated as new neuropsychological research findings emerge. But neuroscientists keep circling back to the fact that it is highly beneficial to learn two languages from birth due its influence on the brain’s functional connectivity, neuroplasticity and structure.
References
Berken, J. A., Gracco, V. L., & Klein, D. (2017). Early bilingualism, language attainment, and brain development. Neuropsychologia, 98, 220–227. https://doi.org/10.1016/j.neuropsychologia.2016.08.031
Duncan, H. D., Nikelski, J., Pilon, R., Steffener, J., Chertkow, H., & Phillips, N. A. (2018). Structural brain differences between monolingual and multilingual patients with mild cognitive impairment and Alzheimer disease: Evidence for cognitive reserve. Neuropsychologia, 109, 270–282. https://doi.org/10.1016/j.neuropsychologia.2017.12.036
Gration, A. (2022, April 5). Bilingualism statistics in 2021: US, UK & Global. Language learning with Preply Blog. Retrieved May 1, 2022, from https://preply.com/en/blog/bilingualism-statistics/
Kim, J. (2019, December 13). Bilingualism: Start early, and earn all your benefits! Science in the News. Retrieved May 1, 2022, from https://sitn.hms.harvard.edu/flash/2019/bilingualism-start-early-and-earn-all-your-benefits/
Tao, L., Wang, G., Zhu, M., & Cai, Q. (2021). Bilingualism and domain-general cognitive functions from a neural perspective: A systematic review. Neuroscience & Biobehavioral Reviews, 125, 264–295. https://doi.org/10.1016/j.neubiorev.2021.02.029
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