The Bilingual Brain: Learning, Language, Longevity

Written By Alexis Earp and Erin Kaufman

Alexis Earp and Erin Kaufman

Illustrations by Abigail Schoenecker

It is almost impossible for a person living in the United States to go about their day-to-day life without encountering a variety of non-English words and phrases. A sign at the pharmacy may include the Spanish word farmacia. Care tags that advise machine-washing a sweater in cold water might include the Mandarin phrase 冷水机洗. A party host could serve hors-d’œuvres. However, for many Americans, exposure to a non-English language is more than just a passing moment: it is a vital method of communication. In the U.S. alone, 67.8 million residents speak a language other than English at home — a number roughly equivalent to the population of France [1, 2]. Since 1980, the percentage of bilinguals in the U.S. has almost doubled [3]. Globally, more than half of the world’s population is estimated to be bilingual [3]. However, the impact of bilingualism reaches far beyond census data: compared to monolinguals, bilinguals demonstrate physiological differences in their brains [4]. Although most bilinguals do not learn two languages in an attempt to reap these physiological benefits, a fascinating aspect of bilingualism is that it seems to aid in preserving certain brain functions as one ages [4, 5].

Aging is Inevitable: C’est la Vie!

The natural and inevitable process of aging may be accompanied by a deterioration of certain brain functions, such as the ability to make decisions and process new information [6]. For example, an avid reader may be able to grow their vocabulary, but the speed at which they can learn new words slows as they age [6]. This phenomenon, called cognitive decline, is a natural result of aging that is accompanied by structural changes in the brain [6]. Neural atrophy, a process through which brain volume and connections between brain cells deteriorate over time, can interfere with cognitive processes associated with language production and memory [6, 7, 8]. Although age-related cognitive decline is normal and inevitable, not everyone experiences it to the same degree [6, 9]. The ability to resist the physiological effects of aging, also known as cognitive reserve, varies among individuals [10]. While cognitive reserve may in part be influenced by genetics, lifestyle practices — such as reading regularly, completing brain teasers, or learning a second language — can help people better resist the effects of cognitive decline and improve cognitive reserve by strengthening the adaptability, or plasticity, of their brain [10, 11, 12].

Audio, Video, Disco: Exercising the Brain Through Learning

Neuroplasticity is the nervous system’s ability to modify connections between neurons in response to a person’s life experiences, such as injury, aging, and learning [13]. Imagine you are going to the gym for the first time: in the beginning, you may only be able to lift light weights or run a short distance. As you continuously adapt to an exercise routine, your heart and muscles grow stronger, improving not only your ability to perform specific exercises at the gym, but also your ability to successfully tackle new forms of physical activity, like playing volleyball. A similar process happens in the brain: as you use specific pathways in your brain, connections between neurons are reinforced, strengthening these pathways [14]. Completing brain teasers and puzzles on a regular basis has been suggested to strengthen cognitive reserve because the brain is challenged with tasks that reinforce previously created pathways [15]. Strengthening these pathways makes the brain more resistant to neural atrophy [6, 16]. Similarly to performing brain teasers, speaking two languages may protect against cognitive decline by increasing neuroplasticity [4].

White Matter: A Certain Je Ne Sais Quoi

Distinct structural and functional differences at the neuronal level in the bilingual brain may be indicative of increased neuroplasticity [4, 17, 18]. The part of the neuron that carries electrical signals from one neuron to another, called an axon, is structurally different in bilinguals than in monolinguals [18, 19, 20]. Axons are surrounded by a layer of fatty tissue called myelin, and these myelinated axons make up a type of tissue called white matter. Axon density and the integrity of white matter in the brain can be measured via fractional anisotropy (FA), where a high FA value indicates greater axon integrity. [19, 21]. Older bilinguals tend to have higher neuronal levels of FA compared to older monolinguals in areas associated with language processing, suggesting greater axon strength or insulation in bilinguals [19, 20, 22, 23]. Older bilinguals have also been found to have a greater amount of white matter in the brain, particularly in their corpus callosum, a structure that bridges the two hemispheres of the brain [21, 22, 24]. Brain regions associated with language processing span both hemispheres, so increased white matter volume in the corpus callosum may aid in the exchange of information between neural regions [22, 25, 26]. The higher FA values and greater white matter volume observed in the corpus callosum are also observed in the arcuate fasciculus —  a bundle of axons that connect regions of the brain associated with language — of bilinguals when compared to monolinguals [22, 23, 27]. An increase in FA, and therefore an increase in white matter integrity, may be correlated with enhanced neuroplasticity in bilinguals [17, 22].

Bona Fide Benefits: Bilingualism Preserving the Brain

In addition to enhanced neuroplasticity, bilinguals demonstrate greater preservation of language-associated brain regions as they age [28]. The superior longitudinal fasciculus (SLF), a collection of fibers in the brain that connects several of the brain’s lobes, is thought to play a role in language, memory, and attention control [29]. Bilinguals display higher levels of myelination of axons in the SLF than monolinguals: myelination may help protect important neuronal connections from age-related degradation [23, 29]. The preservation of myelinated axons may be linked to the preservation of cognitive functions in bilinguals [23, 29]. Additionally, there is differing preservation of gray matter, or neuronal cell bodies, between aging bilinguals and monolinguals in a region of the brain involved with speech production known as Broca’s area [30, 31]. Although Broca’s area is primarily known for its role in language production, it also regulates working memory, memory processing, and action perception and execution [32]. The greater preservation of gray matter in Broca’s area may allow bilinguals to easily switch between multiple languages [22, 32, 33, 34]. The conservation of white and gray matter within language-associated regions in the brain supports the hypothesis that bilinguals have a greater cognitive reserve [22, 33, 34].

Lifelong Benefits: Say Hola to Cognitive Reserve

In addition to observed structural changes in the bilingual brain, older bilingual adults seem to exhibit improved cognitive functions, including memory and attention preservation [11, 22, 35]. Bilinguals demonstrate a greater ability to switch their attention between multiple tasks, outperforming monolinguals on auditory attention-related tasks [20,36]. While performance in attention-related tasks declines as all individuals age, bilinguals seem to continue to outperform monolinguals in these tasks, suggesting greater retention of memory and attention [36]. Furthermore, bilinguals exhibit higher gray matter volume in the superior temporal gyrus — a brain region associated with auditory attention — and this increase in gray matter may underlie improved attention abilities in bilingual individuals [20, 22, 37]. In addition to attention tasks, older bilinguals also seem to perform better than older monolinguals on tasks related to working memory, which refers to the brain’s ability to retain newly learned information and apply it to a current task [38, 39]. This heightened performance may also be connected to the functioning of the SLF because of its involvement in language, memory, and attention [40]. Furthermore, there is also a correlation between increased myelination in the SLF and improved working memory, which could lead to bilinguals performing better on working memory tasks than monolinguals [29]. Physiological differences between older bilinguals and monolinguals support the conclusion that there are long-term benefits and improved cognitive reserve in bilinguals [6, 29].

Hakuna Matata: It’s Never Too Late

Bilingualism appears to be associated with physiological changes in the brain that aid in preserving cognitive functions [20]. Though more research is needed to solidify these findings, learning a second language could be a promising way to delay not only cognitive decline but also age-related cognitive conditions such as some neurodegenerative diseases [41]. Due to the potential long-term cognitive benefits, bilingualism is now being studied as a possible means of cognitive therapy for older populations [41, 42]. While early language learning has been linked with greater neuroplasticity, language learning at any age will allow one to reap some of the physiological benefits of bilingualism [20, 35]. Research on bilingualism as a form of cognitive therapy is critical because as the aging population grows, the strain of cognitive decline on families, healthcare systems, and economies will only become more pronounced [41]. A rise in bilingualism could lead to improved cognitive reserve in the global population [20, 41]. The benefits of bilingualism span beyond communication: they build pathways to healthier people, healthier communities, and healthier futures.

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