Bilingualism Delay of Dementia
As the population of elderly people grow, dementia, Alzheimer’s disease, and other neurodegenerative disorders have become more prevalent. While there is no current pharmacological cure, nonpharmacological approaches including cognitive stimulation, diet, and physical activity has been used a preventative measure. Research has shown that older people who engage in activities such as reading and playing board game are less likely to experience memory loss associated with dementia (Kim et al., 2019). These activities stimulate the brain and in turn strengthen neural connections. The way the brain responds and adapts to environmental stimuli is known as neuroplasticity. Neuroplasticity allows the brain to change shape and function to be more efficient in neural connections after stimuli.
In the paper “Bilingualism for Dementia: Neurological Mechanisms Associated with Functional and Structural Changes in the Brain” (Kim et al., 2019), the authors explore the relationship between bilingualism and dementia. In this study, bilingualism serves an advanced form of cognitive stimulation that has been shown to delay the symptoms of dementia by approximately four to five years. For the brain to learn a second language, new neural connections and structures are formed to allow the brain to manage phonology, semantics, syntax, and grammar of a new language. This high-level brain activity is shown to maintain adult neurogenesis and helps to improve learning. Researchers have identified the subventricular zone to be a potential source of the cells for brain restoration (Kim et al.,). In addition, it shown that older bilingual people, compared to monolinguals, perform better on cognitive tasks. The formation of new synapses, increased axonal growth in granule neurons, and synaptogenesis in the hippocampus are all indicative of learning. These newly formed synapses, formed by learning two languages, compensates for those that become damaged during aging and dementia. Their research also shows that there is an increased functional connectivity in between Broca’s area, Wernicke’s area, dorsolateral prefrontal cortex, dorsal anterior cingulate cortex, and subcortical regions that is associated with bilingualism (Kim et al., 2019). Bilingualism can also help to delay symptoms of dementia by protecting the white matter tracts. As humans age, the density of gray matter is greater reduced in the sensorimotor areas, hippocampus, and entorhinal cortex. Bilingualism increases gray matter density in anterior cingulate cortex, basal ganglia, left caudate, and left putamen (Kim et al., 2019). This could prove as another mechanism to why learning a second languages helps to delay the onset of dementia, Alzheimer’s disease, or other neurodegenerative disorders.
In Dr. Berken’s paper, “Early bilingualism, language attainment, and brain development” (Berken et al., 2017) the researchers further explore the connection between neuroplasticity and bilingualism. Differently than Dr. Kim’s study, Dr. Berken and his colleagues defined bilingualism to be a mastery of two language to a high proficiency. They studied three different groups: English monolinguals, sequential bilinguals, and simultaneous bilinguals. Like Dr. Kim’s study, they found that the sequential bilinguals who had a better accent had greater gray matter density in their left putamen. They found that when sequential bilinguals were speaking their second language, there was higher activation in the premotor cortex, inferior frontal gyrus, and fusiform gyrus. They also discovered a positive correlation between age of acquisition of second language and BOLD fMRI signals. The later the second language was learned, the more activation there is in the premotor area, inferior frontal gyrus, and fusiform gyrus. Dr. Berken and his colleagues concluded that simultaneous bilinguals, those who learned two languages from a very early age, have an increased functional connectivity that requires minimal neural effort to speak in either language. Their BOLD signals in an fMRI look very similar to the English monolinguals when they are speaking English. They also concluded that sequential bilinguals have brain organization that is indicative to learning changes later in life. Both sequential and simultaneous bilinguals provide evidence of neuroplasticity, just is different ways.
Overall, bilingualism encourages advanced learning, cognitive stimulation, and neuroplasticity that can help reduce or delay the effects of aging and symptoms of neurodegenerative disorders.
References
Berken, J. A., Gracco, V. L., Klein, D. (2017). Early bilingualism, language attainment, and brain development. Neuropsychologia. https://www.sciencedirect.com/science/article/abs/pii/S0028393216303293
Kim, S., Jeon, S. G., Nam, Y., Kim, H. S., Yoo, D. H., & Moon, M. (2019). Bilingualism for Dementia: Neurological Mechanisms Associated With Functional and Structural Changes in the Brain. Frontiers in neuroscience, 13, 1224. https://doi.org/10.3389/fnins.2019.01224
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