The Neuropsychology of Bilingualism: How Language Experience Modifies Brain Function
Summary Abstract:
Substantial evidence from across the lifespan points to modifications in cognitive ability for bilingual individuals performing tasks requiring attentional control, typically described as “executive function”. At the same time, some research, particularly behavioral studies with young adults, fail to detect these differences raising questions about the reliability of the claim. However, research using neuroimaging has uncovered underlying modifications to brain networks attributable to bilingual experience and helps to understand why the behavioral effects occur and why they sometimes do not.
I will review two types of related evidence that demonstrate how bilingual brains differ from those of monolinguals and connect those brain differences to reported behavioral differences. First, studies using electroencephalography (EEG) with young adults and functional magnetic resonance imaging (fMRI) with older adults have shown that the resting state of bilingual brains has better intrinsic functional connectivity than does that of monolinguals. For older adults, the intrinsic connectivity found for bilinguals is similar to that found for younger adults in that it shows network differentiation, whereas older monolinguals show the more typical age-related de-differentiation. Differentiation is generally associated with better cognitive performance.
Second, studies using EEG with young adults and fMRI with older adults have shown that bilingual brains require less effortfulness than monolingual brains to achieve similar cognitive outcomes. Young bilinguals outperformed monolinguals on an n-back task as the demands increased and required less attentional effort as indicated by P3 waveforms; older bilingual performed similarly to monolinguals on a set of tasks despite having significantly less cortical volume and white matter integrity. Together, these types of evidence point to a more efficient brain for bilinguals that can be traced to their language experience. In both cases, behavioral effects are only expected to occur when the attentional demands are challenging and not for simple tasks, a prediction consistent with existing evidence.
Why does this reorganization happen? Early explanations based on adult studies focused on the joint activation of the two languages during bilingual speech processing that led to the need to inhibit the non-target language, increasing the need of selective attention. However, research with infants has shown that preverbal babies in the first year of life being raised in bilingual environments have better control over attention than do those being raised in monolingual environments. Language inhibition cannot account for these results. We know that infants in the first year can distinguish between languages in the environment. The interpretation, therefore, is that the complex bilingual linguistic environment requires increased attentional control and that this control is demonstrated as better selective attention on nonverbal tasks, creating a basis for subsequent modifications in attention networks. Research investigating the functional activity in infant brains is needed to confirm this interpretation and understand more clearly how language environments modify brain networks.
Number of Credit Hours: 1.0
Level of Instruction: Intermediate
Learning Objectives:
1. Recognize the complexity of bilingualism as a multidimensional experience
2. Understand the modifications in brain organization that are associated with bilingual experience
3. Evaluate the relation between language use and changes to brain function
Presenter(s):
Ellen Bialystok, PhD
York University
Ellen Bialystok is a Distinguished Research Professor of Psychology at York University. She is an Officer of the Order of Canada and a Fellow of the Royal Society of Canada. Her research uses behavioral and neuroimaging methods to examine the effect of bilingualism on cognitive processes across the lifespan. Her discoveries include the identification of differences in the development of cognitive and language abilities for bilingual children, the use of different brain networks by monolingual and bilingual young adults performing cognitive tasks, and the postponement of symptoms of dementia in bilingual older adults. Recent studies have investigated the effects of bilingual education on children’s development and the cognitive and brain consequences of bilingualism in older adults. Her current research is examining how lifelong bilingualism may be protective for cognitive decline in older age and contribute to cognitive reserve.
