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Luk, Gigi

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Luk, Gigi

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Author's Publications: search.filters.isAuthorOfPublication.9cdc81cf-cf55-44b2-84ab-1b7f37c410ec

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Now showing 1 - 10 of 23
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    Brain network activity in monolingual and bilingual older adults
    (Elsevier BV, 2015) Grady, Cheryl L.; Luk, Gigi; Craik, Fergus I.M.; Bialystok, Ellen
    Bilingual older adults typically have better performance on tasks of executive control (EC) than do their monolingual peers, but differences in brain activity due to language experience are not well understood. Based on studies showing a relation between the dynamic range of brain network activity and performance on EC tasks, we hypothesized that life-long bilingual older adults would show increased functional connectivity relative to monolinguals in networks related to EC. We assessed intrinsic functional connectivity and modulation of activity in task vs. fixation periods in two brain networks that are active when EC is engaged, the frontoparietal control network (FPC) and the salience network (SLN). We also examined the default mode network (DMN), which influences behavior through reduced activity during tasks. We found stronger intrinsic functional connectivity in the FPC and DMN in bilinguals than in monolinguals. Although there were no group differences in the modulation of activity across tasks and fixation, bilinguals showed stronger correlations than monolinguals between intrinsic connectivity in the FPC and task-related increases of activity in prefrontal and parietal regions. This bilingual difference in network connectivity suggests that language experience begun in childhood and continued throughout adulthood influences brain networks in ways that may provide benefits in later life.
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    Proficiency and control in verbal fluency performance across the lifespan for monolinguals and bilinguals
    (Informa UK Limited, 2013) Friesen, Deanna C.; Luo, Lin; Luk, Gigi; Bialystok, Ellen
    The verbal fluency task is a widely used neuropsychological test of word retrieval efficiency. Both category fluency (e.g., list animals) and letter fluency (e.g., list words that begin with F) place demands on semantic memory and executive control functions. However letter fluency places greater demands on executive control than category fluency, making this task well-suited to investigating potential bilingual advantages in word retrieval. Here we report analyses on category and letter fluency for bilinguals and monolinguals at four ages, namely, 7-year-olds, 10-year-olds, young adults, and older adults. Three main findings emerged: 1) verbal fluency performance improved from childhood to young adulthood and remained relatively stable in late adulthood; 2) beginning at 10-years-old, the executive control requirements for letter fluency were less effortful for bilinguals than monolinguals, with a robust bilingual advantage on this task emerging in adulthood; 3) an interaction among factors showed that category fluency performance was influenced by both age and vocabulary knowledge but letter fluency performance was influenced by bilingual status.
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    How iconic are Chinese characters?
    (Cambridge University Press, 1999) BIALYSTOK, ELLEN; Luk, Gigi
    The study explores the notion that some Chinese characters contain pictorial indications of meanings that can be used to help retrieve the referent. Thirty adults with no prior knowledge of Chinese guessed the meanings of twenty Chinese characters by choosing between one of two photographs. Half of the characters were considered to be iconic and the other half was considered to be arbitrary. The proportion of correct guesses for iconic characters was high, but the proportion for arbitrary characters was at chance. These results show a distinction between characters based on the extent to which they have retained aspects of iconicity in reference to their concepts that can direct the reader to their meaning. The results have implications for using pictures to promote the understanding of the orthographic–semantic process in simple Chinese characters.
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    Lifelong Bilingualism Maintains White Matter Integrity in Older Adults
    (Society for Neuroscience, 2011) Luk, Gigi; Bialystok, E.; Craik, F. I. M.; Grady, Cheryl
    Previous research has shown that bilingual speakers have higher levels of cognitive control than comparable monolinguals, especially at older ages. The present study investigates a possible neural correlate of this behavioral effect. Given that white matter (WM) integrity decreases with age in adulthood, we tested the hypothesis that bilingualism is associated with maintenance of WM in older people. Using diffusion tensor imaging, we found higher WM integrity in older people who were lifelong bilinguals than in monolinguals. This maintained integrity was measured by fractional anisotropy (FA) and was found in the corpus callosum extending to the superior and inferior longitudinal fasciculi. We also hypothesized that stronger WM connections would be associated with more widely distributed patterns of functional connectivity in bilinguals. We tested this by assessing the resting-state functional connectivity of frontal lobe regions adjacent to WM areas with group differences in FA. Bilinguals showed stronger anterior to posterior functional connectivity compared to monolinguals. These results are the first evidence that maintained WM integrity is related to lifelong naturally occurring experience; the resulting enhanced structural and functional connectivity may provide a neural basis for “brain reserve.”
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    The Source of Enhanced Cognitive Control in Bilinguals: Evidence From Bimodal Bilinguals
    (Sage Publications, 2008) Emmorey, Karen; Luk, Gigi; Pyers, Jennie E.; Bialystok, Ellen
    Bilinguals often outperform monolinguals on nonverbal tasks that require resolving conflict from competing alternatives. The regular need to select a target language is argued to enhance executive control. We investigated whether this enhancement stems from a general effect of bilingualism (the representation of two languages) or from a modality constraint that forces language selection. Bimodal bilinguals can, but do not always, sign and speak at the same time. Their two languages involve distinct motor and perceptual systems, leading to weaker demands on language control. We compared the performance of 15 monolinguals, 15 bimodal bilinguals, and 15 unimodal bilinguals on a set of flanker tasks. There were no group differences in accuracy, but unimodal bilinguals were faster than the other groups; bimodal bilinguals did not differ from monolinguals. These results trace the bilingual advantage in cognitive control to the unimodal bilingual’s experience controlling two languages in the same modality.
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    The universality of symbolic representation for reading in Asian and alphabetic languages
    (Cambridge University Press, 2007) BIALYSTOK, ELLEN; Luk, Gigi
    Neuroimaging studies of reading have identified unique patterns of activation for individuals reading in alphabetic and Asian languages, suggesting the involvement of different processes in each. The present study investigates the extent to which a cognitive prerequisite for reading, the understanding of the symbolic function of print, is common to children learning to read in these two different systems. Four-year-old children in Hong Kong learning to read in Cantonese and children in Canada learning to read in English are compared for their understanding of this concept by means of the moving word task. Children in both settings performed the same on the task, indicating similar levels of progress in spite of experience with very different writing systems. In addition, the children in Hong Kong benefited from the structural similarity between certain iconic characters and their referents, making these items easier than arbitrary characters. These results point to an important cognitive universal in the development of literacy for all children that is the foundation for skilled reading that later becomes diverse and specialized.
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    Receptive vocabulary differences in monolingual and bilingual children
    (Cambridge University Press, 2010) BIALYSTOK, ELLEN; PEETS, KATHLEEN F.; YANG, SUJIN; Luk, Gigi
    Studies often report that bilingual participants possess a smaller vocabulary in the language of testing than monolinguals, especially in research with children. However, each study is based on a small sample so it is difficult to determine whether the vocabulary difference is due to sampling error. We report the results of an analysis of 1,738 children between 3 and 10 years old and demonstrate a consistent difference in receptive vocabulary between the two groups. Two preliminary analyses suggest that this difference does not change with different language pairs and is largely confined to words relevant to a home context rather than a school context.
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    Receptive vocabulary differences in monolingual and bilingual adults
    (Cambridge University Press, 2012) Luk, Gigi; BIALYSTOK, ELLEN
    English receptive vocabulary scores from 797 monolingual and 808 bilingual participants between the ages of 17 and 89 years old were aggregated from 20 studies to compare standard scores across language groups. The distribution of scores was unimodal for both groups but the mean score was significantly different, with monolinguals obtaining higher standard scores than bilinguals. Consistent with previous research, older adults had higher vocabulary scores than younger adults. The results are discussed in terms of the implications for theoretical conceptions of linguistic processing and clinical diagnosis in bilingual populations.
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    Is there a relation between onset age of bilingualism and enhancement of cognitive control?
    (Cambridge University Press, 2011) DE SA, ERIC; BIALYSTOK, ELLEN; Luk, Gigi
    Young English-speaking monolingual and bilingual adults were examined for English proficiency, language use history, and performance on a flanker task. The bilinguals, who were about twenty years old, were divided into two groups (early bilinguals and late bilinguals) according to whether they became actively bilingual before or after the age of ten years. Early bilinguals and monolinguals demonstrated similar levels of English proficiency, and both groups were more proficient in English than late bilinguals. In contrast, early bilinguals produced the smallest response time cost for incongruent trials (flanker effect) with no difference between monolinguals and late bilinguals. Moreover, across the whole sample of bilinguals, onset age of active bilingualism was negatively correlated with English proficiency and positively correlated with the flanker effect. These results suggest a gradient in which more experience in being actively bilingual is associated with greater advantages in cognitive control and higher language proficiency.
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    Cognitive control for language switching in bilinguals: A quantitative meta-analysis of functional neuroimaging studies
    (Informa UK Limited, 2012) Luk, Gigi; Green, David W.; Abutalebi, Jubin; Grady, Cheryl
    In a quantitative meta-analysis, using the activation likelihood estimation method, we examined the neural regions involved in bilingual cognitive control, particularly when engaging in switching between languages. The purpose of this study was to evaluate the bilingual cognitive control model based on a qualitative analysis [Abutalebi, J., & Green, D. W. (2008). Control mechanisms in bilingual language production: Neural evidence from language switching studies. Language and Cognitive Processes, 23, 557-582.]. After reviewing 128 peer-reviewed articles, ten neuroimaging studies met our inclusion criteria and in each study, bilinguals switched between languages in response to cues. We isolated regions involved in voluntary language switching, by including reported contrasts between the switching conditions and high level baseline conditions involving similar tasks but requiring the use of only one language. Eight brain regions showed significant and reliable activation: left inferior frontal gyrus, left middle temporal gyrus, left middle frontal gyrus, right precentral gyrus, right superior temporal gyrus, midline pre-SMA and bilateral caudate nuclei. This quantitative result is consistent with bilingual aphasia studies that report switching deficits associated with lesions to the caudate nuclei or prefrontal cortex. It also extends the previously reported qualitative model. We discuss the implications of the findings for accounts of bilingual cognitive control.