Person:

Luk, Gigi

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.

We report the results of two studies investigating lexical access in bilinguals. In Study 1,monolinguals performed better than bilinguals on tests of naming and letter fluency, but not on category fluency. When vocabulary size was considered, most of the effects disappeared or were reduced. In Study 2, a larger group of bilinguals was studied to compare the effect of vocabulary size,and a more restrictive version of the letter fluency task was used to increase executive processing involvement. In this case, bilinguals with matched vocabulary scores outperformed monolinguals on letter fluency, and bilinguals with lower vocabulary scores performed at the same level as monolinguals. The results are discussed in terms of the contributions of vocabulary size and executive control to performance on lexical retrieval tasks.