Foreign Language Learning in Older Adults: Anatomical and Cognitive Markers of Vocabulary Learning Success

Abstract

In recent years, foreign language learning (FLL) has been proposed as a possible cognitive intervention for older adults. However, the brain network and cognitive functions underlying FLL has remained largely unconfirmed in older adults. In particular, older and younger adults have markedly different cognitive profile-while older adults tend to exhibit decline in most cognitive domains, their semantic memory usually remains intact. As such, older adults may engage the semantic functions to a larger extent than the other cognitive functions traditionally considered the most important (e.g., working memory capacity and phonological awareness). Using anatomical measurements and a cognitive test battery, the present study examined this hypothesis in twenty cognitively normal older adults (58-69 years old), who participated in a two-month Italian learning programme. Results showed that the immediate learning success and long-term retention of Italian vocabularies were most consistently predicted by the anatomical measures of the left pars orbitalis and left caudal middle frontal cortex, which are implicated in semantic and episodic memory functions. Convergent evidence was also found based on the pattern of cognitive associations. Our results are consistent with a prominent role of semantic and episodic memory functions in vocabulary learning in older learners.

Keywords: FreeSurfer; caudal middle frontal cortex; episodic memory; foreign language learning; pars orbitalis; semantic memory; structural MRI; vocabulary learning.

Figure 1

Italian learning programme. The whole programme was divided into three phases—initial-learning (visits 1–5), intensive-learning (visits 6–17), and post-learning (visits 18–21). In the initial- and intensive-learning phases, six word lists were taught per vocabulary lesson, each comprising a verb and six nouns. After two vocabulary lessons, there was a revision session. Such a cycle of three sessions was repeated four times during the learning programme (hence × 4 in the figure). Asterisks (*) were used to indicate the visits during which phonological tests were administered (see main text).

Figure 2

Cortical and sub-cortical regions of interest (ROIs).

Figure 3

Learning curves across the five weeks. (A) The accuracy of Ita-to-Can translation across weeks. (B) The accuracy of Can-to-Ita translation across weeks. Solid lines: overall in-class learning performance as a function of week; dotted lines: the scores for the verb and noun components, separately plotted to reflect the structure of the in-class quizzes. The error bars represent standard error means.

Figure 4

Associations of the in-class Can-to-Ita score with the cortical measures. (A) Significant associations at left pars orbitalis, left caudal middle frontal cortex, left entorhinal cortex, and right insula. (B) Subtle modulations in the degree of association between final test scores with the cortical measures, found at left pars orbitalis, right middle temporal gyrus, right caudal anterior cingulate, and right pars orbitalis.

Figure 5

Associations of the final test score with the cortical measures. A more left-dominant network was implicated, with seven left hemisphere regions showing significant associations with the final test score when compared to only two right hemisphere regions.

Figure 6

Correlation matrix among demographic, cognitive, and phonological measures at the initial-learning phase.

Figure 7

Modulation of in-class Can-to-Ita score by cognitive predictors, including (A) HKLLT, (B) Raven's SPM, (C) semantic fluency, (D) English Spoonerism, (E) picture naming, and (F) processing speed. Each point represents the score of one participant at a certain week, and the solid lines are the fitted data based on the LME models.