Foreign language training in seniors to prevent old-age disorders: protocol of a randomized controlled trial

Bilinguals constantly need to mentally juggle several languages, which is said to carry over from the language to the general cognitive domain (Grant, Dennis, & Li, 2014). This effect has behaviorally been found to be manifested as better cognitive flexibility (Kroll & Bialystok, 2013), a skill needed to separate the two languages in one mind (Bice & Kroll, 2015). More so than when learning other new skills, learning a new language interferes with earlier acquired language skills; it impacts first language processing and storage (cf. Li, Legault, & Litcofsky, 2014). It is for this reason that foreign language training is expected to boost cognitive flexibility more than other cognitive training programs. Although there is a wealth of observational studies into bilingual advantages, experimental studies remain scarce. The primary objective of this study is to determine whether a bilingual experience affects cognitive flexibility and its neural underpinnings in 189 elderly speakers with subjective, but not objective, cognitive decline which may or may not be accompanied by mood disorders. We assess the unique role of foreign language training compared to a music training and social intervention. In this paper, we present the method that underlies this study. For three to six months, participants practise the language at home for 45 minutes a day, 5 days a week, and participate in real-life classes every fortnight. We assess cognitive flexibility by means of a color-shape switching task and WCST and we simultaneously measure brain activity using combined fNIRS/EEG methods. We expect an increase in cognitive flexibility and positive effects on health outcomes as a result of both training methods, but more so in the language training compared to the music training. Also, we expect increased power in the theta band network measured through EEG and less hypo-activity in the lateral and medial PFC during switching measured through fNIRS. If effective, foreign language learning could serve as an important tool towards healthy aging: it could contribute to a higher cognitive reserve, slow down cognitive aging and reduce vulnerability for depression.