How does learning a new language change the brain?
Well over half a century ago, American linguist Benjamin Lee Whorf proposed that language affects perception and thought. Although Whorfian effects have been found in behavioural studies, no studies on the brain have been conducted so far to investigate how learning and the use of language influence brain activity associated with perception.
One of the research interests of our lab is to locate the language function in the brain and understand how these language-related locations interact with brain regions related to other functions such as perception and cognition. Using state-of-the-art functional magnetic resonance imaging (fMRI), we showed that brain regions mediating language processes participate in neural networks that are activated by the perception of colour.
In our brain imaging experiments, we asked participants to perform a discrimination task on colour patches without requiring them to label the colour name of the patches. Interestingly, we found that brain regions associated with word-finding processes were strongly engaged while performing the task (Figure 1).This suggests that the language-processing areas of the brain are automatically involved during colour perception, thus providing the first neuroimaging support for the Whorf hypothesis that language directly affects perception.
Our follow-up study, in which study participants needed to find a patch with a slightly deviating colour tone among 12 otherwise identical patches and name the number of the respective deviating patch (Figure 2), showed further evidence that the brain region responsible for naming colours was activated during a colour-searching task.More importantly, we found that enhanced activity in regions of the visual cortex that are responsible for colour perception coincided with enhanced activity in language-related regions. These results suggest that language may serve as a form of top-down control, modulating the activity of perceptual brain areas such as the visual cortex.
Staying young by learning new languages
One of the key challenges Singapore faces is an ageing society. Previous studies have shown that speaking more than one language can delay the onset of dementia by a few years. Here, we aim to apply our understanding of the influence of language on perception and cognition to evaluate language learning as a means to counter the negative effects of ageing, for instance, in memory capacity and cognitive control.
In our previous fMRI studies, we found that language learning is highly correlated to activity in the left fusiform gyrus and caudate nucleus—regions thought to mediate executive control functions and resolve competition that arises between the first language and a new language that is being learned.
In an ongoing project using another brain imaging technique called electroencephalography, we asked participants to learn a new writing system. Intriguingly, after only one week of training, we found that brain waves related to writing-to-speech-sound mapping in our young adult participants had changed (Figure 3). These imaging studies suggest that adult brains are still plastic and that learning a new language changes the brain not only in language-related areas but also in other cognitive control areas.
We are now designing and examining the feasibility of a community-based language training programme for older adults. Apart from giving older adults the opportunity to expand their linguistic repertoire, it is hoped that these interventions will ultimately aid them in maintaining healthy and active lifestyles, thereby impacting society at large.