Verbal communication (Language Processing) displays one of the most essential cognitive functions in everyday social life. As globalization grows, being proficient in several languages gains more and more important even in later stages of life. Hence, it seems crucial to investigate neuronal processes of foreign language learning in adulthood.
Neuroscientific studies showed that even when a foreign language is learned during adulthood, a high proficiency level can be attained while brain areas similar to those of the native language are recruited. In this study(1), at first, an implicit semantic training was conducted with healthy monolingual adults. Subjects had to learn new foreign pseudowords for familiar objects, thus the training resembled a classical second language learning paradigm. They were however interested in neuronal processing during the recall of learned compared to new pseudoword-picture pairings.
Electrophysiological and vascular responses were assessed simultaneously by means of electroencephalography (EEG) and functional near-infrared spectroscopy (NIRS). Both neuroscientific methods are soundless and easily combinable in a relatively natural setting, thus being ideal for the investigation of acoustic stimuli. The EEG excellently tracks online processing mechanisms with a high temporal resolution whereas the fNIRS provides a good spatial resolution of the recruited brain areas.
EEG results showed larger amplitudes for new pseudoword-picture-pairings compared to learned pairings. This effect was displayed by a long-lasting negativity predominantly on right frontal electrodes. Such a result is in line with a typical old/new effect. fNIRS results display greater left-hemispheric activations on frontal areas for learned pseudoword-picture-pairings which mainly cover the left inferior frontal gyrus (IFG).
EEG results supporting the old/new effect indicate that new and therefore unknown pairings require more processing effort on the neuronal level and that just learned pairings might be subject to automatization processes. The IFG has shown to be activated during phonological processing but was also found to be involved in the selection processes of semantic information when competitors are present. During the recall experiment, participants had to distinguish between learned and new pseudoword-picture-pairings, forcing them to actively select between stimuli. This selection process leads to enhanced focused attention on previously learned pairings and is reflected by increased activation in inferior frontal regions in the fNIRS. The results of the study underline the fascinating plasticity of the adult brain during foreign language learning, even after a short semantic training.
(1) Neuronal correlates of foreign language learning in adulthood: A combined EEG and fNIRS study. (2019). Sarah Steber, Nicola König, Sonja Rossi.
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