Assessing multilingual speakers' language processing through functional near-infrared spectroscopy (fNIRS)

Multilinguals' navigation through three or more language systems utilizing one cognitive system is a phenomenon of recent interest. Few functional near-infrared spectroscopy (fNIRS) studies have focused on brain activations concerning multilinguals. The present study uses picture-naming and fNIRS technique to explore the prefrontal brain activations amongst neurotypical multilinguals belonging to four major provinces of Pakistan. The 26 right-handed participants utilize their native language (Punjabi, Pushto, Sindhi or Balochi), first language (Urdu) and second language (English) distinctively in the experiment. Brain imaging results demonstrate a significant activation of the right prefrontal cortex among the multilingual adults along with left laterality. Moreover, results indicate significant activation of channels demonstrating heavier cognitive load with English in comparison to first or native language(s). The paper suggests that right dorsolateral prefrontal cortex and right medial prefrontal cortex play a significant role in language processing alongside the left prefrontal cortex, exemplifying that peripheral activation during word retrieval, processing and production is a possibility.