The processing of stress in a foreign language modulates functional antagonism between default mode and attention network regions

Abstract

Lexical stress is an essential element of prosody. Mastering this prosodic feature is challenging, especially in a free-stress foreign language for individuals native to a fixed-stress language, a phenomenon referred to as stress deafness. By using functional magnetic resonance imaging, we elucidated the neuronal underpinnings of stress processing in a free-stress foreign language, and determined the underlying mechanism of stress deafness. Here, we contrasted behavioral and hemodynamic responses revealed by native speakers of a free-stress (German; N = 38) and a fixed-stress (French; N = 47) language while discriminating pairs of words in a free-stress foreign language (Spanish). Consistent with the stress deafness phenomenon, French speakers performed worse than German speakers in discriminating Spanish words based on cues of stress but not of vowel. Whole-brain analyses revealed widespread bilateral networks (i.e., cerebral regions including frontal, temporal and parietal areas as well as insular, subcortical and cerebellar structures), overlapping with the ones previously associated with stress processing within native languages. Moreover, our results provide evidence that the structures pertaining to a right-lateralized attention system (i.e., middle frontal gyrus, anterior insula) and the Default Mode Network modulate stress processing as a function of the performance level. In comparison to the German speakers, the French speakers activated the attention system and deactivated the Default Mode Network to a stronger degree, reflecting attentive engagement, likely a compensatory mechanism underlying the “stress-deaf” brain. The mechanism modulating stress processing argues for a rightward lateralization, indeed overlapping with the location covered by the dorsal stream but remaining unspecific to speech.