Neural Substrates Of Speech Production:the Role Of Domain-general Cognitive Functions

Speech production is a complex activity,which involves not only languagespecific processes,but also domain-general cognitive processes,especially working memory and inhibition.Previous research mostly focused on alphabetic languages like English,seldom studies examined non-alphabetic languages like Chinese.Therefore,in this study,we investigated the brain activation of participants under different production modes(i.e.,covert,overt,and handwritten)and different cue stimuli types(pinyin and radical)using fMRI technique.Another aim was to examine the role of domain-general cognitive functions(working memory and inhibitory control)in lexical production,so the brain activation under n-back task and stopsignal task were also recorded.The findings reveal 1)a general neural network for Chinese lexical production,which cover left inferior frontal gyrus,parietal lobe,subcortical regions,and cerebellum.As for different stimuli types,pinyin production activated more left inferior frontal gyrus,parietal lobe,and motor related areas,whereas radical production activated more bilateral occipital areas.This may be because pinyin production need to access phonological information and select between co-activated candidates across more aspects(e.g.,vowel selection,tone selection),while radical production would rely more on an orthographic pathway.Furthermore,covert and overt production differed in brain activation patterns.Overt production involves more motor,auditory and somatosensory areas due to motor execution and sensory feedback from their own output,while covert production involves bilateral inferior frontal cortex,right superior frontal gyrus and the anterior cingulate cortex,which may be associated with non-language cognitive processes.2)Conjunction analysis of the three tasks showed that language specific areas mainly lie in left frontal cortices.Verbal fluency,n-back,and stop-signal tasks commonly activated bilateral parietal areas,which is consistent with previous findings that the parietal lobe is a domain-general processing system.This study indicates Chinese lexical production involves a general neural network,and different stimuli cues and production modes involve different brain areas.Language-specific areas mainly lie in left frontal lobe,while parietal areas may underlie domain-general cognitive functions in speech production.