This study aimed to investigate the effect of the unfamiliar stressed word on spoken Thai word perception in the pre-attentive processing evaluated by N200 component. EEG recording was obtained from eleven participants, who were instructed to ignore the sound stimuli while watching silent movies.

The unfamiliar stress word elicited N200 amplitude was higher than familiar stress word which was principally generated in the frontal area. It was possible that the unfamiliar stressed word of Thai language induced highly selective attention and retrieval of information from episodic memory. These results suggested that native Thai speakers who are familiar to using the tones in Thai language can perceive and discriminate the stress word correspondingly to the native stress language speakers in pre-attentive stage of speech perception.

Therefore, these data show the role of the frontal area in the auditory pre-attentive processing in Thai stress word perception in native Thai speakers. It needs further study whether frontal lobe lesions affect the sound discrimination at pre-attentive stage, then this will provide another valuable test to evaluate the frontal lobe function in the future.            

 Keywords: Speech perception; Pre-attentive; N200; ERP