This study aimed to investigate the effect of the unfamiliar stressed prosody on spoken Thai word perception in the pre-attentive processing of the brain evaluated by the N2a and brain wave oscillatory activity. EEG recording was obtained from eleven participants, who were instructed to ignore the sound stimuli while watching silent movies. Results showed that prosody of unfamiliar stress word perception elicited N2a component and the quantitative EEG analysis found that theta and delta wave powers were principally generated in the frontal area. It was possible that the unfamiliar prosody with different frequencies, duration and intensity of the sound of Thai words induced highly selective attention and retrieval of information from the episodic memory of the pre-attentive stage of speech perception. This brain electrical activity evidence could be used for further study in the development of valuable clinical tests to evaluate the frontal lobe function in speech perception.
