Mismatch Negativity (MMN) generally increased as a function of the degree of dscrepancy from the standard-stimulus duration. The MMN generator is indeed semitive to even vely small amounts of stimulus energy. The main objective of this study was to investigate the codical activation of level-to-contour tone changes in dfferent vowel duration indexed by mismatch negativity Twenty-two healthy right-handed adults pdcipated in this study. It was found that the long-to-shod vowel duration changes with level-to-fallinglrising and fallmglrising-to-level tone changes perception elicited MMN between 196-220 msec with reference to the standard-stimulus Event-related Potentials (ERPs). The long-to-shod vowel duration and level-tofallinglrising tone changes elicited a strong MMN bilaterally for both native and nonnative speakers of Thai, unhke shod-to-long vowel duration and fallinglrising-to-level tone changes. Source localization analyses performed using Low Resolution Electromagnetic Tomography (LORETA) demomtrated that sources were obtained in the Middle Temporal Gyrus (MTG) of the left hemisphere and in the Superior Temporal Gyrus (STG) of the right hemisphere for both subject groups. © 2012 Asian Network for Scientific Information.