Abstract
Purpose Mismatch negativity (MMN) reflects a preperceptual neurophysiological response that
is generated subconsciously due to the interruption of a memory trace of ongoing sensory
events in the environment. It has been widely used by researchers to understand complex
perceptual mechanisms. Furthermore, it has been recommended as an objective tool to
investigate disorders related to auditory cognition in hearing aid and cochlear implant
users. Many researchers suggest that utilizing a larger acoustic difference between
standard and deviant stimuli within the oddball paradigm will lead to a more robust
MMN response. The purpose of the present study is to examine if increasing the abstract
phonemic contrast between standard and deviant stimuli in the oddball paradigm leads
to a more robust MMN response.
Methods Fourteen young female adults participated in the present study. To ensure that the
MMN response was elicited by phonemic and not acoustic differences in the stimuli,
a one-to-many ratio was created for the abstract phonemic features while controlling
the acoustic features when designing the oddball paradigm as described by Phillips
et al. (2000). MMN amplitude was measured at the Cz and Fz electrodes in two conditions,
with two trials in each condition. In condition 1, the standards and deviants differed
by one distinctive feature: voicing in trial 1 (/tӕ/ was standard and /dӕ/ was deviant)
and place of articulation in trial 2 (/bӕ/ was standard and /dӕ/ was deviant). In
condition 2, the standards and deviants differed across two distinctive features:
voicing and place of articulation. In trial 1, /pӕ/ was standard and /dӕ/ was deviant;
in trial 2, /dӕ/ was standard and /pӕ/ was deviant.
Results MMN amplitudes elicited by two distinctive features were significantly larger than
MMN amplitudes elicited by one distinctive feature (p < 0.001). Trials 1 and 2 in each condition showed no statistical difference, and
they were repeatable and highly correlated. Recordings from the Cz and Fz electrodes
showed no statistical difference and were highly correlated and similar in morphology.
Conclusion It is known in the literature that increasing acoustic complexity elicits a more
robust MMN. The present study showed that this assumption can be extended to abstract
phonemic complexity. Increasing the phonemic complexity by utilizing more distinctive
features in the oddball paradigm increased the amplitude and robustness of the MMN.
Keywords
MMN - mismatch negativity - phonemic MMN - phoneme perception - MMN amplitude
