The purpose of this study was to compare the robustness of the event-related potential
(ERP) response, called the mismatch negativity (MMN), when elicited by simple tone
stimuli (differing in frequency, duration, or intensity) and speech stimuli (CV nonword
contrast /de:/ vs. /ge:/ and CV word contrast /deI/ vs. /geI/). The study was conducted
using 30 young adult subjects (Groups A and B; n = 15 each). The speech stimuli were
presented to Group A at a stimulus onset asynchrony (SOA) of 610 msec and to Group
B at an SOA of 900 msec. The tone stimuli were presented to both groups at an SOA
of 610 msec. MMN responses were elicited by the simple tone stimuli (66.7%–96.7% of
subjects with MMN "present," or significantly different from zero, p < 0.05) but not
the speech stimuli (10% subjects with MMN present for nonwords, 10% for words). The
length of the SOA (610 msec or 900 msec) had no effect on the ability to obtain consistent
MMN responses to the speech stimuli. The results indicated a lack of robust MMN elicited
by speech stimuli with fine acoustic contrasts under carefully controlled methodological
conditions. The implications of these results are discussed in relation to conflicting
reports in the literature of speech-elicited MMNs, and the importance of appropriate
methodological design in MMN studies investigating speech processing in normal and
pathological populations.
Key Words
Consonant-vowel tokens - event-related potential - mismatch negativity - simple tones
- stimulus onset asynchrony - words
