Mismatch negativity and P300 evoked response potentials : perception and discrimination of /r/ and /l/ in Korean and English listeners

This study used behavioral measures in conjunction with electrophysiological measures to study perception and discrimination of /r/ and /I/ in native American-English and Korean listeners. MMN and P300 evoked response potentials (ERP) were obtained from 13 American-English subjects and 19 Korean subjects. The stimuli used to elicit the ERPs were:

Tape One: Odd Tones Variable ISI - tones randomized in an odd-ball paradigm with a 2.0 to 4.0 second variable interstimulus interval - used to produce a P300.

Tape Two: La80/Ra20 Steady ISI - /la/ and /ra/ syllables randomized in an odd-ball paradigm with a 2.0 second constant interstimulus interval - used to produce a MMN.

Tape Three: La2Q/Ra80 Steady ISI - /la/ and /ra/ syllables randomized in an odd-ball paradigm with a 2.0 second constant interstimulus interval (opposite of Tape Two) - used to produce a MMN.

Tape Four: La20/Ra80 Variable ISI - /la/ and /ra/ syllables randomized in an odd-ball paradigm with a 2.0 to 4.0 second variable interstimulus interval - used to produce a P300.

All subjects, English and Korean, were given two discrimination tasks (AB and ABX paradigm) along with the four taped conditions, The Korean subjects were divided into "Proficient' and "Non-Proficient" speakers of English based on their ABX scores.

It was hypothesized that the P300s elicited by the tonal stimuli and the MMNs elicited by the syllables would reveal no differences in the latencies and amplitudes among the three groups. The P300S elicited by the syllables were, however, expected to reveal prolonged latencies and reduced amplitudes in the Non- Proficient Korean group due to the difficulties of perceiving /r/ and /I/, documented in native Korean listeners.

Statistical analyses using MANOVA, ANOVA, Pearson and Spearman Correlation procedures revealed (1) no significant differences in the latencies and amplitudes of the P300s generated by the tonal stimuli among the three groups, and (2) no significant differences in the latencies and amplitudes of the MMNs generated by the phonemic stimuli among the three groups.

Although graphed data appeared to reveal prolonged latencies in the P300s elicited by the syllables for the Non-Proficient Koreans, a one-way MANOVA indicated that there were no statistically significant differences in the latencies or amplitudes among the three groups. Because of this finding, no relationship between the behavioral measures and the electrophysiological measures was found to exist.

These findings could be a function of the relative English proficiency of these Korean subjects (too homogeneous), the result of the subjects making discriminations on an acoustic rather than linguistic basis, and/or the result of a large degree of variability found in the groups' mean latencies and amplitudes.