Comparison of behavioral discrimination, MMN and P300 to speech and non-speech stimuli

This study examined the relation of central auditory processes and perception abilities to speech and non-speech stimuli. Behavioral responses and auditory evoked potentials (MMN and P300) of ten native English speaking males/females were evaluated to consonant-vowel speech (two within-category stimuli) and non-speech (two frequency glides whose frequencies matched the formant transitions of the consonant-vowel stimuli) synthetically-generated contrasts. The stimuli were presented monaurally to the right ear of all listeners. Listeners exhibited the best discrimination to the non-speech in same/different and oddball behavioral discrimination procedures. MMN responses were present in all subjects, without regard to stimulus type. P300s were elicited in nine of ten subject to the non-speech contrast, and in four of ten to the speech contrast. These results suggest that the two types of stimuli were processed differently in behavioral responses and P300 but not in the MMN responses. The enhanced discrimination of the frequency glide (non-speech) stimuli versus the CV (speech) stimuli of analogous acoustical content support the idea that the processing of speech is mediated differently than non-speech at higher levels in the auditory system.