Context modulates processing of speech sounds in the right auditory cortex of human subjects.

Using whole-head magnetoencephalography, we studied how context affects processing of speech sounds by recording the magnetic counterpart (MMNm) of the mismatch negativity (MMN) event-related potential, which is elicited in the auditory cortex by a contrast between infrequent and frequent auditory stimuli. In Experiment 1, in the right, but not in the left, hemisphere auditory cortex, a contrast of consonant-vowel syllables elicited a stronger MMNm when presented within a word context than when occurring alone. Further, in Experiment 2, these same syllable contrasts were processed in the right auditory cortex more strongly when embedded in a non-speech sound context than when presented alone. This facilitation thus was insensitive to the phonetic and semantic features of the context but might nevertheless reflect the participation of the right hemisphere in speech perception.