[Auditory perception in patients with multiple and severe handicaps: study of mismatch negativity to speech sounds]

We have found that the mismatch negativity (MMN) of event-related potentials (ERPs) to the tone burst sound is generated passively in some multiple and severe handicapped patients. This study investigated whether 10 patients with severe handicaps, whose auditory perception is hard to be evaluated clinically, exhibited MMN to the speech sound (SS). The stimuli included tone bursts of 700 and 1000 Hz in frequency, and 4 patterns of SS (1 phoneme: [a, ae], [a, o]; and 2 phonemes: [amo, ano], [ao, aka]) presented at an 85: 15 occurrence with 75 dBSPL. In the tone burst paradigm, 7 patients had a definite MMN wave followed by an N1 wave. However, a few patients showed MMN to some patterns of SS. The latency of MMN to SS was almost within normal limits. These results suggest that these patients could discriminate subtle differences of frequency in some speech sounds, although their auditory response to actual speech sounds were poor.