COGNITIVE EVOKED-POTENTIALS TO SPEECH AND TONAL STIMULI IN CHILDREN WITH IMPLANTS

We investigated late anti cognitive (mismatch negativity P300) auditor y potentials in 14 children with cochlear implants between the ages of 4 and 12 years. Length of cochlear implant use ranged from 7 to 84 mo nths. Three types of stimulus contrasts were used: (1) a loudness cont rast consisting of a 1500 Hz tone burst presented at 75 (standard) and 90 dB sound pressure level (deviant); (2) a frequency contrast consis ting of a 1500 Hz tone burst (standard) and a 3000 Hz tone burst (devi ant) presented at 80 dB sound pressure level; and (3) a speech contras t consisting of ''heed'' (standard) and ''who'd'' (deviant) delivered with a roving loudness paradigm involving a randomized variation of th e levels of the standard and deviant stimuli. Latencies and amplitudes of components N1, P2, N2, and P3 and a mismatch negativity were measu red. Overall, there were very few missing or unidentifiable components , P3 and mismatch negativity components were identified for all subjec ts and all stimuli. The latencies of most components were affected by stimulus type. There was a trend for longer latencies for the speech c ontrast compared with the loudness or frequency contrasts. This may be a reflection of the increased processing time required for the speech stimuli because of its higher complexity. There were several signific ant correlations between speech recognition and cognitive evoked poten tial latencies. These results indicate that the clinical use of cognit ive evoked potentials in children with cochlear implants is feasible a nd informative.