Description of the ELARs

Electrical N1-P2 cortical responses of the ELAR could be recorded for stimulation by all selected electrodes from all subjects. The morphology of the ELAR recordings was consistent with other reported ELAR findings (e.g., Maurer et al., 1999; Firszt et al., 2002a,b). The mean latency values across electrodes were 86.4 msec (± 3.1) for N1, 178.7 msec (± 6.3) for P2, and 92.3 msec (± 4.3) for N1-P2 interval, standard errors being indicated between brackets. Figure 1 displays N1-P2 responses evoked by stimulation delivered by electrodes 3, 7, 11, and 15 in Subject 12. Individual waveforms recorded from all fourteen subjects and evoked by stimulation delivered by electrode 7 are shown in Figure 2.

Figure 1. N1-P2 responses recorded from Subject 12 on electrodes 3, 7, 11, and 15 at comfortably loud intensity. N1 and P2 are indicated. CU: Current Unit (proportional to microamperes). Negativity is up.

Figure 2. Individual waveforms recorded at comfortably loud intensities for stimulation on electrode 7 (medium electrode) from all fourteen subjects. N1 and P2 are indicated. The subjects’ speech perception score in quiet (phonemes presented at 65 dB HL) at three months of cochlear implant use are indicated, as well as the intensity of stimulation used for ELAR recording. CU: Current Unit (proportional to microamperes). Negativity is up.