Using the Electrically-Evoked Auditory Change Complex (eACC) to Evaluate Electrode and Modulation Rate Discrimination

Background

Despite the success of cochlear implants (CIs), outcomes remain variable across individuals. CI users rely on temporal envelope cues for perception and ability to discriminate different rates of envelope modulation is related to outcomes. Likewise, electrode discrimination skills are thought to impact on performance. Here, we used the electrically-evoked auditory change complex (eACC) to assess both modulation and electrode discrimination. Recordings were obtained either by slow or fast periodic changes in an ongoing auditory stimulus, eliciting transient and steady-state eACC responses, respectively.

Methods

Five adult post-lingually deaf Nucleus device users were included. Electrode and modulation discrimination was assessed both behaviorally and objectively (using the eACC). Fast periodic changes (evoking steady-state eACCs) were presented at a rate of approximately 6.4 Hz, while slow changes were presented at a rate of 2 Hz (evoking transient eACCs). Modulation discrimination was assessed at 125 and 801 pps using two modulation depths (50 and 100%) presented on one apical electrode. Electrode discrimination was assessed in three apical electrode pairs at 801 pps.

Results

Slow eACC responses could be evoked for both electrode and modulation experiments. Fast eACC recordings, however, did not elicit responses. Further details of the parameter set exploration will be presented.

Conclusions

Slow eACC can be used to assess modulation and electrode discrimination abilities in CI users. While we previously showed that fast steady-state eACC responses can be obtained from normal hearing listeners, this was not the case for CI users, suggesting that neural generators of the steady-state eACC may be adapted.