Electro-Haptic Enhancement of Spatial Hearing in Cochlear Implant Users

Abstract

Cochlear implants (CIs) have enabled hundreds of thousands of profoundly hearing-impaired people to perceive sounds by electrically stimulating the auditory nerve. However, CI users are often very poor at locating sounds, which leads to impaired sound segregation and threat detection. We provided missing spatial hearing cues through haptic stimulation to augment the electrical CI signal. We found that this "electro-haptic" stimulation dramatically improved sound localisation. Furthermore, participants were able to effectively integrate spatial information transmitted through these two senses, performing better with combined audio and haptic stimulation than with either alone. Our haptic signal was presented to the wrists and could readily be delivered by a low-cost wearable device. This approach could provide a non-invasive means of improving outcomes for the vast majority of CI users who have only one implant, without the expense and risk of a second implantation.

Figure 1

Haptic stimulation significantly reduces localisation error in cochlear implant users. (A,B) Mean response location vs actual sound source location before and after training (grey line = perfect localisation performance). (C,D) RMS error before and after training (grey bar = chance performance, +/− 95% confidence). Error bars show the standard error of the mean.

Figure 2

Training improves localisation performance and facilitates multi-modal integration. (A,B) Change in RMS error for each individual for the Audio-haptic and Haptic-only conditions relative to the Audio-only condition in the pre-training session. (C) Change in RMS error for the audio-only condition after training. (D) Performance in the Audio-haptic condition relative to the Haptic-only condition before and after training. Users with unilateral and bimodal device configurations with and without linked devices are indicated by different lines and markers (see legend).

Figure 3

Schematic illustration of the experimental set up. This schematic shows the audio-only condition, where the participant has their hands in their lap rather than their wrists on the shaker contacts. On each trial the audio stimulus was presented through one of the 11 loudspeakers, positioned at points between 75° to the left and 75° to the right of the centre.