Fig. 1.

Electrode design for a vestibular implant that stimulates all 5 vestibular end organs. A: 3-dimensional (3D) reconstruction of chinchilla microcomputed tomograhy and microMRI scans (Hayden et al. 2011) was used to design new electrode arrays to target the utricle and saccule (blue indicates the lumen and yellow the neural epithelium). A, anterior; P, posterior; D, dorsal; H, horizontal. B: the electrode array was designed to have as many contacts on the utricle and saccule while still maintaining safe charge injection. With these constraints, in addition to those from the fabrication process, an array of 13 activated iridium oxide film (AIROF) electrodes for the utricle and 13 for the saccule (outlines of end organs adapted from Desai et al. 2005) were designed to lay on the macular surface of each end organ. C: the polyimide/gold/AIROF array has 2 large connectors (C1 and C2) through which a printed circuit board can connect to the array’s 50 electrodes on 3 different shanks. The 1st shank (C3) has 8 contacts to target the horizontal semicircular canal and the array of 13 for the saccule, the next shank (C4) has 8 contacts for the superior canal with 13 for the utricle, and the final shank (C5) has 8 electrodes for the posterior canal. D: view from postero-supero-lateral through a surgical microscope during electrode implantation. The surgical approach through the bulla of the chinchilla provides access to all 3 canal ampullae. A small hole was made in or near each ampulla, and the electrode array shank with 8 posterior canal electrodes was inserted to a predetermined depth based on the 3D anatomical model shown in A. The horizontal canal + saccule and the anterior canal + utricle shanks are inserted through openings made near each canal’s ampulla. Placement of electrodes targeting utricle and saccule relies on canal bone landmarks, the trajectory of insertion and electrode array geometry.