Fast recovery of binaural spatial hearing in a bilateral cochlear implant recipient

Although recent studies have documented that binaural cochlear implantation (CI) can restore spatial hearing, the time-course of such recovery and the role of previous binaural experience remain unclear. Here, we report, for the first time, a different time-course of spatial hearing recovery in two binaural CI recipients that substantially differ in terms of previous binaural experience. Both CI recipients had 5 years of monaural CI experience at the time of activation of the second implant. However, while recipient S.P. became deaf late in life, recipient P.A. became deaf in early childhood. At the time of binaural activation, P.A. was above chance at localizing sounds with both monaural and binaural hearing; on the contrary, S.P. was above chance with monaural hearing only. Strikingly, 1-month after activation, S.P. substantially improved his binaural localisation abilities (at the expenses of monaural ones), while P.A.’s performance remained stable regardless of hearing condition. Results show that recovery of binaural spatial abilities can occur rapidly after bilateral CI. However, deafness onset and duration of previous binaural experience may be critical for such fast plastic changes. Recovery of binaural hearing also conflicts with previously developed localisation abilities with monaural CI, suggesting competing auditory space representations in the brain.