The influence of a sensitive period on central auditory development in children with unilateral and bilateral cochlear implants

We examined the longitudinal development of the cortical auditory evoked potential (CAEP) in 21 children who were fitted with unilateral cochlear implants and in two children who were fitted with bilateral cochlear implants either before age 3.5 years or after age 7 years. The age cut-offs (<3.5 years for early-implanted and >7 years for late-implanted) were based on the sensitive period for central auditory development described in [Ear Hear. 23 (6), 532.] Our results showed a fundamentally different pattern of development of CAEP morphology and P1 cortical response latency for early- and late-implanted children. Early-implanted children and one child who received bilateral implants by age 3.5 years showed rapid development in CAEP waveform morphology and P1 latency. Late-implanted children showed aberrant waveform morphology and significantly slower decreases in P1 latency postimplantation. In the case of a child who received his first implant by age 3.5 years and his second implant after age 7 years, CAEP responses elicited by the second implant were similar to late-implanted children. Our results are consistent with animal models of central auditory development after implantation and confirm the presence of a relatively brief sensitive period for central auditory development in young children.