Thalamocortical activity and plasticity in children using cochlear implants

The electrically evoked middle latency response (EMLR), reflecting thalamocortical activity, was recorded in 81 children with pre- or perilingual deafness. Repeated measures were made in 50 children at the time of implantation, at the initial device stimulation, and again after 2, 6, and 12 months of implant use. EMLRs were measured once in 31 children who had 5.3 +/- 2.9 years of implant experience. EMLRs were rarely detected at the time of implant surgery and were poorly detected on the first day of device activation. Detection improved significantly with consistent implant use. Older children were more likely to have detectable EMLRs at early stages of device use than younger children. However, younger children tended to have more rapid rates of increase in delectability of EMLRs with duration of use than their older peers. Thus, in children: (1) clinical use of EMLRs at the time of initial implantation may be limited;, (2) neural synchrony at the level of the thalamus and auditory cortex improves with consistent cochlear implant use; and (3) thalamocortical plasticity may be limited by the period of deprivation prior to implantation and/or the age at implantation. (c) 2004 Elsevier B.V. All rights reserved.