People with congenital deafness may acquire a cochlear implant at a later age and be able to hear. Given that it seems there is a curve for synaptic plasticity of different circuits:
(1) Cochlear implants are used in older children (age 3-8) with moderate success. How can we explain the fact that they developed hearing despite not receiving any auditory stimulus in early age?
(2) Can auditory circuits be formed at any age, or is there an age in which the use of a cochlear implants will not be useful anymore?