Investigators hope to study patients with 1 cochlear implant and who have had hearing preservation surgery and compare the changes in the brain of these patients with normal hearing patients by doing a scan of the brain when listening to speech. The information investigators collect may help investigators to understand how the brain learns to hear with a cochlear implant and whether it uses the same areas in the brain to listen as in normal hearing patients as well as predict which patients will do well with a cochlear implant as a very specialised operation is needed to insert the cochlear implant in to the ear and is done by very few surgeons in the country. After the operation, patients need several months of teaching to help them learn how to hear through the implant. Having a cochlear implant requires a lot of cooperation and time from the patient and if investigators could understand how the brain learns to hear with a cochlear implant and predict which patients do well and why then we may be able to avoid unnecessary procedures.