The goal is to study the neural basis of auditory processing, as experienced by young congenitally deaf users with cochlear implant (CI). CI is a neuroprosthetic device that can evoke sensation of sound in deaf people by electrical stimulation of the auditory nerve. However, CI still produces very limited auditory sensations. Speech recognition in noise, multi-talker conversation, sound localization and music appreciation remain highly problematic for most of CI users. Current knowledge on auditory processing with CI is mostly based on studies with post-lingual CI users; these subjects used to have normal hearing, but had to adapt to electrical stimulation after they became deaf. It is not clear whether current problems in auditory processing by CI are due to the crude information provided by CI devices or because post-lingual subjects can not fully exploit all auditory information provided by CI devices. Therefore, our proposal aims at understanding auditory processing and its neural basis in specific subpopulation of young congenitally deaf subjects who received their cochlear implants within their first three years of life and have no normal hearing experience. In other words, we will collect and analyze data in subjects who developed their auditory system being exposed exclusively to electric stimulation. Our general hypothesis is that malleable brain plasticity during maturational phase, driven by solely electric stimulation, leads to enhanced use of available auditory CI cues and even to new forms of auditory processing. By comparing results of pre-lingual congenitally CI deaf users with those of post-lingually CI users, we will be able to disentangle neurobiological contributions from technological aspects of current CI devices to the auditory processing. The project will contribute to basic understanding of how our ability to process sounds and speech depends on sensory experience. This knowledge will lead to improved CI designs and rehabilitative programs.