Cochlear implants are powerful tools for people with hearing loss. Using electrodes implanted in the ear that transmit sound directly to the brain, they can give even the profoundly deaf a sense of sound.
But their success often depends on how early the implants are placed. People who are born deaf and receive implants as adults have worse outcomes than those who are fitted with the implants as children, said Andrea Warner-Czyz, an audiologist at the University of Texas at Dallas who studies development in children with hearing loss.
This is at least partly because as people with hearing loss grow older, the parts of their brain that are normally used to process sounds are reassigned to other jobs, such as visual processing. Once these reassignments occur, it is difficult to re-train them to do anything else.