Lots of healing of the brain occurs naturally over time. Sleep and good nutrition are important.
Abuse causes the brain to turn off certain parts of it's own circuitry, as though it is a giant switchboard. The parts of the brain turned off could be referred to as being in amnesia or repression.
Healing of these areas might involve remembering the painful event which caused the brain to "flip the breakers" on those circuits. This might be initially painful but it might be necessary. When these breakers are restored to normal functional levels, the brain regains it's normal function.
A wise counselor might be able to help the brain restore it's normal functional circuitry. The counselor (called a "T") can also assist in bearing the pain of reconnection.
EMDR is a therapeutic method which directly restores the open circuits.