Forgetfulness that can result from brain damage or severe emotional trauma; amnesia. Pathological loss of memory can be caused by dementia, Alzheimer’s disease, alcoholism, head injury, seizures, stroke, brain surgery, ECT (electroconvulsive therapy), the use of barbiturates or other tranquilizers, and other physical events or conditions. Depending on the cause, loss of memory can occur gradually or all at once, and it may be permanent or temporary.