when information that had been stored in long term memory can no longer be retrieved and used
Long-term memory Many neurodegenerative diseases can cause memory loss. Some of the most prevalent (and, as a consequence, most intensely researched) include Alzheimer's disease, dementia, Huntington's disease, multiple sclerosis, Parkinson's disease, and schizophrenia. None act specifically on memory; instead, memory loss is often a casualty of generalized neuronal deterioration. Currently, these illnesses are irreversible, but research into stem cells, psychopharmacology, and genetic engineering holds much promise.