Memory disorders can range from mild to severe, but they all result from some kind of neurological damage to the structures of the brain, thus hindering the storage, retention and recollection of memories.

Memory disorders can be progressive, like Alzheimer’s or Huntington’s disease, or immediate, like those resulting from a traumatic head injury. Most disorders are exacerbated by the effects of ageing, which remains the single greatest risk factor for neurodegenerative diseases in general.

Research and analysis of individual case studies of memory disorders (including cases such as “A.J.”, “H.M.”, “K.C.” and Clive Wearing) have yielded many important insights into how human memory works, although much more work remains to be done. In recent years, neuroimaging techniques such as MRI, CAT and PET scans have also aided in the analysis of how memory disorders affect the brain physiologically and neurologically

Effects of memory disorders on brain activity: Images courtesy of US National Institute on Aging