Richard Semon in 1904 described that experiences cause some changes in the neurons and these changes are referred to as engram and they form memory of the particular experience in those neurons. Reactivation of these neurons occur when patient tries to recall those memories. Theodule-Armand Ribot, a French psychologist determined that memory loss affects recent memories first. Memories are lost in reverse order of their development.

• Richard Semon in 1904 described that experiences cause some changes in the neurons and these changes are referred to as engram and they form memory of the particular experience in those neurons. Reactivation of these neurons occur when patient tries to recall those memories.^[1]
• Theodule-Armand Ribot, a French psychologist determined that memory loss affects recent memories first. Memories are lost in reverse order of their development.^[2]
• In 1763, Sauvages recognized amnesia as a medical disorder.^[3]
• In early 19th century clinical description of amnesia was identified.^[3]
• Caroline Miles and Henri & Henri first described infantile amnesia in 1893 and 1895,respectively. It was further explained by Sigmund Freud in 1953.^[4]
• Alzheimer’s disease was first described in 1906 by Alois Alzheimer, a psychiatrist and a pathologist of German origin.^[5]
• Korsakoff syndrome was discovered in late 19th century by a neuropsychiatrist of russian origin named, Sergei Korsakoff.^[6]