- "Where am I? What place is this? What are these? I feel I should know. They're familiar, and yet unfamiliar. How did I get here? Who am I? Try to remember."
- "These last few weeks, my love for Miramanee grows stronger with each passing day. However, the dreams return every night. Fragments of memories... I can almost get hold of them, and then..." (TOS: "The Paradise Syndrome")
The Zalkonian John Doe experienced a complete memory loss after having been severely injured in a crash. His memory loss may be especially related to damages to his brain stem. (TNG: "Transfigurations")
In 2372, after his appearance and identity were changed to free him from his dishonor, Kurn (now Rodek) was told by Doctor Julian Bashir that he was suffering from a form of permanent amnesia. (DS9: "Sons of Mogh")
As, according to Dr. Crusher in Commander Riker's fantasy, memories are formed by association, it may be possible to trigger them by smells, sounds and images from the present. The idea is similar to being reminded of an old friend by listening to a song. This can be done by associational therapy, which means exposing the patient to familiar surrounding. Hoping this could stimulate the brain's neural synapses into regenerating. The success is not very likely. (TNG: "Future Imperfect")
Counseling was a long but promising way of restoring one's memory. Deanna Troi assured Geordi La Forge that they would work together to restore the memories that had been deleted and replaced by the Romulans as they brainwashed him. (TNG: "The Mind's Eye")
Telepathic memory retrieval was a process practiced by Ullian researchers. It involved the use of their telepathic abilities to retrieve and expand lost or faded memory engrams of an individual. It could be used to cure amnesia, but the memory could be altered by ill-willed Ullians in the case of a memory invasion. In 2368, Jev first invaded Deanna Trois memories causing coma and amnesia about the invasion, then when she awakened altered those memories, she asked him to retrieve, in order to blame his father Tarmin for the crime. (TNG: "Violations")
Androids could be affected by memory loss. One possible cause of amnesia was an overload of the positronic net, in such case the memories from before the overload could be recovered but none of those between the accident and the reparation. (TNG: "Thine Own Self") Data's programming possessed a memory loss fail-safe system to prevent anyone from taking advantage of him if this happened. (Star Trek Nemesis; Star Trek: Insurrection)
Dealing with amnesia
The first thing commonly done when persons were amnesic, was asking them what last thing they could remember, or if they could recall anything from the past. (TNG: "Future Imperfect", "Transfigurations", "Thine Own Self")
Persons suffering from memory loss were often given a new name when their amnesia occurred in a place where no one knew them. On Barkon IV, Data was named Jayden by two children. The two had considered calling him "Radioactive", for they mistook the inscription on the case Data carried for his actual name. (TNG: "Thine Own Self") Captain Kirk who was in a similar situation on the planet Amerind, was asked his name by the Natives and managed to remember "Ki... Ku...". He therefore was named Kirok. (TOS: "The Paradise Syndrome") The English placeholder name John Doe, commonly used in legal action, case or discussion for a party, whose true identity is unknown was used by Dr. Crusher to name a survivor of a crash. When John Doe recovered consciousness he could not remember who he was and kept this name. (TNG: "Transfigurations")
As amnesics had lost their memories of events, they were sometimes considered unreliable even for information not related to their personal memory. When Data was suffering memory loss, he was not believed on Barkon IV when he said that fire was not an element. (TNG: "Thine Own Self")
Likewise, in situations in which a faked memory loss would be convenient, amnesics were often accused of lying. While investigating on the murder of Keith Rocha, Riker assumed the suspect Aquiel Uhnari was hiding information or had conveniently forgotten details. (TNG: "Aquiel")
Amnesia could also be hard to believe for the patient, in case the loss is not complete but only for some memories or a lapse of time. The first concern of amnesics was how to recover their memory. (TNG: "Future Imperfect")
In 2367 William T. Riker was told in a holographic projection, that a virus had caused a form of amnesia, destroying all his memories from the moment he became infected to the present, supposedly sixteen years later. Riker discovered little by little details of his life in those years, without remembering anything. He then noticed things that could not be possible, for example a photograph of a holodeck creation, who was said to have been his wife. Riker then confronted everyone with the lie and the holo-images vanished. (TNG: "Future Imperfect")
Self-impose memory blockade
After a traumatic event a person could create a memory block on themselves. The deletion of any traces, log entries for instance, could be practiced. Telepaths such as the Cairn could sense the blocked memories as "a part of [the person] that is dark," meaning they could not see it. Under intense fatigue and stress the blockade could break down, particularly if a similar event was witnessed. In the case of Lwaxana Troi this led to her suffering a coma. She had effectively erased all memories of her daughter Kestra after her accidental drowning and could not stand the sudden recovery of them. Only after facing the truth and accepting those memories, could Lwaxana's psyche find peace and have her awaken. (TNG: "Dark Page")
Vulcans had the ability of drawing out memories with the help of a pyllora: a person who, during a mind meld, acted as guide or counselor within a memory experienced, to assist the subject with repressing the memory. Tuvok repressed a traumatic memory that way, when he was infected with a memory virus. (VOY: "Flashback")
A memory wipe was a medical procedure to selectively erase memories from someone, generally practiced without her or his knowledge.
- Lacunar amnesia, a psychological form of memory loss.
- Anterograde amnesia, a medical condition which prevented the sufferer from storing new memories.