How Amnesia Works

Anterograde Amnesia

Like any medical condition, amnesia's causes and effects can be hard to pin down. For one person, it may erase a few minutes' worth of memory. For another, like Clive Wearing, a whole lifetime might disappear. So in addition to defining amnesia by the cause — brain damage or psychological trauma — doctors characterize amnesia by the type of memories lost.

Retrograde amnesia means you have trouble remembering the past. Oppositely, anterograde amnesia means you have difficulty making new memories and absorbing new information.

Anterograde amnesia, the more common of the two, is associated with injury to the hippocampus. With it, you cannot convert new sensory information into long-term memories. For instance, alcohol-induced blackouts are a type of anterograde neurological amnesia. Drinking too much alcohol blocks the neural pathways in the brain from forming new memories while intoxicated. People experiencing a blackout may talk and interact normally, but the next morning all will be blank.

Can Amnesia Erase Fear?

The film "Eternal Sunshine of the Spotless Mind" played with the idea of completely removing someone from your memory. Researchers at the Ledoux Laboratory at New York University are coming closer to making that concept a reality by learning how to erase specific emotionally charged memories in the brain. Their research focuses on our brains' responses to things that scare us. Whenever we make a memory of a fearful moment, such as a dog biting us, we make neural pathways in our brains to that memory that we retrace when we remember it. In an experiment with rats, the researchers discovered a drug that removed a neural pathway connected to a fearful memory. As the research advances, it could develop into a breakthrough therapy for people with emotional disorders, crippled by specific painful memories.

For more information, read Can I take a drug to wipe out one particular memory?