SciTech

HealthTalk: Amnesia

“I’ve never seen anyone at all. I’ve never heard a word until now. I’ve never had a dream, even. Day and night are the same — blank. Precisely like death.”

Clive Wearing, a famous amnesia patient, gave this description of a severe form of amnesia, or memory loss, in a video segment by the BBC. In 1985, a rare virus infected his brain, causing damage to important brain structures. As a result of the disease, Wearing’s memory now lasts for a maximum of 30 seconds, after which he feels like he has just woken up.

One of the regions of Wearing’s brain damaged was the hippocampus. Many amnesia patients similar to Wearing have had their hippocampus damaged, which has led scientists to believe that this region is in some way responsible for forming new memories.

While Wearing can no longer remember the tastes of foods, such that every bite is a new experience, he functions no differently from a normal person in actions and speech. Before his amnesia, he was a professional musician — his skills at the piano are undiminished. His wife is the only face he recognizes, and every moment he sees her, he feels like they have reunited after decades, even though she may have just left the room for a moment.

The two forms of amnesia are retrograde and anterograde amnesia. These terms describe which memories have been erased in relation to the present time. Retrograde amnesia, according to neurology.health-cares.net, occurs when memories are removed prior to the events that caused the amnesia. Anterograde amnesia prevents new events from creating new memories. Since Wearing does not remember some events prior to the virus attack, and since he also cannot form new memories, he has both retrograde and anterograde amnesia.

It is important to appreciate how memory works when understanding amnesia. According to the book Brain and Behavior by Brian Kolb and Ian Whishaw, memory can be divided into two categories: explicit memory and implicit memory.

Explicit memory involves a conscious recollection of training, such as learning a fact. Wearing’s erased memories are explicit memories and are memories of events. Implicit memory can be thought of as unconscious memory, such as a habit or skill. Wearing’s ability to play the piano is an example of implicit memory. It is thought that implicit memory is diffusely spread across the brain, which is why destroying a region of the brain, like the damage caused by the virus Wearing contracted, will not remove the memory.

The basis of memory formation involves neurons, which can interact with other neurons via chemical or electrical signals. According to_ Discovery Health_, neurons in the brain are constantly forming new connections and removing old ones. Neurons that interact form stronger connections between each other over time. By practicing a piece of music, for example, a person causes the same neurons to fire together. Therefore, the connections between the neurons that fire when practicing are enhanced, strengthening a memory.

Memory retrieval, such as an individual remembering specific events, is not widely understood. Studies have shown increased activity in certain structures of the brains of participants who were asked to recall a list of items, but scientists are unsure of the specific roles of the structures. Furthermore, different types of recall exist, including recognition, where subjects are asked if they have seen an item on a list before, and free recall, where subjects are asked to recall the items on the list in any order.

When someone has amnesia, part of the pathway involved in forming new memories or retrieving old ones is damaged. Neuroscientists are trying to determine what the pathway is, in order to understand how memory works and how amnesia might be cured. Studying patients like Wearing, while sometimes heartbreaking, can yield great insight into the workings of the mind.