What Is Anterograde Amnesia?

Anterograde amnesia is a rare but serious form of memory loss in which a person cannot create new memories after an amnesia-inducing event. It may involve either a partial or total inability to remember new information.

While long-term memories from before the incident remain intact, people with this type of amnesia are often unable to form new memories.

Understanding Anterograde Amnesia

Anterograde amnesia is thought to involve the failure to encode (or possibly retrieve) new memories. There are also different levels of severity of anterograde amnesia.

Some people might forget a recent meal or a new phone number, for example, while others might forget what they were doing 30 seconds ago. Task difficulty can also influence memory, with more complex tasks being more difficult to remember than simpler tasks that may require less brainpower.

There are several well-known movie characters with anterograde amnesia, as the short-term memory deficit can make for some funny and suspenseful scenes. Unfortunately, the true nature of the condition can be severely debilitating.

Take the character Leonard Shelby in the movie "Memento," for instance. He keeps notes on himself to keep on track as he tries to solve a crime despite his anterograde amnesia. "Memento" may be the closest representation of what actual anterograde amnesia is like, particularly given the way in which the movie is filmed to reflect the character's memory impairments.

Memory and Amnesia

It can be helpful to understand the different types of memory that can be affected when amnesia occurs. First, we can divide memory into declarative or non-declarative.

• Declarative memory refers to the recollection of facts, whether as part of a specific event or just as unrelated information.
• Non-declarative memory is also known as procedural memory and refers to remembering how to do something, such as riding a bike or making a phone call.
  

Declarative memory can be further divided into episodic and semantic memory, which refers to whether the memory involves connections to times or places.

• Episodic memory refers to autobiographical information that includes temporal or spatial context. For example, you might remember what happened on a particular vacation.
• Semantic memory refers to factual information without any association to events that happened in your past. For example, you might remember that you own a bike, but don't remember where you bought it or where you have ridden it.

Brain Areas Involved in Memory

There are several brain areas involved in anterograde amnesia. Research tells us that it's likely that the hippocampus and nearby subcortical regions are implicated. The medial temporal lobe (MTL), basal forebrain, and fornix have all been considered as potential parts of the brain that may play a role in anterograde amnesia.

The MTL system consists of the hippocampal, perirhinal, entorhinal, and parahippocampal areas of the brain and is important for factual recall (declarative memory). The MTL is not involved in non-declarative memory.

Examples of Anterograde Amnesia

In the most famous case study of a person with anterograde amnesia, the patient known as H.M. was shown to be able to learn how to complete a maze, even though he had no memory of having completed the maze before. H.M. was suffering from anterograde amnesia due to surgery conducted to cure his epilepsy.

Another famous case study of anterograde amnesia is that of Clive Wearing, who contracted the herpes simplex virus and related complications to his brain. After this event, Wearing developed significant retrograde and anterograde amnesia. However, he retained his ability to play piano and conduct a choir.

Symptoms of Anterograde Amnesia

Because people with anterograde amnesia cannot create new memories, someone with this form of amnesia will forget things such as:

• A person they just met
• What they ate last
• New phone numbers
• Recent life changes
• Things they recently learned

A person with anterograde amnesia symptoms might remember how to make a phone call but they don't remember what they did earlier this morning. This is because declarative and non-declarative memories are thought to be stored in different areas of the brain. What's more, these individuals will often have lost the episodic part of declarative memory but not the semantic part.

Anterograde Amnesia vs. Retrograde Amnesia

Anterograde amnesia differs from retrograde amnesia in the timing of when memories are lost. People who have retrograde amnesia cannot remember things that happened before the event that caused their amnesia. But they can form new memories after the event.

Conversely, people with anterograde amnesia can often remember everything up until that event—but can't retain memories of things happening after that date. It is also possible for a person to have both of these types of amnesia, which is referred to as severe global amnesia.

Causes of Anterograde Amnesia

There are multiple potential causes of anterograde amnesia, all of which involve some sort of trauma or stress to the brain. Factors that can increase the risk of developing anterograde amnesia include:

• Drug use: Short-term anterograde amnesia may result from the use of certain drugs.
• Benzodiazepines: This type of medication has been linked to anterograde amnesia, along with the use of non-benzodiazepine sedatives such as zolpidem (Ambien).
• Traumatic brain injury: Damage to the hippocampus or surrounding area has been linked to anterograde amnesia.
• Brain inflammation: Inflammation of the brain such as encephalitis has been linked to signs of anterograde amnesia.
• Brain surgery: Patients who had parts of the brain removed, such as the MTL, have been shown to have impairments related to anterograde amnesia.
• Stroke: Stroke has been linked to anterograde amnesia.
• Alcohol blackout: A person who consumes a large amount of alcohol in a short time may experience a loss of memory for the period that they were drinking. However, after the episode, their memory functioning would return to normal.
• Chronic alcoholism: Drinking a lot over time can result in a thiamine (B1) deficiency, leading to Korsakoff syndrome, which causes significant problems in anterograde episodic memory.
• Concussion/sports injury: Concussion and sports injury to the head have been linked to anterograde amnesia.
• Electroconvulsive therapy: ECT is an effective treatment for depression. Anterograde amnesia is one observed side effect, although research suggests that this effect may be temporary or short-term.

How Is Anterograde Amnesia Diagnosed?

Diagnosing anterograde amnesia can involve using brain scan technology such as magnetic resonance imaging (MRI) and CT scan. In addition, the doctor will ask questions to better understand the memory loss, such as:

• Whether long-term or recent memory is affected
• When the memory issue started
• What could have caused the anterograde amnesia, if you know
• If there is any family history of similar problems
• Any substance use or history of seizures
• Related problems, such as confusion, language issues, or personality changes

Treatment of Anterograde Amnesia

While there is no cure for anterograde amnesia, some recovery and rehabilitation may be possible—even with permanent damage. Treatments for anterograde amnesia are primarily aimed at managing the condition. The following strategies are often used:

• Reminders such as alarms
• Journals, notes, or diaries
• Family support
• Occupational therapy

There is no FDA-approved medication treatment for amnesia. But vitamin B1 (thiamine) supplements may be used in instances where there is a vitamin deficiency. Technology tools can also be used to offer assistance, often in the form of daily planners and reminder apps.

Coping With Anterograde Amnesia

Some self-help strategies may help people living with anterograde amnesia. These might include establishing defined daily routines and finding ways to mark the passage of time.

Outline daily tasks, including things such as shopping, money management, meal preparation, and appointments. This list should be visible and accessible at any time. Break down daily tasks into smaller steps and check off progress.

People with amnesia may lose track of time and spend hours on the same task. One way to deal with this is to create a laminated chart noting what needs to be accomplished on each task and place it in a visible location.