Anterograde Amnesia: Familiar faces become strangers

 

Anterograde Amnesia: Imagine yourself wandering up and down the streets not finding back home. Well, the solution is simple, looking for a taxi or ask some pedestrian for help. But what if you don’t even know the address? Or even worse, why you left your house in the first place? This article will provide you with some insights into the world of people suffering from anterograde amnesia. This type of amnesia makes them unable to retrieve conscious memories after having suffered from an accident or complications from a brain surgery.

Anterograde Amnesia

Anterograde Amnesia

Definition of Anterograde Amnesia

Anterograde Amnesia is a partial or complete inability to form new memories after an event e.g an accident. This is in contrast to retrograde amnesia, in which the affected person cannot recall memories before a detrimental incident. What all patients with anterograde amnesia have in common is a difficulty or complete inability to form long-term memory. The short-term memory cannot be stored as a permanent memory trace anymore. Anterograde amnesia is more common than retrograde amnesia, however, also cases exist where the patient has global or total amnesia in which both anterograde- and retrograde amnesia occur at the same time.

General

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Examples of Anterograde Amnesia

  • If a man is involved in a car accident and can only recall memories which have been stored before his accident
  • The movie “50 First Dates describes a similar case in which a woman lost her memory due to an accident and could not remember anything after that day
  • The movie “Memento” is about a man who lost his memory after his wife had been killed. To find the murderer, he uses tattoos and notes to identify the murderer.

Possible Causes Anterograde Amnesia

For anterograde amnesia to occur, certain brain structures are destroyed or do not properly connect to other brain structures. In the case of anterograde amnesia, the individual struggles with memory encoding and storage. Even though novel information can be processed normally, the input cannot make it to the brain structures which serve the storage of long-term memory. This inability could be caused by the following:

  • Drugs (benzodiazepines, used to treat an array of disorders, have powerful amnesiac properties as well as alcohol)
  • Brain injury or surgery (if the hippocampus or medial temporal lobe is damaged)
  • Concussions
  • A heart attack
  • Brain seizures
  • Prolonged oxygen deprivation
  • Less probable: after having suffered from a shock or when having to deal with an emotional disorder

What brain areas are affected?

When suffering from anterograde amnesia, only one brain region or a number of brain regions at the same time can be affected. Here we provide you with the deprived areas:

  • Medial Temporal Lobe Amnesia (damage to the hippocampus and/or associated structures)
    This is the best-studied brain area. The hippocampus is an important area which stores long-term memory. Simple tasks such as finding back to your own house would be impossible without this brain structure. The hippocampus is also damaged in patients with Alzheimer’s explaining the forgetfulness of the individuals suffering from this condition.
  • Basal forebrain amnesia (impairment of the medial septal-diagonal band of Broca). This structure makes direct connections with the hippocampus. It facilitates the transport of the necessary neurotransmitters towards the hippocampus thereby ensuring proper functioning of learning and memory. The most important neurotransmitters are GABA, acetylcholine, and glutamate.
  • Diencephalic amnesia (also called Wernicke-Korsakoff Syndrome) with damage to the anterior thalamic nucleus. This kind of amnesia happens mostly in alcoholics, and also here the hippocampus is affected as the three brain structures described here belong to the hippocampal system working as a unit. The difference, in this case, is patients to be alert and responsive at normal levels and the degradation of the diencephalon was seen to be caused by prolonged alcohol intoxication.

 The Hippocampus is affected in anterograde amnesia

 

Controversies related to Anterograde Amnesia

As for many disorders having a neurological cause, generalizing across the whole population by looking at the cases of a few individuals is not sufficient. This is also the case for anterograde amnesia. Thanks to novel brain imaging techniques, the neuroscientific field has made a lot of progress in understanding the general mechanism and brain areas involved in this type of amnesia. Nevertheless, more and more patients constantly manage to leave neurologists baffled. The current knowledge, therefore, proves to be insufficient mainly due to a simple reason. However before we will talk about this, we need to clarify a few terms.

When you and I think about the term “memory” mostly only one kind pop into our head. Finding the answers to questions to for instance “What is my name?”, “How are my parents called?” or “Which movie did I watch yesterday?” requires retrieving a memory stored in our hippocampus. Such memories we refer to as declarative memory and they comprise knowledge of the “knowing what” like facts and events which can be consciously recalled. However, this is only one part of memory. The other kind of memory is termed non-declarative memory which works implicitly, meaning without the contribution of consciousness. Memories of the “knowing how” fall into this kind, for instance, the ability to ride a bike or even very simple tasks like eating.

These processes are so automatized, we do not even ascribe meaning to those memory forms. Memories which do not require the input of consciousness are mostly not affected by anterograde amnesia. This fact can be verified by simple observations of amnesiac patients failing to remember events from the past, but still being perfectly able to play the piano (if it was learned prior to acquiring anterograde amnesia). The memory of an interest in anterograde amnesia is, therefore, the declarative memory, which can be subdivided into episodic- and semantic memory. The episodic memory comprises remembering autobiographical events (times, places, associated emotions…), the recalling of personal experiences. Semantic memory, on the other hand, is the recalling of factual information, concepts or ideas which we have acquired in our life. The underlying problem constitutes these two different memories. According to previous studies, both episodic and semantic memory both belong to declarative memory and can, therefore, be seen to work together. However, the case of 8-year-old patient C.L revealed that this statement is not entirely true. She was diagnosed with anterograde amnesia but only showed impairments when it came to recalling important events (where she went on vacation with her parents). Her semantic memory was not affected which suggests independent neuronal processes to be involved in episodic and semantic memories. So far, studies have been inconclusive in finding out where the differences and commonalities lay, which makes the development of treatment options especially challenging.

Anterograde Amnesia Treatment

Here is a short list of the most important treatment options, but usually anterograde amnesia resolves itself without treatment:

  • Occupational therapists: The aim is to create a connection between the intact memories prior to memory loss to the new memories which are lost with the purpose to retain the information of the latter. This is achieved via memory training.
  • Hypnosis and meditation techniques
  • Adjusted nutrition (especially if the amnesia’s cause is overconsumption of alcohol): This is an easy form of treatment which involves a simple change in your diet. Apart from reducing alcohol consumption or better, achieving complete abstinence, an essential pillar is the consumption of “brain foods” such as apples, almonds, cumin or sage.
  • Physical exercise

Tips for patients and family members

  • Keep important items such as keys or money always in the same place and try to do things always in the same order and the same manner.
  • Write information down in big letters. Use sticky notes.
  • Set alarms for simple things, e.g. when to take something out of the oven
  • Relatives should keep a visitors book so the amnesiac can check who has been in
  • As a close family member, try to keep your frustration to a minimum when the person does not remember even very important events, e.g. marriage, birthday parties or even recent deaths of relatives

Fictional Cases with Anterograde Amnesia

Movies have tried to portray anterograde amnesia through their characters. Such are the examples of Lucy Whitmore in 50 First Dates. She suffers from anterograde amnesia after a car accident and a man tries to make her fall in love with him regardless of this amnesia.

Another example is Finding Nemo and Finding Dory, and Jonathan Archer in Star Trek, Chris Pratt in The Lookout.

Probably the most famous movie that depicted anterograde amnesia was Memento, where Leonard Shelby is trying to identify the man who raped and killed his wife but through clues left by himself on his body and in Polaroid snaps. Mental health professionals have concluded that this movie is an accurate depiction of anterograde amnesia.

Patrick has completed a Master in Cognitive Neuroscience and is currently doing an online course in journalism. His aim is to inform the general public about science-related topics. He looks to achieve this by keeping his work simple, yet precise and informative for everyone.