Amnesia – causes, symptoms, diagnosis, treatment, pathology

In the movie The Bourne Identity, CIA assassin
Jason Bourne tells his new acquaintance Marie Kreutz about washing up on shore, unconscious,
with two bullets in his back. He tells her that he can’t remember anything
that happened before regaining consciousness, saying
[Jason: No, I’m serious. I don’t know who I am, I don’t know where
I’m going, none of it.] Jason Bourne has amnesia which refers to lacking
memory. Now, memory can be divided into two main types. The first is implicit memory, also known as
procedural memory. Procedural memory refers the sorts of skills
you do automatically, without thinking much about it. For example, walking, riding a bike, or texting
for most teenagers–anything that has become a habit. The second type of memory is explicit memory,
also known as declarative memory. Declarative memory refers to retaining facts–the
sort of stuff you need to win a trivia contest. And these memories do take conscious effort
to retrieve. When trying to remember things like, “how
many countries start with the letter J?”, most of us need to stop and focus. It’s three by the way. You can think of procedural memory as “remembering
how,” and declarative memory as “remembering what.” When we talk about amnesia, we really mean
that some part of a person’s declarative memory, the “remembering what” is affected. Jason Bourne may not remember who he is, but
he has no problem remembering how to speak foreign languages or how to fight. Now, the process of making declarative memory
can be broken down into four stages, and each stage involves specific parts of the brain. The first stage is encoding, and it occurs
in the prefrontal cortex. Encoding begins right when you first sense
something. Say you’re tasting a strawberry. Encoding would involve classifying the strawberry
according to sweetness, size, color and texture. Think of encoding as a process of breaking
down an experience into a manageable parts for rest of the brain to use. The second stage is consolidation. Consolidation occurs in the hippocampus, which
is deep within the temporal lobes. In consolidation, the encoded bits of information
like sweetness, size, and texture of the strawberry are linked up to existing memories. Think of consolidation as solidifying the
memory. Comparing that information about the strawberry
with memories you already have, like eating a raspberry or a blueberry, helps determine
where to put that new information in your memory. When you consolidate a memory you are organizing
it in a way that will be easier to recall. The third stage is storage, and it takes place
throughout the cortex. In storage, the information that gets linked
up to existing memories get preserved or retained. Now in order to retain a memory, it has to
be edited, pared down and simplified. So less important details, like what you were
wearing or what day of the week it was when you tasted the strawberry, get edited out. That way the memory stays focused on the really
important stuff the sweetness, size, color and texture of the strawberry – the stuff
that matters. The fourth stage is retrieval, and it occurs
in the prefrontal cortex, hippocampus, and cortex. In retrieval, the brain goes through encoding,
consolidation, and storage of the memory over and over again. And with each run-through, retrieval gets
easier. If you’ve ever tried to memorize facts for
a test, you’ve gone through the process of retrieval. and you probably know that the
more you run through that information,the more likely you’ll be able to remember it
on the test. The retrieval stage protects memories from
being lost – the oldest, most retrieved memories are most resilient. Now, with amnesia, any of these four stages
can be affected. Amnesia can be categorized into two types,
according to which stages are impacted. The first type is anterograde amnesia and
it refers to an inability to form new memories – often forgetting what happened hour to hour. This can feel incredibly confusing and frustrating
for individuals as they struggle to recall recent events like who they just spoke to
or where they just came from. Anterograde amnesia is usually because of
a problem in the encoding or consolidating stage, and typically results from damage to
the prefrontal cortex or hippocampus. The second and probably most well-known type
of amnesia is retrograde amnesia, and it refers to an inability to recall old memories. This can cause anxiety for individuals with
retrograde amnesia as well as friends and family as they completely forget important
people or moments in their life. Often, individuals might create false memories,
called confabulations, or might have difficulty placing a specific memory in time. Retrograde amnesia is usually because of a
problem in the storage or retrieval stage, and typically results from damage to the cortex,
but could involve the prefrontal cortex or hippocampus as well. Both anterograde and retrograde amnesia can
be caused by acute and chronic conditions. Acute causes include traumatic head wounds
or infections. And Chronic causes include brain tumors and
neurodegenerative diseases, including dementia and alzheimer’s. Amnesia can also develop from a thiamine or
vitamin B1 deficiency, and in that setting it’s called Wernicke-Korsakoff syndrome. Amnesia can also result from medical procedures
like electroconvulsive therapy, as well as medications like benzodiazepines. Besides brain injury or illness, retrograde
amnesia can result from psychological trauma, in which case it’s termed dissociative amnesia. It’s unclear how psychological trauma causes
retrograde amnesia, but it’s thought that perhaps forgetting traumatic events is a psychological
defense against the distress they can cause. Sometimes dissociative amnesia targets a specific
memory, like a specific violent event, whereas other times it can be more general, wiping
out whole decades of memories. Sometimes dissociative amnesia is accompanied
by dissociative fugue, where a person suddenly wanders away from their home or community
without a clear memory of having done that. Diagnosis of amnesia often requires getting
a medical history from the person affected, as well as their friends and family to help
fill in possible gaps. Blood tests can detect nutritional deficiencies
or infections that impact memory. And MRI or a CT imaging may be used to detect
structural damage or abnormalities in the brain. For a diagnosis of dissociative amnesia, the
Diagnostic and Statistical Manual of Mental Disorders, or DSM-V, states that memory loss
should “not occur exclusively during the course” of dissociative fugue, meaning that
the memory loss should still be present after the episode of wandering away is over. The DSM-V further states that the amnesia
can’t be “due to any physiologic effects” of a drug, or be better explained by any other
medical condition associated with retrograde amnesia. In many cases, amnesia is temporary, and people
will regain memory so long as the cause is addressed. Occupational and cognitive therapies can assist
with the recovery process, by teaching people strategies for organizing and sorting new
information, and help those with amnesia learn to manage day-to-day life. Mobile phones and other portable digital devices
have become an important part of treatment, as they can provide people with alarms and
other reminders, as well as a way to store important information, like pictures and videos
of close friends and family. For dissociative amnesia, psychotherapy can
help a person safely process traumatic memories. Alright, so as a quick recap, anterograde
amnesia usually affects the encoding or consolidating stage of memory formation and causes a person
to be unable to form new memories. Retrograde amnesia usually affects the storage
or retrieval stage of memory formation and causes a person to be unable to recall old
memories. One type of retrograde amnesia is a dissociative
amnesia which is thought to be a psychological defense to dissociate or detach from distressing
events in the past.


  1. The video was nice.. (As always) but I have an advise: Sarah, you should give the information at a bit slower pace like Tanner Marshall tells everything at a slower pace.

  2. So is it always will be this voice from now on?
    Very frustrating since the videos are not good as they used to be.I guess previous narrators voice was big part of it and what made them enjoyable to listen to….Not anymore😑
    P.S Wernicke-Korsakoff isn't pronounced the way you said it!

  3. Tanner Marshall and Kyle Slinn has best Voice,
    But thank u Sarah for Ur hard work for us, Although few but still Illustrations were wonderful.
    A bit fast , but i Nearly understood Every thing.

  4. Great video. I hit my head at work, weeks later forgotten about it completely, until after a MRI head scan suggested a neurodegenerative issue, over 20 weeks passed before I remembered hitting my head. Can a moderate tbi cause that level of neurodegeneration in that time?

  5. Are you PROFESSIONAL's making these VIDEOS? Dr.s & THERAPIST,and MENTAL health professionals?? Dr. DjDebUsa wants to know.Subscribe & HELP me.12~2017

  6. i had Declarative amnesia after i had to undergo brain surgery. i'm still recovering information i once knew and getting back on track again.

  7. is there any physiological disorder in the prefrontal cortex, cortex and hippocampus to an anterograde amnesia patient's brain?

  8. All i remember with my life is that i hited my head on a slide and i was outside and a girl was calling me by a name all i learmed from school is gone.

  9. I was excident on 2 July last year, minor injury on left head,swollen, brain bleeding, and lost memory for a new things, like 4 days ago,1 week ago ,and sometimes I forget what I did today and yesterday ,I forget where I put keys, forgot to switch off kitchen buttons, I can't repeat and my head sick when I'm trying so hard to remember, forgot the short cut way drive home, erhghhh cannot sleep better,same dream, dizzy, nausea and I'm suffering for almost a year

  10. Anything can be deleted from memory or even added to existing memories. It's just a bit difficult for us but not difficult for angels or other races of alien life. Hence [email protected]@__#@

  11. Almost every Arabic Tv show has a character which suffers from amnesia and when i was a kid i used to wonder how the character who lost all of their memory still remember how to talk and walk and sometimes they appear to be very selective of what they can remember they remember body parts and objects like chair and bed but when it comes to people they don’t i was very frustrated lmao

  12. All I remember is the fairy god mother asking me if I want a good memory or very large penis? For the life of me I can’t remember what I chose 😳

  13. Is it Common to get Amnesia when staring at someone/something or is it just me?

    (I usually get it and its actually very annoying and uh i think i’m in Retrograde Amnesia but i’m not telling it to my Parents since my Parents might even freak out.)

    Edit: Just please be nice to reply I’m just a 12 y/o Boy.

  14. I forget a lot of things, but I think it's because of the stress… Hopefully… I can't remember my childhood (still under 18) clearly… Just a few events… I couldn't remember a conversation… And I just talked to the person… Scary…

  15. I had a head injury years ago which resulted in partial amnesia among other diagnoses from my job accident, my family and relatives became aware of this and were over protective of me while I was recovering from my injuries. The scary part about amnesia was me not remembering the group of people that I should of stayed away from who I thought were my friends, from the past before my job accident they already knew that they were not my true friends. I tried not to tell anyone about my amnesia but once the bad group of people found out, they immediately took advantage pretending to be my friends, I even invited them in my home, I was robbed. Treating doctors explained to me that flashbacks can occur as a sign that the memory is coming back. I'm no longer with those bad friends. My question is, is it possible that all of my memory will come back?

  16. I'm sorry I have retrograde amnesia it all started cuz I went back to playing this certain video game and I can remember being good at it but when I start at planes I sucked play online ran into a couple people and they reminded me started looking up YouTube videos to get better at the game then I started running into the video that I know I already watched slowly but surely my memory came back 🤔

  17. Amnesia has advantages too. I have lost a lot of my memory over 3 years. There are things i used to know but now i cannot recall.

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