Short Term Memory Loss : Anterograde Amnesia

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Man with question mark in his brain

 

At the nanoscopic level, eventually the human body is made up of little atoms and molecules which constantly get replaced every second. In fact after every 10 years or so, you are a complete new you! With all your atoms and molecules changed, you have nothing matterly common between you of now and you of 10 years past. But, you are still the same you. Still living in the same identity. And memories are what that make it possible!

But what if I say that you can’t create new memories anymore? That you’ll forget everything forever…literally everything you’re seeing, feeling, listening all will be gone within a few hours?

I’m talking about the Short Term Memory Loss, scientifically named as Anterograde Amnesia. It refers to the loss of memory after a particular incident. More precisely, the inability to transfer the memory from your short term to long term. The memories before the incident remain intact. The patients’ memory could be of a few minutes or a few hours but it can’t exceed a day! And after that, the brain simply factory resets itself to the time just before the trauma which caused the damage. The patient may not remember what he had for the breakfast or even if he had the breakfast or not. Anterograde Amnesia, though rare, has attracted a lot of attention of medical researchers as well as the movie-makers because of its mysterious nature.

forgetting

It is observed that though the people suffering from STML can’t make the factual memory, or the memory of the events, but, they can learn a skill! For example, teach them how to ride a bicycle in case they don’t know, and give them a bicycle the very next day. They will have absolutely no memory of the learning sessions of the last day, they will also hesitate to ride, but once on the bicycle, they’ll be able to ride without falling. Strange! You know how to do that, but you don’t know how you know that!

Now, let us see the different kinds of memories we have. Broadly memories are of two types: Short Term Memory (STM) and Long Term Memory (LTM). STM is everything that happened today, while LTM is everything that happened except today. When you sleep, your STM gets transferred to the LTM. Further, LTM is also categorized into 3 types:

Episodic Memory: The one which includes the autobiography part. Like who am I? Who are the people I meet? What was I doing today at 6 pm?

Procedural Memory: These are all the how-to stuffs. For example, how to write, how to drive a car, how to make paper planes etc. Memories that define a rule.

Semantic Memory: In simple words, the facts! The facts about the world. Like New Delhi is the capital city of India, and other stuff like that.

Anterograde amnesia makes the people unable to form new episodic memories, but they can still make procedural and semantic memories!

For the sake of understanding, formation of a new memory could be seen as the formation of a connection between two different neurons. Neurons are nothing but the basic building blocks of the brain. Long term memories have stronger connections between the neurons while the short term memories have weaker connections. These connections slowly get attenuated with time. Repetitions make the connections stronger. Now, these connections are made through chemicals known as neurotransmitters. One neuron releases it, while the in the vicinity of it receive it and whoa! We just transferred an information!

 

Causes of Anterograde Amnesia:

  • Use of Benzodiazepine (BZD) drugs: They affect almost every part of the brain function. BZD drugs enhance the action of GABA (abbreviated name for another big molecule). This GABA is assigned the function of reducing the signals between the neurons. So, consumption of BZD in higher amounts may reduce the neuronic connections to such an extent that we may not recover it at all. And since the connections for short term memories are already weak, they easily get cleared. There! We just lost the memory!
  • Brain Injury. Especially the ones which injure the hippocampus part of the brain. Everything that we observe first goes to the short term memory. With time, depending upon the frequency or attention of observations, they get transferred to the long term memory. Now this hippocampus is kind of gate through which the information from the short term memory passes to the long term memory. If it’s damaged, no new memories could be formed!
  • Usual body illness too can cause anterograde amnesia if they’re potentially harmful for the brain tissues.
  • Brain Tumours. Especially in the medial temporal lobe of the brain.
  • Alcohol Consumption. Yeah, crossing limits with any sort of stuff is quite harmful. High amounts of alcohol in a short span of time inhibits the transfer of information from the short term to the long term memory.
  • Aging
  • Alzheimer’s disease

 

At present, medical science has no pin-point cure to the short term memory loss. However, improvements might be seen. Memory exercises are always beneficial in such cases. Sometimes, therapy might help in regaining the brain-functionality while sometimes the disease might be permanently irreversible. In most of the cases, full recovery is not possible, yet the patients could be taught upon how to deal with the disease. It could be very stressful for the family members as well. Making memory notes, keeping journals, keeping to-do lists: these could help a bit, but eventually it’s the love and support of the family members that’ll keep the patient going!

loss_of_memory

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