Back to Directory

Long Term Potentiation and its Effects on Learning

What is Long Term Potentiation?

Long Term Potetiation or LTP is a process in the brain that allows for the formation of long term memories, both conscious and unconscious. LTP forms long term memories by making neurons create connections with each other. (LTD for Long Term Depression allows for the breakage of bonds that no longer serve a purpose.) LTP for this article, will focus on its work in the amygdala. Specifically, how it allows for Pavlov's conditioning

Pavlov's Conditioning

Most people know about how Pavlov accidentally trained dogs to create saliva when they heard a bell. Most people do not know most of the terms used around this experiment though. Classical Conditioning is unconsciously being trained to associate two unrelated stimuli together. This does not mean any two stimuli can be trained together, some are easier to pair than others (like nausea after eating something is easier than nausea with jumping for instance), however the important part is the association. Most conditioning requires the two stimulus to occur either directly together or have one come slightly before the other for an association to be made. The only exception is eating food with a later injection that causes nausea, which has been shown a maximum time distance of 6 hours for association to occur.

In order for association to occur there must already be a reaction. For instance with the dogs, the dogs already created Saliva in response to food. This is an Unconditioned Response. They then paired the food with the bell ring, the Conditioned Stimulus (though to be technical it's the Neutral Stimulus until the pairing is made.) Because the dogs start to associate the bell ring with recieving food, the dogs begin to salivate after hearing a bell, a Conditioned Response.

In short, Classical Conditioning happens when two unrelated stimuli become connected in thr brain. This can be many different types of stimuli, but the main principle remains the same.

The Process of LTP

Set the scene. 2 neurons, one we will focus on, and another to start the process. There are 2 receptors we are focusing on, AMPAR receptors, and NMDA receptors. Both of these receptors allow Calcium into the cell body. However, AMPAR receptors open in response to Glutamate, and NMDA receptors are blocked by Magnesium when the cell is at rest. They can only allow Calcium into the cell once that Magnesium is removed by the cell becoming more positive.

  1. A Neuron releases Glutamate into the Synaptic Cleft
  2. GLutamate binds to AMPAR receptors, allowing some Calcium into the cell
  3. The Calcium makes the cell positive enough that Magnesium stops blocking NMDA receptors
  4. NMDA recetors create a Calcium rush into the cell
  5. The Cell undergoes an Action Potential
  6. The Action Potential causes more AMPAR receptors that are already existing around the cell to be inserted into the cell wall
  7. Creb (not the Creb cycle one) goes to the nucleus of the Neuron
  8. Creb tells the nucleous to make more AMPAR receptors which are later inserted into the cell wall

What does this mean for memory?

I'm getting there. LTP is a process feeds into itself. The more times LTP happens, the easier it is for the cell to react because there are more receptors to allow Calcium into the cell body. This means after even 1 response, NMDA receptors are not necessary for the large calcium rush again. This is because the more receptors there are for a neuron to pick up on another neurons signals, the stronger the bond is between those two neurons. This is also why habits can be hard to kick.

Long vs. Short term LTP

Short term LTP is when the first AMPAR receptors are inserted into the cell wall. Long term LTP isnlcudes the whole proces right up to the newly created AMPAR receptors being inserted into the wall. Because of this, Long term LTP requires protein synthesis (receptors are a protein), while short term LTP does not.

How LTP Allows for Memory Formation

LTP creates bonds between neurons. This means it allows for associations to be made by strengthening the pathways between two objects. This is especially apparent in the Amygdala. The center for fear and agression. The Amygdala allows for two unrelated stimuli to be connected by association with fear. If going somewhere is associated with fear like the doctors office or school, before even arriving you can become agitated due to this response. This can generalize as well to other situations.

Well I'm Afraid, How do I Work with This?

While conscious fear can be worked on by adjusting your thoughts (as in Cognitive Behavioral therapy), this does not address the unconscious fear. The best way to fight the unconscious fear is to put yourself in those situations, and let those associations die. it is terifying and really hard, especially at first, but if nothing bad continues to happen to you in those situations, the preexisting bonds can be overridden with new associations. One way to do this, is to treat yourself like an anxious dog. Give yourself treats for doing scary things. Regularly challenge the idea that the things that scare you will scare you.

Unfortunately, this trainign is not permenant. You are not unlearning or forgettign the fear, you simply have new associations that do not cause fear. If you stop regularly challenging these fears, they can return and it will take a lot of work to relearn how to feel safe again. However, it will take less work as you've already built the pathways of safety. You just need to strengthen them again.