Can we trust our Memories?

We depend on our memory for a sense of who we are. These are the stories we have experienced and have shaped our lives. We refer to them at all times and use the memories to help guide our actions.

Can we actually depend on them for accurate information?

A previous blog about the discovery of how memories are actually collected notes that even during the event of the memory happening the information is error prone and the data collected may be incomplete. We want the past to persist because it gives us permanence and a sense of order.

"This a long tested explanation of how memories and learning is transferred and stored in the brain. This is not a perfect system but one that has evolved over millions of years. There are many earlier parts remaining that may be of little use or even damaging . It is a complicated one and subject to many errors. It was originally developed for somewhat simple learning,where the animals are, what is dangerous, who can you trust etc. We now live in a complicated and changing world and rely more and more on this system. This storage of outside information is far from perfect yet we build all of our perceptions and consciousness on it." (discovering memory process).

We now have a whole new field of evidence that shows the memory process is further error prone when we recall our stored memories.

Memory is not a discrete packet of of data that remains constant. Just the opposite,  memories are constantly adjusted by many factors.  A big problem is we do not recognize the changes and we think of each memory as authentic. The very act of remembering changes the memory. Every time we recall an event it is altered by the circumstance we are in at that time. It is changed by our present circumstances and is warped from the our new experiences. Old memories become active as we recall new ones. You don't learn  something new without incorporating it into old information.

The brain relies on a few chemicals to record and store these events.  Each memory begins as a changed set of connections in the brain. A network of neurons are woven together within the vast electrical grid of the brain. The cells recording different parts of the memory are scattered throughout the brain and there has to be a way that they communicate to add their part to the total memory.  This firing of one group of cells causing another group (s) to become active is called Long Term Potentiation.  The method involves genes making special chemical proteins that allows this action to occur.  It is a major job to wire all of this into the brain to create a memory. Sometimes new receptors are created, increase in neurotransmitters, growth of new channels etc. This is called the consolidation phase where the memory is being hardwired  into the brain. The storage of a recent event into a long term memory requires special molecules and can take a week or more to occur.

Since new proteins are needed to create memories  (proteins are the building blocks used ) there had to be new proteins made to store memories as they were experienced.  In the late 1990s a scientist tested this by blocking the protein synthesis.  By creating fear in lab mice at the sound of a certain noise he then played this noise and at the same time injected a chemical into the brain, that stopped protein synthesis.  The memory was erased and the mice showed no signs of fear to that noise.  Conclusion-If new proteins could not be made to "build" the memory during the act of recalling the memory then it was lost.  Timing was important, the block had to occur at that actual moment the recall was taking place. 

Memories are not formed and then maintained in their original state, they are reformed every time we recall them.  The brain is not concerned about the truth of the original event of the memory but instead has a updating mechanism to allow the memories to be updated to our new situations. It wants useful information not old movies. Instead it is more like a play with subtle differences each time it is viewed.

Our present situation also will effect the memory. If you are very hungry and are recalling a event that had food there will be an emphasis on food.  Surveys show that the longer a time after an event the more changes in the memory of the event compared to the memory at the time.  The more times they had to recall a memory the more changed it became.  Also, almost none of the people involved realized that their idea of the memory had changed during the years of study. They had strong emotions that convinced them their latest memory was true even though they could then see it differed from the earlier memory. Similar examples are the unreliability of eye witnesses (even though they are allowed in court) and all autobiographies should be labeled fiction.

"History is that certainty produced at the point where the imperfections of memory meet the inadequacies of documentation".

It has also been shown that a fiction story can be presented as a memory to someone and they will then accept it as a factual experience.  People can create a believed memory by others telling them what happened in their past. They incorporate this into their own ideas of the past even though it is not true. These memories are planted by others. This is true especially of  police interviews. By asking a question " did you see the broken headlight?" instead of " did you see a broken headlight?" This can change the whole memory. 3/4 of the cases shown by DNA to be not guilty were convicted using eye witness accounts. Once a memory is planted the person now accepts this as the true memory of the past.

Since our  memories are newly formed in the act of remembering them controlling the conditions under which they are recalled can change their content.  An example is the stress syndrome many have with memories of  traumatic event.  These traumatic events occur and stress chemicals such as cortisol and norepinephrine flood the neurons and assure the memory is stored.   If these chemicals are blocked it reduces the ability to recall the event or modifies the reaction while recalling it. They may remember the event but the feelings of pain associated with it will be modified as to how they feel at the present moment of recall.  This fact may help explain why some get good results from psychotherapy. They are discussing the painful events under a comfortable and secure place and perhaps feeling better so the memory is less disturbing as it is recalled.  They are rewriting the memory under safe conditions.

A recent experiment with traumatized patients showed that when they were given the "feel good" drug ecactscy at the time of memory recall  They did recall the trauma but did not feel overwhelmed by it.  The positive feelings of the drug changed the intensity of the memory. 83% of the patients showed a decrease in symptoms after this.  Again , the conditions that we are at the time of recall changes the original memory. A similar experiment using the Beta blocker drug propranolol during the recalling of traumatic memories allowed the patient to have the recall but had much less emotional response.  This drug inhibits the production of norepinephrine a strong emotion  neurotransmitter.   After a few sessions with this the patients were able to live with the traumatic memory.

A perfect drug would be one that didn't just tamp down the emotional responses but actually erased the traumatic memory.  A protein enzyme called PKMzeta is found at the synapses where neurons connect, It stays in these regions for long times. Without this protein memory recall fades.  There is an inhibitor of the PKM  and when this is given memories fade away. PKMZeta normally opens a sensor (AMPA) on the outside of a neuron that then allows a channel to open to the inside of the cell. It allows a network of cells to suddenly communicate with each other. Every long term memory is on the verge of vanishing and the PKM allows this to not happen .  If the enzyme is blocked the memory circuit shuts down and the memory is lost.  

If there is a genetic enhancement of the production of this enzyme than the animal becomes a memory freak remembering each and every thing they come cross. Their memory performance double that of normal mice.  These mice have ongoing high levels of PKM at their synapses allowing memory channels to be open for long times.  Injecting a PKM inhibitor into the brain while a previously conditioned rat was exposed to a certain sound frequency the fear of this sound was immediately erased.  However the other sound clues were still remembered. The blockage was for a specific memory. Another experiment included eating a sugar, and then an injection of Lithium and severe nausea. The  association with the severe nausea and the sugar so they would not eat the sugar . The experiment showed that after one injection of PKM and they forgot the nausea and began eating the sugar they had previously avoided.

By asking people to remember certain things it may be possible to give a drug that would erase that specific memory.

It may be possible to erase the sensation of pain or compulsive behavior or drug addiction and other things associated with neurons and networks in the brain and in the spinal cord.

Using PKM inhibitors into the brain of drug addicted mice allowed them to erase the memory of drug use and its associations. It is thought a lot of drug use is a learned behavior that has memories to reenforce the addictions.

At this time the PKM inhibitor is a lab tool but in the future drugs could be developed that would change the memories we have.

Another way might be to implant a false memory that will help a patient. For example, certain foods make you sick and you would avoid them. A implanted memory of enjoying asparagus was able to cause people to order this at meal time. Drinking a cola while being rocked to create nausea made people avoid cola in the future. Even though they knew why they got sick they associated it with the drink.  This is called conditional memory. This implanting of memories may help in addiction and other disorders.

Sleep, and the type of sleep , is important in being able to store the memories we have gathered during the waking hours.  During certain times of sleep there is a burst of brain cell activity called "spindles". These last for a second or less in time.  This allows the memories to be stored in the hippocampus and long term memory is created.  The hippocampus is often damaged with aging (see previous blogs on memory).  A drug, zoipidern (ambien) can improve the number of spindle times and increase long term memory. It may be that drug therapy may improve our storage of memory.

When we learn something new and then sleep immediately after,  the amount of information we retain is greater then when we go through the day normally and then sleep.  Napping after learning may improve your memory. Reviewing important information just before bedtime may be beneficial to retaining new information.

We now realize , with disappointment, that our memories are not perfect and our "stories' may not be true.