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Where Have All The Memories Gone?

I was inspired to write this blog post by something I saw in one of my favorite TV shows, Full House. DJ Tanner was asked if she remembered someone. She’s currently 10 and was 5 years old when she last saw the person. When she said no, her dad said “Don’t worry about it DJ. You were only 5 years old.” Her younger sister then said “I’m 5! Does that mean I won’t remember any of this?” As I watched that scene in the TV show, I realized how common this situation is. Imagine this scenario. You’re at your annual family reunion looking for where the food is being served and a woman you swear you have never seen before walks up to you. She gives you a big hug and tells you she’s missed you so much. “I remember when you were just learning how to walk!” She says. “You’re so big now! Do you remember me?” You smile and nod as she gives you another hug even though you have no idea who this is. Maybe you’ve experienced this or maybe you’ve experienced something similar in a different way. When I was five years old, my father abandoned my family and me. 15 years later, I struggle to remember my memories with him or even how he looked. What happens to those memories of the random woman at the family reunion? And what happened to those memories of people we lost at a young age?

Mary Ainsworth’s Attachment Theory

The reason why these stories are so relatable is that forgetting childhood memories happens to everyone. It’s a common phenomenon called childhood amnesia. This occurs when human adults have trouble remembering anything from the ages of 0-3 and only a surface level recollection of memories before the age of 10. We see these effects mainly with declarative memories. Declarative memories can be memories of a previous experience (episodic memories) or factual information (semantic memory). The types of memories were looking into are episodic memories. Remembering your favorite Christmas memory or remembering your first vacation experience are both examples of episodic memories. Additionally, remembering what you ate for breakfast yesterday or what your mom told you when you told her about the bullying you’re experiencing at school can be an episodic memory. Compared to procedural memories, episodic memories, when remembered, can be explained. A procedural memory would be remembering how to walk, talk, use your laptop, write with a pencil, play the piano, and other things. Since procedural memories are not memories we can explain, we don’t see the effect of infantile amnesia on procedural memories. Even though we can’t remember these episodic memories, our memories from early infancy and childhood still affect us. We see this effect in how episodic memories of our parents can affect our personality traits as adults. Diana Baumrind’s Parenting Style theory actually looks into this in depth. In her theory, there are four main styles of parenting and all four styles have a different impact on the child’s wellbeing. The effect of memories on a child is also seen in Mary Ainsworth’s strange situation test. In this study, a toddler and their mom are in a room playing. The mom is then instructed to leave to see the baby’s reaction and then a stranger enters the room to also gage the baby’s reaction. Depending on the relationship between the baby and the mother, the babies react in different ways. Some babies play on their own even when the mom is in the room while others are seen clinging to their mother from the start and crying until they see their mother again. According to Mary Ainsworth, the babies that play on their own without the mother and don’t react when the mother leaves are used to being ignored by their parents based on past experiences. Both Mary Ainsworth and Diana Baumrind have different parenting style theories but they both agree that parenting styles and memories with your parents affect the child’s development and their adult characteristics. If these memories didn’t form or didn’t last, they would not have been able to affect us in adulthood. They have seemingly turned into implicit memories, which are memories Since there is proof that these memories are still affecting us, my question is do these memories still exist? If so, what’s stopping us from retrieving them?

Diana Baumrind’s Attachment Theory; Based on experiences with parents

 

While most studies performed about infantile amnesia were not done on humans, they were done on animals that have similar brain development processes and similar brain parts/functions. Most of the brain structures that exist in humans also exist in rats. In order to look into matters that concern long term memory, we have to focus on the development and functions of the hippocampus. The hippocampus plays an important role in forming memories and is also a structure that humans and rats share.

One study that can help us understand what happened to these memories a study done by Callaghan and colleagues suggests there is still a neural trace of these memories still exists even if we are unable to recall these memories (Li et al. 2014). The definition of forgetting is “failing to remember.” To remember something, you have to retrieve that memory from long term memory. Since we are unable to remember, we are indeed forgetting these memories. However, this evidence suggests that we are not forgetting because the memory no longer exists but rather because something is stopping us from retrieving that information. In other words, the memories are available to us but not accessible.

Modal Memory Model

There is a difference between availability and accessibility in memory. To understand the difference between the two, you have to understand the stages of memory according to the modal memory model; Sensory memory, short term memory, and long term memory. Sensory memory is the first stage in the memory model. In this stage, we can take in a lot of information but we will only remember what we attend to. The information we attend to moves on to short term memory. Short term memory has a short life span and also does not have a lot of space. This means you can’t store a lot of information in short term memory and you can’t keep information in short term memory for a long period of time. In order to form a long lasting memory, you use rehearsal to store the memory into long term memory. In the case of an episodic memory, reciting these memories to friends and family can be a form of rehearsal but also thinking about these memories can be a form of rehearsal. In order to use your long term memories, you have to retrieve them from long term memory. So, these memories we are unable to remember are available in our long term memory. However, they’re not accessible to us so we’re unable to retrieve the memories.
Retrieval is extremely important in the memory process. Have you ever tried to remember something you know and just can’t? It feels like it’s on the tip of your tongue but you can’t quite say it. Then someone else says it and you say “I knew it!” In those scenarios, you’ll usually have trouble retrieving the information. Retrieval can be affected by a lot of things, like the amount of attention you gave to what you are trying to recall while you were learning that material. The main question that came up and was left unanswered for Callaghan and her colleagues was why we are not able to retrieve these memories.
Research done a few years later found more evidence supporting the “memory trace” theory and also found a possible explanation for why we have trouble retrieving these memories (Travaglia et. al, 2016).

A diagram of the study done with by Travaglia and colleagues on infantile amnesia and memory retrieval. The diagram shows the training conditions of the rats and the testing conditions while also showing what they would expect the rats to do if they were able to retrieve the memories from training.

Travaglia and colleagues did a study on rats that proved an experience from early childhood was stored as a memory trace. The researchers used 17-24 day old rats and testing the likelihood that the rats would return to an area in which they were previously shocked. There were two compartments and a door separating both compartments. The first compartment is where the rat is initially placed. When the rat enters the second compartment, the door is closed and the rat is shocked on the foot. They are then tested later to see whether the rats will enter the second compartment. Some rats were trained to remember the shocking while other rats only experienced the shocking experience one time and other rats (the control) did not experience the foot shock at all. They found that when the rats were trained to remember there was a shocking would remember not to go into the second compartment but would rapidly forget (about 1 day later). They also tested whether a contextual reminder or a shock-reminder would reinstate the memory. The contextual reminder means they put the rats in the same environment they were in during the initial shocking experiment while the shock reminder meant they shocked the rats again to remind them how the shock feels instead of training them to avoid the shock again. While the contextual reminder did not, when the rats were shocked again, it reinstated the memory. They had similar results to how they acted right after they were trained.

Younger children will fall and hurt themselves because of their playful nature. However, they get back up again and continue doing the action that got them hurt in the first place, just like the rats going into the area they were shocked in previously.

In regards to how this can be compared to how human children develop, this can be compared to how children learn from their mistakes. Since toddlers and children are naturally playful, they usually find themselves in situations where they get hurt, whether they fall down at the playground or they play with something they don’t know is dangerous. Have you ever seen a toddler run around somewhere and then fall? In your mind, you’re thinking “Oh my gosh, I hope she’s okay and not hurt.” or maybe you’re thinking what my mom would think “Maybe next time she won’t run around after I told her not to.” However, the toddler dusts him or herself off, gets up like nothing happened, and continues running around. I’ve seen this happen so many times. Sometimes the child is actually hurt but after he/she is done crying, they want to go back to playing until they are reminded of the pain in some way or form. That is similar to what happens in the experiment when the young rats are shocked. As human children get older, however, contextual reminders do work to help retrieve memories. You can see this in the visual cliff experiment done by Eleanor J. Gibson. I’ve also seen this happen with my younger cousins. When he was three years old, he refused to walk on grass because of his memory of falling on grass one time. If I were to tell him about this now at age 10, he would not remember a thing. That is similar to what happens in the experiment when the young rats are shocked. If these memories of our pain were completely unavailable, we wouldn’t be able to be reminded of these memories. So, the research team determined that this was not a problem with creating long-lasting memories but rather a problem with retrieving those memories.
Another research team suggests that the high levels of neurogenesis during infancy can be the reasoning behind our poor memory recall as infants and children (Frankland and Josselyn, 2012). Through their research, they found that as neurogenesis decreases with age, the ability to form memories increased. Alberni and her colleagues found similar findings in 2017 (Alberni et al. 2017).This is very similar to the theory Travaglia and her colleagues discussed. They both found evidence that suggests the amount of development happening in the brain during infancy and childhood is the reasoning behind the lack of or hindrance in the retrieval of early memories. This makes sense since we see this problem in early childhood, where the bulk of our brain development occurs. Our brains are still functioning when we’re children but they are not at there highest capability because they’re still developing and growing everyday. This is why we struggle to retrieve those memories from early childhood.
Understanding why we can’t retrieve those memories and why these memories still effect our development is very important. We still don’t know how to retrieve those memories but we know why it happens. It also gives us some insight into just how much brain development occurs in children of a young age and its effect on processes we don’t normally see. We can see the effect of early brain development on procedural memories like speech, walking, and language comprehension because these memories are based on performance. However, it takes a lot longer to realize that the development of the brain affects explicit memories because their memories are based on recall. It’s harder to connect these memory errors to brain development when you only notice it’s effect once brain development is complete and you’re at a family reunion being greeted by someone you swear you’ve never seen before. Learning that these memories are still present and why we can’t reach them answers a lot of questions but also creates a lot more questions. So to answer the question the title of the blog asks, our memories from childhood have not gone anywhere. However, they’re harder to retrieve.

References

  1. Alberini, C. M., & Travaglia, A. (2017). Infantile amnesia: A critical period of learning to learn and remember. The Journal of Neuroscience, 37(24), 5783–5795. https://doi-org.colby.idm.oclc.org/10.1523/JNEUROSCI.0324-17.2017
  2. Travaglia, A., Bisaz, R., Sweet, E. S., Blitzer, R. D., & Alberini, C. M. (2016). Infantile amnesia reflects a developmental critical period for hippocampal learning. Nature Neuroscience, 19(9), 1225–1233. https://doi-org.colby.idm.oclc.org/10.1038/nn.4348
  3. Li, S., Callaghan, B. L., & Richardson, R. (2014). Infantile amnesia: Forgotten but not gone. Learning & Memory, 21(3), 135–139. https://doi-org.colby.idm.oclc.org/10.1101/lm.031096.113
  4. Josselyn, S. A., & Frankland, P. W. (2012). Infantile amnesia: A neurogenic hypothesis. Learning & Memory, 19(9), 423–433. https://doi-org.colby.idm.oclc.org/10.1101/lm.021311.110
  5. McLeod, S. (2018). Saul McLeod. Retrieved December 03, 2020, from https://www.simplypsychology.org/mary-ainsworth.html
  6. Diana Baumrind: Parenting Styles & Theory. (n.d.). Retrieved December 03, 2020, from https://study.com/academy/lesson/diana-baumring-parenting-styles-theory.html
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