Why can’t you remember being a baby?

One of my biggest fears is losing my memory. Not being able to remember adventures, experiences, feelings and moments; even faces! It just terrifies me. I think it must be one of the reasons why I am obsessed with taking photos and capturing moments in one frame forever! I’ve taken my digital camera with me everywhere for as long as I can remember to take those photos that I love and treasure – and also why picking a photographer for my wedding was a priority! And you might think I’m joking when I say I’m obsessed with taking photos but I’ve got over 20,000 on my external hard drive from uni, holidays, school, 18th birthday parties all the way back to primary school.

But how far back does it go? How far back do my photos remind me of all the things I’ve done and the places I’ve been? And when do I have to start relying on good old fashioned memories from my brain? Well, not back far enough if you ask me.

One of my earliest memories that I can remember is actually not that early at all! But I so vividly remember being allowed to stay up at my grandparents house to watch the fireworks on TV in London to celebrate the arrival of not just a new year, but of the new millennium! So I would have just turned 9 years old! From then I can remember more things about school, looking out over Grandfather Mountain in North Carolina back in 2001, when the Queen Mother died back in 2002 as I remember being distraught that the news coverage was the only thing on all the TV channels, and even laying on the sofa with my brother and sister at my Dad’s house – all of us with chicken pox! But any earlier than this and I have no recollection. In fact, all there is are albums and albums and albums full of photos like these:

Albums full of photos from birthday parties, holidays and much more. But for me that’s all they are. Photos of me. Which got me thinking…

Why can’t we remember being babies?

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The answers to this question may be tucked away in the way our memory system develops as we grow from a baby into a teenager and into adulthood. It may also explain the reason why I can’t remember that photo being taken of me at a few months old but ask me to sing any Spice Girls or S Club 7 song word for word even if I haven’t heard it in years and I’m your girl! One brain is not fully developed when we are born. Instead it continues to grow and change during this important early time in our lives. In fact, our brains continuously change throughout our lifetimes as we learn new things so the brains cells, or neurons, in our brains can make new connections. Ans as our brains develop, so does our memory. So, let’s take a wander down memory lane and take a look.

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How are memories formed?

Before we can understand why we don’t remember our childhood, we first need to know how memories are formed in the first place.

Our brains simmer with activity with different groups of neurons that are responsible for different thoughts or perceptions drifting in and out of action. Memory is the reactivation of a specific group of neurons that are formed by persistent changes in the strength of the connections between them.

These connections between neurons are called synapses and can be made stronger or weaker depending on when and how often they have been activated. Active connections tend to get stronger, whereas those that aren’t used get weaker and can eventually disappear. A connection between two neurons becomes stronger when neuron A consistently activates neuron B by sending an electrical signal through to it. Think of a line of people all holding hands. Each of them are the neurons and their hands are the synapses! If you sent a wave of your arms through that entire chain of people, that would be like sending a signal through a neuron. The more you do it, the better you become at the exercise, so your connection in your neurons becomes stronger. If someone lets go for whatever reason, the last neuron in the chain doesn’t get fired as often, and so that connection has now been weakened. It is thisΒ changing strength of existing synapses is what is crucial to memory formation.

Image result for neurons and synapses

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Do you remember?

Adults can rarely remember events from before they were three years old, and then have patchy memories when it comes to things that happened to them from the ages of three to about seven. This is a phenomenon called ‘infantile amnesia’.

So why is it so hard to remember being a baby and waddling around as a toddler? Is it simply because our first, third and seventh birthdays were a long time ago and our memories have naturally faded? Not necessarily! A 40 year old adult will usually have really strong memories of adolescence which for them happened more than 20 years ago. While for a 15 year old, it would be unlikely for them to remember their fifth birthday even though it was only 10 years ago!

It used to be thought that during our early childhood we weren’t able to make stable memories of events, and hence why we can’t recall much from that time. But it turns out that infants and small children can and do form memories. This includes implicit memories – or memories that allow us to carry out tasks without thinking about it – and explicit memories – such as those when we consciously remember an event that happened to us! But it is our ability to remember things for long periods of time that gets better throughout childhood.

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The changing brain

Neuroscientists who study memory in animals have discovered that it is not just us humans that experience infantile amnesia. Instead it seems to be common to animals whose brains, like ours, keep developing after they are born.

At birth, a human baby’s brain is only a quarter of its adult size. By the age of two, it will be three quarters of the size of an adult brain! This change in size matches up with the growth of neurons, and the testing and pruning of those connections in your brain. So what does the fact that our brains are still developing mean for memory formation?

Let’s start with the hippocampus – the part of the brain that is especially important for the formation of episodic memories – or memories of events that happened to us! While many parts of the brain keep developing and changing after we are born, the hippocampus is one of the few regions in our brains that keep producing new neurons well into adulthood, although how quickly we produce new neurons as adults is slower.

Image result for brain section staining
This is a coronal section of a brain and our hippocampus is that region of purple lines that almost look likes wings that is seen in both our left and right hand sides of our brains

Scientists think that this rapid rate of neuron production when we are babies and toddlers could contribute to our higher rate of forgetting when we were young. How? By forming new connections with memory circuits, the masses of new neurons may disrupt existing networks of already formed memories.

Scientists have tested this theory in experiments where they have changed the rate at which neurons grow in the hippocampus of young and adult mice. The young mice with slowed neuron growth had better long term memory, and interestingly the older mice with increased rates of neuron formation suffered from memory loss. Based on these results, the scientists Frankland and Josselyn showed that rapid neuron growth during early childhood disrupts the wiring in your brain that stores old memories, making them inaccessible as neuron A can’t fire neuron B!

What about our prefrontal cortex? This area of the brain right at the front just behind your forehead, and influences things like your personality and decision making for example. So, understandably, this part of your brain is also underdeveloped at birth but it also is involved in encoding your memories. So this region of your brain and it’s development when we are young could also influence our very earliest memories.

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So why can’t we remember being a baby?

Turns out that the rapid birth of many new brain cells in our young brains blocks access to our old memories!

So I am going to blame the fact that one of my earliest memories is actually quite late compared to the average on the fact that my brain was still furiously creating new brain cells for longer!

 

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What’s your earliest memory and how old were you? Or perhaps you might be one of these people with hyperthymesia where you are able to remember much more than the average person? If you want to know more about any part of memory formation or whether there is any links how quickly your brain produces new brain cells and intelligence for example, then please comment below. Let’s use our hippocampus to make some new connections to learn something new about memory πŸ™‚

Science love.

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