The short answer

Dreams are hard to remember because changes in certain neurotransmitters hamper the ability to send new information into short-term memory storage.

The long answer

There is still a lot we don't know about dreams, but one thing is for sure: dreams are notoriously difficult to recall. Also if you're someone who insists you don't dream, yes you do. You just can't remember them.

Scientists aren’t entirely sure why dreams are hard to remember, but one of the best hypotheses has to do with how our memory systems work when we’re dreaming. So let’s first dive into how researchers believe memory works when we're awake.

Here's an incredibly simple description of how memory-building works: First the cerebral cortex senses new information. Then it then sends the information to the hippocampus for short-term storage. Finally if the memory is deemed important enough, the hippocampus sends this information back to the cortex for long-term storage.

Think of the connection between the cortex and the hippocampus like a two-way road. Coming from the cortex are raw materials of memory being sent to the hippocampus for short-term storage. Coming from the hippocampus are key memories deemed important enough to require long-term storage.

So what's happening to this process while we're dreaming? Research has shown that there are fluctuations in certain neurotransmitters while we're dreaming that seem to block the connection from the cortex to the hippocampus (represented in my clipart diagram as a "Road Closed" sign).

Since the hippocampus isn't as reliably receiving new information of our dream experience, short-term memory storage is very difficult. When we wake up, it takes a few minutes for the connection back to the hippocampus to fully reactivate. So if you want to remember your dream, it's best to really focus on thinking about your dream or, better yet, writing it down immediately.

🧠 Bonus brain points

What are some reasons our brain might be designed to not remember dreams?

Dreaming is not well understand from a scientific perspective. But if a potential function of dreaming is to process past memories, it makes sense why your brain wouldn't deem it important to create new memories during this time.

Dream brain activity is very similar to daydreaming brain activity. In other words, the thoughts we have while we're dreaming are somewhat akin to what you were thinking while you were cleaning dishes last Tuesday. Can't remember where your mind wandered while scrubbing? It's the same reason our brain doesn't dependably focus on recalling dreams: it's just not that important, so why waste the energy to remember?

Another reason that may explain why we don't remember all of our dreams is because we could potentially start to confuse dreams with reality. Dreams are essentially hallucinations rooted in familiar people or activities pulled from your memory. If we recalled all of our dreams, we could end up mixing up what we said to Susan in real life versus what we said to Susan in our dream. Not remembering dreams protects our perception of reality.

By forgetting most dreams, we may be preserving the clarity of our waking life, while still benefiting from the subconscious processing that dreams provide.

Sources

Bogaty, A. (2014). What happens when you remove the hippocampus? - Sam Kean. YouTube. TED-Ed. Retrieved July 27, 2023, from https://www.youtube.com/watch?v=KkaXNvzE4pk&t=202s&ab_channel=TED-Ed.

Breus, M. (2022, December 13). How to Remember Your Dreams. Sleep Doctor. https://thesleepdoctor.com/dreams/how-to-remember-your-dreams/

Gholipour, B. (2018, May 31). Why Can’t We Remember Our Dreams? LiveScience. https://www.livescience.com/62703-why-we-forget-dreams-quickly.html

Hartmann, E. (2011, May 1). Why Do Memories of Vivid Dreams Disappear Soon After Waking Up?. Scientific American. https://www.scientificamerican.com/article/why-do-memories-of-vivid-dreams/

Obringer, L. A., & Jeffcoat, Y. (2021, October 15). How Dreams Work. HowStuffWorks Science. https://science.howstuffworks.com/life/inside-the-mind/human-brain/dream4.htm

U.S. Department of Health and Human Services. (2019, September 19). The brain may actively forget during dream sleep. National Institutes of Health. https://www.nih.gov/news-events/news-releases/brain-may-actively-forget-during-dream-sleep