Altered

Memory is strange its intangibility and obscurity. Physiologically, it’s simple enough: a set of specified neural connections in the brain. However, that does not explain the different types of memory that needs to be identified, where dreams are concerned.

There are various types of stored memory that comes into play when discussing dreams. Declerative memory involves conscious recall. Further, this type of memory is divided into semantic and episodic. Semantic memory is the memory of simple facts. For example, if I was asked what the capital of New York was, I’d utilize semantic memory by answering. On the other hand, episodic memory is derived from the ability to recall experiences rather than facts. For example, if I was asked what my first memory of New York was, I would describe the beautiful snow. The lateral prefrontal cortex is highly active in consolidating episodic memory. The other type of memory that is impactful on dreaming is procedural memory, which consists of recall through motor skills. This is an implicit memory that is stored within the cerebrum of the brain.

Now, it might seem a bit strange that I am writing extensively about the different types of memory. However, lately I’ve been questioning quite a bit about the role of memory in dreams. Further, I’ve been even more intrigued about the role of dreams in memory.

The impact of memory in dreams is obvious. After all, most dream theories state that dreams are simply our memories just being processed differently. That is something I have often written about in the past. But what recently grabbed my attention was the fact that perhaps it works the other way around too. Perhaps, dreams are also shaping the way we remember things in our waking hours.

A theory has been recently proposed that states that dreams actually have a crucial role in the encoding of episodic memory. A REM dream is kept -after the dream has taken place- by the hippo-campus and in the second stage of sleep, that dream is encoded throughout the sleep cycle. This might actually explain the feeling of being mistaken that an experience actually took place, whereas it was actually a dream.

Another question that ties dreams and memory together has actually troubled me for a while. Why and how are specific memories chosen to be incorporated within dreams? I often am forced to reflect back on past memories because of specific dreams and I’m simply curious to understand the cause. Why do our brains pick out certain memories, no matter what type?

After thorough research, I understand that memories impact dreams differently depending on which stage of sleep the dream has formed within. If one dreams in the NREM (non rapid eye movement) stage, episodic memories are more likely to be consolidated from the hippo-campus. However, if the dream occurs during REM sleep, the memory will be one which had provokes strong emotions or even stress. This implies that NREM dreams prove to be the ones that involve past memories of recent experiences that may have been distorted. REM dreams are ones that involved snippets of memory that has induced emotions.

Research on rodents also showed that instead of strengthening memories, sleep and dream transforms them. Neural reactivation studies by Stickgold show that recent experience is not faithfully or continuously retained.

The memories are not only altered through the cropping of the mental image but also by snipping and gluing of semantic memories to episodic ones. For example, if I were to have a memory of camping while eating marshmallows in my house, it might be altered within my dream to include the fact that I was eating my marshmallows while on a camping trip. The episodic memory of my camping trip would be meshed with the semantic memory of marshmallows and camping going together.

Further, the intertwining of memories and dreams clearly shows the magnitude of impact dreams have on waking hours.

Questions

1/ What are the most prominent kinds of memory associated with dreams?

2/ What were the specifics of the neural reactivation study? What was measured to determine the decay of the memories?

3/ Are the most recent memories consolidated within the NREM stage or REM stage?

4/ Does the altering of memories within dreams have significant negative impacts?

5/ If one’s ability to recall vanishes, will the ability to dream follow?