“Why can’t we remember dreams?” was the question that Doris, a thirteen years old very intelligent dame, asked me a week ago.

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Why can’t we remember dreams? What we should be asking is: Why do we remember dreams at all. We shouldn’t remember anything. We don’t use our memory natural mechanisms in our dreams so, why can we remember them?

“I don’t get it” Doris said.

“Ok. Let’s start with the basic. Let’s start with how we remember things. Do you remember what we talked about last week?”

“Sure! You talked about the hippocampus, the limbic system and the famous Mr. H.M.”.

“Do you remember what are the short-term memory and the long-term memory?”

“Yes. The short-term memories are the things we remember that happened during the day. Then, they are turned into long-term memories by the hippocampus in the limbic system inside our heads. Right? ”

“Ok. Now, there is one more kind of memory you should know about: the sensory memory”

“Wait a moment. How many memories are there? Doris asked suspiciously.

“According to psychologists, only those three: the sensory memory, short-term memory and the long-term memory”

“Ok. Go ahead”

“Thank you. The sensory memory is the one we use in our first impressions of things. Is our ability to look at something and remember how it looked with just a second of observation”

“… We recollect this information directly from our senses. There are many kinds of sensory memory depending on the sense we use. We won’t go into details but the mostly important source of information is our vision. The second in importance is our sense of hearing”.

“… Scientists believe that the short-time memory coding rely mainly in the sense of hearing. Vision is also important and the rest don’t help much”

“Ok. We know the three memories now. What has this to do with remembering dreams?”

“The important thing is to understand how we remember things. For instance: Did you have breakfast this morning?”

“Yeah, sure!”

“What do you remember from that moment?”

Doris closed her eyes.

“Hum, let me see… the smell of the hot chocolate, the taste of the bread, the voice of my mom, the cloths she was wearing, the things she told me…”

“Can you reproduce the scene in your mind?”

“Sure”

“Can you reproduce the smell of the chocolate?”

Doris closed her eyes even harder.

“I remember I liked it” Doris said; then she added: “I know what the taste of hot chocolate is. I could recognize it immediately if you let me have a sip”

“But you can’t reproduce the sensation”

“Not really, no”.

“All the things you said you remembered are sensations: data coming through your senses to be processed in your brain. But some sensations are harder to reproduce in our mind than others”

“… The main materials our brain uses to store memories are images and sounds. It uses all the information provided by the senses but the images and sounds rule. The reason they are so easy to reproduce in our minds is because they were made in our brains”

“What?! You mean our brains create the things we see?”

“Not exactly, the brain reproduces the image in our brain, inside a part of it, at the back of our head, which is called the visual cortex. The complete mechanism of how we see was discovered by Harvard scientists Hubel and Torsten in the late nineteen fifties. Have you heard of them?

“Not in my dreams”.

“Anyways, Hubel and Torsten received a Nobel prize for their discoveries. They found out how the information was processed to produce the image in our brain. The visual cortex acts as the center where signals, coming the eyes’ retina – and other parts of the brain –, are processed and the image is formed”

“Oh, I see…. Get it? I see”

“Very funny” I said, not amusedly. “The information coming from our ears as sounds is processed in another region of our brain, primarily in the temporal lobe”.

“Now, during our dreaming, our eyes are closed and light cannot excite the neurons in the retina that capture the image – the cones and the rods. The visual cortex has no information to process. Our audition system can still perceive signals but not from the dream so; the mechanisms we normally use for recalling are turned off during sleep”

“But our emotions don’t need our eyes” Doris said.

“You are right! That’s when the limbic system and the hippocampus become important. Do you remember when we talked about that?”

“Yeah, that’s why we remember nightmares better than pleasant dreams. The emotions are stronger in nightmares”

“Correct! You are a very clever girl”.

Doris remained pensive for a moment and then she asked “Do you think blind people dream?”

“That’s very good question, and is more relevant to our subject than you think. The answer is yes: blind people dream too”

“And they see images in their dreams?”

“… Yes, they do, but the quality of the images depends on how much time they could see before becoming blind. People who became blind in their adulthood – for instance: as a result of an accident – report that the images they see in their dreams don’t differ from their previous dreams”.

“… People who became blind in their early childhood refer that they often see blurred images, especially faces. People who were born blind report they only have auditory dreams”.

“Auditory dreams…? What are those?”

“Those are dreams where the images are totally absent and only sounds are perceived, just like hearing a radio. Some scientists believe those dreams are responsible for the reported improvement of the hearing sense on blind people”.

Doris thought about it for a while. “So, the mind puts the images in the dreams…” She said. She looked disappointed and I asked her why.

“In my dreams, I go to places I have never being before; places I have never even seen anywhere. I was hoping that, somehow, my mind traveled to those places, like Jaguar Shamans do. Now, you say that all the images of the dream are a result of the memory…”

“Don’t get disappointed yet. There is a missing link in this scheme that might open a door to your mind traveling desires; but, is getting late. We’ll talk about that next time”.