Sleep XIV

For me the most important bits of the book were in the last section because they really convince you to make a lifestyle change mostly by scaring you with the effects of sleep deprivation. But that doesn't mean the rest of it isn't important. They are. They are also fun to read and are mostly non-scary, because Matthew is hoping you'd be super convinced by now to sleep at least 8 hours! The section is titled Why and How we Dream.

We usually dream in the REM state, but it's not the only state of sleep we dream in. As we are falling asleep or exiting sleep, the dream like experiences you have tend to be visually or movement based. But dreams as most of us think of them - those hallucinogenic, motoric, emotional, and bizarre experiences with a rich narrative - come from REM Sleep.

MRI scanner help effectively measure localized activity of the brain in three dimensions covering upper, middle and upper brain. Scientist have placed individuals inside brain scanning machines to observe the changes that take place during REM sleep. 

During deep NREM sleep, overall metabolic activity shows a modest decrease relative to that measured from an individual while they are resting but awake. But as the individual transfers into deep rEM sleep and begins to dream, different areas of the brain light up on the scanning machine - depicting an increase in activity - upto 30% more activity. Which regions are these:

• Visuospatial Regions: at the back that enable complex perception
• Motor Cortex: instigating movement
• Hippocampus & surrounding region - which support autobiographical memory
• Deep emotional center : amygdala and cingulate cortex (ribbon like tissue sitting above the amygdala lining the inner surface of the brain) - both generating and processing emotions.

But while these regions were getting more active, certain section of the brain - the left and the right sides pf the prefrontal cortex specifically, the region close to the temples of both sides - were experiencing deactivation during REM sleep and dreaming. Nor the prefrontal cortex, Matthew says,  is like the CEO of the brain, managing rational thought and logical decision making, sending "top-down" instructions to the more primitive deep brain -enters, like those instigating emotions. This is the part that deactivates during REM and dreaming. 

"REM sleep can therefore be considered as a state characterised by strong activation in visual, motor, emotional and autobiographical memory regions of the brain, yet a relative deactivation in the regions that control rational thought"

Because of the brain scanner, scientists could analyse what's happening inside someone's brain when they were sleeping and then wake them up to obtain a report of their dream and try and match the scans to the narrative of the dreamer - for eg: less motor activity and more emotional and visual activity means less movement but strong emotional and visual scenes and objects in the dream. 

Therefore they could predict the nature of the person's dream even before obtaining a report from them.

After this Matthew shares with us an experiment conducted by a research team in Japan, led by Dr. Yukiyasu Kamitani, where they tried to pinpoint what is it exactly that we are dreaming of - scary! They worked with a group of participants who were put inside the brain scanner and then just as they were about to enter the realm of REM, they were woken up and asked to narrate their dreams. the Researchers did this many times over a few days. When they had enough data, they had a table of dream reports and the corresponding regional activity in the brain. The team then subcategorised the reports to content categories - food, nature, furniture, men, women, cars etc. Then again, the participants were asked to enter the brain scanner albeit awake this time and shown pictures of things in each of the above categories. The brain areas that lit up with each picture was them marked and used as a baseline to match what was happening in the sleeping brain. Soon the researchers knew what  you were dreaming of - a car, a house, nature, a man or a woman. Thankfully the finer details of the type of dream object were still hidden! 

But Matthew believes this data and this knowledge is important for science to start tackling issues like PTSD by mapping brain activity during sleep in people suffering from it. 

I told you these chapters weren't scary!

The next sub-section is where do dreams come from?  The Greek & Egyptians believed that dreams were sent by the gods offering divine information. Aristotle, alternatively, and very rationally for his time, said dreams come from recent waking activity. Sigmund Freud in his very famous book the interpretation of Dreams, said the origin of dreams was within the brain / mind of an individual - which was remarkable for this time and of course correct. But where he stumbled was when he believed that dreams came from unrealised wishes. According to his theory, repressed desires [latent content]  were so powerful and shocking that if they appeared in the dream undisguised, they would wake the dreamer up.  To protect the dreamer and his sleep, Freud believed there was a censor within the mind...that repressed desires could pass through and emerge disguised from the other side unrecognizable to the dreamer [manifest content]

He also believed that he could reverse engineer dreams to unravel their true meaning. Scientists have not been able to prove his theory, nor could they prove it to be false. And hence it was abandoned by science. Researchers had different Freudian psychoanalysts interpret a dream to hear very different interpretations of this same dream, with no statistical similarity between them. 

Matthew, while giving due credit to Freud for doing the best he could in the limitation of era that was in when science was at a nascent stage, says, that is not reason for accepting his theory on dreams.  Since the person's hippocampus and autobiographical regions are active during REM sleep and dreaming, dreaming might therefore contain experiences from a person's recent experiences, stuff Freud called "day residue".  But turns out it is not all that simple. In an experiment, individuals logged their daily activities they were engaged in  and their current emotional concerns. They also were asked to keep dream journals of any dreams they could recall. External judges were then called to calibrate these two logs. It turned out that there was a 1-2% overlap of the activity report & the dreams. But! 35%-55% of emotional themes and concerns that participants were having while they were awake during the day powerfully and unambiguously resurfaced in teh dream they were having at night.

All this is good - science has come a long way and we can pinpoint what the individual is dreaming about broadly and also to an extent where these dreams come from, what's the source. Matthew Walker in the next chapter takes us through what's the point of all this dreaming action - what are we achieving. 

Read on. But also get a good night's sleep and dream away! 

I'll end with a quote from Harry Potter, yes I'm a Potterhead.

It does not do to dwell on dreams and forget to live ~ J.K Rowling