https://pmc.ncbi.nlm.nih.gov/articles/PMC4912466/
- talks about REM sleep behavior disorder (RBD)
https://www.vox.com/unexplainable/400062/sleep-twitches-why
- unexplainable podcast blog post
- https://blumberg.lab.uiowa.edu/videos
- sleep twitching videos
- What do we know so far?
- Honestly not much, it's a lot of stuff that's interesting but doesn't really feel like it's worth writing down.
I need to understand the process though. So......What have I learned thus far?
https://www.sleepfoundation.org/parasomnias/hypnic-jerks
- do sleep twitches only happen as you fall asleep? Or later as well?
Things to understand to complete the topic picture:
- what is REM sleep exactly
## Off Camera Research (Day 1)
https://pmc.ncbi.nlm.nih.gov/articles/PMC3034236/ (I feel like if I can just understand this paper I will have more than enough material to keep me busy for the time frame.
- Ontogenetic hypothesis:
- The part of the brain that starts active sleep acts as the go between for the brain and the connecting musculature. This leads to brain and neuromusculature development
- This hypothesis didn't address the twitching or its role in development
- this publication reviews recent findings about elaborating on the above hypothesis
- the feedback that limb twitching produces activate the somatosensory cortex and the hippocampus
- If we can fully understand how twitches contributes to all the stuff tied to neural circuits, that should help us understand how sensory motor things develop in the littles.
- They are also hoping that twitches can be useful in monitoring the somatosensory stuff for a persons entire lifespan. Also it could help people with injuries to limbs get feeling or motor control back
It took me forever, but understanding the basics of that abstract should give me a pretty clear understanding of the topic, broad strokes.
Starting off with the **SOMATOSENSORY CORTEX** and what the heck it does:
- https://www.sciencedirect.com/topics/medicine-and-dentistry/somatosensory-cortex
- it receives "projections" through the spinal cord
- it's divided into two regions, primary and secondary
- general understood to be associated with the perception of intensity and somatosensory inputs: things you can touch or feel (hot, cold, sharp, smooth, physical touch stuff)
- both parts are activated by "itch stimuli". What does that mean?
- Not sure. I think that this just means that itching lights up parts of the somatosensory cortex that are useful for studying how it works? maybe?
- https://www.simplypsychology.org/somatosensory-cortex.html
- It processes all sensory information from your body
- There is a homunculous map of the somatosensory cortex. Each of the different mapped out portions coresponds to different areas of the body.
- there is a specific section that controls the hands, and the feet, and the lips, eyes, mouth, toes, ect.
- different parts of the brain are more sensitive, and therefor have more brain real estate dedicated to them
- damage to these parts of the brain may mean the a person might have trouble with sensations, indetifying an object with their eyes closed, tracing things onto a hand
- this is also the part of the brain responsible for the phantom limb effect
- Okay, probably enough on this topic. Let's get back to the main case
- actually, first let's look into REM sleep a little. Specifically the temporary paralysis that goes along with it because I feel like that might be relevant.
- Wait. It might not be relevant. Cause isn't the whole point that the twitches aren't related?
https://pmc.ncbi.nlm.nih.gov/articles/PMC3034236/
- back to the original publication (moving past the abstract now)
- Aparently the theory that sleep plays a functional role in learning and memory is generating controversy? I thought that was pretty much accepted as fact
- myoclonic twitching or hypnic jerks or sleep myoclonus
- what's the difference between these three things? Are they the same?
- turns out that the author of this paper is the guy that was speaking to Vox on the Unexplainable episode. That's cool!
- his CV is FORTY SIX pages long!!! What the what!?!?
- this references "complete loss of muscle tone" as one of the "striking features of sleep". What does that mean though!?
- https://stanfordhealthcare.org/medical-conditions/sleep/nighttime-sleep-behaviors/rem-behavior-disorder.html
- With REM sleep, changes occur in brain signaling which cause reduced muscle tone in many of the body's muscles; this may be called REM sleep muscle paralysis or muscle atonia
- "an individual may awaken and become quickly alert; they may be able to provide a coherent dream story."
- this quote isn't contradicting the other guy, but it is point to some things that are interesting questions I have.
- what about the people who sleep walk, or believe they are fighting someone in a dream and end up fighting their spouse in bed?
- The OG guy is saying that twitching is either unrelated to dreams or is actually what's causing them in the first place.
- REFER BACK TO THIS PUBLICATION
- they raise a lot of interesting points
- "As conspicuous as twitching is in adults, it is much more conspicuous in infants."
- here he makes the point about infants dreaming more even though they have no life experience to dream about
- newborns are in REM sleep approximately 50% of the time. Which is a little crazy
- Okay it's clearing up for me. Here's the case he's making
- The brainstem starts lighting up during sleep. As it lights up it triggers the brain activation, but also AT THE SAME TIME it triggers twitching. The dream is kindof doing it's thing, but then the brain starts to get more input from the twitching which influences the direction that the dream goes.
- But how is the twitching overcoming the loss of "muscle tone"
- he explaines the history a bit. Read it yourself if you're interested
- They wanted to see if the twitches would continue if they separated the parts of the brain that they believed were responsible for the dreaming and the twitching
- the twitching continued unaffected
- they did it to cats first, then 1 week old rats
- they believe that this is pretty conclusive evidence that twitching is not caused by dreams....
## Off Camera Research (Day 2)
Goals for today?
- Ummmmm I think I need to finish reading that publication...see if that sparks any more questions
- My question was: what's up with sleep twitches? I think?
- Don't forget to do details and thumbnail for later.
- first off read the rest of that paper though
https://pmc.ncbi.nlm.nih.gov/articles/PMC3034236/ (OG article)
### The Ontogenetic Hypothesis Elaborated
- Oh. He's saying that it makes no sense to say that active sleep can only develop the brain if it has already seen or heard things. It can develop without direct external stimulation?
- First we need to demonstrate that sensory feedback from twitching that hits the brain does actually modify the brain.
- apparently, lots of research supports the fact that sensory inputs are lesser during sleep, and especially during REM/active sleep
- hold on.
- Immediately after the above sentence he says, "The phenomenon of increased sensory threshold during sleep is widespread". Isn't that a contradiction?
- Oh nevermind, "increased sensory threshold" means it's harder to feel or perceive something. my bad.
- So he's saying, if all of the other sense are dampened, does that also mean the feedback from the twitches is also dampened?
- They got some evidence in favor of twitches being useful when there were sleeping rats that showed the organization of spinal sesorimotor circuits when the twitching limb touched a nearby object.
- So for sure, at least at the level of the spinal cord, the sensory input from twitching is not blocked
- They were also able to see that the limb twitches were lighting up coresponding regions in the somatosensory cortex
- They were able to trigger the "spindle burst" in the somatosensory cortex manually by stroking or flexing the limb in question
- ????? How is this relating to the above statement that there is an increased sensory threshhold during sleep?
- Apparently, in human infants, the muscle twitches in the single muscle that is responsible for holding up the neck was recorded, which amounted to 38,000 twiches, A DAY! Which is kindof crazy.
- they also recorded body part area in the somatosenory cortex lighting up 4,000 times in a day.
- they feel like the sheer quantity of episodes makes it hard to ignore this
- How does the activity in the brain from sleep twitching differ from awake movement?
- It might have something to do with segregating the different limbs and isolating those specific parts of the brain and muscle
- There is also a lot of "background noise" when the subject is awake vs when they are asleep most of the brain isn't doing much
I'm running out of time and I just remembered that in that podcast they talked about using twitches as way to train robot movements and I want to look into that.
- hmmm I'm not finding anything like that. I feel like if anyone was doing that it would be Boston Dynamics