How to tell if a brain is awake: EEG may not always be a reliable reflection of consciousness:
Remarkably, scientists are still debating just how to reliably determine whether someone is conscious. This question is of great practical importance when making medical decisions about anesthesia or treating patients in vegetative state or coma.
Currently, researchers rely on various measurements from an electroencephalogram, or EEG, to assess level of consciousness in the brain. A Michigan Medicine team was able to demonstrate, using rats, that the EEG doesn't always track with being awake.
"EEG doesn't necessarily correlate with behavior," says Dinesh Pal, Ph.D., assistant professor of anesthesiology at the U-M Medical School. "We are raising more questions and asking that people are more cautious when interpreting EEG data."
Under anesthesia, an EEG will display a sort of signature of unconsciousness: reduced brain connectivity; increased slow waves, which are also associated with deep sleep, vegetative state and coma; and less complexity or less change in brain activity over time.
Building on data from a 2018 study, Pal and his team wanted to see what happened to these measures when a brain was awakened under anesthesia. To do so, they targeted an area of the brain called the medial prefrontal cortex, which has been shown to play a role in attention, self-processing and coordinating consciousness.
Using a drug in that part of the brain that mimics the activity of neurotransmitter acetylcholine, the team was able to rouse some of the rats so that they were up and moving around despite the fact that they were receiving continuous anesthesia. Using the same drug in the back of the brain did not awaken the rats. So, both groups of rats had anesthesia in the brain but only one group "woke up."
Then, "we took the EEG data and looked at those factors that have been considered correlates of wakefulness. We figured if the animals were waking up, even while still exposed to anesthesia, then these factors should also come back up. However, despite wakeful behavior, the EEGs were the same in the moving rats and the non-moving anesthetized rats," says Pal.
(Score: 4, Interesting) by maxwell demon on Friday January 03 2020, @07:01AM (1 child)
How did they determine that the rats are really awake, and not doing the rat equivalent of sleepwalking?
The Tao of math: The numbers you can count are not the real numbers.
(Score: 3, Insightful) by c0lo on Friday January 03 2020, @08:40AM
The salmon told them [prefrontal.org] - linked is original, open access research. As PDF.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by DannyB on Friday January 03 2020, @02:55PM
Announce: It's 5 PM! Time to wake up and go home!
See how many responses you get.
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.
(Score: 2) by JoeMerchant on Friday January 03 2020, @04:39PM
EEG is taken with surface electrodes, usually without shaving scalp hair, placed at approximate locations outside the skull. Nerves and muscles outside the skull also produce electrical signals and due to their proximity to the electrodes these signals are many times stronger than the desired signals coming from the brain. Within the brain, activity in the surface brain matter effectively masks activity deeper inside.
"Signs of wakefulness" are strongest in the electrodes placed over the eyes - and neuroscientists who aren't trying to hold up an emerald curtain will confess that these signs come mostly from eyelid and eye movement muscles. It doesn't invalidate the correlation - activity in those muscles is indeed correlated with wakefulness, but that's mostly EMG you're interpreting, not the upstream brain activity that ultimately triggers it.
Some 20-25 years ago, we undertook ANOVA on various physiological signs and attempted to correlate things like EKG, heart rate variability, respiratory rate, depth, etc. and basically the kitchen sink, too... whatever we could get our hands on to line up with EEG sleep staging. We had simultaneous EEG, collected by a single practicing EEG sleep technician (important to reduce variability due to electrode placement choices) scored by 6 board certified presently practicing neurologists and attempted to find clear signs of stage I, II, III, IV sleep in the non-EEG physiological data. It was an impossible task because the neurologists didn't even agree among themselves about how to interpret the EEG into sleep stages. All we could get with any degree of reliability (from the EEG alone) was wakefulness vs deep sleep, the stages inbetween might as well have been randomly assigned. Inasmuch as the neurologists agreed among themselves, we could get the same data from non-EEG physiologic signs - but... without that magic sleep stage number (which is total B.S.) nobody cares, not impressed. Gold plated straw man placed on a pedestal so high that noone will ever knock it off.
🌻🌻 [google.com]