Brain Gateways

Where are the switches located for analgesia/anesthesia?

"There are things known and things unknown and in between are The Doors." ~ Jim Morrison.

My deep dive into consciousness started way back in early undergrad college when I joined this “new, innovative” study area called “neuroscience”. Its broad swath covered from cognitive psychology all the way to biophysical physiology. One of my first honors papers described the co-emergence two word speech with Piagetian milestones such as object permanence. And the search for a biological basis to the “Theory of Mind” followed seamlessly from my studies of philosophers.

Many years later, I wrote the creative nonfiction book, “Be the Rainbow * Bridge Heaven and Earth: How-to Manual for Integrating Alternative and Evidence-Based Medicine” as a way to consolidate a career of these pursuits. There, I describe the phenomena of placebo and nocebo and evidence of their brain underpinnings. A recent investigation further circumscribes the regions involved in this self induced pain relief. Applied transcranial direct current stimulating the right dorsal lateral prefrontal cortex enhances placebo associated analgesia and diminishes hyperalgesia from nocebo.

As a medical officer in FDA’s Review Division of Anesthesia, I worked with many investigational applications seeking ways to objectively determine the point in time where loss of consciousness occurs, allowing for deep anesthesia. Propofol is a popular agent used to induce conscious sedation. MIT investigators studied how it changes measured brain waves as it reaches this state, and may have successfully found a clear biomarker to use in clinical practice.

Data from the research shows strong increases in synchrony only in very slow frequencies (deep red color) between the thalamus and four cortical regions. Credit: Miller/Brown labs MIT Picower Institute

"What we show is that propofol dramatically changes and controls the dynamics of the brain's rhythms." Conscious functions, such as perception and cognition, depend on coordinated brain communication, in particular between the thalamus and the brain's surface regions, or cortex, in a variety of frequency bands ranging from 4 to 100 Hz. Propofol, the study shows, seems to bring coordination among the thalamus and cortical regions down to frequencies around just 1 Hz. … As much as the study explains how propofol generates unconsciousness, it also helps to explain the unified experience of consciousness, … "All the cortex has to be on the same page to produce consciousness," … "One theory about how this works is through thalamo-cortical loops that allow the cortex to synchronize. Propofol may be breaking the normal operation of those loops by hyper synchronizing them in prolonged down states. It disrupts the ability of the cortex to communicate." -Earl Miller

But where exactly is the gate of ‘conscious awareness’, if there really is one. In a new study researchers identify a key area in the cortex that appears to be that long sought-after site; the anterior insular cortex acts as a switch between low level sensory information and higher level processing, that allows only the most important information to enter conscious awareness. At the point where consciousness slips away, the anterior insular cortex deactivates and this disrupts/shifts networks in the brain that support consciousness.

Wow. Neuroscience sure has come a loooong way since my college days.

Glad I stuck with it.

REFERENCES

https://www.verywellmind.com/what-is-object-permanence-2795405

https://medicalxpress.com/news/2021-05-current-brain-dorsal-lateral-prefrontal.html

Yiheng Tu et al. Manipulating placebo analgesia and nocebo hyperalgesia by changing brain excitability, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2101273118

https://medicalxpress.com/news/2021-04-anesthesia-doesnt-simply-brain-rhythms.html

André M Bastos et al, Neural effects of propofol-induced unconsciousness and its reversal using thalamic stimulation, eLife (2021). DOI: 10.7554/eLife.60824

https://medicalxpress.com/news/2021-05-reveals-gateway-conscious-awareness.html

"Anterior insula regulates brain network transitions that gate conscious access," Cell Reports (2021). DOI: 10.1016/j.celrep.2021.109081

https://www.amazon.com/Rainbow-Bridge-Heaven-Earth-ebook/dp/B0081UEYIU/

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