Saturday, 30 May 2020

Closing Another Gap - Consciousness

General anesthesia has been in use for nearly 175 years, but its mechanism for causing loss of consciousness has been unknown until now. So momentous was the first use of ether that it was memorialized in this painting, "First Operation Under Ether," by Robert C. Hinckley.

Francis A. Countway Library of Medicine,
Harvard Medical School.
Solving the 175-year-old medical mystery of anesthesia’s effects | Scripps Research

Scientists may not have fully explained consciousness and how the brain monitors its own thought processes but, as this piece of research by scientists from the Scripps Institute shows, consciousness does not exist independently of the brain, as some woo-peddling charlatans claim, but is an integral, materialist function of neurophysiology.

Scripps Research News explains:

Using modern nanoscale microscopic techniques, plus clever experiments in living cells and fruit flies, the scientists show how clusters of lipids in the cell membrane serve as a missing go-between in a two-part mechanism. Temporary exposure to anesthesia causes the lipid clusters to move from an ordered state, to a disordered one, and then back again, leading to a multitude of subsequent effects that ultimately cause changes in consciousness.

The research was published, open access, last Friday, in PNAS:

Anesthetics are used every day in thousands of hospitals to induce loss of consciousness, yet scientists and the doctors who administer these compounds lack a molecular understanding for their action. The chemical properties of anesthetics suggest that they could target the plasma membrane. Here the authors show anesthetics directly target a subset of plasma membrane lipids to activate an ion channel in a two-step mechanism. Applying the mechanism, the authors mutate a fruit fly to be less sensitive to anesthetics and convert a nonanesthetic-sensitive channel into a sensitive one. These findings suggest a membrane-mediated mechanism will be an important consideration for other proteins of which direct binding of anesthetic has yet to explain conserved sensitivity to chemically diverse anesthetics.

Inhaled anesthetics are a chemically diverse collection of hydrophobic molecules that robustly activate TWIK-related K+ channels (TREK-1) and reversibly induce loss of consciousness. For 100 y, anesthetics were speculated to target cellular membranes, yet no plausible mechanism emerged to explain a membrane effect on ion channels. Here we show that inhaled anesthetics (chloroform and isoflurane) activate TREK-1 through disruption of phospholipase D2 (PLD2) localization to lipid rafts and subsequent production of signaling lipid phosphatidic acid (PA). Catalytically dead PLD2 robustly blocks anesthetic TREK-1 currents in whole-cell patch-clamp recordings. Localization of PLD2 renders the TRAAK channel sensitive, a channel that is otherwise anesthetic insensitive. General anesthetics, such as chloroform, isoflurane, diethyl ether, xenon, and propofol, disrupt lipid rafts and activate PLD2. In the whole brain of flies, anesthesia disrupts rafts and PLDnull flies resist anesthesia. Our results establish a membrane-mediated target of inhaled anesthesia and suggest PA helps set thresholds of anesthetic sensitivity in vivo.

Mahmud Arif Pavel, E. Nicholas Petersen, Hao Wang, Richard A. Lerner, Scott B. Hansen
Studies on the mechanism of general anesthesia
Proceedings of the National Academy of Sciences
May 2020, 202004259; DOI: 10.1073/pnas.2004259117

Copyright: ©2020 The authors
Published by PNAS. Open access
Reprinted under a Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

Like other gaps in scientific knowledge and understanding, the 'mystery' of consciousness is a rich feeding ground for charlatans and frauds claiming to have discovered the secret - which always turns out to be the locally-popular god of the culture to whom the fraud is marketing his books and delivering his lectures. Strangely, scientifically illiterate people often assume a gap in their knowledge and understanding is called 'God', not 'Ignorance'.

But, as this paper shows, whenever science finally closes a gap, it turns out to have a perfectly rational explanation of which magic is never part and in which immaterial entities are never needed. In this case, research has shown that by chemically disrupting ion channels in cell membranes, consciousness can be abolished. Clearly, if consciousness is the result of processes disconnected with neurophysiology, it could not be abolished this way.

Now we know how anaesthetics abolishes consciousness, there is no reason to presuppose it exists independently of the brain and can somehow survive death. The simplistic reification of consciousness in the form of a 'soul', or magic entity living inside us, is merely a primitive way to explain a basic function of neurophysiology by people who knew nothing of the subject.

The ever-shrinking God of the Gaps just got a lot smaller and frauds now have one less mystery with which to fleece their credulous dupes.

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  1. Great post and very interesting. I was never one to believe consciousness could survive without the brain that produces it.

  2. The older I get, the more I find the gap-closing discoveries concerning the mind the most enjoyable.


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