Watching the waves

AROUND 1936 three neurologists at Harvard Medical School raided the medicine cabinet, filling their boots with morphine, barbiturates, ethers and even cobra venom. They applied those substances to (apparently) willing volunteers and cemented primitive electrodes to their scalps and earlobes. They also collared a drunk and wired him up. With pen and paper, they then recorded how the electrical signals in their volunteers’ brains changed as the drugs began to take hold.

This kind of gonzo science might meet a touch of resistance from the institutional review board if proposed today, but the work of Gibbs, Gibbs and Lennox still stands. The trio showed, without meaning to, that sedatives lower the activity of the brain through several clear stages, and that each stage is observable in that organ’s electrical readings. Their results have been refined over the years, of course, to the extent that Emery Brown, a successor of theirs at Harvard, now thinks, as he told the annual meeting of the American Association for the Advancement of Science, that statistical analysis of such electroencephalography (EEG) signals has become so good that it can be used to make anaesthesia safer and better.

The EEG of a conscious brain shows no striking features, just low-amplitude and seemingly uncorrelated ups and downs in the frequency of oscillations in the brain’s electric field. That is because the brain’s neurons are firing independently of one another as they go about the various tasks that render their owner conscious. Then (as the Harvard trio found) as the patient goes under the oscillations smooth out, deepening into a stark, uniform wave which vibrates ten times a second. The drug has tripped the neurons into singing from the same hymn sheet. Their unified song takes over from the cacophony of a conscious brain, and the patient is out.

That, Dr Brown believes, gives anaesthetists a better way to assess how deeply someone is under than measuring blood pressure and heart rate. He regularly uses brain waves clinically. In a recent operation, for example, he was able to administer a third of the normal dose of an anaesthetic called propofol to an 81-year-old cancer patient, monitoring her brain waves to ensure that she was deeply under at all times. Indeed, he thinks he may be able to automate the whole process, and has designed a machine which adjusts the dose in response to brainwave changes.

He also believes that the potential for using EEG to understand unconscious brainwaves goes beyond the operating table. Sleeping pills, for instance, do not so much aid sleep as sedate their recipient. Dr Brown thinks insomniacs might be guided into true sleep through a more precise examination of their brain activity, and the application of commensurate drugs.

Moreover, true successor to Gibbs, Gibbs and Lennox that he is, Dr Brown reveals his own gonzo side when he says his understanding of EEG readouts is such that he believes he could safely place someone into, and then retrieve him from, a “locked-in” state—one in which a person is fully aware of his surroundings, but incapable of any movement or action. When your correspondent offered himself as a test subject, only partially in jest, Dr Brown flashed an arch grin, before sombrely explaining that such an experiment would be beyond the tolerance of modern review boards, too.

Correction (February 22nd 2018): In the original version of this article we wrote that “morphine, barbiturates, ethers and even cobra venom” had been injected into (apparently) willing volunteers. Ether is inhaled, not injected. Sorry.