Discover 3

March 2018^ DISCOVER^49

BRAD BUHR (2)

drives would become a thing of the past.

The race is on to build memristor chips

at a cost scalable to consumer computers,

and for good reason: Memristors require

perhaps 1 percent of the energy of a stan-

dard chip. And while standard computer

chips are limited to the binary code of 0s

and 1s, memristors deal in fractional units

of information — a development consid-

ered key in building computers that behave

like the human brain.

Tuszynski wasn’t familiar with mem-

ristors until he met Chua at a 2015

conference in India. “I think microtubules

are memristors,” Chua told him, reveal-

ing a longstanding interest in Hameroff ’s

work. Chua was particularly struck, he

says, when he once heard Hameroff point

out that microtubules are ubiquitous

in nature, while neurons are not. This

insight — really, a simple statement of

fact — struck Chua as crucial. “All of

these biological systems engage in a kind

of information processing,” he says. “So

how do they do it?”

He thought Hameroff had found the

answer in microtubules.

Tuszynski is very different from

Hameroff, his longtime research collabo-

rator. Stolid and practical, he’s published

more than 400 papers in peer-reviewed

publications, toiling in the earthy fields

of precision medicine and computational

biology. “Stuart, I think, is very prone to

speculation,” he says. “In many respects,

he is his own worst enemy and would be

better off if he limited himself a bit. But

Stuart is a genius. His work on microtu-

bules, prior even to ever getting involved

with Penrose, is brilliant, and it is the rea-

son I work on microtubules today.”

To test the memristor theory, Tuszynski’s

team filled a dish with microtubules,

tubulin proteins and a buffer solution,

then added electricity. Over the course of

many weeks, he found a fascinating result.

The more he replaced the buffer solution

with more microtubules, the better the

conductance.

“The conductance increased by two- or

threefold with the increased presence of

microtubules,” says Tuszynski, suggesting

the microtubules were better at conducting

energy than the buffer solution.

Further, he found the signature memris-

tor effect: When he reversed the flow of

electricity, as in an alternating current, the

efficiency of the conductance increased, as

if the microtubule had remembered the current that previ-

ously passed through it.

Tuszynski’s lab published a paper last summer on the

conductive properties of microtubules in Nature Scientific

Reports, and it is preparing a paper on microtubules as

memristors. If these results hold up, it could support

Hameroff ’s case.

THE QUANTUM REALM

The last morning of the conference in Tucson, Hameroff

slowly rolls a suitcase out to the lobby and plops down in

a lounge chair to handle a few more administrative duties.

“I think it went well,” he says. “People are telling me they

enjoyed it. I organized this, so that could be bullshit. But I

think they mean it.”

This being a Hameroff production, there was a fair

amount of combat. Chalmers accused Hameroff of taking

the conference too far into the quantum realm.

Hameroff has a ready response. He was able to include

so many quantum-oriented conference sessions, he says,

because quantum biology is a growing field.

Of course, none of this is to say that Hameroff wins this

debate. He has yet to reframe fringe as frontier, and he may

never. But in this moment, with scientific success being in

part a simple function of math — is an idea gaining or los-

ing adherents? — he is clearly on the way up, and that is

perhaps never so apparent as when he gets up to leave.

With one hand on the handle to his luggage, he is imme-

diately stopped. Hudetz, the anesthesiologist who was once

dismissive of Hameroff, walks over to say hello. He tells his

host, with seeming earnestness, “It was a very good confer-

ence, Stuart. I had a great time.”

Hameroff thanks him. They banter a bit, and Hudetz

turns to walk away. “You know,” says Hameroff, stopping

him, “you ought to do some research on microtubules.”

“It’s funny you should say that,” Hudetz replies. “Because

we’re talking about it in my lab. There’s some interest. We

might just do that.”^ D

Steve Volk is a contributing editor at Discover.

Leon Chua, left, first

theorized about

circuit elements

called memristors,

which could be

like resistors with

memory. Jack

Tuszynski, right,

thinks microtubules

could be memristors.