The Economist
Reading the brain
Mind-goggling
It is now possible to scan someone’s brain and get a reasonable idea of
what is going through his mind
Oct 29th 2011 | from the print edition
* *
IF YOU think the art of mind-reading is a conjuring trick, think again.
Over the past few years, the ability to connect first monkeys and then men to
machines in ways that allow brain signals to tell those machines what to do
has improved by leaps and bounds. In the latest demonstration of this,
just published in the Public Library of Science, Bin He and his colleagues at
the University of Minnesota report that their volunteers can successfully
fly a helicopter (admittedly a virtual one, on a computer screen) through a
three-dimensional digital sky, merely by thinking about it. Signals from
electrodes taped to the scalp of such pilots provide enough information for
a computer to work out exactly what the pilot wants to do.
That is interesting and useful. Mind-reading of this sort will allow the
disabled to lead more normal lives, and the able-bodied to extend their range
of possibilities still further. But there is another kind of mind-reading,
too: determining, by scanning the brain, what someone is actually thinking
about. This sort of mind-reading is less advanced than the
machine-controlling type, but it is coming, as three recently published papers
make clear.
One is an attempt to study dreaming. A second can reconstruct a moving
image of what an observer is looking at. And a third can tell what someone is
thinking about.
In this section
* »Mind-goggling
* _Waters of change_ (http://www.economist.com/node/21534749)
* _Now count to a hundred_ (http://www.economist.com/node/21534747)
_Reprints_ (http://www.economist.com/rights)
First, dreams. To study them, Martin Dresler, of the Max Planck Institute
of Psychiatry, in Munich, and his colleagues recruited a group of what are
known as lucid dreamers. They report their results in this week’s Current
Biology.
A lucid dream is one in which the person doing the dreaming is aware that
he is dreaming, and can control his actions almost as if he were awake. Most
people have lucid dreams occasionally. A few, though, have them often—and
some have become good at manipulating the process. Dr Dresler co-opted six
self-professed practitioners of the art for his experiment. He asked them
to perform, in their dreams, a simple action whose neurological traces in a
brain scan are well understood. This action was to clench either their
right or their left hand into a fist. The test would be to see if Dr Dresler’s
brain scanner could reliably tell the difference.
Once a volunteer had dozed off and begun dreaming, he was to shift his eyes
from left to right twice, to show he was ready to begin the experiment.
(Unlike other parts of the body, which become limp in the phase of sleep
during which dreams occur, the eyes continue to twitch. Indeed, this phase is
known as rapid-eye-movement sleep.) After this signal, he clenched his left
hand in his dream ten times, and then his right hand. (His real hands, of
course, remained motionless.) He indicated the end of each set of clenches
by turning his eyes as before. A trial was deemed a success if at least four
sets of alternate clenches were performed in this way.
At first, only one participant managed to meet these exacting criteria,
though he did so on two occasions. Dr Dresler speculated that the reason was
his chosen brain scanner. He was using a functional magnetic-resonance
imaging (fMRI) machine. This is the best sort of scanner, but it makes a
terrible racket and so is not conducive to dreamy slumber. Replacing fMRI with
a
slightly less accurate technique called near-infra-red spectroscopy produced
two further successful trials involving a different volunteer.
Both techniques were able to see the brain acting to clench a volunteer’s
fist in his dream in exactly the way that it does when ordering
fist-clenching in reality. This might not seem a big deal, but it is the first
time
science has proved what was hitherto mere speculation: that the brain, when
dreaming, behaves like the brain when awake. In principle, then, it might be
possible to “read” dreams as they are happening, and thus perhaps solve
one of the great mysteries of biology: what, exactly, is dreaming for?
Though it may seem a stretch to suggest that the mind of a dreamer could be
read in this way, it is not. For the second paper of the trio, published
in Current Biology in September, shows that it is now possible to make a
surprisingly accurate reconstruction, in full motion and glorious
Technicolor, of exactly what is passing through an awake person’s mind.
This study was done by Jack Gallant of the University of California,
Berkeley. In the name of science, three members of Dr Gallant’s team each
endured two sessions of fMRI while watching assorted film trailers. The
researchers chose to experiment on themselves, rather than calling for
volunteers,
because the experiment required them to sit perfectly still in an fMRI
machine for long periods. Two hours of being bombarded with excerpts from such
treats as the remake of “The Pink Panther”, they decided, would be too
brutal a procedure to visit on innocent outsiders
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