18 THE SCIENTIST | the-scientist.com
ANDRZEJ KRAUZENOTEBOOKpaper alluded to the procedure’s poten-
tial to treat Alzheimer’s disease and other
memory-related disorders.
“I got calls—at least two a day for
quite a long period of time—and emails:
‘My loved one is suffering from X, Y, or Z;
thank God now you can cure it. How do
we get to your lab?’” Voss says. He would
have to explain to them that this was a
scientific study, not an approved treat-
ment. “There are a million steps between
here and there, and maybe it would never
work—we don’t really know.”
But Voss’s team continues to connect
those dots, in hopes that one day the tech-
nique—the use of magnetic fields to influ-
ence activity in neurons close to the brain’s
surface—could help patients with any
number of brain disorders, and perhaps
cognitively healthy people as well.
In August, the researchers reported
that transcranial magnetic stimulation
(TMS) could moderately improve epi-
sodic memory—the ability to remember
people, events, and other things you’ve
encountered in your life (as opposed to,
s ay, how to do something)—when tar-geted at the correct part of the brain.
Voss and his colleagues were interested
in activating the hippocampus, a struc-
ture near the brain’s center that serves as
a hub of memory production and stor-
age. Because the hippocampus itself
is inaccessible by TMS—the magnetic
field falls off precipitously with depth,
explains Voss—the researchers instead
targeted areas of the brain where activity
correlated with activity in the hippocam-
pus, to try to activate the networks that
link more-superficial regions with the
deep-brain structure.
The researchers used the technique
to target the posterior-medial network
in 16 study participants following a
memory pretest. Every day for five days
in a row, subjects would come to the
lab to sit for 20 minutes and allow a
researcher to hold a figure-eight-shaped
wand to their heads. When participants
received the test treatment rather than
a sham procedure, the wand emitted
a magnetic field that “goes on and off
very quickly,” Voss says. This field “eas-
ily goes into the brain... [and] induceselectrical activity in the axons of the
cortical neurons.”
On the sixth d ay, subjects returned
to the lab to have their memory retested.
While lying in an fMRI scanner, each per-
son viewed images of, for example, an
object or an animal—some of which were
displayed within a six-panel grid, and oth-
ers that were paired with a second image, of
an environment. After a short break, partic-
ipants looked at a series of test images and,
for each one, had to report if they recog-
nized it from the first set, and if so, where it
had been displayed on the screen or which
environmental scene it was paired with.This remembering of location or pairing
information exercises an aspect of memory
known as recollection. And it is this aspect
that was improved by the magnetic stim-
ulation—a result that fits with previous
research showing that the targeted cortical-
hippocampal network is more involved in
recollection than in recognition, or sim-
ply knowing whether the object has been
previously viewed. What’s more, Voss and
his colleagues reported that better recol-
lection correlated with activity increases in
that network during memory formation,
validating the experimental approach (Sci
Adv, 4:eaar2768, 2018).
“I now have a pretty high level of confi-
dence that we’re actually doing something
specific to this targeted hippocampal net-
work... and what we’re doing to it is at
some level changing the memory-formation
information process,” Voss says. “That
to me is the most amazing part—just
that we simply can change the function
of this memory network... from outside
of the head.”
Voss’s group isn’t the only one trying
to boost memory in this noninvasive w ay.
At the University of California, Berkeley,We simply can change
the function of this memory
network... from outside
of the head.
—Joel Voss, Northwestern University