18 THE SCIENTIST | the-scientist.com
NOTEBOOKcated showed higher rates of false memory
for both the eyewitness and perpetrator
scenarios compared with controls.
To look for longer-term effects of
cannabis, the experimenters called the
subjects back a week later and tested them
again on the word lists, this time with a few
different dummy words thrown in. They
also re-interviewed the subjects about the
VR scenarios using a combination of old
and new questions. As before, they found
lower memory accuracy in the word-
association test in those who had been
intoxicated compared with sober partici-
pants. There were no statistically signifi-
cant differences between the groups for
the virtual reality scenarios, a result that Kloft
says may indicate memory decay over time in
all participants (PNAS, 117:4585–89, 2020).
Cognitive neuropsychopharmacologist
Manoj Doss, a postdoc at Johns Hopkins
University who was not involved in the study,
has used word association and other tasks in
his own research to demonstrate that tetrahy-
drocannabinol (THC), the main psychoactive
ingredient in cannabis, increases false mem-
ories when participants attempt to retrieve
information they’d previously learned. Doss
says that the study by Kloft and collabora-
tors is novel not only because it employs vir-
tual reality, but because it shows that both the
real-world scenarios and the word associa-
tion task can induce false memories.
For the tests administered after one
week, however, Doss notes that it’s difficult
to determine if the researchers were observ-
ing actual false memories, because partici-
pants might remember both the accurate
and the dummy information they encoun-
tered in the original experiment. In the
follow-up test, “people might say yes to the
things they’re not supposed to just because
they saw them in that first test,” says Doss.
He suggests that increasing the number of
items tested, as well as separately analyzing
the new and previously used word tests and
interview questions, could reveal a higher
incidence of false memories in the delayed
test for the participants who took cannabis.
Giovanni Marsicano, a neuroscientist at
the University of Bordeaux in France who
did not participate in the research, says
that the new results match up with find-ings he’s made in mice: animals that receive
injections of THC are more likely than con-
trols to associate unrelated stimuli—itself
a sort of false memory. His work has also
shown that a cannabinoid receptor known
as CB1 that is highly abundant in the hip-
pocampus and prefrontal cortex probably
plays a key role in the formation of these
incidental associations. One of this recep-
tor’s main jobs is to decrease the release
of neurotransmitters. Marsicano hypoth-
esizes that when the CB1 receptor is acti-
vated, neural signaling is inhibited in such
a way that the brain is less able to separate
correct from incorrect information.
Roger Pertwee, a pharmacologist at the
University of Aberdeen in the UK who was
not involved in the research, says that the
Dutch team’s results aren’t surprising given
what’s known about how cannabinoids affect
memory. Unlike endogenous cannabinoids,
which tend to selectively activate some CB
receptors and not others, compounds in can-
nabis activate all CB1 receptors at once; this
indiscriminate activation may also somehow
contribute to the formation of false memo-
ries, explains Pertwee, who works with GW
Pharmaceuticals, a company that makes pre-
scription medicines derived from cannabis.In the future, Kloft says she’s inter-
ested in looking at how people regard the
memories they form when high in order to
find out whether they “trust” those mem-
ories. “Are they confident in them, and is
there any strategy they pursue to correct
for their probably impaired memory?”
Study coauthor Elizabeth Loftus, a
cognitive psychologist and human mem-
ory expert at the University of California,
Irvine, says that the team’s study should
prompt people to think about best practices
when it comes to intoxicated witnesses. “The
law recognizes that there are vulnerable
witnesses who need extra special care and
attention when you’re interviewing them:
young children, people with mental disabil-ities, sometimes the elderly are included in
that category,” Loftus says. “Might not [peo-
ple who are high] be another example of... vulnerable witnesses where you’ve got to
be extra careful?”
—Amy Schleunes
Brain Boost
What if you could boost your brain’s
processing capabilities simply by sticking
electrodes onto your head and flipping
a switch? Berkeley, California–based
neurotechnology company Humm has
developed a device that it claims serves that
purpose. Their “bioelectric memory patch”
is designed to enhance working memory—
the type of short-term memory required to
temporarily hold and process information—
by noninvasively stimulating the brain.
In recent years, neurotechnology com-
panies have unveiled direct-to-consumer
(DTC) brain stimulation devices that prom-
ise a range of benefits, including enhancing
athletic performance, increasing concen-
tration, and reducing depression. Humm’s
memory patch, which resembles a large,
rectangular Band-Aid, is one such product.
Users can stick the device to their forehead
and toggle a switch to activate it. Electrodes
within the patch generate transcranial alter-
nating current stimulation (tACS), a method
of noninvasively zapping the brain with
oscillating waves of electricity. The com-
pany recommends 15 minutes of stimulation
to give users up to “90 minutes of boosted
learning” immediately after using the device.
The product is set for public release in 2021.
Over the last year or so, Humm has gen-
erated much excitement among investors,
consumers, and some members of the scien-
tific community. In addition to raising sev-
eral million dollars in venture capital fund-
ing, the company has drawn interest both
from academic research labs and from the
United States military. According to Humm
cofounder and CEO Iain McIntyre, the US
Air Force has ordered approximately 1,
patches to use in a study at their training
academy that is set to start later this year.
Despite the hype, however, some scien-
tists say that the jury is still out on whetherSome participants laughed and
talked to the virtual charac ters.
Others became paranoid.