around $5 a pop. According to McIntyre,
1,000 people have already paid between $40
and $500 for subscriptions of up to several
months’ worth of the product. Those cus-
tomers will receive the products this year, as
part of a beta test. Anyone else who is inter-
ested will need to wait until the company
officially launches its device in 2021.
—Diana KwonMemory
Munchers
Nearly seven years ago, Sheena Josse-
lyn and her husband Paul Frankland were
talking with their two-year-old daughter
and started to wonder why she could eas-
ily remember what happened over the last
day or two but couldn’t recall events that had
happened a few months before. Josselyn and
Frankland, both neuroscientists at the Hos-pital for Sick Children Research Institute
in Toronto, suspected that maybe neuro-
genesis, the creation of new neurons, could
be involved in this sort of forgetfulness.
In humans and other mammals, neuro-
genesis happens in the hippocampus, a
region of the brain involved in learning and
memory, tying the generation of new neurons
to the process of making memories. Josselyn
and Frankland knew that in infancy, the brain
makes a lot of new neurons, but that neuro-
genesis slows with age. Ye t youngsters have
more trouble making long-term memories
than adults do, a notion that doesn’t quite
jibe with the idea that the principal function
of neurogenesis is memory formation.
To test the connection between neuro-
genesis and forgetting, the researchers put
mice in a box and shocked their feet with an
electric current, then returned the animals
to their home cages and either let them stay
sedentary or had them run on a wheel, an
activity that boosts neurogenesis. Six weekslater, the researchers put the mice back in
the box where they had received the shocks.
There, the sedentary mice froze in fear,
anticipating a shock, but the mice that had
run on a wheel didn’t show signs of anxiety.
It was as if the wheel-running mice had for-
gotten they’d been shocked before (Science,
344:598–602, 2014).
Frankland says that this sort of active
erasure of memories makes sense, because
remembering everything that happens can
overload the brain; some memories, such
as what exactly we did last week, need to
be cleared out to make room for new infor-
mation. While scientists don’t know yet
exactly how the brain maintains memo-
ries, some suggest that neuronal connec-
tions play a role. Neurogenesis may help
erase memories, then, if new neurons
make their way into established brain cir-
cuits and tweak the existing network of
synapses. (See “Putting New Neurons in
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