This document proposes using transcranial alternating current stimulation (tACS) between 12-15 Hz on the thalamocortical regions of the brain to artificially induce sleep spindles during sleep. Sleep spindles have been linked to declarative memory consolidation. The study would test if such stimulation can enhance memory retention by having participants memorize word pairs and testing recall after sleep with or without spindle induction. Recent technological advances have made it possible to artificially generate brain states and processes like sleep spindles, offering an opportunity to explore their role in memory.

1.
Declarative
Memory
and
tACS:
Inducing
Sleep
Spindles.
A
Proposal
Zac
Shaiken
(ID:5882389)
PSYC
211
Lab
2007
Demonstrator:
Kahla
Redman
1423
words

2.
Abstract
The
relationship
between
sleep
and
memory
is
well
documented.
Specifically,
the
relationship
between
thalamacortical
oscillations
(sleep
spindles,
which
occur
in
stage-­‐2
sleep
and
slow
wave
sleep)
and
declarative
memory
is
well
documented.
Until
recently,
artificially
generating
brain
states
and
events
was
thought
to
be
possible
but
the
technology
was
not
adequate
to
do
so.
However,
recent
technological
breakthroughs
have
proven
that
the
technology
now
exists
to
generate
brain
states.
The
proposed
study
would
attempt
to
generate
sleep
spindles
by
using
transcranial
alternating
current
stimulation
between
12
and
15
Hz
on
the
thalamacortical
regions
of
the
brain.
Using
a
paired-­‐associates
wordlist,
participants
will
be
tested
to
see
if
such
stimulation
can
be
used
to
enhance
declarative
memory.

3.
Review
Have
you
ever
wondered
why
we
sleep?
An
individual
who
sleeps
eight
hours
each
night
and
lives
to
be
80
years
old
will
spend
close
to
27
of
those
years
asleep.
One
of
the
many
functions
of
sleep
is
the
consolidation
and
encoding
of
memories
(Schabus,
2004).
Specifically,
sleep
spindles
(thalamacortical
oscillations
occurring
primarily
during
stage-­‐2
sleep
and
slow
wave
sleep)
have
been
linked
to
the
consolidation
and
encoding
of
declarative
memories
(Schabus
et
al.,
2004).
The
Schabus
et
al.
(2004)
study
involved
giving
participants
a
paired
word
list
to
memorize
and
asking
them
to
recall
the
pairs
after
sleep.
Participants
who
had
more
sleep
spindles
tended
to
recall
the
paired
words
better
than
participants
who
had
less
sleep
spindles.
This
implies
a
relationship
between
sleep
spindles
and
declarative
memory
consolidation.
However,
it
remains
unknown
whether
sleep
spindles
are
a
result
of
thalamacoritcal
encoding
and
consolidation,
or
are
the
catalyst.
Additionally,
spindles
occurring
during
slow
wave
sleep
(SWS)
seem
to
be
especially
important
to
declarative
memory
retention.
Cox,
Hofman,
and
Talamini
(2012)
examined
this
phenomenon
in
subjects
who
watched
a
movie
and
were
asked
to
answer
questions
about
the
movie.
They
found
that
sleep
spindle
density
in
SWS
was
strongly
and
positively
correlated
to
declarative
memory
and
the
associated
recall.
In
other
words,
subjects
who
experienced
dense
sleep
spindles
in

4. SWS
were
more
likely
to
correctly
answer
questions
about
the
film
than
subjects
who
did
not
experience
sleep
spindles
in
SWS.
Furthermore,
a
study
in
elderly
women
found
that
the
number
of
sleep
spindles
in
stage-­‐2
sleep
was
positively
correlated
with
declarative
memory
performance
(Seeck-­‐Hirschner
et
al.,
2012).
In
this
study,
elderly
women
were
asked
to
draw
a
figure
using
a
template.
After
sleep,
they
were
asked
to
reproduce
the
drawing.
The
number
of
discrepancies
between
the
two
drawings
was
negatively
correlated
with
the
number
of
sleep
spindles
that
the
participant
experienced
during
the
night.
It
is
important
to
note
that
this
study
emphasizes
the
importance
of
the
number
of
sleep
spindles
in
stage-­‐2
sleep
as
opposed
to
SWS.
This
can
be
attributed
to
age.
As
humans
age,
the
time
spent
in
SWS
decreases.
Some
studies
suggest
that
this
decrease
is
tied
to
age-­‐related
reductions
in
cognitive
performance
and
abilities—such
as
memory
(Tisserand
&
Jolies,
2003).
The
evidence
that
suggests
the
importance
of
sleep
spindles
to
declarative
memory
inspired
the
central
research
question
for
the
current
study:
is
it
possible
to
artificially
induce
sleep
spindles
in
a
way
that
catalyzes
or
promotes
the
consolidation
of
declarative
memories?
Until
relatively
recently,
the
idea
of
artificially
inducing
brain
processes
was
reserved
for
the
realm
of
science
fiction.
However,
new
research
has
opened
the
door
to
this
previously
latent
ability.
In
fact,
in
a
groundbreaking
study
by
Voss
et
al.
(2014),
researchers
used
current
stimulation
to
induce
lucid
dreaming
in
subjects
who
were
in
REM
sleep.
Using
a
method
called
transcranial
altering
current
stimulation
(tACS),
researchers
were
able
to
artificially
produce
a
gamma
frequency
that
closely
resembled
the

5. frequency
produced
during
a
lucid
dream.
Neuronal
synchrony
occurred,
inducing
self-­‐awareness
and
other
elements
of
lucidity
into
the
subject’s
dream.
In
two
studies,
participants
were
given
direct
stimulation
at
a
low
frequency
to
enhance
SWS.
Participants
were
given
a
paired
wordlist
to
memorize
before
the
experimental
group
received
direct
stimulation
early
in
sleep.
They
found
that
direct
transcranial
stimulation
enhanced
SWS,
promoted
sleep
spindles,
and
resulted
in
enhanced
performances
on
the
recall
task
the
next
day
(Marshall
et
al.,
2006;
2011).
These
studies
show
that
transcranial
stimulation
can
be
viable
to
enhancing
memory
through
neuronal
synchrony.
Although
studies
have
been
conducted
that
enhance
various
stages
of
sleep,
no
study
thus
far
has
specifically
attempted
to
generate
sleep
spindles
(as
opposed
to
attempting
to
induce
or
prolong
a
specific
stage
of
sleep).
Instead
of
creating
the
circumstances
during
which
these
oscilliatory
events
occur,
the
current
study
attempts
to
generate
the
oscilliatory
events
themselves.
In
order
to
understand
how
tACS
can
catalyze
sleep
spindles,
it
is
important
to
have
an
intimate
understanding
of
what
sleep
spindles
are.
Sleep
spindles
are
thalamacortical
bursts
that
occur
roughly
every
3-­‐10
seconds
and
last
for
around
1-­‐
3
seconds.
They
are
theta
waves
and
are
roughly
between
12
and
15
Hz.
As
was
alluded
to
earlier,
the
precise
function
of
sleep
spindles
is
unknown,
however,
studies
suggest
that
they
functionally
“preserve
sleep
by
inhibiting
sensory
input”
(Schabus,
2004;
Yamadori,
1971).
In
conclusion,
sleep
spindles
are
thalamacortical
bursts
that
occur
during
stage-­‐2
sleep
and
SWS
and
are
correlated
with
the
consolidation
and
encoding
of

6. declarative
memories
(Schabus,
2004;
Schabus
et
al.,
2004;
Cox
et
al.,
2012;
Seeck-­‐
Hirschner,
2012;
Marshall
et
al.,
2006;
2011).
Until
recently,
artificially
generating
brain
states
was
theoretically
possible
but
the
technology
was
not
advanced
enough
to
make
this
a
reality.
However,
studies
have
been
conducted
that
enhanced
stage-­‐2
sleep
and
SWS,
using
direct
transcranial
stimulation,
thereby
creating
the
conditions
necessary
for
sleep
spindles
to
occur
(Marshall
et
al.,
2006;
2011).
Additionally,
Voss
et
al.
(2014)
used
tACS
to
induce
lucidity
in
dreams,
which
is
indicative
of
the
immense
technological
advancements
that
have
occurred
in
this
field.
Proposal
It
has
been
suggested
that
tACS
can
induce
brain
states
during
sleep
through
neuronal
synchrony.
We
want
to
give
subjects
a
declarative
memory
test,
expose
the
experimental
group
to
either
tACS
during
stage-­‐2
sleep
or
SWS,
then
test
their
recall.
We
hypothesize
that
individuals
who
are
exposed
to
tACS
between
12
and
15
Hz
during
stage-­‐2
sleep
will
demonstrate
neuronal
synchrony
in
the
form
of
a
sleep
spindle
and
will
ultimately
perform
better
on
a
declarative
recall
test
than
individuals
who
are
not
exposed
to
tACS.
Additionally,
we
hypothesize
that
individuals
who
are
exposed
to
tACS
between
12
and
15
Hz
during
SWS
will
demonstrate
neuronal
synchrony
in
the
form
of
a
sleep
spindle
and
will
ultimately
perform
better
on
a
declarative
recall
test
than
individuals
who
are
not
exposed
to
tACS,
as
well
as
individuals
who
are
exposed
to
tACS
during
stage-­‐2
sleep.

7. Method
Participants.
We
would
like
to
recruit
200
participants
for
this
study.
Ideally
these
participants
would
be
diverse
in
age,
ethnicity,
and
gender
identification
in
order
to
ensure
generalizability.
Additionally,
participants
would
ideally
have
no
history
of
sleep
disorders
or
mental
illness
as
these
could
be
potential
confounds.
We
would
like
to
recruit
them
through
email
blasts,
social
media,
word
of
mouth,
and
newspaper
ads.
Finally,
we
would
like
to
compensate
individuals
for
their
time
with
a
small
gift
card
to
a
local
restaurant.
Apparatus.
For
this
experiment,
we
would
need
access
to
a
sleep
lab
containing
the
necessary
equipment
for
monitoring
brain
waves
and
for
administering
current
stimulation
(EEG
with
tACS
capabilities,
EOG,
and
EMG).
Additionally,
we
would
need
a
declarative
memory
task.
The
task
that
we
would
like
to
use
is
a
modified
version
of
the
Plihal
and
Born
test
used
in
the
Schabus
et
al.
(2004)
study.
This
test
is
a
paired-­‐associate
wordlist
that
has
been
modified
to
reduce
the
likelihood
of
a
false
pairing
as
a
result
of
a
semantic
connection—thus
giving
the
most
accurate
depiction
of
declarative
recall.
Procedure.
All
participants
will
be
given
the
modified
version
of
the
Plihal
and
Born
test
in
which
they
are
to
memorize
paired
words.
The
participants
will
be
randomly
divided
into
two
groups-­‐
the
control
group
and
the
experimental
group.
Then
they
will
go
into
the
sleep
lab
for
a
night.
In
the
lab,
their
sleep
will
be
monitored.
The
control
group
will
only
be
monitored.
The
experimental
group
will
be
randomly
divided
in
half.
One
half
of
the
experimental
group
will
receive
tACS
during
stage-­‐2
sleep
while
the
other
half
of
the
experimental
group
will
receive
tACS

8. during
SWS.
The
number
of
sleep
spindles
will
be
recorded.
The
next
day,
participants
will
be
given
the
recall
portion
of
the
Plihal
and
Born
test
in
which
they
identify
as
many
of
the
pairs
that
they
have
already
been
exposed
to
as
possible.
Results
Once
we
have
recorded
all
of
the
data
we
will
first
compare
the
number
of
sleep
spindles
that
participants
in
each
group
had
using
an
ANOVA
test.
Then,
we
will
use
the
same
test
to
determine
if
the
independent
variables
(tACS
at
different
stages
of
sleep)
had
an
effect
on
the
number
of
pairs
recalled.
If
the
tests
show
that
tACS
resulted
in
significantly
higher
or
lower
recall
ability
than
the
control
group
and
the
tACS
group
experienced
less
than
or
equal
to
the
number
of
sleep
spindles
that
the
control
group
experienced
then
we
will
know
that
there
is
a
confounding
variable.

9. References
Cox,
R.,
Hofman,
W.
F.,
&
Talamini,
L.
M.
(2012).
Involvement
of
spindles
in
memory
consolidation
is
slow
wave
sleep-­‐specific.
Learning
&
Memory,
19.
264-­‐267.
Marshall
L.,
Helgadottir
H.,
&
Molle
M.
(2006).
Boosting
slow
oscillations
during
sleep
potentiates
memory.
Nature,
444.
610-­‐613
Marshall
L,
Kirov
R,
Brade
J,
Mölle
M,
&
Born
J.
(2011).
Transcranial
electrical
currents
to
probe
EEG
brain
rhythms
and
memory
consolidation
during
sleep
in
humans.
PLOS
One,
6.
Schabus,
M.
(2004).
The
significance
of
sleep
spindles
for
declarative
memory
consolidation
(Doctoral
dissertation).
Retreived
from
University
of
Salzburg.
Schabus,
M.,
Gruber,
G.,
Parapatics,
S.,
Sauter,
C.,
Klösch,
G.,
Anderer,
P.,
…
Zeitlhofer,
J.
(2004).
Sleep
spindles
and
their
significance
for
declarative
memory
consolidation.
SLEEP,
27(8).
1479-­‐1485.
Seeck-­‐Hirschner,
M.,
Baier,
P.
C.,
Weinhold,
S.
L.,
Dittmar,
M.,
Heiermann,
S.
(2012).
Declarative
memory
performance
is
associated
with
the
number
of
sleep
spindles
in
elderly
women.
The
American
Journal
of
Geriatric
Psychiatry,
20(9).
782-­‐8.
Tisserand,
D.
J.,
&
Jolies,
J.
(2003).
On
the
involvement
of
prefrontal
networks
in
cognitive
ageing.
Cortex,
39.
1107-­‐1128.
Voss,
U.,
Holzmann,
R.,
Hobson,
A.,
Paulus,
W.,
Koppehele-­‐Gossel,
J.,
Kilmke,
A.,
&
Nitsche,
M.
A.
(2014).
Induction
of
self
awareness
in
dreams
through
frontal
low
current
stimulation
of
gamma
activity.
Nature
Neuroscience.

10. Yamadori,
A.
(1971).
Role
of
the
spindles
in
the
onset
of
sleep.
Kobe
Journal
of
Medical
Sciences,
17,
97-­‐111.