<s>
Theta	B-Algorithm
waves	I-Algorithm
generate	O
the	O
theta	B-Algorithm
rhythm	I-Algorithm
,	O
a	O
neural	B-Algorithm
oscillation	I-Algorithm
in	O
the	O
brain	O
that	O
underlies	O
various	O
aspects	O
of	O
cognition	O
and	O
behavior	O
,	O
including	O
learning	O
,	O
memory	O
,	O
and	O
spatial	O
navigation	O
in	O
many	O
animals	O
.	O
</s>
<s>
It	O
can	O
be	O
recorded	O
using	O
various	O
electrophysiological	B-Application
methods	O
,	O
such	O
as	O
electroencephalogram	B-Application
(	O
EEG	B-Application
)	O
,	O
recorded	O
either	O
from	O
inside	O
the	O
brain	O
or	O
from	O
electrodes	O
attached	O
to	O
the	O
scalp	O
.	O
</s>
<s>
At	O
least	O
two	O
types	O
of	O
theta	B-Algorithm
rhythm	I-Algorithm
have	O
been	O
described	O
.	O
</s>
<s>
The	O
hippocampal	O
theta	B-Algorithm
rhythm	I-Algorithm
is	O
a	O
strong	O
oscillation	O
that	O
can	O
be	O
observed	O
in	O
the	O
hippocampus	O
and	O
other	O
brain	O
structures	O
in	O
numerous	O
species	O
of	O
mammals	O
including	O
rodents	O
,	O
rabbits	O
,	O
dogs	O
,	O
cats	O
,	O
and	O
marsupials	O
.	O
</s>
<s>
"	O
Cortical	O
theta	B-Algorithm
rhythms	I-Algorithm
"	O
are	O
low-frequency	O
components	O
of	O
scalp	O
EEG	B-Application
,	O
usually	O
recorded	O
from	O
humans	O
.	O
</s>
<s>
Theta	B-Algorithm
rhythms	I-Algorithm
can	O
be	O
quantified	O
using	O
quantitative	B-Algorithm
electroencephalography	I-Algorithm
(	O
qEEG	B-Algorithm
)	O
using	O
freely	O
available	O
toolboxes	O
,	O
such	O
as	O
,	O
EEGLAB	B-Algorithm
or	O
the	O
Neurophysiological	B-Algorithm
Biomarker	I-Algorithm
Toolbox	I-Algorithm
(	O
NBT	O
)	O
.	O
</s>
<s>
In	O
rats	O
,	O
theta	B-Algorithm
wave	I-Algorithm
rhythmicity	O
is	O
easily	O
observed	O
in	O
the	O
hippocampus	O
,	O
but	O
can	O
also	O
be	O
detected	O
in	O
numerous	O
other	O
cortical	O
and	O
subcortical	O
brain	O
structures	O
.	O
</s>
<s>
Hippocampal	O
theta	B-Algorithm
waves	I-Algorithm
,	O
with	O
a	O
frequency	O
range	O
of	O
6	O
–	O
10Hz	O
,	O
appear	O
when	O
a	O
rat	O
is	O
engaged	O
in	O
active	O
motor	O
behavior	O
such	O
as	O
walking	O
or	O
exploratory	O
sniffing	O
,	O
and	O
also	O
during	O
REM	O
sleep	O
.	O
</s>
<s>
Theta	B-Algorithm
waves	I-Algorithm
with	O
a	O
lower	O
frequency	O
range	O
,	O
usually	O
around	O
6	O
–	O
7Hz	O
,	O
are	O
sometimes	O
observed	O
when	O
a	O
rat	O
is	O
motionless	O
but	O
alert	O
.	O
</s>
<s>
When	O
a	O
rat	O
is	O
eating	O
,	O
grooming	O
,	O
or	O
sleeping	O
,	O
the	O
hippocampal	O
EEG	B-Application
usually	O
shows	O
a	O
non-rhythmic	O
pattern	O
known	O
as	O
large	O
irregular	O
activity	O
or	O
LIA	O
.	O
</s>
<s>
The	O
hippocampal	O
theta	B-Algorithm
rhythm	I-Algorithm
depends	O
critically	O
on	O
projections	O
from	O
the	O
medial	O
septal	O
area	O
,	O
which	O
in	O
turn	O
receives	O
input	O
from	O
the	O
hypothalamus	O
and	O
several	O
brainstem	O
areas	O
.	O
</s>
<s>
Hippocampal	O
theta	B-Algorithm
rhythms	I-Algorithm
in	O
other	O
species	O
differ	O
in	O
some	O
respects	O
from	O
those	O
in	O
rats	O
.	O
</s>
<s>
In	O
humans	O
,	O
hippocampal	O
theta	B-Algorithm
rhythm	I-Algorithm
has	O
been	O
observed	O
and	O
linked	O
to	O
memory	O
formation	O
and	O
navigation	O
.	O
</s>
<s>
As	O
with	O
rats	O
,	O
humans	O
exhibit	O
hippocampal	O
theta	B-Algorithm
wave	I-Algorithm
activity	O
during	O
REM	O
sleep	O
.	O
</s>
<s>
Humans	O
also	O
exhibit	O
predominantly	O
cortical	O
theta	B-Algorithm
wave	I-Algorithm
activity	O
during	O
REM	O
sleep	O
.	O
</s>
<s>
Increased	O
sleepiness	O
is	O
associated	O
with	O
decreased	O
alpha	O
wave	O
power	B-Algorithm
and	O
increased	O
theta	B-Algorithm
wave	I-Algorithm
power	B-Algorithm
.	O
</s>
<s>
Meditation	O
has	O
been	O
shown	O
to	O
increase	O
theta	O
power	B-Algorithm
.	O
</s>
<s>
The	O
function	O
of	O
the	O
hippocampal	O
theta	B-Algorithm
rhythm	I-Algorithm
is	O
not	O
clearly	O
understood	O
.	O
</s>
<s>
Green	O
and	O
Arduini	O
,	O
in	O
the	O
first	O
major	O
study	O
of	O
this	O
phenomenon	O
,	O
noted	O
that	O
hippocampal	O
theta	O
usually	O
occurs	O
together	O
with	O
desynchronized	O
EEG	B-Application
in	O
the	O
neocortex	O
,	O
and	O
proposed	O
that	O
it	O
is	O
related	O
to	O
arousal	O
.	O
</s>
<s>
Another	O
theory	O
links	O
the	O
theta	B-Algorithm
rhythm	I-Algorithm
to	O
mechanisms	O
of	O
learning	O
and	O
memory	O
(	O
Hasselmo	O
,	O
2005	O
)	O
.	O
</s>
<s>
In	O
human	O
EEG	B-Application
studies	O
,	O
the	O
term	O
theta	O
refers	O
to	O
frequency	O
components	O
in	O
the	O
4	O
–	O
7Hz	O
range	O
,	O
regardless	O
of	O
their	O
source	O
.	O
</s>
<s>
Although	O
there	O
were	O
a	O
few	O
earlier	O
hints	O
,	O
the	O
first	O
clear	O
description	O
of	O
regular	O
slow	O
oscillations	O
in	O
the	O
hippocampal	O
EEG	B-Application
came	O
from	O
a	O
paper	O
written	O
in	O
German	O
by	O
Jung	O
and	O
Kornmüller	O
(	O
1938	O
)	O
.	O
</s>
<s>
Green	O
and	O
Arduini	O
described	O
an	O
inverse	O
relationship	O
between	O
hippocampal	O
and	O
cortical	O
activity	O
patterns	O
,	O
with	O
hippocampal	O
rhythmicity	O
occurring	O
alongside	O
desynchronized	O
activity	O
in	O
the	O
cortex	O
,	O
whereas	O
an	O
irregular	O
hippocampal	O
activity	O
pattern	O
was	O
correlated	O
with	O
the	O
appearance	O
of	O
large	O
slow	O
waves	O
in	O
the	O
cortical	O
EEG	B-Application
.	O
</s>
<s>
By	O
1965	O
,	O
Charles	O
Stumpf	O
was	O
able	O
to	O
write	O
a	O
lengthy	O
review	O
of	O
"	O
Drug	O
action	O
on	O
the	O
electrical	O
activity	O
of	O
the	O
hippocampus	O
"	O
citing	O
hundreds	O
of	O
publications	O
(	O
Stumpf	O
,	O
1965	O
)	O
,	O
and	O
in	O
1964	O
John	O
Green	O
,	O
who	O
served	O
as	O
the	O
leader	O
of	O
the	O
field	O
during	O
this	O
period	O
,	O
was	O
able	O
to	O
write	O
an	O
extensive	O
and	O
detailed	O
review	O
of	O
hippocampal	O
electrophysiology	B-Application
(	O
Green	O
,	O
1964	O
)	O
.	O
</s>
<s>
Because	O
of	O
a	O
historical	O
accident	O
,	O
the	O
term	O
"	O
theta	B-Algorithm
rhythm	I-Algorithm
"	O
is	O
used	O
to	O
refer	O
to	O
two	O
different	O
phenomena	O
,	O
"	O
hippocampal	O
theta	O
"	O
and	O
"	O
human	O
cortical	O
theta	O
"	O
.	O
</s>
<s>
Both	O
of	O
these	O
are	O
oscillatory	O
EEG	B-Application
patterns	O
,	O
but	O
they	O
may	O
have	O
little	O
in	O
common	O
beyond	O
the	O
name	O
"	O
theta	O
"	O
.	O
</s>
<s>
In	O
the	O
oldest	O
EEG	B-Application
literature	O
dating	O
back	O
to	O
the	O
1920s	O
,	O
Greek	O
letters	O
such	O
as	O
alpha	O
,	O
beta	O
,	O
theta	O
,	O
and	O
gamma	O
were	O
used	O
to	O
classify	O
EEG	B-Application
waves	O
falling	O
into	O
specific	O
frequency	O
ranges	O
,	O
with	O
"	O
theta	O
"	O
generally	O
meaning	O
a	O
range	O
of	O
about	O
4	O
–	O
7	O
cycles	O
per	O
second	O
(	O
Hz	O
)	O
.	O
</s>
<s>
Later	O
,	O
hippocampal	O
oscillations	O
of	O
the	O
same	O
type	O
were	O
observed	O
in	O
rats	O
;	O
however	O
,	O
the	O
frequency	O
of	O
rat	O
hippocampal	O
EEG	B-Application
oscillations	O
averaged	O
about	O
8Hz	O
and	O
rarely	O
fell	O
below	O
6Hz	O
.	O
</s>
<s>
Thus	O
the	O
rat	O
hippocampal	O
EEG	B-Application
oscillation	O
should	O
not	O
,	O
strictly	O
speaking	O
,	O
have	O
been	O
called	O
a	O
"	O
theta	B-Algorithm
rhythm	I-Algorithm
"	O
.	O
</s>
<s>
EEG	B-Application
oscillations	O
in	O
the	O
4	O
–	O
7Hz	O
frequency	O
range	O
,	O
regardless	O
of	O
where	O
in	O
the	O
brain	O
they	O
occur	O
or	O
what	O
their	O
functional	O
significance	O
is	O
.	O
</s>
<s>
The	O
first	O
meaning	O
is	O
usually	O
intended	O
in	O
literature	O
that	O
deals	O
with	O
rats	O
or	O
mice	O
,	O
while	O
the	O
second	O
meaning	O
is	O
usually	O
intended	O
in	O
studies	O
of	O
human	O
EEG	B-Application
recorded	O
using	O
electrodes	O
glued	O
to	O
the	O
scalp	O
.	O
</s>
<s>
In	O
general	O
,	O
it	O
is	O
not	O
safe	O
to	O
assume	O
that	O
observations	O
of	O
"	O
theta	O
"	O
in	O
the	O
human	O
EEG	B-Application
have	O
any	O
relationship	O
to	O
the	O
"	O
hippocampal	O
theta	B-Algorithm
rhythm	I-Algorithm
"	O
.	O
</s>
<s>
Scalp	O
EEG	B-Application
is	O
generated	O
almost	O
entirely	O
by	O
the	O
cerebral	O
cortex	O
,	O
and	O
even	O
if	O
it	O
falls	O
into	O
a	O
certain	O
frequency	O
range	O
,	O
this	O
cannot	O
be	O
taken	O
to	O
indicate	O
that	O
it	O
has	O
any	O
functional	O
dependence	O
on	O
the	O
hippocampus	O
.	O
</s>
<s>
Due	O
to	O
the	O
density	O
of	O
its	O
neural	O
layers	O
,	O
the	O
hippocampus	O
generates	O
some	O
of	O
the	O
largest	O
EEG	B-Application
signals	O
of	O
any	O
brain	O
structure	O
.	O
</s>
<s>
In	O
some	O
situations	O
the	O
EEG	B-Application
is	O
dominated	O
by	O
regular	O
waves	O
at	O
4	O
–	O
10Hz	O
,	O
often	O
continuing	O
for	O
many	O
seconds	O
.	O
</s>
<s>
This	O
EEG	B-Application
pattern	O
is	O
known	O
as	O
the	O
hippocampal	O
theta	B-Algorithm
rhythm	I-Algorithm
.	O
</s>
<s>
It	O
has	O
also	O
been	O
called	O
Rhythmic	O
Slow	O
Activity	O
(	O
RSA	O
)	O
,	O
to	O
contrast	O
it	O
with	O
the	O
large	O
irregular	O
activity	O
(	O
LIA	O
)	O
that	O
usually	O
dominates	O
the	O
hippocampal	O
EEG	B-Application
when	O
theta	O
is	O
not	O
present	O
.	O
</s>
<s>
The	O
frequency	O
of	O
the	O
theta	B-Algorithm
waves	I-Algorithm
increases	O
as	O
a	O
function	O
of	O
running	O
speed	O
,	O
starting	O
at	O
about	O
6.5Hz	O
on	O
the	O
low	O
end	O
,	O
and	O
increasing	O
to	O
about	O
9Hz	O
at	O
the	O
fastest	O
running	O
speeds	O
,	O
although	O
higher	O
frequencies	O
are	O
sometimes	O
seen	O
for	O
brief	O
high-velocity	O
movements	O
such	O
as	O
jumps	O
across	O
wide	O
gaps	O
.	O
</s>
<s>
In	O
1975	O
Kramis	O
,	O
Bland	O
,	O
and	O
Vanderwolf	O
proposed	O
that	O
in	O
rats	O
there	O
are	O
two	O
distinct	O
types	O
of	O
hippocampal	O
theta	B-Algorithm
rhythm	I-Algorithm
,	O
with	O
different	O
behavioral	O
and	O
pharmacological	O
properties	O
(	O
Kramis	O
et	O
al.	O
,	O
1975	O
)	O
.	O
</s>
<s>
Vanderwolf	O
(	O
1969	O
)	O
made	O
a	O
strong	O
argument	O
that	O
the	O
presence	O
of	O
theta	O
in	O
the	O
hippocampal	O
EEG	B-Application
can	O
be	O
predicted	O
on	O
the	O
basis	O
of	O
what	O
an	O
animal	O
is	O
doing	O
,	O
rather	O
than	O
why	O
the	O
animal	O
is	O
doing	O
it	O
.	O
</s>
<s>
It	O
is	O
commonly	O
argued	O
that	O
cholinergic	O
receptors	O
do	O
not	O
respond	O
rapidly	O
enough	O
to	O
be	O
involved	O
in	O
generating	O
theta	B-Algorithm
waves	I-Algorithm
,	O
and	O
therefore	O
that	O
GABAergic	O
and/or	O
glutamatergic	O
signals	O
(	O
Ujfalussy	O
and	O
Kiss	O
,	O
2006	O
)	O
must	O
play	O
the	O
central	O
role	O
.	O
</s>
<s>
A	O
major	O
research	O
problem	O
has	O
been	O
to	O
discover	O
the	O
"	O
pacemaker	O
"	O
for	O
the	O
theta	B-Algorithm
rhythm	I-Algorithm
,	O
that	O
is	O
,	O
the	O
mechanism	O
that	O
determines	O
the	O
oscillation	O
frequency	O
.	O
</s>
<s>
As	O
a	O
rule	O
,	O
EEG	B-Application
signals	O
are	O
generated	O
by	O
synchronized	O
synaptic	O
input	O
to	O
the	O
dendrites	O
of	O
neurons	O
arranged	O
in	O
a	O
layer	O
.	O
</s>
<s>
The	O
hippocampus	O
contains	O
multiple	O
layers	O
of	O
very	O
densely	O
packed	O
neurons	O
—	O
the	O
dentate	O
gyrus	O
and	O
the	O
CA3/CA1/subicular	O
layer	O
—	O
and	O
therefore	O
has	O
the	O
potential	O
to	O
generate	O
strong	O
EEG	B-Application
signals	O
.	O
</s>
<s>
Basic	O
EEG	B-Application
theory	O
says	O
that	O
when	O
a	O
layer	O
of	O
neurons	O
generates	O
an	O
EEG	B-Application
signal	O
,	O
the	O
signal	O
always	O
phase-reverses	O
at	O
some	O
level	O
.	O
</s>
<s>
Thus	O
,	O
theta	B-Algorithm
waves	I-Algorithm
recorded	O
from	O
sites	O
above	O
and	O
below	O
a	O
generating	O
layer	O
have	O
opposite	O
signs	O
.	O
</s>
<s>
The	O
largest	O
theta	B-Algorithm
waves	I-Algorithm
,	O
however	O
,	O
are	O
generally	O
recorded	O
from	O
the	O
vicinity	O
of	O
the	O
fissure	O
that	O
separates	O
the	O
CA1	O
molecular	O
layer	O
from	O
the	O
dentate	O
gyrus	O
molecular	O
layer	O
.	O
</s>
<s>
Theta	B-Algorithm
waves	I-Algorithm
recorded	O
from	O
above	O
the	O
hippocampus	O
are	O
smaller	O
,	O
and	O
polarity-reversed	O
with	O
respect	O
to	O
the	O
fissure	O
signals	O
.	O
</s>
<s>
The	O
strongest	O
theta	B-Algorithm
waves	I-Algorithm
are	O
generated	O
by	O
the	O
CA1	O
layer	O
,	O
and	O
the	O
most	O
significant	O
input	O
driving	O
them	O
comes	O
from	O
the	O
entorhinal	O
cortex	O
,	O
via	O
the	O
direct	O
EC	O
→	O
CA1	O
pathway	O
.	O
</s>
<s>
The	O
dentate	O
gyrus	O
also	O
generates	O
theta	B-Algorithm
waves	I-Algorithm
,	O
which	O
are	O
difficult	O
to	O
separate	O
from	O
the	O
CA1	O
waves	O
because	O
they	O
are	O
considerably	O
smaller	O
in	O
amplitude	O
,	O
but	O
there	O
is	O
some	O
evidence	O
that	O
dentate	O
gyrus	O
theta	O
is	O
usually	O
about	O
90	O
degrees	O
out	O
of	O
phase	O
from	O
CA1	O
theta	O
.	O
</s>
<s>
Direct	O
projections	O
from	O
the	O
septal	O
area	O
to	O
hippocampal	O
interneurons	O
also	O
play	O
a	O
role	O
in	O
generating	O
theta	B-Algorithm
waves	I-Algorithm
,	O
but	O
their	O
influence	O
is	O
much	O
smaller	O
than	O
that	O
of	O
the	O
entorhinal	O
inputs	O
(	O
which	O
are	O
,	O
however	O
,	O
themselves	O
controlled	O
by	O
the	O
septum	O
)	O
.	O
</s>
<s>
A	O
large	O
body	O
of	O
evidence	O
indicates	O
that	O
theta	B-Algorithm
rhythm	I-Algorithm
is	O
likely	O
involved	O
in	O
spatial	O
learning	O
and	O
navigation	O
(	O
Buzsáki	O
,	O
2005	O
)	O
.	O
</s>
<s>
Theta	B-Algorithm
rhythms	I-Algorithm
are	O
very	O
strong	O
in	O
rodent	O
hippocampi	O
and	O
entorhinal	O
cortex	O
during	O
learning	O
and	O
memory	O
retrieval	O
,	O
and	O
are	O
believed	O
to	O
be	O
vital	O
to	O
the	O
induction	O
of	O
long-term	O
potentiation	O
,	O
a	O
potential	O
cellular	O
mechanism	O
of	O
learning	O
and	O
memory	O
.	O
</s>
<s>
Phase	B-Algorithm
precession	I-Algorithm
along	O
the	O
theta	B-Algorithm
wave	I-Algorithm
in	O
the	O
hippocampus	O
permits	O
neural	O
signals	O
representing	O
events	O
that	O
are	O
only	O
expected	O
or	O
those	O
from	O
the	O
recent	O
past	O
to	O
be	O
placed	O
next	O
to	O
the	O
actually	O
ongoing	O
ones	O
along	O
a	O
single	O
theta	O
cycle	O
,	O
and	O
to	O
be	O
repeated	O
over	O
several	O
theta	O
cycles	O
.	O
</s>
<s>
Based	O
on	O
evidence	O
from	O
electrophysiological	B-Application
studies	O
showing	O
that	O
both	O
synaptic	O
plasticity	O
and	O
strength	O
of	O
inputs	O
to	O
hippocampal	O
region	O
CA1	O
vary	O
systematically	O
with	O
ongoing	O
theta	O
oscillations	O
(	O
Hyman	O
et	O
al.	O
,	O
2003	O
;	O
Brankack	O
et	O
al.	O
,	O
1993	O
)	O
,	O
it	O
has	O
been	O
suggested	O
that	O
the	O
theta	B-Algorithm
rhythm	I-Algorithm
functions	O
to	O
separate	O
periods	O
of	O
encoding	O
of	O
current	O
sensory	O
stimuli	O
and	O
retrieval	O
of	O
episodic	O
memory	O
cued	O
by	O
current	O
stimuli	O
so	O
as	O
to	O
avoid	O
interference	O
that	O
would	O
occur	O
if	O
encoding	O
and	O
retrieval	O
were	O
simultaneous	O
.	O
</s>
<s>
In	O
non-human	O
animals	O
,	O
EEG	B-Application
signals	O
are	O
usually	O
recorded	O
using	O
electrodes	O
implanted	O
in	O
the	O
brain	O
;	O
the	O
majority	O
of	O
theta	O
studies	O
have	O
involved	O
electrodes	O
implanted	O
in	O
the	O
hippocampus	O
.	O
</s>
<s>
In	O
humans	O
,	O
because	O
invasive	O
studies	O
are	O
not	O
ethically	O
permissible	O
except	O
in	O
some	O
neurological	O
patients	O
,	O
the	O
largest	O
number	O
of	O
EEG	B-Application
studies	O
have	O
been	O
conducted	O
using	O
electrodes	O
glued	O
to	O
the	O
scalp	O
.	O
</s>
<s>
The	O
signals	O
picked	O
up	O
by	O
scalp	O
electrodes	O
are	O
comparatively	O
small	O
and	O
diffuse	O
and	O
arise	O
almost	O
entirely	O
from	O
the	O
cerebral	O
cortex	O
for	O
the	O
hippocampus	O
is	O
too	O
small	O
and	O
too	O
deeply	O
buried	O
to	O
generate	O
recognizable	O
scalp	O
EEG	B-Application
signals	O
.	O
</s>
<s>
Human	O
EEG	B-Application
recordings	O
show	O
clear	O
theta	O
rhythmicity	O
in	O
some	O
situations	O
,	O
but	O
because	O
of	O
the	O
technical	O
difficulties	O
,	O
it	O
has	O
been	O
difficult	O
to	O
tell	O
whether	O
these	O
signals	O
have	O
any	O
relationship	O
with	O
the	O
hippocampal	O
theta	O
signals	O
recorded	O
from	O
other	O
species	O
.	O
</s>
<s>
Green	O
and	O
Arduini	O
(	O
1954	O
)	O
,	O
in	O
their	O
pioneering	O
study	O
of	O
theta	B-Algorithm
rhythms	I-Algorithm
,	O
reported	O
only	O
brief	O
bursts	O
of	O
irregular	O
theta	O
in	O
monkeys	O
.	O
</s>
<s>
Other	O
investigators	O
have	O
reported	O
similar	O
results	O
,	O
although	O
Stewart	O
and	O
Fox	O
(	O
1991	O
)	O
described	O
a	O
clear	O
7	O
–	O
9Hz	O
theta	B-Algorithm
rhythm	I-Algorithm
in	O
the	O
hippocampus	O
of	O
urethane-anesthetized	O
macaques	O
and	O
squirrel	O
monkeys	O
,	O
resembling	O
the	O
type	O
2	O
theta	O
observed	O
in	O
urethane-anesthetized	O
rats	O
.	O
</s>
<s>
Cortical	O
theta	O
oscillations	O
were	O
observed	O
during	O
the	O
transition	O
from	O
sleep	O
and	O
during	O
quiet	O
wakefulness	O
;	O
however	O
,	O
the	O
authors	O
were	O
unable	O
to	O
find	O
any	O
correlation	O
between	O
hippocampal	O
and	O
cortical	O
theta	B-Algorithm
waves	I-Algorithm
,	O
and	O
concluded	O
that	O
the	O
two	O
processes	O
are	O
probably	O
controlled	O
by	O
independent	O
mechanisms	O
.	O
</s>
<s>
Also	O
,	O
increased	O
theta	B-Algorithm
waves	I-Algorithm
have	O
been	O
seen	O
in	O
humans	O
in	O
'	O
no	O
thought	O
 '	O
meditation	O
.	O
</s>
