<s>
Resting	B-Algorithm
state	I-Algorithm
fMRI	I-Algorithm
(	O
rs-fMRI	O
or	O
R-fMRI	O
)	O
is	O
a	O
method	O
of	O
functional	B-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
fMRI	B-Algorithm
)	O
that	O
is	O
used	O
in	O
brain	O
mapping	O
to	O
evaluate	O
regional	O
interactions	O
that	O
occur	O
in	O
a	O
resting	O
or	O
task-negative	O
state	O
,	O
when	O
an	O
explicit	O
task	O
is	O
not	O
being	O
performed	O
.	O
</s>
<s>
These	O
brain	O
networks	O
are	O
observed	O
through	O
changes	O
in	O
blood	O
flow	O
in	O
the	O
brain	O
which	O
creates	O
what	O
is	O
referred	O
to	O
as	O
a	O
blood-oxygen-level	B-Algorithm
dependent	I-Algorithm
(	O
BOLD	O
)	O
signal	O
that	O
can	O
be	O
measured	O
using	O
fMRI	B-Algorithm
.	O
</s>
<s>
Because	O
brain	B-Application
activity	I-Application
is	O
intrinsic	O
,	O
present	O
even	O
in	O
the	O
absence	O
of	O
an	O
externally	O
prompted	O
task	O
,	O
any	O
brain	O
region	O
will	O
have	O
spontaneous	O
fluctuations	O
in	O
BOLD	B-Algorithm
signal	I-Algorithm
.	O
</s>
<s>
The	O
resting	B-Algorithm
state	I-Algorithm
approach	O
is	O
useful	O
to	O
explore	O
the	O
brain	O
's	O
functional	O
organization	O
and	O
to	O
examine	O
if	O
it	O
is	O
altered	O
in	O
neurological	O
or	O
mental	O
disorders	O
.	O
</s>
<s>
Because	O
of	O
the	O
resting	B-Algorithm
state	I-Algorithm
aspect	O
of	O
this	O
imaging	O
,	O
data	O
can	O
be	O
collected	O
from	O
a	O
range	O
of	O
patient	O
groups	O
including	O
people	O
with	O
intellectual	O
disabilities	O
,	O
pediatric	O
groups	O
,	O
and	O
even	O
those	O
that	O
are	O
unconscious	O
.	O
</s>
<s>
Resting-state	O
functional	B-Algorithm
connectivity	I-Algorithm
research	O
has	O
revealed	O
a	O
number	O
of	O
networks	O
which	O
are	O
consistently	O
found	O
in	O
healthy	O
subjects	O
,	O
different	O
stages	O
of	O
consciousness	O
and	O
across	O
species	O
,	O
and	O
represent	O
specific	O
patterns	O
of	O
synchronous	O
activity	O
.	O
</s>
<s>
Functional	B-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
functional	B-Algorithm
MRI	I-Algorithm
or	O
fMRI	B-Algorithm
)	O
is	O
a	O
specific	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	O
)	O
procedure	O
that	O
measures	O
brain	B-Application
activity	I-Application
by	O
detecting	O
associated	O
changes	O
in	O
blood	O
flow	O
.	O
</s>
<s>
More	O
specifically	O
,	O
brain	B-Application
activity	I-Application
is	O
measured	O
through	O
low	O
frequency	O
BOLD	B-Algorithm
signal	I-Algorithm
in	O
the	O
brain	O
.	O
</s>
<s>
FMRI	B-Algorithm
is	O
used	O
both	O
in	O
research	O
,	O
and	O
to	O
a	O
lesser	O
extent	O
,	O
in	O
clinical	O
settings	O
.	O
</s>
<s>
It	O
can	O
also	O
be	O
combined	O
and	O
complemented	O
with	O
other	O
measures	O
of	O
brain	O
physiology	O
such	O
as	O
EEG	B-Application
and	O
NIRS	O
.	O
</s>
<s>
Arterial	B-Algorithm
spin	I-Algorithm
labeling	I-Algorithm
fMRI	B-Algorithm
can	O
be	O
used	O
as	O
a	O
complementary	O
approach	O
for	O
assessing	O
resting	O
brain	O
functions	O
.	O
</s>
<s>
The	O
physiological	O
blood-flow	O
response	O
largely	O
decides	O
the	O
temporal	O
sensitivity	O
,	O
how	O
well	O
neurons	O
that	O
are	O
active	O
can	O
be	O
measured	O
in	O
BOLD	O
fMRI	B-Algorithm
.	O
</s>
<s>
For	O
fMRI	B-Algorithm
specifically	O
,	O
the	O
haemodynamic	O
response	O
is	O
assumed	O
to	O
last	O
over	O
10	O
seconds	O
,	O
rising	O
multiplicatively	O
(	O
that	O
is	O
,	O
as	O
a	O
proportion	O
of	O
current	O
value	O
)	O
,	O
peaking	O
at	O
4	O
to	O
6	O
seconds	O
,	O
and	O
then	O
falling	O
multiplicatively	O
.	O
</s>
<s>
While	O
fMRI	B-Algorithm
strives	O
to	O
measure	O
the	O
neuronal	O
activity	O
in	O
the	O
brain	O
,	O
the	O
BOLD	B-Algorithm
signal	I-Algorithm
can	O
be	O
influenced	O
by	O
many	O
other	O
physiological	O
factors	O
other	O
than	O
neuronal	O
activity	O
.	O
</s>
<s>
For	O
example	O
,	O
respiratory	O
fluctuations	O
and	O
cardiovascular	O
cycles	O
affect	O
the	O
BOLD	B-Algorithm
signal	I-Algorithm
being	O
measured	O
in	O
the	O
brain	O
and	O
therefore	O
are	O
usually	O
tried	O
to	O
be	O
removed	O
during	O
processing	O
of	O
the	O
raw	O
fMRI	B-Algorithm
data	O
.	O
</s>
<s>
Due	O
to	O
these	O
sources	O
of	O
noise	O
,	O
there	O
have	O
been	O
many	O
experts	O
who	O
have	O
approached	O
the	O
idea	O
of	O
resting	B-Algorithm
state	I-Algorithm
fMRI	I-Algorithm
very	O
skeptically	O
during	O
the	O
early	O
uses	O
of	O
fMRI	B-Algorithm
.	O
</s>
<s>
Resting	B-Algorithm
state	I-Algorithm
functional	B-Algorithm
connectivity	I-Algorithm
between	O
spatially	O
distinct	O
brain	O
regions	O
reflects	O
the	O
repeated	O
history	O
of	O
co-activation	O
patterns	O
within	O
these	O
regions	O
,	O
thereby	O
serving	O
as	O
a	O
measure	O
of	O
plasticity	O
.	O
</s>
<s>
He	O
had	O
used	O
fMRI	B-Algorithm
to	O
study	O
how	O
different	O
regions	O
of	O
the	O
brain	O
communicate	O
while	O
the	O
brain	O
is	O
at	O
rest	O
and	O
not	O
performing	O
any	O
active	O
task	O
.	O
</s>
<s>
Though	O
at	O
the	O
time	O
,	O
Biswal	O
’s	O
research	O
was	O
mostly	O
disregarded	O
and	O
attributed	O
to	O
another	O
signal	O
source	O
,	O
his	O
resting	O
neuroimaging	B-Algorithm
technique	O
has	O
now	O
been	O
widely	O
replicated	O
and	O
considered	O
a	O
valid	O
method	O
of	O
mapping	O
functional	O
brain	O
networks	O
.	O
</s>
<s>
These	O
experiments	O
showed	O
that	O
the	O
brain	O
is	O
constantly	O
active	O
with	O
a	O
high	O
level	O
of	O
activity	O
even	O
when	O
the	O
person	O
is	O
not	O
engaged	O
in	O
focused	O
mental	O
work	O
(	O
the	O
resting	B-Algorithm
state	I-Algorithm
)	O
.	O
</s>
<s>
These	O
include	O
the	O
relative	O
independence	O
of	O
blood	O
flow	O
and	O
oxygen	O
consumption	O
during	O
changes	O
in	O
brain	B-Application
activity	I-Application
,	O
which	O
provided	O
the	O
physiological	O
basis	O
of	O
fMRI	B-Algorithm
,	O
as	O
well	O
the	O
discovery	O
of	O
the	O
well	O
known	O
Default	O
Mode	O
Network	O
.	O
</s>
<s>
Functional	B-Algorithm
connectivity	I-Algorithm
is	O
the	O
connectivity	O
between	O
brain	O
regions	O
that	O
share	O
functional	O
properties	O
.	O
</s>
<s>
This	O
applies	O
to	O
both	O
resting	B-Algorithm
state	I-Algorithm
and	O
task-state	O
studies	O
.	O
</s>
<s>
While	O
functional	B-Algorithm
connectivity	I-Algorithm
can	O
refer	O
to	O
correlations	O
across	O
subjects	O
,	O
runs	O
,	O
blocks	O
,	O
trials	O
,	O
or	O
individual	O
time	O
points	O
,	O
resting	B-Algorithm
state	I-Algorithm
functional	B-Algorithm
connectivity	I-Algorithm
focuses	O
on	O
connectivity	O
assessed	O
across	O
individual	O
BOLD	O
time	O
points	O
during	O
resting	O
conditions	O
.	O
</s>
<s>
Functional	B-Algorithm
connectivity	I-Algorithm
has	O
also	O
been	O
evaluated	O
using	O
the	O
perfusion	O
time	O
series	O
sampled	O
with	O
arterial	O
spin	O
labeled	O
perfusion	O
fMRI	B-Algorithm
.	O
</s>
<s>
Functional	B-Algorithm
connectivity	I-Algorithm
MRI	O
(	O
)	O
,	O
which	O
can	O
include	O
resting	B-Algorithm
state	I-Algorithm
fMRI	I-Algorithm
and	O
task-based	O
MRI	O
,	O
might	O
someday	O
help	O
provide	O
more	O
definitive	O
diagnoses	O
for	O
mental	O
health	O
disorders	O
such	O
as	O
bipolar	O
disorder	O
and	O
may	O
also	O
aid	O
in	O
understanding	O
the	O
development	O
and	O
progression	O
of	O
post-traumatic	O
stress	O
disorder	O
as	O
well	O
as	O
evaluate	O
the	O
effect	O
of	O
treatment	O
.	O
</s>
<s>
Functional	B-Algorithm
connectivity	I-Algorithm
has	O
been	O
suggested	O
to	O
be	O
an	O
expression	O
of	O
the	O
network	O
behavior	O
underlying	O
high	O
level	O
cognitive	O
function	O
partially	O
because	O
unlike	O
structural	O
connectivity	O
,	O
functional	B-Algorithm
connectivity	I-Algorithm
often	O
changes	O
on	O
the	O
order	O
of	O
seconds	O
as	O
in	O
the	O
case	O
of	O
dynamic	B-Algorithm
functional	I-Algorithm
connectivity	I-Algorithm
.	O
</s>
<s>
It	O
is	O
one	O
of	O
the	O
most	O
studied	O
networks	O
present	O
during	O
resting	B-Algorithm
state	I-Algorithm
and	O
is	O
one	O
of	O
the	O
most	O
easily	O
visualized	O
networks	O
.	O
</s>
<s>
Depending	O
on	O
the	O
method	O
of	O
resting	B-Algorithm
state	I-Algorithm
analysis	O
,	O
functional	B-Algorithm
connectivity	I-Algorithm
studies	O
have	O
reported	O
a	O
number	O
of	O
neural	B-General_Concept
networks	I-General_Concept
that	O
result	O
to	O
be	O
strongly	O
functionally	O
connected	O
during	O
rest	O
.	O
</s>
<s>
The	O
key	O
networks	O
,	O
also	O
referred	O
as	O
components	O
,	O
which	O
are	O
more	O
frequently	O
reported	O
include	O
:	O
the	O
DMN	O
,	O
the	O
sensory/motor	O
networks	O
,	O
the	O
central	B-General_Concept
executive	I-General_Concept
network	I-General_Concept
(	O
CEN	O
)	O
,	O
up	O
to	O
three	O
different	O
visual	O
networks	O
,	O
a	O
ventral	B-General_Concept
and	O
dorsal	O
attention	O
network	O
,	O
the	O
auditory	O
network	O
and	O
the	O
limbic	O
network	O
.	O
</s>
<s>
As	O
already	O
reported	O
,	O
these	O
resting-state	O
networks	O
consist	O
of	O
anatomically	O
separated	O
,	O
but	O
functionally	O
connected	O
regions	O
displaying	O
a	O
high	O
level	O
of	O
correlated	O
BOLD	B-Algorithm
signal	I-Algorithm
activity	O
.	O
</s>
<s>
Many	O
programs	O
exist	O
for	O
the	O
processing	O
and	O
analyzing	O
of	O
resting	B-Algorithm
state	I-Algorithm
fMRI	I-Algorithm
data	O
.	O
</s>
<s>
Some	O
of	O
the	O
most	O
commonly	O
used	O
programs	O
include	O
SPM	O
,	O
AFNI	O
,	O
FSL	B-Algorithm
(	O
esp	O
.	O
</s>
<s>
Melodic	O
for	O
ICA	O
)	O
,	O
CONN	B-Algorithm
,	O
,	O
and	O
Connectome	O
Computation	O
System	O
(	O
)	O
.	O
</s>
<s>
There	O
are	O
many	O
methods	O
of	O
both	O
acquiring	O
and	O
processing	O
rsfMRI	B-Algorithm
data	O
.	O
</s>
<s>
Independent	B-Algorithm
component	I-Algorithm
analysis	I-Algorithm
(	O
ICA	O
)	O
is	O
a	O
useful	O
statistical	O
approach	O
in	O
the	O
detection	O
of	O
resting	B-Algorithm
state	I-Algorithm
networks	O
.	O
</s>
<s>
Other	O
methods	O
of	O
observing	O
networks	O
and	O
connectivity	O
in	O
the	O
brain	O
include	O
the	O
seed-based	B-Algorithm
d	I-Algorithm
mapping	I-Algorithm
and	O
region	B-Algorithm
of	I-Algorithm
interest	I-Algorithm
(	O
ROI	O
)	O
methods	O
of	O
analysis	O
.	O
</s>
<s>
In	O
these	O
cases	O
,	O
signal	O
from	O
only	O
a	O
certain	O
voxel	B-Algorithm
or	O
cluster	O
of	O
voxels	B-Algorithm
known	O
as	O
the	O
seed	O
or	O
ROI	O
are	O
used	O
to	O
calculate	O
correlations	O
with	O
other	O
voxels	B-Algorithm
of	O
the	O
brain	O
.	O
</s>
<s>
Overall	O
connectivity	O
between	O
an	O
ROI	O
(	O
such	O
as	O
the	O
prefrontal	O
cortex	O
)	O
and	O
all	O
other	O
voxels	B-Algorithm
of	O
the	O
brain	O
can	O
also	O
be	O
averaged	O
,	O
providing	O
a	O
measure	O
of	O
global	O
brain	O
connectivity	O
(	O
GBC	O
)	O
specific	O
to	O
that	O
ROI	O
.	O
</s>
<s>
Other	O
methods	O
for	O
characterizing	O
resting-state	O
networks	O
include	O
partial	O
correlation	O
,	O
coherence	O
and	O
partial	O
coherence	O
,	O
phase	O
relationships	O
,	O
dynamic	B-Algorithm
time	I-Algorithm
warping	I-Algorithm
distance	O
,	O
clustering	O
,	O
and	O
graph	O
theory	O
.	O
</s>
<s>
Resting-state	O
functional	B-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
rfMRI	O
)	O
can	O
image	O
low-frequency	O
fluctuations	O
in	O
the	O
spontaneous	O
brain	B-Application
activities	I-Application
,	O
representing	O
a	O
popular	O
tool	O
for	O
macro-scale	O
functional	O
connectomics	O
to	O
characterize	O
inter-individual	O
differences	O
in	O
normal	O
brain	O
function	O
,	O
mind-brain	O
associations	O
,	O
and	O
the	O
various	O
disorders	O
.	O
</s>
<s>
With	O
fMRI	B-Algorithm
providing	O
functional	O
and	O
DWI	O
structural	O
information	O
about	O
the	O
brain	O
,	O
these	O
two	O
imaging	O
techniques	O
are	O
commonly	O
used	O
in	O
conjunction	O
to	O
provide	O
a	O
holistic	O
view	O
of	O
brain	O
network	O
interactions	O
.	O
</s>
<s>
When	O
collected	O
from	O
defined	O
ROI	O
’s	O
,	O
fMRI	B-Algorithm
data	O
informs	O
researchers	O
of	O
how	O
activity	O
(	O
blood	O
flow	O
)	O
in	O
the	O
brain	O
changes	O
over	O
time	O
or	O
during	O
a	O
task	O
.	O
</s>
<s>
Altered	O
brain	O
network	O
connectivity	O
has	O
been	O
shown	O
across	O
a	O
swathe	O
of	O
disorders	O
,	O
such	O
as	O
Schizophrenia	B-Application
,	O
Depression	O
,	O
Stroke	O
,	O
and	O
brain	O
tumor	O
,	O
underpinning	O
their	O
unique	O
symptoms	O
.	O
</s>
<s>
Many	O
imaging	O
experts	O
feel	O
that	O
in	O
order	O
to	O
obtain	O
the	O
best	O
combination	O
of	O
spatial	O
and	O
temporal	O
information	O
from	O
brain	B-Application
activity	I-Application
,	O
both	O
fMRI	B-Algorithm
as	O
well	O
as	O
electroencephalography	B-Application
(	O
EEG	B-Application
)	O
should	O
be	O
used	O
simultaneously	O
.	O
</s>
<s>
This	O
dual	O
technique	O
combines	O
the	O
EEG	B-Application
's	O
well	O
documented	O
ability	O
to	O
characterize	O
certain	O
brain	O
states	O
with	O
high	O
temporal	O
resolution	O
and	O
to	O
reveal	O
pathological	O
patterns	O
,	O
with	O
fMRI	B-Algorithm
's	O
(	O
more	O
recently	O
discovered	O
and	O
less	O
well	O
understood	O
)	O
ability	O
to	O
image	O
blood	O
dynamics	O
through	O
the	O
entire	O
brain	O
with	O
high	O
spatial	O
resolution	O
.	O
</s>
<s>
Up	O
to	O
now	O
,	O
EEG-fMRI	O
has	O
been	O
mainly	O
seen	O
as	O
an	O
fMRI	B-Algorithm
technique	O
in	O
which	O
the	O
synchronously	O
acquired	O
EEG	B-Application
is	O
used	O
to	O
characterize	O
brain	B-Application
activity	I-Application
( 	O
 '	O
brain	O
state	O
 '	O
)	O
across	O
time	O
allowing	O
to	O
map	O
(	O
through	O
statistical	O
parametric	O
mapping	O
,	O
for	O
example	O
)	O
the	O
associated	O
haemodynamic	O
changes	O
.	O
</s>
<s>
The	O
clinical	O
value	O
of	O
these	O
findings	O
is	O
the	O
subject	O
of	O
ongoing	O
investigations	O
,	O
but	O
recent	O
researches	O
suggest	O
an	O
acceptable	O
reliability	O
for	O
EEG-fMRI	O
studies	O
and	O
better	O
sensitivity	O
in	O
higher	O
field	O
scanner	O
.	O
</s>
<s>
Outside	O
the	O
field	O
of	O
epilepsy	O
,	O
EEG-fMRI	O
has	O
been	O
used	O
to	O
study	O
event-related	O
(	O
triggered	O
by	O
external	O
stimuli	O
)	O
brain	O
responses	O
and	O
provided	O
important	O
new	O
insights	O
into	O
baseline	O
brain	B-Application
activity	I-Application
during	O
resting	O
wakefulness	O
and	O
sleep	O
.	O
</s>
<s>
Positron	B-Application
emission	I-Application
tomography	I-Application
(	O
PET	O
)	O
can	O
then	O
be	O
used	O
to	O
image	O
the	O
brain	O
and	O
changes	O
in	O
blood	O
flow	O
and	O
results	O
show	O
very	O
similar	O
regions	O
of	O
connectivity	O
confirming	O
networks	O
found	O
in	O
fMRI	B-Algorithm
studies	O
and	O
TMS	O
can	O
also	O
be	O
used	O
to	O
support	O
and	O
provide	O
more	O
detailed	O
information	O
on	O
the	O
connected	O
regions	O
.	O
</s>
<s>
Potential	O
pitfalls	O
when	O
using	O
rsfMRI	B-Algorithm
to	O
determine	O
functional	O
network	O
integrity	O
are	O
contamination	O
of	O
the	O
BOLD	B-Algorithm
signal	I-Algorithm
by	O
sources	O
of	O
physiological	O
noise	O
such	O
as	O
heart	O
rate	O
,	O
respiration	O
,	O
and	O
head	O
motion	O
.	O
</s>
<s>
Research	O
using	O
resting	B-Algorithm
state	I-Algorithm
fMRI	I-Algorithm
has	O
the	O
potential	O
to	O
be	O
applied	O
in	O
clinical	O
context	O
,	O
including	O
use	O
in	O
the	O
assessment	O
of	O
many	O
different	O
diseases	O
and	O
mental	O
disorders	O
.	O
</s>
<s>
Other	O
types	O
of	O
current	O
and	O
future	O
clinical	O
applications	O
for	O
resting	B-Algorithm
state	I-Algorithm
fMRI	I-Algorithm
include	O
identifying	O
group	O
differences	O
in	O
brain	O
disease	O
,	O
obtaining	O
diagnostic	O
and	O
prognostic	O
information	O
,	O
longitudinal	O
studies	O
and	O
treatment	O
effects	O
,	O
clustering	O
in	O
heterogeneous	O
disease	O
states	O
,	O
and	O
pre-operative	O
mapping	O
and	O
targeting	O
intervention	O
.	O
</s>
<s>
As	O
resting	B-Algorithm
state	I-Algorithm
measurements	O
have	O
no	O
cognitive	O
demands	O
(	O
instead	O
of	O
psychological	O
experiments	O
including	O
tasks	O
)	O
,	O
cognitively	O
impaired	O
persons	O
can	O
also	O
be	O
measured	O
easily	O
.	O
</s>
