<s>
Functional	B-Algorithm
near-infrared	I-Algorithm
spectroscopy	I-Algorithm
(	O
fNIRS	B-Algorithm
)	O
is	O
an	O
optical	O
brain	O
monitoring	O
technique	O
which	O
uses	O
near-infrared	O
spectroscopy	O
for	O
the	O
purpose	O
of	O
functional	B-Algorithm
neuroimaging	I-Algorithm
.	O
</s>
<s>
Using	O
fNIRS	B-Algorithm
,	O
brain	B-Application
activity	I-Application
is	O
measured	O
by	O
using	O
near-infrared	O
light	O
to	O
estimate	O
cortical	O
hemodynamic	O
activity	O
which	O
occur	O
in	O
response	O
to	O
neural	O
activity	O
.	O
</s>
<s>
Alongside	O
EEG	B-Application
,	O
fNIRS	B-Algorithm
is	O
one	O
of	O
the	O
most	O
common	O
non-invasive	O
neuroimaging	O
techniques	O
which	O
can	O
be	O
used	O
in	O
portable	O
contexts	O
.	O
</s>
<s>
The	O
signal	O
is	O
often	O
compared	O
with	O
the	O
BOLD	B-Algorithm
signal	I-Algorithm
measured	O
by	O
fMRI	B-Algorithm
and	O
is	O
capable	O
of	O
measuring	O
changes	O
both	O
in	O
oxy	O
-	O
and	O
deoxyhemoglobin	O
concentration	O
,	O
but	O
can	O
only	O
measure	O
from	O
regions	O
near	O
the	O
cortical	O
surface	O
.	O
</s>
<s>
fNIRS	B-Algorithm
may	O
also	O
be	O
referred	O
to	O
as	O
Optical	O
Topography	O
(	O
OT	O
)	O
and	O
is	O
sometimes	O
referred	O
to	O
simply	O
as	O
NIRS	O
.	O
</s>
<s>
fNIRS	B-Algorithm
estimates	O
the	O
concentration	O
of	O
hemoglobin	O
from	O
changes	O
in	O
absorption	O
of	O
near	O
infrared	O
light	O
.	O
</s>
<s>
Different	O
fNIRS	B-Algorithm
techniques	O
can	O
also	O
use	O
the	O
way	O
in	O
which	O
light	O
propagates	O
to	O
estimate	O
blood	O
volume	O
and	O
oxygenation	O
.	O
</s>
<s>
fNIRS	B-Algorithm
is	O
a	O
non-invasive	O
imaging	O
method	O
involving	O
the	O
quantification	O
of	O
chromophore	O
concentration	O
resolved	O
from	O
the	O
measurement	O
of	O
near	O
infrared	O
(	O
NIR	O
)	O
light	O
attenuation	O
or	O
temporal	O
or	O
phasic	O
changes	O
.	O
</s>
<s>
fNIRS	B-Algorithm
focuses	O
primarily	O
on	O
absorption	O
:	O
differences	O
in	O
the	O
absorption	O
spectra	O
of	O
deoxy-Hb	O
and	O
oxy-Hb	O
allow	O
the	O
measurement	O
of	O
relative	O
changes	O
in	O
hemoglobin	O
concentration	O
through	O
the	O
use	O
of	O
light	O
attenuation	O
at	O
multiple	O
wavelengths	O
.	O
</s>
<s>
fNIRS	B-Algorithm
is	O
most	O
sensitive	O
to	O
hemodynamic	O
changes	O
which	O
occur	O
nearest	O
to	O
the	O
scalp	O
and	O
these	O
superficial	O
artifacts	O
are	O
often	O
addressed	O
using	O
additional	O
light	O
detectors	O
located	O
closer	O
to	O
the	O
light	O
source	O
(	O
short-separation	O
detectors	O
)	O
.	O
</s>
<s>
demonstrated	O
the	O
feasibility	O
of	O
fNIRS	B-Algorithm
in	O
adult	O
humans	O
.	O
</s>
<s>
Currently	O
,	O
wearable	O
fNIRS	B-Algorithm
are	O
being	O
developed	O
.	O
</s>
<s>
The	O
idea	O
had	O
been	O
successfully	O
implemented	O
in	O
launching	O
their	O
first	O
fNIRS	B-Algorithm
(	O
or	O
Optical	O
Topography	O
,	O
as	O
they	O
call	O
it	O
)	O
device	O
based	O
on	O
Frequency	O
Domain	O
in	O
2001	O
:	O
Hitachi	O
ETG-100	O
.	O
</s>
<s>
Later	O
,	O
Harumi	O
Oishi	O
( 大石	O
晴美	O
)	O
,	O
a	O
PhD-to-be	O
at	O
Nagoya	O
University	O
,	O
published	O
her	O
doctoral	O
dissertation	O
in	O
2003	O
with	O
the	O
subject	O
of	O
"	O
language	O
learners	O
 '	O
cortical	O
activation	O
patterns	O
measured	O
by	O
ETG-100	O
"	O
under	O
the	O
supervision	O
of	O
Professor	O
Toru	O
Kinoshita	O
( 木下	O
微	O
)	O
—	O
presenting	O
a	O
new	O
prospect	O
on	O
the	O
use	O
of	O
fNIRS	B-Algorithm
.	O
</s>
<s>
Currently	O
,	O
there	O
are	O
three	O
modalities	O
of	O
fNIR	B-Algorithm
spectroscopy	O
:	O
</s>
<s>
However	O
,	O
CW-fNIRS	O
does	O
not	O
provide	O
any	O
knowledge	O
of	O
photon	O
path-length	O
,	O
so	O
changes	O
in	O
HbO	O
concentration	O
are	O
relative	O
to	O
an	O
unknown	O
path-length	O
.	O
</s>
<s>
Many	O
CW-fNIRS	O
commercial	O
systems	O
use	O
estimations	O
of	O
photon	O
path-length	O
derived	O
from	O
computerized	O
Monte-Carlo	B-Algorithm
simulations	I-Algorithm
and	O
physical	O
models	O
,	O
to	O
approximate	O
absolute	O
quantification	O
of	O
hemoglobin	O
concentrations	O
.	O
</s>
<s>
Due	O
to	O
their	O
simplicity	O
and	O
cost-effectiveness	O
,	O
CW-fNIRS	O
is	O
by	O
far	O
the	O
most	O
common	O
form	O
of	O
functional	O
NIRS	O
since	O
it	O
is	O
the	O
cheapest	O
to	O
make	O
,	O
applicable	O
with	O
more	O
channels	O
,	O
and	O
ensures	O
a	O
high	O
temporal	B-General_Concept
resolution	I-General_Concept
.	O
</s>
<s>
Still	O
,	O
the	O
simplicity	O
and	O
cost-effectiveness	O
of	O
CW-based	O
devices	O
prove	O
themselves	O
to	O
be	O
the	O
most	O
favorable	O
for	O
a	O
number	O
of	O
clinical	O
applications	O
:	O
neonatal	O
care	O
,	O
patient	O
monitoring	O
systems	O
,	O
diffuse	B-Algorithm
optical	I-Algorithm
tomography	I-Algorithm
,	O
and	O
so	O
forth	O
.	O
</s>
<s>
FD-fNIRS	O
measures	O
attenuation	O
,	O
phase	O
shift	O
and	O
the	O
average	O
path	O
length	O
of	O
light	O
through	O
the	O
tissue	O
.	O
</s>
<s>
Multi-Distance	O
,	O
which	O
is	O
a	O
part	O
of	O
the	O
FD-fNIRS	O
,	O
is	O
insensitive	O
to	O
differences	O
in	O
skin	O
color	O
—	O
giving	O
constant	O
results	O
regardless	O
of	O
subject	O
variation	O
.	O
</s>
<s>
TD-fNIRS	O
does	O
have	O
a	O
slow	O
sampling	O
rate	O
as	O
well	O
as	O
a	O
limited	O
number	O
of	O
wavelengths	O
.	O
</s>
<s>
At	O
least	O
two	O
open-source	O
fNIRS	B-Algorithm
models	O
are	O
available	O
online	O
:	O
</s>
<s>
It	O
is	O
a	O
set	O
of	O
matlab	O
scripts	O
used	O
for	O
analyzing	O
fNIRS	B-Algorithm
data	O
.	O
</s>
<s>
This	O
toolbox	O
is	O
a	O
set	O
of	O
Matlab-based	O
tools	O
for	O
the	O
analysis	O
of	O
functional	B-Algorithm
near-infrared	I-Algorithm
spectroscopy	I-Algorithm
(	O
fNIRS	B-Algorithm
)	O
.	O
</s>
<s>
This	O
toolbox	O
defines	O
the	O
+nirs	O
namespace	O
and	O
includes	O
a	O
series	O
of	O
tools	O
for	O
signal	O
processing	O
,	O
display	O
,	O
and	O
statistics	O
of	O
fNIRS	B-Algorithm
data	O
.	O
</s>
<s>
AtlasViewer	O
allows	O
fNIRS	B-Algorithm
data	O
to	O
be	O
visualized	O
on	O
a	O
model	O
of	O
the	O
brain	O
.	O
</s>
<s>
fNIRS	B-Algorithm
has	O
been	O
successfully	O
implemented	O
as	O
a	O
control	O
signal	O
for	O
brain	B-Application
–	I-Application
computer	I-Application
interface	I-Application
systems	O
.	O
</s>
<s>
fNIRS	B-Algorithm
measurements	O
can	O
be	O
used	O
to	O
calculate	O
functional	O
connectivity	O
.	O
</s>
<s>
Multi-channel	O
fNIRS	B-Algorithm
measurements	O
create	O
a	O
topographical	O
map	O
of	O
neural	O
activation	O
,	O
whereby	O
temporal	O
correlation	O
between	O
spatially	O
separated	O
events	O
can	O
be	O
analyzed	O
.	O
</s>
<s>
The	O
low	O
cost	O
,	O
portability	O
and	O
high	O
temporal	B-General_Concept
resolution	I-General_Concept
of	O
fNIRS	B-Algorithm
,	O
with	O
respect	O
to	O
fMRI	B-Algorithm
,	O
have	O
proven	O
to	O
be	O
highly	O
advantageous	O
in	O
studies	O
of	O
this	O
nature	O
.	O
</s>
<s>
Diffuse	B-Algorithm
optical	I-Algorithm
tomography	I-Algorithm
is	O
the	O
3D	O
version	O
of	O
Diffuse	B-Algorithm
optical	I-Algorithm
imaging	I-Algorithm
.	O
</s>
<s>
These	O
images	O
can	O
be	O
used	O
to	O
develop	O
a	O
3D	O
volumetric	O
model	O
which	O
is	O
known	O
as	O
the	O
Diffuse	B-Algorithm
Optical	I-Algorithm
Tomography	I-Algorithm
.	O
</s>
<s>
fNIRS	B-Algorithm
electrode	O
locations	O
can	O
be	O
defined	O
using	O
a	O
variety	O
of	O
layouts	O
,	O
including	O
names	O
and	O
locations	O
that	O
are	O
specified	O
by	O
the	O
International	B-Algorithm
10	I-Algorithm
–	I-Algorithm
20	I-Algorithm
system	I-Algorithm
as	O
well	O
as	O
other	O
layouts	O
that	O
are	O
specifically	O
optimized	O
to	O
maintain	O
a	O
consistent	O
30mm	O
distance	O
between	O
each	O
location	O
.	O
</s>
<s>
The	O
use	O
of	O
fNIRS	B-Algorithm
as	O
a	O
functional	B-Algorithm
neuroimaging	I-Algorithm
method	O
relies	O
on	O
the	O
principle	O
of	O
neuro-vascular	O
coupling	O
also	O
known	O
as	O
the	O
haemodynamic	O
response	O
or	O
blood-oxygen-level	B-Algorithm
dependent	I-Algorithm
(	O
BOLD	B-Algorithm
)	O
response	O
.	O
</s>
<s>
This	O
principle	O
also	O
forms	O
the	O
core	O
of	O
fMRI	B-Algorithm
techniques	O
.	O
</s>
<s>
fNIRS	B-Algorithm
and	O
fMRI	B-Algorithm
are	O
sensitive	O
to	O
similar	O
physiologic	O
changes	O
and	O
are	O
often	O
comparative	O
methods	O
.	O
</s>
<s>
Studies	O
relating	O
fMRI	B-Algorithm
and	O
fNIRS	B-Algorithm
show	O
highly	O
correlated	O
results	O
in	O
cognitive	O
tasks	O
.	O
</s>
<s>
fNIRS	B-Algorithm
has	O
several	O
advantages	O
in	O
cost	O
and	O
portability	O
over	O
fMRI	B-Algorithm
,	O
but	O
cannot	O
be	O
used	O
to	O
measure	O
cortical	O
activity	O
more	O
than	O
4cm	O
deep	O
due	O
to	O
limitations	O
in	O
light	O
emitter	O
power	O
and	O
has	O
more	O
limited	O
spatial	O
resolution	O
.	O
</s>
<s>
fNIRS	B-Algorithm
includes	O
the	O
use	O
of	O
diffuse	B-Algorithm
optical	I-Algorithm
tomography	I-Algorithm
(	O
DOT/NIRDOT	O
)	O
for	O
functional	O
purposes	O
.	O
</s>
<s>
Multiplexing	O
fNIRS	B-Algorithm
channels	O
can	O
allow	O
2D	O
topographic	O
functional	O
maps	O
of	O
brain	B-Application
activity	I-Application
(	O
e.g.	O
</s>
<s>
while	O
using	O
multiple	O
emitter	O
spacings	O
may	O
be	O
used	O
to	O
build	O
3D	O
tomographic	B-Algorithm
maps	O
.	O
</s>
<s>
Hyperscanning	O
involves	O
two	O
or	O
more	O
brains	O
monitored	O
simultaneously	O
to	O
investigate	O
interpersonal	O
(	O
across-brains	O
)	O
neural	O
correlates	O
in	O
various	O
social	O
situations	O
,	O
which	O
proves	O
fNIRS	B-Algorithm
to	O
be	O
a	O
suitable	O
modality	O
for	O
investigating	O
live	O
brain-to-brain	O
social	O
interactions	O
.	O
</s>
<s>
Modern	O
fNIRS	B-Algorithm
systems	O
are	O
combined	O
with	O
virtual	O
or	O
augmented	O
reality	O
in	O
studies	O
on	O
brain-computer	B-Application
interfaces	I-Application
,	O
neurorehabilitation	O
or	O
social	O
perception	O
.	O
</s>
<s>
fNIRS	B-Algorithm
can	O
be	O
used	O
to	O
monitor	O
musicians	O
 '	O
brain	B-Application
activity	I-Application
while	O
playing	O
musical	O
instruments	O
.	O
</s>
<s>
The	O
advantages	O
of	O
fNIRS	B-Algorithm
are	O
,	O
among	O
other	O
things	O
:	O
noninvasiveness	O
,	O
low-cost	O
modalities	O
,	O
perfect	O
safety	O
,	O
high	O
temporal	B-General_Concept
resolution	I-General_Concept
,	O
compatibility	O
with	O
other	O
imaging	O
modalities	O
,	O
and	O
multiple	O
hemodynamic	O
biomarkers	O
.	O
</s>
<s>
For	O
fNIRS	B-Algorithm
those	O
include	O
:	O
low	O
brain	O
sensitivity	O
,	O
low	O
spatial	O
resolution	O
,	O
and	O
shallow	O
penetration	O
depth	O
.	O
</s>
<s>
Despite	O
a	O
few	O
limitations	O
,	O
fNIRS	B-Algorithm
devices	O
are	O
relatively	O
small	O
,	O
lightweight	O
,	O
portable	O
and	O
wearable	O
.	O
</s>
<s>
Ultimately	O
,	O
future	O
at-risk	O
individuals	O
in	O
hospitals	O
could	O
benefit	O
from	O
neuromonitoring	O
and	O
neurorehabilitation	O
that	O
fNIRS	B-Algorithm
can	O
offer	O
.	O
</s>
<s>
Now	O
there	O
are	O
fully	O
wireless	O
research	O
grade	O
fNIRS	B-Algorithm
systems	O
in	O
the	O
market	O
.	O
</s>
<s>
When	O
comparing	O
and	O
contrasting	O
neuroimaging	O
devices	O
it	O
is	O
important	O
to	O
look	O
at	O
the	O
temporal	B-General_Concept
resolution	I-General_Concept
,	O
spatial	O
resolution	O
,	O
and	O
the	O
degree	O
of	O
immobility	O
.	O
</s>
<s>
In	O
particular	O
,	O
EEG	B-Application
(	O
electroencephalograph	B-Application
)	O
and	O
MEG	O
(	O
magnetoencephalography	O
)	O
have	O
high	O
temporal	B-General_Concept
resolution	I-General_Concept
,	O
but	O
a	O
low	O
spatial	O
resolution	O
.	O
</s>
<s>
EEG	B-Application
also	O
has	O
a	O
higher	O
degree	O
of	O
mobility	O
than	O
MEG	O
has	O
.	O
</s>
<s>
When	O
looking	O
at	O
fNIRS	B-Algorithm
,	O
they	O
are	O
similar	O
to	O
an	O
EEG	B-Application
.	O
</s>
<s>
They	O
have	O
a	O
high	O
degree	O
of	O
mobility	O
as	O
well	O
as	O
temporal	B-General_Concept
resolution	I-General_Concept
,	O
and	O
they	O
have	O
low	O
spatial	O
resolution	O
.	O
</s>
<s>
PET	O
scans	O
and	O
fMRIs	B-Algorithm
are	O
grouped	O
together	O
,	O
however	O
they	O
are	O
distinctly	O
different	O
from	O
the	O
other	O
neuroimaging	O
scans	O
.	O
</s>
<s>
They	O
have	O
a	O
high	O
degree	O
of	O
immobility	O
,	O
medium/high	O
spatial	O
resolution	O
,	O
and	O
a	O
low	O
temporal	B-General_Concept
resolution	I-General_Concept
.	O
</s>
<s>
Among	O
all	O
other	O
facts	O
,	O
what	O
makes	O
fNIRS	B-Algorithm
a	O
special	O
point	O
of	O
interest	O
is	O
that	O
it	O
is	O
compatible	O
with	O
some	O
of	O
these	O
modalities	O
,	O
including	O
:	O
MRI	O
,	O
EEG	B-Application
,	O
and	O
MEG	O
.	O
</s>
