<s>
Blood-oxygen-level-dependent	B-Algorithm
imaging	I-Algorithm
,	O
or	O
BOLD-contrast	O
imaging	O
,	O
is	O
a	O
method	O
used	O
in	O
functional	B-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
fMRI	B-Algorithm
)	O
to	O
observe	O
different	O
areas	O
of	O
the	O
brain	O
or	O
other	O
organs	O
,	O
which	O
are	O
found	O
to	O
be	O
active	O
at	O
any	O
given	O
time	O
.	O
</s>
<s>
In	O
1990	O
,	O
three	O
papers	O
published	O
by	O
Seiji	O
Ogawa	O
and	O
colleagues	O
showed	O
that	O
hemoglobin	O
has	O
different	O
magnetic	O
properties	O
in	O
its	O
oxygenated	O
and	O
deoxygenated	O
forms	O
(	O
deoxygenated	O
hemoglobin	O
is	O
paramagnetic	O
and	O
oxygenated	O
hemoglobin	O
is	O
diamagnetic	O
)	O
,	O
both	O
of	O
which	O
could	O
be	O
detected	O
using	O
MRI	B-Algorithm
.	O
</s>
<s>
This	O
leads	O
to	O
magnetic	O
signal	O
variation	O
which	O
can	O
be	O
detected	O
using	O
an	O
MRI	B-Algorithm
scanner	O
.	O
</s>
<s>
Although	O
most	O
fMRI	B-Algorithm
research	O
uses	O
BOLD	O
contrast	O
imaging	O
as	O
a	O
method	O
to	O
determine	O
which	O
parts	O
of	O
the	O
brain	O
are	O
most	O
active	O
,	O
because	O
the	O
signals	O
are	O
relative	O
,	O
and	O
not	O
individually	O
quantitative	O
,	O
some	O
question	O
its	O
rigor	O
.	O
</s>
<s>
BOLD-contrast	O
imaging	O
is	O
only	O
sensitive	O
to	O
differences	O
between	O
two	O
brain	O
states	O
,	O
so	O
a	O
new	O
method	O
was	O
needed	O
to	O
analyse	O
these	O
correlated	O
fluctuations	O
called	O
resting	B-Algorithm
state	I-Algorithm
fMRI	I-Algorithm
.	O
</s>
<s>
Its	O
proof	O
of	O
concept	O
of	O
blood-oxygen-level-dependent	B-Algorithm
contrast	O
imaging	O
was	O
provided	O
by	O
Seiji	O
Ogawa	O
and	O
Colleagues	O
in	O
1990	O
,	O
following	O
an	O
experiment	O
which	O
demonstrated	O
that	O
an	O
in	O
vivo	O
change	O
of	O
blood	O
oxygenation	O
could	O
be	O
detected	O
with	O
MRI	B-Algorithm
.	O
</s>
<s>
In	O
Ogawa	O
's	O
experiments	O
,	O
blood-oxygen-level-dependent	B-Algorithm
imaging	I-Algorithm
of	O
rodent	O
brain	O
slice	O
contrast	O
in	O
different	O
components	O
of	O
the	O
air	O
.	O
</s>
<s>
Other	O
notable	O
pioneers	O
of	O
BOLD	O
fMRI	B-Algorithm
include	O
Kenneth	O
Kwong	O
and	O
colleagues	O
,	O
who	O
first	O
used	O
the	O
technique	O
in	O
human	O
participants	O
in	O
1992	O
.	O
</s>
