<s>
Event-related	B-Algorithm
functional	I-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
efMRI	B-Algorithm
)	O
is	O
a	O
technique	O
used	O
in	O
magnetic	O
resonance	O
imaging	O
of	O
medical	O
patients	O
.	O
</s>
<s>
EfMRI	B-Algorithm
is	O
used	O
to	O
detect	O
changes	O
in	O
the	O
BOLD	O
(	O
blood	B-Algorithm
oxygen	I-Algorithm
level	I-Algorithm
dependent	I-Algorithm
)	O
hemodynamic	O
response	O
to	O
neural	O
activity	O
in	O
response	O
to	O
certain	O
events	O
.	O
</s>
<s>
Within	O
fMRI	B-Algorithm
methodology	O
,	O
there	O
are	O
two	O
different	O
ways	O
that	O
are	O
typically	O
employed	O
to	O
present	O
stimuli	O
.	O
</s>
<s>
efMRI	B-Algorithm
attempts	O
to	O
model	O
the	O
change	O
in	O
fMRI	B-Algorithm
signal	O
in	O
response	O
to	O
neural	O
events	O
associated	O
with	O
behavioral	O
trials	O
.	O
</s>
<s>
According	O
to	O
D'Esposito	O
,	O
"	O
event-related	B-Algorithm
fMRI	I-Algorithm
has	O
the	O
potential	O
to	O
address	O
a	O
number	O
of	O
cognitive	O
psychology	O
questions	O
with	O
a	O
degree	O
of	O
inferential	O
and	O
statistical	O
power	O
not	O
previously	O
available.	O
"	O
</s>
<s>
If	O
the	O
experiment	O
is	O
properly	O
set	O
up	O
and	O
the	O
different	O
events	O
are	O
timed	O
correctly	O
,	O
efMRI	B-Algorithm
allows	O
a	O
person	O
to	O
observe	O
the	O
differences	O
in	O
neural	O
activity	O
associated	O
with	O
each	O
event	O
.	O
</s>
<s>
Positron	B-Application
emission	I-Application
tomography	I-Application
(	O
PET	O
)	O
,	O
was	O
the	O
most	O
frequently	O
used	O
brain	O
mapping	O
technique	O
before	O
the	O
development	O
of	O
fMRI	B-Algorithm
.	O
</s>
<s>
According	O
to	O
D'Esposito	O
,	O
they	O
include	O
that	O
fMRI	B-Algorithm
"	O
does	O
not	O
require	O
an	O
injection	O
of	O
radioisotope	O
into	O
participants	O
and	O
is	O
otherwise	O
noninvasive	O
,	O
has	O
better	O
spatial	O
resolution	O
,	O
and	O
has	O
better	O
temporal	O
resolution.	O
"	O
</s>
<s>
The	O
first	O
MRI	B-Algorithm
studies	O
employed	O
the	O
use	O
of	O
"	O
exogenous	O
paramagnetic	O
tracers	O
to	O
map	O
changes	O
in	O
cerebral	O
blood	O
volume	O
"	O
,	O
which	O
allowed	O
for	O
the	O
assessment	O
of	O
brain	O
activity	O
over	O
several	O
minutes	O
.	O
</s>
<s>
This	O
changed	O
with	O
two	O
advancements	O
to	O
MRI	B-Algorithm
,	O
the	O
rapidness	O
of	O
MRI	B-Algorithm
techniques	O
were	O
increased	O
to	O
1.5	O
Tesla	O
by	O
the	O
end	O
of	O
the	O
1980s	O
,	O
which	O
provided	O
a	O
2-d	O
image	O
.	O
</s>
<s>
When	O
fMRI	B-Algorithm
was	O
developed	O
one	O
of	O
its	O
major	O
limitations	O
was	O
the	O
inability	O
to	O
randomize	O
trials	O
,	O
but	O
the	O
event	B-Algorithm
related	I-Algorithm
fMRI	I-Algorithm
fixed	O
this	O
problem	O
.	O
</s>
<s>
Next	O
,	O
a	O
push	O
for	O
the	O
improvement	O
of	O
temporal	B-General_Concept
resolution	I-General_Concept
of	O
fMRI	B-Algorithm
studies	O
led	O
to	O
the	O
development	O
of	O
event-related	O
designs	O
,	O
which	O
according	O
to	O
Peterson	O
,	O
was	O
inherited	O
from	O
ERP	O
research	O
in	O
electrophysiology	B-Application
,	O
but	O
it	O
was	O
discovered	O
that	O
this	O
averaging	O
did	O
not	O
apply	O
very	O
well	O
to	O
the	O
hemodynamic	O
response	O
because	O
the	O
response	O
from	O
trials	O
could	O
overlap	O
.	O
</s>
<s>
Accordingly	O
,	O
fMRI	B-Algorithm
has	O
limited	O
temporal	B-General_Concept
resolution	I-General_Concept
.	O
</s>
<s>
The	O
hemodynamic	O
response	O
is	O
the	O
basis	O
for	O
the	O
BOLD	O
(	O
blood	B-Algorithm
oxygen	I-Algorithm
level	I-Algorithm
dependent	I-Algorithm
)	O
contrast	O
in	O
fMRI	B-Algorithm
.	O
</s>
<s>
In	O
a	O
typical	O
efMRI	B-Algorithm
,	O
after	O
every	O
trial	O
the	O
hemodynamic	O
response	O
is	O
allowed	O
to	O
return	O
to	O
baseline	O
.	O
</s>
<s>
In	O
rapid	O
event-related	B-Algorithm
fMRI	I-Algorithm
,	O
trials	O
are	O
randomized	O
and	O
the	O
HRF	O
is	O
deconvolved	O
afterwards	O
.	O
</s>
<s>
In	O
fMRI	B-Algorithm
data	O
,	O
it	O
is	O
assumed	O
that	O
there	O
is	O
a	O
linear	O
relationship	O
between	O
neural	O
stimulation	O
and	O
the	O
BOLD	O
response	O
.	O
</s>
<s>
Statistical	O
parametric	O
mapping	O
is	O
used	O
to	O
produce	O
a	O
design	B-Algorithm
matrix	I-Algorithm
,	O
which	O
includes	O
all	O
of	O
the	O
different	O
response	O
shapes	O
produced	O
during	O
the	O
event	O
.	O
</s>
