<s>
The	O
linear	B-Algorithm
transform	I-Algorithm
model	I-Algorithm
refers	O
to	O
a	O
fundamental	O
assumption	O
guiding	O
the	O
analysis	O
of	O
functional	B-Algorithm
Magnetic	I-Algorithm
Resonance	I-Algorithm
Imaging	I-Algorithm
(	O
fMRI	B-Algorithm
)	O
studies	O
.	O
</s>
<s>
Specifically	O
,	O
the	O
model	O
holds	O
that	O
the	O
fMRI	B-Algorithm
signal	O
is	O
approximately	O
proportional	O
to	O
a	O
measure	O
of	O
local	O
neural	O
activity	O
,	O
averaged	O
over	O
a	O
spatial	O
extent	O
of	O
several	O
millimeters	O
and	O
over	O
a	O
time	O
period	O
of	O
several	O
seconds	O
.	O
</s>
<s>
The	O
linear	B-Algorithm
transform	I-Algorithm
model	I-Algorithm
is	O
a	O
common	O
and	O
widespread	O
assumption	O
used	O
in	O
the	O
interpretation	O
of	O
fMRI	B-Algorithm
studies	O
.	O
</s>
<s>
Heeger	O
and	O
Ress	O
,	O
in	O
a	O
review	O
of	O
fMRI	B-Algorithm
and	O
its	O
relation	O
to	O
neuronal	O
activity	O
,	O
argue	O
that	O
it	O
is	O
a	O
reasonable	O
and	O
useful	O
approximation	O
for	O
local	O
neural	O
activity	O
"	O
for	O
some	O
recording	O
sites	O
,	O
in	O
some	O
brain	O
areas	O
,	O
using	O
certain	O
experimental	O
protocols	O
"	O
,	O
but	O
it	O
is	O
not	O
under	O
other	O
circumstances	O
.	O
</s>
