<s>
Local	B-Algorithm
field	I-Algorithm
potentials	I-Algorithm
(	O
LFP	O
)	O
are	O
transient	O
electrical	O
signals	O
generated	O
in	O
nervous	O
and	O
other	O
tissues	O
by	O
the	O
summed	O
and	O
synchronous	O
electrical	O
activity	O
of	O
the	O
individual	O
cells	O
(	O
e.g.	O
</s>
<s>
As	O
a	O
result	O
of	O
the	O
Inverse-square	O
law	O
,	O
such	O
electrodes	O
can	O
only	O
'	O
see	O
 '	O
potentials	O
in	O
spatially	O
limited	O
radius	B-Protocol
.	O
</s>
<s>
During	O
local	B-Algorithm
field	I-Algorithm
potential	I-Algorithm
recordings	O
,	O
a	O
signal	O
is	O
recorded	O
using	O
an	O
extracellular	O
microelectrode	O
placed	O
sufficiently	O
far	O
from	O
individual	O
local	O
neurons	O
to	O
prevent	O
any	O
particular	O
cell	O
from	O
dominating	O
the	O
electrophysiological	O
signal	O
.	O
</s>
<s>
This	O
signal	O
is	O
then	O
low-pass	B-Algorithm
filtered	O
,	O
cut	O
off	O
at	O
~	O
300	O
Hz	O
,	O
to	O
obtain	O
the	O
local	B-Algorithm
field	I-Algorithm
potential	I-Algorithm
(	O
LFP	O
)	O
that	O
can	O
be	O
recorded	O
electronically	O
or	O
displayed	O
on	O
an	O
oscilloscope	O
for	O
analysis	O
.	O
</s>
<s>
The	O
unfiltered	O
signal	O
reflects	O
the	O
sum	O
of	O
action	B-Algorithm
potentials	I-Algorithm
from	O
cells	O
within	O
approximately	O
50-350	O
μm	O
from	O
the	O
tip	O
of	O
the	O
electrode	O
and	O
slower	O
ionic	O
events	O
from	O
within	O
0.5	O
–	O
3mm	O
from	O
the	O
tip	O
of	O
the	O
electrode	O
.	O
</s>
<s>
The	O
low-pass	B-Algorithm
filter	I-Algorithm
removes	O
the	O
spike	B-Algorithm
component	O
of	O
the	O
signal	O
and	O
passes	O
the	O
lower	O
frequency	O
signal	O
,	O
the	O
LFP	O
.	O
</s>
<s>
The	O
local	B-Algorithm
field	I-Algorithm
potential	I-Algorithm
is	O
believed	O
to	O
represent	O
the	O
sum	O
of	O
synaptic	B-Application
inputs	O
into	O
the	O
observed	O
area	O
,	O
as	O
opposed	O
to	O
the	O
spike	B-Algorithm
data	O
,	O
which	O
represents	O
the	O
output	O
from	O
the	O
area	O
.	O
</s>
<s>
The	O
fast	O
fluctuations	O
are	O
mostly	O
caused	O
by	O
the	O
short	O
inward	O
and	O
outward	O
currents	O
of	O
action	B-Algorithm
potentials	I-Algorithm
,	O
while	O
the	O
direct	O
contribution	O
of	O
action	B-Algorithm
potentials	I-Algorithm
is	O
minimal	O
in	O
the	O
LFP	O
.	O
</s>
<s>
The	O
LFP	O
is	O
thus	O
composed	O
of	O
the	O
more	O
sustained	O
currents	O
in	O
the	O
tissue	O
,	O
such	O
as	O
the	O
synaptic	B-Application
and	O
somato-dendritic	O
currents	O
.	O
</s>
<s>
Data-driven	O
models	O
have	O
shown	O
a	O
predictive	O
relationship	O
between	O
the	O
LFPs	O
and	O
spike	B-Algorithm
activity	O
.	O
</s>
<s>
The	O
major	O
slow	O
currents	O
involved	O
in	O
generating	O
the	O
LFP	O
are	O
believed	O
to	O
be	O
the	O
same	O
that	O
generate	O
the	O
postsynaptic	B-Algorithm
potential	I-Algorithm
(	O
PSP	O
)	O
.	O
</s>
<s>
It	O
was	O
originally	O
thought	O
that	O
EPSPs	O
and	O
IPSPs	O
were	O
the	O
exclusive	O
constituents	O
of	O
LFPs	O
,	O
but	O
phenomena	O
unrelated	O
to	O
synaptic	B-Application
events	O
were	O
later	O
found	O
to	O
contribute	O
to	O
the	O
signal	O
(	O
Kobayashi	O
1997	O
)	O
.	O
</s>
<s>
Thus	O
changes	O
in	O
the	O
local	B-Algorithm
field	I-Algorithm
potential	I-Algorithm
represent	O
simultaneous	O
dendritic	O
events	O
in	O
cells	O
in	O
the	O
open	O
field	O
configuration	O
.	O
</s>
<s>
Part	O
of	O
the	O
low-pass	B-Algorithm
filtering	I-Algorithm
giving	O
rise	O
to	O
local	B-Algorithm
field	I-Algorithm
potentials	I-Algorithm
is	O
due	O
to	O
complex	O
electrical	O
properties	O
of	O
extracellular	O
space	O
.	O
</s>
<s>
The	O
fact	O
that	O
the	O
extracellular	O
space	O
is	O
not	O
homogeneous	O
,	O
and	O
composed	O
of	O
a	O
complex	O
aggregate	O
of	O
highly	O
conductive	O
fluids	O
and	O
low-conductive	O
and	O
capacitive	O
membranes	O
,	O
can	O
exert	O
strong	O
low-pass	B-Algorithm
filtering	I-Algorithm
properties	O
.	O
</s>
<s>
Ionic	O
diffusion	O
,	O
which	O
plays	O
an	O
important	O
role	O
in	O
membrane	O
potential	O
variations	O
,	O
can	O
also	O
act	O
as	O
a	O
low-pass	B-Algorithm
filter	I-Algorithm
.	O
</s>
