<s>
Electroencephalography	B-Application
(	O
EEG	B-Application
)	O
is	O
a	O
method	O
to	O
record	O
an	O
electrogram	O
of	O
the	O
spontaneous	O
electrical	O
activity	O
of	O
the	O
brain	O
.	O
</s>
<s>
The	O
biosignals	B-Algorithm
detected	O
by	O
EEG	B-Application
have	O
been	O
shown	O
to	O
represent	O
the	O
postsynaptic	B-Algorithm
potentials	I-Algorithm
of	O
pyramidal	O
neurons	O
in	O
the	O
neocortex	O
and	O
allocortex	O
.	O
</s>
<s>
It	O
is	O
typically	O
non-invasive	O
,	O
with	O
the	O
EEG	B-Application
electrodes	O
placed	O
along	O
the	O
scalp	O
(	O
commonly	O
called	O
"	O
scalp	O
EEG	B-Application
"	O
)	O
using	O
the	O
International	B-Algorithm
10-20	I-Algorithm
system	I-Algorithm
,	O
or	O
variations	O
of	O
it	O
.	O
</s>
<s>
Electrocorticography	O
,	O
involving	O
surgical	O
placement	O
of	O
electrodes	O
,	O
is	O
sometimes	O
called	O
"	O
intracranial	O
EEG	B-Application
"	O
.	O
</s>
<s>
Clinical	O
interpretation	O
of	O
EEG	B-Application
recordings	O
is	O
most	O
often	O
performed	O
by	O
visual	O
inspection	O
of	O
the	O
tracing	O
or	O
quantitative	B-Algorithm
EEG	I-Algorithm
analysis	I-Algorithm
.	O
</s>
<s>
Voltage	O
fluctuations	O
measured	O
by	O
the	O
EEG	B-Application
bioamplifier	O
and	O
electrodes	O
allow	O
the	O
evaluation	O
of	O
normal	O
brain	B-Application
activity	I-Application
.	O
</s>
<s>
As	O
the	O
electrical	O
activity	O
monitored	O
by	O
EEG	B-Application
originates	O
in	O
neurons	O
in	O
the	O
underlying	O
brain	O
tissue	O
,	O
the	O
recordings	O
made	O
by	O
the	O
electrodes	O
on	O
the	O
surface	O
of	O
the	O
scalp	O
vary	O
in	O
accordance	O
with	O
their	O
orientation	O
and	O
distance	O
to	O
the	O
source	O
of	O
the	O
activity	O
.	O
</s>
<s>
This	O
means	O
not	O
all	O
neurons	O
will	O
contribute	O
equally	O
to	O
an	O
EEG	B-Application
signal	O
with	O
an	O
EEG	B-Application
predominately	O
reflecting	O
the	O
activity	O
of	O
cortical	O
neurons	O
near	O
to	O
the	O
electrodes	O
on	O
the	O
scalp	O
.	O
</s>
<s>
Deep	O
structures	O
within	O
the	O
brain	O
further	O
away	O
from	O
the	O
electrodes	O
will	O
not	O
contribute	O
directly	O
to	O
an	O
EEG	B-Application
,	O
these	O
include	O
the	O
base	O
of	O
the	O
cortical	O
gyrus	O
,	O
mesial	O
walls	O
of	O
the	O
major	O
lobes	O
,	O
hippocampus	O
,	O
thalamus	O
and	O
brain	O
stem	O
.	O
</s>
<s>
A	O
healthy	O
human	O
EEG	B-Application
will	O
show	O
certain	O
patterns	O
of	O
activity	O
which	O
correlate	O
with	O
how	O
awake	O
a	O
person	O
is	O
.	O
</s>
<s>
The	O
observed	O
frequencies	O
are	O
subdivided	O
in	O
various	O
groups	O
,	O
these	O
are	O
alpha	B-Application
(	O
8	O
–	O
13Hz	O
)	O
,	O
beta	B-Algorithm
(	O
13	O
–	O
30Hz	O
)	O
,	O
delta	B-Algorithm
(	O
0.5	O
–	O
4Hz	O
)	O
and	O
theta	B-Algorithm
(	O
4	O
–	O
7Hz	O
)	O
.	O
</s>
<s>
Alpha	B-Application
waves	I-Application
are	O
observed	O
when	O
a	O
person	O
is	O
in	O
a	O
state	O
of	O
relaxed	O
wakefulness	O
and	O
are	O
mostly	O
prominent	O
over	O
parietal	O
and	O
occipital	O
sites	O
.	O
</s>
<s>
During	O
intense	O
mental	O
activity	O
beta	B-Algorithm
waves	I-Algorithm
are	O
more	O
prominent	O
in	O
frontal	O
areas	O
as	O
well	O
as	O
other	O
regions	O
.	O
</s>
<s>
If	O
a	O
relaxed	O
person	O
is	O
told	O
to	O
open	O
their	O
eyes	O
one	O
observes	O
alpha	B-Application
activity	O
decreasing	O
and	O
an	O
increase	O
in	O
beta	B-Algorithm
activity	O
.	O
</s>
<s>
Theta	B-Algorithm
and	O
delta	B-Algorithm
waves	I-Algorithm
are	O
not	O
seen	O
in	O
wakefulness	O
and	O
if	O
they	O
are	O
it	O
is	O
a	O
sign	O
of	O
brain	O
dysfunction	O
.	O
</s>
<s>
EEG	B-Application
can	O
detect	O
abnormal	O
electrical	O
discharges	O
such	O
as	O
sharp	O
waves	O
,	O
spikes	B-Algorithm
or	O
spike-and-wave	B-Algorithm
complexes	O
that	O
are	O
seen	O
in	O
people	O
with	O
epilepsy	O
,	O
thus	O
it	O
is	O
often	O
used	O
to	O
inform	O
the	O
medical	O
diagnosis	O
.	O
</s>
<s>
EEG	B-Application
can	O
detect	O
the	O
onset	O
and	O
spatio-temporal	O
(	O
location	O
and	O
time	O
)	O
evolution	O
of	O
seizures	O
and	O
the	O
presence	O
of	O
status	O
epilepticus	O
.	O
</s>
<s>
EEG	B-Application
used	O
to	O
be	O
a	O
first-line	O
method	O
of	O
diagnosis	O
for	O
tumors	O
,	O
stroke	O
and	O
other	O
focal	O
brain	O
disorders	O
,	O
but	O
this	O
use	O
has	O
decreased	O
with	O
the	O
advent	O
of	O
high-resolution	O
anatomical	O
imaging	O
techniques	O
such	O
as	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	O
)	O
and	O
computed	O
tomography	O
(	O
CT	O
)	O
.	O
</s>
<s>
Despite	O
limited	O
spatial	O
resolution	O
,	O
EEG	B-Application
continues	O
to	O
be	O
a	O
valuable	O
tool	O
for	O
research	O
and	O
diagnosis	O
.	O
</s>
<s>
It	O
is	O
one	O
of	O
the	O
few	O
mobile	O
techniques	O
available	O
and	O
offers	O
millisecond-range	O
temporal	O
resolution	O
which	O
is	O
not	O
possible	O
with	O
CT	O
,	O
PET	B-Application
or	O
MRI	O
.	O
</s>
<s>
Derivatives	O
of	O
the	O
EEG	B-Application
technique	O
include	O
evoked	B-Algorithm
potentials	I-Algorithm
(	O
EP	O
)	O
,	O
which	O
involves	O
averaging	O
the	O
EEG	B-Application
activity	O
time-locked	O
to	O
the	O
presentation	O
of	O
a	O
stimulus	O
of	O
some	O
sort	O
(	O
visual	O
,	O
somatosensory	O
,	O
or	O
auditory	O
)	O
.	O
</s>
<s>
Event-related	B-Algorithm
potentials	I-Algorithm
(	O
ERPs	B-Algorithm
)	O
refer	O
to	O
averaged	O
EEG	B-Application
responses	O
that	O
are	O
time-locked	O
to	O
more	O
complex	O
processing	O
of	O
stimuli	O
;	O
this	O
technique	O
is	O
used	O
in	O
cognitive	O
science	O
,	O
cognitive	O
psychology	O
,	O
and	O
psychophysiological	O
research	O
.	O
</s>
<s>
In	O
1875	O
,	O
Richard	O
Caton	O
(	O
1842	O
–	O
1926	O
)	O
,	O
a	O
physician	O
practicing	O
in	O
Liverpool	B-Application
,	O
presented	O
his	O
findings	O
about	O
electrical	O
phenomena	O
of	O
the	O
exposed	O
cerebral	O
hemispheres	O
of	O
rabbits	O
and	O
monkeys	O
in	O
the	O
British	O
Medical	O
Journal	O
.	O
</s>
<s>
In	O
1890	O
,	O
Polish	O
physiologist	O
Adolf	O
Beck	O
published	O
an	O
investigation	O
of	O
spontaneous	O
electrical	O
activity	O
of	O
the	O
brain	O
of	O
rabbits	O
and	O
dogs	O
that	O
included	O
rhythmic	O
oscillations	B-Algorithm
altered	O
by	O
light	O
.	O
</s>
<s>
Beck	O
started	O
experiments	O
on	O
the	O
electrical	O
brain	B-Application
activity	I-Application
of	O
animals	O
.	O
</s>
<s>
His	O
observation	O
of	O
fluctuating	O
brain	B-Application
activity	I-Application
led	O
to	O
the	O
conclusion	O
of	O
brain	B-Algorithm
waves	I-Algorithm
.	O
</s>
<s>
In	O
1912	O
,	O
Ukrainian	O
physiologist	O
Vladimir	O
Vladimirovich	O
Pravdich-Neminsky	O
published	O
the	O
first	O
animal	O
EEG	B-Application
and	O
the	O
evoked	B-Algorithm
potential	I-Algorithm
of	O
the	O
mammalian	O
(	O
dog	O
)	O
.	O
</s>
<s>
In	O
1914	O
,	O
Napoleon	O
Cybulski	O
and	O
Jelenska-Macieszyna	O
photographed	O
EEG	B-Application
recordings	O
of	O
experimentally	O
induced	O
seizures	O
.	O
</s>
<s>
German	O
physiologist	O
and	O
psychiatrist	O
Hans	O
Berger	O
(	O
1873	O
–	O
1941	O
)	O
recorded	O
the	O
first	O
human	O
EEG	B-Application
in	O
1924	O
.	O
</s>
<s>
Expanding	O
on	O
work	O
previously	O
conducted	O
on	O
animals	O
by	O
Richard	O
Caton	O
and	O
others	O
,	O
Berger	O
also	O
invented	O
the	O
electroencephalograph	B-Application
(	O
giving	O
the	O
device	O
its	O
name	O
)	O
,	O
an	O
invention	O
described	O
"	O
as	O
one	O
of	O
the	O
most	O
surprising	O
,	O
remarkable	O
,	O
and	O
momentous	O
developments	O
in	O
the	O
history	O
of	O
clinical	O
neurology	O
"	O
.	O
</s>
<s>
In	O
1934	O
,	O
Fisher	O
and	O
Lowenbach	O
first	O
demonstrated	O
epileptiform	O
spikes	B-Algorithm
.	O
</s>
<s>
In	O
1935	O
,	O
Gibbs	O
,	O
Davis	O
and	O
Lennox	O
described	O
interictal	O
spike	B-Algorithm
waves	O
and	O
the	O
three	O
cycles/s	O
pattern	O
of	O
clinical	O
absence	O
seizures	O
,	O
which	O
began	O
the	O
field	O
of	O
clinical	O
electroencephalography	B-Application
.	O
</s>
<s>
Subsequently	O
,	O
in	O
1936	O
Gibbs	O
and	O
Jasper	O
reported	O
the	O
interictal	O
spike	B-Algorithm
as	O
the	O
focal	O
signature	O
of	O
epilepsy	O
.	O
</s>
<s>
The	O
same	O
year	O
,	O
the	O
first	O
EEG	B-Application
laboratory	O
opened	O
at	O
Massachusetts	O
General	O
Hospital	O
.	O
</s>
<s>
Franklin	O
Offner	O
(	O
1911	O
–	O
1999	O
)	O
,	O
professor	O
of	O
biophysics	O
at	O
Northwestern	O
University	O
developed	O
a	O
prototype	O
of	O
the	O
EEG	B-Application
that	O
incorporated	O
a	O
piezoelectric	O
inkwriter	O
called	O
a	O
Crystograph	O
(	O
the	O
whole	O
device	O
was	O
typically	O
known	O
as	O
the	O
Offner	O
Dynograph	O
)	O
.	O
</s>
<s>
In	O
1947	O
,	O
The	O
American	O
EEG	B-Application
Society	O
was	O
founded	O
and	O
the	O
first	O
International	O
EEG	B-Application
congress	O
was	O
held	O
.	O
</s>
<s>
In	O
the	O
1950s	O
,	O
William	O
Grey	O
Walter	O
developed	O
an	O
adjunct	O
to	O
EEG	B-Application
called	O
EEG	B-Application
topography	O
,	O
which	O
allowed	O
for	O
the	O
mapping	O
of	O
electrical	O
activity	O
across	O
the	O
surface	O
of	O
the	O
brain	O
.	O
</s>
<s>
An	O
electroencephalograph	B-Application
system	O
manufactured	O
by	O
Beckman	O
Instruments	O
was	O
used	O
on	O
at	O
least	O
one	O
of	O
the	O
Project	O
Gemini	O
manned	O
spaceflights	O
(	O
1965-1966	O
)	O
to	O
monitor	O
the	O
brain	B-Algorithm
waves	I-Algorithm
of	O
astronauts	O
on	O
the	O
flight	O
.	O
</s>
<s>
The	O
first	O
instance	O
of	O
the	O
use	O
of	O
EEG	B-Application
to	O
control	O
a	O
physical	O
object	O
,	O
a	O
robot	O
,	O
was	O
in	O
1988	O
.	O
</s>
<s>
The	O
robot	O
would	O
follow	O
a	O
line	O
or	O
stop	O
depending	O
on	O
the	O
alpha	B-Application
activity	O
of	O
the	O
subject	O
.	O
</s>
<s>
If	O
the	O
subject	O
relaxed	O
and	O
closed	O
their	O
eyes	O
therefore	O
increasing	O
alpha	B-Application
activity	O
,	O
the	O
bot	O
would	O
move	O
.	O
</s>
<s>
Opening	O
their	O
eyes	O
thus	O
decreasing	O
alpha	B-Application
activity	O
would	O
cause	O
the	O
robot	O
to	O
stop	O
on	O
the	O
trajectory	O
.	O
</s>
<s>
Five	O
groups	O
of	O
three	O
people	O
participated	O
in	O
the	O
experiment	O
using	O
EEG	B-Application
.	O
</s>
<s>
EEG	B-Application
is	O
the	O
gold	O
standard	O
diagnostic	O
procedure	O
to	O
confirm	O
epilepsy	O
.	O
</s>
<s>
The	O
sensitivity	O
of	O
a	O
routine	O
EEG	B-Application
to	O
detect	O
interictal	O
epileptiform	O
discharges	O
at	O
epilepsy	O
centers	O
has	O
been	O
reported	O
to	O
be	O
in	O
the	O
range	O
of	O
29-55	O
%	O
.	O
</s>
<s>
Given	O
the	O
low	O
to	O
moderate	O
sensitivity	O
,	O
a	O
routine	O
EEG	B-Application
(	O
typically	O
with	O
a	O
duration	O
of	O
20	O
–	O
30	O
minutes	O
)	O
can	O
be	O
normal	O
in	O
people	O
that	O
have	O
epilepsy	O
.	O
</s>
<s>
When	O
an	O
EEG	B-Application
shows	O
interictal	O
epileptiform	O
discharges	O
(	O
e.g.	O
</s>
<s>
sharp	O
waves	O
,	O
spikes	B-Algorithm
,	O
spike-and-wave	B-Algorithm
,	O
etc	O
.	O
)	O
</s>
<s>
it	O
is	O
confirmatory	O
of	O
epilepsy	O
in	O
nearly	O
all	O
cases	O
(	O
high	O
specificity	O
)	O
,	O
however	O
up	O
to	O
3.5	O
%	O
of	O
the	O
general	O
population	O
may	O
have	O
epileptiform	O
abnormalities	O
in	O
an	O
EEG	B-Application
without	O
ever	O
having	O
had	O
a	O
seizure	O
(	O
low	O
false	B-General_Concept
positive	I-General_Concept
rate	I-General_Concept
)	O
or	O
with	O
a	O
very	O
low	O
risk	O
of	O
developing	O
epilepsy	O
in	O
the	O
future	O
.	O
</s>
<s>
When	O
a	O
routine	O
EEG	B-Application
is	O
normal	O
and	O
there	O
is	O
a	O
high	O
suspicion	O
or	O
need	O
to	O
confirm	O
epilepsy	O
,	O
it	O
may	O
be	O
repeated	O
or	O
performed	O
with	O
a	O
longer	O
duration	O
in	O
the	O
epilepsy	O
monitoring	O
unit	O
(	O
EMU	O
)	O
or	O
at	O
home	O
with	O
an	O
ambulatory	O
EEG	B-Application
.	O
</s>
<s>
In	O
addition	O
,	O
there	O
are	O
activating	O
maneuvers	O
such	O
as	O
photic	O
stimulation	O
,	O
hyperventilation	O
and	O
sleep	O
deprivation	O
that	O
can	O
increase	O
the	O
diagnostic	O
yield	O
of	O
the	O
EEG	B-Application
.	O
</s>
<s>
An	O
EEG	B-Application
might	O
also	O
be	O
helpful	O
for	O
diagnosing	O
or	O
treating	O
the	O
following	O
disorders	O
:	O
</s>
<s>
At	O
times	O
,	O
a	O
routine	O
EEG	B-Application
is	O
not	O
sufficient	O
to	O
establish	O
the	O
diagnosis	O
or	O
to	O
determine	O
the	O
best	O
course	O
of	O
action	O
in	O
terms	O
of	O
treatment	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
attempts	O
may	O
be	O
made	O
to	O
record	O
an	O
EEG	B-Application
while	O
a	O
seizure	O
is	O
occurring	O
.	O
</s>
<s>
This	O
is	O
known	O
as	O
an	O
ictal	O
recording	O
,	O
as	O
opposed	O
to	O
an	O
interictal	O
recording	O
which	O
refers	O
to	O
the	O
EEG	B-Application
recording	O
between	O
seizures	O
.	O
</s>
<s>
To	O
obtain	O
an	O
ictal	O
recording	O
,	O
a	O
prolonged	O
EEG	B-Application
is	O
typically	O
performed	O
accompanied	O
by	O
a	O
time-synchronized	O
video	O
and	O
audio	O
recording	O
.	O
</s>
<s>
Outpatient	O
ambulatory	O
video	O
EEGs	B-Application
typically	O
last	O
one	O
to	O
three	O
days	O
.	O
</s>
<s>
For	O
reasons	O
of	O
safety	O
,	O
medications	O
are	O
not	O
withdrawn	O
during	O
an	O
EEG	B-Application
outside	O
of	O
the	O
hospital	O
.	O
</s>
<s>
Ambulatory	O
video	O
EEGs	B-Application
,	O
therefore	O
,	O
have	O
the	O
advantage	O
of	O
convenience	O
and	O
are	O
less	O
expensive	O
than	O
a	O
hospital	O
admission	O
,	O
but	O
the	O
disadvantage	O
of	O
a	O
decreased	O
probability	O
of	O
recording	O
a	O
clinical	O
event	O
.	O
</s>
<s>
In	O
cases	O
of	O
epileptic	O
seizures	O
,	O
continuous	O
EEG	B-Application
monitoring	O
helps	O
to	O
characterize	O
seizures	O
and	O
localize/lateralize	O
the	O
region	O
of	O
brain	O
from	O
which	O
a	O
seizure	O
originates	O
.	O
</s>
<s>
In	O
clinical	O
use	O
,	O
EEG	B-Application
traces	O
are	O
visually	O
analyzed	O
by	O
neurologists	O
to	O
look	O
at	O
various	O
features	O
.	O
</s>
<s>
Increasingly	O
,	O
quantitative	O
analysis	O
of	O
EEG	B-Application
is	O
being	O
used	O
in	O
conjunction	O
with	O
visual	O
analysis	O
.	O
</s>
<s>
Quantitative	O
analysis	O
displays	O
like	O
power	O
spectrum	O
analysis	O
,	O
alpha-delta	O
ratio	O
,	O
amplitude	O
integrated	O
EEG	B-Application
,	O
spike	B-Algorithm
detection	O
can	O
help	O
quickly	O
identify	O
segments	O
of	O
EEG	B-Application
that	O
need	O
close	O
visual	O
analysis	O
or	O
in	O
some	O
cases	O
be	O
used	O
as	O
surrogates	O
for	O
quick	O
identification	O
of	O
seizures	O
in	O
long	O
term	O
recordings	O
.	O
</s>
<s>
EEG	B-Application
may	O
be	O
used	O
to	O
monitor	O
the	O
depth	O
of	O
anesthesia	O
,	O
as	O
an	O
indirect	O
indicator	O
of	O
cerebral	O
perfusion	O
in	O
carotid	O
endarterectomy	O
,	O
or	O
to	O
monitor	O
amobarbital	O
effect	O
during	O
the	O
Wada	O
test	O
.	O
</s>
<s>
EEG	B-Application
can	O
also	O
be	O
used	O
to	O
predict	O
the	O
depth	O
of	O
anesthesia	O
based	O
on	O
the	O
dynamics	O
of	O
the	O
alpha-band	O
.	O
</s>
<s>
EEG	B-Application
can	O
also	O
be	O
used	O
in	O
intensive	O
care	O
units	O
for	O
brain	O
function	O
monitoring	O
to	O
monitor	O
for	O
non-convulsive	O
seizures/non	O
-convulsive	O
status	O
epilepticus	O
,	O
to	O
monitor	O
the	O
effect	O
of	O
sedative/anesthesia	O
in	O
patients	O
in	O
medically	O
induced	O
coma	O
(	O
for	O
treatment	O
of	O
refractory	O
seizures	O
or	O
increased	O
intracranial	O
pressure	O
)	O
,	O
and	O
to	O
monitor	O
for	O
secondary	O
brain	O
damage	O
in	O
conditions	O
such	O
as	O
subarachnoid	O
hemorrhage	O
(	O
currently	O
a	O
research	O
method	O
)	O
.	O
</s>
<s>
after	O
cardiac	O
arrest	O
,	O
EEG	B-Application
can	O
provide	O
some	O
prognostic	O
information	O
.	O
</s>
<s>
If	O
a	O
patient	O
with	O
epilepsy	O
is	O
being	O
considered	O
for	O
resective	O
surgery	O
,	O
it	O
is	O
often	O
necessary	O
to	O
localize	O
the	O
focus	O
(	O
source	O
)	O
of	O
the	O
epileptic	O
brain	B-Application
activity	I-Application
with	O
a	O
resolution	O
greater	O
than	O
what	O
is	O
provided	O
by	O
scalp	O
EEG	B-Application
.	O
</s>
<s>
The	O
recording	O
of	O
these	O
signals	O
is	O
referred	O
to	O
as	O
electrocorticography	O
(	O
ECoG	O
)	O
,	O
subdural	O
EEG	B-Application
(	O
sdEEG	O
)	O
,	O
intracranial	O
EEG	B-Application
(	O
icEEG	O
)	O
,	O
or	O
stereotactic	O
EEG	B-Application
(	O
sEEG	O
)	O
.	O
</s>
<s>
The	O
signal	O
recorded	O
from	O
ECoG	O
is	O
on	O
a	O
different	O
scale	O
of	O
activity	O
than	O
the	O
brain	B-Application
activity	I-Application
recorded	O
from	O
scalp	O
EEG	B-Application
.	O
</s>
<s>
Low	O
voltage	O
,	O
high	O
frequency	O
components	O
that	O
cannot	O
be	O
seen	O
easily	O
(	O
or	O
at	O
all	O
)	O
in	O
scalp	O
EEG	B-Application
can	O
be	O
seen	O
clearly	O
in	O
ECoG	O
.	O
</s>
<s>
EEG	B-Application
is	O
not	O
indicated	O
for	O
diagnosing	O
headache	O
.	O
</s>
<s>
Sometimes	O
it	O
is	O
more	O
convenient	O
or	O
clinically	O
necessary	O
to	O
perform	O
ambulatory	O
EEG	B-Application
recordings	O
in	O
the	O
home	O
of	O
the	O
patient	O
.	O
</s>
<s>
EEG	B-Application
,	O
and	O
the	O
related	O
study	O
of	O
ERPs	B-Algorithm
are	O
used	O
extensively	O
in	O
neuroscience	O
,	O
cognitive	O
science	O
,	O
cognitive	O
psychology	O
,	O
neurolinguistics	O
and	O
psychophysiological	O
research	O
,	O
but	O
also	O
to	O
study	O
human	O
functions	O
such	O
as	O
swallowing	O
.	O
</s>
<s>
any	O
EEG	B-Application
techniques	O
used	O
in	O
research	O
are	O
not	O
standardised	O
sufficiently	O
for	O
clinical	O
use	O
,	O
and	O
many	O
ERP	B-Algorithm
studies	O
fail	O
to	O
report	O
all	O
of	O
the	O
necessary	O
processing	O
steps	O
for	O
data	O
collection	O
and	O
reduction	O
,	O
limiting	O
the	O
reproducibility	O
and	O
replicability	O
of	O
many	O
studies	O
.	O
</s>
<s>
But	O
research	O
on	O
mental	O
disabilities	O
,	O
such	O
as	O
auditory	O
processing	O
disorder	O
(	O
APD	O
)	O
,	O
ADD	O
,	O
or	O
ADHD	O
,	O
is	O
becoming	O
more	O
widely	O
known	O
and	O
EEGs	B-Application
are	O
used	O
as	O
research	O
and	O
treatment	O
.	O
</s>
<s>
Several	O
other	O
methods	O
to	O
study	O
brain	O
function	O
exist	O
,	O
including	O
functional	B-Algorithm
magnetic	I-Algorithm
resonance	I-Algorithm
imaging	I-Algorithm
(	O
fMRI	B-Algorithm
)	O
,	O
positron	B-Application
emission	I-Application
tomography	I-Application
(	O
PET	B-Application
)	O
,	O
magnetoencephalography	B-Algorithm
(	O
MEG	O
)	O
,	O
nuclear	O
magnetic	O
resonance	O
spectroscopy	O
(	O
NMR	O
or	O
MRS	O
)	O
,	O
electrocorticography	O
(	O
ECoG	O
)	O
,	O
single-photon	O
emission	O
computed	O
tomography	O
(	O
SPECT	O
)	O
,	O
near-infrared	O
spectroscopy	O
(	O
NIRS	B-Algorithm
)	O
,	O
and	O
event-related	B-Algorithm
optical	I-Algorithm
signal	I-Algorithm
(	O
EROS	O
)	O
.	O
</s>
<s>
Despite	O
the	O
relatively	O
poor	O
spatial	O
sensitivity	O
of	O
EEG	B-Application
,	O
the	O
"	O
one-dimensional	O
signals	O
from	O
localised	O
peripheral	O
regions	O
on	O
the	O
head	O
make	O
it	O
attractive	O
for	O
its	O
simplistic	O
fidelity	O
and	O
has	O
allowed	O
high	O
clinical	O
and	O
basic	O
research	O
throughput	O
"	O
.	O
</s>
<s>
Thus	O
,	O
EEG	B-Application
possesses	O
some	O
advantages	O
over	O
some	O
of	O
those	O
other	O
techniques	O
:	O
</s>
<s>
EEG	B-Application
prevents	O
limited	O
availability	O
of	O
technologists	O
to	O
provide	O
immediate	O
care	O
in	O
high	O
traffic	O
hospitals	O
.	O
</s>
<s>
EEG	B-Application
only	O
requires	O
a	O
quiet	O
room	O
and	O
briefcase-size	O
equipment	O
,	O
whereas	O
fMRI	B-Algorithm
,	O
SPECT	O
,	O
PET	B-Application
,	O
MRS	O
,	O
or	O
MEG	O
require	O
bulky	O
and	O
immobile	O
equipment	O
.	O
</s>
<s>
For	O
example	O
,	O
MEG	O
requires	O
equipment	O
consisting	O
of	O
liquid	O
helium-cooled	O
detectors	O
that	O
can	O
be	O
used	O
only	O
in	O
magnetically	O
shielded	O
rooms	O
,	O
altogether	O
costing	O
upwards	O
of	O
several	O
million	O
dollars	O
;	O
and	O
fMRI	B-Algorithm
requires	O
the	O
use	O
of	O
a	O
1-ton	O
magnet	O
in	O
,	O
again	O
,	O
a	O
shielded	O
room	O
.	O
</s>
<s>
EEG	B-Application
can	O
readily	O
have	O
a	O
high	O
temporal	O
resolution	O
,	O
(	O
although	O
sub-millisecond	O
resolution	O
generates	O
less	O
meaningful	O
data	O
)	O
,	O
because	O
the	O
two	O
to	O
32	O
data	O
streams	O
generated	O
by	O
that	O
number	O
of	O
electrodes	O
is	O
easily	O
stored	O
and	O
processed	O
,	O
whereas	O
3D	O
spatial	O
technologies	O
provide	O
thousands	O
or	O
millions	O
times	O
as	O
many	O
input	O
data	O
streams	O
,	O
and	O
are	O
thus	O
limited	O
by	O
hardware	O
and	O
software	O
.	O
</s>
<s>
EEG	B-Application
is	O
commonly	O
recorded	O
at	O
sampling	O
rates	O
between	O
250	O
and	O
2000Hz	O
in	O
clinical	O
and	O
research	O
settings	O
.	O
</s>
<s>
EEG	B-Application
is	O
relatively	O
tolerant	O
of	O
subject	O
movement	O
,	O
unlike	O
most	O
other	O
neuroimaging	O
techniques	O
.	O
</s>
<s>
EEG	B-Application
is	O
silent	O
,	O
which	O
allows	O
for	O
better	O
study	O
of	O
the	O
responses	O
to	O
auditory	O
stimuli	O
.	O
</s>
<s>
EEG	B-Application
does	O
not	O
involve	O
exposure	O
to	O
high-intensity	O
(	O
>1	O
Tesla	O
)	O
magnetic	O
fields	O
,	O
as	O
in	O
some	O
of	O
the	O
other	O
techniques	O
,	O
especially	O
MRI	O
and	O
MRS	O
.	O
</s>
<s>
EEG	B-Application
does	O
not	O
involve	O
exposure	O
to	O
radioligands	O
,	O
unlike	O
positron	B-Application
emission	I-Application
tomography	I-Application
.	O
</s>
<s>
EEG	B-Application
also	O
has	O
some	O
characteristics	O
that	O
compare	O
favorably	O
with	O
behavioral	O
testing	O
:	O
</s>
<s>
the	O
simplicity	O
of	O
EEG	B-Application
readily	O
provides	O
for	O
tracking	O
of	O
brain	O
changes	O
during	O
different	O
phases	O
of	O
life	O
.	O
</s>
<s>
EEG	B-Application
sleep	O
analysis	O
can	O
indicate	O
significant	O
aspects	O
of	O
the	O
timing	O
of	O
brain	O
development	O
,	O
including	O
evaluating	O
adolescent	O
brain	O
maturation	O
.	O
</s>
<s>
In	O
EEG	B-Application
there	O
is	O
a	O
better	O
understanding	O
of	O
what	O
signal	O
is	O
measured	O
as	O
compared	O
to	O
other	O
research	O
techniques	O
,	O
e.g.	O
</s>
<s>
fMRI	B-Algorithm
,	O
for	O
example	O
,	O
can	O
directly	O
display	O
areas	O
of	O
the	O
brain	O
that	O
are	O
active	O
,	O
while	O
EEG	B-Application
requires	O
intense	O
interpretation	O
just	O
to	O
hypothesize	O
what	O
areas	O
are	O
activated	O
by	O
a	O
particular	O
response	O
.	O
</s>
<s>
Depending	O
on	O
the	O
orientation	O
and	O
location	O
of	O
the	O
dipole	O
causing	O
an	O
EEG	B-Application
change	O
,	O
there	O
may	O
be	O
a	O
false	O
localization	O
due	O
to	O
the	O
inverse	O
problem	O
.	O
</s>
<s>
EEG	B-Application
poorly	O
measures	O
neural	O
activity	O
that	O
occurs	O
below	O
the	O
upper	O
layers	O
of	O
the	O
brain	O
(	O
the	O
cortex	O
)	O
.	O
</s>
<s>
Unlike	O
PET	B-Application
and	O
MRS	O
,	O
cannot	O
identify	O
specific	O
locations	O
in	O
the	O
brain	O
at	O
which	O
various	O
neurotransmitters	O
,	O
drugs	O
,	O
etc	O
.	O
</s>
<s>
Often	O
takes	O
a	O
long	O
time	O
to	O
connect	O
a	O
subject	O
to	O
EEG	B-Application
,	O
as	O
it	O
requires	O
precise	O
placement	O
of	O
dozens	O
of	O
electrodes	O
around	O
the	O
head	O
and	O
the	O
use	O
of	O
various	O
gels	O
,	O
saline	O
solutions	O
,	O
and/or	O
pastes	O
to	O
maintain	O
good	O
conductivity	O
,	O
and	O
a	O
cap	O
is	O
used	O
to	O
keep	O
them	O
in	O
place	O
.	O
</s>
<s>
While	O
the	O
length	O
of	O
time	O
differs	O
dependent	O
on	O
the	O
specific	O
EEG	B-Application
device	O
used	O
,	O
as	O
a	O
general	O
rule	O
it	O
takes	O
considerably	O
less	O
time	O
to	O
prepare	O
a	O
subject	O
for	O
MEG	O
,	O
fMRI	B-Algorithm
,	O
MRS	O
,	O
and	O
SPECT	O
.	O
</s>
<s>
Signal-to-noise	O
ratio	O
is	O
poor	O
,	O
so	O
sophisticated	O
data	O
analysis	O
and	O
relatively	O
large	O
numbers	O
of	O
subjects	O
are	O
needed	O
to	O
extract	O
useful	O
information	O
from	O
EEG	B-Application
.	O
</s>
<s>
Simultaneous	O
EEG	B-Application
recordings	O
and	O
fMRI	B-Algorithm
scans	I-Algorithm
have	O
been	O
obtained	O
successfully	O
,	O
though	O
recording	O
both	O
at	O
the	O
same	O
time	O
effectively	O
requires	O
that	O
several	O
technical	O
difficulties	O
be	O
overcome	O
,	O
such	O
as	O
the	O
presence	O
of	O
ballistocardiographic	O
artifact	O
,	O
MRI	O
pulse	O
artifact	O
and	O
the	O
induction	O
of	O
electrical	O
currents	O
in	O
EEG	B-Application
wires	O
that	O
move	O
within	O
the	O
strong	O
magnetic	O
fields	O
of	O
the	O
MRI	O
.	O
</s>
<s>
Similarly	O
,	O
simultaneous	O
recordings	O
with	O
MEG	O
and	O
EEG	B-Application
have	O
also	O
been	O
conducted	O
,	O
which	O
has	O
several	O
advantages	O
over	O
using	O
either	O
technique	O
alone	O
:	O
</s>
<s>
EEG	B-Application
requires	O
accurate	O
information	O
about	O
certain	O
aspects	O
of	O
the	O
skull	O
that	O
can	O
only	O
be	O
estimated	O
,	O
such	O
as	O
skull	O
radius	O
,	O
and	O
conductivities	O
of	O
various	O
skull	O
locations	O
.	O
</s>
<s>
MEG	O
and	O
EEG	B-Application
both	O
detect	O
activity	O
below	O
the	O
surface	O
of	O
the	O
cortex	O
very	O
poorly	O
,	O
and	O
like	O
EEG	B-Application
,	O
the	O
level	O
of	O
error	O
increases	O
with	O
the	O
depth	O
below	O
the	O
surface	O
of	O
the	O
cortex	O
one	O
attempts	O
to	O
examine	O
.	O
</s>
<s>
MEG	O
has	O
access	O
to	O
virtually	O
no	O
sources	O
of	O
brain	B-Application
activity	I-Application
below	O
a	O
few	O
centimetres	O
under	O
the	O
cortex	O
.	O
</s>
<s>
EEG	B-Application
,	O
on	O
the	O
other	O
hand	O
,	O
can	O
receive	O
signals	O
from	O
greater	O
depth	O
,	O
albeit	O
with	O
a	O
high	O
degree	O
of	O
noise	O
.	O
</s>
<s>
Combining	O
the	O
two	O
makes	O
it	O
easier	O
to	O
determine	O
what	O
in	O
the	O
EEG	B-Application
signal	O
comes	O
from	O
the	O
surface	O
(	O
since	O
MEG	O
is	O
very	O
accurate	O
in	O
examining	O
signals	O
from	O
the	O
surface	O
of	O
the	O
brain	O
)	O
,	O
and	O
what	O
comes	O
from	O
deeper	O
in	O
the	O
brain	O
,	O
thus	O
allowing	O
for	O
analysis	O
of	O
deeper	O
brain	O
signals	O
than	O
either	O
EEG	B-Application
or	O
MEG	O
on	O
its	O
own	O
.	O
</s>
<s>
Recently	O
,	O
a	O
combined	O
EEG/MEG	O
(	O
EMEG	O
)	O
approach	O
has	O
been	O
investigated	O
for	O
the	O
purpose	O
of	O
source	O
reconstruction	O
in	O
epilepsy	O
diagnosis	O
.	O
</s>
<s>
EEG	B-Application
has	O
also	O
been	O
combined	O
with	O
positron	B-Application
emission	I-Application
tomography	I-Application
.	O
</s>
<s>
This	O
provides	O
the	O
advantage	O
of	O
allowing	O
researchers	O
to	O
see	O
what	O
EEG	B-Application
signals	O
are	O
associated	O
with	O
different	O
drug	O
actions	O
in	O
the	O
brain	O
.	O
</s>
<s>
Recent	O
studies	O
using	O
machine	O
learning	O
techniques	O
such	O
as	O
neural	B-Architecture
networks	I-Architecture
with	O
statistical	O
temporal	O
features	O
extracted	O
from	O
frontal	O
lobe	O
EEG	B-Application
brainwave	B-Algorithm
data	O
has	O
shown	O
high	O
levels	O
of	O
success	O
in	O
classifying	O
mental	O
states	O
(	O
Relaxed	O
,	O
Neutral	O
,	O
Concentrating	O
)	O
,	O
mental	O
emotional	O
states	O
(	O
Negative	O
,	O
Neutral	O
,	O
Positive	O
)	O
and	O
thalamocortical	O
dysrhythmia	O
.	O
</s>
<s>
Neurons	O
are	O
constantly	O
exchanging	O
ions	O
with	O
the	O
extracellular	O
milieu	O
,	O
for	O
example	O
to	O
maintain	O
resting	O
potential	O
and	O
to	O
propagate	O
action	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
Recording	O
these	O
voltages	O
over	O
time	O
gives	O
us	O
the	O
EEG	B-Application
.	O
</s>
<s>
The	O
electric	O
potential	O
generated	O
by	O
an	O
individual	O
neuron	O
is	O
far	O
too	O
small	O
to	O
be	O
picked	O
up	O
by	O
EEG	B-Application
or	O
MEG	O
.	O
</s>
<s>
EEG	B-Application
activity	O
therefore	O
always	O
reflects	O
the	O
summation	O
of	O
the	O
synchronous	B-Algorithm
activity	I-Algorithm
of	O
thousands	O
or	O
millions	O
of	O
neurons	O
that	O
have	O
similar	O
spatial	O
orientation	O
.	O
</s>
<s>
Pyramidal	O
neurons	O
of	O
the	O
cortex	O
are	O
thought	O
to	O
produce	O
the	O
most	O
EEG	B-Application
signal	O
because	O
they	O
are	O
well-aligned	O
and	O
fire	O
together	O
.	O
</s>
<s>
Scalp	O
EEG	B-Application
activity	O
shows	O
oscillations	B-Algorithm
at	O
a	O
variety	O
of	O
frequencies	O
.	O
</s>
<s>
Several	O
of	O
these	O
oscillations	B-Algorithm
have	O
characteristic	O
frequency	O
ranges	O
,	O
spatial	O
distributions	O
and	O
are	O
associated	O
with	O
different	O
states	O
of	O
brain	O
functioning	O
(	O
e.g.	O
,	O
waking	O
and	O
the	O
various	O
sleep	O
stages	O
)	O
.	O
</s>
<s>
These	O
oscillations	B-Algorithm
represent	O
synchronized	B-Algorithm
activity	I-Algorithm
over	O
a	O
network	O
of	O
neurons	O
.	O
</s>
<s>
The	O
neuronal	O
networks	O
underlying	O
some	O
of	O
these	O
oscillations	B-Algorithm
are	O
understood	O
(	O
e.g.	O
,	O
the	O
thalamocortical	O
resonance	O
underlying	O
sleep	B-Algorithm
spindles	I-Algorithm
)	O
,	O
while	O
many	O
others	O
are	O
not	O
(	O
e.g.	O
,	O
the	O
system	O
that	O
generates	O
the	O
posterior	O
basic	O
rhythm	O
)	O
.	O
</s>
<s>
Research	O
that	O
measures	O
both	O
EEG	B-Application
and	O
neuron	O
spiking	O
finds	O
the	O
relationship	O
between	O
the	O
two	O
is	O
complex	O
,	O
with	O
a	O
combination	O
of	O
EEG	B-Application
power	O
in	O
the	O
gamma	B-Algorithm
band	O
and	O
phase	O
in	O
the	O
delta	B-Algorithm
band	O
relating	O
most	O
strongly	O
to	O
neuron	O
spike	B-Algorithm
activity	O
.	O
</s>
<s>
In	O
conventional	O
scalp	O
EEG	B-Application
,	O
the	O
recording	O
is	O
obtained	O
by	O
placing	O
electrodes	O
on	O
the	O
scalp	O
with	O
a	O
conductive	O
gel	O
or	O
paste	O
,	O
usually	O
after	O
preparing	O
the	O
scalp	O
area	O
by	O
light	O
abrasion	O
to	O
reduce	O
impedance	O
due	O
to	O
dead	O
skin	O
cells	O
.	O
</s>
<s>
Electrode	O
locations	O
and	O
names	O
are	O
specified	O
by	O
the	O
International	B-Algorithm
10	I-Algorithm
–	I-Algorithm
20	I-Algorithm
system	I-Algorithm
for	O
most	O
clinical	O
and	O
research	O
applications	O
(	O
except	O
when	O
high-density	O
arrays	O
are	O
used	O
)	O
.	O
</s>
<s>
A	O
smaller	O
number	O
of	O
electrodes	O
are	O
typically	O
used	O
when	O
recording	O
EEG	B-Application
from	O
neonates	O
.	O
</s>
<s>
In	O
analog	O
EEG	B-Application
,	O
the	O
signal	O
is	O
then	O
filtered	O
(	O
next	O
paragraph	O
)	O
,	O
and	O
the	O
EEG	B-Application
signal	O
is	O
output	O
as	O
the	O
deflection	O
of	O
pens	O
as	O
paper	O
passes	O
underneath	O
.	O
</s>
<s>
Most	O
EEG	B-Application
systems	O
these	O
days	O
,	O
however	O
,	O
are	O
digital	O
,	O
and	O
the	O
amplified	O
signal	O
is	O
digitized	O
via	O
an	O
analog-to-digital	O
converter	O
,	O
after	O
being	O
passed	O
through	O
an	O
anti-aliasing	O
filter	O
.	O
</s>
<s>
Analog-to-digital	O
sampling	O
typically	O
occurs	O
at	O
256	O
–	O
512Hz	O
in	O
clinical	O
scalp	O
EEG	B-Application
;	O
sampling	O
rates	O
of	O
up	O
to	O
20kHz	O
are	O
used	O
in	O
some	O
research	O
applications	O
.	O
</s>
<s>
These	O
procedures	O
may	O
induce	O
normal	O
or	O
abnormal	O
EEG	B-Application
activity	O
that	O
might	O
not	O
otherwise	O
be	O
seen	O
.	O
</s>
<s>
The	O
digital	O
EEG	B-Application
signal	O
is	O
stored	O
electronically	O
and	O
can	O
be	O
filtered	O
for	O
display	O
.	O
</s>
<s>
Typical	O
settings	O
for	O
the	O
high-pass	O
filter	O
and	O
a	O
low-pass	B-Algorithm
filter	I-Algorithm
are	O
0.5	O
–	O
1Hz	O
and	O
35	O
–	O
70Hz	O
respectively	O
.	O
</s>
<s>
The	O
high-pass	O
filter	O
typically	O
filters	O
out	O
slow	O
artifact	O
,	O
such	O
as	O
electrogalvanic	O
signals	O
and	O
movement	O
artifact	O
,	O
whereas	O
the	O
low-pass	B-Algorithm
filter	I-Algorithm
filters	O
out	O
high-frequency	O
artifacts	O
,	O
such	O
as	O
electromyographic	O
signals	O
.	O
</s>
<s>
The	O
EEG	B-Application
signals	O
can	O
be	O
captured	O
with	O
opensource	B-License
hardware	O
such	O
as	O
OpenBCI	B-Algorithm
and	O
the	O
signal	O
can	O
be	O
processed	O
by	O
freely	O
available	O
EEG	B-Application
software	O
such	O
as	O
EEGLAB	B-Algorithm
or	O
the	O
Neurophysiological	B-Algorithm
Biomarker	I-Algorithm
Toolbox	I-Algorithm
.	O
</s>
<s>
This	O
is	O
referred	O
to	O
variously	O
as	O
"	O
electrocorticography	O
(	O
ECoG	O
)	O
"	O
,	O
"	O
intracranial	O
EEG	B-Application
(	O
I-EEG	O
)	O
"	O
or	O
"	O
subdural	O
EEG	B-Application
(	O
SD-EEG	O
)	O
"	O
.	O
</s>
<s>
Depth	O
electrodes	O
may	O
also	O
be	O
placed	O
into	O
brain	O
structures	O
,	O
such	O
as	O
the	O
amygdala	O
or	O
hippocampus	O
,	O
structures	O
,	O
which	O
are	O
common	O
epileptic	O
foci	O
and	O
may	O
not	O
be	O
"	O
seen	O
"	O
clearly	O
by	O
scalp	O
EEG	B-Application
.	O
</s>
<s>
The	O
electrocorticographic	O
signal	O
is	O
processed	O
in	O
the	O
same	O
manner	O
as	O
digital	O
scalp	O
EEG	B-Application
(	O
above	O
)	O
,	O
with	O
a	O
couple	O
of	O
caveats	O
.	O
</s>
<s>
ECoG	O
is	O
typically	O
recorded	O
at	O
higher	O
sampling	O
rates	O
than	O
scalp	O
EEG	B-Application
because	O
of	O
the	O
requirements	O
of	O
Nyquist	O
theorem	O
–	O
the	O
subdural	O
signal	O
is	O
composed	O
of	O
a	O
higher	O
predominance	O
of	O
higher	O
frequency	O
components	O
.	O
</s>
<s>
Also	O
,	O
many	O
of	O
the	O
artifacts	O
that	O
affect	O
scalp	O
EEG	B-Application
do	O
not	O
impact	O
ECoG	O
,	O
and	O
therefore	O
display	O
filtering	O
is	O
often	O
not	O
needed	O
.	O
</s>
<s>
A	O
typical	O
adult	O
human	O
EEG	B-Application
signal	O
is	O
about	O
10	O
µV	O
to	O
100	O
µV	O
in	O
amplitude	O
when	O
measured	O
from	O
the	O
scalp	O
.	O
</s>
<s>
Since	O
an	O
EEG	B-Application
voltage	O
signal	O
represents	O
a	O
difference	O
between	O
the	O
voltages	O
at	O
two	O
electrodes	O
,	O
the	O
display	O
of	O
the	O
EEG	B-Application
for	O
the	O
reading	O
encephalographer	O
may	O
be	O
set	O
up	O
in	O
one	O
of	O
several	O
ways	O
.	O
</s>
<s>
The	O
representation	O
of	O
the	O
EEG	B-Application
channels	O
is	O
referred	O
to	O
as	O
a	O
montage	O
.	O
</s>
<s>
When	O
analog	O
(	O
paper	O
)	O
EEGs	B-Application
are	O
used	O
,	O
the	O
technologist	O
switches	O
between	O
montages	O
during	O
the	O
recording	O
in	O
order	O
to	O
highlight	O
or	O
better	O
characterize	O
certain	O
features	O
of	O
the	O
EEG	B-Application
.	O
</s>
<s>
With	O
digital	O
EEG	B-Application
,	O
all	O
signals	O
are	O
typically	O
digitized	O
and	O
stored	O
in	O
a	O
particular	O
(	O
usually	O
referential	O
)	O
montage	O
;	O
since	O
any	O
montage	O
can	O
be	O
constructed	O
mathematically	O
from	O
any	O
other	O
,	O
the	O
EEG	B-Application
can	O
be	O
viewed	O
by	O
the	O
electroencephalographer	O
in	O
any	O
display	O
montage	O
that	O
is	O
desired	O
.	O
</s>
<s>
The	O
EEG	B-Application
is	O
read	O
by	O
a	O
clinical	O
neurophysiologist	O
or	O
neurologist	O
(	O
depending	O
on	O
local	O
custom	O
and	O
law	O
regarding	O
medical	O
specialities	O
)	O
,	O
optimally	O
one	O
who	O
has	O
specific	O
training	O
in	O
the	O
interpretation	O
of	O
EEGs	B-Application
for	O
clinical	O
purposes	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
visual	O
inspection	O
of	O
the	O
waveforms	O
,	O
called	O
graphoelements	B-Application
.	O
</s>
<s>
The	O
use	O
of	O
computer	O
signal	O
processing	O
of	O
the	O
EEG	B-Application
–	O
so-called	O
quantitative	B-Algorithm
electroencephalography	I-Algorithm
–	O
is	O
somewhat	O
controversial	O
when	O
used	O
for	O
clinical	O
purposes	O
(	O
although	O
there	O
are	O
many	O
research	O
uses	O
)	O
.	O
</s>
<s>
The	O
single	O
channel	O
dry	O
EEG	B-Application
electrode	O
construction	O
and	O
results	O
were	O
published	O
in	O
1994	O
.	O
</s>
<s>
The	O
advantages	O
of	O
such	O
electrodes	O
are	O
:	O
(	O
1	O
)	O
no	O
electrolyte	O
used	O
,	O
(	O
2	O
)	O
no	O
skin	O
preparation	O
,	O
(	O
3	O
)	O
significantly	O
reduced	O
sensor	O
size	O
,	O
and	O
(	O
4	O
)	O
compatibility	O
with	O
EEG	B-Application
monitoring	O
systems	O
.	O
</s>
<s>
The	O
electrode	O
was	O
tested	O
on	O
an	O
electrical	O
test	O
bench	O
and	O
on	O
human	O
subjects	O
in	O
four	O
modalities	O
of	O
EEG	B-Application
activity	O
,	O
namely	O
:	O
(	O
1	O
)	O
spontaneous	O
EEG	B-Application
,	O
(	O
2	O
)	O
sensory	O
event-related	B-Algorithm
potentials	I-Algorithm
,	O
(	O
3	O
)	O
brain	O
stem	O
potentials	O
,	O
and	O
(	O
4	O
)	O
cognitive	O
event-related	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
In	O
1999	O
researchers	O
at	O
Case	O
Western	O
Reserve	O
University	O
,	O
in	O
Cleveland	O
,	O
Ohio	O
,	O
led	O
by	O
Hunter	O
Peckham	O
,	O
used	O
64-electrode	O
EEG	B-Application
skullcap	O
to	O
return	O
limited	O
hand	O
movements	O
to	O
quadriplegic	O
Jim	O
Jatich	O
.	O
</s>
<s>
As	O
Jatich	O
concentrated	O
on	O
simple	O
but	O
opposite	O
concepts	O
like	O
up	O
and	O
down	O
,	O
his	O
beta-rhythm	O
EEG	B-Application
output	O
was	O
analysed	O
using	O
software	O
to	O
identify	O
patterns	O
in	O
the	O
noise	O
.	O
</s>
<s>
EEG	B-Application
technology	O
often	O
involves	O
applying	O
a	O
gel	O
to	O
the	O
scalp	O
which	O
facilitates	O
strong	O
signal-to-noise	O
ratio	O
.	O
</s>
<s>
Since	O
patients	O
dislike	O
having	O
their	O
hair	O
filled	O
with	O
gel	O
,	O
and	O
the	O
lengthy	O
setup	O
requires	O
trained	O
staff	O
on	O
hand	O
,	O
utilizing	O
EEG	B-Application
outside	O
the	O
laboratory	O
setting	O
can	O
be	O
difficult	O
.	O
</s>
<s>
Therefore	O
,	O
research	O
has	O
been	O
directed	O
to	O
developing	O
dry	O
and	O
semi-dry	O
EEG	B-Application
bioelectronic	O
interfaces	O
.	O
</s>
<s>
Some	O
EEG	B-Application
systems	O
attempt	O
to	O
circumvent	O
this	O
issue	O
by	O
applying	O
a	O
saline	O
solution	O
.	O
</s>
<s>
ARL	O
also	O
developed	O
a	O
visualization	O
tool	O
,	O
Customizable	O
Lighting	O
Interface	O
for	O
the	O
Visualization	O
of	O
EEGs	B-Application
or	O
CLIVE	O
,	O
which	O
showed	O
how	O
well	O
two	O
brains	O
are	O
synchronized	O
.	O
</s>
<s>
EEG	B-Application
has	O
several	O
limitations	O
.	O
</s>
<s>
EEG	B-Application
is	O
most	O
sensitive	O
to	O
a	O
particular	O
set	O
of	O
post-synaptic	B-Algorithm
potentials	I-Algorithm
:	O
those	O
generated	O
in	O
superficial	O
layers	O
of	O
the	O
cortex	O
,	O
on	O
the	O
crests	O
of	O
gyri	O
directly	O
abutting	O
the	O
skull	O
and	O
radial	O
to	O
the	O
skull	O
.	O
</s>
<s>
Dendrites	O
,	O
which	O
are	O
deeper	O
in	O
the	O
cortex	O
,	O
inside	O
sulci	O
,	O
in	O
midline	O
or	O
deep	O
structures	O
(	O
such	O
as	O
the	O
cingulate	O
gyrus	O
or	O
hippocampus	O
)	O
,	O
or	O
producing	O
currents	O
that	O
are	O
tangential	O
to	O
the	O
skull	O
,	O
have	O
far	O
less	O
contribution	O
to	O
the	O
EEG	B-Application
signal	O
.	O
</s>
<s>
EEG	B-Application
recordings	O
do	O
not	O
directly	O
capture	O
axonal	O
action	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
An	O
action	B-Algorithm
potential	I-Algorithm
can	O
be	O
accurately	O
represented	O
as	O
a	O
current	O
quadrupole	O
,	O
meaning	O
that	O
the	O
resulting	O
field	O
decreases	O
more	O
rapidly	O
than	O
the	O
ones	O
produced	O
by	O
the	O
current	O
dipole	O
of	O
post-synaptic	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
In	O
addition	O
,	O
since	O
EEGs	B-Application
represent	O
averages	O
of	O
thousands	O
of	O
neurons	O
,	O
a	O
large	O
population	O
of	O
cells	O
in	O
synchronous	B-Algorithm
activity	I-Algorithm
is	O
necessary	O
to	O
cause	O
a	O
significant	O
deflection	O
on	O
the	O
recordings	O
.	O
</s>
<s>
Action	B-Algorithm
potentials	I-Algorithm
are	O
very	O
fast	O
and	O
,	O
as	O
a	O
consequence	O
,	O
the	O
chances	O
of	O
field	O
summation	O
are	O
slim	O
.	O
</s>
<s>
However	O
,	O
neural	O
backpropagation	O
,	O
as	O
a	O
typically	O
longer	O
dendritic	O
current	O
dipole	O
,	O
can	O
be	O
picked	O
up	O
by	O
EEG	B-Application
electrodes	O
and	O
is	O
a	O
reliable	O
indication	O
of	O
the	O
occurrence	O
of	O
neural	O
output	O
.	O
</s>
<s>
Not	O
only	O
do	O
EEGs	B-Application
capture	O
dendritic	O
currents	O
almost	O
exclusively	O
as	O
opposed	O
to	O
axonal	O
currents	O
,	O
they	O
also	O
show	O
a	O
preference	O
for	O
activity	O
on	O
populations	O
of	O
parallel	O
dendrites	O
and	O
transmitting	O
current	O
in	O
the	O
same	O
direction	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
Pyramidal	O
neurons	O
of	O
cortical	O
layers	O
II/III	O
and	O
V	O
extend	O
apical	O
dendrites	O
to	O
layer	O
I	O
.	O
Currents	O
moving	O
up	O
or	O
down	O
these	O
processes	O
underlie	O
most	O
of	O
the	O
signals	O
produced	O
by	O
electroencephalography	B-Application
.	O
</s>
<s>
Therefore	O
,	O
EEG	B-Application
provides	O
information	O
with	O
a	O
large	O
bias	O
to	O
select	O
neuron	O
types	O
,	O
and	O
generally	O
should	O
not	O
be	O
used	O
to	O
make	O
claims	O
about	O
global	O
brain	B-Application
activity	I-Application
.	O
</s>
<s>
The	O
meninges	O
,	O
cerebrospinal	O
fluid	O
and	O
skull	O
"	O
smear	O
"	O
the	O
EEG	B-Application
signal	O
,	O
obscuring	O
its	O
intracranial	O
source	O
.	O
</s>
<s>
It	O
is	O
mathematically	O
impossible	O
to	O
reconstruct	O
a	O
unique	O
intracranial	O
current	O
source	O
for	O
a	O
given	O
EEG	B-Application
signal	O
,	O
as	O
some	O
currents	O
produce	O
potentials	O
that	O
cancel	O
each	O
other	O
out	O
.	O
</s>
<s>
EEG	B-Application
has	O
several	O
strong	O
points	O
as	O
a	O
tool	O
for	O
exploring	O
brain	B-Application
activity	I-Application
.	O
</s>
<s>
EEGs	B-Application
can	O
detect	O
changes	O
over	O
milliseconds	O
,	O
which	O
is	O
excellent	O
considering	O
an	O
action	B-Algorithm
potential	I-Algorithm
takes	O
approximately	O
0.5	O
–	O
130	O
milliseconds	O
to	O
propagate	O
across	O
a	O
single	O
neuron	O
,	O
depending	O
on	O
the	O
type	O
of	O
neuron	O
.	O
</s>
<s>
Other	O
methods	O
of	O
looking	O
at	O
brain	B-Application
activity	I-Application
,	O
such	O
as	O
PET	B-Application
,	O
fMRI	B-Algorithm
or	O
fUS	B-Algorithm
have	O
time	O
resolution	O
between	O
seconds	O
and	O
minutes	O
.	O
</s>
<s>
EEG	B-Application
measures	O
the	O
brain	O
's	O
electrical	O
activity	O
directly	O
,	O
while	O
other	O
methods	O
record	O
changes	O
in	O
blood	O
flow	O
(	O
e.g.	O
,	O
SPECT	O
,	O
fMRI	B-Algorithm
,	O
fUS	B-Algorithm
)	O
or	O
metabolic	O
activity	O
(	O
e.g.	O
,	O
PET	B-Application
,	O
NIRS	B-Algorithm
)	O
,	O
which	O
are	O
indirect	O
markers	O
of	O
brain	O
electrical	O
activity	O
.	O
</s>
<s>
EEG	B-Application
can	O
be	O
used	O
simultaneously	O
with	O
fMRI	B-Algorithm
or	O
fUS	B-Algorithm
so	O
that	O
high-temporal-resolution	O
data	O
can	O
be	O
recorded	O
at	O
the	O
same	O
time	O
as	O
high-spatial-resolution	O
data	O
,	O
however	O
,	O
since	O
the	O
data	O
derived	O
from	O
each	O
occurs	O
over	O
a	O
different	O
time	O
course	O
,	O
the	O
data	O
sets	O
do	O
not	O
necessarily	O
represent	O
exactly	O
the	O
same	O
brain	B-Application
activity	I-Application
.	O
</s>
<s>
There	O
are	O
technical	O
difficulties	O
associated	O
with	O
combining	O
EEG	B-Application
and	O
fMRI	B-Algorithm
including	O
the	O
need	O
to	O
remove	O
the	O
MRI	O
gradient	O
artifact	O
present	O
during	O
MRI	O
acquisition	O
.	O
</s>
<s>
Furthermore	O
,	O
currents	O
can	O
be	O
induced	O
in	O
moving	O
EEG	B-Application
electrode	O
wires	O
due	O
to	O
the	O
magnetic	O
field	O
of	O
the	O
MRI	O
.	O
</s>
<s>
EEG	B-Application
can	O
be	O
used	O
simultaneously	O
with	O
NIRS	B-Algorithm
or	O
fUS	B-Algorithm
without	O
major	O
technical	O
difficulties	O
.	O
</s>
<s>
EEG	B-Application
reflects	O
correlated	O
synaptic	O
activity	O
caused	O
by	O
post-synaptic	B-Algorithm
potentials	I-Algorithm
of	O
cortical	O
neurons	O
.	O
</s>
<s>
The	O
ionic	O
currents	O
involved	O
in	O
the	O
generation	O
of	O
fast	O
action	B-Algorithm
potentials	I-Algorithm
may	O
not	O
contribute	O
greatly	O
to	O
the	O
averaged	O
field	B-Algorithm
potentials	I-Algorithm
representing	O
the	O
EEG	B-Application
.	O
</s>
<s>
More	O
specifically	O
,	O
the	O
scalp	O
electrical	O
potentials	O
that	O
produce	O
EEG	B-Application
are	O
generally	O
thought	O
to	O
be	O
caused	O
by	O
the	O
extracellular	O
ionic	O
currents	O
caused	O
by	O
dendritic	O
electrical	O
activity	O
,	O
whereas	O
the	O
fields	O
producing	O
magnetoencephalographic	B-Algorithm
signals	O
are	O
associated	O
with	O
intracellular	O
ionic	O
currents	O
.	O
</s>
<s>
The	O
EEG	B-Application
is	O
typically	O
described	O
in	O
terms	O
of	O
(	O
1	O
)	O
rhythmic	B-Algorithm
activity	I-Algorithm
and	O
(	O
2	O
)	O
transients	O
.	O
</s>
<s>
The	O
rhythmic	B-Algorithm
activity	I-Algorithm
is	O
divided	O
into	O
bands	O
by	O
frequency	O
.	O
</s>
<s>
To	O
some	O
degree	O
,	O
these	O
frequency	O
bands	O
are	O
a	O
matter	O
of	O
nomenclature	O
(	O
i.e.	O
,	O
any	O
rhythmic	B-Algorithm
activity	I-Algorithm
between	O
8	O
–	O
12Hz	O
can	O
be	O
described	O
as	O
"	O
alpha	B-Application
"	O
)	O
,	O
but	O
these	O
designations	O
arose	O
because	O
rhythmic	B-Algorithm
activity	I-Algorithm
within	O
a	O
certain	O
frequency	O
range	O
was	O
noted	O
to	O
have	O
a	O
certain	O
distribution	O
over	O
the	O
scalp	O
or	O
a	O
certain	O
biological	O
significance	O
.	O
</s>
<s>
Frequency	O
bands	O
are	O
usually	O
extracted	O
using	O
spectral	O
methods	O
(	O
for	O
instance	O
Welch	O
)	O
as	O
implemented	O
for	O
instance	O
in	O
freely	O
available	O
EEG	B-Application
software	O
such	O
as	O
EEGLAB	B-Algorithm
or	O
the	O
Neurophysiological	B-Algorithm
Biomarker	I-Algorithm
Toolbox	I-Algorithm
.	O
</s>
<s>
Computational	O
processing	O
of	O
the	O
EEG	B-Application
is	O
often	O
named	O
quantitative	B-Algorithm
electroencephalography	I-Algorithm
(	O
qEEG	B-Algorithm
)	O
.	O
</s>
<s>
Most	O
of	O
the	O
cerebral	O
signal	O
observed	O
in	O
the	O
scalp	O
EEG	B-Application
falls	O
in	O
the	O
range	O
of	O
1	O
–	O
20Hz	O
(	O
activity	O
below	O
or	O
above	O
this	O
range	O
is	O
likely	O
to	O
be	O
artifactual	O
,	O
under	O
standard	O
clinical	O
recording	O
techniques	O
)	O
.	O
</s>
<s>
Waveforms	O
are	O
subdivided	O
into	O
bandwidths	O
known	O
as	O
alpha	B-Application
,	O
beta	B-Algorithm
,	O
theta	B-Algorithm
,	O
and	O
delta	B-Algorithm
to	O
signify	O
the	O
majority	O
of	O
the	O
EEG	B-Application
used	O
in	O
clinical	O
practice	O
.	O
</s>
<s>
Associated	O
with	O
inhibition	O
of	O
elicited	O
responses	O
(	O
has	O
been	O
found	O
to	O
spike	B-Algorithm
in	O
situations	O
where	O
a	O
person	O
is	O
actively	O
trying	O
to	O
repress	O
a	O
response	O
or	O
action	O
)	O
.	O
</s>
<s>
Also	O
is	O
shown	O
during	O
short-term	O
memory	O
matching	O
of	O
recognized	O
objects	O
,	O
sounds	O
,	O
or	O
tactile	O
sensations	O
A	O
decrease	O
in	O
gamma-band	O
activity	O
may	O
be	O
associated	O
with	O
cognitive	O
decline	O
,	O
especially	O
when	O
related	O
to	O
the	O
theta	B-Algorithm
band	O
;	O
however	O
,	O
this	O
has	O
not	O
been	O
proven	O
for	O
use	O
as	O
a	O
clinical	O
diagnostic	O
measurement	O
Mu8	O
–	O
12	O
Sensorimotor	O
cortex	O
Shows	O
rest-state	O
motor	O
neurons	O
.	O
</s>
<s>
Mu	B-Algorithm
suppression	O
could	O
indicate	O
that	O
motor	O
mirror	O
neurons	O
are	O
working	O
.	O
</s>
<s>
Deficits	O
in	O
Mu	B-Algorithm
suppression	O
,	O
and	O
thus	O
in	O
mirror	O
neurons	O
,	O
might	O
play	O
a	O
role	O
in	O
autism	O
.	O
</s>
<s>
Unfortunately	O
there	O
is	O
no	O
agreement	O
in	O
standard	O
reference	O
works	O
on	O
what	O
these	O
ranges	O
should	O
be	O
–	O
values	O
for	O
the	O
upper	O
end	O
of	O
alpha	B-Application
and	O
lower	O
end	O
of	O
beta	B-Algorithm
include	O
12	O
,	O
13	O
,	O
14	O
and	O
15	O
.	O
</s>
<s>
If	O
the	O
threshold	O
is	O
taken	O
as	O
14Hz	O
,	O
then	O
the	O
slowest	O
beta	B-Algorithm
wave	I-Algorithm
has	O
about	O
the	O
same	O
duration	O
as	O
the	O
longest	O
spike	B-Algorithm
(	O
70ms	O
)	O
,	O
which	O
makes	O
this	O
the	O
most	O
useful	O
value	O
.	O
</s>
<s>
Delta	B-Algorithm
waves	I-Algorithm
is	O
the	O
frequency	O
range	O
up	O
to	O
4Hz	O
.	O
</s>
<s>
FIRDA	O
–	O
frontal	O
intermittent	O
rhythmic	O
delta	B-Algorithm
)	O
and	O
posteriorly	O
in	O
children	O
(	O
e.g.	O
</s>
<s>
OIRDA	O
–	O
occipital	O
intermittent	O
rhythmic	O
delta	B-Algorithm
)	O
.	O
</s>
<s>
Theta	B-Algorithm
is	O
the	O
frequency	O
range	O
from	O
4Hz	O
to	O
7Hz	O
.	O
</s>
<s>
Theta	B-Algorithm
is	O
seen	O
normally	O
in	O
young	O
children	O
.	O
</s>
<s>
Excess	O
theta	B-Algorithm
for	O
age	O
represents	O
abnormal	O
activity	O
.	O
</s>
<s>
Alpha	B-Application
is	O
the	O
frequency	O
range	O
from	O
8	O
Hz	O
to	O
12Hz	O
.	O
</s>
<s>
Hans	O
Berger	O
named	O
the	O
first	O
rhythmic	O
EEG	B-Application
activity	O
he	O
observed	O
the	O
"	O
alpha	B-Application
wave	O
"	O
.	O
</s>
<s>
This	O
was	O
the	O
"	O
posterior	O
basic	O
rhythm	O
"	O
(	O
also	O
called	O
the	O
"	O
posterior	O
dominant	O
rhythm	O
"	O
or	O
the	O
"	O
posterior	O
alpha	B-Application
rhythm	O
"	O
)	O
,	O
seen	O
in	O
the	O
posterior	O
regions	O
of	O
the	O
head	O
on	O
both	O
sides	O
,	O
higher	O
in	O
amplitude	O
on	O
the	O
dominant	O
side	O
.	O
</s>
<s>
The	O
posterior	O
basic	O
rhythm	O
is	O
actually	O
slower	O
than	O
8Hz	O
in	O
young	O
children	O
(	O
therefore	O
technically	O
in	O
the	O
theta	B-Algorithm
range	O
)	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
posterior	O
basic	O
rhythm	O
,	O
there	O
are	O
other	O
normal	O
alpha	B-Application
rhythms	O
such	O
as	O
the	O
mu	B-Algorithm
rhythm	I-Algorithm
(	O
alpha	B-Application
activity	O
in	O
the	O
contralateral	O
sensory	O
and	O
motor	O
cortical	O
areas	O
)	O
that	O
emerges	O
when	O
the	O
hands	O
and	O
arms	O
are	O
idle	O
;	O
and	O
the	O
"	O
third	O
rhythm	O
"	O
(	O
alpha	B-Application
activity	O
in	O
the	O
temporal	O
or	O
frontal	O
lobes	O
)	O
.	O
</s>
<s>
Alpha	B-Application
can	O
be	O
abnormal	O
;	O
for	O
example	O
,	O
an	O
EEG	B-Application
that	O
has	O
diffuse	O
alpha	B-Application
occurring	O
in	O
coma	O
and	O
is	O
not	O
responsive	O
to	O
external	O
stimuli	O
is	O
referred	O
to	O
as	O
"	O
alpha	B-Application
coma	O
"	O
.	O
</s>
<s>
Beta	B-Algorithm
is	O
the	O
frequency	O
range	O
from	O
13Hz	O
to	O
about	O
30Hz	O
.	O
</s>
<s>
Beta	B-Algorithm
activity	O
is	O
closely	O
linked	O
to	O
motor	O
behavior	O
and	O
is	O
generally	O
attenuated	O
during	O
active	O
movements	O
.	O
</s>
<s>
Low-amplitude	O
beta	B-Algorithm
with	O
multiple	O
and	O
varying	O
frequencies	O
is	O
often	O
associated	O
with	O
active	O
,	O
busy	O
or	O
anxious	O
thinking	O
and	O
active	O
concentration	O
.	O
</s>
<s>
Rhythmic	O
beta	B-Algorithm
with	O
a	O
dominant	O
set	O
of	O
frequencies	O
is	O
associated	O
with	O
various	O
pathologies	O
,	O
such	O
as	O
Dup15q	O
syndrome	O
,	O
and	O
drug	O
effects	O
,	O
especially	O
benzodiazepines	O
.	O
</s>
<s>
Gamma	B-Algorithm
is	O
the	O
frequency	O
range	O
approximately	O
30	O
–	O
100Hz	O
.	O
</s>
<s>
Gamma	B-Algorithm
rhythms	I-Algorithm
are	O
thought	O
to	O
represent	O
binding	O
of	O
different	O
populations	O
of	O
neurons	O
together	O
into	O
a	O
network	O
for	O
the	O
purpose	O
of	O
carrying	O
out	O
a	O
certain	O
cognitive	O
or	O
motor	O
function	O
.	O
</s>
<s>
Mu	B-Algorithm
range	O
is	O
8	O
–	O
13Hz	O
and	O
partly	O
overlaps	O
with	O
other	O
frequencies	O
.	O
</s>
<s>
Mu	B-Algorithm
suppression	O
is	O
thought	O
to	O
reflect	O
motor	O
mirror	O
neuron	O
systems	O
,	O
because	O
when	O
an	O
action	O
is	O
observed	O
,	O
the	O
pattern	O
extinguishes	O
,	O
possibly	O
because	O
the	O
normal	O
and	O
mirror	O
neuronal	O
systems	O
"	O
go	O
out	O
of	O
sync	O
"	O
and	O
interfere	O
with	O
one	O
other	O
.	O
</s>
<s>
Some	O
features	O
of	O
the	O
EEG	B-Application
are	O
transient	O
rather	O
than	O
rhythmic	O
.	O
</s>
<s>
Spikes	B-Algorithm
and	O
sharp	O
waves	O
may	O
represent	O
seizure	O
activity	O
or	O
interictal	O
activity	O
in	O
individuals	O
with	O
epilepsy	O
or	O
a	O
predisposition	O
toward	O
epilepsy	O
.	O
</s>
<s>
Other	O
transient	O
features	O
are	O
normal	O
:	O
vertex	O
waves	O
and	O
sleep	B-Algorithm
spindles	I-Algorithm
are	O
seen	O
in	O
normal	O
sleep	O
.	O
</s>
<s>
The	O
mu	B-Algorithm
rhythm	I-Algorithm
is	O
an	O
example	O
of	O
a	O
normal	O
variant	O
.	O
</s>
<s>
The	O
normal	O
electroencephalogram	B-Application
(	O
EEG	B-Application
)	O
varies	O
by	O
age	O
.	O
</s>
<s>
The	O
prenatal	B-Algorithm
EEG	I-Algorithm
and	O
neonatal	O
EEG	B-Application
is	O
quite	O
different	O
from	O
the	O
adult	O
EEG	B-Application
.	O
</s>
<s>
Fetuses	O
in	O
the	O
third	O
trimester	O
and	O
newborns	O
display	O
two	O
common	O
brain	B-Application
activity	I-Application
patterns	O
:	O
"	O
discontinuous	O
"	O
and	O
"	O
trace	O
alternant.	O
"	O
</s>
<s>
The	O
EEG	B-Application
in	O
childhood	O
generally	O
has	O
slower	O
frequency	O
oscillations	B-Algorithm
than	O
the	O
adult	O
EEG	B-Application
.	O
</s>
<s>
The	O
normal	O
EEG	B-Application
also	O
varies	O
depending	O
on	O
state	O
.	O
</s>
<s>
The	O
EEG	B-Application
is	O
used	O
along	O
with	O
other	O
measurements	O
(	O
EOG	O
,	O
EMG	O
)	O
to	O
define	O
sleep	O
stages	O
in	O
polysomnography	O
.	O
</s>
<s>
Stage	O
I	O
sleep	O
(	O
equivalent	O
to	O
drowsiness	O
in	O
some	O
systems	O
)	O
appears	O
on	O
the	O
EEG	B-Application
as	O
drop-out	O
of	O
the	O
posterior	O
basic	O
rhythm	O
.	O
</s>
<s>
There	O
can	O
be	O
an	O
increase	O
in	O
theta	B-Algorithm
frequencies	O
.	O
</s>
<s>
Stage	O
II	O
sleep	O
is	O
characterized	O
by	O
sleep	B-Algorithm
spindles	I-Algorithm
–	O
transient	O
runs	O
of	O
rhythmic	B-Algorithm
activity	I-Algorithm
in	O
the	O
12	O
–	O
14Hz	O
range	O
(	O
sometimes	O
referred	O
to	O
as	O
the	O
"	O
sigma	O
"	O
band	O
)	O
that	O
have	O
a	O
frontal-central	O
maximum	O
.	O
</s>
<s>
Stage	O
III	O
and	O
IV	O
sleep	O
are	O
defined	O
by	O
the	O
presence	O
of	O
delta	B-Algorithm
frequencies	O
and	O
are	O
often	O
referred	O
to	O
collectively	O
as	O
"	O
slow-wave	O
sleep	O
"	O
.	O
</s>
<s>
The	O
EEG	B-Application
in	O
REM	O
(	O
rapid	O
eye	O
movement	O
)	O
sleep	O
appears	O
somewhat	O
similar	O
to	O
the	O
awake	O
EEG	B-Application
.	O
</s>
<s>
EEG	B-Application
under	O
general	O
anesthesia	O
depends	O
on	O
the	O
type	O
of	O
anesthetic	O
employed	O
.	O
</s>
<s>
With	O
halogenated	O
anesthetics	O
,	O
such	O
as	O
halothane	O
or	O
intravenous	O
agents	O
,	O
such	O
as	O
propofol	O
,	O
a	O
rapid	O
(	O
alpha	B-Application
or	O
low	O
beta	B-Algorithm
)	O
,	O
nonreactive	O
EEG	B-Application
pattern	O
is	O
seen	O
over	O
most	O
of	O
the	O
scalp	O
,	O
especially	O
anteriorly	O
;	O
in	O
some	O
older	O
terminology	O
this	O
was	O
known	O
as	O
a	O
WAR	O
(	O
widespread	O
anterior	O
rapid	O
)	O
pattern	O
,	O
contrasted	O
with	O
a	O
WAIS	O
(	O
widespread	O
slow	O
)	O
pattern	O
associated	O
with	O
high	O
doses	O
of	O
opiates	O
.	O
</s>
<s>
Anesthetic	O
effects	O
on	O
EEG	B-Application
signals	O
are	O
beginning	O
to	O
be	O
understood	O
at	O
the	O
level	O
of	O
drug	O
actions	O
on	O
different	O
kinds	O
of	O
synapses	O
and	O
the	O
circuits	O
that	O
allow	O
synchronized	O
neuronal	O
activity	O
.	O
</s>
<s>
EEG	B-Application
is	O
an	O
extremely	O
useful	O
technique	O
for	O
studying	O
brain	B-Application
activity	I-Application
,	O
but	O
the	O
signal	O
measured	O
is	O
always	O
contaminated	O
by	O
artifacts	O
which	O
can	O
impact	O
the	O
analysis	O
of	O
the	O
data	O
.	O
</s>
<s>
Artifacts	O
may	O
bias	O
the	O
visual	O
interpretation	O
of	O
EEG	B-Application
data	O
as	O
some	O
may	O
mimic	O
cognitive	O
activity	O
that	O
could	O
affect	O
diagnoses	O
of	O
problems	O
such	O
as	O
Alzheimer	O
's	O
disease	O
or	O
sleep	O
disorders	O
.	O
</s>
<s>
As	O
such	O
the	O
removal	O
of	O
such	O
artifacts	O
in	O
EEG	B-Application
data	O
used	O
for	O
practical	O
applications	O
is	O
of	O
the	O
upmost	O
importance	O
.	O
</s>
<s>
It	O
is	O
important	O
to	O
be	O
able	O
to	O
distinguish	O
artifacts	O
from	O
genuine	O
brain	B-Application
activity	I-Application
in	O
order	O
to	O
prevent	O
incorrect	O
interpretations	O
of	O
EEG	B-Application
data	O
.	O
</s>
<s>
The	O
goal	O
of	O
any	O
approach	O
is	O
to	O
develop	O
methodology	O
capable	O
of	O
identifying	O
and	O
removing	O
artifacts	O
without	O
affecting	O
the	O
quality	O
of	O
the	O
EEG	B-Application
signal	O
.	O
</s>
<s>
However	O
such	O
simple	O
filters	O
are	O
not	O
an	O
appropriate	O
choice	O
for	O
dealing	O
with	O
all	O
artifacts	O
,	O
as	O
for	O
some	O
,	O
their	O
frequencies	O
will	O
overlap	O
with	O
the	O
EEG	B-Application
frequencies	O
.	O
</s>
<s>
Blind	O
source	O
separation	O
(	O
BSS	O
)	O
algorithms	O
employed	O
to	O
remove	O
artifacts	O
include	O
principal	B-Application
component	I-Application
analysis	I-Application
(	O
PCA	O
)	O
and	O
independent	B-Algorithm
component	I-Algorithm
analysis	I-Algorithm
(	O
ICA	O
)	O
and	O
several	O
algorithms	O
in	O
the	O
this	O
class	O
have	O
been	O
successful	O
at	O
tackling	O
most	O
physiological	O
artifacts	O
.	O
</s>
<s>
The	O
method	O
is	O
called	O
wavelet	O
quantil	O
normalization	O
WQN	O
and	O
can	O
be	O
used	O
in	O
real-time	O
to	O
remove	O
artifacts	O
on	O
EEG	B-Application
sedline	O
monitor	O
.	O
</s>
<s>
Ocular	O
artifacts	O
affect	O
the	O
EEG	B-Application
signal	O
significantly	O
.	O
</s>
<s>
This	O
is	O
due	O
to	O
eye	O
movements	O
involving	O
a	O
change	O
in	O
electric	O
fields	O
surrounding	O
the	O
eyes	O
,	O
distorting	O
the	O
electric	O
field	O
over	O
the	O
scalp	O
,	O
and	O
as	O
EEG	B-Application
is	O
recorded	O
on	O
the	O
scalp	O
,	O
it	O
therefore	O
distorts	O
the	O
recorded	O
signal	O
.	O
</s>
<s>
It	O
is	O
thought	O
that	O
the	O
eyelid	O
can	O
be	O
described	O
as	O
a	O
sliding	O
potential	O
source	O
and	O
that	O
the	O
impacting	O
of	O
blinking	O
is	O
different	O
to	O
eye	O
movement	O
on	O
the	O
recorded	O
EEG	B-Application
.	O
</s>
<s>
Eyelid	O
fluttering	O
artifacts	O
of	O
a	O
characteristic	O
type	O
were	O
previously	O
called	O
Kappa	B-Application
rhythm	I-Application
(	O
or	O
Kappa	O
waves	O
)	O
.	O
</s>
<s>
They	O
are	O
usually	O
in	O
the	O
Theta	B-Algorithm
(	O
4	O
–	O
7Hz	O
)	O
or	O
Alpha	B-Application
(	O
7	O
–	O
14Hz	O
)	O
range	O
.	O
</s>
<s>
They	O
are	O
in	O
fact	O
noise	O
in	O
the	O
EEG	B-Application
reading	O
,	O
and	O
should	O
not	O
technically	O
be	O
called	O
a	O
rhythm	O
or	O
wave	O
.	O
</s>
<s>
Therefore	O
,	O
current	O
usage	O
in	O
electroencephalography	B-Application
refers	O
to	O
the	O
phenomenon	O
as	O
an	O
eyelid	O
fluttering	O
artifact	O
,	O
rather	O
than	O
a	O
Kappa	B-Application
rhythm	I-Application
(	O
or	O
wave	O
)	O
.	O
</s>
<s>
The	O
electrooculogram	O
(	O
EOG	O
)	O
consists	O
of	O
a	O
series	O
of	O
electrodes	O
measuring	O
voltage	O
changes	O
close	O
to	O
the	O
eye	O
and	O
is	O
the	O
most	O
common	O
tool	O
for	O
dealing	O
with	O
the	O
eye	O
movement	O
artifact	O
in	O
the	O
EEG	B-Application
signal	O
.	O
</s>
<s>
The	O
frequency	O
range	O
for	O
muscular	O
artifacts	O
is	O
wide	O
and	O
overlaps	O
with	O
every	O
classic	O
EEG	B-Application
rhythm	O
.	O
</s>
<s>
However	O
most	O
of	O
the	O
power	O
is	O
concentrated	O
in	O
the	O
lower	O
range	O
of	O
the	O
observed	O
frequencies	O
of	O
20	O
to	O
300Hz	O
making	O
the	O
gamma	B-Algorithm
band	O
particularly	O
susceptible	O
to	O
muscular	O
artifacts	O
.	O
</s>
<s>
Some	O
muscle	O
artifacts	O
may	O
have	O
activity	O
with	O
a	O
frequency	O
as	O
low	O
as	O
2Hz	O
which	O
and	O
delta	B-Algorithm
and	O
theta	B-Algorithm
bands	O
may	O
also	O
be	O
affected	O
by	O
muscle	O
activity	O
.	O
</s>
<s>
Muscular	O
artifacts	O
may	O
impact	O
sleep	O
studies	O
as	O
unconscious	O
bruxism	O
(	O
grinding	O
of	O
teeth	O
)	O
or	O
snoring	O
can	O
seriously	O
impact	O
the	O
quality	O
of	O
the	O
recorded	O
EEG	B-Application
.	O
</s>
<s>
The	O
potential	O
due	O
to	O
cardiac	O
activity	O
introduces	O
electrocardiograph	B-Application
(	O
ECG	B-Application
)	O
errors	O
in	O
the	O
EEG	B-Application
.	O
</s>
<s>
Artifacts	O
arising	O
due	O
to	O
cardiac	O
activity	O
may	O
be	O
removed	O
with	O
the	O
help	O
of	O
an	O
ECG	B-Application
reference	O
signal	O
.	O
</s>
<s>
Minor	O
tongue	O
movements	O
can	O
contaminate	O
the	O
EEG	B-Application
,	O
especially	O
in	O
parkinsonian	O
and	O
tremor	B-Application
disorders	O
.	O
</s>
<s>
Movement	O
by	O
the	O
patient	O
,	O
or	O
even	O
just	O
settling	O
of	O
the	O
electrodes	O
,	O
may	O
cause	O
electrode	O
pops	O
,	O
spikes	B-Algorithm
originating	O
from	O
a	O
momentary	O
change	O
in	O
the	O
impedance	O
of	O
a	O
given	O
electrode	O
.	O
</s>
<s>
Poor	O
grounding	O
of	O
the	O
EEG	B-Application
electrodes	O
can	O
cause	O
significant	O
50	O
or	O
60Hz	O
artifact	O
,	O
depending	O
on	O
the	O
local	O
power	O
system	O
's	O
frequency	O
.	O
</s>
<s>
A	O
third	O
source	O
of	O
possible	O
interference	O
can	O
be	O
the	O
presence	O
of	O
an	O
IV	O
drip	O
;	O
such	O
devices	O
can	O
cause	O
rhythmic	O
,	O
fast	O
,	O
low-voltage	O
bursts	O
,	O
which	O
may	O
be	O
confused	O
for	O
spikes	B-Algorithm
.	O
</s>
<s>
It	O
may	O
also	O
appear	O
as	O
focal	O
or	O
unilateral	O
decrease	O
in	O
amplitude	O
of	O
the	O
EEG	B-Application
signal	O
.	O
</s>
<s>
Intracortical	O
Encephalogram	B-Application
electrodes	O
and	O
sub-dural	O
electrodes	O
can	O
be	O
used	O
in	O
tandem	O
to	O
discriminate	O
and	O
discretize	O
artifact	O
from	O
epileptiform	O
and	O
other	O
severe	O
neurological	O
events	O
.	O
</s>
<s>
More	O
advanced	O
measures	O
of	O
abnormal	O
EEG	B-Application
signals	O
have	O
also	O
recently	O
received	O
attention	O
as	O
possible	O
biomarkers	O
for	O
different	O
disorders	O
such	O
as	O
Alzheimer	O
's	O
disease	O
.	O
</s>
<s>
Systems	O
for	O
decoding	O
imagined	O
speech	O
from	O
EEG	B-Application
have	O
applications	O
such	O
as	O
in	O
brain	B-Application
–	I-Application
computer	I-Application
interfaces	I-Application
.	O
</s>
<s>
The	O
Department	O
of	O
Defense	O
(	O
DoD	O
)	O
and	O
Veteran	O
's	O
Affairs	O
(	O
VA	O
)	O
,	O
and	O
U.S	O
Army	O
Research	O
Laboratory	O
(	O
ARL	O
)	O
,	O
collaborated	O
on	O
EEG	B-Application
diagnostics	O
in	O
order	O
to	O
detect	O
mild	O
to	O
moderate	O
Traumatic	O
Brain	O
Injury	O
(	O
mTBI	O
)	O
in	O
combat	O
soldiers	O
.	O
</s>
<s>
Both	O
conditions	O
present	O
with	O
altered	O
low-frequency	O
brain	B-Algorithm
wave	I-Algorithm
oscillations	B-Algorithm
.	O
</s>
<s>
Altered	O
brain	B-Algorithm
waves	I-Algorithm
from	O
PTSD	O
patients	O
present	O
with	O
decreases	O
in	O
low-frequency	O
oscillations	B-Algorithm
,	O
whereas	O
,	O
mTBI	O
injuries	O
are	O
linked	O
to	O
increased	O
low-frequency	O
wave	O
oscillations	B-Algorithm
.	O
</s>
<s>
Effective	O
EEG	B-Application
diagnostics	O
can	O
help	O
doctors	O
accurately	O
identify	O
conditions	O
and	O
appropriately	O
treat	O
injuries	O
in	O
order	O
to	O
mitigate	O
long-term	O
effects	O
.	O
</s>
<s>
Traditionally	O
,	O
clinical	O
evaluation	O
of	O
EEGs	B-Application
involved	O
visual	O
inspection	O
.	O
</s>
<s>
Instead	O
of	O
a	O
visual	O
assessment	O
of	O
brain	B-Algorithm
wave	I-Algorithm
oscillation	O
topography	O
,	O
quantitative	B-Algorithm
electroencephalography	I-Algorithm
(	O
qEEG	B-Algorithm
)	O
,	O
computerized	O
algorithmic	O
methodologies	O
,	O
analyzes	O
a	O
specific	O
region	O
of	O
the	O
brain	O
and	O
transforms	O
the	O
data	O
into	O
a	O
meaningful	O
"	O
power	O
spectrum	O
"	O
of	O
the	O
area	O
.	O
</s>
<s>
Another	O
common	O
measurement	O
made	O
from	O
EEG	B-Application
data	O
is	O
that	O
of	O
complexity	O
measures	O
such	O
as	O
Lempel-Ziv	O
complexity	O
,	O
fractal	O
dimension	O
,	O
and	O
spectral	O
flatness	O
,	O
which	O
are	O
associated	O
with	O
particular	O
pathologies	O
or	O
pathology	O
stages	O
.	O
</s>
<s>
Inexpensive	O
EEG	B-Application
devices	O
exist	O
for	O
the	O
low-cost	O
research	O
and	O
consumer	O
markets	O
.	O
</s>
<s>
Recently	O
,	O
a	O
few	O
companies	O
have	O
miniaturized	O
medical	O
grade	O
EEG	B-Application
technology	O
to	O
create	O
versions	O
accessible	O
to	O
the	O
general	O
public	O
.	O
</s>
<s>
Some	O
of	O
these	O
companies	O
have	O
built	O
commercial	O
EEG	B-Application
devices	O
retailing	O
for	O
less	O
than	O
US$100	O
.	O
</s>
<s>
In	O
2004	O
OpenEEG	O
released	O
its	O
ModularEEG	O
as	O
open	B-License
source	I-License
hardware	O
.	O
</s>
<s>
Compatible	O
open	B-License
source	I-License
software	O
includes	O
a	O
game	O
for	O
balancing	O
a	O
ball	O
.	O
</s>
<s>
In	O
2007	O
NeuroSky	B-Device
released	O
the	O
first	O
affordable	O
consumer	O
based	O
EEG	B-Application
along	O
with	O
the	O
game	O
NeuroBoy	O
.	O
</s>
<s>
This	O
was	O
also	O
the	O
first	O
large	O
scale	O
EEG	B-Application
device	O
to	O
use	O
dry	O
sensor	O
technology	O
.	O
</s>
<s>
In	O
2008	O
the	O
Final	B-Application
Fantasy	I-Application
developer	O
Square	O
Enix	O
announced	O
that	O
it	O
was	O
partnering	O
with	O
NeuroSky	B-Device
to	O
create	O
a	O
game	O
,	O
Judecca	O
.	O
</s>
<s>
In	O
2009	O
Mattel	O
partnered	O
with	O
NeuroSky	B-Device
to	O
release	O
the	O
Mindflex	O
,	O
a	O
game	O
that	O
used	O
an	O
EEG	B-Application
to	O
steer	O
a	O
ball	O
through	O
an	O
obstacle	O
course	O
.	O
</s>
<s>
By	O
far	O
the	O
best-selling	O
consumer	O
based	O
EEG	B-Application
to	O
date	O
.	O
</s>
<s>
In	O
2009	O
Uncle	O
Milton	O
Industries	O
partnered	O
with	O
NeuroSky	B-Device
to	O
release	O
the	O
Star	B-Application
Wars	I-Application
Force	O
Trainer	O
,	O
a	O
game	O
designed	O
to	O
create	O
the	O
illusion	O
of	O
possessing	O
the	O
Force	O
.	O
</s>
<s>
In	O
2010	O
,	O
NeuroSky	B-Device
added	O
a	O
blink	O
and	O
electromyography	O
function	O
to	O
the	O
MindSet	O
.	O
</s>
<s>
In	O
2011	O
,	O
NeuroSky	B-Device
released	O
the	O
MindWave	O
,	O
an	O
EEG	B-Application
device	O
designed	O
for	O
educational	O
purposes	O
and	O
games	O
.	O
</s>
<s>
The	O
headset	O
is	O
a	O
NeuroSky	B-Device
MindWave	O
unit	O
with	O
two	O
motors	O
on	O
the	O
headband	O
where	O
a	O
cat	O
's	O
ears	O
might	O
be	O
.	O
</s>
<s>
In	O
2014	O
,	O
OpenBCI	B-Algorithm
released	O
an	O
eponymous	O
open	B-License
source	I-License
brain-computer	B-Application
interface	I-Application
after	O
a	O
successful	O
kickstarter	O
campaign	O
in	O
2013	O
.	O
</s>
<s>
The	O
basic	O
OpenBCI	B-Algorithm
has	O
8	O
channels	O
,	O
expandable	O
to	O
16	O
,	O
and	O
supports	O
EEG	B-Application
,	O
EKG	B-Application
,	O
and	O
EMG	O
.	O
</s>
<s>
The	O
OpenBCI	B-Algorithm
is	O
based	O
on	O
the	O
Texas	O
Instruments	O
ADS1299	O
IC	O
and	O
the	O
Arduino	O
or	O
PIC	O
microcontroller	O
,	O
and	O
costs	O
$399	O
for	O
the	O
basic	O
version	O
.	O
</s>
<s>
This	O
device	O
functions	O
as	O
a	O
dry	O
sensor	O
at	O
a	O
size	O
no	O
larger	O
than	O
a	O
Bluetooth	B-Protocol
ear	O
piece	O
.	O
</s>
<s>
In	O
2015	O
,	O
A	O
Chinese-based	O
company	O
Macrotellect	O
released	O
BrainLink	O
Pro	O
and	O
BrainLink	O
Lite	O
,	O
a	O
consumer	O
grade	O
EEG	B-Application
wearable	O
product	O
providing	O
20	O
brain	O
fitness	O
enhancement	O
Apps	O
on	O
Apple	O
and	O
Android	B-Application
App	I-Application
Stores	I-Application
.	O
</s>
<s>
In	O
2021	O
,	O
BioSerenity	O
release	O
the	O
Neuronaute	O
and	O
Icecap	O
a	O
single-use	O
disposable	O
EEG	B-Application
headset	O
that	O
allows	O
recording	O
with	O
equivalent	O
quality	O
to	O
traditional	O
cup	O
electrodes	O
.	O
</s>
<s>
The	O
EEG	B-Application
has	O
been	O
used	O
for	O
many	O
purposes	O
besides	O
the	O
conventional	O
uses	O
of	O
clinical	O
diagnosis	O
and	O
conventional	O
cognitive	O
neuroscience	O
.	O
</s>
<s>
An	O
early	O
use	O
was	O
during	O
World	O
War	O
II	O
by	O
the	O
U.S.	O
Army	O
Air	O
Corps	O
to	O
screen	O
out	O
pilots	O
in	O
danger	O
of	O
having	O
seizures	O
;	O
long-term	O
EEG	B-Application
recordings	O
in	O
epilepsy	O
patients	O
are	O
still	O
used	O
today	O
for	O
seizure	O
prediction	O
.	O
</s>
<s>
Neurofeedback	B-Application
remains	O
an	O
important	O
extension	O
,	O
and	O
in	O
its	O
most	O
advanced	O
form	O
is	O
also	O
attempted	O
as	O
the	O
basis	O
of	O
brain	B-Application
computer	I-Application
interfaces	I-Application
.	O
</s>
<s>
The	O
EEG	B-Application
is	O
also	O
used	O
quite	O
extensively	O
in	O
the	O
field	O
of	O
neuromarketing	O
.	O
</s>
<s>
The	O
EEG	B-Application
is	O
altered	O
by	O
drugs	O
that	O
affect	O
brain	O
functions	O
,	O
the	O
chemicals	O
that	O
are	O
the	O
basis	O
for	O
psychopharmacology	O
.	O
</s>
<s>
Berger	O
's	O
early	O
experiments	O
recorded	O
the	O
effects	O
of	O
drugs	O
on	O
EEG	B-Application
.	O
</s>
<s>
The	O
science	O
of	O
pharmaco-electroencephalography	O
has	O
developed	O
methods	O
to	O
identify	O
substances	O
that	O
systematically	O
alter	O
brain	O
functions	O
for	O
therapeutic	O
and	O
recreational	O
use	O
.	O
</s>
<s>
Honda	O
is	O
attempting	O
to	O
develop	O
a	O
system	O
to	O
enable	O
an	O
operator	O
to	O
control	O
its	O
Asimo	O
robot	O
using	O
EEG	B-Application
,	O
a	O
technology	O
it	O
eventually	O
hopes	O
to	O
incorporate	O
into	O
its	O
automobiles	O
.	O
</s>
<s>
EEGs	B-Application
have	O
been	O
used	O
as	O
evidence	O
in	O
criminal	O
trials	O
in	O
the	O
Indian	O
state	O
of	O
Maharashtra	O
.	O
</s>
<s>
Brain	O
Electrical	O
Oscillation	O
Signature	O
Profiling	O
(	O
BEOS	O
)	O
,	O
an	O
EEG	B-Application
technique	O
,	O
was	O
used	O
in	O
the	O
trial	O
of	O
State	O
of	O
Maharashtra	O
v	O
.	O
Sharma	O
to	O
show	O
Sharma	O
remembered	O
using	O
arsenic	O
to	O
poison	O
her	O
ex-fiancé	O
,	O
although	O
the	O
reliability	O
and	O
scientific	O
basis	O
of	O
BEOS	O
is	O
disputed	O
.	O
</s>
<s>
A	O
lot	O
of	O
research	O
is	O
currently	O
being	O
carried	O
out	O
in	O
order	O
to	O
make	O
EEG	B-Application
devices	O
smaller	O
,	O
more	O
portable	O
and	O
easier	O
to	O
use	O
.	O
</s>
<s>
So	O
called	O
"	O
Wearable	O
EEG	B-Application
"	O
is	O
based	O
upon	O
creating	O
low	O
power	O
wireless	O
collection	O
electronics	O
and	O
'	O
dry	O
 '	O
electrodes	O
which	O
do	O
not	O
require	O
a	O
conductive	O
gel	O
to	O
be	O
used	O
.	O
</s>
<s>
Wearable	O
EEG	B-Application
aims	O
to	O
provide	O
small	O
EEG	B-Application
devices	O
which	O
are	O
present	O
only	O
on	O
the	O
head	O
and	O
which	O
can	O
record	O
EEG	B-Application
for	O
days	O
,	O
weeks	O
,	O
or	O
months	O
at	O
a	O
time	O
,	O
as	O
ear-EEG	B-Algorithm
.	O
</s>
<s>
Research	O
is	O
also	O
being	O
carried	O
out	O
on	O
identifying	O
specific	O
solutions	O
to	O
increase	O
the	O
battery	O
lifetime	O
of	O
Wearable	O
EEG	B-Application
devices	O
through	O
the	O
use	O
of	O
the	O
data	O
reduction	O
approach	O
.	O
</s>
<s>
In	O
research	O
,	O
currently	O
EEG	B-Application
is	O
often	O
used	O
in	O
combination	O
with	O
machine	O
learning	O
.	O
</s>
<s>
EEG	B-Application
data	O
are	O
pre-processed	O
then	O
passed	O
on	O
to	O
machine	O
learning	O
algorithms	O
.	O
</s>
<s>
These	O
algorithms	O
are	O
then	O
trained	O
to	O
recognize	O
different	O
diseases	O
like	O
schizophrenia	B-Application
,	O
epilepsy	O
or	O
dementia	O
.	O
</s>
<s>
In	O
this	O
vein	O
,	O
complexity	O
measures	O
of	O
EEG	B-Application
data	O
are	O
often	O
calculated	O
,	O
such	O
as	O
Lempel-Ziv	O
complexity	O
,	O
fractal	O
dimension	O
,	O
and	O
spectral	O
flatness	O
.	O
</s>
<s>
It	O
has	O
been	O
shown	O
that	O
combining	O
or	O
multiplying	O
such	O
measures	O
can	O
reveal	O
previously	O
hidden	O
information	O
in	O
EEG	B-Application
data	O
.	O
</s>
<s>
EEG	B-Application
signals	O
from	O
musical	O
performers	O
were	O
used	O
to	O
create	O
instant	O
compositions	O
and	O
one	O
CD	O
by	O
the	O
Brainwave	B-Algorithm
Music	O
Project	O
,	O
run	O
at	O
the	O
Computer	O
Music	O
Center	O
at	O
Columbia	O
University	O
by	O
Brad	O
Garton	O
and	O
Dave	O
Soldier	O
.	O
</s>
<s>
Similarly	O
,	O
an	O
hour-long	O
recording	O
of	O
the	O
brainwaves	B-Algorithm
of	O
Ann	O
Druyan	O
was	O
included	O
on	O
the	O
Voyager	O
Golden	O
Record	O
,	O
launched	O
on	O
the	O
Voyager	O
probes	O
in	O
1977	O
,	O
in	O
case	O
any	O
extraterrestrial	O
intelligence	O
could	O
decode	O
her	O
thoughts	O
,	O
which	O
included	O
what	O
it	O
was	O
like	O
to	O
fall	O
in	O
love	O
.	O
</s>
