<s>
Neural	B-Algorithm
oscillations	I-Algorithm
,	O
or	O
brainwaves	B-Algorithm
,	O
are	O
rhythmic	O
or	O
repetitive	O
patterns	O
of	O
neural	O
activity	O
in	O
the	O
central	O
nervous	O
system	O
.	O
</s>
<s>
Neural	O
tissue	O
can	O
generate	O
oscillatory	B-Algorithm
activity	I-Algorithm
in	O
many	O
ways	O
,	O
driven	O
either	O
by	O
mechanisms	O
within	O
individual	O
neurons	O
or	O
by	O
interactions	O
between	O
neurons	O
.	O
</s>
<s>
In	O
individual	O
neurons	O
,	O
oscillations	B-Algorithm
can	O
appear	O
either	O
as	O
oscillations	B-Algorithm
in	O
membrane	O
potential	O
or	O
as	O
rhythmic	O
patterns	O
of	O
action	B-Algorithm
potentials	I-Algorithm
,	O
which	O
then	O
produce	O
oscillatory	O
activation	O
of	O
post-synaptic	B-Algorithm
neurons	O
.	O
</s>
<s>
At	O
the	O
level	O
of	O
neural	O
ensembles	O
,	O
synchronized	O
activity	O
of	O
large	O
numbers	O
of	O
neurons	O
can	O
give	O
rise	O
to	O
macroscopic	O
oscillations	B-Algorithm
,	O
which	O
can	O
be	O
observed	O
in	O
an	O
electroencephalogram	B-Application
.	O
</s>
<s>
Oscillatory	B-Algorithm
activity	I-Algorithm
in	O
groups	O
of	O
neurons	O
generally	O
arises	O
from	O
feedback	O
connections	O
between	O
the	O
neurons	O
that	O
result	O
in	O
the	O
synchronization	O
of	O
their	O
firing	O
patterns	O
.	O
</s>
<s>
The	O
interaction	O
between	O
neurons	O
can	O
give	O
rise	O
to	O
oscillations	B-Algorithm
at	O
a	O
different	O
frequency	O
than	O
the	O
firing	O
frequency	O
of	O
individual	O
neurons	O
.	O
</s>
<s>
A	O
well-known	O
example	O
of	O
macroscopic	O
neural	B-Algorithm
oscillations	I-Algorithm
is	O
alpha	B-Application
activity	I-Application
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
in	O
humans	O
were	O
observed	O
by	O
researchers	O
as	O
early	O
as	O
1924	O
(	O
by	O
Hans	O
Berger	O
)	O
.	O
</s>
<s>
The	O
possible	O
roles	O
of	O
neural	B-Algorithm
oscillations	I-Algorithm
include	O
feature	O
binding	O
,	O
information	O
transfer	O
mechanisms	O
and	O
the	O
generation	O
of	O
rhythmic	O
motor	O
output	O
.	O
</s>
<s>
Over	O
the	O
last	O
decades	O
more	O
insight	O
has	O
been	O
gained	O
,	O
especially	O
with	O
advances	O
in	O
brain	B-Algorithm
imaging	I-Algorithm
.	O
</s>
<s>
A	O
major	O
area	O
of	O
research	O
in	O
neuroscience	O
involves	O
determining	O
how	O
oscillations	B-Algorithm
are	O
generated	O
and	O
what	O
their	O
roles	O
are	O
.	O
</s>
<s>
Oscillatory	B-Algorithm
activity	I-Algorithm
in	O
the	O
brain	O
is	O
widely	O
observed	O
at	O
different	O
levels	O
of	O
organization	O
and	O
is	O
thought	O
to	O
play	O
a	O
key	O
role	O
in	O
processing	O
neural	O
information	O
.	O
</s>
<s>
Numerous	O
experimental	O
studies	O
support	O
a	O
functional	O
role	O
of	O
neural	B-Algorithm
oscillations	I-Algorithm
;	O
a	O
unified	O
interpretation	O
,	O
however	O
,	O
is	O
still	O
lacking	O
.	O
</s>
<s>
Adolf	O
Beck	O
published	O
in	O
1890	O
his	O
observations	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
detected	O
with	O
electrodes	O
directly	O
placed	O
on	O
the	O
surface	O
of	O
the	O
brain	O
.	O
</s>
<s>
Before	O
Hans	O
Berger	O
,	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
a	O
dog	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
are	O
observed	O
throughout	O
the	O
central	O
nervous	O
system	O
at	O
all	O
levels	O
,	O
and	O
include	O
spike	B-Algorithm
trains	I-Algorithm
,	O
local	B-Algorithm
field	I-Algorithm
potentials	I-Algorithm
and	O
large-scale	O
oscillations	B-Algorithm
which	O
can	O
be	O
measured	O
by	O
electroencephalography	B-Application
(	O
EEG	B-Application
)	O
.	O
</s>
<s>
In	O
general	O
,	O
oscillations	B-Algorithm
can	O
be	O
characterized	O
by	O
their	O
frequency	O
,	O
amplitude	B-Application
and	O
phase	O
.	O
</s>
<s>
These	O
signal	O
properties	O
can	O
be	O
extracted	O
from	O
neural	O
recordings	O
using	O
time-frequency	B-Algorithm
analysis	I-Algorithm
.	O
</s>
<s>
In	O
large-scale	O
oscillations	B-Algorithm
,	O
amplitude	B-Application
changes	O
are	O
considered	O
to	O
result	O
from	O
changes	O
in	O
synchronization	O
within	O
a	O
neural	O
ensemble	O
,	O
also	O
referred	O
to	O
as	O
local	O
synchronization	O
.	O
</s>
<s>
In	O
addition	O
to	O
local	O
synchronization	O
,	O
oscillatory	B-Algorithm
activity	I-Algorithm
of	O
distant	O
neural	O
structures	O
(	O
single	O
neurons	O
or	O
neural	O
ensembles	O
)	O
can	O
synchronize	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
and	O
synchronization	O
have	O
been	O
linked	O
to	O
many	O
cognitive	O
functions	O
such	O
as	O
information	O
transfer	O
,	O
perception	O
,	O
motor	O
control	O
and	O
memory	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
have	O
been	O
most	O
widely	O
studied	O
in	O
neural	O
activity	O
generated	O
by	O
large	O
groups	O
of	O
neurons	O
.	O
</s>
<s>
Large-scale	O
activity	O
can	O
be	O
measured	O
by	O
techniques	O
such	O
as	O
EEG	B-Application
.	O
</s>
<s>
In	O
general	O
,	O
EEG	B-Application
signals	O
have	O
a	O
broad	O
spectral	O
content	O
similar	O
to	O
pink	O
noise	O
,	O
but	O
also	O
reveal	O
oscillatory	B-Algorithm
activity	I-Algorithm
in	O
specific	O
frequency	O
bands	O
.	O
</s>
<s>
The	O
first	O
discovered	O
and	O
best-known	O
frequency	O
band	O
is	O
alpha	B-Application
activity	I-Application
(	O
8	O
–	O
12	O
Hz	O
)	O
that	O
can	O
be	O
detected	O
from	O
the	O
occipital	O
lobe	O
during	O
relaxed	O
wakefulness	O
and	O
which	O
increases	O
when	O
the	O
eyes	O
are	O
closed	O
.	O
</s>
<s>
Other	O
frequency	O
bands	O
are	O
:	O
delta	B-Algorithm
(	O
14Hz	O
)	O
,	O
theta	B-Algorithm
(	O
48Hz	O
)	O
,	O
beta	B-Algorithm
(	O
1330Hz	O
)	O
,	O
low	B-Algorithm
gamma	I-Algorithm
(	O
3070Hz	O
)	O
,	O
and	O
high	B-Algorithm
gamma	I-Algorithm
(	O
70150Hz	O
)	O
frequency	O
bands	O
,	O
where	O
faster	O
rhythms	O
such	O
as	O
gamma	B-Algorithm
activity	I-Algorithm
have	O
been	O
linked	O
to	O
cognitive	O
processing	O
.	O
</s>
<s>
Indeed	O
,	O
EEG	B-Application
signals	O
change	O
dramatically	O
during	O
sleep	O
and	O
show	O
a	O
transition	O
from	O
faster	O
frequencies	O
to	O
increasingly	O
slower	O
frequencies	O
such	O
as	O
alpha	B-Application
waves	I-Application
.	O
</s>
<s>
Consequently	O
,	O
neural	B-Algorithm
oscillations	I-Algorithm
have	O
been	O
linked	O
to	O
cognitive	O
states	O
,	O
such	O
as	O
awareness	O
and	O
consciousness	O
.	O
</s>
<s>
Although	O
neural	B-Algorithm
oscillations	I-Algorithm
in	O
human	O
brain	B-Application
activity	I-Application
are	O
mostly	O
investigated	O
using	O
EEG	B-Application
recordings	O
,	O
they	O
are	O
also	O
observed	O
using	O
more	O
invasive	O
recording	O
techniques	O
such	O
as	O
single-unit	O
recordings	O
.	O
</s>
<s>
Neurons	O
can	O
generate	O
rhythmic	O
patterns	O
of	O
action	B-Algorithm
potentials	I-Algorithm
or	O
spikes	B-Algorithm
.	O
</s>
<s>
Bursting	B-Algorithm
is	O
another	O
form	O
of	O
rhythmic	O
spiking	O
.	O
</s>
<s>
Oscillatory	B-Algorithm
activity	I-Algorithm
can	O
also	O
be	O
observed	O
in	O
the	O
form	O
of	O
subthreshold	B-Algorithm
membrane	I-Algorithm
potential	I-Algorithm
oscillations	I-Algorithm
(	O
i.e.	O
</s>
<s>
in	O
the	O
absence	O
of	O
action	B-Algorithm
potentials	I-Algorithm
)	O
.	O
</s>
<s>
If	O
numerous	O
neurons	O
spike	B-Algorithm
in	O
synchrony	O
,	O
they	O
can	O
give	O
rise	O
to	O
oscillations	B-Algorithm
in	O
local	B-Algorithm
field	I-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
Quantitative	O
models	O
can	O
estimate	O
the	O
strength	O
of	O
neural	B-Algorithm
oscillations	I-Algorithm
in	O
recorded	O
data	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
are	O
commonly	O
studied	O
from	O
a	O
mathematical	O
framework	O
and	O
belong	O
to	O
the	O
field	O
of	O
"	O
neurodynamics	B-Algorithm
"	O
,	O
an	O
area	O
of	O
research	O
in	O
the	O
cognitive	O
sciences	O
that	O
places	O
a	O
strong	O
focus	O
upon	O
the	O
dynamic	O
character	O
of	O
neural	O
activity	O
in	O
describing	O
brain	O
function	O
.	O
</s>
<s>
In	O
particular	O
,	O
it	O
aims	O
to	O
relate	O
dynamic	O
patterns	O
of	O
brain	B-Application
activity	I-Application
to	O
cognitive	O
functions	O
such	O
as	O
perception	O
and	O
memory	O
.	O
</s>
<s>
In	O
very	O
abstract	O
form	O
,	O
neural	B-Algorithm
oscillations	I-Algorithm
can	O
be	O
analyzed	O
analytically	O
.	O
</s>
<s>
When	O
studied	O
in	O
a	O
more	O
physiologically	O
realistic	O
setting	O
,	O
oscillatory	B-Algorithm
activity	I-Algorithm
is	O
generally	O
studied	O
using	O
computer	B-Application
simulations	I-Application
of	O
a	O
computational	B-Application
model	I-Application
.	O
</s>
<s>
The	O
functions	O
of	O
neural	B-Algorithm
oscillations	I-Algorithm
are	O
wide-ranging	O
and	O
vary	O
for	O
different	O
types	O
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
also	O
play	O
an	O
important	O
role	O
in	O
many	O
neurological	O
disorders	O
,	O
such	O
as	O
excessive	O
synchronization	O
during	O
seizure	O
activity	O
in	O
epilepsy	O
or	O
tremor	B-Application
in	O
patients	O
with	O
Parkinson	O
's	O
disease	O
.	O
</s>
<s>
Oscillatory	B-Algorithm
activity	I-Algorithm
can	O
also	O
be	O
used	O
to	O
control	O
external	O
devices	O
such	O
as	O
a	O
brain	B-Application
–	I-Application
computer	I-Application
interface	I-Application
.	O
</s>
<s>
Oscillatory	B-Algorithm
activity	I-Algorithm
is	O
observed	O
throughout	O
the	O
central	O
nervous	O
system	O
at	O
all	O
levels	O
of	O
organization	O
.	O
</s>
<s>
Neurons	O
generate	O
action	B-Algorithm
potentials	I-Algorithm
resulting	O
from	O
changes	O
in	O
the	O
electric	O
membrane	O
potential	O
.	O
</s>
<s>
Neurons	O
can	O
generate	O
multiple	O
action	B-Algorithm
potentials	I-Algorithm
in	O
sequence	O
forming	O
so-called	O
spike	B-Algorithm
trains	I-Algorithm
.	O
</s>
<s>
These	O
spike	B-Algorithm
trains	I-Algorithm
are	O
the	O
basis	O
for	O
neural	O
coding	O
and	O
information	O
transfer	O
in	O
the	O
brain	O
.	O
</s>
<s>
Spike	B-Algorithm
trains	I-Algorithm
can	O
form	O
all	O
kinds	O
of	O
patterns	O
,	O
such	O
as	O
rhythmic	O
spiking	O
and	O
bursting	B-Algorithm
,	O
and	O
often	O
display	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Oscillatory	B-Algorithm
activity	I-Algorithm
in	O
single	O
neurons	O
can	O
also	O
be	O
observed	O
in	O
sub-threshold	B-Algorithm
fluctuations	I-Algorithm
in	O
membrane	O
potential	O
.	O
</s>
<s>
These	O
rhythmic	O
changes	O
in	O
membrane	O
potential	O
do	O
not	O
reach	O
the	O
critical	O
threshold	O
and	O
therefore	O
do	O
not	O
result	O
in	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
They	O
can	O
result	O
from	O
postsynaptic	B-Algorithm
potentials	I-Algorithm
from	O
synchronous	O
inputs	O
or	O
from	O
intrinsic	O
properties	O
of	O
neurons	O
.	O
</s>
<s>
Class	O
I	O
neurons	O
can	O
generate	O
action	B-Algorithm
potentials	I-Algorithm
with	O
arbitrarily	O
low	O
frequency	O
depending	O
on	O
the	O
input	O
strength	O
,	O
whereas	O
Class	O
II	O
neurons	O
generate	O
action	B-Algorithm
potentials	I-Algorithm
in	O
a	O
certain	O
frequency	O
band	O
,	O
which	O
is	O
relatively	O
insensitive	O
to	O
changes	O
in	O
input	O
strength	O
.	O
</s>
<s>
Class	O
II	O
neurons	O
are	O
also	O
more	O
prone	O
to	O
display	O
sub-threshold	O
oscillations	B-Algorithm
in	O
membrane	O
potential	O
.	O
</s>
<s>
A	O
group	O
of	O
neurons	O
can	O
also	O
generate	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Through	O
synaptic	B-Application
interactions	I-Application
,	O
the	O
firing	O
patterns	O
of	O
different	O
neurons	O
may	O
become	O
synchronized	O
and	O
the	O
rhythmic	O
changes	O
in	O
electric	O
potential	O
caused	O
by	O
their	O
action	B-Algorithm
potentials	I-Algorithm
will	O
add	O
up	O
(	O
constructive	O
interference	O
)	O
.	O
</s>
<s>
That	O
is	O
,	O
synchronized	O
firing	O
patterns	O
result	O
in	O
synchronized	O
input	O
into	O
other	O
cortical	O
areas	O
,	O
which	O
gives	O
rise	O
to	O
large-amplitude	O
oscillations	B-Algorithm
of	O
the	O
local	B-Algorithm
field	I-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
These	O
large-scale	O
oscillations	B-Algorithm
can	O
also	O
be	O
measured	O
outside	O
the	O
scalp	O
using	O
electroencephalography	B-Application
(	O
EEG	B-Application
)	O
and	O
magnetoencephalography	B-Algorithm
(	O
MEG	B-Algorithm
)	O
.	O
</s>
<s>
The	O
electric	O
potentials	O
generated	O
by	O
single	O
neurons	O
are	O
far	O
too	O
small	O
to	O
be	O
picked	O
up	O
outside	O
the	O
scalp	O
,	O
and	O
EEG	B-Application
or	O
MEG	B-Algorithm
activity	O
always	O
reflects	O
the	O
summation	O
of	O
the	O
synchronous	O
activity	O
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>
Instead	O
,	O
the	O
probability	O
of	O
firing	O
is	O
rhythmically	O
modulated	O
such	O
that	O
neurons	O
are	O
more	O
likely	O
to	O
fire	O
at	O
the	O
same	O
time	O
,	O
which	O
gives	O
rise	O
to	O
oscillations	B-Algorithm
in	O
their	O
mean	O
activity	O
(	O
see	O
figure	O
at	O
top	O
of	O
page	O
)	O
.	O
</s>
<s>
As	O
such	O
,	O
the	O
frequency	O
of	O
large-scale	O
oscillations	B-Algorithm
does	O
not	O
need	O
to	O
match	O
the	O
firing	O
pattern	O
of	O
individual	O
neurons	O
.	O
</s>
<s>
However	O
,	O
if	O
the	O
probability	O
of	O
a	O
large	O
group	O
of	O
neurons	O
is	O
rhythmically	O
modulated	O
at	O
a	O
common	O
frequency	O
,	O
they	O
will	O
generate	O
oscillations	B-Algorithm
in	O
the	O
mean	O
field	O
(	O
see	O
also	O
figure	O
at	O
top	O
of	O
page	O
)	O
.	O
</s>
<s>
Neural	O
ensembles	O
can	O
generate	O
oscillatory	B-Algorithm
activity	I-Algorithm
endogenously	O
through	O
local	O
interactions	O
between	O
excitatory	O
and	O
inhibitory	O
neurons	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillation	I-Algorithm
can	O
also	O
arise	O
from	O
interactions	O
between	O
different	O
brain	O
areas	O
coupled	O
through	O
the	O
structural	O
connectome	O
.	O
</s>
<s>
Positive	O
feedback	O
loops	O
tend	O
to	O
cause	O
oscillatory	B-Algorithm
activity	I-Algorithm
where	O
frequency	O
is	O
inversely	O
related	O
to	O
the	O
delay	O
time	O
.	O
</s>
<s>
This	O
thalamocortical	O
network	O
is	O
able	O
to	O
generate	O
oscillatory	B-Algorithm
activity	I-Algorithm
known	O
as	O
recurrent	O
thalamo-cortical	O
resonance	B-Application
.	O
</s>
<s>
The	O
thalamocortical	O
network	O
plays	O
an	O
important	O
role	O
in	O
the	O
generation	O
of	O
alpha	B-Application
activity	I-Application
.	O
</s>
<s>
In	O
a	O
whole-brain	O
network	O
model	O
with	O
realistic	O
anatomical	O
connectivity	O
and	O
propagation	O
delays	O
between	O
brain	O
areas	O
,	O
oscillations	B-Algorithm
in	O
the	O
beta	B-Algorithm
frequency	I-Algorithm
range	I-Algorithm
emerge	O
from	O
the	O
partial	O
synchronisation	O
of	O
subsets	O
of	O
brain	O
areas	O
oscillating	O
in	O
the	O
gamma-band	O
(	O
generated	O
at	O
the	O
mesoscopic	O
level	O
)	O
.	O
</s>
<s>
Scientists	O
have	O
identified	O
some	O
intrinsic	O
neuronal	O
properties	O
that	O
play	O
an	O
important	O
role	O
in	O
generating	O
membrane	O
potential	O
oscillations	B-Algorithm
.	O
</s>
<s>
In	O
particular	O
,	O
voltage-gated	O
ion	O
channels	O
are	O
critical	O
in	O
the	O
generation	O
of	O
action	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
The	O
dynamics	O
of	O
these	O
ion	O
channels	O
have	O
been	O
captured	O
in	O
the	O
well-established	O
Hodgkin	O
–	O
Huxley	O
model	O
that	O
describes	O
how	O
action	B-Algorithm
potentials	I-Algorithm
are	O
initiated	O
and	O
propagated	O
by	O
means	O
of	O
a	O
set	O
of	O
differential	O
equations	O
.	O
</s>
<s>
In	O
addition	O
to	O
periodic	O
spiking	O
,	O
subthreshold	B-Algorithm
membrane	I-Algorithm
potential	I-Algorithm
oscillations	I-Algorithm
,	O
i.e.	O
</s>
<s>
resonance	B-Application
behavior	O
that	O
does	O
not	O
result	O
in	O
action	B-Algorithm
potentials	I-Algorithm
,	O
may	O
also	O
contribute	O
to	O
oscillatory	B-Algorithm
activity	I-Algorithm
by	O
facilitating	O
synchronous	O
activity	O
of	O
neighboring	O
neurons	O
.	O
</s>
<s>
Like	O
pacemaker	O
neurons	O
in	O
central	O
pattern	O
generators	O
,	O
subtypes	O
of	O
cortical	O
cells	O
fire	O
bursts	O
of	O
spikes	B-Algorithm
(	O
brief	O
clusters	O
of	O
spikes	B-Algorithm
)	O
rhythmically	O
at	O
preferred	O
frequencies	O
.	O
</s>
<s>
Bursting	B-Algorithm
neurons	O
have	O
the	O
potential	O
to	O
serve	O
as	O
pacemakers	O
for	O
synchronous	O
network	O
oscillations	B-Algorithm
,	O
and	O
bursts	O
of	O
spikes	B-Algorithm
may	O
underlie	O
or	O
enhance	O
neuronal	O
resonance	B-Application
.	O
</s>
<s>
Apart	O
from	O
intrinsic	O
properties	O
of	O
neurons	O
,	O
biological	B-General_Concept
neural	I-General_Concept
network	I-General_Concept
properties	O
are	O
also	O
an	O
important	O
source	O
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Neurons	O
communicate	O
with	O
one	O
another	O
via	O
synapses	B-Application
and	O
affect	O
the	O
timing	O
of	O
spike	B-Algorithm
trains	I-Algorithm
in	O
the	O
post-synaptic	B-Algorithm
neurons	O
.	O
</s>
<s>
Depending	O
on	O
the	O
properties	O
of	O
the	O
connection	O
,	O
such	O
as	O
the	O
coupling	O
strength	O
,	O
time	O
delay	O
and	O
whether	O
coupling	O
is	O
excitatory	O
or	O
inhibitory	O
,	O
the	O
spike	B-Algorithm
trains	I-Algorithm
of	O
the	O
interacting	O
neurons	O
may	O
become	O
synchronized	O
.	O
</s>
<s>
Certain	O
network	O
structures	O
promote	O
oscillatory	B-Algorithm
activity	I-Algorithm
at	O
specific	O
frequencies	O
.	O
</s>
<s>
For	O
example	O
,	O
neuronal	O
activity	O
generated	O
by	O
two	O
populations	O
of	O
interconnected	O
inhibitory	O
and	O
excitatory	O
cells	O
can	O
show	O
spontaneous	O
oscillations	B-Algorithm
that	O
are	O
described	O
by	O
the	O
Wilson-Cowan	B-Algorithm
model	I-Algorithm
.	O
</s>
<s>
If	O
a	O
group	O
of	O
neurons	O
engages	O
in	O
synchronized	O
oscillatory	B-Algorithm
activity	I-Algorithm
,	O
the	O
neural	O
ensemble	O
can	O
be	O
mathematically	O
represented	O
as	O
a	O
single	O
oscillator	O
.	O
</s>
<s>
Weakly	O
coupled	O
oscillators	O
can	O
generate	O
a	O
range	O
of	O
dynamics	O
including	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Long-range	O
connections	O
between	O
different	O
brain	O
structures	O
,	O
such	O
as	O
the	O
thalamus	O
and	O
the	O
cortex	O
(	O
see	O
thalamocortical	O
oscillation	B-Algorithm
)	O
,	O
involve	O
time-delays	O
due	O
to	O
the	O
finite	O
conduction	O
velocity	O
of	O
axons	O
.	O
</s>
<s>
Because	O
most	O
connections	O
are	O
reciprocal	O
,	O
they	O
form	O
feed-back	O
loops	O
that	O
support	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Oscillations	B-Algorithm
recorded	O
from	O
multiple	O
cortical	O
areas	O
can	O
become	O
synchronized	O
to	O
form	O
large	O
scale	O
brain	O
networks	O
,	O
whose	O
dynamics	O
and	O
functional	O
connectivity	O
can	O
be	O
studied	O
by	O
means	O
of	O
spectral	O
analysis	O
and	O
Granger	B-General_Concept
causality	I-General_Concept
measures	O
.	O
</s>
<s>
Coherent	O
activity	O
of	O
large-scale	O
brain	B-Application
activity	I-Application
may	O
form	O
dynamic	O
links	O
between	O
brain	O
areas	O
required	O
for	O
the	O
integration	O
of	O
distributed	O
information	O
.	O
</s>
<s>
In	O
addition	O
to	O
fast	O
direct	O
synaptic	B-Application
interactions	I-Application
between	O
neurons	O
forming	O
a	O
network	O
,	O
oscillatory	B-Algorithm
activity	I-Algorithm
is	O
regulated	O
by	O
neuromodulators	O
on	O
a	O
much	O
slower	O
time	O
scale	O
.	O
</s>
<s>
That	O
is	O
,	O
the	O
concentration	O
levels	O
of	O
certain	O
neurotransmitters	O
are	O
known	O
to	O
regulate	O
the	O
amount	O
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
For	O
instance	O
,	O
GABA	O
concentration	O
has	O
been	O
shown	O
to	O
be	O
positively	O
correlated	O
with	O
frequency	O
of	O
oscillations	B-Algorithm
in	O
induced	O
stimuli	O
.	O
</s>
<s>
These	O
neurotransmitter	O
systems	O
affect	O
the	O
physiological	O
state	O
,	O
e.g.	O
,	O
wakefulness	O
or	O
arousal	O
,	O
and	O
have	O
a	O
pronounced	O
effect	O
on	O
amplitude	B-Application
of	O
different	O
brain	B-Algorithm
waves	I-Algorithm
,	O
such	O
as	O
alpha	B-Application
activity	I-Application
.	O
</s>
<s>
Oscillations	B-Algorithm
can	O
often	O
be	O
described	O
and	O
analyzed	O
using	O
mathematics	O
.	O
</s>
<s>
Harmonic	O
oscillations	B-Algorithm
appear	O
very	O
frequently	O
in	O
nature	O
—	O
examples	O
are	O
sound	O
waves	O
,	O
the	O
motion	O
of	O
a	O
pendulum	O
,	O
and	O
vibrations	O
of	O
every	O
sort	O
.	O
</s>
<s>
Noise-driven	O
harmonic	O
oscillators	O
realistically	O
simulate	O
alpha	O
rhythm	O
in	O
the	O
waking	O
EEG	B-Application
as	O
well	O
as	O
slow	O
waves	O
and	O
spindles	O
in	O
the	O
sleep	O
EEG	B-Application
.	O
</s>
<s>
Successful	O
EEG	B-Algorithm
analysis	I-Algorithm
algorithms	O
were	O
based	O
on	O
such	O
models	O
.	O
</s>
<s>
Several	O
other	O
EEG	B-Application
components	O
are	O
better	O
described	O
by	O
limit-cycle	O
or	O
delayed-feedback	O
oscillations	B-Algorithm
.	O
</s>
<s>
Limit-cycle	O
oscillations	B-Algorithm
arise	O
from	O
physical	O
systems	O
that	O
show	O
large	O
deviations	O
from	O
equilibrium	O
,	O
whereas	O
delayed-feedback	O
oscillations	B-Algorithm
arise	O
when	O
components	O
of	O
a	O
system	O
affect	O
each	O
other	O
after	O
significant	O
time	O
delays	O
.	O
</s>
<s>
Limit-cycle	O
oscillations	B-Algorithm
can	O
be	O
complex	O
but	O
there	O
are	O
powerful	O
mathematical	O
tools	O
for	O
analyzing	O
them	O
;	O
the	O
mathematics	O
of	O
delayed-feedback	O
oscillations	B-Algorithm
is	O
primitive	O
in	O
comparison	O
.	O
</s>
<s>
In	O
a	O
linear	O
oscillator	O
,	O
the	O
frequency	O
is	O
more	O
or	O
less	O
constant	O
but	O
the	O
amplitude	B-Application
can	O
vary	O
greatly	O
.	O
</s>
<s>
In	O
a	O
limit-cycle	O
oscillator	O
,	O
the	O
amplitude	B-Application
tends	O
to	O
be	O
more	O
or	O
less	O
constant	O
but	O
the	O
frequency	O
can	O
vary	O
greatly	O
.	O
</s>
<s>
A	O
heartbeat	O
is	O
an	O
example	O
of	O
a	O
limit-cycle	O
oscillation	B-Algorithm
in	O
that	O
the	O
frequency	O
of	O
beats	O
varies	O
widely	O
,	O
while	O
each	O
individual	O
beat	O
continues	O
to	O
pump	O
about	O
the	O
same	O
amount	O
of	O
blood	O
.	O
</s>
<s>
Computational	B-Application
models	I-Application
adopt	O
a	O
variety	O
of	O
abstractions	O
in	O
order	O
to	O
describe	O
complex	O
oscillatory	O
dynamics	O
observed	O
in	O
brain	B-Application
activity	I-Application
.	O
</s>
<s>
It	O
is	O
a	O
set	O
of	O
nonlinear	O
ordinary	O
differential	O
equations	O
that	O
approximates	O
the	O
electrical	O
characteristics	O
of	O
a	O
neuron	O
,	O
in	O
particular	O
the	O
generation	O
and	O
propagation	O
of	O
action	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
The	O
mathematics	O
of	O
the	O
Hodgkin	O
–	O
Huxley	O
model	O
are	O
quite	O
complicated	O
and	O
several	O
simplifications	O
have	O
been	O
proposed	O
,	O
such	O
as	O
the	O
FitzHugh	O
–	O
Nagumo	O
model	O
,	O
the	O
Hindmarsh	B-Algorithm
–	I-Algorithm
Rose	I-Algorithm
model	I-Algorithm
or	O
the	O
capacitor-switch	O
model	O
as	O
an	O
extension	O
of	O
the	O
integrate-and-fire	O
model	O
.	O
</s>
<s>
Such	O
models	O
only	O
capture	O
the	O
basic	O
neuronal	O
dynamics	O
,	O
such	O
as	O
rhythmic	O
spiking	O
and	O
bursting	B-Algorithm
,	O
but	O
are	O
more	O
computationally	O
efficient	O
.	O
</s>
<s>
This	O
allows	O
the	O
simulation	O
of	O
a	O
large	O
number	O
of	O
interconnected	O
neurons	O
that	O
form	O
a	O
neural	B-General_Concept
network	I-General_Concept
.	O
</s>
<s>
A	O
neural	B-General_Concept
network	I-General_Concept
model	O
describes	O
a	O
population	O
of	O
physically	O
interconnected	O
neurons	O
or	O
a	O
group	O
of	O
disparate	O
neurons	O
whose	O
inputs	O
or	O
signalling	O
targets	O
define	O
a	O
recognizable	O
circuit	O
.	O
</s>
<s>
Local	O
interactions	O
between	O
neurons	O
can	O
result	O
in	O
the	O
synchronization	O
of	O
spiking	O
activity	O
and	O
form	O
the	O
basis	O
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
In	O
particular	O
,	O
models	O
of	O
interacting	O
pyramidal	O
cells	O
and	O
inhibitory	O
interneurons	O
have	O
been	O
shown	O
to	O
generate	O
brain	B-Algorithm
rhythms	I-Algorithm
such	O
as	O
gamma	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Similarly	O
,	O
it	O
was	O
shown	O
that	O
simulations	O
of	O
neural	B-General_Concept
networks	I-General_Concept
with	O
a	O
phenomenological	O
model	O
for	O
neuronal	O
response	O
failures	O
can	O
predict	O
spontaneous	O
broadband	O
neural	B-Algorithm
oscillations	I-Algorithm
.	O
</s>
<s>
Neural	O
field	O
models	O
are	O
another	O
important	O
tool	O
in	O
studying	O
neural	B-Algorithm
oscillations	I-Algorithm
and	O
are	O
a	O
mathematical	O
framework	O
describing	O
evolution	O
of	O
variables	O
such	O
as	O
mean	O
firing	O
rate	O
in	O
space	O
and	O
time	O
.	O
</s>
<s>
In	O
modeling	O
the	O
activity	O
of	O
large	O
numbers	O
of	O
neurons	O
,	O
the	O
central	O
idea	O
is	O
to	O
take	O
the	O
density	O
of	O
neurons	O
to	O
the	O
continuum	B-Algorithm
limit	I-Algorithm
,	O
resulting	O
in	O
spatially	O
continuous	O
neural	B-General_Concept
networks	I-General_Concept
.	O
</s>
<s>
Models	O
based	O
on	O
these	O
principles	O
have	O
been	O
used	O
to	O
provide	O
mathematical	O
descriptions	O
of	O
neural	B-Algorithm
oscillations	I-Algorithm
and	O
EEG	B-Application
rhythms	O
.	O
</s>
<s>
The	O
Kuramoto	O
model	O
of	O
coupled	O
phase	O
oscillators	O
is	O
one	O
of	O
the	O
most	O
abstract	O
and	O
fundamental	O
models	O
used	O
to	O
investigate	O
neural	B-Algorithm
oscillations	I-Algorithm
and	O
synchronization	O
.	O
</s>
<s>
It	O
captures	O
the	O
activity	O
of	O
a	O
local	O
system	O
(	O
e.g.	O
,	O
a	O
single	O
neuron	O
or	O
neural	O
ensemble	O
)	O
by	O
its	O
circular	O
phase	O
alone	O
and	O
hence	O
ignores	O
the	O
amplitude	B-Application
of	O
oscillations	B-Algorithm
(	O
amplitude	B-Application
is	O
constant	O
)	O
.	O
</s>
<s>
The	O
Kuramoto	O
model	O
is	O
widely	O
used	O
to	O
study	O
oscillatory	O
brain	B-Application
activity	I-Application
and	O
several	O
extensions	O
have	O
been	O
proposed	O
that	O
increase	O
its	O
neurobiological	O
plausibility	O
,	O
for	O
instance	O
by	O
incorporating	O
topological	O
properties	O
of	O
local	O
cortical	O
connectivity	O
.	O
</s>
<s>
In	O
particular	O
,	O
it	O
describes	O
how	O
the	O
activity	O
of	O
a	O
group	O
of	O
interacting	O
neurons	O
can	O
become	O
synchronized	O
and	O
generate	O
large-scale	O
oscillations	B-Algorithm
.	O
</s>
<s>
Simulations	O
using	O
the	O
Kuramoto	O
model	O
with	O
realistic	O
long-range	O
cortical	O
connectivity	O
and	O
time-delayed	O
interactions	O
reveal	O
the	O
emergence	O
of	O
slow	O
patterned	O
fluctuations	O
that	O
reproduce	O
resting-state	O
BOLD	B-Algorithm
functional	O
maps	O
,	O
which	O
can	O
be	O
measured	O
using	O
fMRI	B-Algorithm
.	O
</s>
<s>
Both	O
single	O
neurons	O
and	O
groups	O
of	O
neurons	O
can	O
generate	O
oscillatory	B-Algorithm
activity	I-Algorithm
spontaneously	O
.	O
</s>
<s>
Likewise	O
,	O
brain-wide	O
activity	O
reveals	O
oscillatory	B-Algorithm
activity	I-Algorithm
while	O
subjects	O
do	O
not	O
engage	O
in	O
any	O
activity	O
,	O
so-called	O
resting-state	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Oscillatory	B-Algorithm
activity	I-Algorithm
may	O
respond	O
by	O
increases	O
or	O
decreases	O
in	O
frequency	O
and	O
amplitude	B-Application
or	O
show	O
a	O
temporary	O
interruption	O
,	O
which	O
is	O
referred	O
to	O
as	O
phase	O
resetting	O
.	O
</s>
<s>
Spontaneous	B-Algorithm
activity	I-Algorithm
is	O
brain	B-Application
activity	I-Application
in	O
the	O
absence	O
of	O
an	O
explicit	O
task	O
,	O
such	O
as	O
sensory	O
input	O
or	O
motor	O
output	O
,	O
and	O
hence	O
also	O
referred	O
to	O
as	O
resting-state	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
It	O
is	O
opposed	O
to	O
induced	B-Algorithm
activity	I-Algorithm
,	O
i.e.	O
</s>
<s>
brain	B-Application
activity	I-Application
that	O
is	O
induced	O
by	O
sensory	O
stimuli	O
or	O
motor	O
responses	O
.	O
</s>
<s>
The	O
term	O
ongoing	B-Algorithm
brain	I-Algorithm
activity	I-Algorithm
is	O
used	O
in	O
electroencephalography	B-Application
and	O
magnetoencephalography	B-Algorithm
for	O
those	O
signal	O
components	O
that	O
are	O
not	O
associated	O
with	O
the	O
processing	O
of	O
a	O
stimulus	O
or	O
the	O
occurrence	O
of	O
specific	O
other	O
events	O
,	O
such	O
as	O
moving	O
a	O
body	O
part	O
,	O
i.e.	O
</s>
<s>
events	O
that	O
do	O
not	O
form	O
evoked	O
potentials/evoked	O
fields	O
,	O
or	O
induced	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Spontaneous	B-Algorithm
activity	I-Algorithm
is	O
usually	O
considered	O
to	O
be	O
noise	O
if	O
one	O
is	O
interested	O
in	O
stimulus	O
processing	O
;	O
however	O
,	O
spontaneous	B-Algorithm
activity	I-Algorithm
is	O
considered	O
to	O
play	O
a	O
crucial	O
role	O
during	O
brain	O
development	O
,	O
such	O
as	O
in	O
network	O
formation	O
and	O
synaptogenesis	O
.	O
</s>
<s>
Spontaneous	B-Algorithm
activity	I-Algorithm
may	O
be	O
informative	O
regarding	O
the	O
current	O
mental	O
state	O
of	O
the	O
person	O
(	O
e.g.	O
</s>
<s>
Certain	O
types	O
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
,	O
such	O
as	O
alpha	B-Application
waves	I-Application
,	O
are	O
part	O
of	O
spontaneous	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Statistical	O
analysis	O
of	O
power	O
fluctuations	O
of	O
alpha	B-Application
activity	I-Application
reveals	O
a	O
bimodal	O
distribution	O
,	O
i.e.	O
</s>
<s>
a	O
high	O
-	O
and	O
low-amplitude	O
mode	O
,	O
and	O
hence	O
shows	O
that	O
resting-state	B-Algorithm
activity	I-Algorithm
does	O
not	O
just	O
reflect	O
a	O
noise	O
process	O
.	O
</s>
<s>
In	O
case	O
of	O
fMRI	B-Algorithm
,	O
spontaneous	O
fluctuations	O
in	O
the	O
blood-oxygen-level	B-Algorithm
dependent	I-Algorithm
(	O
BOLD	B-Algorithm
)	O
signal	O
reveal	O
correlation	O
patterns	O
that	O
are	O
linked	O
to	O
resting	B-Algorithm
states	I-Algorithm
networks	O
,	O
such	O
as	O
the	O
default	O
network	O
.	O
</s>
<s>
The	O
temporal	O
evolution	O
of	O
resting	B-Algorithm
state	I-Algorithm
networks	O
is	O
correlated	O
with	O
fluctuations	O
of	O
oscillatory	O
EEG	B-Application
activity	O
in	O
different	O
frequency	O
bands	O
.	O
</s>
<s>
Ongoing	B-Algorithm
brain	I-Algorithm
activity	I-Algorithm
may	O
also	O
have	O
an	O
important	O
role	O
in	O
perception	O
,	O
as	O
it	O
may	O
interact	O
with	O
activity	O
related	O
to	O
incoming	O
stimuli	O
.	O
</s>
<s>
Indeed	O
,	O
EEG	B-Application
studies	O
suggest	O
that	O
visual	O
perception	O
is	O
dependent	O
on	O
both	O
the	O
phase	O
and	O
amplitude	B-Application
of	O
cortical	B-Algorithm
oscillations	I-Algorithm
.	O
</s>
<s>
For	O
instance	O
,	O
the	O
amplitude	B-Application
and	O
phase	O
of	O
alpha	B-Application
activity	I-Application
at	O
the	O
moment	O
of	O
visual	O
stimulation	O
predicts	O
whether	O
a	O
weak	O
stimulus	O
will	O
be	O
perceived	O
by	O
the	O
subject	O
.	O
</s>
<s>
In	O
response	O
to	O
input	O
,	O
a	O
neuron	O
or	O
neuronal	O
ensemble	O
may	O
change	O
the	O
frequency	O
at	O
which	O
it	O
oscillates	O
,	O
thus	O
changing	O
the	O
rate	O
at	O
which	O
it	O
spikes	B-Algorithm
.	O
</s>
<s>
However	O
,	O
changes	O
in	O
relative	O
oscillation	B-Algorithm
frequency	O
between	O
different	O
brain	O
areas	O
is	O
not	O
so	O
common	O
because	O
the	O
frequency	O
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
is	O
often	O
related	O
to	O
the	O
time	O
delays	O
between	O
brain	O
areas	O
.	O
</s>
<s>
Next	O
to	O
evoked	O
activity	O
,	O
neural	O
activity	O
related	O
to	O
stimulus	O
processing	O
may	O
result	O
in	O
induced	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
Induced	B-Algorithm
activity	I-Algorithm
refers	O
to	O
modulation	O
in	O
ongoing	B-Algorithm
brain	I-Algorithm
activity	I-Algorithm
induced	O
by	O
processing	O
of	O
stimuli	O
or	O
movement	O
preparation	O
.	O
</s>
<s>
Hence	O
,	O
they	O
reflect	O
an	O
indirect	O
response	O
in	O
contrast	O
to	O
evoked	B-Algorithm
responses	I-Algorithm
.	O
</s>
<s>
A	O
well-studied	O
type	O
of	O
induced	B-Algorithm
activity	I-Algorithm
is	O
amplitude	B-Application
change	O
in	O
oscillatory	B-Algorithm
activity	I-Algorithm
.	O
</s>
<s>
For	O
instance	O
,	O
gamma	B-Algorithm
activity	I-Algorithm
often	O
increases	O
during	O
increased	O
mental	O
activity	O
such	O
as	O
during	O
object	O
representation	O
.	O
</s>
<s>
Because	O
induced	O
responses	O
may	O
have	O
different	O
phases	O
across	O
measurements	O
and	O
therefore	O
would	O
cancel	O
out	O
during	O
averaging	O
,	O
they	O
can	O
only	O
be	O
obtained	O
using	O
time-frequency	B-Algorithm
analysis	I-Algorithm
.	O
</s>
<s>
Induced	B-Algorithm
activity	I-Algorithm
generally	O
reflects	O
the	O
activity	O
of	O
numerous	O
neurons	O
:	O
amplitude	B-Application
changes	O
in	O
oscillatory	B-Algorithm
activity	I-Algorithm
are	O
thought	O
to	O
arise	O
from	O
the	O
synchronization	O
of	O
neural	O
activity	O
,	O
for	O
instance	O
by	O
synchronization	O
of	O
spike	B-Algorithm
timing	O
or	O
membrane	O
potential	O
fluctuations	O
of	O
individual	O
neurons	O
.	O
</s>
<s>
Increases	O
in	O
oscillatory	B-Algorithm
activity	I-Algorithm
are	O
therefore	O
often	O
referred	O
to	O
as	O
event-related	O
synchronization	O
,	O
while	O
decreases	O
are	O
referred	O
to	O
as	O
event-related	O
desynchronization	O
.	O
</s>
<s>
Phase	O
resetting	O
occurs	O
when	O
input	O
to	O
a	O
neuron	O
or	O
neuronal	O
ensemble	O
resets	O
the	O
phase	O
of	O
ongoing	O
oscillations	B-Algorithm
.	O
</s>
<s>
It	O
is	O
very	O
common	O
in	O
single	O
neurons	O
where	O
spike	B-Algorithm
timing	O
is	O
adjusted	O
to	O
neuronal	O
input	O
(	O
a	O
neuron	O
may	O
spike	B-Algorithm
at	O
a	O
fixed	O
delay	O
in	O
response	O
to	O
periodic	O
input	O
,	O
which	O
is	O
referred	O
to	O
as	O
phase	O
locking	O
)	O
and	O
may	O
also	O
occur	O
in	O
neuronal	O
ensembles	O
when	O
the	O
phases	O
of	O
their	O
neurons	O
are	O
adjusted	O
simultaneously	O
.	O
</s>
<s>
Phase	O
resetting	O
is	O
fundamental	O
for	O
the	O
synchronization	O
of	O
different	O
neurons	O
or	O
different	O
brain	O
regions	O
because	O
the	O
timing	O
of	O
spikes	B-Algorithm
can	O
become	O
phase	O
locked	O
to	O
the	O
activity	O
of	O
other	O
neurons	O
.	O
</s>
<s>
Phase	O
resetting	O
also	O
permits	O
the	O
study	O
of	O
evoked	O
activity	O
,	O
a	O
term	O
used	O
in	O
electroencephalography	B-Application
and	O
magnetoencephalography	B-Algorithm
for	O
responses	O
in	O
brain	B-Application
activity	I-Application
that	O
are	O
directly	O
related	O
to	O
stimulus-related	O
activity	O
.	O
</s>
<s>
Evoked	B-Algorithm
potentials	I-Algorithm
and	O
event-related	B-Algorithm
potentials	I-Algorithm
are	O
obtained	O
from	O
an	O
electroencephalogram	B-Application
by	O
stimulus-locked	O
averaging	O
,	O
i.e.	O
</s>
<s>
ongoing	O
or	O
spontaneous	B-Algorithm
activity	I-Algorithm
,	O
are	O
averaged	O
out	O
.	O
</s>
<s>
That	O
is	O
,	O
event-related	B-Algorithm
potentials	I-Algorithm
only	O
reflect	O
oscillations	B-Algorithm
in	O
brain	B-Application
activity	I-Application
that	O
are	O
phase-locked	O
to	O
the	O
stimulus	O
or	O
event	O
.	O
</s>
<s>
Evoked	O
activity	O
is	O
often	O
considered	O
to	O
be	O
independent	O
from	O
ongoing	B-Algorithm
brain	I-Algorithm
activity	I-Algorithm
,	O
although	O
this	O
is	O
an	O
ongoing	O
debate	O
.	O
</s>
<s>
It	O
has	O
recently	O
been	O
proposed	O
that	O
even	O
if	O
phases	O
are	O
not	O
aligned	O
across	O
trials	O
,	O
induced	B-Algorithm
activity	I-Algorithm
may	O
still	O
cause	O
event-related	B-Algorithm
potentials	I-Algorithm
because	O
ongoing	O
brain	O
oscillations	B-Algorithm
may	O
not	O
be	O
symmetric	O
and	O
thus	O
amplitude	B-Application
modulations	O
may	O
result	O
in	O
a	O
baseline	O
shift	O
that	O
does	O
not	O
average	O
out	O
.	O
</s>
<s>
This	O
model	O
implies	O
that	O
slow	O
event-related	O
responses	O
,	O
such	O
as	O
asymmetric	O
alpha	B-Application
activity	I-Application
,	O
could	O
result	O
from	O
asymmetric	O
brain	O
oscillation	B-Algorithm
amplitude	B-Application
modulations	O
,	O
such	O
as	O
an	O
asymmetry	O
of	O
the	O
intracellular	O
currents	O
that	O
propagate	O
forward	O
and	O
backward	O
down	O
the	O
dendrites	O
.	O
</s>
<s>
Under	O
this	O
assumption	O
,	O
asymmetries	O
in	O
the	O
dendritic	O
current	O
would	O
cause	O
asymmetries	O
in	O
oscillatory	B-Algorithm
activity	I-Algorithm
measured	O
by	O
EEG	B-Application
and	O
MEG	B-Algorithm
,	O
since	O
dendritic	O
currents	O
in	O
pyramidal	O
cells	O
are	O
generally	O
thought	O
to	O
generate	O
EEG	B-Application
and	O
MEG	B-Algorithm
signals	O
that	O
can	O
be	O
measured	O
at	O
the	O
scalp	O
.	O
</s>
<s>
Neural	B-Algorithm
synchronization	I-Algorithm
can	O
be	O
modulated	O
by	O
task	O
constraints	O
,	O
such	O
as	O
attention	O
,	O
and	O
is	O
thought	O
to	O
play	O
a	O
role	O
in	O
feature	O
binding	O
,	O
neuronal	O
communication	O
,	O
and	O
motor	O
coordination	O
.	O
</s>
<s>
Neuronal	B-Algorithm
oscillations	I-Algorithm
became	O
a	O
hot	O
topic	O
in	O
neuroscience	O
in	O
the	O
1990s	O
when	O
the	O
studies	O
of	O
the	O
visual	O
system	O
of	O
the	O
brain	O
by	O
Gray	O
,	O
Singer	O
and	O
others	O
appeared	O
to	O
support	O
the	O
neural	O
binding	O
hypothesis	O
.	O
</s>
<s>
According	O
to	O
this	O
idea	O
,	O
synchronous	O
oscillations	B-Algorithm
in	O
neuronal	O
ensembles	O
bind	O
neurons	O
representing	O
different	O
features	O
of	O
an	O
object	O
.	O
</s>
<s>
This	O
phenomenon	O
is	O
best	O
seen	O
in	O
local	B-Algorithm
field	I-Algorithm
potentials	I-Algorithm
which	O
reflect	O
the	O
synchronous	O
activity	O
of	O
local	O
groups	O
of	O
neurons	O
,	O
but	O
has	O
also	O
been	O
shown	O
in	O
EEG	B-Application
and	O
MEG	B-Algorithm
recordings	O
providing	O
increasing	O
evidence	O
for	O
a	O
close	O
relation	O
between	O
synchronous	O
oscillatory	B-Algorithm
activity	I-Algorithm
and	O
a	O
variety	O
of	O
cognitive	O
functions	O
such	O
as	O
perceptual	O
grouping	O
and	O
attentional	O
top-down	O
control	O
.	O
</s>
<s>
Although	O
all	O
of	O
the	O
heart	O
's	O
cells	O
have	O
the	O
ability	O
to	O
generate	O
action	B-Algorithm
potentials	I-Algorithm
that	O
trigger	O
cardiac	O
contraction	O
,	O
the	O
sinoatrial	O
node	O
normally	O
initiates	O
it	O
,	O
simply	O
because	O
it	O
generates	O
impulses	O
slightly	O
faster	O
than	O
the	O
other	O
areas	O
.	O
</s>
<s>
Central	O
pattern	O
generators	O
are	O
neuronal	B-General_Concept
circuits	I-General_Concept
that	O
—	O
when	O
activated	O
—	O
can	O
produce	O
rhythmic	O
motor	O
patterns	O
in	O
the	O
absence	O
of	O
sensory	O
or	O
descending	O
inputs	O
that	O
carry	O
specific	O
timing	O
information	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
could	O
create	O
periodic	O
time	O
windows	O
in	O
which	O
input	O
spikes	B-Algorithm
have	O
larger	O
effect	O
on	O
neurons	O
,	O
thereby	O
providing	O
a	O
mechanism	O
for	O
decoding	O
temporal	O
codes	O
.	O
</s>
<s>
Synchronization	O
of	O
neuronal	B-Algorithm
firing	I-Algorithm
may	O
serve	O
as	O
a	O
means	O
to	O
group	O
spatially	O
segregated	O
neurons	O
that	O
respond	O
to	O
the	O
same	O
stimulus	O
in	O
order	O
to	O
bind	O
these	O
responses	O
for	O
further	O
joint	O
processing	O
,	O
i.e.	O
</s>
<s>
The	O
functional	O
role	O
of	O
synchronized	O
oscillatory	B-Algorithm
activity	I-Algorithm
in	O
the	O
brain	O
was	O
mainly	O
established	O
in	O
experiments	O
performed	O
on	O
awake	O
kittens	O
with	O
multiple	O
electrodes	O
implanted	O
in	O
the	O
visual	O
cortex	O
.	O
</s>
<s>
These	O
experiments	O
showed	O
that	O
groups	O
of	O
spatially	O
segregated	O
neurons	O
engage	O
in	O
synchronous	O
oscillatory	B-Algorithm
activity	I-Algorithm
when	O
activated	O
by	O
visual	O
stimuli	O
.	O
</s>
<s>
The	O
frequency	O
of	O
these	O
oscillations	B-Algorithm
was	O
in	O
the	O
range	O
of	O
40Hz	O
and	O
differed	O
from	O
the	O
periodic	O
activation	O
induced	O
by	O
the	O
grating	O
,	O
suggesting	O
that	O
the	O
oscillations	B-Algorithm
and	O
their	O
synchronization	O
were	O
due	O
to	O
internal	O
neuronal	O
interactions	O
.	O
</s>
<s>
Similar	O
findings	O
were	O
shown	O
in	O
parallel	O
by	O
the	O
group	O
of	O
Eckhorn	O
,	O
providing	O
further	O
evidence	O
for	O
the	O
functional	O
role	O
of	O
neural	B-Algorithm
synchronization	I-Algorithm
in	O
feature	O
binding	O
.	O
</s>
<s>
Since	O
then	O
,	O
numerous	O
studies	O
have	O
replicated	O
these	O
findings	O
and	O
extended	O
them	O
to	O
different	O
modalities	O
such	O
as	O
EEG	B-Application
,	O
providing	O
extensive	O
evidence	O
of	O
the	O
functional	O
role	O
of	O
gamma	B-Algorithm
oscillations	I-Algorithm
in	O
visual	O
perception	O
.	O
</s>
<s>
These	O
oscillations	B-Algorithm
can	O
be	O
disrupted	O
by	O
GABA	O
blocker	O
picrotoxin	O
,	O
and	O
the	O
disruption	O
of	O
the	O
oscillatory	O
synchronization	O
leads	O
to	O
impairment	O
of	O
behavioral	O
discrimination	O
of	O
chemically	O
similar	O
odorants	O
in	O
bees	O
and	O
to	O
more	O
similar	O
responses	O
across	O
odors	O
in	O
downstream	O
β-lobe	O
neurons	O
.	O
</s>
<s>
Recent	O
follow-up	O
of	O
this	O
work	O
has	O
shown	O
that	O
oscillations	B-Algorithm
create	O
periodic	O
integration	O
windows	O
for	O
Kenyon	O
cells	O
in	O
the	O
insect	O
mushroom	O
body	O
,	O
such	O
that	O
incoming	O
spikes	B-Algorithm
from	O
the	O
antennal	O
lobe	O
are	O
more	O
effective	O
in	O
activating	O
Kenyon	O
cells	O
only	O
at	O
specific	O
phases	O
of	O
the	O
oscillatory	O
cycle	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
are	O
also	O
thought	O
be	O
involved	O
in	O
the	O
sense	O
of	O
time	O
and	O
in	O
somatosensory	O
perception	O
.	O
</s>
<s>
However	O
,	O
recent	O
findings	O
argue	O
against	O
a	O
clock-like	O
function	O
of	O
cortical	O
gamma	B-Algorithm
oscillations	I-Algorithm
.	O
</s>
<s>
Oscillations	B-Algorithm
have	O
been	O
commonly	O
reported	O
in	O
the	O
motor	O
system	O
.	O
</s>
<s>
Pfurtscheller	O
and	O
colleagues	O
found	O
a	O
reduction	O
in	O
alpha	O
(	O
812Hz	O
)	O
and	O
beta	B-Algorithm
(	O
1330Hz	O
)	O
oscillations	B-Algorithm
in	O
EEG	B-Application
activity	O
when	O
subjects	O
made	O
a	O
movement	O
.	O
</s>
<s>
Using	O
intra-cortical	O
recordings	O
,	O
similar	O
changes	O
in	O
oscillatory	B-Algorithm
activity	I-Algorithm
were	O
found	O
in	O
the	O
motor	O
cortex	O
when	O
the	O
monkeys	O
performed	O
motor	O
acts	O
that	O
required	O
significant	O
attention	O
.	O
</s>
<s>
In	O
addition	O
,	O
oscillations	B-Algorithm
at	O
spinal	O
level	O
become	O
synchronised	O
to	O
beta	B-Algorithm
oscillations	B-Algorithm
in	O
the	O
motor	O
cortex	O
during	O
constant	O
muscle	O
activation	O
,	O
as	O
determined	O
by	O
cortico-muscular	O
coherence	O
.	O
</s>
<s>
Recently	O
it	O
was	O
found	O
that	O
cortical	B-Algorithm
oscillations	I-Algorithm
propagate	O
as	O
travelling	O
waves	O
across	O
the	O
surface	O
of	O
the	O
motor	O
cortex	O
along	O
dominant	O
spatial	O
axes	O
characteristic	O
of	O
the	O
local	O
circuitry	O
of	O
the	O
motor	O
cortex	O
.	O
</s>
<s>
Simulations	O
have	O
shown	O
that	O
ongoing	O
wave	O
activity	O
in	O
cortex	O
can	O
elicit	O
steady	O
muscle	O
force	O
with	O
physiological	O
levels	O
of	O
EEG-EMG	O
coherence	O
.	O
</s>
<s>
These	O
oscillations	B-Algorithm
are	O
also	O
observed	O
in	O
motor	O
output	O
of	O
physiological	O
tremor	B-Application
and	O
when	O
performing	O
slow	O
finger	O
movements	O
.	O
</s>
<s>
In	O
support	O
,	O
it	O
was	O
shown	O
that	O
these	O
movement	O
discontinuities	O
are	O
directly	O
correlated	O
to	O
oscillatory	B-Algorithm
activity	I-Algorithm
in	O
a	O
cerebello-thalamo-cortical	O
loop	O
,	O
which	O
may	O
represent	O
a	O
neural	O
mechanism	O
for	O
the	O
intermittent	O
motor	O
control	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
,	O
in	O
particular	O
theta	B-Algorithm
activity	O
,	O
are	O
extensively	O
linked	O
to	O
memory	O
function	O
.	O
</s>
<s>
Theta	B-Algorithm
rhythms	I-Algorithm
are	O
very	O
strong	O
in	O
rodent	O
hippocampi	O
and	O
entorhinal	O
cortex	O
during	O
learning	O
and	O
memory	O
retrieval	O
,	O
and	O
they	O
are	O
believed	O
to	O
be	O
vital	O
to	O
the	O
induction	O
of	O
long-term	O
potentiation	O
,	O
a	O
potential	O
cellular	O
mechanism	O
for	O
learning	O
and	O
memory	O
.	O
</s>
<s>
Coupling	O
between	O
theta	B-Algorithm
and	O
gamma	B-Algorithm
activity	I-Algorithm
is	O
thought	O
to	O
be	O
vital	O
for	O
memory	O
functions	O
,	O
including	O
episodic	O
memory	O
.	O
</s>
<s>
Tight	O
coordination	O
of	O
single-neuron	O
spikes	B-Algorithm
with	O
local	O
theta	B-Algorithm
oscillations	B-Algorithm
is	O
linked	O
to	O
successful	O
memory	O
formation	O
in	O
humans	O
,	O
as	O
more	O
stereotyped	O
spiking	O
predicts	O
better	O
memory	O
.	O
</s>
<s>
Sleep	O
stages	O
are	O
characterized	O
by	O
spectral	O
content	O
of	O
EEG	B-Application
:	O
for	O
instance	O
,	O
stage	O
N1	O
refers	O
to	O
the	O
transition	O
of	O
the	O
brain	O
from	O
alpha	B-Application
waves	I-Application
(	O
common	O
in	O
the	O
awake	O
state	O
)	O
to	O
theta	B-Algorithm
waves	I-Algorithm
,	O
whereas	O
stage	O
N3	O
(	O
deep	O
or	O
slow-wave	O
sleep	O
)	O
is	O
characterized	O
by	O
the	O
presence	O
of	O
delta	B-Algorithm
waves	I-Algorithm
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
may	O
play	O
a	O
role	O
in	O
neural	O
development	O
.	O
</s>
<s>
For	O
example	O
,	O
retinal	O
waves	O
are	O
thought	O
to	O
have	O
properties	O
that	O
define	O
early	O
connectivity	O
of	O
circuits	O
and	O
synapses	B-Application
between	O
cells	O
in	O
the	O
retina	O
.	O
</s>
<s>
Specific	O
types	O
of	O
neural	B-Algorithm
oscillations	I-Algorithm
may	O
also	O
appear	O
in	O
pathological	O
situations	O
,	O
such	O
as	O
Parkinson	O
's	O
disease	O
or	O
epilepsy	O
.	O
</s>
<s>
These	O
pathological	O
oscillations	B-Algorithm
often	O
consist	O
of	O
an	O
aberrant	O
version	O
of	O
a	O
normal	O
oscillation	B-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
one	O
of	O
the	O
best	O
known	O
types	O
is	O
the	O
spike	B-Algorithm
and	I-Algorithm
wave	I-Algorithm
oscillation	B-Algorithm
,	O
which	O
is	O
typical	O
of	O
generalized	O
or	O
absence	O
epileptic	O
seizures	O
,	O
and	O
which	O
resembles	O
normal	O
sleep	B-Algorithm
spindle	I-Algorithm
oscillations	B-Algorithm
.	O
</s>
<s>
A	O
tremor	B-Application
is	O
an	O
involuntary	O
,	O
somewhat	O
rhythmic	O
,	O
muscle	O
contraction	O
and	O
relaxation	O
involving	O
to-and-fro	O
movements	O
of	O
one	O
or	O
more	O
body	O
parts	O
.	O
</s>
<s>
Most	O
tremors	B-Application
occur	O
in	O
the	O
hands	O
.	O
</s>
<s>
In	O
some	O
people	O
,	O
tremor	B-Application
is	O
a	O
symptom	O
of	O
another	O
neurological	O
disorder	O
.	O
</s>
<s>
Many	O
different	O
forms	O
of	O
tremor	B-Application
have	O
been	O
identified	O
,	O
such	O
as	O
essential	O
tremor	B-Application
or	O
Parkinsonian	O
tremor	B-Application
.	O
</s>
<s>
It	O
is	O
argued	O
that	O
tremors	B-Application
are	O
likely	O
to	O
be	O
multifactorial	O
in	O
origin	O
,	O
with	O
contributions	O
from	O
neural	B-Algorithm
oscillations	I-Algorithm
in	O
the	O
central	O
nervous	O
systems	O
,	O
but	O
also	O
from	O
peripheral	O
mechanisms	O
such	O
as	O
reflex	O
loop	O
resonances	B-Application
.	O
</s>
<s>
These	O
seizures	O
are	O
transient	O
signs	O
and/or	O
symptoms	O
of	O
abnormal	O
,	O
excessive	O
or	O
hypersynchronous	B-Algorithm
neuronal	I-Algorithm
activity	I-Algorithm
in	O
the	O
brain	O
.	O
</s>
<s>
In	O
thalamocortical	O
dysrhythmia	O
(	O
TCD	O
)	O
,	O
normal	O
thalamocortical	O
resonance	B-Application
is	O
disrupted	O
.	O
</s>
<s>
The	O
thalamic	O
loss	O
of	O
input	O
allows	O
the	O
frequency	O
of	O
the	O
thalamo-cortical	O
column	O
to	O
slow	O
into	O
the	O
theta	B-Algorithm
or	O
delta	B-Algorithm
band	O
as	O
identified	O
by	O
MEG	B-Algorithm
and	O
EEG	B-Application
by	O
machine	O
learning	O
.	O
</s>
<s>
Neural	B-Algorithm
oscillations	I-Algorithm
are	O
sensitive	O
to	O
several	O
drugs	O
influencing	O
brain	B-Application
activity	I-Application
;	O
accordingly	O
,	O
biomarkers	O
based	O
on	O
neural	B-Algorithm
oscillations	I-Algorithm
are	O
emerging	O
as	O
secondary	O
endpoints	O
in	O
clinical	O
trials	O
and	O
in	O
quantifying	O
effects	O
in	O
pre-clinical	O
studies	O
.	O
</s>
<s>
These	O
biomarkers	O
are	O
often	O
named	O
"	O
EEG	B-Application
biomarkers	O
"	O
or	O
"	O
Neurophysiological	O
Biomarkers	O
"	O
and	O
are	O
quantified	O
using	O
quantitative	B-Algorithm
electroencephalography	I-Algorithm
(	O
qEEG	B-Algorithm
)	O
.	O
</s>
<s>
EEG	B-Application
biomarkers	O
can	O
be	O
extracted	O
from	O
the	O
EEG	B-Application
using	O
the	O
open-source	O
Neurophysiological	B-Algorithm
Biomarker	I-Algorithm
Toolbox	I-Algorithm
.	O
</s>
<s>
Neural	B-Algorithm
oscillation	I-Algorithm
has	O
been	O
applied	O
as	O
a	O
control	O
signal	O
in	O
various	O
brain	B-Application
–	I-Application
computer	I-Application
interfaces	I-Application
(	O
BCIs	O
)	O
.	O
</s>
<s>
Although	O
individual	O
neuron	O
activities	O
cannot	O
be	O
recorded	O
through	O
non-invasive	O
BCI	O
because	O
the	O
skull	O
damps	O
and	O
blurs	O
the	O
electromagnetic	O
signals	O
,	O
oscillatory	B-Algorithm
activity	I-Algorithm
can	O
still	O
be	O
reliably	O
detected	O
.	O
</s>
<s>
The	O
BCI	O
was	O
introduced	O
by	O
Vidal	O
in	O
1973	O
as	O
challenge	O
of	O
using	O
EEG	B-Application
signals	O
to	O
control	O
objects	O
outside	O
human	O
body	O
.	O
</s>
<s>
After	O
the	O
BCI	O
challenge	O
,	O
in	O
1988	O
,	O
alpha	O
rhythm	O
was	O
used	O
in	O
a	O
brain	B-Algorithm
rhythm	I-Algorithm
based	O
BCI	O
for	O
control	O
of	O
a	O
physical	O
object	O
,	O
a	O
robot	O
.	O
</s>
<s>
In	O
particular	O
,	O
some	O
forms	O
of	O
BCI	O
allow	O
users	O
to	O
control	O
a	O
device	O
by	O
measuring	O
the	O
amplitude	B-Application
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
in	O
specific	O
frequency	O
bands	O
,	O
including	O
mu	B-Algorithm
and	O
beta	B-Algorithm
rhythms	I-Algorithm
.	O
</s>
<s>
A	O
non-inclusive	O
list	O
of	O
types	O
of	O
oscillatory	B-Algorithm
activity	I-Algorithm
found	O
in	O
the	O
central	O
nervous	O
system	O
:	O
</s>
