<s>
A	O
K-complex	B-Algorithm
is	O
a	O
waveform	O
that	O
may	O
be	O
seen	O
on	O
an	O
electroencephalogram	B-Application
(	O
EEG	B-Application
)	O
.	O
</s>
<s>
It	O
is	O
the	O
"	O
largest	O
event	O
in	O
healthy	O
human	O
EEG	B-Application
"	O
.	O
</s>
<s>
K-complexes	B-Algorithm
have	O
two	O
proposed	O
functions	O
:	O
first	O
,	O
suppressing	O
cortical	O
arousal	O
in	O
response	O
to	O
stimuli	O
that	O
the	O
sleeping	O
brain	O
evaluates	O
not	O
to	O
signal	O
danger	O
,	O
and	O
second	O
,	O
aiding	O
sleep-based	O
memory	O
consolidation	O
.	O
</s>
<s>
The	O
K-complex	B-Algorithm
was	O
discovered	O
in	O
1937	O
in	O
the	O
private	O
laboratories	O
of	O
Alfred	O
Lee	O
Loomis	O
.	O
</s>
<s>
K-complex	B-Algorithm
consists	O
of	O
a	O
brief	O
negative	O
high-voltage	O
peak	O
,	O
usually	O
greater	O
than	O
100	O
µV	O
,	O
followed	O
by	O
a	O
slower	O
positive	O
complex	O
around	O
350	O
and	O
550	O
ms	O
and	O
at	O
900	O
ms	O
a	O
final	O
negative	O
peak	O
.	O
</s>
<s>
K-complexes	B-Algorithm
occur	O
roughly	O
every	O
1.0	O
–	O
1.7	O
minutes	O
and	O
are	O
often	O
followed	O
by	O
bursts	O
of	O
sleep	B-Algorithm
spindles	I-Algorithm
.	O
</s>
<s>
Both	O
K-complex	B-Algorithm
and	O
delta	B-Algorithm
wave	I-Algorithm
activity	O
in	O
stage	O
2	O
sleep	O
create	O
slow-wave	O
(	O
0.8Hz	O
)	O
and	O
delta	O
(	O
1.6	O
–	O
4.0Hz	O
)	O
oscillations	O
.	O
</s>
<s>
However	O
,	O
their	O
topographical	O
distribution	O
is	O
different	O
,	O
and	O
the	O
delta	B-Algorithm
power	I-Algorithm
of	O
K-complexes	B-Algorithm
is	O
higher	O
.	O
</s>
<s>
This	O
is	O
accompanied	O
by	O
a	O
decrease	O
in	O
broadband	O
EEG	B-Application
power	O
including	O
gamma	B-Algorithm
wave	I-Algorithm
activity	O
.	O
</s>
<s>
The	O
activity	O
of	O
K-complexes	B-Algorithm
is	O
transferred	O
to	O
the	O
thalamus	O
where	O
it	O
synchronizes	O
the	O
thalamocortical	O
network	O
during	O
sleep	O
,	O
producing	O
sleep	O
oscillations	O
such	O
as	O
spindles	O
and	O
delta	B-Algorithm
waves	I-Algorithm
.	O
</s>
<s>
K-complexes	B-Algorithm
have	O
been	O
suggested	O
both	O
to	O
protect	O
sleep	O
and	O
also	O
to	O
engage	O
in	O
information	O
processing	O
,	O
as	O
they	O
are	O
both	O
an	O
essential	O
part	O
of	O
the	O
synchronization	B-Algorithm
of	O
NREM	O
sleep	O
,	O
while	O
they	O
also	O
respond	O
to	O
both	O
internal	O
and	O
external	O
stimuli	O
in	O
a	O
reactive	O
manner	O
.	O
</s>
<s>
Another	O
suggested	O
function	O
is	O
aiding	O
the	O
activation	O
homeostasis	O
of	O
synapses	B-Application
and	O
memory	O
consolidation	O
.	O
</s>
<s>
The	O
activation	O
thresholds	O
of	O
cortical	O
synapses	B-Application
become	O
lowered	O
during	O
wakefulness	O
as	O
they	O
process	O
information	O
,	O
making	O
them	O
more	O
responsive	O
,	O
and	O
so	O
need	O
to	O
be	O
adjusted	O
back	O
to	O
preserve	O
their	O
signal-to-noise	O
ratio	O
.	O
</s>
<s>
The	O
down-state	O
provided	O
by	O
K-complexes	B-Algorithm
does	O
this	O
by	O
reducing	O
the	O
strengths	O
of	O
synaptic	O
connections	O
that	O
occur	O
while	O
an	O
individual	O
is	O
awake	O
.	O
</s>
<s>
Another	O
change	O
occurs	O
in	O
adults	O
:	O
before	O
30	O
years	O
of	O
age	O
their	O
frequency	O
and	O
amplitude	B-Application
is	O
higher	O
than	O
in	O
older	O
people	O
particularly	O
those	O
over	O
50	O
years	O
of	O
age	O
.	O
</s>
<s>
This	O
parallels	O
the	O
decrease	O
in	O
other	O
components	O
of	O
sleep	O
such	O
as	O
sleep	B-Algorithm
spindle	I-Algorithm
density	O
and	O
delta	B-Algorithm
power	I-Algorithm
.	O
</s>
<s>
In	O
individuals	O
with	O
idiopathic	O
generalized	O
epilepsy	O
,	O
K-complex	B-Algorithm
induced	O
synchronization	B-Algorithm
can	O
trigger	O
spike-and-wave	B-Algorithm
discharges	O
.	O
</s>
<s>
In	O
autosomal	O
dominant	O
nocturnal	O
frontal	O
lobe	O
epilepsy	O
,	O
K-complexes	B-Algorithm
are	O
almost	O
invariably	O
present	O
at	O
the	O
start	O
of	O
seizures	O
.	O
</s>
<s>
Individuals	O
with	O
restless	O
legs	O
syndrome	O
have	O
increased	O
numbers	O
of	O
K-complexes	B-Algorithm
and	O
these	O
are	O
associated	O
with	O
(	O
and	O
often	O
precede	O
)	O
leg	O
movements	O
.	O
</s>
<s>
Dopamine	O
enhancing	O
drugs	O
such	O
as	O
L-DOPA	O
that	O
reduce	O
leg	O
movements	O
do	O
not	O
reduce	O
the	O
K-complex	B-Algorithm
suggesting	O
that	O
they	O
are	O
primary	O
and	O
the	O
leg	O
movements	O
secondary	O
to	O
them	O
.	O
</s>
<s>
Failure	O
of	O
such	O
drugs	O
to	O
reduce	O
K-complexes	B-Algorithm
in	O
spite	O
of	O
reducing	O
the	O
leg	O
movements	O
has	O
been	O
suggested	O
to	O
be	O
why	O
patients	O
after	O
such	O
treatment	O
still	O
continue	O
to	O
complain	O
of	O
non-restorative	O
sleep	O
.	O
</s>
<s>
This	O
inhibition	O
of	O
REM	O
sleep	O
significantly	O
decreases	O
K-complex	B-Algorithm
count	O
,	O
and	O
unlike	O
L-DOPA	O
treatment	O
,	O
clonazepam	O
studies	O
report	O
improvement	O
in	O
sleep	O
restoration	O
.	O
</s>
<s>
Therefore	O
,	O
drugs	O
that	O
inhibit	O
REM	O
sleep	O
also	O
decrease	O
K-complex	B-Algorithm
count	O
.	O
</s>
<s>
Obstructive	O
sleep	O
apnea	O
syndrome	O
is	O
associated	O
with	O
inspiratory	O
occlusions	O
evoking	O
fewer	O
K-complexes	B-Algorithm
during	O
NREM	O
sleep	O
even	O
though	O
K-complexes	B-Algorithm
are	O
evoked	O
normally	O
to	O
auditory	O
stimuli	O
and	O
such	O
individuals	O
react	O
normally	O
to	O
respiratory	O
interruptions	O
when	O
awake	O
.	O
</s>
