This presentation discusses in detail the transients that occur mainly in late stage 1 and stage 2 of sleep, and may be confused to be pathological. The prototype here are theK complexes and the Sleep Spindles.

1. Electroencephalogram,
Spindles and K complexes

2. Sleep
• The default state
• Active Process
• Requires synchronizers
• Sleep Spindles, K Complexes

3. Raphe promotes sleep
Locus coeruleus
promotes
wakefulness
*so sleep control
is distributed
across centers

4. The reticular formation also
promotes wakefulness

5. Stages of sleep form cyclical pattern
Slow-Wave Activity:
-- Spindles:
7 - 15 Hz ; Wax and
Wane
-- Delta:
1 - 4 Hz
-- Slow Osc. .5 - 1 Hz

6. Sleep Spindles
• Compared to alpha rhythm !!
• One of the earliest described events
• Hallmark of Synchronization
• Requires an oscillator

7. Midpontine pre- trigeminal
Cerebellum
Encephale isole‘
Klimesch VO: BioIII
Normal sleep-wake cycle including REM
Cerveau isole‘
SWS
Thalamus
Sleep-wake cycle without REM
pproximate location of the three cuts for the human brain are
below.
7

8. THALAMUS

9. Gyri orbitales
Gyri frontales
Co
rp
u
G. praecentralis
G. postcentralis
RE
Gyri
temporales
VA
VL
VP LP
Pu
LGN
MGN
Gyri
parietales
A
M
ss
tri
atu
m

10. Thalamocortical
Network
Ctx
+
+
RE
+
TC
-

11. Thalamocortical spindle circuitry
Modified from Steriade and Llinás. Physiol.Rev. 68:649-742, 1998.

12. T type calcium channel genes in
thalamus
α1G
α1H
α1I
Courtesy of E Talley, D Bayliss & E
Perez-Reyes

13. Post inhibitory rebound in thalamic
relay neurons
-60
Vm
-70
-80
Ca2+depende
nt
rebound
burst
IPSP
threshold
1
hT
0
T channels reprimed
100 ms

14. Thalamo-cortical reentrant loops.
Steriade, M. (1999). Coherent oscillations and
short-term plasticity in corticothalamic networks. TINS, Vol. 22 (8), 337-344.
Basic Circuitry:
Cortex
RE
Cortex
Dorsal Thal. = Relay Nuclei
RE
L-circ
Th-cx
Dendro-dendr.
Th-cx
RE
L-circ
Aff
‚Secondary neurons‘

15. 1,2
Afferent brainstem input to Th-cx (1),
Activation of RE and Cortex (2)
Cortex
L-circ
RE
Th-cx
Dendro-dendr.
Th-cx
RE
L-circ
Aff

16. 3 Excitatory processes in Cortex;
Inhibition of primary L-circ;
Inhibition of other RE cells
Cortex
L-circ
RE
Th-cx
Dendro-dendr.
Th-cx
RE
L-circ
Aff

17. 4
Excitatory feedback response from cortex.
Disinhibition of primary L-circ neurons.
Inhibition of secondary Th-cx neurons.
The resulting effect is that during time 4, Th-cx are again under inhibitory control from L-circ neurons and, at the same time are activated
from cortico-thalamic cells. Thus, only strong (converging and/or amplified) cortical feedback will trigger another excitatory activation
wave into the cortex in time 5.
Cortex
The strong
inhibition of the
secondary Th-cx
cell may lead to low
threshold spikes
(LTS) and, thus, to
a 10 Hz oscillation.
L-circ
RE
Th-cx
Th-cx
RE
L-circ
Aff

18. 5 The primary Th-cx cell may start a new excitatory burst into the cortex. At this stage
(because released from the L-circ inhibition), a new afferent input will have a strong effect.
The secondary Th-cx cells remain under inhibition
RESULT: Center-surround ‚on-off‘ effect with a resulting strong focal activation of
cortical target neurons.
Cortex
RE
L-circ
Th-cx
Th-cx
RE
L-circ
Aff

19. Summary of findings:
Afferent brainstem activation is missing and cortical activation is strong:
- Th-cx cells are hyperpolarized and oscillate with spindle frequency Note that a depol.
current pulse during maximal hyperpol. leads to high frequency bursts. The result is
increased oscillatory cortical activation leading to Delta activity.
- The effect of increased cortical activation is even larger if stimulation patterns are
oscillatory
SLEEP: Spindles and Delta
RE
Cortex
Th-cx hyperpolarized,
Sleep spindles
L-circ
Th-cx
Missing brainstem afferents

20. Spindle oscillations in thalamus
A M P A /N M D A R
T h a la m u s
G A B A AR
nR t
T C
+
timing
R ebound
B u rs t
E P S P &
B u rs t
IP S P
20 m V
C o rte x
-
200 m s

21. RE Cell Rapidly bursting type
A Mathematical model
Foundations II - Neuroimaging

23. TC Cell modulation by RE cell
A Mathematical model

26. Propagation of Spindles

27. Ontogeny of Spindles
• EEG maturation
• Posterior Dominant
• Anterior spread
• Amplitude decreases with age
• Two ditinct frequency bands seen

28. K Complexes
Paroxysmal Events

29. K Complexes
• stage 2 sleep, arousing stimuli.
• Loomis et al. (1938);
• reason for calling them K complexes
remains obscure
• spur of the moment
• Knocking
• K complex shows a maximum over the
vertex,
• also K complexes with an indubitable
maximum over the frontal midline.

30. • H. Davis et al. - central and frontal K
complexes
• Brazier (1949) presumed two distinct
generators; these were area 6,
corresponding with the vertex, and area 9,
corresponding with frontal midline.
• initial sharp component, followed by a slow
component that fuses with a superimposed
fast component.
• The sharp component is biphasic and not
seldom multiphasic.
• The slow component is represented by a
large slow wave that may exceed 1,000
msec in duration

32. Positive occipital sharp transients of sleep
POSTS start to occur in healthy people at age 4 years, become fairly common
by age 15 years, remain common through age 35 years, and start to disappear
by age 50 years.
POSTS are seen very commonly on EEG and have been said to be more
common during daytime naps than during nocturnal sleep.
Most characteristics of POSTS are contained in their name. They have a
positive maximum at the occiput, are contoured sharply, and occur in early
sleep (stages I and II). Their morphology classically is described as "reverse
check mark," and their amplitude is 50-100 µV. They typically occur in runs of
4-5 Hz and are bisynchronous, although they may be asymmetric. They persist
in stage II sleep but usually disappear in subsequent stag

33. Vertex sharp transients
Also called vertex waves or V waves, these transients are almost
universal. Although they often are grouped together with K complexes,
strictly speaking, vertex sharp transients are distinct from K
complexes. Like K complexes, vertex waves are maximum at the
vertex (central midline placement of electrodes [Cz]), so that,
depending on the montage, they may be seen on both sides, usually
symmetrically. Their amplitude is 50-150 µV. They can be contoured
sharply and occur in repetitive runs, especially in children. They persist
in stage II sleep but usually disappear in subsequent stages. Unlike K
complexes, vertex waves are narrower and more focal and by
themselves do not define stage II.