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Vestibulospinal System
Vestibular Classics
March 02, 2007
Zakir Mridha
 The function of Vestibulospinal Syestem is to control of proper body posture
and movement.
 Specially, human upright vertical position is unstable.
 A continuous activation of postural muscles is therefore required to
avoid falling.
 The function of Vestibulospinal Syestem is to control of proper body posture
and movement.
 Specially, human upright vertical position is unstable.
 A continuous activation of postural muscles is therefore required to
avoid falling.
 The problem is complicated by the reduced dimension of the support
base (the feet) and by the articulated structure of the human skeleton.
 The function of Vestibulospinal Syestem is to control of proper body posture
and movement.
 Specially, human upright vertical position is unstable.
 A continuous activation of postural muscles is therefore required to
avoid falling.
 The problem is complicated by the reduced dimension of the support
base (the feet)and by the articulated structure of the human skeleton.
 But surprisingly, upright posture is a capability, which is learnt in the
first year of life.
Normal steady position of the head is maintained by powerful set of reflexes
that is known as vestibulocollic reflex
Peripheral sensory signals
(angular and/or linear accelerations)
detected by vestibular receptors
processed in the vestibular nuclei
LVST
MVST
relayed to the spinal cord
Modulates activity in muscles that rotate the head and upper torso and modulate
adjustments pertinent to limb and body orientation in the gravitational field.
 >20 pairs of muscles that control reflex movements of the head & neck.
 3 major groups: a) Neck Extensors
b) Neck Flexors
c) Neck Rotators
 Neck motoneurons are located
mainly in C1, C2 and C3 segments
 Pathways of axons in the spinal cord:
a) i-LVST
b) MVST and
c) c-LVST
 >20 pairs of muscles that control reflex movements of the head & neck.
 3 major groups: a) Neck Extensors
b) Neck Flexors
c) Neck Rotators
 Neck motoneurons are located
mainly in C1, C2 and C3 segments
 Pathways of axons in the spinal cord:
a) i-LVST
b) MVST and
c) c-LVST
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Location of the Vestibulo-spinal Neurons in Vestibular Nuclei
Type of HC nerve-activated Neurons
Axonal pathways
Projection level
Conduction velocity
Experimental Arrangements
Experimental Arrangements
Orthodromic:
Propagation of an impulse along
an axon in normal direction.
Antidromic:
Performing a nerve conduction
study in such a manner that the nerve
impulses is being propagated in a
direction opposite to that in which
the nerve fiber ordinarily conducts.
Experimental Arrangements
Orthodromic:
Propagation of an impulse along
an axon in normal direction.
Antidromic:
Performing a nerve conduction
study in such a manner that the nerve
impulses is being propagated in a
direction opposite to that in which
the nerve fiber ordinarily conducts.
Three types of Neurons:
VS neurons: Send axon to spinal
cord but not to the OMN.
VO neurons: Send axon to OMN
but not to the spinal cord.
VOS neurons: Send axon to both
Spinal cord and OMN.
Example of orthdromic and antidromic spikes
C1/2
C3
OMN
Axonal projection of the HC-activated
Vestibular neurons to the spinal cord were
examined using a collision test between
orthodromic andantidromic responses.
Antidromic response was confirmed by its
fixed latency at a stimulus intensuty
near the threshold, and by consistent
responses during high-frequency stimulation.
The antidromic spike evoked by spinal cord
stimulus were blocked by a preceding spike
evoked by HC stimulation when the timing
of the HC stimulation was close to that
of the spinal cord stimulation.
Projection levels in the spinal cord
Axonal Pathways of HC nerve-activated Vestibulospinal Neurons:
Locations of HC nerve activated vestibular neurons:
HC nerve-activated vestibulospinal neurons
Saccular nerve-activated vestibulospinal neurons
Sato et al. 1997
Axonal pathways & projection levels of SAC & UT-activated
vestibulospinal neurons
72%
12%
16%
30%
63%
7%
Sato et al. 1997
Projection of VS Neurons at different Levels of the Spinal Cord
80
70
70
60
50
40
30
20
-2
C1
Percentage (%
)
80
50
40
30
20
-2
C1
10
C3
60
T1
0
T1
i-LVST
L3
10
C3
0
MVST
i-LVST
MVST
L3
c-LVST
c-LVST
(Sato et al. 1997)
(Sato et al. 1996)
Posterior Canal
Anterior Canal
Horizontal Canal
Percentage (%
)
Sacculus
Utriculus
80
80
80
70
70
60
60
20
C
1- 2
10
C3
0
T1
i-LVST
L3
MVST
c-LVST
(Sugita et al. 2004)
40
30
20
C
1-2
10
C3
0
T1
i-LVST
L3
MVST
c-LVST
(Kitajima et al. 2006)
50
40
30
20
C1
-2
10
C3
0
T1
i-LVST
L3
MVST
c-LVST
(Kushiro et al. 2007??)
Percentage (%
)
30
50
Percentage (%
)
40
60
Percentage (%
)
50
70
 Neural connections and pathways underlying sacculocollic reflexes were studied by
intracellular recording from neck extensor and flexor motorneurons.
 Extensor muscle: Biventer Cervicis and Complexus Muscle– Motoneuron located at
C2 and C3 levels.
 Flexor Muscle: Longus Capitis Muscle– Motoneuron located at C2 levels
Methods:
a) Selective electrical stimulation of Saccular nerves.
b) Action potentials recorded from antidromically identified neck motoneurons
c) Pathways were determined by making transection of VST
Stimulus-response curves of N1 Potential
(Inset: Typical field
potential)
Synaptic Potential in Neck Motoneurons following Saccular Nerve stimulation
Excitatory Post Synaptic Potential (EPSP): is a temporary increase in postsynaptic membrane potential
caused by the flow of positively charged ions into the postsynaptic cell. They are the opposite of Inhibitory
Post Synaptic Potential (IPSP), which usually result from the flow of negative ions into the cell.
Latency of Synaptic Potential in Extensors and flexors motoneurons
Diagram of disynaptic and trisynaptic sacculo-collic motoneuron connections
Extensors
Flexors
Diagram of the Utriculo-neck motoneuron conections
Ikegami et al. 1994
Sternocleidomastoid muscle:
 origin, sternal head-manubrium, clavicular head-clavicle;
 insertion, mastoid process and superior nuchal line of occipital bone;
 innervation, accessory nerve and cervical plexus;
 action, flexes vertebral column, rotates
head.
Effect of Saccular nerve stimulation on ipsi- and contrlateral SCM motoneurons
Effect of Utricular nerve stimulation on ipsi- and contrlateral SCM motoneurons
Results from transecting experiments
Schematic diagram of the Sacculo- and Utriculo-sternocleidomastoid pathways
Longissimus Muscle Group: action, lateral flexion
1. Obliqus Capitis superior Muscle (OCS)
2. Splenius Muscle (SPL)
3. Longissimus Muscle (LONG)
Semispinalis Muscle Group: action, extends, rotates vertebral column
1. Biventer Cervicis Muscle (BIV)
2. Complexus Muscle (COMP)
Predominant Connections from Otolith & Canal to neck motoneurons
Muscles
Saccules
Utricules
HC
AC
PC
Ipsi
Contra
Ipsi
Contra
Ipsi
Contra
Ipsi
Contra
Ipsi
Contra
Extensors
EP
EP
EP
IP
IP
EP
EP
EP
IP
IP
Flexors
IP
IP
EP
IP
n.t
EP
IP
IP
n.t
EP
Rotators
IP
0
IP
EP
IP
EP
IP
EP
IP
EP
Red = LVST
Green = MVST
n.t. = Not Tested
O = No Effect
Muscles
Saccules
Utricules
HC
AC
PC
Ipsi
Contra
Ipsi
Contra
Ipsi
Contra
Ipsi
Contra
Ipsi
Contra
Extensors
EP
EP
EP
IP
IP
EP
EP
EP
IP
IP
Flexors
IP
IP
EP
IP
n.t
EP
IP
IP
n.t
EP
Rotators
IP
0
IP
EP
IP
EP
IP
EP
IP
EP
Projection of VS Neurons at different Levels of the Spinal Cord
80
70
60
50
40
30
20
-2
C1
)
80
70
50
40
30
20
-2
C1
10
C3
60
Percentage (%
Red = LVST
Green = MVST
Black = Unknown
n.t. = Not Tested
O = No Effect
0
T1
i-LVST
L3
10
C3
0
T1
MVST
i-LVST
MVST
L3
c-LVST
c-LVST
(Sato et al. 1997)
(Sato et al. 1996)
Posterior Canal
Anterior Canal
Horizontal Canal
Percentage (%
)
Sacculus
Utriculus
80
80
80
20
10
C3
0
T1
i-LVST
L3
MVST
c-LVST
(Sugita et al. 2004)
50
40
30
20
-2
C1
Percentage (%
)
30
Percentage (%
)
50
60
10
C3
0
T1
i-LVST
L3
MVST
c-LVST
(Kitajima et al. 2006)
50
40
30
20
-2
C1
10
C3
0
T1
i-LVST
L3
MVST
c-LVST
(Kushiro et al. 2007??)
)
70
60
Percentage (%
70
60
40
-2
C1
70