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SUPERIOR OLIVE & LATERAL LEMNISCUS
Douglas OliverUniversity of Connecticut Health Center
CORTEX
MGB
IC
DCN
VCN
SOC
COCHLEA
Auditory Cortex
Auditory Pathways
DLL
VLL
DLL
VLL
GLUTGABAGLY
InferiorColliculus
Medial Geniculate Body
IC
Auditory Pathways
Organization of Superior Olivary Complex
Subdivisions and Cytoarchitecture Neuron types Inputs Outputs Synapses Basic Circuit
Tsuchitani, 1978, Fig. 10
MSO
LSO
MNTB
MSO
LSO
MNTB
(somata & dendrites) (axons & endings)
D
M
Cytoarchitecture of Superior Olivary Complex
Comparative anatomy of SOC
Tetsufumi Ito &Shig Kuwada
Brod
alFi
g 9-
8
MSO: medial superior olive; LSO: lateral superior oliveNTB: nucleus of trapezoid body; IC: inferior colliculus
Binaural Basic Circuits
Medial Superior Olive (MSO)
MSO Principle Cells
glutamate
Fusiform Bipolar Disc-shaped Each dendrite
innervated by a different side
MSO-In situ hybridization
VGLUT1 VGLUT2 VIAAT NISSL
MSO
MNTB
LSOSPO
RPO
LSO MSO
MNTB
G
BB
B
L
L
H
H
EI - ILD EE - ITD
MSO Inputs and Synapses
E=Excitation (glutamate) --- I=Inhibition (glycine)
H=high frequencyL=low frequency
LNTBTO LSO
Unlike retinal targets, the cochlear nuclei contain maps of frequency, not location.
T
T + ITD
So how does the auditory system know ‘where’ a sound is coming from?
By comparing the interaural time differences (ITD) between the ears
How is this accomplished?...
ITD CODING
A
B
C
D
E
abcd eOutputPlace Code
Left InputTime Code
Right InputTime Code
A
B
C
D
E
abcd eOutputPlace Code
Left InputTime Code
Right InputTime Code
MSO "peak" unit LSO "trough" unit
ExcitationInhibition
A C
D E
B
ITD ITD
LSO
E
E E
I
Figure 14.2
MSO
MSO creates a response to interaural time differences
Binaural Responses in MSO
MSO Summary Cytoarchitecture – Laminar stack Neuron types - glutamate Inputs – Spherical bushy AVCN Outputs – Inferior colliculus Synapses – Excitatory glutamate
Basic Circuit –Coincidence detector for ITD
Lateral Superior Olive(LSO)
Brod
alFi
g 9-
8
MSO: medial superior olive; LSO: lateral superior oliveNTB: nucleus of trapezoid body; IC: inferior colliculus
Binaural Basic Circuits
LSO-In situ hybridization
VGLUT1 VGLUT2 VIAAT NISSL
MSO
MNTB
LSOSPO
RPO
Calyx of Held
CalyxVGLUT1
LSO MSO
MNTB
G
BB
B
L
L
H
H
EI - ILD EE - ITD
LSO Inputs and Synapses
E=Excitation (glutamate) --- I=Inhibition (glycine)
H=high frequencyL=low frequency
A
B
C
D
E
abcd eOutputPlace Code
Left InputTime Code
Right InputTime Code
A
B
C
D
E
abcd eOutputPlace Code
Left InputTime Code
Right InputTime Code
MSO "peak" unit LSO "trough" unit
ExcitationInhibition
A C
D E
B
ITD ITD
MSO
E
E E
I
Figure 14.2
LSO
Binaural Responses in Superior Olive
LSO Summary Cytoarchitecture – S-shaped laminae Neuron types – glutamate or glycine Inputs – Spherical bushy AVCN ipsilateral MNTB principle cells driven by globular bushy cells
contralateral Outputs – Bilateral inferior colliculus Synapses – Excitatory glutamate from ipsilateral Inhibitory glycine from MNTB
Basic Circuit – Coincidence detector for ILD and ITD
Brod
alFi
g 9-
8
MSO: medial superior olive; LSO: lateral superior oliveNTB: nucleus of trapezoid body; IC: inferior colliculus
Output of SOC to IC
glutamate
glycine
Controversy in the mechanisms of ITD coding
• Mechanisms to code ITD are unclear• Delay lines• Inhibition• Other mechanisms
Beckius et al 1999
Too many best delays outside of physiological range
Peaks vs slopes
Summary of ITD coding
Jeffress model of delay lines consistent with avian MSO
Mammalian mechanisms in dispute Do peaks of activity indicate place in space or
is it the relative amount of activity on two sides (slopes)
Animals with larger heads might have peaks Inhibition plays a role and can shift peaks Role of plasticity? Ear movements?
Interaural Level Difference (ILD) Coding
ITDs work only for the low frequency components of sound
What about higher frequencies?
The sound shadow cast by the head produces interaural level differences
How is this comparison made?...
Louder Softer
ILD CODING
LSO MSO
MNTB
G
BB
B
L
L
H
H
EI - ILD EE - ITD
LSO Inputs and Synapses
E=Excitation (glutamate) --- I=Inhibition (glycine)
H=high frequencyL=low frequency
LSO Creates ILD Responses
Excitatory and inhibitory inputs to LSO When sound is louder in ipsilateral ear, LSO
neurons fire action potentials When sound is louder in the contralateral ear,
LSO neurons are inhibited ILD may overshadow ITD in the LSO
Brod
alFi
g 9-
8
MSO: medial superior olive; LSO: lateral superior oliveNTB: nucleus of trapezoid body; IC: inferior colliculus
Output of SOC to IC
glutamate
glycine
Periolivary nuclei
Sources of inhibitory inputs Ascending Descending
Periolivary-In situ hybridization
VGLUT1 VGLUT2 VIAAT NISSL
MSO
MNTB
LSOSPO
RPO
Periolivary Nuclei
CONTRLATERALVCN
IPSILATERALVCN
VMPO
VLPO
SPO
DPO
Basic Circuit of SPON
Other Inputs: Descending System
Periolivary Nuclei Summary
Neurons use GABA, glycine, or acetylcholine Inputs from cochlear nucleus, one side only Monaural Output to IC: SPON Cochlear nucleus: VNTB & VLPO Cochlea -medial OCB: VMPO & other Cochlea -lateral OCB: VLPO & other
Lateral Lemniscus
Sources of inhibitory inputs to inferior colliculus (IC)
Dorsal nucleus of the Lateral Lemniscus GABA inputs to IC
Ventral nucleus of the Lateral Lemniscus Mixed GABA and glycine inputs to IC
Intermediate nucleus of the lateral lemniscus Glutamatergic neurons
Cytoarchitecture and subdivisions
Neuron Types-DNLL
Cochleotopical organization
DNLL
Neuron Types-VCLL
VCLL
Batra and Fitzpatrick Hearing Res. 168 - 2002
Perc
enta
ge o
f GAB
A-ir
neur
ons t
hat
inne
rvat
e th
e in
ferio
r col
licul
us in
the
rat
González-Hernández et al. (1996) Sources of GABAergic input to the inferior colliculus ofthe rat.J. Comp. Neurol. 372 : 309–326.
IC (c)DNLL (c)DNLL (i)INLL (i)VNLL (i)CLSO (c)LSO (i)MSO (i)SPON (i)OPO (i)AVCN (c)PVCN (c)DCN (c)
2.920.39.59.8480.60.60.32.93.40.80.50
234.44.09.147.50.60.40.24.44.01.01.00
CNICv CNICd
INLL + IVNLL = 57.8 % / 56.6%
NLL is the main source of inhibitory inputs to the IC
Neurotransmitters
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