Lecture 12: olfaction: the insect antennal lobe

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Lecture 12 olfaction the insect antennal lobe
References H C Mulvad, thesis (http//www.nordita
.dk/mulvad/Thesis), Ch 2 G Laurent, Trends
Neurosci 19 489-496 (1996) M Bazhenov et al,
Neuron 30 553-567 and 569-581 (2001) Dayan
Abbott, Sect 7.5
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Olfaction (smell)

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Olfaction (smell)
The oldest sense (even bacteria do it)

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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar)
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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy
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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy Insects receptor cells
-gt antennal lobe -gt mushroom bodies

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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy Insects receptor cells
-gt antennal lobe -gt mushroom bodies Mammals
receptor cells -gt olfactory bulb -gt olfactory
cortex
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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy Insects receptor cells
-gt antennal lobe -gt mushroom bodies Mammals
receptor cells -gt olfactory bulb -gt olfactory
cortex 100000 receptor cells, several hundred
types (distinguished by receptor proteins)

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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy Insects receptor cells
-gt antennal lobe -gt mushroom bodies Mammals
receptor cells -gt olfactory bulb -gt olfactory
cortex 100000 receptor cells, several hundred
types (distinguished by receptor proteins) any
cell responsive to a range of odorants

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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy Insects receptor cells
-gt antennal lobe -gt mushroom bodies Mammals
receptor cells -gt olfactory bulb -gt olfactory
cortex 100000 receptor cells, several hundred
types (distinguished by receptor proteins) any
cell responsive to a range of odorants gt an
odor produces a characteristic pattern of
activity across the receptor cell population

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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy Insects receptor cells
-gt antennal lobe -gt mushroom bodies Mammals
receptor cells -gt olfactory bulb -gt olfactory
cortex 100000 receptor cells, several hundred
types (distinguished by receptor proteins) any
cell responsive to a range of odorants gt an
odor produces a characteristic pattern of
activity across the receptor cell
population Receptor physiology Receptor
proteins (1 kind/cell) metabotropic, G-protein
coupled, lead to opening of Na channels
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Olfaction (smell)
The oldest sense (even bacteria do it) Highly
conserved in evolution (mammals and insects
similar) Basic anatomy Insects receptor cells
-gt antennal lobe -gt mushroom bodies Mammals
receptor cells -gt olfactory bulb -gt olfactory
cortex 100000 receptor cells, several hundred
types (distinguished by receptor proteins) any
cell responsive to a range of odorants gt an
odor produces a characteristic pattern of
activity across the receptor cell
population Receptor physiology Receptor
proteins (1 kind/cell) metabotropic, G-protein
coupled, lead to opening of Na channels, similar
to phototransduction in retina
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Antennal lobe
1000-10000 neurons in locust 1130 830
excitatory, 300 inhibitory in honeybee 800
excitatory, 4000 inhibitory
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Antennal lobe
1000-10000 neurons in locust 1130 830
excitatory, 300 inhibitory in honeybee 800
excitatory, 4000 inhibitory Organized into
glomeruli (bunches of synapes) (1000 in
locust, 160 in bee)
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Antennal lobe
1000-10000 neurons in locust 1130 830
excitatory, 300 inhibitory in honeybee 800
excitatory, 4000 inhibitory Organized into
glomeruli (bunches of synapes) (1000 in
locust, 160 in bee)
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Antennal lobe
1000-10000 neurons in locust 1130 830
excitatory, 300 inhibitory in honeybee 800
excitatory, 4000 inhibitory Organized into
glomeruli (bunches of synapes) (1000 in
locust, 160 in bee)
Connections between AL neurons dendrodentritic
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Excitatory cells (PN)
PN projection neuron axon takes its spikes out
of the antennal lobe, to the mushroom bodies (
other higher areas)
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Excitatory cells (PN)
PN projection neuron axon takes its spikes out
of the antennal lobe, to the mushroom bodies (
other higher areas) transmitter ACh
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Excitatory cells (PN)
PN projection neuron axon takes its spikes out
of the antennal lobe, to the mushroom bodies (
other higher areas) transmitter ACh
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Excitatory cells (PN)
PN projection neuron axon takes its spikes out
of the antennal lobe, to the mushroom bodies (
other higher areas) transmitter ACh
Dendrites have postsynaptic terminals in 1 or
more glomeruli (10-20 in locust)
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Inhibitory cells (LN)
LN local neuron projects only within the
antennal lobe
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Inhibitory cells (LN)
LN local neuron projects only within the
antennal lobe no Na spikes, only Ca spikelets
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Inhibitory cells (LN)
LN local neuron projects only within the
antennal lobe no Na spikes, only Ca
spikelets transmitter GABA
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Inhibitory cells (LN)
LN local neuron projects only within the
antennal lobe no Na spikes, only Ca
spikelets transmitter GABA
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Inhibitory cells (LN)
LN local neuron projects only within the
antennal lobe no Na spikes, only Ca
spikelets transmitter GABA
Dendrites with postsynaptic terminals in several
or all glomeruli
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Antennal lobe responsestemporally modulated
oscillatory activity patterns
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Antennal lobe responsestemporally modulated
oscillatory activity patterns
20 hz oscillations
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Antennal lobe responsestemporally modulated
oscillatory activity patterns
20 hz oscillations
(No oscillations in input from receptor cells)
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Oscillations and transient synchronization
membrane potentials
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Oscillations and transient synchronization
membrane potentials
Local field potential In mushroom body Measures
average AL activity
(cell in mushroom body)
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Oscillations and transient synchronization
membrane potentials
Local field potential In mushroom body Measures
average AL activity
(cell in mushroom body)
PN firing transiently synchronized to LFP
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Model (Bazhenov et al)

• 90 PNs, 30 LNs

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Model (Bazhenov et al)

• 90 PNs, 30 LNs
• Single-compartment, conductance-based neurons

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Model (Bazhenov et al)

• 90 PNs, 30 LNs
• Single-compartment, conductance-based neurons
• (post)synaptic kinetics

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Model (Bazhenov et al)

• 90 PNs, 30 LNs
• Single-compartment, conductance-based neurons
• (post)synaptic kinetics
• Fast excitation, fast and slow inhibition

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Model (Bazhenov et al)

• 90 PNs, 30 LNs
• Single-compartment, conductance-based neurons
• (post)synaptic kinetics
• Fast excitation, fast and slow inhibition
• 50 connectivity, random

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Model (Bazhenov et al)

• 90 PNs, 30 LNs
• Single-compartment, conductance-based neurons
• (post)synaptic kinetics
• Fast excitation, fast and slow inhibition
• 50 connectivity, random
• Stimuli 1-s current pulse inputs to
  randomly-chosen 33 of neurons

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Bazhenov network
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Excitatory neurons
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Excitatory neurons
Active currents

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Excitatory neurons
Active currents Na

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Excitatory neurons
Active currents Na
K
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Excitatory neurons
Active currents Na
K A-current
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Excitatory neurons
Active currents Na
K A-current
Synaptic input
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Excitatory neurons
Active currents Na
K A-current
Synaptic input
Fast (ionotropic) synaptic currents (nACh and
GABAA)
( O is open fraction)
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Excitatory neurons
Active currents Na
K A-current
Synaptic input
Fast (ionotropic) synaptic currents (nACh and
GABAA)
( O is open fraction)
T is transmitter concentration
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Excitatory neurons
Active currents Na
K A-current
Synaptic input
Fast (ionotropic) synaptic currents (nACh and
GABAA)
( O is open fraction)
exc inh
T is transmitter concentration
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Slow inhibition
Kinetics like GABAB
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Slow inhibition
Kinetics like GABAB
G-protein concentration
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Slow inhibition
Kinetics like GABAB
G-protein concentration
Activated receptor concentration
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Slow inhibition
Kinetics like GABAB
G-protein concentration
Activated receptor concentration
Fast and slow Components
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Inhibitory neurons
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Inhibitory neurons
Active currents

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Inhibitory neurons
Active currents Ca

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Inhibitory neurons
Active currents Ca

( -gt Ca spikes)
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Inhibitory neurons
Active currents Ca
K
( -gt Ca spikes)
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Inhibitory neurons
Active currents Ca
K
Ca-dependent K current
( -gt Ca spikes)
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Inhibitory neurons
Active currents Ca
K
Ca-dependent K current
( -gt spike rate adaptation)
( -gt Ca spikes)
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Inhibitory neurons
Active currents Ca
K
Ca-dependent K current
( -gt spike rate adaptation)
( -gt Ca spikes)
Dynamics of nK(Ca)
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Inhibitory neurons
Active currents Ca
K
Ca-dependent K current
( -gt spike rate adaptation)
( -gt Ca spikes)
Dynamics of nK(Ca)
Ca dynamics
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2 neurons (1 PN, 1LN)
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6 PNs 2 LNs
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6 PNs 2 LNs
(fast) inhibition between LNs
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6 PNs 2 LNs
(fast) inhibition between LNs
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6 PNs 2 LNs
(fast) inhibition between LNs
LNs take turns
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Full network (9030)
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Responses of 4 PNs to 1 stimulus
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Responses of 4 PNs to 1 stimulus
Reliable (trial-to-trial reproducible) firing
timing when there is large Inhibitory input
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Another stimulus
Input to same set of PNs but different LNs
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Another stimulus
Input to same set of PNs but different LNs
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Another stimulus
Input to same set of PNs but different LNs
Same overall firing rate pattern, but different
temporal fine structure
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3rd stimulus
Input to 90-different set of neurons
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3rd stimulus
Input to 90-different set of neurons
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3rd stimulus
Input to 90-different set of neurons
Different firing pattern across neurons (but same
network-average rate)
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Blocking LN-LN inhibition
LNs now spike regularly
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Blocking LN-LN inhibition
LNs now spike regularly
Less difference between responses to stimuli 1
and 2
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Reducing IK(Ca)
(reducing LN spike-rate adaptation)
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Reducing IK(Ca)
(reducing LN spike-rate adaptation)
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Reducing IK(Ca)
(reducing LN spike-rate adaptation)
Less precise timing, weaker temporal modulation,
reduced discriminability
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Role of slow LN-PN inhibition
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Role of slow LN-PN inhibition

• Slow rate modulations
• abolished

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Role of slow LN-PN inhibition

• Slow rate modulations
• abolished
• reduced
• discriminability