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. Olfaction (smell).

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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, Neuron30 553-567 and 569-581 (2001)

Dayan & Abbott, Sect 7.5


Olfaction (smell)


Olfaction (smell)

The oldest sense (even bacteria do it)


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:

Insects:receptor cells -> antennal lobe -> mushroom bodies


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:

Insects:receptor cells -> antennal lobe -> mushroom bodies

Mammals: receptor cells -> olfactory bulb -> olfactory cortex


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:

Insects:receptor cells -> antennal lobe -> mushroom bodies

Mammals: receptor cells -> olfactory bulb -> olfactory cortex

~100000 receptor cells, several hundred types

(distinguished by receptor proteins)


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:

Insects:receptor cells -> antennal lobe -> mushroom bodies

Mammals: receptor cells -> olfactory bulb -> olfactory cortex

~100000 receptor cells, several hundred types

(distinguished by receptor proteins)

any cell responsive to a range of odorants:


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:

Insects:receptor cells -> antennal lobe -> mushroom bodies

Mammals: receptor cells -> olfactory bulb -> olfactory cortex

~100000 receptor cells, several hundred types

(distinguished by receptor proteins)

any cell responsive to a range of odorants:

=> an odor produces a characteristic pattern of activity

across the receptor cell population


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:

Insects:receptor cells -> antennal lobe -> mushroom bodies

Mammals: receptor cells -> olfactory bulb -> olfactory cortex

~100000 receptor cells, several hundred types

(distinguished by receptor proteins)

any cell responsive to a range of odorants:

=> 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


Olfaction (smell)

The oldest sense (even bacteria do it)

Highly conserved in evolution (mammals and insects similar)

Basic anatomy:

Insects:receptor cells -> antennal lobe -> mushroom bodies

Mammals: receptor cells -> olfactory bulb -> olfactory cortex

~100000 receptor cells, several hundred types

(distinguished by receptor proteins)

any cell responsive to a range of odorants:

=> 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


Antennal lobe

~1000-10000 neurons

in locust: 1130: 830 excitatory, 300 inhibitory

in honeybee: 800 excitatory, 4000 inhibitory


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)


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)


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


Excitatory cells (PN)

PN = projection neuron: axon takes its spikes out of the antennal

lobe, to the mushroom bodies (+ other higher areas)


Excitatory cells (PN)

PN = projection neuron: axon takes its spikes out of the antennal

lobe, to the mushroom bodies (+ other higher areas)

transmitter: ACh


Excitatory cells (PN)

PN = projection neuron: axon takes its spikes out of the antennal

lobe, to the mushroom bodies (+ other higher areas)

transmitter: ACh


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)


Inhibitory cells (LN)

LN = local neuron: projects only within the antennal lobe


Inhibitory cells (LN)

LN = local neuron: projects only within the antennal lobe

no Na spikes, only Ca “spikelets”


Inhibitory cells (LN)

LN = local neuron: projects only within the antennal lobe

no Na spikes, only Ca “spikelets”

transmitter: GABA


Inhibitory cells (LN)

LN = local neuron: projects only within the antennal lobe

no Na spikes, only Ca “spikelets”

transmitter: GABA


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


Antennal lobe responses:temporally modulated oscillatory activity patterns


Antennal lobe responses:temporally modulated oscillatory activity patterns

~20 hz oscillations:


Antennal lobe responses:temporally modulated oscillatory activity patterns

~20 hz oscillations:

(No oscillations in input from receptor cells)


Oscillations and transient synchronization

membrane potentials


Oscillations and transient synchronization

membrane potentials

Local field potential

In mushroom body:

Measures average

AL activity

(cell in mushroom body)


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


Model (Bazhenov et al)

  • 90 PNs, 30 LNs


Model (Bazhenov et al)

  • 90 PNs, 30 LNs

  • Single-compartment, conductance-based neurons


Model (Bazhenov et al)

  • 90 PNs, 30 LNs

  • Single-compartment, conductance-based neurons

  • (post)synaptic kinetics


Model (Bazhenov et al)

  • 90 PNs, 30 LNs

  • Single-compartment, conductance-based neurons

  • (post)synaptic kinetics

  • Fast excitation, fast and slow inhibition


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


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


Bazhenov network


Excitatory neurons


Excitatory neurons

Active currents:


Excitatory neurons

Active currents:

Na


Excitatory neurons

Active currents:

Na K


Excitatory neurons

Active currents:

Na K A-current


Excitatory neurons

Active currents:

Na K A-current

Synaptic input


Excitatory neurons

Active currents:

Na K A-current

Synaptic input

Fast (ionotropic) synaptic currents (nACh and GABAA):

( [O] is open fraction)


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:


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:


Slow inhibition

Kinetics like GABAB


Slow inhibition

Kinetics like GABAB

G-protein concentration:


Slow inhibition

Kinetics like GABAB

G-protein concentration:

Activated receptor concentration


Slow inhibition

Kinetics like GABAB

G-protein concentration:

Activated receptor concentration

Fast and slow

Components:


Inhibitory neurons


Inhibitory neurons

Active currents:


Inhibitory neurons

Active currents:

Ca


Inhibitory neurons

Active currents:

Ca

( -> Ca spikes)


Inhibitory neurons

Active currents:

Ca K

( -> Ca spikes)


Inhibitory neurons

Active currents:

Ca K Ca-dependent K current

( -> Ca spikes)


Inhibitory neurons

Active currents:

Ca K Ca-dependent K current

( -> Ca spikes)

( -> spike rate adaptation)


Inhibitory neurons

Active currents:

Ca K Ca-dependent K current

( -> Ca spikes)

( -> spike rate adaptation)

Dynamics of nK(Ca):


Inhibitory neurons

Active currents:

Ca K Ca-dependent K current

( -> Ca spikes)

( -> spike rate adaptation)

Dynamics of nK(Ca):

Ca dynamics:


2 neurons (1 PN, 1LN)


6 PNs + 2 LNs


6 PNs + 2 LNs

(fast) inhibition

between LNs


6 PNs + 2 LNs

(fast) inhibition

between LNs


6 PNs + 2 LNs

(fast) inhibition

between LNs

LNs take turns:


Full network (90+30)


Responses of 4 PNs to 1 stimulus


Responses of 4 PNs to 1 stimulus

Reliable (trial-to-trial reproducible) firing timing when there is large

Inhibitory input


Another stimulus:

Input to same set of PNs but different LNs


Another stimulus:

Input to same set of PNs but different LNs


Another stimulus:

Input to same set of PNs but different LNs

Same overall firing rate pattern, but different temporal fine structure


3rd stimulus:

Input to 90%-different set of neurons:


3rd stimulus:

Input to 90%-different set of neurons:


3rd stimulus:

Input to 90%-different set of neurons:

Different firing pattern across neurons (but same network-average rate)


Blocking LN-LN inhibition

LNs now spike ~ regularly


Blocking LN-LN inhibition

LNs now spike ~ regularly

Less difference between responses to stimuli 1 and 2


Reducing IK(Ca)

(reducing LN spike-rate adaptation)


Reducing IK(Ca)

(reducing LN spike-rate adaptation)


Reducing IK(Ca)

(reducing LN spike-rate adaptation)

Less precise timing, weaker temporal modulation, reduced discriminability


Role of slow LN-PN inhibition


Role of slow LN-PN inhibition

Slow rate modulations

abolished


Role of slow LN-PN inhibition

  • Slow rate modulations

  • abolished

  • reduced

    discriminability


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